welding manual r01 nov 2006

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BHARAT HEAVY ELECTRICALS LIMITED POWER SECTOR - CORPORATE QUALITY

2

INDEX

Sl.No. Description Page No.

01 Cover Sheet 01 02 Index 02 03 Preface 03 04 Foreword 04 05 Approval Sheet 05 06 Important Note 06 07 Status of Amendments 07 08 Table of Contents (Part A & B ) 08

3

PREFACE

Construction activities at field are dominated by welding processes for assembly

and building critical products like boiler, boiler auxiliaries, electrostatic precipitator

and piping. Various welding processes are adopted at the field based on the product

requirements and reliability of the welds.

This document has been prepared to provide basic guidelines to all construction

personnel in ensuring effective process management of welding and allied

activities. The various aspects of process control covering the stages of planning &

preparation for welding, controls during welding and post welding requirements are

brought out in the form of specifications, norms and procedures/instructions in this

document. This manual has been updated to reflect the newer materials and

processes developed by BHEL.

The requirements specified in this document are based on the relevant codes/

specifications like IBR, ASME and AWS and also consolidates the experience of

BHEL good welding practices based on more than three decades of manufacturing

and erection. The document also provides DO s and DON’T s for the benefit of

users, which would help in better process control and prevention of defects.

I am sure that this Manual would enable the construction activities in a big way to

manage their welding processes effectively to produce defect free quality.

A.V. Krishnan

General Manager (Corporate Quality)

4

F O R E W O R D

The present revision of Welding Manual has been made with the contributions

from a team of BHEL Engineers having long experience in the areas of Construction

Management, Welding and Quality of manufacturing units and Power Sector.

In this revision, the comments / suggestions offered by Power Sector / Regions,

HPBP BHEL Trichy, Piping Centre, HPEP Hyderabad & HEEP Haridwar and the

minimum requirements of reference codes have been taken care.

This manual deals with, apart from Welding requirements for BHEL HPBP Trichy

complex,HEEP Haridwar & HPEP Hyderabad packages also. Welding requirements for

the new material P91 / T91 are dealt in detail for the benefit of site engineers.

It is felt that this revision manual will be more useful and practical for

implementation as an aid for assurance of quality of welding at the sites.

Any further feedback or suggestion is welcome to improve upon the the present

volume in due course.

Place : Chennai (D.Indran) Date : 09.11.2006 Executive Director

Power Sector - Southern Region

5

W E L D I N G M A N U A L F O R

POWER SECTOR

BHARAT HEAVY ELECTRICALS LIMITED POWER SECTOR / CORPORATE QUALITY

NAME DESIGNATION / DIVISION V.KANDHSAMY AGM/ PSSR –QLY, Chennai UM DESHPANDE AGM/ CQ, SECUNDRABAD Dr. K.P.DHANDAPANI DGM / WTC-TIRUCHY P.ELANGOVAN DGM / PC- Chennai A.SUKUMARAN Manager/ SAS Cell - TIRUCHY D.DEVASAHAYAM Manager/ PSSR-QLY, Chennai

PREPARED BY

R.JANARTHANAN Dy. Manager/ PC-Chennai

APPROVED BY

A.V.KRISHNAN

GENERAL MANAGER / CQ, NEW DELHI

DOCUMENT NO.

PSQ-WDM-COM R01 / 11 – 06

ISSUE DATE

COPY NO. ID No. :

DATE OF ISSUE

CONTROLLED COPY / INFORMATION COPY

ISSUED BY

ISSUED TO :

6

I M P O R T A N T

THIS WELDING MANUAL PROVIDES BROAD BASED GUIDELINES

FOR WELDING WORK AT SITES. HOWEVER, SITES MUST

ENSURE ADHERENCE TO THE PRIMARY DOCUMENTS LIKE

CONTRACT DRAWINGS, ERECTION WELDING SCHEDULE, PLANT

/ CORPORATE STANDARDS, WHEREVER SUPPLIED, STATUTORY

DOCUMENTS, WELDING PROCEDURE SPECIFICATIONS,

CONTRACTUAL OBLIGATIONS, IF ANY AND SPECIAL

INSTRUCTIONS ISSUED BY MANUFACTURING UNITS SPECIFIC

TO THE PROJECT.

WELDING MANUAL A1. WELDING-GENERAL 7

STATUS OF AMENDMENTS

Sl.No. Reference of Sheet(s) Amended

Amendment No. & Date Remarks


A1. WELDING-GENERAL

1.0 SCOPE:

This manual deals with activities and information related to welding for site

operations including P91 material. Where specific documents are supplied

by the manufacturers, the same shall be adopted.

2. DOCUMENTS REFERRED:

2.1 The following documents are referred in preparation of this manual.

1. AWS D1.1

2. ASME sections I, II (A&C), V & IX

3. ASME B31.1

4. IBR

5. BHEL Manufacturing Units’ Standards & practices

3. PROCEDURE:

3.1 The following documents shall be referred as primary documents

- Contract drawings

- Erection Welding Schedule or equivalent

- Plant / Corporate standards, where supplied

- Statutory documents

- Welding Procedure Specifications

- Contractual obligations, if any.

3.2 Welder Qualification:

3.2.1 Ensure, personnel qualified as per statutory requirements are engaged, where required.

3.2.2 For welding not under the purview of statutory requirements, qualification of welders shall be as in this manual.

3.3 Monitor performance of qualified butt welders as in this manual.

3.4 Ensure selection, procurement, storage, drying & issue of welding consumables, as detailed in this manual.

3.4.1 List of approved vendors of general purpose welding electrodes as provided by BHEL, Tiruchy Unit web site (www.bheltry.co.in) shall be used for selection of brands at sites . Alternatively specific contractual requirements, if any may be followed.


3.4.1.1 Where Tiruchy list does not cover site requirements, such specific cases may be referred to Head(Qly) of the region.

3.5 Welding in-charge shall assign a unique identification for all the butt welds coming under the purview of statutory regulations. Such identification may be traceable through documents like drawings, sketches etc.

3.5.1 A welding “job card” incorporating the welding parameters and heat treatment requirements is recommended to be issued for all critical welds like pressure part welds, piping welds, ceiling girder welds. A format of the job card is enclosed for illustration.

3.6 Heat Treatment:

3.6.1 Preheat, inter pass, post heat and Post Weld Heat Treatment (PWHT) requirements shall be as per applicable documents; where these are not supplied, reference may be made to this manual.

3.6.2 Prior to PWHT operation, a “job card” containing material specification, weld reference, size, rate of heating, soaking temperature, soaking time and rate of cooling shall be prepared referring to applicable documents, and issued.

3.6.3 On completion of PWHT, temperature recorder details (like Sl.No., make, range, chart speed) chart number, date of PWHT, start and end time of operation shall be entered on the job card. The PWHT chart shall contain the chart number.

3.6.4 The chart shall be evaluated and results recorded. Refer Heat Treatment Manual (Document No. PSQ-HTM-COM) for details.

3.7 Equipment & Instruments:

3.7.1 Equipment/accessories used shall be assessed for fitness prior to use.

3.7.2 Use calibrated temperature recorders.

3.7.3 Thermal chalks shall be batch tested prior to use. 3.8 Inspection:

3.8.1 Inspection of welding may be done as per Chapter A5 and records maintained as appropriate.


3.8.2 Weld log containing the following information shall be prepared for all completed systems.

- Project / Unit reference

- Drawing No.

- Weld designation

- EWS/equivalent

- Material specification

- Welder code

- Date of welding

- NDE ref. and results (including repair details)

- PWHT ref. and results

- Remarks, if any.

3.9 Safety:

3.9.1 Safe access to weld area shall be provided.

3.9.2 Adequate protection shall be provided against excessive wind and rain water entry during welding.

3.10 Records :

3.10.1 All records, as required, shall be maintained by welding in-charge.


WELDING JOB CARD Page 2 of 2

FILLER WIRE / ELECTRODE CONSUMPTION GTAW Filler wire : SMAW φ 2.5 mm : φ 3.15 mm : φ 4.0 mm : Date of LPI for RG Plug : Remarks : Date of Return :

WELDING JOB CARD Page 1 of 2 Project :

Unit No. : Area: Boiler / TG / PCP

Job Card No. : Date:

Joint No. :

Drawing No. :

System Description :

Size (Dia. x thick) :

Material Specification :

Welder No.(s) :

Date of welding :

Filler wire Specification :

Electrode Specification :

Preheat temperature :

Inter pass temperature :

PWHT temperature :

Welding Engineer


JOB CARD (WELDING, HEAT TREATMENT & ND EXAMINATION)

FOR P91 WELDS

Card No.: Date: Project UNIT NO. Contractor: System: Drawing No.

PGMA: DU No.: Joint No.:

Material Specification: + OD (mm): WT(mm)

Filler metal: GTAW SMAW

Joint fit-up: Min. WT: Root gap: Root

mismatch: Log sheet filled:

Y / N

No. of T/Cs: Location: Distance from EP edge: mm

Welders’ ID: M/c No.:

Preheat Temp.: °C Minimum Rate of heating: °C per hour

Purging flow rate: Litres / min. Purging time: Minutes Shielding flow rate: Litres / min. for GTAW Distance bet. dams: Metres

Interpass Temp.: ° C Maximum Rate of cooling: °C per hour

Holding Temp.: ° C for min. 1 hour. for post heating

PWHT: ° C Rate of heating / cooling: °C per hour

Soaking time Minutes (2.5 minutes per mm) Cooling to: 350° C

Preheating started at Hrs. on Preheating completed at Hrs.

Root welding started at Hrs. Root welding completed at Hrs.

Welding started at Hrs. Welding completed at Hrs.

Interpass temp. maintained between °C and °C

Holding temp. reached at Hrs. Holding completed at Hrs.

No. of T/Cs: Location:

PWHT started at Hrs. on . Soaking started at Hrs. .

Soaking completed at Hrs. 350°C reached at Hrs.

UT Equipment used: Calibration validity:

UT carried out on Result : OK / Not OK

MPI Equipment used: Calibration validity:

MPI carried out on Result: OK / Not OK

Hardness test Equipment used: Calibration validity:

Hardness test carried out on Value:

History of interruption if any, with time:

Contractor BHEL Customer


JOB CARD (WELDING, HEAT TREATMENT & ND EXAMINATION)

FOR T91 WELDS Card No.: Date:

Project UNIT NO. Contractor: System: Drawing No.

PGMA: DU No.: Joint No.:

Material Specification: + OD (mm): WT(mm)

Filler metal: GTAW SMAW

Joint fit-up: Min. WT: Root gap: Root

mismatch: Log sheet filled:

Y / N

No. of T/Cs: Location: Distance from EP edge: mm

Welders’ ID: M/c No.:

Preheat Temp.: °C Minimum Rate of heating: °C per hour

Purging flow rate: Litres / min. Purging time: Minutes Shielding flow rate: Litres / min. for GTAW Distance bet. dams: Metres

Interpass Temp.: ° C Maximum Rate of cooling: °C per hour

Holding Temp.: ° C for min. 1 hour. for post heating

PWHT: ° C Rate of heating / cooling: °C per hour

Soaking time Minutes (2.5 minutes per mm) Cooling to: 350° C

Preheating started at Hrs. on Preheating completed at Hrs.

Root welding started at Hrs. Root welding completed at Hrs.

Welding started at Hrs. Welding completed at Hrs.

Interpass temp. maintained between °C and °C

Holding temp. reached at Hrs. Holding completed at Hrs.

No. of T/Cs: Location:

PWHT started at Hrs. on . Soaking started at Hrs. .

Soaking completed at Hrs. 350°C reached at Hrs.

UT Equipment used: Calibration validity:

UT carried out on Result : OK / Not OK

MPI Equipment used: Calibration validity:

MPI carried out on Result: OK / Not OK

Hardness test Equipment used: Calibration validity:

Hardness test carried out on Value:

History of interruption if any, with time:

Contractor BHEL Customer

WELDING MANUAL A2 BASE MATERIALS 16

CHAPTER – A2

BASE MATERIALS


A2. BASE MATERIALS 1.0 SCOPE:

1.1 This chapter contains tabulations of chemical compositions and mechanical properties of various materials generally used in BHEL sites.

2.0 CONTENTS:

CHEMICAL COMPOSITION AND MECHANICAL PROPERTIES

Table 1 - Pipes (ASME)

Table 2 - Tubes (ASME)

Table 3 - Forgings (ASME)

Table 4 - Castings (ASME)

Table 5 - Plates / Sheets (ASME)

Table 6 - Pipes (Other specifications)

Table 7 - Tubes (Other specifications)

3.0 The data are for general information purposes. The corresponding P numbers are also indicated.

4.0 For materials not covered in this chapter, the supplier shall be contacted.


Table-1 Pipes

Chemical Composition (%) Mechanical Properties (Min.) Sl. No.

P.No. / Group

No.

Material Specification C Mn P S Si Ni Cr Mo V T.S

Kg / mm2 Y.S

Kg / mm2 % E Min.

1 P 1 / 1

SA 106 Gr. B (Remarks:

Carbon restricted to 0.25% Max.)

0.30 Max.

0.29-1.06

0.035 Max.

0.035 Max.

0.10 Max.

0.40 Max.

0.40 Max.

0.15 Max. - 42 25 30

2 P 1 / 2

SA 106 Gr. C

(Remarks: Carbon restricted to 0.25% Max.)

0.35 Max.

0.29- 1.06

0.035 Max.

0.035 Max.

0.10 Max.

0.40 Max. 0.40 0.15

Max. - 49 28 30

3 P 4 / 1 SA 335 P 12 0.15 Max.

0.30- 0.61

0.025 Max.

0.025 Max.

0.50 Max. - 0.80-

1.25 0.44- 0.65 - 42 21 30

4 P 5A / 1 SA 335 P 22 0.15 Max.

0.30- 0.60

0.025 Max.

0.025 Max.

0.50 Max. - 1.90-

2.60 0.87- 1.13 - 42 21 30

5 P 5B / 2 SA 335 P91 0.08- 0.12

0.30- 0.60

0.02 Max.

0.01 Max.

0.20- 0.50

0.40 Max.

8.00- 9.50

0.85- 1.05 0.18-0.25 60 42 20


Table-2 Tubes CHEMICAL COMPOSITION AND MECHANICAL PROPERTIES


P.No. / Group No.

Material Specification (ASME) C Mn P S Si Ni Cr Mo V

T.S Kg / mm2

Y.S Kg / mm2

% E Min.

1 P 1 / 1 SA 192 0.06-0.18 0.27-0.63 0.035

Max. 0.035 Max.

0.25 Max. - - - 33 18 35

2 P 1 / 1

SA 210 Gr A1

(Remarks: Carbon restricted to 0.25%

Max.)

0.27 Max.

0.93 Max.

0.035 Max.

0.035 Max.

0.10 Max. - - -

42 26 30

3 P 1 / 1 SA 179 0.06-0.18 0.27-0.63 0.035

Max. 0.035 Max. - - - - 33 18 35

4 P 1 / 2

SA 210 Gr C

(Remarks: Carbon restricted to 0.30%

Max.)

0.35 Max.

0.29- 1.06

0.035 Max.

0.035 Max.

0.10 Max. - - -

49 28 30

5 P 3 / 1 SA 209 T1 0.10- 0.20

0.30- 0.80

0.025 Max.

0.025 Max.

0.10- 0.50 - - 0.44-0.65 39 21 30

6 P 4 / 1 SA 213 T11 0.15 Max. 0.30-0.60 0.025

Max. 0.025 Max. 0.50-1.00 - 1.00-

1.50 0.44-0.65 42 21 30

7 P 4 / 1 SA 213 T12 0.15 Max. 0.30-0.61 0.025

Max. 0.025 Max. 0.50 Max. - 0.80-

1.25 0.44- 0.65 42 22 30

8 P 5 A / 1 SA 213 T22 0.15 Max. 0.30-0.60 0.025

Max. 0.025 Max.

0.50 Max. - 1.90-

2.60 0.87- 1.13

42 21 30

9 P 5 B / 1 SA 213 T5 0.15 Max. 0.30-0.60 0.025

Max. 0.025 Max.

0.50 Max. - 4.00-

6.00 0.45- 0.65

42 21 30

10 P 5 B / 1 SA 213 T9 0.15 Max. 0.30-0.60 0.025

Max. 0.025 Max. 0.25-1.00 - 8.00-

10.00 0.90- 1.10 - 42 21 30

11 P 5 B / 2 SA 213 T91 0.08- 0.12

0.30- 0.60

0.02 Max.

0.01 Max.

0.20- 0.50

0.40 Max.

8.00- 9.50

0.85- 1.05

0.18-0.25

60 42 20

12 P 8 / 1 SA 213 TP 304 H 0.04- 0.10

2.00 Max.

0.04 Max.

0.03 Max.

0.75 Max.

8.00- 11.00

18.00-

20.00 - - 53 21 35

13 P 8 / 1 SA 213 TP 347 H (Cb + Ta Stabilised)

0.04- 0.10

2.00 Max.

0.04 Max.

0.03 Max.

0.75 Max.

9.00- 13.00

17.00-

20.00 - - 53 21 35


CHEMICAL COMPOSITION AND MECHANICAL PROPERTIES Table-3 Forgings


P.No. / Group No.


Kg / mm2 Y.S

Kg / mm2 % E Min.

1 P 1 / 2

SA 105 (Remarks:

Carbon restricted to

0.25% Max.)

0.35 Max.

0.60- 1.05

0.04 Max.

0.05 Max.

0.35 Max.

0.40 Max.

0.30 Max.

0.12 Max. - 49 25 30

2 P 4 / 1 SA 182 F11 Class 3

0.10- 0.20

0.30- 0.80

0.04 Max.

0.04 Max.

0.50- 1.00 - 1.00-

1.50 0.44-0.65 - 49 28 20

3 P 4 / 1 SA 182 F 12 Class 2 0.10-0.20 0.30-0.80 0.04

Max. 0.04 Max. 0.10-0.60 - 0.80-1.25 0.44-0.65 - 49 28 20

4 P 5 A / 1 SA 182 F 22 Class 3

0.15 Max. 0.30-0.60 0.04

Max. 0.04 Max.

0.50 Max. - 2.00-2.50 0.87-1.13 - 53 32 20

5 P 5 B / 2 SA 182 F91 0.08-0.12 0.30-0.60 0.02 Max.

0.01 Max. 0.20-0.50 0.40

Max. 8.00-9.50 0.85-1.05 0.18-0.25 60 42 20



Table-4 Castings


P.No. / Group No.

Material Specification (ASME) C Mn P S Si Ni Cr Mo T.S

Kg / mm2 Y.S

Kg / mm2 % E Min.

1 P 1 / 2

SA 216 WCB (Remarks: Carbon restricted to 0.25%

Max.)

0.30 Max. 1.00 Max. 0.04 Max. 0.045 Max. 0.60 Max. 0.50 Max. 0.50 Max. 0.20 Max. 49 25 22

2 P 1 / 2 SA 216 WCC 0.25 Max. 1.20 Max. 0.04 Max. 0.045 Max. 0.60 Max. 0.50 Max. 0.50 Max. 0.20 Max. 49 28 22

3 P 4 / 1 SA 217 WC6 0.20 Max. 0.50-0.80 0.04 Max. 0.045 Max. 0.60 Max. - 1.00-1.50 0.45-0.65 49 28 20

4 P 5 A / 1 SA 217 WC 9 0.18 Max. 0.40-0.70 0.04 Max. 0.045 Max. 0.60 Max. - 2.00-2.75 0.90-1.20 49 28 20

5 P 8 / 1 SA 351 CF 8 0.08 Max. 1.50 Max. 0.04 Max. 0.04 Max. 2.00 Max. 8.00-11.00

18.00- 21.00 0.50 Max. 49 21 35

6 P 8 / 1 SA 351 CF 8M 0.08 Max. 1.50 Max. 0.04 Max. 0.04 Max. 1.50 Max. 9.00-12.00

18.00-21.00 2.00- 3.00 49 21 30

7 P 8 / 1 SA 351 CF 8C 0.08 Max. 1.50 Max. 0.04 Max. 0.04 Max. 2.00 Max. 9.00-12.00

18.00-21.00 0.50 Max. 49 21 30

8 P 8 / 2 SA 351 CH 20 0.04-0.20 1.50 Max. 0.04 Max. 0.04 Max. 2.00 Max. 12.00-15.00

22.00-26.00 0.50 Max. 49 21 30


CHEMICAL COMPOSITION AND MECHANICAL PROPERTIES Table-5 Plates / Sheets

Chemical Composition (%) Mechanical Properties (Min.) Sl.

No. P.No. /

Group No. Material

Specification C Mn P S Si Ni Cr Mo V T.S Kg / mm2

Y.S Kg / mm2

% E Min.

1 P 1 / 1 SA 36 0.25-0.29 0.80-1.20 0.40 0.05 0.40 Max. - - - - - - -

2 P 1 / 1 SA 516 Gr 60 0.21-0.25 0.55-1.30 0.035 Max.

0.035 Max. 0.13-0.45 - - - - 53 21 23

3 P 1 / 2 SA 516 Gr 70 0.31 Max. 0.79-1.30 0.035

Max. 0.035 Max. 0.13-0.45 - - - - 49 27 21

4 P 1 / 2 SA 299 0.30 Max. 0.84-1.62 0.035

Max. 0.04 Max. 0.13-0.45 - - - - 53 29 19

5 P 1 / 2 SA 515 Gr 70 0.35 Max.

1.30 Max.

0.035 Max.

0.035 Max. 0.13-0.45 - - - - 49 27 21

6 P 4 / 1 SA 387 Gr 12 Class 2

0.17 Max. 0.35-0.73 0.035

Max. 0.035 Max. 0.13-0.45 - 0.74-1.21 0.40-0.65 - 46 28 22

7 P 5 A / 1 SA 387 Gr 22 Class 2

0.15 Max. 0.25-0.66 0.035

Max. 0.035 Max.

0.50 Max. - 1.88-2.62 0.85-1.15 - 52 32 18

8 P 5 B / 2 SA 387 Gr 91 0.06-0.15 0.25-0.66 0.025 Max.

0.012 Max. 0.18-0.56 0.43

Max. 7.90-9.60 0.80-1.10 0.18-0.25 60 42 18

9 P 8 / 1 SA 240 TYPE 304

0.08 Max.

2.00 Max.

0.045 Max.

0.03 Max.

0.75 Max.

8.00-10.50

18.00-20.00 - - 53 21 40

10 IS 2062 Gr.A 0.23 Max.

1.50 Max.

0.050 Max.

0.050 Max. - - - - - 42 25 23

11 IS 2062 Gr.B 0.22 Max.

1.50 Max.

0.045 Max.

0.045 Max.

0.40 Max. - - - - 42 25 23

12 IS 2062 Gr.C 0.20 Max.

1.50 Max.

0.040 Max.

0.040 Max.

0.40 Max. - - - - 42 25 23

13 IS 8500-540 0.20 Max.

1.60 Max.

0.045 Max.

0.045 Max.

0.45 Max. - - - - 55 40 20


CHEMICAL COMPOSITION AND MECHANICAL PROPERTIES Table-6 Pipes (Other Specifications)

Chemical Composition (%) Mechanical Properties (Min.) Sl.

No.

P.No. / Group

No.


Kg / mm2 Y.S

Kg / mm2 % E Min.

1 P 1 / 1 DIN St. 35.8 0.17 Max.

0.40- 0.80

0.04 Max.

0.04 Max. 0.10-0.35 - - - - 36.70-

48.96 24 25

2 P 1 / 1 DIN St. 45.8 0.21 Max. 0.45-1.20 0.04

Max. 0.04 Max. 0.10-0.35 - - - - 41.80-

54.10 26 21

3 P 1 / 1 BS 3602 / 410 0.21 Max. 0.40-1.20 0.045

Max. 0.045 Max.

0.35 Max. - - - - 41.82-

56.10 25 22

4 P 1 / 1 BS 3602 / 460 0.22 Max. 0.80-1.40 0.045

Max. 0.045 Max.

0.35 Max. - - - - 46.90-

61.20 28.60 21

0.10-0.15 0.40 Max.

0.04 Max.

0.04 Max. 0.10-0.35 - 0.70-1.10 0.45-0.65 - 46.90-

62.22 18.36 22 5 P 4 / 1

BS 3604 620-460 HFS

or CDS 620-440 0.10-0.18 0.40-0.70 0.04

Max. 0.04 Max.

0.10- 0.35 - 0.70-1.10 0.45-

0.65 - 44.90- 60.20 29.58 22

6 P 5 / 1 BS 3604

622 HFS or CDS

0.08- 0.15

0.40- 0.70

0.04 Max.

0.04 Max.

0.50 Max.

-

2.00 2.50

0.90- 1.20

- 48.80 26.80 17

7 -

BS 3604 HFS 660

Or CDS 660

0.15 Max.

0.40- 0.70

0.04 Max.

0.04 Max. 0.10-0.35 - 0.25-0.50 0.50-0.70 0.22-0.30 47.30 30 17

8 P5B / 2 X20CrMoV121 DIN17175 0.17-0.23 ≤ 1.00

0.030 Max.

0.030 Max. ≥ 0.50 0.30-0.80 10.00-

12.50 0.80-1.20 0.25-0.35 70-86 50 17



Table-7 Tubes (Other Specifications) Chemical Composition (%) Mechanical Properties (Min.) Sl.

No.

P.No. / Group

No.


Kg / mm2 T.S

Kg / mm2 % E Min.

1 P 1 / 1 DIN St. 35.8 0.17 Max.

0.40- 0.80

0.04 Max.

0.04 Max. 0.10-0.35 - - - - 36.70-

48.96 24 25

2 P 1 / 1 DIN St. 45.8 0.21 Max. 0.40-1.20 0.04

Max. 0.04 Max. 0.10-0.35 - - - - 41.80-

54.06 26 21

3 P 1 / 1 BS 3059 / 360 0.17 Max.

0.40- 0.80

0.045 Max.

0.045 Max.

0.35 Max. - - - - 36.70-

51.00 22 24

4 P 1 / 1 BS 3059 / 440 0.12-0.18 0.90-1.20 0.040 Max.

0.035 Max. 0.10-0.35 - - - - 44.88-

59.20 25 21

5 P 3 / 1 15 Mo3 DIN17175 0.12-0.20 0.40-

0.80 0.035 Max.

0.035 Max. 0.10-0.35 - - 0.25-0.35 - 45.90-

61.20 27.50 22

6 P 4 / 1 13 Cr Mo 44 DIN17175

0.10- 0.18

0.40- 0.70

0.035 Max.

0.035 Max. 0.10-0.35 - 0.70-1.10 0.45-

0.65 - 44.88-60.18 29.60 22

7 P 4 / 1 BS 3059 / 620 0.10-0.15 0.40- 0.70

0.040 Max.

0.040 Max. 0.10-0.35 - 0.70-1.10 0.45-

0.65 - 46.90-62.20 18.40 22

8 P 5 / 1 10 Cr Mo 910 DIN17175 0.08-0.15 0.40-0.70 0.035

Max. 0.035 Max.

0.50 Max. - 2.00-2.50 0.90-1.20 - 45.90-

61.20 28.60 20

9 P 5 / 1 BS 3059 (622) - 440 0.08-0.15 0.40-0.70 0.04

Max. 0.04 Max.

0.50 Max. - 2.00-2.50 0.90-1.20 - 44.90-

60.18 17.85 20

10 P 5 / 1 BS 3059 (622) - 490 0.08-0.15 0.40-0.70 0.040

Max. 0.040 Max.

0.50 Max. - 2.00-2.50 0.90-1.20 - 49.98-

65.00 28.05 20

11 - 14 Mo V 63 DIN17175 0.10-0.18 0.40-0.70 0.035

Max. 0.035 Max. 0.10-0.35 0.30-0.60 0.50-0.70 0.22-0.32 46.90-

62.22 32.60 20

12 P5B / 2 X20CrMoV121 DIN17175 0.17-0.23 ≤ 1.00

0.030 Max.

0.030 Max. ≥ 0.50 0.30-0.80 10.00-

12.50 0.80-1.20 0.25-0.35 70-86 50 17

WELDING MANUAL A3 WELDING MATERIAL SPECIFICATION AND CONTROL

25

CHAPTER - A3

WELDING MATERIAL SPECIFICATION AND CONTROL


26

A3. WELDING MATERIAL SPECIFICATION AND CONTROL

1.0 SCOPE:

This chapter gives details for welding material specification and control at sites.

2.0 CONTENTS:

1. Table-1 - Weld Metal Chemical Composition.

2. Table-2 - Mechanical property requirement for all-weld metal.

3. Receipt inspection of welding electrodes/filler wires.

4. Storage and identification of welding electrodes/filler wires.

5. Drying and holding of welding electrodes.

6. Selection and issue of welding electrodes/filler wires.

7. Table-3 - Selection of GTAW filler wire, SMAW electrodes for butt welds in tubes, pipes, headers.

8. Table-4 - Selection of electrodes for welding attachments to tubes.

9. Table-5 - Selection of electrodes, preheat, PWHT for attachment to attachment welds.

10. Table-6 - Selection of electrodes for welding nozzle attachments, hand hole plate, RG plug etc. to headers, pipes.

11. Table-7 – Selection of filler wire and electrodes for non-pressure parts ( including structures )

12. Table-8 - A numbers

13. Table-9 - F numbers

14. SFA Classification 3.0 For welding consumables not covered in this chapter, relevant details may be

obtained from the Manufacturing Units.


27

Table - 1 WELD METAL CHEMICAL COMPOSITION

Weight, % Electrode SFA No.

C Mn Si P S Ni Cr Mo V Cu Other Elements %

E 6010 5.1 Not Specified E 6013 5.1 Not Specified E 7018 / E 7018-1 5.1 Not

Specified 1.60 0.75 Not Specified 0.30 0.20 0.30 0.08 -

E 7018-A1 5.5 0.12 0.90 0.80 0.03 0.03 - - 0.40-0.65 - - E 8018-B2 5.5 0.05-0.12 0.90 0.80 0.03 0.03 - 1.00-1.50 0.40-0.65 - - E 8018-B2L 5.5 0.05 0.80 0.80 0.03 0.03 - 1.00-1.50 0.40-0.65 - - E 9018-B3 5.5 0.05-0.12 0.90 0.80 0.03 0.03 - 2.00-2.50 0.90-1.20 - - E 9018-B3L 5.5 0.05 0.90 0.80 0.03 0.03 - 2.00-2.50 0.90-1.20 - -

E 9018-B9 5.5 0.08-0.13 1.25 0.30 0.01 0.01 1.0 8.00-10.50 0.85-1.20 0.15-0.30 0.25

E 308 5.4 0.08 0.50-2.50 0.90 0.04 0.03 9.00-11.00

18.00-21.00 0.75 - 0.75

E 308-L 5.4 0.04 0.50-2.50 0.90 0.04 0.03 9.00-11.00

18.00-21.00 0.75 - 0.75

E 309 5.4 0.15 0.50-2.50 0.90 0.04 0.03 12.00-14.00

22.00-25.00 0.75 - 0.75

E 309-L 5.4 0.04 0.50-2.50 0.90 0.04 0.03 12.00-14.00

22.00-25.00 0.75 - 0.75

Combined Limit for

Mn+Ni+Cu+Mo+V=1.75

E 347 5.4 0.08 0.50-2.50 0.90 0.04 0.03 9.00-11.00

18.00-21.00 0.75 - 0.75 Cb+Ta 8XC Min. to 1.00

Max.

ENi-Cl 5.15 2.00 2.50 4.00 - 0.03 85 d min - - - 2.5e Fe Al others 8.0 1.0 Total 1.0

ENiFe-Cl 5.15 2.00 2.50 4.00 - 0.03 45d-60 - - - 2.5e Fe Al others Remf 1.0 Total 1.0


28

Table - 1(Contd…)

WELD METAL CHEMICAL COMPOSITION

Weight, % Electrode SFA No. C Mn Si P S Ni Cr Mo V Cu

Other Elements %

ER70S-2 5.18 0.07 0.90-1.40 0.40-0.70 0.025 0.035 a a a a 0.50b Ti Zr Al 0.05- 0.05- 0.05- 0.15 0.12 0.15

ER80S-G 5.28 Not Specified ER90S-G 5.28 Not Specified ER80S-B2 5.28 0.07-0.12 0.40-0.70 0.40-0.70 0.025 0.025 0.20 1.20-1.50 0.40-0.65 - 0.35c Total other Elements 0.50 ER90S-B3 5.28 0.07-0.12 0.40-0.70 0.40-0.70 0.025 0.025 0.20 2.30-2.70 0.90-1.20 - 0.35c Total other Elements 0.50 ER80S-D2 5.28 0.07-0.12 1.60-2.10 0.50-0.80 0.025 0.025 0.15 - 0.40-0.60 - 0.50c Total other Elements 0.50 ER90S-B9 5.28 0.07-0.13 1.25 0.15-0.30 0.01 0.01 1.00 8.00-9.50 0.80-1.10 0.15-0.25 0.20 Total other Elements 0.50

ER 308 5.9 0.08 1.00-2.50 0.30-0.65 0.03 0.03 9.00-11.00

19.50-22.00 0.75 - 0.75

ER 309 5.9 0.12 1.00-2.50 0.30-0.65 0.03 0.03 12.00-14.00

23.00-25.00 0.75 - 0.75

ER 309-L 5.9 0.03 1.00-2.50 0.30-0.65 0.03 0.03 12.00-14.00

23.00-25.00 0.75 - 0.75

ER 347 5.9 0.08 1.00-2.50 0.30-0.65 0.03 0.03 9.00-11.00

19.00-21.50 0.75 - 0.75 Cb+Ta 10XC Min.

to 1.0 Max.


29

TABLE - 1 (Contd…)

WELD METAL CHEMICAL COMPOSITION

a) These elements may be present but are not intentionally added.

b) The maximum weight percent of copper in the rod or electrode due to any coating

plus the residual copper content in the steel shall be 0.50.

c) The maximum weight percent of copper in the rod or electrode due to any coating

plus the residual copper content in the steel shall comply with the stated value.

d) Nickel plus incident Cobalt.

e) Copper plus incident Silver.

f) “Rem” stands for remainder.

g) Manufacturer’s certification to have met the requirements of ASME Sec. II

Part C is acceptable in cases where the chemical analysis are not reflected.

h) Single values are maximum.


30

Table-2

MECHANICAL PROPERTY REQUIREMENT

FOR ALL-WELD METAL

Electrode SFA No.

Tensile Strength

ksi

Yield Strength at 0.2% of

Proof Stress, ksi

Elongation In 2 inch (50.8 mm) %

E6010 5.1 60 48 22

E6013 5.1 60 48 17

E7018 5.1 70 58 22

E7018-1* 5.1 70 58 22

E7018-A1 5.5 70 57 25

E8018-B2 5.5 80 67 19

E8018-B2L 5.5 75 57 19

E9018-B3 5.5 90 77 17

E9018-B3L 5.5 90 77 17

E9018-B9 5.5 90 77 17

E308 5.4 80 - 35

E308L 5.4 75 - 35

E309 5.4 80 - 30

E309L 5.4 75 - 30

E347 5.4 75 - 30

ENi-CI 5.15 40-65 38-60 3-6

ENiFe-CI 5.15 58-84 43-63 6-18

ER70S-2 5.18 70 58 22

ER80S-B2 5.28 80 68 19

* - These electrodes shall meet the lower temperature impact requirements specified below:


31

Table-2 (Contd..)

MECHANICAL PROPERTY REQUIREMENT FOR ALL-WELD METAL

Electrode SFA No.

Tensile Strength

ksi

Yield Strength at 0.2% of

Proof Stress, ksi

Elongation In 2 inch (50.8 mm) %

ER90S-B3 5.28 90 78 17

ER80S-D2 5.28 80 68 17

ER90S-B9 5.28 90 60 16

ER308 5.9

ER308L 5.9

ER309 5.9

ER309L 5.9

ER347 5.9

These values are not required in the test certificate

NOTE:

a) Single values are minimum.

b) Manufacturer’s certification to have met the requirements of ASME-Section II Part C is acceptable in cases where the mechanical properties are not reflected.

c) 1ksi is approximately equal to 6.89 Mpa.


32

RECEIPT INSPECTION OF WELDING ELECTRODES / FILLER WIRES

1. All electrodes/filler wires received at site stores shall be segregated for type and size

of electrode.

2. Ensure that electrode packets received are free from physical damage.

3. Where electrodes are damaged, the same shall be removed from use.

4. Only electrodes identified in the “list of approved vendors of welding electrodes” are to be accepted.

5. Where filler metals are supplied by manufacturing unit, inspect for damages, if any.

6. Ensure availability of relevant test certificates. Refer tables of chemical compositions and mechanical properties for acceptance.

7. Endorse acceptance/rejection on the test certificate.


33

STORAGE & IDENTIFICATION OF WELDING ELECTRODES/FILLER WIRES

1.0 SCOPE:

1.1 This procedure is applicable for storage of welding electrodes/filler wires used at sites.

2.0 PROCEDURE:

2.1 Only materials accepted (based on receipt inspection) shall be taken into account for storage.

2.2 Storage Facility:

2.2.1 The storage facility shall be identified.

2.2.2 Access shall be restricted to authorised personnel.

2.2.3 The storage area shall be clean and dry.

2.2.4 Steel racks may be used for storage. Avoid storing wood inside the storage room.

2.2.5 Maintain the temperature of the storage facility above the ambient temperature. This can be achieved by the use of appropriate heating arrangements.

2.3 The electrodes/filler wire shall be segregated and identified for

a. Type of electrode e.g. E7018.

b. Size of electrode e.g. Dia 3.15 mm.

2.4 Colour coding for filler wires:

2.4.1 On receipt of GTAW filler wires, codify the filler wires as per table I below. Both ends shall be coloured.

Table-1

Specification Brand Name* Colour Code/Embossing

RT 1/2 Mo (ER80S-G) TGSM Green

RT 1 Cr 1/2 Mo (ER80S-G) TGS 1CM Silver gray / White

RT 2 1/4 Cr 1 Mo (ER90S-G) TGS 2CM Brown / Red

RT 9 Cr 1Mo 1/4 V(ER90S-B9) MTS-3 Embossing

RT 347 (ER347) TGS - 347 Blue (*or other approved equivalents)


34

2.4.2 Where another set of colour code is followed, maintain a record of coding used.

2.4.3 Where the filler wire is cut, apply the appropriate colour code at both ends of the piece.

2.4.4 For other filler wires, a suitable colour distinct from Table 1 shall be applied.

2.4.5 AWS No. or brand name embossed end to be retained for identification.


35

DRYING AND HOLDING OF WELDING ELECTRODES

1.0 SCOPE:

1.1 This section details activities regarding drying and holding of welding electrodes used at sites.

2.0 PROCEDURE:

2.1 While handling, avoid contact of oil, grease with electrodes. Do not use oily or wet gloves.

2.2 It is recommended that not more than two days’ requirements are dried.

3.0 GTAW Filler Wires:

3.1 These wires do not require any drying.

4.0 Covered Electrodes:

4.1.0 Drying and holding :

4.1.1 Identify drying oven and holding oven.

4.1.2 They shall preferably have a temperature control facility upto 350°C for drying oven and 200°C for holding oven.

4.1.3 A calibrated thermometer shall be provided for monitoring temperature.

4.2.0 On opening a packet of electrodes, segregate and place them in the drying oven. Avoid mix up.

4.2.1 After loading, raise the drying oven temperature to the desired range as per table in 4.2.5.

4.2.2 Note the time when the temperature reaches the desired range. Maintain this temperature for the duration required as per Table in 4.2.5.

4.2.3 On completion of drying, transfer the electrodes to holding oven; maintain a minimum temperature of 100°C till issue.

4.2.4 The electrode shall not be subjected to more than two cycles of drying.


36

4.2.5 Maintain a register containing following details:

Date Sl.No. Brand Name

Batch No.

Dia Qty. Baking Temp.

reach time

Time of transfer to

holding oven

Remarks

1

2

3

Drying and Holding Parameters

Baking (*) AWS

Classification Temperature °C Time (Hours)

Minimum Holding

Temperature °C (@)

E7018 250 - 300 2 100

E7018-1 250 - 300 2 100

E7018-A1 250 - 300 2 100

E8018-B2 250 - 300 2 100

E9018-B3 250 - 300 2 100

E8018-B2L 250 - 300 2 100

E9018-B3L 250 - 300 2 100

E9018-B9 250 - 300 2 100

E309 & E347 250 - 300 1 100

Note : (*) Guideline has been given however, supplier’s recommendations shall be followed. Note : (@) Maintain the temperature in the oven till issue.

4.2.6 After issue, maintain the electrodes in a portable oven at a minimum temperature of 65°C till use (not applicable for E6013, E309 & E347 electrodes)

4.3 Unused, returned electrodes shall be segregated and kept in the holding oven.


37

SELECTION AND ISSUE OF WELDING

ELECTRODES / FILLER WIRES

1.0 SCOPE:

1.1 This procedure details methods for selection and issue of welding electrodes/filler wires for site operations.

2.0 PROCEDURE:

2.1 Selection:

2.1.1 The type of filler wire/electrode for welding shall be based on the details given in the contract documents like Erection Welding Schedule, drawings, Welding Procedure Specifications as supplied by the manufacturing units.

2.1.2 Where not specified by the manufacturing units, selection shall be based on the tables enclosed.

2.1.3 Where electrodes/filler wire are not covered in the documents mentioned in 2.1.1., 2.1.2, refer to manufacturing units.

2.2 Issue :

2.2.1 Issue of welding electrodes/filler wires shall be based on authorised welding electrodes issue voucher.

2.2.2 It is recommended to restrict quantity issued to not more than 4 hours’ requirements.

2.2.3 Redried low hydrogen electrodes shall be carried to the work spot in a portable oven.

2.2.3.1 Maintain the temperature in the portable oven at the work spot above 65°C.

2.2.4 Unused electrodes shall be returned and kept in the holding oven till reissue.


38

Table-3

SELECTION OF GTAW FILLER WIRE, SMAW ELECTRODE FOR

BUTT WELDS IN TUBES, PIPES AND HEADERS

Material Welding Process

P1 Gr 1 P1 Gr 2

P3 Gr 1 P4 Gr 1 P5A Gr 1 P5B Gr 2 P8 Cr Mo V

P1 Gr 1 GTAW RT1/2 Mo

P1 Gr 2 SMAW E7018-1 Note 1

GTAW RT1/2 Mo RT1/2 Mo P3 Gr 1

SMAW E7018-1 E7018-A1

GTAW RT1/2 Mo RT1/2 Mo RT1Cr1/2 Mo P4 Gr 1

SMAW E7018-1 E7018-A1 E8018-B2

GTAW RT1/2 Mo RT1/2 Mo RT1Cr1/2 Mo RT21/4 Cr1Mo RT21/4 Cr1Mo P5A Gr 1

SMAW E7018-1 E7018-A1 E8018-B2 E9018-B3 E9018-B3

P5B Gr 2 GTAW ER90S-B9

GTAW RT21/4 Cr1Mo Note-3

P5B Gr 2

SMAW E9018-B9

GTAW ERNiCr3 ERNiCr3 RT347 P8

SMAW EniCrFe3 EniCrFe3 E347

GTAW RT21/4 Cr1Mo RT21/4 Cr1Mo CrMoV Note 2 SMAW E9018-B3 E9018-B3

Note-1 : E7018-A1 for P1 Gr2 + P1 Gr2 when PWHT is involved. Note-2 : DIN14MoV63 or equivalent Note-3: For t > 20 mm


39

Table-4

SELECTION OF ELECTRODES FOR WELDING ATTACHMENTS TO TUBES

Attachment Material Tube Material

P1 Group 1 P4 Group 1 P5A Group 1 P8

P1 Group 1 P1 Group 2 E 7018 E 7018 E 7018 E 7018-A1

P3 E 7018-A1 E 7018-A1 E 7018-A1 E 7018-A1

P4 Group 1 E 8018-B2 E 8018-B2 E 8018-B2 E 7018-A1

P5A Group 1 E 9018-B3 E 9018-B3 E 9018-B3 E 7018-A1

P8 E 309 E 309 E 347


40

Table-5

SELECTION OF ELECTRODES, PREHEAT, PWHT FOR ATTACHMENT TO ATTACHMENT WELDS

(Seal Bands, High Crown Bars, End Bars, End Bar Lifting Lugs and Collector Plates etc.)

Material Welding Requirements

P1 P4 P5 A P8 Group 1 P8 Group 2

P1 Electrode Preheat PWHT

E7018 Nil Nil


E7018 (Note 2) 120 (Note 4)

Nil (Note 2 & 3)

E8018-B2 120 (Note 4) Nil (Note 3)

P5 A Electrode Preheat PWHT

E7018 150°C (Note 4) Nil (Note 1 & 2)

E8018-B2 150°C (Note 4)

Nil (Note 1)

E9018-B3 150°C (Note 4)

Nil (Note 1)


E309 Nil Nil

E309 Nil Nil

E309 Nil Nil

E347 Nil Nil

E309 Nil Nil

Note – 1 : When P5 A material thickness is more than 10 mm, PWHT is required. Note – 2 : Electrode, preheat and PWHT requirement for welding end bar lifting lug are as follows:

End Bar Lifting Lug End Bar Electrode Preheat °C PWHT °C

P1 P4 E8018-B2 120 650 – 680

P1 P5 E9018-B3 150 680 – 720

Note – 3: When P4 material thickness is more than 13 mm PWHT required. Note – 4 : Preheat is not required for P4up to 16 mm & for P5 A up to 12 mm, if PWHT is carried out. Note - 5: For load carrying members, PWHT is required irrespective of thickness.


41

Table-6

SELECTION OF ELECTRODES FOR WELDING NOZZLE ATTACHMENTS, HAND HOLE PLATE, RG PLUG ETC. TO HEADERS, PIPES.

Attachment Material Header, Pipe

Material P1 P3 P4 P5 A P5 B/2 P8

P1 E7018-1 - E7018-1 - - ENiCrFe3

P4 - - E8018-B2 E8018-B2 - -

P5 A - - - E9018-B3 E9018-B3 ENiCrFe3

P5 B/2 - - - E9018-B3 E9018-B9 ENiCrFe3

CrMoV Note 1 - - - E9018-B3 - ENiCrFe3

Note 1 : DIN 14MoV63 or equivalent.


42

Table - 7

SELECTION OF ELECTRODES FOR NON-PRESSURE PARTS (INCLUDING STRUCTURES) (NOTE 1)

Material SMAW Electrodes SAW Wires

C O2 Wires

P1 + P1

For butt welds ≤ 6 mm: E 6013

> 6 mm: E 7018

For fillets ≤ 8 m : E 6013 >8 mm: E 7018

EL 8 EM 12 K EL 8 EM 12 K

Carton Steel + P1 E 6013 or E 7018

EM 12 K

Carton Steel + Carton Steel

E 8018 – B2 EB 2

E 81 T 1 – B2

Note 1 : E 6013 Electrodes can be used for all non-load carrying welds of all thickness of IS 2062 plates upto 20 mm thickness and 8 mm fillets.

E 71 T - 1


43

TABLE-8

A NUMBERS CLASSIFICATION OF FERROUS WELD METAL ANALYSIS FOR

PROCEDURE QUALIFICATION

Analysis, % (Note 1) A. No.

Types of Weld Deposit C Cr Mo Ni Mn Si

1 Mild steel 0.20 – – – 1.60 1.00

2 Carbon-Molybdenum 0.15 0.50 0.40-0.65 – 1.60 1.00

3 Chrome (0.4% to 2%)- Molybdenum 0.15 0.40-

2.00 0.40-0.65 – 1.60 1.00

4 Chrome (2% to 6%)- Molybdenum 0.15 2.00-

6.00 0.40-1.50 – 1.60 2.00

5 Chrome (6% to 10.5%)- Molybdenum 0.15 6.00-

10.50 0.40-1.50 – 1.20 2.00

6 Chrome-Martensitic 0.15 11.00-15.00 0.70 – 2.00 1.00

7 Chrome-Ferritic 0.15 11.00-30.00 1.00 – 1.00 3.00

8 Chromium-Nickel 0.15 14.50-30.00 4.00 7.50-

15.00 2.50 1.00

9 Chromium-Nickel 0.30 19.00-30.00 6.00 15.00-

37.00 2.50 1.00

10 Nickel to 4% 0.15 – 0.55 0.80-4.00 1.70 1.00

11 Manganese-Molybdenum 0.17 – 0.25-0.75 0.85 1.25-

2.25 1.00

12 Nickel-Chrome-Molybdenum 0.15 1.50 0.25-0.80

1.25-2.80

0.75-2.25 1.00

Note 1: Single values shown above are maximum.


44

TABLE-9

F NUMBERS GROUPING OF ELECTRODES AND WELDING RODS FOR QUALIFICATION

F.No. ASME Specification No. AWS Classification No.

Steel and Steel Alloys

1 SFA-5.1 EXX20

1 SFA-5.1 EXX22 1 SFA-5.1 EXX24 1 SFA-5.1 EXX27 1 SFA-5.1 EXX28 1 SFA-5.4 EXXX(X)-25 1 SFA-5.4 EXXX(X)-26 1 SFA-5.5 EXX20-X 1 SFA-5.5 EXX27-X

2 SFA-5.1 EXX12 2 SFA-5.1 EXX13 2 SFA-5.1 EXX14 2 SFA-5.1 EXX19 2 SFA-5.5 E(X)XX13-X

3 SFA-5.1 EXX10 3 SFA-5.1 EXX11 3 SFA-5.5 E(X)XX10-X 3 SFA-5.5 E(X)XX11-X

4 SFA-5.1 EXX15 4 SFA-5.1 EXX16 4 SFA-5.1 EXX18 4 SFA-5.1 EXX18M 4 SFA-5.1 EXX48 4 SFA-5.4 other than austenitic and duplex EXXX(X)-15 4 SFA-5.4 other than austenitic and duplex EXXX(X)-16 4 SFA-5.4 other than austenitic and duplex EXXX(X)-17 4 SFA-5.5 E(X)XX15-X 4 SFA-5.5 E(X)XX16-X 4 SFA-5.5 E(X)XX18-X 4 SFA-5.5 E(X)XX18M 4 SFA-5.5 E(X)XX18M1


45

TABLE-9 (CONTD.)



5 SFA-5.4 austenitic and duplex EXXX(X)-15 5 SFA-5.4 austenitic and duplex EXXX(X)-16 5 SFA-5.4 austenitic and duplex EXXX(X)-17

6 SFA-5.2 All classifications 6 SFA-5.9 All classifications 6 SFA-5.17 All classifications 6 SFA-5.18 All classifications 6 SFA-5.20 All classifications 6 SFA-5.22 All classifications 6 SFA-5.23 All classifications 6 SFA-5.25 All classifications 6 SFA-5.26 All classifications 6 SFA-5.28 All classifications 6 SFA-5.29 All classifications 6 SFA-5.30 INMs-X 6 SFA-5.30 IN5XX 6 SFA-5.30 IN3XX(X)

Aluminium and Aluminium-Base Alloys

21 SFA-5.3 E1100 21 SFA-5.3 E3003 21 SFA-5.10 ER1100 21 SFA-5.10 R1100 21 SFA-5.10 ER1188 21 SFA-5.10 R1188

22 SFA-5.10 ER5183 22 SFA-5.10 R5183 22 SFA-5.10 ER5356 22 SFA-5.10 R5356 22 SFA-5.10 ER5554 22 SFA-5.10 R5554 22 SFA-5.10 ER5556


46

TABLE-9 (CONTD.)

F NUMBERS

GROUPING OF ELECTRODES AND WELDING RODS FOR QUALIFICATION


22 SFA-5.10 R5556 22 SFA-5.10 ER5654 22 SFA-5.10 R5654

23 SFA-5.3 E4043 23 SFA-5.10 ER4009 23 SFA-5.10 R4009 23 SFA-5.10 ER4010 23 SFA-5.10 R4010 23 SFA-5.10 R4011 23 SFA-5.10 ER4043 23 SFA-5.10 R4043 23 SFA-5.10 ER4047 23 SFA-5.10 R4047 23 SFA-5.10 ER4145 23 SFA-5.10 R4145 23 SFA-5.10 ER4643 23 SFA-5.10 R4643

24 SFA-5.10 R206.0 24 SFA-5.10 R-C355.0 24 SFA-5.10 R-A356.0 24 SFA-5.10 R357.0 24 SFA-5.10 R-A357.0

25 SFA-5.10 ER2319 25 SFA-5.10 R2319

Copper And Copper Alloys

31 SFA-5.6 ECu 31 SFA-5.7 ERCu

32 SFA-5.6 ECuSi 32 SFA-5.7 ERCuSi-A


47

TABLE-9 (CONTD.)

F NUMBERS

GROUPING OF ELECTRODES AND WELDING RODS FOR QUALIFICATION

F.No. ASME Specification No. AWS Classification No. 33 SFA-5.6 ECuSn-A 33 SFA-5.6 ECuSn-C 33 SFA-5.7 ERCuSn-A

34 SFA-5.6 ECuNi 34 SFA-5.7 ERCuNi 34 SFA-5.30 IN67

35 SFA-5.8 RBCuZn-A 35 SFA-5.8 RBCuZn-B 35 SFA-5.8 RBCuZn-C 35 SFA-5.8 RBCuZn-D

36 SFA-5.6 ECuAl-A2 36 SFA-5.6 ECuAl-B 36 SFA-5.7 ERCuAl-A1 36 SFA-5.7 ERCuAl-A2 36 SFA-5.7 ERCuAl-A3

37 SFA-5.6 ECuNiAl 37 SFA-5.6 ECuMnNiAl 37 SFA-5.7 ERCuNiAl 37 SFA-5.7 ERCuMnNiAl

Nickel And Nickel Alloys

41 SFA-5.11 ENi-1 41 SFA-5.14 ERNi-1 41 SFA-5.30 IN61

42 SFA-5.11 ENiCu-7 42 SFA-5.14 ERNiCu-7 42 SFA-5.14 ERNiCu-8 42 SFA-5.30 IN60


48

TABLE-9 (CONTD.)



45 SFA5.11 ENiCrMo-11 45 SFA5.14 ERNiCrMo-1 45 SFA5.14 ERNiCrMo-8 45 SFA5.14 ERNiCrMo-9 45 SFA5.14 ERNiCrMo-11 45 SFA5.14 ERNiFeCr-1

Titanium And Titanium Alloys

51 SFA-5.16 ERTi-1 51 SFA-5.16 ERTi-2 51 SFA-5.16 ERTi-3 51 SFA-5.16 ERTi-4 52 SFA-5.16 ERTi-7 53 SFA-5.16 ERTi-9 53 SFA-5.16 ERTi-9ELI 54 SFA-5.16 ERTi-12

55 SFA-5.16 ERTi-5 55 SFA-5.16 ERTi-5ELI 55 SFA-5.16 ERTi-6 55 SFA-5.16 ERTi-6ELI 55 SFA-5.16 ERTi-15

Zirconium And Zirconium Alloys

61 SFA-5.24 ERZr2 61 SFA-5.24 ERZr3 61 SFA-5.24 ERZr4

Hard-Facing Weld Metal Overlay

71 SFA-5.13 All classifications

72 SFA-5.21 All classifications


49

SFA CLASSIFICATION

SFA NO. DESCRIPTION

5.01 Filler Metal Procurement guidelines 5.1 Carbon Steel Electrodes for Shielded Metal Arc Welding

5.2 Carbon and Low Alloy Steel Rods for Oxy fuel Gas Welding

5.3 Aluminium and Aluminium Alloy Electrodes for Shielded Metal Arc Welding

5.4 Stainless Steel Electrodes for Shielded Metal Arc Welding

5.5 Low-Alloy Steel Electrodes for Shielded Metal Arc Welding

5.6 Covered Copper and Copper Alloy Arc Welding Electrodes

5.7 Copper and Copper Alloy Bare Welding Rods and Electrodes

5.8 Filler Metal for Brazing and Braze Welding

5.9 Bare Stainless Steel Welding Electrodes and Rods

5.10 Bare Aluminium and Aluminium Alloy Welding Electrodes and Rods

5.11 Nickel and Nickel Alloy Welding Electrodes for Shielded Metal Arc Welding

5.12 Tungsten and Tungsten Alloy Electrodes for Arc Welding and Cutting

5.13 Solid Surfacing Welding Rods and Electrodes

5.14 Nickel and Nickel Alloy Bare Welding Electrodes and Rods

5.15 Welding Electrodes and Rods for Cast Iron

5.16 Titanium and Titanium Alloy Welding Rods and Electrodes

5.17 Carbon Steel Electrodes and Fluxes for Submerged Arc Welding

5.18 Carbon Steel Filler Metals for Gas Shielded Arc Welding

5.20 Carbon Steel Electrodes for Flux Cored Arc Welding


50

SFA CLASSIFICATION

SFA NO. DESCRIPTION

5.21 Composite Surfacing Welding Rods and Electrodes

5.22 Stainless Steel Electrodes for Flux Cored Arc Welding and Stainless Steel

Flux Cored Rods for Gas Tungsten Arc Welding

5.23 Low Alloy Steel Electrodes and Fluxes for Submerged Arc Welding

5.24 Zirconium and Zirconium Alloy Welding Electrodes and Rods

5.25 Carbon and Low Alloy Steel Electrodes and Fluxes for Electro-slag Welding

5.26 Carbon and Low Alloy Steel Electrodes for Electro-gas Welding

5.28 Low-Alloy Steel Electrodes and Rods for Gas Shielded Arc Welding

5.29 Low Alloy Electrodes for Flux Cored Arc Welding

5.30 Consumable Inserts

5.31 Fluxes and Brazing and Braze Welding

5.32 Welding Shielding gas

CHAPTER - A4

PROCEDURE FOR WELDER QUALIFICATION

A4. PROCEDURE FOR WELDER QUALIFICATION

1.0 SCOPE:

1.1 This chapter details the procedure for qualification of welder and performance monitoring.

2.0 CONTENTS:

1. Qualification of Welder.

2. Table-1 - Welder Qualification Requirements.

3. Figure-1 Fillet Weld Break Specimen.

Figure-2 Method of Rupturing.

Figure-3 Positions.

Figure-4 Plate Butt Weld Specimen.

Figure-5 Pipe Butt Weld Specimen.

Figure-6 Bend Specimen.

Figure-7 Bend Jig.

4. Record of Welder Performance Qualification Tests.

5. Welder performance monitoring.

QUALIFICATION OF WELDER

1.0 BASE METAL:

1.1 For selection refer Tables in Chapter II.

2.0 TEST COUPON:

2.1 Depending on the range to be qualified, choose the appropriate test coupon from Table - 1.

2.2 For plate butt welds, details of edge preparation shall be as per Figure-4.

2.3 For pipe butt welds, details of edge preparation shall be as per Figure-5.

2.4 For structural tack welds, refer Figure-1.

3.0 REQUIREMENT OF TESTS:

3.1 For Structural Tack Welders:

3.1.1 Break Test as per Figure-2.

3.2 For Plate Butt Welds:

3.2.1 Minimum of 2 specimens for bend test; one for root bend and other for face

bend. Width of specimen shall be 38 mm for plate thickness upto 9.5 mm. For

thickness greater than 9.5 mm, width of specimens shall be 10 mm and they

shall be side bend tested.

3.3 For Pipe Welder :

3.3.1 The order of removal of test specimens shall be as per Figure-6.

3.3.2 For width and number of bend specimens, refer table below:

TABLE

No. of Bend Specimens OD W Face Root Side

> 101.6 38.0 2 2 (**) 50.8 - 101.6 19.0 2 2 (**)

< 50.8 9.5 2 2 (**) <= 25.4 (++) 2 2 -

(**) for thickness greater than 9.5 mm, side bend test of width 9.5 mm may be substituted.

(++) Cut into 4 equal sections (with allowance for saw cuts or machine cutting); sharp corners to be rounded off.

OD - Outer diameter of pipe in mm.

W - Width of bend test specimen in mm.

3.4 For bend jig refer Figure-7, for thickness of bend specimen 9.5 mm; for other thicknesses (t) the dimension shall be as below :

A = 4t B = 2t C = 6t + 3.2 mm D = 3t + 1.6 mm

The above values are nominal.

3.5 Radiographic examination of test welds may be carried out in lieu of bend tests. Procedure and acceptance criteria are as per NDE Manual.

4.0 ESSENTIAL VARIABLES :

4.1 Changes to the following variables require requalification.

4.1.1 Process : Example : Change from GTAW to SMAW or vice versa.

4.1.2 Joint : A change from one type of bevel to another. Example : ‘vee’ bevel to ‘u’ bevel. 4.1.3 Base Metal :

A change in thickness or pipe diameter beyond the limits prescribed in Table-1.

4.1.4 Filler Metal:

A change from one F number to another F-number, except as specified in Table-1.

4.1.5 Positions:

Note: This procedure envisages qualification of welders to perform in all positions. Deviation to this is not recommended.

4.1.6 Gas:

Note: This procedure envisages test to pre-prescribed gas as for production welds. Deviation to this is not recommended.

4.1.7 Electrical Characteristics:

a) AC to DC and vice versa.

b) In DC, DCEN (Electrode Negative) to DCEP (Electrode Positive) and vice versa.

4.1.8 Technique :

Note : This procedure envisages only use of uphill progression technique.

ACCEPTANCE CRITERIA :

Structural Tack Welding :

No cracks.

No lack of fusion.

Undercut not exceeding 1 mm.

Not more than 1 porosity (max. diameter of porosity 2 mm).

Plate/Pipe Welding :

Visual Inspection :

a) No cracks.

b) No lack of fusion or incomplete penetration.

c) Not more than 1 porosity in a length of 100 mm of length of weld (max. porosity diameter 2mm).

5.0 Bend Test Results:

The convex surface of the bend test specimen shall be visually examined for surface discontinuities. For acceptance, the surface shall contain no discontinuities exceeding the following dimensions:

1. 3 mm measured in any direction on the surface.

2. The sum of the greatest dimensions of all discontinuities exceeding 1 mm but less than or equal to 3 mm, shall not exceed 10 mm.

3. The maximum corner crack of 6 mm, except when that corner crack resulted from visible slag inclusion or other fusion type discontinuities, then the 3 mm maximum shall apply. Specimens with corner cracks exceeding 6 mm with no evidence of slag inclusions or other fusion type discontinuities shall be disregarded, and a replacement test specimen from the original weldment shall be tested.

6.0 RETESTS:

6.1 A welder who fails to meet the acceptance criteria for one or more test specimens, may be retested as per this procedure after adequate practice.

7.0 VALIDITY :

7.1 When a welder meets the requirements of this procedure, the validity will be for a maximum of 2 years from the date of test, limited to validity specified by statutory authority, as applicable.

The validity may be extended by one year each time, based on satisfactory performance, with sufficient back up records.

8.0 REQUALIFICATION :

8.1 Requalification is required for the following :

a. Where there is a specific reason to doubt the skill of the welder.

b. Due to non-engagement of the welder for a continuous period of 6 months.

9. RECORDS:

The welding in charge at site shall maintain the following records:

a) Record of Welder Performance qualification Test (as per format).

b) Register of qualified welders (employer-wise) containing the following details:

1) Name of welder.

2) Age.

3) Tested for pipe / tube / plate / tack.

4) Performance Test No.

5) Validity.

6) Welder Code.

7) Remarks.

The above register shall be updated for deletions also.

Copies of welder identity card (including details as in 9.1 b and relevant variables

qualified).

Pertinent radiography reports.

10.0 ENCLOSURES :

1. Table-1 : Welder Qualification Requirements.

2. Record of Welder Performance Qualification Test.

3. Figure-1: Structural Tack Weld Specimen.

4. Figure-2 : Break Test.

5. Figure-3 : Weld Positions.

6. Figure-4 : Plate Butt Weld Specimen.

7. Figure-5 : Pipe Butt Weld Specimen.

8. Figure-6 : Order of Removal of Test Specimen.

9. Figure-7 : Bend Jig.

WELDER QUALIFICATION REQUIREMENTS

Table - 1

Sl.No. Test For Base6

Metal Note 1

Test Coupon

Dimension OD, t

Electrode6 to be used Note 2, 4

Weld Positions

Reference Figure

Range Qualified Dia. & T

Position Qualified

Electrode Qualified Note 2, 4

Remarks

(E6013) F2 3F & 4F Fig. 1 & 2 T-Unlimited All F2, F1 Refer Fig. 1,3 1 Structural tack P1 Gr 1 t=10mm or

12mm (E7018) F4 3F & 4F Fig. 1 & 2 T-Unlimited All F4 &

Below Refer

Fig. 1,3

t≥25mm F4 3G & 4G Fig.3 T≥3.2mm* All F4 & Below

2 Plate Welder (Structural) - do -

t<25mm F4 3G & 4G Fig.3 T>3.2mm*

≤2t All F4 &

Below

t≥13mm F4 2G, 3G & 4G Fig.3

T-Unlimited OD≥610mm

All F4 & Below

3 Plate Welder (Other than structural)

- do - t<13mm F4 2G, 3G &

4G Fig.3 T≤2t OD≥610mm

All F4 & Below

OD<25mm F4 6G Fig.3 Test piece Dia.& above All F4 &

Below

OD≥25mm & ≤73mm

F4 6G Fig.3 25mm & above All F4 &

Below

OD>73mm F4 6G Fig.3 73mm & above All F4 &

Below

t<13mm F4 6G Fig.3 T≤2t All F4 & Below

4 Pipe Welder - do -

t≥13mm F4 6G Fig.3 T-Unlimited All F4 & Below

* Also qualifies for welding fillet welds on material of unlimited thickness.

Table - 1 (contd...) NOTES:

1. For P grouping refer Chapter II.

2. For F grouping refer Chapter III.

3. Base material limitation:

a. Where test coupons belong to P1 thro’ P11, welder is qualified for base materials P1 thro’ P11.( ASME Sec IX QW 423, Alternate base material for welder qualification)

It means, if a welder is qualified with carbon steel material, he is also qualified for alloy steel and vice versa.

b. Use appropriate F group electrodes.

4. Qualification in one F number, qualifies for that F-number only, except as stated below in A, B, C & D.

A. Qualification in F4 qualifies for F4 and below.

B. Qualification in F5 qualifies for F5 only.

C. Qualification in any of F41 thro’ F45 qualifies for F41 thro’ F45.

D. For non-ferrous materials, the base materials shall be typical of production material and appropriate filler materials shall be selected. Qualification is limited to the base material, process and filler F group. Diameter and thickness limitations apply as per Table-1.

OD = outer diameter, t = thickness of test coupon; T = thickness qualified.

5. Where qualification is for GTAW followed by SMAW, the welder is also qualified upto 6 mm thickness by GTAW process.

6. Base material indicated is carbon steel; for other base materials, corresponding electrodes are to be chosen. Also for GTAW process, the corresponding filler wire should be chosen.

TACK WELDER QUALIFICATION

RECORD OF WELDER PERFORMANCE – QUALIFICATION TEST Performance Test No.

Date: Site:

Welder’s Name & Address: Welder Code:

Material Groupings permitted: Welding Process: Thickness Qualified: Position(s) Qualified: (This performance test is as per Dia Qualified: Procedure No. )

TEST MATERIAL

Specification: Filler Material: Thickness (and Dia. of pipe): SFA No.: Shielding Gas(es) AWS Classification:

PROCESS VARIABLES

Position of test weld: Current: Polarity: Pre-heat temp: Inter Pass Temp: Post-heat Temp: Test Joints Test Results Type Bend Results Type Bend Results Type Bend Results Type Bend Results Radiography Ref. & Results: (sketch)

Welder’s Signature

Agency Conducting Test

We certify that the statement in this record are correct and that the test weld were prepared, welded and tested in accordance with requirements.

This is valid upto __________________________

Welding In-charge / BHEL

WELDER PERFORMANCE MONITORING

1.0 PURPOSE:

This procedure deals with monitoring the performance of welders engaged at sites.

This procedure is applicable where radiography is performed.

2.0 PROCEDURE:

2.1 The welder performance shall be monitored on a calendar month basis.

2.2 Extent of radiography shall be representative of weekly outputs of the welder.

2.3 Quantum of radiography shall be as per contractual requirements.

2.4 Evaluation of welds radiographed shall be as per NDE manual or other documents as

specifically applicable.

2.5 Welder performance evaluation:

2.5.1 For welds dia. ≤ 88.9 mm:

2.5.1.1 The percentage defectives (repairable) is calculated as a percentage of number of

unaccepted welds to those radiographed.

2.5.1.2 Upto and including 5% defectives: performance is satisfactory else unsatisfactory.

2.5.2 For welds dia. > 88.9 mm and plate welds:

2.5.2.1 The percentage defectives is calculated as a percentage of length of defectives

repairable to the length radiographed.

2.5.2.2 Upto and including 2.5% defectives: performance is satisfactory else unsatisfactory.

2.6 When a welder gives unsatisfactory performance for a continuous period of 3 months,

he shall be requalified.

2.6.1 Requalification of welder shall be called for when there is a specific reason to question

his ability to make acceptable welds. This shall override requirements of clause 2.6.

2.7 Welds produced during any month shall be radiographed and evaluated latest by 10th

of the succeeding month.

2.7.1 Under circumstances when clause 2.7 is not satisfied for any particular welder, he

may be disengaged from the job till such time his performance can be evaluated for the month in study.

2.7.2 Site in-charge may waive the restriction imposed in 2.7.1 reviewing the situations for

non-compliance of cl.2.7 and may allow engagement of the welder in question for a

period not exceeding one successive month to the month in study.

3.0 RECORDS:

3.1 Welding in-charge shall prepare and maintain Welder Performance Records, welder-

wise.

CHAPTER - A5

INSPECTION OF WELDING

A5. INSPECTION OF WELDING 1.0 PURPOSE:

This procedure provides details for performing visual inspection of weld fit-ups, welding in progress and completed welds.

2.0 REFERENCE:

2.1 Contract drawings.

2.2 Erection Welding Schedule (supplied by Units) or equivalent.

2.3 Welding Procedure Specification, where supplied.

2.4 Indian Boiler Regulations (for boilers erected in India)

3.0 GENERAL REQUIREMENTS:

3.1 Ensure that the components to be welded are in accordance with the contract drawings, Welding Schedule and other relevant documents.

3.2 The condition of welded surfaces to be inspected must be clean and dry.

3.3 There shall be sufficient lighting to allow proper interpretation of visual inspection.

4.0 WELD FIT-UP INSPECTION:

4.1 The surface to be welded shall be smooth and free from deep notches, irregularities, scale, rust, oil, grease and other foreign materials.

4.2 Piping, tubing and headers to be joined shall be aligned within allowable tolerances on diameters, wall thicknesses and out-of-roundness as below:

Maximum permissible mis-alignment at bore

Max. Misalignment (mm) Bore (mm) For GTAW For SMAW

Upto 100 1.0 1.0 Over 100 to 300 1.6 1.6 Over 300 1.6 2.4

4.3 While fit up, components to be welded shall not show any appreciable off-set or misalignment

when viewed from positions apart.

4.4 The root opening of components to be joined shall be adequate to provide acceptable penetration.

4.5 On fillet welds, the parts to be joined shall be brought as close to contact as practical, although in most instances a small opening between the parts is desirable.

4.6 Root gaps should be maintained at 1.6 mm - 2.4mm (refer relevant document).

4.7 Weld area should be protected from drafts and wind, to maintain inert gas shield.

5.0 CHECKS DURING WELDING OPERATION:

5.1 Ensure the required minimum preheat temperature is applied and established during welding.

5.2 Ensure correct electrode/filler metal is used for welding.

5.3 Tack welds are examined by the welder before they are incorporated in the final weld.

5.4 Ensure proper drying/holding of electrodes prior to use.

5.5 Ensure correct inter pass temperature is maintained.

5.6 Ensure proper cleaning of weld between beads.

6.0 CHECKS ON THE COMPLETED WELD:

6.1 No visible cracks, pin-holes or incomplete fusion.

6.2 The weld surface must be sufficiently free of coarse ripples, grooves, overlaps, abrupt ridges and valleys, visible slag inclusions, porosity and adjacent starts and stops.

6.3 Undercuts not to exceed 0.8 mm.

6.4 Where inside surface is readily accessible, the same shall be inspected for excess penetration and root concavity. The permissible limits are given below :

Root concavity: max of 2.5 mm or 20% of thickness at weld, whichever is lesser, provided adequate reinforcement is present.

Excess penetration: upto and including 3.2 mm.

6.5 For plate butt welds, the weld reinforcement should not exceed 3.2 mm.

6.6 For circumferential joints in piping and tubing the maximum weld reinforcements permitted are given below :

Maximum Permissible Reinforcements

Thickness of base metal

For service above 400°C

Temperature upto & incl. 400°C

Upto 3.0 2.0 2.5 Over 3 to 5 2.0 3.0 Over 5 to 13 2.0 4.0 Over 13 to 25 2.5 5.0 Over 25 to 50 3.0 6.0 Over 50 4.0 6.0

All dimensions in mm.

6.7 There shall be no overlaps.

The faces of fillet welds are not excessively convex or concave and the weld legs are of in proper length.

6.8 In case of weld joints in pressure parts and joints like ceiling girder, the weld joint must be suitably identified.

CHAPTER - A6

REPAIR WELDING

A6. REPAIR WELDING 1.0 PURPOSE:

1.1 This procedure details steps to be taken for weld repairs.

2.0 PROCEDURE:

2.1 Unacceptable welds, based on visual inspection or NDE, shall be repaired.

2.2 Removal of Defects:

2.2.1 The identified defect area shall be marked on the part.

2.2.2 The defects may be removed by grinding/thermal gouging.

2.2.2.1 Where thermal gouging is done, adopt the requirements of preheating as detailed in Heat Treatment Manual.

2.2.2.2 However, only grinding is permitted for the last 6 mm from the root.

2.3 Removal of defects shall be verified by visual inspection, PT, MT, RT as appropriate.

2.4 The profile of ground portion shall be smooth and wide enough to permit proper fusion during repair welding.

2.5 Repair welding shall be carried out as per the procedure for the initial weld.

2.6 Repair weld shall undergo the same type of NDE as the initial weld.

2.7 Repeat steps 2.1 to 2.6 till acceptable weld is made.

2.8 Where cutting, re-edge preparation and re-welding the joint will yield better results, the same shall be followed.

3.0 Where a specific repair procedure is supplied by the Manufacturing Unit, the same shall be followed.

4.0 RECORDS :

4.1 Records pertaining to the repairs like Welder, NDE records shall be maintained.

WELDING MANUAL A7. SAFE PRACTICES IN WELDING 74

74

CHAPTER - A7

SAFE PRACTICES IN WELDING


75

SAFE PRACTICES IN WELDING

(This is included for information purposes only.)

This covers many of the basic elements of safety general to arc welding processes. It

includes many, but not all, of the safety aspects related to structural welding. The

hazards that may be encountered and the practices that will minimize personal injury

and property damage are reviewed here.

J1 Electrical Hazards

Electric shock can kill. However, it can be avoided. Live electrical parts should not be

touched. Read and understand the manufacturer’s instructions and recommended

safe practices. Faulty installation, improper grounding, and incorrect operation and

maintenance of electrical equipment are all sources of danger.

All electrical equipment and the work-pieces should be grounded. A separate

connection is required to ground the work-piece. The work lead should not be

mistaken for a ground connection.

To prevent shock, the work area, equipment, and clothing should be kept dry at all

times. Dry gloves and rubber soled shoes should be worn. The welder should stand

on a dry board or insulated platform.

Cables and connections should be kept in good condition. Worn, damaged or bare

cables should not be used. In case of electric shock, the power should be turned off

immediately. If the rescuer must resort to pulling the victim from the live contact, non-

conducting materials should be used. A physician should be called and CPR

continued until breathing has been restored, or until a physician has arrived.

J2 Fumes and Gases

Many welding, cutting, and allied processes produce fumes and gases which may be

harmful to one’s health. Fumes and solid particles originate from welding

consumables, the base metal, and any coating present on the base metal. Gases are

produced during the welding process or may be produced by the effects of process


76

The possible effects of over-exposure to fumes and gases range from irritation of

eyes, skin, and respiratory system to more severe complications. Effects may occur

immediately or at some later time. Fumes can cause symptoms such as nausea,

headaches, dizziness, and metal fumes fever. Sufficient ventilation, exhaust at the

arc, or both, should be used to keep fumes and gases from breathing zones and the

general work area.

J3 Noise

Excessive noise is a known health hazard. Exposure to excessive noise can cause a

loss of hearing. This loss of hearing can be either full or partial, and temporary or

permanent. Excessive noise adversely affects hearing capability. In addition, there is

evidence that excessive noise affects other bodily functions and behavior. Personal

protective devices such as ear muffs or ear plugs may be employed. Generally, these

devices are only accepted when engineering controls are not fully effective.

J4 Burn Protection

Molten metal, sparks, slag, and hot work surfaces are produced by welding, cutting

and allied process. These can cause burns if precautionary measures are not used.

Workers should wear protective clothing made of fire resistance material. Pant cuffs or

clothing with open pockets or other places on clothing that can catch and retain molten

metal or sparks should not be worn. High top shoes or leather leggings and fire

resistant gloves should be worn. Pant legs should be worn over the outside of high top

boots. Helmets or hand shields that provide protection for the face, neck, and ears,

should be worn, as well as head covering to protect. Clothing should be kept free of

grease and oil. Combustible materials should not be carried in pockets. If any

combustible substance is spilled on clothing it should be replaced with fire resistance

clothing before working with open arcs or flame.

Appropriate eye protection should be used at all times. Goggles or equivalent also

should be worn to give added eye protection.

Insulated gloves should be worn at all times when in contact with hot items or

handling electrical equipment.


77

J5 Fire Prevention

Molten metal, sparks, slag, and hot work surfaces are produced by welding, cutting,

and allied processes. These can cause fire or explosion if precautionary measures

are not used.

Explosions have occurred where welding or cutting has been performed in spaces

containing flammable gases, vapours, liquid, or dust. All combustible material should

b e removed from the work area. Where possible, move the work to a location well

away from combustible materials. If neither action is possible, combustibles should be

protected with a cover or fire resistant material. All combustible materials should be

removed or safely protected within a radius of 35 ft. (11m) around the work area.

Welding or cutting should not be done in atmospheres containing dangerously reactive

or flammable gases, vapours, liquid, or dust. Heat should not be applied to a container

that has held an unknown substance or a combustible material whose contents when

heated can produce flammable or explosive vapours. Adequate ventilation should be

provided in work areas to prevent accumulation of flammable gases, vapours or dusts.

Containers should be cleaned and purged before applying heat.

J6 Radiation

Welding, cutting and allied operations may produce radiant energy (radiation) harmful

to health. Everyone should acquaint themselves with the effects of this radiant

energy.

Radiant energy may be ionizing (such as X-rays) or non-ionizing (such as ultraviolet,

visible light, or infrared). Radiation can produce a variety of effects such as skin burns

and eye damage, if excessive exposure occurs.

Some processes such as resistance welding and cold pressure welding ordinarily

produce negligible quantities of radiant energy. However, most arc welding and

cutting processes (except submerged arc when used properly), laser welding and

torch welding, cutting, brazing, or soldering can produce quantities of non-ionizing

radiation such that precautionary measures are necessary.

78

78 /172

1. Welding arcs should not be viewed except through welding filter plates.

2. Transparent welding curtains are not intended as welding filter plates, but

rather, are intended to protect passers by from incidental exposure.

3. Exposed skin should be protected with adequate gloves and clothing as

specified.

4. The casual passers by to welding operations should be protected by the use of

screens, curtains, or adequate distance from aisles, walkways, etc.

5. Safety glasses with ultraviolet protective side shields have been shown to

provide some beneficial protection from ultraviolet radiation produced by

welding arcs.

WELDING MANUAL PART – B 79

PART - B

Table of Contents

Chapter Description

No. off

Part-B & Table of Contents 79,80

Pre-Assembly & Welding of Ceiling Girders 81-92 B-1

Improved techniques for ceiling girder 93-99

Erection Welding Practice for SA 335 P91 Material

100-120

Argon Purity Level

121-122 B-2

Use of resistance heating for PWHT of P-91 pipes

123-126

B-3 General Tolerances for welding structures - (Form and position)

127-130

B-4 Welding of pipes and pipes shaped connections in Steam Turbines, Turbo-Generators and Heat Exchangers

131-133

B-5 Instructions for carrying out condenser plate and neck welding

134-137

B-6 Repair procedure of arresting the leakage of strength welds on tube to tube sheet joints of ‘U’ tube HP heater

138-140

B-7 Repair procedure of grey cast iron castings 141-144

B-8 Special Instructions for the repair of Steam Turbine Casings

145-151

B-9 Gas Metal Arc Welding 152-155

B-10 Orbital Welding 156-168

B-11 Edge Preparation Details 169-170

B-12 Erection Procedure for Rear Water box and Rear water Chamber in condenser

171-175

Notes for Welding thermo couples pads & clamps

Welding and PWHT sequence for lower ring drum B-13

Work Instructions For Demagnetisation

176-178

B-14 Erection Welding Practice for SA 213 T91 Material 179-184

CHAPTER - B1

PRE-ASSEMBLY AND WELDING OF CEILING GIRDERS

PART - B

B1. PRE - ASSEMBLY AND WELDING OF CEILING GIRDERS A) Pre-assembly of Ceiling Girder:

- Identify the pieces for the following:

- Work order No.

- PGMA

- DU No.

- Girder designation

- Position the girder pieces over the pre-assembly bed inside the furnace cavity

keeping left, middle and right side pieces following shop punch mark details.

- Check and measure the following:

- Camber, length & diagonal

- Sweep

- Twist

- Edge preparation and condition

- Web height at extended portion and compare with flange to flange inner

distance (for easy insertion 1mm gap to be ensured on either side. If

required grind web ends to achieve the above).

- Major deviation if any, to be informed to manufacturing unit for corrective

action. Rectify the deviations accordingly.

B) Final check and finishing :

i) Repeat the dimensional check, carried out prior to welding, after Post Weld

Heat Treatment and compare the two.

ii) Clean and paint the weld region.

iii) Check the holes drilled in the web of ceiling girder (distance from the end and

Centerline distance of each group of holes, which is the Centerline distance of

welded beams).

iv) Check the size and location of pad plates welded on the web of ceiling girder.

These pad plates are to be welded only on sides and bottom face.

v) Ensure pre-assembly bed is made on the leveled and consolidated area to

avoid sinking during placement of girders on the bed.

vi) Ensure the pre-assembly bed members are properly spaced to avoid sagging of

girder pieces when they are placed over it. (Refer Fig. - 1).

vii) Match the pieces as per match marks provided in the pieces. Ensure the

orientation of girder pieces as per drawing (Ref. Fig. - 2 & 3).

1.0 Fit-up:

a) While leveling the pieces, the reference lines punched on the web at about 1 to

1.5M level from bottom flange may be taken as reference.

b) While adjusting the overall length of the girder, check the distance between

girder pin connection bolt hole centres which is marked in the bottom flange and

as well as on the top flange.

c) While adjusting the overall straightness of the girder piece the longitudinal centerline

of the girders and web line marked on the pieces may be taken as reference.

d) While matching the piece, flange root gap and web root gap shall be maintained

between 4 to 6m and 6 to 8mm respectively in the field joint areas (Ref. Fig. - 3).

e) The parts to be joined by filled welds shall be brought as close as practicable.

f) Abutting parts to be joined by butt welds shall be carefully aligned. An offset

exceeding 10% of the thickness of the thinner part, but in no case more than

3.2mm may be permitted.

g) Members to be welded shall be properly aligned and held in position by bolts,

clamps, wedges and other suitable devices until welded is completed.

PRE ASSEMBLY AND WELDING OF CEILING GIRDERS

h) No tack weld to be made in the web for aligning. Instead ‘L’ clamps and wedges

shall be used for web alignment to keep the joint free during the welding of

flange joint.

i) Ensure after dimensional check-up the girder assembly is properly locked in

position by using stoppers. ‘L’ clamps, wedges, guy ropes and struts or by any

suitable device to avoid distortion during welding and Post Weld Heat Treatment

operations. Ensure proper locking, in such a way that the girder assembly can

move longitudinally during welding and Post Weld Heat Treatment operations to

avoid accumulation of thermal stress.

2.0 Dimensional check-up:

a) Section depth and flange width can be checked as cross reference since these

are already checked up in shop.

Tolerance: Section depth upto 1 M - ± 3mm

Above 1 M upto 2 M - ± 4.5mm

Above 2 M - + 7.5mm - 4.5mm Flange width - ± 3mm

b) Check the following dimensions prior to clearing the assembly for welding and

are to be recorded in the log sheet.

1. Level of the girder assembly.

2. Deviation in straightness on both flanges.

3. Flatness of web on both vertical and horizontal axis.

4. Out-of-squareness of the assembly.

5. Flange and web joint alignment.

6. Overall length of the assembly.

7. Flatness of bottom flange in girder pin locations.

8. Longitudinal and cross diagonals of the assembly.

9. Welded beam location distance on either side of the field joint.

3.0 Dimensional tolerance:

1. Individual piece camber and sweep - Max. 5mm

2. Individual piece length - ± 5mm

3. Level of the girder assembly - Max. 5mm

4. Deviation in straightness on total length - Max. 15mm

5. Flatness of web - Max. 10mm

6. Out-of-squareness of assembly - Max. 8mm

7. Overall length of assembly - ± 15mm

(with the recommended gap for welding of web and flange at field joints, the

overall length of the girder shall be achieved within limits after allowing weld

shrinkage).

8. Flatness of bottom flange at girder pin

Connection location - Max. 2mm

9. Longitudinal and cross diagonal of

assembly (difference) - Max. 15mm

4.0 Pre-heating :

a) Pre-heat temperature required for various range of plate material thickness is

As follows :

P. No. of Header Material

Thickness (mm)

Preheat °C

Post Heating °C

PWHT °C

t ≤ 19 Nil Nil Nil

19 < t ≤ 25 Nil Nil 595 - 625

25 < t ≤ 75 100 Nil 595 - 625

P1Gr 1

t > 75 150 Nil 595 - 625

t < 19 Nil Nil 620 – 650

19 < t ≤ 25 Nil 150

for 2 hours 620 - 650

19 < t ≤ 75 100 150

for 2 hours

620 - 650

P1Gr 2

t > 75 150 150 for 2 hours

620 - 650

b) It is desirable to pre-heat using electric resistance coil heaters. Use of self pre-

heat is not permitted.

c) When electrode of 3mm and below are used the minimum pre-heat temperature

shall be increased by 50°C from the pre-heat temperature mentioned above.

5.0 Welding:

a) Welders shall be qualified as per Welding Manual.

b) Welding consumables conforming to the design requirements shall be used.

c) Selection of welding consumables shall be out of the “Approved list of welding

consumables” issued by WTC, Tiruchy.

d) Welding consumables used for this are to be stored properly and issued after

necessary baking. Electrodes issued for job should be kept in holding ovens

and maintain the temperature. The above are to be carried out as per welding

manual.

e) Pre-heating requirements for materials shall be strictly followed as mentioned.

f) The sequence of welding to be followed as indicated in the Fig. - 4.

g) Complete the root plus three runs on inner side as per the sequence shown in

Fig. - 4.

h) Back gouge / chip the weld from outer side and carryout LPI / MPI tests for ensuring defect free root weld.

i) Complete the outer side weld for three runs as per the sequence indicated in

Fig. - 4.

j) Complete the flange joint weld, around 60% thickness of the joint on both sides

of flange alternately (inner and outer) as per the sequence shown in Fig. - 5.

k) After completion of 60% of flange welding check the web alignment (adjust with

wedges to achieve web alignment if required).

l) Check the root gap. If required, ground to get the gap.

m) Preheat to 150°C and adopt the weld sequence for the web root welding plus

two runs as shown in Fig. - 4.

n) Back gouge / chip the second side of the weld to achieve defect free root weld.

o) Carryout LPI / MPI on the weld joint on root side.

p) Complete the two runs of weld on the second side as per the sequence shown

in Fig. - 5.

q) Complete the balance flange joint and then the balance web joint as per the

sequence indicated respectively in Figures - 4 & 5.

Note: The welding sequence of flange and web can be changed depending on the

number of welders engaged.

r) Complete the fillet welding between flange and web on both sides.

s) Carry out the post heating of weld joint for 1 hour at 250°C.

t) Welding shall not be done when the surfaces are wet, oil traces are seen or

exposed to rain or high wind or when the welders are exposed to inclement

conditions.

u) The sizes and length of weld shall not be less or substantially in excess than the

specified in the drawing.

CEILING GIRDER WELDING (SEQUENCE)

PRE ASSEMBLY AND WELDING OF CEILING GIRDERS

6.0 Post Weld Heat Treatment :

For C&C - Mn Steel : (IS 2062, ASTM A36, BS 4360 Gr 43D, DIN 17100 ST 37.3,

JIS 3106 SM 41, 3192)

a) Butt welds in plates over 50mm thick shall be subjected to Post Weld Heat

Treatment. For unequal thickness of plates, the groove depth at the weld shall

be considered for Post Weld Heat Treatment.

b) The fillet welds for fixing attachments like pads etc. made on tension flanges

over 50mm thick shall also be post weld-heat treated.

For high tensile steels : (DIN 17100 st 52.3, is 961-HTW).

a) Butt welds in plates 50mm and above thick shall be Post Weld Heat Treated.

For unequal thickness of plates, the groove depth at the weld shall be

considered for Post Weld Heat Treatment.

b) The fillet welds for fixing attachments like pads etc. made on tension flanges

50mm and above thickness shall also be post weld heat treated.

For the fillet welds joining the tension flange to web need not be post weld heat treated.

All the post weld heat treatment cycle range shall be 600°C to 650°C. The above

cycle shall be controlled within a tolerance of ± 10°C. The recommended temperature

for Post Weld Heat Treatment must be selected as the mid point of the recommended

range.

Soaking time for Post Weld Heat Treatment shall be 1 hr./ 25mm thick upto 50mm and

2 hr. + 15 minutes for each additional 25mm thickness over 50mm.

The heating rate above 400°C and cooling rate after Post Weld Heat Treatment upto

400°C shall be as follows :

Thickness range Rate of heating (Max.)

Rate of cooling (Max.)

≤ 25mm 220°C / hr 110°C / hr > 25 ≤ 50mm 110°C / hr 110 °C / hr > 50 ≤ 75mm 75°C / hr 110°C / hr > 75mm 55°C / hr 65°C / hr

Autographic calibrated recorder shall be used to record rate of heating, soaking and

rate of cooling.

Fixing and location of thermocouple shall be made as per details in Welding Manual.

(Typical case - Refer to Figures - 6 & 7).

7.0 Non-Destructive Examination (NDE) :

Ceiling girder assembled keeping web vertical. CUT EDGES a) Flame cut welding edges for thickness > 38mm - 100% MPI. b) Random MPI for all edges of thickness > 20mm. Weld build up areas : Weld build up areas in flanges and web - 100% MPI / LPI. Flange butt joint 100% MPI for thickness > 25mm. 100% RT for thickness > 32mm. Web butt joint :

a) 100% LPI for back gouged / chipped area before second side welding. b) SPOT RT / 100%. The defective areas shall be further repaired and re-

radiographed.

Fillet welds : a) Fillet weld between (tension) bottom flange and web - 100% MPI. b) Other fillet welds - random MPI.

8.0 Final check-up and finishing :

After Post Weld Heat Treatment, surface to be cleaned properly and painted with two coats

of red oxide primer.

Cement washed surfaces are to be cleaned properly in the HSFG bolt area including cleat

angles.

Dimensional check-up of girder shall be carried out and to be recorded in the log sheets.

‘No stay arc’ shall be done on heat treated members.

IMPROVED TECHNIQUES

FOR

CEILING GIRDER

WELDING SEQUENCE FOR CEILING GIRDER

Sl. No.

STEP No.

WELDING SEQUENCE

1 1 Pre heat and welding root run at flange

2 2 Weld root run at flange

3 Repeat step 1 and 2 and weld three runs

Post heat and cool to room temperature

4 Back grind and LPI (at flange)

5 3 Pre heat and weld Root + Three runs (at other side of the flange)

6 Follow steps 1, 2 and 3 alternatively and welding upto 60% of the thickness of the flange

7 Correct the mismatch and check the root gap of the web and grind if required

8 4 Weld root run (at web)

9 5 Weld root run (at web)

10 4 Weld two run (at web)

11 5 Welding two run (at web), post heat and cool to room temperature

12 Back grinding and LP (at web)

13 Grind the flange welding and take intermediate RT if required

14 6 Root run (at other side of the web)

15 7 Root run (at other side of the web)

16 6 Weld two run at web

17 7 Weld two run at web

18 1,2 Weld three run at flange

19 5 Weld three run at flange

20 Follow steps 1,2 and 3 alternatively and complete the flange welding

21 4 Weld three run at web




25 Follow steps 4, 5,6,7 alternatively and complete the web welding

26 8 Welding root +two run (at flange +web)

27 9 Welding root +two run (at flange +web)

28 Follow step 8 and 9 alternatively(each three run and complete flange +web fillet

welding)

BHEL : ___________________ SITE

Unit No.: _________________________

WELDING JOB CARD

Unit no.

:

Area : Boiler/TG/PCP

Card no. : 002 Date 26/11/2000

PGMA, DU : 35/211

Joint No. : GRBLHS

Drg Ref : Flange Web

Dia X Thick : PL 100X75 PL 40 x 25

Material : IS8500Fe540 IS2062Fe410B

Welder no.(s) : ST043(BOTTOM) ST082(TOP)

Date of welding : 26/11/200

Filler wire : -

Electrode : E8018B2 E7018

Preheat : 150 deg.c 120 deg c

Post heat : 250 deg.c/1 hour 150deg.c/1 hour

Inter pass temp : 300 deg.c max 300 deg.c max

Welding Engr.

BHEL : ______________SITE

Unit : ______________

STRESS RELIEF (S.R.) JOB CARD

Unit no.

:

Area : Boiler/TG/PCP

Card no. : 007 Date 04/01/2001

PGMA, DU :

Joint No. : GRERWS (Unit-111)

Drg Ref : Flange Web

Dia x Thick : PL 100X75 PL 36 x 25

Material : IS8500Fe540 IS2062Fe410B

NDE Cleared on : 04/01/2001 Report no.

Required Actual

Rate of heating Max deg c / hour 55 52

Soak temperature deg c : 625+/-10 630

Soak time Minutes : 165 165

Rate of cooling Max deg.c/hour : 65 62

Welding Engr.

WELDING MANUAL B-2 ERECTION WELDING PRACTICE FOR SA335 P91 MATERIAL 100

CHAPTER - B2

ERECTION WELDING PRACTICE FOR SA335 P91 MATERIAL


B2. ERECTION WELDING PRACTICE FOR SA 335 P91 MATERIAL 1.0 SCOPE

1.1 This document details salient practices to be adopted during erection of SA335 P91

material.

2.0 MATERIAL

Materials shall be identified as follows.

1) Colour Code : Brown & Red

2) Hard Stamping : Specification, Heat No, Size.

3) Paint / Stencil : WO DU, as per the relevant drawing & document.

2.1 When any defect like crack, lamination, deposit noticed during visual examination the

same shall be confirmed by Liquid Penetrant Inspection. If confirmed, same shall be

referred to unit.

3.0 ERECTION 3.1 Edge Preparation and fit up 3.1.1 Cutting of P-91 material shall be done by band saw / hacksaw / machining / grinding only.

Edge preparation (EP) shall be done only by machining. In extreme cases, grinding

can be done with prior approval of Welding Engineer/Quality Assurance Engineer.

During machining /grinding, care should be taken to avoid excessive pressure to

prevent heating up of the pipe edges.

3.1.2 All Edge Preparations done at site shall be subjected to Liquid Penetrant Inspection

(LPI). Weld build-up on Edge Preparation is prohibited.

3.1.3 The weld fit-up shall be carried out properly to ensure proper alignment and root gap.

Neither tack welds nor bridge piece shall be used to secure alignment. Partial root

weld of minimum 20mm length by GTAW and fit-up by a clamping arrangement is

recommended. Use of site manufactured clamps for fit up is acceptable .The

necessary preheat and purging shall be done as per clause 4.1 and 3.2.2

3.1.4 The fit-up shall be as per drawing. Root gap shall be 2 to 4 mm; root mismatch shall

be within 1-mm. Suitable Reference punch marks shall be made on both the pipes

(at least on three axis)

(a) At 200 mm from the EP for UT.

(b) At 1000 mm from the EP for identifying weld during PWHT.


3.2.0 FIXING OF THERMOCOUPLE (T/C) AND HEATING ELEMENTS DURING PREHEATING AND PWHT

3.2.1 No Preheating is required for fixing T / C with resistance spot welding.

Following are the equipment / facilities for heating cycles.

(1) Heating methods : Induction heating

(2) Thermo couples : Ni-Cr / Ni-Al of 0.5 mm gauge size.

(3) Temp.Recorders : 6 Points / 12 Points.

3.2.2 ARRANGEMENT FOR PURGING :-

Argon gas with requisite quality shall be used for purging the root side of weld.

The purging dam (blank) shall be fixed on either side of the weld bevel prior to pre-

heating. The dam shall be fixed inside the pipe and it shall be located away from

the heating zone. Purging is to be done for root welding (GTAW) followed by two

filler passes of SMAW in case of butt welds. Purging is not required in the case of

nozzle and attachment welds, when they are not full penetration joints. The

Argon to be used shall be dry.

The flow rate is to be maintained during purging is 10 to 26 litres / minute and for

shielding during GTAW is 8 to 14 litres / minute. (A minimum flow rate as per

welding Procedure specification shall be maintained).

Start purging from inside of pipe when root temperature reaches 220deg C. Provide

continuous and adequate Argon Gas to ensure complete purging in the root area.

The minimum pre-flushing time for purging before start of welding shall be 5

minutes, irrespective of the pipe size.

Wherever possible, solid purging gas chambers are to be used which can be

removed after welding. If not possible, only water-soluble paper is to be used.

Plastic foils that are water-soluble are NOT acceptable.

3.2.3 USING ALUMINIUM DAM ARRANGEMENT:

In order to retain the Argon gas at the inside of the pipe near root area of the weld

joint, the purging dams made of Aluminium and permanite gaskets may be provided

during the weld fit-up work as indicated in the sketch.

The Aluminium discs shall be firmly secured with a thin wire rope. After completion

of the root welding followed by two filler passes, the disc may be pulled outwards

softly.

CAUTION: ENSURE REMOVAL OF PURGE DAM ARRANGEMENT AFTER WELDING


3.2.4 USING OF WATER SOLUBLE PAPER :

The dams can be made of water-soluble paper for creating the purging chamber.

The advantage in such dam arrangement is that dissolving in water can flush the

dams. The following are different methods used.

4.0 WELDING / WELDERS QUALIFICATION :

Only Qualified welding procedures are to be used. Welders Qualified as per ASME

Sec IX and IBR on P91 material shall only be engaged. Welders log book to be

maintained and welders performance to be monitored by site welding engineer /

Quality assurance engineer. The applicable WPS for P91+P91 shall be WPS

N0.1034.

4.1 PREHEATING:

Prior to start of pre heating ensure that surfaces are clean and free from grease , oil

and dirt. Preheating temp shall be maintained at 220 deg C (min) by using

Induction heating The Temperature shall be ensured by using a Calibrated

autographic recorder and two calibrated thermo couples fixed at 0 deg and 180 deg

positions on both pipes 50 mm away from the EP. The thermocouple shall be

welded with the condenser discharge portable spot welding machine. The pre

heating arrangements shall be inspected and approved by welding engineer /

Quality Assurance Engineer. ( Ref Fig - 1)


Alternate arrangements shall be made during power failure. Two additional spare

thermocouple to be fixed(as described above) for emergency use. Gas burners

shall be employed to maintain the Temperature until the power resumes.

4.2 WELDING:

Root Welding shall be done using GTAW process ( as per WPS) five minutes after

the start of argon purging. Filler wire shall be clean and free from rust or oil. Argon

Purging shall be continued minimum two filler passes of SMAW.

4.3 STORAGE OF WELDING CONSUMABLES :

a. Welding consumables are received with proper packing and marking which

includes the relevant batch number for easy identification.

b. Electrodes are stored in their original sealed containers / packages until issued

and kept in dry and clean environment as per the instructions of electrode

manufacturers, taking care of shelf life.

c. Welding filler wires are received with proper packing and marking which

includes the relevant batch number for easy identification.

d. The filler wires are stored in their original packages until issue and kept in dry

and clean environment.

4.3.1 The electrode GTAW wires issued to the welders should be controlled through

issue slips. SMAW electrodes used must be dried in drying ovens with calibrated

temperature Controller. The drying temp shall be as recommended by the

electrode manufacturer. The drying Temp shall be 200 - 300 deg C for two hours if

it is not specified by the manufacturer. Portable flasks shall be used by the welders

for carrying electrodes to the place of use. The electrodes shall be kept at

minimum100 deg C in the flask. Welding shall be carried out with short arc and

stringer bead technique only.

4.4 The inter-pass temperature shall not exceed 350 deg C. After completion of Welding

bring down the temp to 80 - 100 deg C and hold it at this temp for one hour

minimum. The PWHT shall commence after completing one hour of soaking.

CAUTION:- No LPI / Wet MPI shall be carried out on weld before PWHT.


5.0 POST WELD HEAT TREATMENT :

Arrangements: - A minimum of four thermocouples shall be placed such that at least

two are on the weld and the other two on the base material on either side of the weld

within the heating band at 180 degrees apart about 50mm from the weld joint. Two

standby thermocouple shall also be provided on the weld in case of any failure of the

thermocouple.

The width of the heated circumferential band on either side of the weld must be at least

5 times the thickness of the weld. In case of fillet joints the heating band shall be six

times the thickness of the base material. (Ref Fig - 2). An insulation of about 10mm

thickness shall be provided between the cable and weld joint.

5.1 Obtain the clearance for post weld heat treatment cycle from QAE / Welding Engineer.

The PWHT temp for P91 with P91 material shall be 760 + 10°C and the soaking time

shall be 2.5 minutes per mm of weld thickness, subject to a MINIMUM OF TWO

HOURS. All records shall be reviewed by Welding Engineer prior to PWHT clearance.

Heating shall be done by Induction heating only. The rate of heating / cooling: - Thickness upto 60mm - 110°C/ hr.(max)

(Above 350°C) Thickness > 60mm - 55°C/ hr.(max)

Thickness = Actual thickness as measured.

5.2 INSULATION: The width of the insulation band beyond the heating band shall be at

least two times the heating band width on either side of the weldment. The recording

of time & temp shall be continuously monitored with a calibrated recorder right from

preheating. This will be ensured at every one hour by site authorized personnel.

5.3 PREVENTIVE MEASURES DURING POWER FAILURE AND NON-FUNCTIONING OF

EQUIPMENT'S.

No interruption is allowed during welding and PWHT. Hence all the equipment for the

purpose of power supply, welding , heating etc., shall have alternative arrangements.

(diesel generator for providing power to the welding and heating equipments, standby

welding and heating equipments, reserve thermocouple connections, gas burner

arrangement for maintaining temp etc.) Following preventive measures shall be

adopted until normal power supply or backup power supply through diesel generator is

restored :


(a) During start of preheating:

In case of any power failure/interruption during preheating, the weld fit-up shall be

insulated and brought to room temperature. After the electric supply resumes the

joint shall be preheated as per Clause No: 4.1. ( Ref : Fig 3)

(b) During GTAW / SMAW:

Use gas burner arrangement to maintain the temperature at 80 to 100°C upto a

length of 50mm on either side from weld centre line along the complete

circumference of the pipe. Root welding shall be continued after power is restored

and preheating temperature is raised to 220°C. During the above period

temperature shall be recorded through contact type Thermometer. ( Ref : Fig4) (c) During cooling cycle after SMAW welding to holding temperature at 80 to 100°C for

one hour. ( Ref : Fig 5)

Care shall be taken to avoid faster cooling rate by adequate insulation. The required

temp 80 to 100°C shall be maintained by gas burner arrangements till power

resumes / start of PWHT. (d) During post weld heat treatment; The following shall be followed:

*1) During heating cycle

The whole operation to be repeated from the beginning. ( Ref : Fig 6)

*2) During soaking

Heat treat (soak) subsequently for the entire duration. (complete period).

( Ref : Fig 7)

The heating rate shall be as per the chart.

3) During cooling (above 350°C ).

Reheat to soaking temperature and cool at the required rate. ( Ref : Fig 8)

* Temp should not be allowed to fall below 80 to 100°C. Gas burner

arrangement shall be used to maintain the temperature.

5.4 In all the above cases (a to d) the temp. measurement on the weld joint by means of

contact type calibrated temp. Gauges shall be employed to record the temper-ature at

regular Intervals of 15 minutes in the logbook by Quality Assurance Engineer / Welding

Engineer.


5.5 TEMPERATURE MONITORING:

The welding and heat treatment chart given in Figure 9 shall be followed for the

following details. The actual PWHT chart shall be monitored for the following:

a) Preheat

b) Inter pass Temperature (GTAW + SMAW)

c) Controlled cooling and Holding at 80 to 100°C for minimum one hour under

insulation. Start PWHT after minimum one hour of soaking.

d) Heating to PWHT

e) Soaking at PWHT

f) Cooling to 350°C

g) Cooling to Room Temperature (under insulation)

5.6 CAUTION

THE PWHT TEMP. SHALL NOT DEVIATE FROM THE VALUES SPECIFIED IN THE

CHART RANGE SINCE ANY DEVIATIONS TO THE SPECIFIED HOLDING

TEMPERATURE RANGE, WILL ADVERSLY AFFECT THE MECHANICAL

PROPERTIES OF THE WELDMENT AND MAY LEAD TO REJECTION OF THE

WELDMENT. THE WELD JOINTS SHOULD BE KEPT DRY. UNDER NO

CIRCUMSTANCES ANY WATER / LIQUID IS ALLOWED TO COME IN CONTACT ITH

WELD AS WELL AS PREHEATED PORTION OF PIPE.


Insulate 2 Times Heating Band Width fibre glass cloth or

Ceramic woolHeating Band W= 8 X T min

TC2

TC 3TC 4 at 180° apart

ARRANGEMNT FOR POST WELD HEAT TREATMENT

TC5, TC6 ( Spare TC) shall be fixed at 90°, 270° to TC3

Fig - 2

Induction Cable

TC1

or as recommended by theequipment supplier

50mm

50mm


RT

Power Failure during Preheating

220

350

80

Time

100

Temp in deg c

Theoretical curve

Actual curve

After power resumes

RT

Power Failure during GTAW/SMAW

220

350

80

Time

100

During power cut

Theoretical curve Actual curve

After power resumes

Maintain 80 - 100°c by immediate insulation and heating by burners

Temp in deg c

Fig-3

Fig - 4

Immediately cover the joint by insulation, if welding has not been started. Start preheat as per Cl.4.1 after power resumes

POWER CUT


RT

Power Failure during PWHT heating cycle

220

350

80

Time

100

760 ± 10

Temp in deg c

RT

Power Failure during PWHT soaking cycle

220

350

80

Time

100

760 ± 10

Temp in deg c

Theoretical curve

Actual curve

Power cut

T

T1 =T

Actual curve

Theoretical curve

Power cut

T1

Fig - 6

Fig - 7

Rate of heating shall be adhered


RT

Power Failure during PWHT cooling cycle

220

350

80

Time

Tempin deg c

760 ± 10

100

Free fall(While heat insulated)

Actual curve

Theoretical curve

Fig - 8

Rate of cooling shall be adhered

RT

Preheating and PWHT by induction heating

220

350

80

Time

Tempin deg c

1 2 3 4

Sl.No

Temp °cOperation Rate of cooling/Heating

1Preheat 220° C 100 °C/hr

2Welding by GTAW+SMAW 220°C-350°C

3 Cooling 80 - 100 °C 100 °C/hr

4 Holding at 80-100 °C for min 1 hr.Holding shall continue till the start of PWHT

5Heating to PWHT Reach 760 ±10 °C for P91 +

P91

6Soaking at PWHT

760 ± 10 at 2.5minutes /mm( minimum 2 hrs)

7 Cooling Cooling to 350°C

8 Cooling Cooling to Room temperature under insulation

NOTE 1.Purging shall be ensured for minimum root and two further passes of SMAW.2.Ensure removal of all purging dam arrangements after welding..3.For electrodes details strictly follow WPS/EWS.

5

760 ± 10

6 7 8

100

As per clause 5.1

As per clause 5.1

Fig - 9


5.7 CALIBRATION

All equipments like recorder, thermocouple, compensating cable, oven thermostat etc.

should have valid calibration carried at BHEL approved labs. The calibration reports

shall be reviewed and accepted by Calibration In-charge at site prior to use.

6.0 NONDESTRUCTIVE EXAMINATION:

6.1 All NDE shall be done after PWHT only.

Prior to testing all welds shall be smoothly ground. All weld s (fillet & butt) shall be

subjected to MPI (MPI shall be done by YOKE type only). In addition to MPI, butt-

welds and all full penetration welds shall be examined by UT.

LPI procedure shall be BHE: NDT : PB : PT : 01- Rev 11 and

MPI procedure shall be BHE: NDT : PB : MT: 05 - Rev 02

The penetrant materials (Dye Penetrant, Solvent cleaner & Developer) and medium

(dry / wet particles) used in MPI shall be of BHEL approved brands only.

UT procedure shall be as per BHE:NDT:PB: UT21 - Rev 04 with additional

requirements as in (a) through (e)

a) The calibration blocks used shall be of same material specification (P91) dia &

thickness.

b) The UT equipment shall be calibrated prior to use and should be of ‘digital type’

- Krautkramer Model USN 50 of equivalent, capable of storing calibration data

as well as ultrasonic test results as per UT-21 Rev 04.

c) All recordable indications will be stored in memory of either the digital flaw

detector or a PC for review at a later period.

d) The equipment calibration data for specific weld as well as the hard copy of

‘Static echo-trace pattern’ - Showing the flaw-echo amplitude with respect to

DAC, flaw depth, projection surface distance (probe position) and beam-path

shall be attached to UT test report. This hard-copy of echo-trace with

equipment calibration data will form part of test documentation.


e) The examination as well as evaluation will be performed by a qualified Level II

personnel, and a test report will be issued. Any defect noticed during NDT shall

be marked with marker.

7.0 REPAIR OF WELD JOINTS:

(A) WELD REPAIR AT ROOT. On visual examination during root welding if it reveals any surface defects, the same

shall be removed by grinding maintaining temperature 80 - 100°C and rewelded with

GTAW maintaining 220 °C before starting SMAW.

(B) WELD REPAIR ON COMPLETION: Any defect observed on the weld shall be brought to the notice of Quality assurance

engineer. The size and nature of defect shall be reviewed. Any repair on weld to be

carried on their approval only.

If any defects are noticed on the fully completed weld while performing U.T after

completion of PWHT, the same may be assessed in order to find the seriousness of

the defect and to locate where exactly the defect lies from the weld outside surface.

The defect area shall be marked and repaired as below:

a) The weld shall be removed by grinding (gouging not permitted) such that the area

for repair welding is free from sharp corners and provided with sufficient slope

towards the weld face sides. Incase of cut & weld joints HAZ (≅5mm) will have to be

removed by grinding.

b) Surface examination (MPI/LPI) on the ground and welded area to be performed to

ensure a sound base metal before depositing weld layers using SMAW.

c) The temp. of the weld is to be maintained at preheat temp.

d) Carry out SMAW using the same procedure as that of welding.

e) All the specified precautions w.r.t to welding consumables, heating cycles, post

weld heat treatment etc. as followed for original welding, shall be strictly adhered.

f) The NDE shall be conducted for the entire weld joint.

g) If any further defects are observed on the repaired weld, the same may be further

reworked as mentioned above.


8.0 HARDNESS SURVEY The equipment recommended to measure the hardness are EQUOTIP or MICRODUR

make or equivalent portable equipment.

The equipment used for the hardness measurement shall be calibrated as

recommended by the manufacturer and also on a P91 calibration block provided by

PC.

The surface shall be cleaned and prepared as per hardness test instrument

manufacturer’s recommendation prior to hardness survey.

Hardness survey shall be done at each joint at three locations along the circumference.

At each location three readings on weld and parent metal (both pipes) shall be carried

out.

All the hardness values shall be recorded.

The max allowable hardness at weld and parent metal shall be 300 HV10. Joints

having hardness above 300 HV shall be reheat treated and hardness shall be checked

again. If hardness is still more refer to unit.

PM 1 WELD

PM 2 0

270 90

180

Figure - 10

LOCATION PM 1 WELD PM 2

READINGS 1 2 3 AVE 1 2 3 AVE 1 2 3 AVE

0

90

180

270

PM : PARENT MATERIAL AVE : AVERAGE

9.0 COMBINATION WELDING For other combination of material like P22 with P91, and X22 with P91 the applicable

WPS for the involving material shall be obtained from equipment supplier / WTC / PC

and the same shall be used .


9.1 SOAKING TIME FOR COMBINATION WELDING.

WPS N0. Material Temp., Soaking time

1035 P91+P22 745±15°C 2.5mts / mm minimum one hour

MS W0454. P91+X22 750±10°C 2.5mts / mm minimum two hour for thickness

upto 50 mm and minimum four hours for

thickness above 50 mm.

However the precautions as required for P91shall be fully taken care of. 10.0 DEMAGNETISATION

In case magnetisation is noticed on the pipes, the following procedure shall be

followed during welding. Use Residual field-indicator at one end of pipe and measure

the residual field. Note reading and direction of field (+ ve or – ve & No units)

| | | | | | | | | | | | | | | | | | | | |

+10 ↑ 0 -10

Indicator may show readings greater than + or -10 Divisions. A small size electrode or

gem-clip will get attracted & stick to pipe. Wrap insulated welding cable 5 turns-

clockwise on the OD surface or pipe. Wrapped cable to be 50 to 100 mm away from

joint end. One cable end connect to +ve terminal of welding generator and the other to -

ve terminal. Complete electrical circuit & pass 400 amps current for 3 to 4 seconds.

Measure residual field now at the same end of pipe. If demagnetisation is effective the

reading will come closer to `O’ For eg. If it is formerly > + 10 Divisions, it may show -5

Division. The electrode or gem-clip will not stick to pipe-end. If de-magnetisation is

NOT effective The readings will be greater in the same direction The gem clip/electrode

will still stick to pipe, Then repeat the following.

Now wrap the insulated cable (5 turns ) in anti-clockwise direction pass current slightly

excess of 400 Amps Reduce the current gradually to 0 amps in one minute when

current is on. Check for demagnetization using gem-clip / electrode. The gem-clip /

electrode WILL NOT GET attracted. If the reading is shifted to opposite direction,

reverse the turns.


11.0 TRAINING 11.1 The personnel engaged in P91 piping fabrication shall be trained in the following areas. a. Method and Care during fit-up.

b. Argon gas root purging arrangement.

c. Fixing of thermocouple and wires.

d. Arrangements for Pre/Post heating requirements and methods.

e. Adjustment of heating pads/cables at the time of controlling the temperature

within specified tolerance limits during welding or PWHT in case of induction

heating.

f. Good appreciation of the WPS requirements.

g. Handling of P91 welding consumables and re-drying conditions.

h. Special precautions during the power/equipment failure.

i. Weld joints of dissimilar thickness / material specification.

j. Weld defect control and weld repair systems.

11.2 SPECIFIC TRAINING FOR WELDERS

a. The qualified welders who will be engaged in P91 welding shall be given

training on pipe joints simulated with P91 welding and heating cycle conditions.

b. The acquaintance on welding positions, as applicable shall be given using P91

pipes and P91 welding consumables.

c. Welding techniques and instructions on Dos and DON’Ts of P91 welding.

d. Welders only who are qualified on P91 welding alone shall be engaged.

Whenever new welders have to be engaged they shall undergo all the training

as above and shall be qualified with P91 material only.

11.3 CONTROL ON WELDERS

The welder during welding at site follow the following procedures.

The welder shall interact with the HT operator (Induction equipment operator) to

ensure that preheat and interpass temperature during welding are maintained as per

requirements. The welder shall not mix the welding electrodes with that of the other

welder. At the end of the shift, the unused electrodes shall be returned to the stores.

11.4 PERSONNEL / CONTRACTORS ENGAGED FOR HEATING CYCLES (HT Operator)

11.4.1 The Personnel / Contractor shall have adequate heat treat experience on P91 or similar material.


11.4.2 HT operator shall be aware of the following:

a) The equipment used and its working principle and operation.

b) The procedures to be followed in using heating equipments.

c) Procedure to be followed in case of power failure or equipment non-functioning so

that heating cycle is not disrupted.

d) Calibration of equipments.

e) Method of fixing thermocouples and compensating cables leading to HT recorder.

f) Fixing of heating pads or elements on the pipe joints and also in maintaining the

temperature within the specified limits.

11.5 NDE PERSONNEL QUALIFICATIONS

All NDE personnel performing NDT like UT & MPI/LPI shall be qualified in accordance

with BHEL Procedure meeting the requirements of recommended practice SNT-TC- IA.

MPI & LPI shall be carried out be level I qualified personnel and shall be evaluated by

level II qualified personnel. However UT examination and evaluation shall be done by

level II qualified personnel.

11.6 LEVEL OF SUPERVISION

Site Incharge shall be responsible for the completion of all activities from weld fit-up to

final clearance of weld joints after satisfactory NDE and acceptance by BHEL /

Customer / IBR.

12.0 DO’s and DON’T’ s during P 91 welding, heat treatment and NDE at construction site.

12.1 DO’S .

a) Cutting by Band saw/Hack saw/Machining .

b) Pipes Edge Preparation by machining. Machining shall be done without excessive

pressure to prevent heating up of pipe

c) Grinding may be done on exceptional cases after approval and taking adequate care

to prevent overheating.

d) Thermocouple wire (hot/Cold junctions) shall be welded with condenser discharge

portable spot-welding equipment.

e) Reserve Thermocouples shall be made available , incase of failure of connected

thermocouple elements.


f) Ensure adequate Argon Gas for complete purging of air inside the pipe before

starting GTAW root welding.

g) Ensure Preheating at 220°C minimum before GTAW root welding.

h) Start preheating only after clearance from Welding engineer / Quality assurance

engineer for weld fit-up and alignment of the joint as well as fixing of

Thermocouple connections ( for Induction heating)

i) Do visual inspection on root weld maintaining weld preheating temp.

j) Continue Argon purging until the GTAW root welding followed by minimum two filler

passes of SMAW, is completed.

k) Perform partial root welding to facilitate fit-up if necessary.

l) Ensure that only one layer of root welding using TGS 2CM filler wire (2 ¼ Cr 1 Mo) is

deposited. (wherever specified).

m) Ensure proper use of TIG wires as identified by colour coding or suitable hard

punching.

n) Keep the GTAW wires in absolutely clean condition and free from oil , rust, etc.

o) Dry the SMAW electrodes before use.

p) Ensure the interpass temperature is less than 350°C.

q) Hold at 80 to100°C for a period of Minimum 1 hour before the start of PWHT.

r) Record entire heating cycle on Chart through recorders.

s) Exercise control during grinding of weld and adjoining base metal while removing

surface/sub-surface defects or during preparation for NDE.

t) Ensure no contact with moisture during preheat, welding, post heat and PWHT of

Weld Joints.

u) Ensure removal of argon purging arrangements after welding.

v) Use short Arc only. The maximum weaving shall be limited to 1.5 times the dia of

the electrode.

13.0 DON’T’s

a) Avoid Oxy-Acetylene flame cutting.

b) Avoid Weld-build up to correct the weld end-d1 or to set right the lip of the weld bevel.

c) Avoid Arc strike on materials at the time of weld fit up or during welding.

d) Do not Tack weld the Thermocouple wires with Manual Arc/TIG welding.

e) NO GTAW root welding without thorough purging of root area.

f) Do not use Oxy-acetylene flame heating for any heating requirements.


g) Do not use Thermal chalks on the weld groove.

h) Do not stop argon purging till completion of GTAW root welding and two layers of

SMAW.

i) No Tack welding or Bridge piece welding is permitted.

j) Do not use unidentified TIG wires or electrodes.

k) Do not exceed the maximum interpass temperature indicated in WPS.

l) Do not allow moisture, rain, water, cold wind, cold draft etc. to come in contact with

the weld zone or heating zone during the entire cycle from preheat to PWHT.

m) Do not exceed the limits of PWHT soaking temperature.

n) Do not Interrupt the Welding/heating cycle except for unavoidable power failures.

o) Do not use un calibrated equipment for temperature measurement during heating,

welding, post weld, heat treating etc.,

14.0 NDE CONSUMABLES

TECHNICALLY APPROVED BRANDS BY BHEL HPBP.

1) Liquid Penetrant, Penetrant Remover (Solvent cleaner) and Aerosol Developer from

the same manufacturer considered as a family group.

BRAND VENDOR

PENETRANT PENETRANT REMOVER DEVELOPER

ITW SIGNODE INDIA LID., SPOT CHECK SKL-SP

SPOT CHECK SKC-1

SPOT CHECK SKD-S2

P-MET CO.,

FLAW CHECK a) PP-15 b) PP-110

FLAW CHECK a) PP-21 b) PP-120

FLAW CHECK a) PD-31A b) PD-131A

CHECK MATE CHEMICALS (P) LTD.,

CHECK MATE SUPER PT 97

CHECK MATE SUPER CL 96

CHECK MATE SUPER DV 98

PRADEEP METAL TREATMENT CHEMICAL (P)

FLAW GUIDE GP

FLAW GUIDE GP

FLAW GUIDE GP

FERROCHEM

CRACK CHECK FC 911

CRACK CHECK FC 911

CRACK CHECK FC 911


2) Dry Magnetic powder:

(a) MAGNAFLUX - PRODUCT GREY; 8A – RED (b) FERROCHEM PRODUCT NO : 266 (c) K-ELECTRONICS PRODUCT – RD- 200 (SPECIAL)

3) Non-fluorescent magnetic ink: (Prepare bath as instructed by supplier)

(a) MAGNAFLUX – Product 9C RED with MX/MG carrier II oil vehicle.

(b) FERROCHEM – PRODUCT NO : 146 A with oil vehicle (with high flash

point 92°C)

(c) SARDA MAGNA CHECK INK with oil vehicle (with high flash point 92°C)

4) Fluorescent magnetic ink: (Prepare bath as instructed by supplier)

(a) MAGNA FLUX - Product 14A with MX/MG carrier II oil vehicle. (b) MAGNA FLUX - Product 14 AM - Prepared bath of 14A and MG/MX carrier

II ready to use without measuring and Mixing in aerosol container with

MX/MG carrier II oil vehicle.

15.0 DOCUMENTATIONS The documentation shall be as per the customer approved BHEL Quality Plan.


TECHNICAL DIRECTIVE

SHT NO.: 1 OF 2 ARGON PURITY LEVEL

WHAT IS ARGON:

Argon is chemically-inert, monatomic gas, heavy and available in quantity at reasonable

cost. Its chemical symbol is Ar. Atomic weight is 40. Molecular weight is 40.

APPLICATION OF ARGON IN BHEL: In the welding process, Argon is used for SHIELDING and BACKING purpose. The

atmosphere in which we live is composed of about 4/5th of Nitrogen and 1/5th Oxygen.

The welding process when exposed to air, most metals exhibit a strong tendency to

combine with Oxygen, and to lesser extend with Nitrogen, especially when in the molten

condition. The rate of oxide formation will vary with different metals, but even a thin film

of oxide on the surface of metals to be welded can lead to difficulties. For the most part,

the oxides are relatively weak, brittle materials that in no way resemble the metal from

which they are formed. A layer of oxide can easily prevent the joining of two pieces by

welding.

Argon is a shield gas used in Gas Tungsten Arc Welding (GTAW), Root Shielding and

Plasma cutting. Argon protects welds against oxidation as well as reduces fume

emissions during welding.

PRODUCTION OF ARGON : A co-product of oxygen and nitrogen production, argon is manufactured commercially by

means of air separation technology. In a cryogenic process, atmospheric air is

compressed and cooled. Following liquefaction, the air is fractionally distilled based on

the different boiling points of each component. (The boiling point of argon is between

those of nitrogen and oxygen.).

During distillation, liquid nitrogen is the first product extracted from the high-pressure

column. Next, a stream containing oxygen and argon (plus other gases) is withdrawn.

The crude stream, containing approximately 10 percent argon, is refined in a separate

distillation column to produce argon with 98 percent purity.

Manufacturers can further refine the stream by mixing the argon with hydrogen,

catalytically burning the trace oxygen to water, drying and, finally, distilling the stream to

remove remaining hydrogen and nitrogen. Using this process, producers can achieve an

argon product with 99.9995 percent purity.


TECHNICAL DIRECTIVE

SHT NO.: 2 OF 2 ARGON PURITY LEVEL

The compressed argon is supplied in cylinders and liquid argon is supplied in tanks. The

cylinder used for argon will have the body colour of BLUE without band, size of 25 cms dia.

& 1.5 m length, capacity of 6.2 M3 and pressure when fully charged at 150C (approx) 137

Kg/Cm2 (1949 psi).

PURITY LEVEL OF ARGON

INDIAN STANDARD for ARGON, Compressed & Liquid Specification no. IS 5760: 1998

shall be referred.

There are 3 grades of argon, namely:

• Grade 1 : Ultra high purity argon for use in electronics and allied industries

and indirect reading vacuum spectrograph,

• Grade 2 : High purity argon for use in lamp and allied industries and

• Grade 3 : Commercial grade argon for use in welding industry and for other

metallurgical operations.

Accordingly the argon shall comply with the requirements given below:

REQUIREMENT Sl.

No. CHARACTERISTIC Grade 1 Grade 2 Grade 3

i. Oxygen, ppm, Max. 0.5 5.0 10.0 ii. Nitrogen, ppm, Max. 2.0 10.0 300 iii. Hydrogen, ppm, Max. 1.0 2.0 5.0 iv. Water vapours, ppm. Max. 0.5 4.0 7.0 v. Carbon dioxide, ppm, Max. 0.5 0.5 3.0 vi. Carbon monoxide, ppm, Max. 0.5 0.5 2.0 vii. Hydrocarbons, ppm, Max. 0.2 0.5 -

PURCHASE SPECIFICATION FOR ARGON: BHEL - WELDING TECHNOLOGY CENTRE, Trichy recommends the specifications for

purchasing the Argon for welding process is,

“Argon as per Grade 3 of IS-5760: 1998 with Oxygen & Water Vapours restricted to

max. 6 PPM each and with Argon purity level of min. 99.99%. The supply should

accompany Test Certificate for the batch indicating individual element ‘PPM’ level

and overall purity level.”

Hence, it is recommended to purchase the Argon with above specification by BHEL as well

as by our Sub-contractors engaged at sites.

---- O ----


Welding research institute Bharat Heavy Electricals Ltd. Tiruchirappalli-620014

Use of Resistance heating for Post weld heat treatment of P91

pipes.

The subject of the use resistance heating for PWHT has been raised over

the past few years especially for application to P91 steel pipes. In response to this

WRI had taken up extensive studies on the effectiveness of this method in P22, P91

and SA106 Gr.B pipes using the conventionally used continuous coil type heating

method and flexible ceramic pad based resistance heating. The studies were

primarily aimed at evaluation of the effectiveness of the method to achieve close

temperature gradients of the order of ±15°C across the wall thickness of the pipe

during soaking period of Post weld heat treatment. In view of this thermocouples

were attached on the inner walls of the pipe also in this study, though it is not done

in actual situations to enable measurement of temperature gradients at various

stages of PWHT across the wall thickness. The studies were conducted with

different parameters such as heating dimensions, soaking times etc. The study

reveled the following

1. Close temperature gradients up to ±15°C could be achieved across the

circumference of the pipe when an automatic heat treatment is carried out using

Flexible ceramic type pad elements along with Programmable temperature

controller energized by a thyristorised power source that gives an output supply of

65/80V and a digital temperature indicator cum printer is used.

2. This automatic method could be easily used to control the preheat temperature

as well as the inter pass temperature required to be controlled during welding of

P91 steels. The digital printer could give the temperature values along with real time and

were found to be reliable.

3. The conventional method of PWHT using continuous coil type heating method were

found to give higher temperature gradients of the order of ±25°C and required a close

monitoring by skilled personnel to obtain the right results.

Subsequent to this study, a workshop was conducted in Nov 2003 at PSSR chennai

to communicate the results to all construction engineers. Representatives from various

power sector regions attended this workshop. During deliberations, it was felt by all that the

automatic resistance based heat treatment can be applied in one of the 500 MW sites.

Some people opined that prior to the actual use it could be demonstrated in Bellary site as

a next step for implementation of the technique.


In the meanwhile, WRI was recently requested (July 2006) to assist L&T ECC

division to establish the resistance heating method for heating and PWHT of P91 pipes at

SIPAT site for the 660 MW boiler being erected by them. In response to this the same

contractor who was engaged earlier for WRI trials was engaged and a demonstration was

carried out at SIPAT site. The primary aim of this demonstration was to demonstrate the

effectiveness of the automatic method to get temperature gradients to levels of ±15°C in

P91 pipes up to 30 mm thickness. In tune with this two trials were conducted at site. The

first pipe was a P91 pipe with 25 mm thickness in which the entire preheating, interpass

temperature control and during welding and PWHT cycle was applied. The welded pipe

was also subjected to procedure qualification tests at WRI. Secondly one more pipe of 45

mm thickness was also tried to study the effectiveness of the method with thermal cycle

simulation only without welding. The results of the above study reveal the following

1. Temperature gradients within 8-10°C could be obtained between the outer and inner

walls with the automatic resistance heating method.

2. The temperature chart showed that no interruptions or kinks in the time-temperature

record indicating the steady maintenance of temperature throughout the PWHT cycle.

3. The method could be effectively used for the entire heating cycle, including

preheating, interpass temperature control during welding, cooling to intermediate

temperature and regular PWHT cycle.

4. Similar results were observed in the case of 45 mm thick pipe also and the results

were highly reliable.

5. The trials at WRI shop as well as SIPAT site has given good and satisfactory results

indicating that the automatic local PWHT is more reliable, consistent and can be applied in

site with ease.

In view of the above it can be concluded that the automatic resistance based heating method can be used for the entire heating cycle for welding P91 grade pipes up to 32 mm to achieve temperature gradients of the order of ±10°C which is required as per specification. The details of the various components of the automatic resistance heating equipment and system that are to be used in are given in Annex I. The contact address of the contractor through whom the trials were carried out is given in annex II.

Besides this, some more contractors have also shown interest in carrying out the PWHT in the automatic mode. Their addresses are also given in annex II. As the entire set of equipments is made indigenously many contractors would come up with the automatic heating facilities when BHEL specifies the usage of this method.

In this context it is recommended to carry out Procedure qualification test with the largest thickness pipe at site to establish the process with the contractors prior to application for the actual pipe. This would enable the contractors to stabilize the process and serve as a measure of quality assurance for site heat treatment.


Annex I

Details of the automatic resistance heating based equipment recommended for PWHT.

Sl.no Key components of the

equipment

Description of the items that are essential

01 Type of heating element Flexible ceramic pads containing stranded heating elements of standard width and breadths to cover various diameters of pipes. The pads can be of 2.7/3.6 kW power with 65/80V

02 Power supply Power source: 50/70 KvA transformer power source with 3 phase input supply with 415 / 440 V, 50 Hz supply to provide a secondary output voltage of 65/85V and 225 Amps per phase. 6 way thyristorised switching, energy regulators.

03 Controller Microprocessor based Programmable cycle controller (0-1200°C) with easy setting of time and temperature for setting heating/soaking and cooling rates.

04 Temperature recorder Calibrated Digital multi point recorder (12 channel- 0 to 1200°C) cum printer with suitable connecting cable for real time recording temperature with time for the entire heating cycle.

05 Power cables Suitable plug in type copper cables, 2/3/4 way splitter cables to connect heating pads and power source. Suitable temperature compensating cables to connect thermocouples and Power source and temperature recorder

06 Accessories 1. Capacitor discharge based Thermocouple fixing unit.

2. Calibrated thermocouples (type K). 3. Mineral wool /ceramic wool Insulation pads of

min 25 mm thick for insulation of the pipe. 4. Steel banding machine with 1” thick steel band

for securing the heating pads with the pipe.


Annex II

List of vendors /contractors who can carry out the automatic local PWHT at site

VENDOR USED FOR THE STUDY AT WRI AND AT SIPAT SITE

01 Mr. Fernandez Indo therm engineers Pvt.Ltd Plot No. A-374, Road No. 9 Wagle Industrial Estate Thane –400 504

Phone 25822175,25830410,25805563, 25831948 Fax: 022- 25833882 Cell no: 9892592329 Email: [email protected]

VENDORS WHO ARE READY TO OFFER PWHT SERVICES WITH AUTO

EQUIPMENTS

02 K.B. Jetly East West Engineering & electronics company 204, Acharya complex center Dr. C. Gidwani road Chembur, Mumbai 400 074

022 - 556 7654/ 5581766/556 6096 [email protected]

03 Shri .V. Kannan Shastra NDT services 131,Aharya commercial center Near Basant Cinema Dr.C.G.Road Chembur Mumbai –400 074

Ph: 022- 5575 1279 [email protected] Mobile: 98213 29436

04 Injo tech services Office No. 44, 5th floor Yugay Mangal complex Near ICICI bank, Erandwane Pune 411 038

Mr. Ingale 020-5621 2833, 5621 6833 Mobile of Mr. Ingale: 09822036600 [email protected]

05 OPI services, Pune

Mr. Sathe Cell: 9822499002

WELDING MANUAL B-3 GENERAL TOLERANCES FOR WELDING STRUCTURES – (FORM AND POSITION) 127

CHAPTER - B3

GENERAL TOLERANCES FOR WELDING STRUCTURES – (FORM AND POSITION)


Doc. Ref.: AA 0621105 B3. GENERAL TOLERANCES FOR WELDED STRUCTURES -

(FORM AND POSITION)

1.0 GENERAL : 1.1 Tolerance on form and position as defined in this standard are permissible variations

from the geometrically ideal form and position corresponding to the accuracies

commonly obtained in workshops. The standard covers tolerances on straightness,

flatness and parallelism.

1.2 This standard is based on DIN 8570 Part 3 - 1987 1.3 General tolerances for machined components are covered in corporate standard

AA 023 02 08.

1.4 Refer Corporate Standard AA 062 11 04 for general tolerances for lengths and angles

of welded components, assemblies and structures.

2.0 SCOPE : 2.1 This standard prescribes four degrees of accuracies taking into account the function

dependent and the fabrication dependent differences along with appearance aspects

of welded components, assemblies and structures.

2.2 For technical and economic reasons other degrees of accuracy may be appropriate

which have to be specifically stated.

3.0 DEVIATIONS : 3.1 The values of deviations for different classes of accuracies of straightness, flatness and

parallelism are given in Table-1. These values apply to overall dimension and to part

lengths.

4.0 REPRESENTATION ON DRAWING : 4.1 The required degree of accuracy shall be specified in all fabrication drawings. For

example Class E of AA 062 11 05 (DIN 8570 Part 3).

TABLE 1 : TOLERANCES ON STRAIGHTNESS, FLATNESS AND PARALLELISM

Nominal Dimension Range (larger side length of surface) - mm Grade

of accu-racy

Above 30 to 120

Above 120 to 315

Above 315 to 1000

Above 1000

to 2000

Above 2000

to 4000

Above 4000

to 8000

Above 8000

to 12000

Above 12000

to 16000

Above 16000

to 20000

Above 20000

E 0.5 1 1.5 2 3 4 5 6 7 8 F 1 1.5 3 4.5 6 8 10 12 14 16 G 1.5 3 5.5 9 11 16 20 22 25 25 H 2.5 5 9 14 18 26 32 36 40 40


5.0 TESTING : 5.1 Figures 1 to 3 illustrate the mode of testing for straightness, flatness and parallelism.

The test method should be selected on the basis of current measuring practice.

There should be no unusual temperature or weather conditions, e.g. strong sunshine.

The measured values apply to the conditions on the day of testing.

5.2 STRAIGHTNESS :

The edge of the welded component and the straight edge can be arranged in relation to

each other so that the end points of the measured length are the same distance apart

from the ends of the straight edge. The distances between the edge and the straight

edge should be measured.

5.3 FLATNESS :

A measuring plane can be set up outside the welded component parallel to the limiting

planes at any desired distance. For example this can be done with optical instruments,

flexible tube liquid levels, tension wires, clamp plates, surface plates and machine

beds.

5.4 PARALLELISM :

Any of the measuring devices mentioned above can be used to set up a measuring

plane outside the welded component parallel to its reference plane. The distance

from the actual surface to the measuring plane is measured.

The position of the reference surface (= surface after machining) is dimensionally

determined.

Dimension a1 gives the required finished height of the foundation. Dimension a2 gives

the minimum thickness of the support.

The distance between the reference plane and the measuring plane is greater than :

hmax by the minimum possible thickness of the machining allowance “b”. The variation

of the actual surface (=surface before machining) from the reference plane must be

within the tolerance on parallelism. Maximum variation is

hmax - hmin ≤ t

Note : The tolerance on form and position as per this standard may be mentioned on

the drawing in addition to the linear tolerances as per AA 062 11 04 wherever required.

WELDING MANUAL B-4 WELDING OF PIPES AND PIPES SHAPED CONNECTIONS IN STEAM TURBINE, TURBO-GENERATORS AND AUXILIARIES 131

CHAPTER - B4

WELDING OF PIPES AND PIPES SHAPED CONNECTIONS IN STEAM TURBINE, TURBO-GENERATORS AND AUXILIARIES


Doc.Ref.: HW 0620599 B4. WELDING OF PIPES AND PIPE SHAPED CONNECTIONS IN

STEAM TURBINE, TURBO-GENERATOR AND HEAT EXCHANGERS 1.0 SCOPE :

These guidelines cover edge preparation, method of welding for pipes and pipe shaped connections to be used in Steam Turbine, Turbo-generator and heat exchanger of KWU design.

2.0 WELD EDGE PREPARATION : 2.1 Various forms of edge preparation to be used for shop weld, site weld and edge

preparations for pipes manufactured from rolled plates are covered in this standard. 2.2 However, edge preparation may be altered in case where pipe connections are

made between customer’s pipe line and BHEL supply. In all such cases edge preparation must be given on the drawing.

3.0 ASSEMBLY AND WELDING PROCEDURES : 3.1 Before tacking the weld edges must be aligned. The linear misalignment between

weld edges must be maintained according to specifications No. HW 0620099. 3.2 Machined weld end preparations of the components being despatched to site must

be protected with a metal cover. 3.3 Shaped parts of piping e.g. flanges, reducer, elbows, T-sections etc. are ordered

with edge preparations carried out at supplier’s work. 3.4 Welding processes are selected in accordance with Annexure-I. 3.5 Welders qualified as per ASME Section IX are to be employed. 3.6 The distinction is to be made between shop and site welds in the drawing as per

Plant Standard No. 0623.003. 3.7 Tack welds, if not to be removed, must be made with the same filler metal and must

be performed by qualified welder. 3.8 The weld joints are to be purged by inert gas in case of high alloy steels.

4.0 PIPES ROLLED FROM PLATES : 4.1 Weld seams of rolled pipe are welded by Shielded Metal Arc welding. The root is

gouged / ground and welded from back side.

5.0 INSPECTION : 5.1 The weld seams are subjected to internal examination in accordance with HW

0850199. The external characteristics are examined in accordance with HW 0620099.


ANNEXURE-I

NECK WELDING 134

CHAPTER - B5

INSTRUCTIONS FOR CARRYING OUT CONDENSER PLATE AND NECK WELDING

NECK WELDING 135

B5. INSTRUCTIONS FOR CARRYING OUT CONDENSER PLATE

AND NECK WELDING

1.1 GENERAL: 1.1.1 The welding of the condenser is performed by ‘step back seam method’ i.e. from tack

weld to tack weld.

1.1.2 Subsequent filling welds after tack welding are always performed in the opposite

direction. Welding to be carried out as per requirement envisaged in drawing / field

welding schedule.

1.1.3 Condenser Erection Manual as well as instructions issued by manufacturing unit may

also be referred in conjunction with this manual.

1.1.4 All the welding shall be carried out by qualified welders.

1.2 CONDENSER SHELL INTERNALS WELDING: 1.2.1 Tack weld the tube support plate sections aligned with the centre point to the slot

profiles on the bottom plate and the side walls. After tack welding, verify that the holes

in the support plates lie in the vertical and horizontal planes. Enter the actual

measurements on the measurement data record provided.

The thin steel wires and alignment devices can now be removed, as they are no longer

required for further assembly of the condenser shell internals.

Move the internals temporarily housed in the spaces in the tube support plate sections

into their correct positions, align and tack weld them in accordance with the plant-

specific drawing. Assemble the central fishing and the bracing assemblies such as flat

irons and tubes.

NOTE:The steam baffles and bracing units must not be tacked to the tube plates of the

water boxes. This operation is not performed until all internals have been

welded to one another.

Then align the various sections of the air extraction line, weld them together to form

one unit and tack weld to the tube support plates.

During alignment, ensure that the air extraction openings are directed towards the

bottom plate and that therefore the connection holes for the connecting piping systems

are necessarily in the correct positions. Pass out and fit the pipe work to the connecting

piping system through the connection holes. Assemble the shields for the cooler tube

nests. Set down the shields on the flat iron supports, align and tack weld.

NECK WELDING 136

After assembly of all the steam space internals which, to allow for welding warpage,

may only be tack-welded, commence welding of all the condenser shell internals, the

welding sequence being of up most importance.

NOTE: The feed water heater platform must be mounted and welded in place prior to

the assembly of the condensate drain sheets as there is only a gap of

approximately 200 mm between the feed water heater platform and the air

cooler sheet.

Then weld the vertical slot profile strips to the side walls and tube support plates.

During this procedure, welders should as far as possible work simultaneously.

When the condenser shell internals have been completely welded together, tack and

weld the steam baffle plates, the bracing assemblies and the air extraction line and the

connecting piping system at the front and rear tube plates. When all welding work has

been concluded, remove all weld residue from the weld seams and weld zones in the

entire condenser shell.

NOTE:To prevent welding warpage, all welds must be performed simultaneously from

both sides using the back-step method. Vertical joints must be welded from top

to bottom, i.e. from the upper edge of the tube support plate to the bottom plate.

ATTENTION:- THE PERTINENT WELDING PROCEDURE SPECIFICATION AND

WELDING INSTRUCTIONS MUST BE OBSERVED WHEN WELDING.

1. Steam space (top view)

2. Tube support plate

3. Vertical slot profiles

4. Welding locations

NECK WELDING 137

1.3 WELD CONNECTIONS BETWEEN CONDENSER AND LOW PRESSURE TURBINE

NOTE :- The assembly welding instructions given herein are of a general nature.

Please see also the assembly plans, drawings and other instructions for the

plant in question.

1.3.1 In any weld connection, the cooling of the locally heated material in the weld zone will,

by laws of physics cause transverse and longitudinal contractions, these giving rise to

stresses in the material.

In order to keep these stresses as low as possible, it is imperative that the weld is

prepared as specified in the drawings. Before welding is commenced the semi-circular

structural profiles must be bolted to the dome end walls.

1.3.2 WELDING THE CONDENSER TO THE LOW-PRESSURE TURBINE

After the condenser has been brought to operating weight and the spring supports have

been adjusted to compensate for welding contraction, prepare for welding the

condenser to the low-pressure turbine.

Erect scaffolding inside the condenser in accordance with applicable accident

prevention regulations to facilitate access to the weld locations. Then fit the

intermediate, corner and web plates (as called for) and prepare the weld edges. Tack

these parts to the condenser dome with welds with a tack length of three times the

plate thickness at intervals of 25 times the plate thickness.

Weld the joint using the back-step method from tack to tack (see Fig.1). When the base

layer has been completed, make the following filler weld layers, each in a single pass,

and reversing direction for each layer (see Fig.2). After welding, clean the weld zone

using suitable tools.

ATTENTION:- THE PERTINENT WELDING PROCEDURE SPECIFICATION AND

WELDING INSTRUCTIONS MUST BE OBSERVED WHEN WELDING.

STRENGTH WELDS ON TUBE TO TUBE 138

CHAPTER - B6

REPAIR PROCEDURE FOR ARRESTING THE LEAKAGE OF STRENGTH WELDS ON TUBE TO TUBE SHEET JOINTS OF ‘U’

TUBE H.P. HEATER


B6. REPAIR PROCEDURE FOR ARRESTING THE LEAKAGE OF STRENGTH WELDS ON

TUBE TO TUBE SHEET JOINTS OF ‘U’ TUBE H.P. HEATER

1.1 Pressurise the shell side with Nitrogen or Pneumatic air to 7 Kg / cm2 and apply soap

solution over the complete area of welding on tube sheet.

1.2 Find out the leakage of tubes and identify by marking either with chalk or colour.

1.3 Reduce the pressure to zero and also ensure the removal of Nitrogen from the shell.

1.4 Face the defective weld as identified earlier by using face cutter and ensure the

elimination of defect by dye penetrant (LPI) test.

1.5 If found satisfactory, clean the penetrant thoroughly and weld with manual TIG using the

specific WPS according to Tube sheet material and tubes.

1.6 After welding test the weld by dye penetrant and ensure the sound weld metal

deposition.

1.7 Pressurise the shell side again to 7 Kg / cm2 with Nitrogen or Pneumatic air and test the

soundness of welds.

1.8 Plugging of tube of ‘U’ tube HP Heater on weld overlayed tube sheets.

This procedure explains the method of plugging of tubes on overlayed tube sheets of :

1. Carbon steel tubes on inconel weld overlayed tube sheets.

2. Inconel tubes to inconel weld overlayed tube sheets

3. Carbon steel tubes on stainless steel overlayed tube sheets.

4. Stainless steel tubes on Stainless steel overlayed tube sheets.

Procedure :

1. Face the tube end (to be plugged) such that the face of the tube is 4 mm below the

surface of the tube sheet using the facing cutter as shown in sketch.

2. Clean the hole inside thoroughly with the solvent. 3. Prepare the plug made of either SA 105 or 11416.1 to a length of 38 mm as shown in

sketch such that the OD of plug is machined for the interference fit with the tube hole

i.e. tight fit having plug F 0.05 mm less than the actual inside F of tube as shown in

sketch.


4. Fit tightly the plug inside the hole as shown in sketch and weld by GTAW (manual)

using the suitable filler rod.

5. Inspect the soundness of weld after each layer by dye penetrant. 6. After completing the weld pressurise the shell to the operating pressure and then

inspect the weld by dye penetrant.

TUBE PLUG PROCEDURE

SKETCH

CHAPTER - B7

REPAIR PROCEDURE FOR GREY CAST IRON CASTINGS

B7. REPAIR PROCEDURE FOR GREY CAST IRON CASTINGS 1.0 SCOPE 1.1 This quality control procedure is valid for the repair of grey cast iron castings covering

the following specifications :

IS 210 Gr. 20 & Gr. 25

1.2 Defective castings can be salvaged by sound welding practices provided the defects

are accessible to repair are not extensive and are economical to reclaim by welding.

Where repairs are carried out on pressure retaining areas special care should be

exercised to ensure sound weld repair.

2.0 DEFECTS THAT DO NOT REQUIRE WELD REPAIRS : 2.1 Machinable surfaces :

Foundry defects can be left without weld repairs on Machinable areas provided the

depth of such defect is less than 50% of the machining allowance provided. Defects

revealed during machining shall undergo weld repairs. Isolated pores or sand

inclusions of size < 3 mm and separated from one another by atleast 25 mm can be left

without weld repairs.

2.2 Non-Machinable surfaces :

Foundry defects other than cracks, cold shuts, shrinkage etc. can be dressed smooth

by grinding provided the depth of such defect is < 5 % of the specified wall thickness,

and size < 10 mm, separated from one another by atleast 100 mm.

3.0 PREPARATION OF SURFACE : 3.1 The surface around the defective area shall be free from foreign materials such as oil,

grease, paint, rust, sand etc.

3.2 The defective area shall be ground or machined to obtain a sound base for welding. In

the case of surface defects, the skin should be similarly ground or machined.

3.3 Before starting weld repair free graphite shall be removed by flame heating and

cleaned with a wire brush.

3.4 Depending upon the size of the defect, shallow or deep grooves shall be formed by

grinding / machining.

3.5 Where defects are located in relatively inaccessible positions, sufficient material shall

be removed to permit a satisfactory welding operation.

4.0 ELECTRODES :

Low heat nickel iron electrodes (ENiFe-CI and ENi CI type) should be used. The following brands are recommended for repairs : 1.Philips 802, 2. Xyron 2.23, 3. Super Nicron, Fon E119, 4. NFM. Any other equivalent approved by BHEL may also be used.

5.0 WELDING PROCEDURE : 5.1 To ensure maximum freedom from porosity in weld deposits, nickel iron electrodes

should be re-baked for atleast one hour at 260°C in a well ventilated electric oven and

either used immediately or stored in a similar oven at 120°C until used.

5.2 The welding current should be kept as slow as possible consistent with smooth

operation and a good wash at the sides of the joint.

5.3 Wherever possible the casting should be positioned for down hand welding operation.

When extra long welds or several repair positions are involved it is preferable to

stagger the welding operation to distribute the heat and to minimise the distortion.

5.4 Manipulation of the electrode :

It is preferable to use stringer bead technique, with beads not > 50 to 75 mm in length,

slight weaving of the electrode may be done to obtain better wash, but in no case the

width of the deposit should be > 3 times the nominal dia. of the electrode.

5.5 It is preferred to butter the surface of the weld preparation first and then fill gradually

towards the centre of the repaired area.

3.8 It is essential to clean the slag from each crater before making a re-strike and to remove it

completely from each weld run before depositing the adjacent weld.

5.7 To ensure maximum weld soundness the forward movement of the electrode tip should

be accelerated as the end of the weld run is approached, this will taper the run rather

than ending it abruptly in a large weld pool. When re-striking the arc should be started

ahead of the previous weld run, move back over the tapered portion, then continued

forward.

The defective zone must be adequately prepared to permit correct manipulation of the

electrode.

6.0 PREHEATING : 6.1 Preheating is normally not required. Where preheating is resorted to, the entire casting

should be preheated. Interpass temperature should not exceed 250°C.

6.2 It is advisable to cool as slowly as possible after welding although in most cases, it is

sufficient merely to cool under a cover of heat insulating material such as asbestos,

sand or ashes.

6.1 Peening of the weldment after the weld cools down may be done to reduce the

shrinkage stresses.

7.0 WORKMANSHIP :

The weld profile should perfectly merge with the contour of the casting and shall be free

from spatter, slag etc.

8.0 INSPECTION :

In addition to visual examination, non-destructive tests like liquid penetrant inspection

might be employed on repaired areas to ensure freedom from cracks.

CHAPTER - B8

SPECIAL INSTRUCTIONS FOR THE REPAIR OF STEAM TURBINE CASINGS

B8. SPECIAL INSTRUCTIONS FOR THE REPAIR OF STEAM TURBINE CASINGS

Note : These instructions are only guidelines. Specific written approval is to be taken

from the Manufacturing units prior to carrying out repair works.

1.0 GENERAL INSTRUCTIONS : 1.1 This instruction is valid for the repair of steam turbine castings by welding. The

materials for which this instruction is applicable are: CSN 422643, 422710, 422743,

422744, 422745, GS17CrMo55, GS C 25, SA216WCB, GS 17CrMoV511,

21CrMoV57V, 21Cr.MoV57.

1.2 The repair by welding may be carried out only by qualified welder having enough

experience in this line.

1.3 The castings of casings supposed to be repaired by welding must be in the heat treated

state specified in the respective drawing. It is forbidden to carry out any repair by

welding on castings which were not annealed or subjected to the prescribed heat

treatment.

2.0 DECISION ON REPAIR : 2.1 No repair must be carried out without the approval of the manufacturing unit. 2.2 The manufacturing department takes the decision about the repair based on a strict

visual and defectoscopic examination taking into consideration the type and size of the

defect and its location with regard to the possibility of repair. No repair must be

undertaken, would it endanger the proper operation and safety of the equipment.

3.0 EXECUTING THE REPAIR : 3.1 The defects in castings ascertained by the manufacturing unit, must be chipped off or

ground out or drilled out in such a way as to obtain a clean metallic surface. Gouging

by flame or arc - air method is permissible only with non alloyed cast steel like CSN

422643. Even then the gouged portion must be ground in order to obtain a metallic

surface. In case of doubts whether the defect has been completely removed or not, the

electro-magnetic crack test must be applied.

3.2 The defective portions must be removed in such a way as to enable the welder to carry

out the welding successfully. There must be no sharp edges and the transition from the

defective portion to the faultless material must be done in a smooth way. The welding

engineer has to certify whether the preparation has been carried out properly.

3.3 The exact procedure of welding different types of cast steels can be found in the

enclosure of this instruction.

3.4 In case cracks develop during welding, the welder is obliged to stop the welding

operation and call the welding engineer immediately who will instruct the welder how to

proceed further on.

3.5 If preheating for welding is prescribed, it is recommended to heat the whole casting

upto the required temperature. The preheating temperature has to be maintained

through out the welding operation. Heating by means of heating fixtures (producer gas)

is permissible. It is essential to protect the casting during welding against any sudden

cooling which could cause the increase of inner stresses. The surface exposed to the

atmosphere should be covered by suitable insulating materials (asbestos mats, glass

wool etc.). The temperature of preheating is being checked during welding by means

of suitable temperature indicating aids like thermo-chalks etc. If the preheating

temperature falls during welding below the minimum required value, welding must be

interrupted and the temperature regained.

3.6 Welding must proceed without any interruption. In case welding is interrupted for any

unexpected reason the casting must not cool down fast but must be heated by gas

burners in order to cool down slowly to the room temperature. The same procedure

has to be followed when concluding the welding operation.

3.7 In case of large welds intermediate annealing has to be carried out according to the

enclosure of this instruction.

4.0 INSPECTION OF THE REPAIR : 4.1 All major repairs done on casing by welding must be recorded. The manufacturing unit

/ inspection department is obliged to keep these records (including a sketch about the

location of the defect). Only small repairs like local porosity need not be recorded.

4.2 The welds shall be inspected visually. Larger repairs shall always be inspected by

applying defectoscopic methods. The weld must be homogenous without any cracks.

4.3 Defects found in the weld must be again repaired following the same procedure as

stated above.

5.0 HEAT TREATMENT : 5.1 The repaired and inspected castings must be again heat treated. The type of heat

treatment will be given by the welding engineering department from case to case.

6.0 RESPONSIBILITY : 6.1 The manufacturing unit is responsible for :

a) The exact determination of the repair to be carried out on the casing. b) Ascertaining that the found defects were nicely removed. c) Inspection of the executed repair. d) Record keeping on repairs.

6.2 The welding engineering department / manufacturing unit is responsible for :

a) Certifying that the places on which welding is supposed to be done are properly

prepared for undertaking the repair. b) Follow up of welding procedure specification. c) Supervision of the welding operation. d) Ascertaining that the preheating temperature has been reached if prescribed. e) Cooperating with the manufacturing unit when evaluating the result of the

welding operation. f) Prescribing the necessary heat treatment after welding if required.

7.0 REPAIR WELDING PROCEDURE

1 Material specification : GS-C25, 422710, 422643, SA 216 WCB

2 Removal of defects : Defects shall be removed by grinding /

machining.

3 Inspection of pre-welding : Complete elimination of defects shall

be ensured by LPI / MPI /

Radiography.

4 Welding procedure : a) Welder : Qualified as per ASME Sec.IX / IBR b) Process : SMAW c) Electrode : E7018-A1. Properly baked electrodes

to be used.

d) Position : The welding shall be done in the flat

position as far as possible.

e) Arc current : F 2.50 mm (60-80 amps) F 3.15 mm (90-130 amps) F 4.00 mm (140-180 amps) F 5.00 mm (190-240 amps) f) Preheating : Upto 30 mm thickness } 10ºC 30-100 mm thickness } 100ºC 101-200 mm thickness } 150ºC g) Inter pass temperature : 350ºC max. 5 Stress relief : Below 40 mm thickness no stress

relief is required.

Above 40-200 mm thickness stress

relieve at 600-620ºC for 3 hours.

6 Inspection of Post welding : MPI followed by UT.


1 Material specification : GS-17CrMoV511, 21CrMoV57V,

21CrMoV57, 422731.1, 422743.1,

422744.1, 422745.1

2 Removal of defects : Defects shall be removed by grinding

or machining and ensure complete

removal by LPI / MPI.

3 Welding procedure : a) Welder : Qualified as per ASME Sec.IX / IBR b) Process : SMAW c) Electrode : E9018B3. Properly baked electrodes

to be used.

d) Arc current : F 2.50 mm (60-80 amps) F 3.15 mm (90-130 amps) F 4.00 mm (140-180 amps) F 5.00 mm (190-240 amps) e) Preheating : 300ºC, continue this temp. throughout

the welding operation.

f) Inter pass temperature : 375ºC max.

5 Post weld heat treatment : The casing has to be stress relieved

as per code of practice in welding

procedure specification.

6 Inspection after Post weld heat treatment : MPI followed by UT.


1 Material specification : GS-17CrMo55(P4), A182F12,

A217WC6, A387-12

2 Removal of defects : Defects shall be removed by grinding

or machining and ensure complete

removal by LPI.

3 Welding procedure : a) Welder : Qualified as per ASME Sec.IX b) Electrode : E8018B2. Properly baked electrodes

to be used.

d) Arc current : F 4.00 mm (140-180 amps) F 5.00 mm (190-240 amps) e) Preheating : 250ºC, maintain this temp. throughout

the welding operation.

f) Inter pass temperature : 350ºC max. 5 Post weld heat treatment : Maintain the temp. at 300ºC for about

2-3 hours and allow it to cool under

asbestos.

6 Inspection after Post weld heat treatment : MPI followed by UT. Note : If weld repair is extensive, i.e. thickness of weld metal is more than 10 mm,

the casing has to be stress relieved as per the code of practice.

CHAPTER - B9

GAS METAL ARC WELDING

B9. GAS METAL ARC WELDING

1. GENERAL

Gas Metal Arc Welding (GMAW) can be used as a faster alternative to Shielded Metal Arc

Welding (SMAW) . In GMAW the consumable is a wire spool, which is continuously fed by

a motor. This consumable as well as the shielding gas come out through a hand held torch

and the torch is moved manually.

This method thus combines the flexibility of manual methods with the high productivity of

motorised consumable wire movement. The method has two commonly used variants :

(a) Metal Inert Gas (MIG) welding (an example is the welding of aluminium bus

ducts at site)

(b) Metal Active Gas (MAG) welding (an example is steel chimney fabrication at

site)

While Argon is almost always used in MIG welding for shielding the arc, Carbon Dioxide or

Carbon Dioxide with Argon is used for MAG welding.

2. ADVANTAGES OF GMAW The advantages of GMAW over SMAW are :

(a) High welding speed due to continuous feed of filler metal and high deposition rate

(b) No slag removal and no slag inclusion

(c) Higher deposition efficiency

(d) Higher arcing time

(e) Low hydrogen content in weld metal

3. VARIABLES AFFECTING WELD QUALITY THE VARIABLES WHICH AFFECT WELD QUALITY IN GMAW ARE:

(a) Welding current

(b) Polarity

(c) Arc Voltage

(d) Travel speed

(e) Electrode extension

(f) Weld joint position

(g) Electrode diameter

(h) Shielding gas composition

(i) Gas flow rate

The optimum process variables, however, depend on type of base metal, electrode

composition, welding position and the specified quality requirements.

Some suggestive areas where this process can be used to great advantages are CW

piping, Power House Structurals, Ceiling Girders, Condenser etc.

The relevant information from welding techniques and welding procedure data used in one

of the BHEL sites in construction of steel chimney is given below for guidance.

If site wants to adopt GMAW process, procedure may be developed at site and get it vetted

by respective Engineering centres / Manufacturing units.

WELDING TECHNIQUES Joint details : 8mm 8 mm Fillet 8 mm

Current range : 120 to 160 Amps Voltage range : 19 to 22 Volts Electrode consumed (cm / M) : 3 to 3.8 M / Min. Current AC or DC : DC Polarity : EP Size of reinforcement : 1.5 to 2 mm Whether removed : No Inspection and test schedules : As per IS 7307 PT-1

WELDING PROCEDURE DATA SHEET Welding Process : Semi-Auto Material specification : IS 2062 Gr.A Thickness Plate : 8 mm Pipe diameter : -- Filler metal specification : IS-6419 84-C504 (ER-7086) Weld metal analysis : NA

FLUX OR SHIELDING GAS Flux trade Name or composition : NA Shielding gas composition : 99.7% CO2 Trade Name : NA Flow rate : 10-15 LPM Backing strip used : NA Pre-heat temperature range : 10°C Min. Interpass temperature range : 265°C Max. Post Weld Heat Treatment : NA

WELDING PROCEDURE Single or Multi-pass : Multi-pass Single or Multiple Arc : Single Welding position(s) : Horizontal – Vertical

FOR INFORMATION ONLY Electrode and filler wire diameter : 1.2 mm Trade Name : CTTOFIL(ADVANI) Type of backing : NA Fore hand and back hand : NA

CHAPTER - B 10

ORBITAL WELDING

WHAT IS ORBITAL WELDING 1. Definition The term Orbital-Welding is based on the Latin word ORBIS = circle. This has been

adopted primarily by aerospace and used in terms of Orbit (n.) or Orbital (adj.) for the

trajectory of a man-made or natural satellite or around a celestial body.

The combination Orbital and Welding specifies a process by which an arc travels

circumferentially around a work piece (usually a tube or pipe).

The concept Orbital Welding is basically a loosely defined term that is usually used for

process only, where the arc travels at least 360 degrees around the work piece without

interruption.

Consequently, processes, which interrupt the full 360-weld sequence such as for better

puddle control (often used for MIG/MAG welding, using the down-hand welding sequence

in 2 half-circles), can not truly be called orbital welding.

Orbital Tube Welding

Understanding the basic principles behind orbital tube welding may help you arrive more

rapidly at the optimum weld procedure for your specific application.

by Bernard Mannion and Jack Heinzmann III

Orbital welding was first used in the 1960s, when the aerospace industry recognized the

need for a superior joining technique for aerospace hydraulic lines. A mechanism was

developed in which the arc from a Tungsten electrode was rotated around the tubing weld

joint. The arc welding current was regulated with a control system thus automating the

entire process. The result was a more precision and reliable method than the manual

welding method it replaced.

In the early 1980s, Orbital welding became practical for many industries when combination

power supply/control systems were developed that operated from 110 VAC. These

systems were physically small enough to be carried from place-to-place on a construction

site for multiple in-place welds

Modern day orbital welding systems offer computer control, where welding parameters for

a variety of applications can be stored in memory and later called up for a specific

application. Hence, the skills of a certified welder are thus built into the welding system,

producing enormous numbers of identical welds and leaving significantly less room for

error or defects.

Orbital Welding Equipment

In the orbital welding process, tubes/pipes are clamped in place, and an orbital weldhead

rotates an electrode and electric arc around the weld joint to make the required weld. An

orbital welding system consists of a power supply and an orbital weldhead.

The power supply/control system supplies and controls the welding parameters according

to the specific weld program created or recalled from memory. This supply provides the

control parameters, the arc welding current, the power to drive the motor in the weldhead,

and switches the shield gas(es) on/off as necessary.

Orbital weld heads are normally of the enclosed type, and provide an inert atmosphere

chamber that surrounds the weld joint. Standard enclosed orbital weld heads are practical

in welding tube sizes from 1/16 inch (1.6 mm) to 6 inches (152 mm) with wall thicknesses

of up to .154 inches (3.9 mm). Larger diameters and wall thicknesses can be

accommodated with open style weld heads.

Reasons for Using Orbital Welding Equipment

There are many reasons for using orbital welding equipment. The ability to make high

quality, consistent welds repeatedly, at a speed close to the maximum weld speed, offer

many benefits to the user:

1. Productivity. An orbital welding system will drastically outperform manual welders,

many times paying for the cost of the orbital equipment in a single job.

2. Quality. The quality of a weld created by an orbital welding system (with the correct

weld program) will be superior to that of manual welding. In applications such as

semiconductor or pharmaceutical tube welding, orbital welding is the only means to

reach the weld quality requirements.

3. Consistency. Once a weld program has been established, an orbital welding

system can repeatedly perform the same weld hundreds of times, eliminating the

normal variability, inconsistencies, errors, and defects of manual welding.

4. Skill level. Certified welders are increasingly hard to find. With orbital welding

equipment, you don't need a certified welding operator. All it takes is a skilled mechanic

with some weld training.

5. Versatility. Orbital welding may be used in applications where a tube or pipe to be

welded cannot be rotated or where rotation of the part is not practical. In addition,

orbital welding may be used in applications where access space restrictions limit the

physical size of the welding device. Weld heads may be used in rows of boiler tubing,

where it would be difficult for a manual welder to use a welding torch or view the weld

joint.

Many other reasons exist for the use of orbital equipment over manual welding. For

example, applications where inspection of the internal weld is not practical for each weld

created. By making a sample weld coupon that passes certification, the logic holds that if

the sample weld is acceptable, that successive welds created by an automatic machine

with the same input parameters should also be sound.

General Guidelines for Orbital Tube Welding

For orbital welding in many precision or high purity applications, the base material to be

welded; the tube diameter(s); weld joint and part fit-up requirements; shield gas type and

purity; arc length; and Tungsten electrode material, tip geometry, and surface condition

may already be written into a specification covering the application.

Each orbital welding equipment supplier differs slightly in recommended welding practices

and procedures. Where possible, follow the recommendations of your orbital equipment

supplier for equipment set-up and use, especially in areas that pertain to warranty issues.

Note that, this section is only intended as a guideline for those applications where no

specification exists. The engineer responsible for the welding must create the welding set-

up, and derive the welding parameters, in order to arrive at the optimum welding solution.

WELDING BASICS AND SET-UP

The Physics of the GTAW Process

The orbital welding process uses the Gas Tungsten Arc Welding process (GTAW), as the

source of the electric arc that melts the base material and forms the weld. In the GTAW

process (also referred to as the Tungsten Inert Gas process - TIG) an electric arc is

established between a Tungsten electrode and the part to be welded. To start the arc, an

RF or high voltage signal (usually 3.5 to 7 KV) is used to break down (ionize) the insulating

properties of the shield gas and make it electrically conductive in order to pass through a

tiny amount of current. A capacitor dumps current into this electrical path, which reduces

the arc voltage to a level where the power supply can then supply current for the arc. The

power supply responds to the demand and provides weld current to keep the arc

established. The metal to be welded is melted by the intense heat of the arc and fuses

together.

Material Weldability

The material selected varies according to the application and environment the tubing must

survive. The mechanical, thermal, stability, and corrosion resistance requirements of the

application will dictate the material chosen. For complex applications, a significant amount

of testing will be necessary to ensure the long-term suitability of the chosen material from a

functionality and cost viewpoint.

In general, the most commonly used 300 series stainless steels have a high degree of

weldability with the exception of 303/303SE, which contain additives for ease of machining.

Four hundred series stainless steels are often weldable, but may require post weld heat

treatment.

Accommodation must be made for the potential differences of different material heats. The

chemical composition of each heat batch number will have minor differences in the

concentration of alloying and trace elements. These trace elements can vary the

conductivity and melting characteristics slightly for each heat. When a change in heat

number is made, a test coupon should be made for the new heat. Minor changes in

amperage may be required to return the weld to its original profile.

It is important that certain elements of the material be held to close tolerances. Minor

deviations in elements, such as sulfur, can vary the fluid flow in the weld pool, completely

changing the weld profile and causing arc wander.

Weld Joint Fit-Up

Weld joint fit-up is dependent on the weld specification requirements on tube straightness,

weld concavity, reinforcement, and drop through. If no specification exists, the laws of

physics will require that the molten material flow and compensate for tube mismatch and

any gap in the weld joint.

Tubing is produced according to tolerances that are rigid or loose according to the

application for which the tube was purchased. It is important that the wall thickness is

repeatable at the weld joint from part to part. Differences in tube diameter or out-of-

roundness will cause weld joint mismatch and arc gap variations from one welding set up

to another.

Tube and pipe end prep facing equipment is recommended in order to help ensure end

squareness and end flatness. Both the I.D. and O.D. should be burr free with no

chamfer.When two tubes are butted together for welding, two of the main considerations

are mismatch and gaps. In general, the following rules apply:

v Any gap should be less than five percent of the wall thickness. It is possible to weld

with gaps of up to 10 percent (or greater) of wall thickness, but the resultant quality of

weld will suffer greatly, and repeatability will also become a significant challenge.

v Wall thickness variations at the weld zone should be +/- five percent of nominal wall

thickness. Again, the laws of physics will allow welding with mismatch of up to 25

percent of wall thickness if this is the only challenge. Again, the resultant quality of weld

will suffer greatly, and repeatability will become an issue.

v Alignment mismatch (high-low) should be avoided by using engineering stands and clamps

to align the two tubes to be welded. This system also removes the mechanical requirement of

aligning the tubes from the orbital weld head.

Shield Gas (es)

An inert gas is required on the tube O.D. and I.D. during welding to prevent the molten material from combining with the oxygen in the ambient atmosphere. The objective of the welder should be to create a weld that has zero tint at the weld zone I.D.

Argon is the most commonly used shield gas (for the O.D. of the tube) and the purge gas

(for the I.D. of the tube). Helium is often used for welding on copper material. Mixed gases,

such as 98 percent Argon/two percent Hydrogen; 95 percent Argon/five percent Hydrogen;

90 percent Argon/10 percent Hydrogen; or 75 percent Helium/25 percent Argon may be

used when the wall thickness to be welded is heavy (.1" or above). Using mixtures of 95

percent Argon/five percent Hydrogen is incompatible with carbon steels and some exotic

alloys, often causing hydrogen embrittlement in the resultant weld. As a general rule, for

simplicity and reduction of shield gas cost, use 100 percent Argon gas.

Gas purity is dictated by the application. For high purity situations, where the concern for

micro-contamination is paramount, such as semiconductor and pharmaceutical

applications, the shield and purge gases must minimize the heat tint that could otherwise

be undesirable. In these applications, ultra high purity gas or gas with a local purifier is

employed. For non-critical applications, commercial grade argon gas may be used.

Tungsten Electrode

The Tungsten welding electrode, the source of the welding arc, is one of the most

important elements of the welding system that is commonly ignored by welding systems

users. Users continue to manually grind and wonder why they produce inconsistent

results. Whether in manual or automatic welding, this is the area where manufacturing

organizations can improve the consistency of their welding output with minor effort.

Basically, the objective for the choice of Tungsten parameters is to balance the benefits of

a clean arc start and reduced arc wander with good weld penetration and a satisfactory

electrode life.

Electrode Materials

For quite some time, Tungsten manufacturers have added an oxide to pure Tungsten to

improve the arc starting characteristics and longevity of pure Tungsten electrodes. In the

orbital welding industry, the most commonly used electrode materials are two percent

thoriated Tungsten and two percent ceriated Tungsten.

Safety

The safety issues of Tungsten electrode material are now being looked at more closely.

Many users of the TIG welding process do not realize that the welding electrode they use

contains Thorium, a radioactive element added to the Tungsten. While the radioactivity is

of a low level, it brings an issue of danger, especially with the radioactive dust that is

generated when grinding the electrodes to a point for welding.

Alternative, non-radioactive Tungsten materials are now available, such as two percent

ceriated electrodes, which often offer superior arc welding. While these materials are

commercially available they have been largely ignored until recently. Recommended

Electrode Materials

Cerium, as a base material, has a lower work function than Thorium, offering superior

emission characteristics. So, not only do ceriated electrodes offer an advance in electrode

safety, they also improve the arc starting ability of the orbital equipment. However, as

mentioned earlier, it is always best to follow the advice of your orbital equipment

manufacturer.

Electrode Tip Geometry

Given the ever-increasing weld quality requirements of the final weld, more and more

companies are looking for ways to ensure that their weld quality is up to par. Consistency

and repeatability are key to welding applications. The shape and quality of the Tungsten

electrode tip is also being recognized as a vital process variable. Once a weld procedure

has been established, it is important that consistent electrode material, tip geometry, and

surface condition be used.

Welders should follow an equipment supplier's suggested procedures and dimensions first,

because they have usually performed a significant amount of qualifying and

troubleshooting work to optimize electrode preparation for their equipment. However,

where these specifications do not exist, or the welder or engineer would like to change

those settings to possibly improve and optimize their welding, the following guidelines

apply:

Electrode Taper

This is usually called out in degrees of included angle (usually anywhere between 14° and

60°). Below is a summary chart that illustrates how different tapers offer different arc

shapes and features:

Sharper Electrodes Blunter Electrodes

Last less than blunt Last longer

Less weld penetration Better weld penetration

Wider arc shape Narrower arc shape

Handle less amperage Handle more amperage

Less arc wander Potential for more arc wander

More consistent arc Less consistent arc

To demonstrate graphically how the taper selection will effect the size of the weld bead

and the amount of penetration, the following drawing shows typical representations of the

arc shape and resultant weld profile for different tapers.

Electrode Tip Diameter

Grinding an electrode to a point is sometimes desirable for certain applications, especially

where arc starting is difficult or short duration welds on small parts are performed. In most

cases, however, it is best for a welder to leave a flat spot or tip diameter at the end of

electrode. This reduces erosion at the thin part of a point, and reduces the concern that the

tip may fall into the weld. Larger and smaller tip diameters offer the following trade-offs:

Smaller Tip Larger Tip

Easier to start Usually harder to start

Less arc wander More chance of arc wander

Less electrode life More electrode life

Less weld penetration More weld penetration

Tungsten Electrode Grinders and Pre-Ground Electrodes

Using electrodes pre-ground to requirements or a dedicated commercial electrode grinder

to provide electrode tip quality and consistency, offers the following benefits to the user in

their welding process:

Improved arc starting, increased arc stability, and more consistent weld penetration.

v Longer electrode life before electrode wear or contamination.

v Reduction of Tungsten shedding. This minimizes the possibility of Tungsten

inclusions in the weld.

v A dedicated electrode grinder helps ensure that the welding electrodes will not

become contaminated by residue or material left on a standard shop grinder wheel.

v Tungsten electrode grinding equipment requires less skill to ensure that the

Tungsten electrode is ground correctly and with more consistency.

Pre-Ground Electrodes

Rather than risk electrode radioactivity issues, and constantly endure the variability of each

operator grinding the electrodes with a slightly different touch, many manufacturing

organizations have chosen to purchase electrodes pre-ground. Since a small difference in

the dimensions of an orbital electrode can produce a big difference in the weld results, pre-

ground electrodes are the preferred electrode choice to maintain the consistency of your

welding. This low-cost option ensures that the electrode material quality, tip geometry, and

ground electrode surface input to the welding process is constant. Consult electrode charts

or a pre-ground electrode supplier to obtain the electrode diameter and tip geometry that is

most suitable for your welding application.

Conclusion

In conclusion, the important points to remember are:

v Orbital welding has been used by many industries to improve the quality and

quantity of tube welding when compared to what can be accomplished by manual

welders.

v The effective cost of an employee computes to be significantly more than just his

base salary. The output of a $20 per hour skilled welder actually costs over $72,000

per year (almost twice his yearly base wage).

v If a complete orbital welding system costs between $15,000 and $20,000 and

can output over twice the amount of welding that a manual welder can produce then

the equipment will pay for itself in a matter of months.

v Finally, the volume of welds that are produced by an automated welding system

will far exceed that of a manual welder. In addition to weld quality improvements, this

will bring two additional financial benefits: One, increased output per day at lower cost.

Two, lowered scrap and rework costs due to improved weld consistency.

Tubesheet Weld Heads - Orbital Welding Equipment

/ Automated Welding Equipment

These Magnatech weld heads are specifically designed for making tube-

to-tubesheet welds. Configured for fast and simple operation, the Head

is inserted into the tube to be welded, and the operator pushes the

START WELD switch.

Multiple torch positioning adjustments allow virtually all tubesheet joint

designs to be welded. All three models weld a wide range of tube sizes

and operate in any position.

For welds requiring filler wire addition, an optional wire feeder can be

mounted on the weld head. A standard wire spool, mounted directly on

the Head, provides precise and positive wire feeding, not possible with

floor-mounted feeders.

These weld Heads bring the productivity and repetitive precision of

machine welding to the fabrication and repair of steam generators and

heat exchangers.

All three weld Heads models are used with Magnatech power sources,

ranging form simple to operate analog models to microprocessor-based

systems with program storage capability.

TUBE GEOMETRIES

Model 424 is ideal for all tubesheet geometries.

Model 425 with AVC is for multipass welding

Model 426 is ideal for fusion welding where preheat is not required.

Process: GTAW

Weld Head Type: Open arc.

Tube Size Range: Model 424: 10mm - 78mm (0.4" - 3.07") OD

Model 425: 10mm - 140.2mm (0.4" - 5.52") OD

Model 426: 10mm - 70.1mm (0.4" - 2.76") OD

Features:

• Water-cooled torch and weld Head body

(models 425 & 426 only) allow use on

pre-heated tubesheets

• Lifting eye allows use on a

counterbalance for weightless operation

• Multiple torch angle and wire feed

positioning mechanism allow optimum

torch position and wire entry angle

• Simple centering cartridge design allows

quick installation without requiring prior

installation of expensive custom-

fabricated locating fixtures

• Inexpensive centering cartridges fit the

exact tube ID

• Filler wire spool rotates with the torch -

eliminating wire entry problems common

with floor-mounted feeders (Models 424

& 425)

• No cable wrap-up

Options: • Filler Wire feeder using standard 1kg

(2lbs.) spools

• Three point standoff for welding

"extended tube" geometries

• Transparent purge gas chamber for

titanium floods the enclosed weld area

independent of torch shielding gas,

reducing purge time and weld oxidation

• Arc Voltage Control parallel to tungsten

electrode - even when the torch is

angled for a fillet weld

• Torches for internal bore welding

• Extension Cables

• Dual Head Switcher allows two Heads

to be used alternately maximizing "arc

on" duty cycle

Applications:

• Heat exchanger seal and strength welds

• Power generation

• Petrochemical

• Sanitary

• Food and beverage

@@@@

171

Erection Procedure for Rear Water Box & Rear water Chamber

Condensers supplied by Haridwar for 210/250/500 MW ratings are having flanged connection between water box and water chamber at both the ends. (Front & rear). This is to facilitate re-tubing in case it is required. With the use of stainless steel, reliability of condenser tube material has increased and chances of failures and re-tubing has reduced tremendously.

In Amarkantak 210 MW, flanges have been removed from rear water box & water chamber and both have been directly welded together. Space for re-tubing has been kept on front water box side.

A- Pre assembly

1. Place both Rear water chambers on horizontal surface with water side surface of tube plate on top position. Level the water chambers w.r.t tube plate. Mark top & bottom position of water chambers.

2. Weld backing strip on all four walls of water chambers as shown in Fig.I. In Rear water chamber (GS) backing strip will be welded inside on all the four walls and on Rear water chamber (TS) it will be welded inside on three walls and outside on vertical wall near condenser centre line.

3. Measure tube sheet flatness as per recommended procedure and record the dimensions in log sheet L-02.

4. Water box inside length & width and corresponding dimensions of water chamber to be checked w.r.t. horizontal & vertical centre lines and recorded in log sheet to ascertain trueness of dimensions.

5. If logged dimensions indicate any mismatch, same may be corrected

6. Match Rear water Box (TS/GS) by lowering it over respective water chamber / backing strip such that the weld edges of water chamber and water box match for proper welding. In case of mismatch, the same to be rectified.

B - Assembly : Assembly can be done in two ways as per site’s convenience. Option –1

7. Remove the water box after completing the activity as per A (6) above.

Page : 2 of 2

172

8. Weld 4 number channels (2 horizontal & 2 vertical) of size 100x50 along the length

and width to stiffen the water chamber. Refer Fig. I. Holes in the tube plate to be suitably protected.

9. Lower the water chamber (without water box) on bottom plate for erection as per

standard procedure.

10. Tack weld / final weld water chamber with side walls and bottom plate. 11. Carry out tubing.

12. Weld the water boxes using proper welding sequence as given (C ) below.

Option – II (Refer Fig.-2)

13. Weld water box and chamber with the help of technological plates (12 x 100 x 250)

as shown in the drawing.

14. Lower water box and chamber together for erection.

15. Tack weld / Final weld water chamber with side walls and bottom plate.

16. Remove water box to facilitate tubing & expansion by cutting stiffening plates.

17. Carry out tubing.

18. Weld the water boxes using proper welding sequence as given (C ) below.

C- Welding sequence for water box & water chamber (Refer Fig-3)

1. Tack weld Water box (GS) and Chamber(GS) -100 (200).

2. Root run on all sides.

3. Final welding to be done as per Detail-I.

4. Welding of Generator side water box-Water chamber to be completed first as it has all

welds from outside.

5. Bring Turbine side water box in position. Repeat steps 1-4 indicated above.

6. All welding is from outside except vertical welding of Rear water box & water chamber

(TS) near condenser centerline which is from inside.

7. Direction of welding shall be as indicated in the drawing.

8. Over head welding is required for carrying out bottom welding of water boxes and water

chambers.

(Naveen Prakash) (S.K.Baveja) (Lalit Kishore)

176

NOTES FOR WELDING THERMOCOUPLE PADS & CLAMPS FOR SH & RH METAL TEMPERATURE MEASUREMENT

Pad / Clamp Material : SS 304, 316, 321, 310

Sl.No Tube Material (SH & RH)

Thickness in mm (t – max).

Thermocouple pad Material

Pre-heat (min)

Post-weld heat

Treatment

Consumable Electrode

1 SA210 Gr. A1 7.6

SS 304, 316, 321, 310 NIL NIL E7018 A1

2 SA213 T11 8.6

SS 304, 316, 321, 310 1250C NIL E7018 A1

t<8.0

SS 304, 316, 321, 310 1500C NIL E7018 A1

8.0 to 12.0

SS 304, 316, 321 NIL NIL E 309

3

SA213 T22

8.0 to 12.0 SS 310

1500C ON T22 Side NIL E 309

7300C to 7600C

(min, 30 minutes)

4 SA213 T91

ALL THICKNESS

SS 304, 316, 321, 310

2200C ON T91 Side

E 309

5 SA213 TP347 H ALL THICKNESS SS 304, 316, 321 NIL NIL E 347

6 SA213 TP347 H 12.0 (max.) SS 310 NIL NIL E 309

NOTE :

1 The above had been discussed with WTC on 25th May 2006 for the applicability and confirmed thro email by WTC on 29th May 2006

2 The above can be taken as the general guidelines for all the boilers.

3 Electrode size : 2.50 mm

4 Welder shall strike ARC on Thermocouple pad or "Run-on Run-off" Block and bring are up to side of thermocouple pad using as low a current as possible to avoid burn-through.

177

WELDING AND PWHT SEQUENCE FOR LOWER RING DRUM 1.0 PURPOSE 1.1 To describe the welding and PWHT (Post Weld Heat Treatment) sequences for the four

field welds in the lower ring drum. 2.0 PROCEDURE 2.1 One of the sequences indicated below is to be followed when welding the four joints in

the lower ring drum shown in figure 1. The main concern is that joints on opposite ends of the crossover pipe not be welded simultaneously.

2.1.1 Joints 1,2,3 and 4 be welded individually in that order. 2.1.2 Joints 1 and 2 be welded simultaneously then joint 3 and 4 simultaneously. 2.1.3 Joints 1 and 2 be welded simultaneously then joint 3, then joint 4 (or 3 and 4

simultaneously, followed by 1 and 2 individually). 2.2 PWHT be performed in the following sequence :

2.2.1 Joints 1 and 2 simultaneously, followed by joints 3 and 4 simultaneously.

178

WORK INSTRUCTIONS FOR DEMAGNETISATION

• Use Residual field- indicator at one end of stub tube and measure the residual field. (GUASS METER)

• Note reading and direction of field + ve or - ve- ¦¦¦¦¦¦¦¦¦¦|¦¦¦¦¦¦¦¦¦¦ +10 á 0 -10 • Indicator may show readings greater than + 10 or -10 Divisions . • A smaller dia electrode or gem-clip will get attracted & stick to stub tube DEMAGNETISATION PROCEDURE: Wrap insulated welding cable - 5 turns-clockwise on the Outer Dia surface of stub tube. - Wrapped cable to be wound 50 to 100 mm away from stub tube. - One cable-end connect to + ve terminal of welding generator - The other cable-end to - ve terminal

- Complete electrical circuit & Pass 400 amps current 2 to 3 seconds and reduce the current gradually to zero or minimum.. - Measure residual field now at the same end of stub tube - If de-magnetisation is effective the reading will come closer to '0' - For Eg. If it is formerly > + 10 Divns. , it may show now + 5 divisions or less than 5 or even -Divns.

- The electrode or gem-clip will not get attracted to stub tube end • If de-magnetisation is NOT effective - The gem-clip/electrode will be attracted to stub tube. - Readings will show more divisions in the same direction • TO effectively DE-MAGNETISE : - Change the polarity of cables attached to welding generator (or) - Wrap the insulated cable (5turns) in anti-clockwise direction - Pass current slightly excess of 400 Amps - Reduce the current gradually to 0 amps in one minute when current is on. - You will find the ends are de-magnetised - The gem-clip/electrode WILL NOT GET attracted. (P.S.Subbaraman) (R.J.Pardikar) DY MANAGER /NDT SDGM / NDT Level II Sr.Level III

179

ERECTION WELDING PRACTICE FOR SA 213 T 91 MATERIAL 1.0 Scope :

1.1 This document details salient practices to be adopted during welding of SA213 T91

material.

2.0 MATERIAL

2.1 SA213 T91 Dia, and thickness will be as per Erection Welding Schedule for the site

2.2 When any defect like crack, lamination, deposit noticed during visual examination, the

same shall be confirmed by Liquid Penetrant Inspection. If confirmed, it shall be referred

to unit.

3.0 ERECTION

3.1 EDGE PREPARATION AND FIT UP

3.1.1 Cutting of T-91 material shall be done by band saw/hacksaw/machining/ grinding only.

Edge preparation (EP) shall be done only by machining. In extreme cases, grinding can

be done with prior approval of Welding Engineer/ Quality Assurance Engineer. During

machining/ grinding, care should be taken to avoid excessive pressure to prevent

heating up of to the tube edges.

3.1.2 All Edge Preparations done at site shall be subjected to Liquid Penetrate Inspection

(LPI). Weld build-up on Edge Preparation is prohibited.

3.1.3 The weld fit-up shall be carried out properly to ensure proper alignment and root gap.

Neither tack welds nor bridge piece shall be used to secure alignment. Fit-up by a

clamping arrangement is recommended. Coil load to be transferred to crown plate/ end

bar assembly. Ensure that coil load should not come on stubs/header. Use site

fabricated clamps for fit up. The necessary preheat and purging shall be done as per

clause 4.1 and 3.2.2 ref. WPS No. 1036 Rev 04 dt 02 04 04.

3.1.4 The fit-up and root gap shall be as per drawing.

3.2.0 FIXING OF THERMOCOUPLE (T/C), DURING PREHEATING AND PWHT

3.2.1 No. Preheating is required for fixing T/C with resistance spot welding.

Following are the equipment/ facilities required for heating cycles.

(1) Heating methods: Resistance heating

(2) Thermo couples: Ni-Cr/ Ni-Al of 0.5mm.

(3) Temp. Recorders: 6 Points/12 Points.

180

3.2.2 ARRANGEMENT FOR PURGING:

Argon gas with requisite quality shall be used for purging the root side of weld. The

purging dam (water soluble paper) shall be fixed on HDR Nipple side of the weld bevel

prior to fit-up and pre-heating. Purging is to be done from cross over tube down stream

end. ( Sketch 3). Ensure that atmosphere air is completely purged out through the root

gap before starting welding and welding can be continued with Argon backing.

The flow rate is to be maintained for purging is 6 to 8 litres/ minute and for GTAW is 8-12

litres/ minute.

3.2.3 When root temperature reaches 220oC, start purging through cross over tube down

stream end for 5 minutes. Then the root gap to be covered by asbestos rope. Provide

continuous and adequate argon gas to ensure complete purging in the root area. Only

water-soluble paper is to be used. Plastic foils that are water-soluble are NOT

acceptable.

3.2.4 USING OF WATER SOLUBLE PAPER

The dams can be made of water-soluble paper for creating the purging chamber. The

advantage in such dam arrangement is that the dissolving paper dam gets flushed

during hydraulic test. The following is the method to be used:

Simply stuff water-soluble paper into the Header Nipples at specified distance from the

weld as per attached sketch 1

SKETCH - 1

181

4.0 WELDING/WELDERS QUALIFICATION:

Only qualified welding procedure is to be used. Welders qualified as per ASME Sec IX

and IBR and on T91 material shall be engaged. Welders log book shall be maintained

and welders performance to be monitored by site welding engineer/ Quality assurance

engineer. The applicable WPS for T91+T91 shall be WPS No. 1036/04 dt. 02/04/04.

4.1 PREHEATING (Bunching of tubes can be followed):

Prior to start of pre heating ensure that surface are clean and free from grease, oil and

dirt. Preheating temp shall be maintained at 220oC (min) by using resistance heating.

Sufficient number of thermo couples shall be fixed on both coils and header nipples

away from the EP. The thermocouple shall be welded with the condenser discharge

portable spot welding machine. The pre heating arrangements shall be inspected and

cleared by welding engineer/ Quality Assurance Engineer before start of preheating. Ref

. Sketch 2

4.2.1 WELDING:

Welding shall be done using GTAW process (as per WPS). Filler wire shall be clean and

free from rust or oil. Argon Purging shall be continued till completion of welding.

5.0 POST WELD HEAT TREATMENT (PWHT) – RESISTANCE HEATING METHOD (Bunching of tubes can be followed):

Arrangements: Sufficient number of thermocouples shall be placed covering weld and

the base material. The width of the heated circumferential band on either side of the

weld must be at least 100mm. ( Sketch 2)

5.1 Obtain the clearance for PWHT cycle from QAE/ Welding Engineer. The PWHT temp for

T91 with T91 material shall be 760 ± 10oC and the soaking time shall be 90 minutes.

5.2 Welding and Heat treatment chart given in ( Sketch 4) shall be followed for pre-hating,

welding, PWHT, rate of heating/ cooling etc.

6.0 NDE: Carry out Non-Destructive Examination (RT) as per Field Welding Schedule.

7.0 HARDNESS SURVEY:

100% hardness survey shall be conducted on welds and parent material in first five coils.

Based on satisfactory results, the hardness survey can be reduced to 10% covering all

the heat treatment cycles.

The equipment recommended to measure the hardness is EQUOTIP or equivalent.

Portable equipment used in the hardness measurement shall be calibrated .

The surface shall be cleaned and prepared as per hardness test instrument

manufacture’s recommendation prior to hardness survey.

Hardness survey of weld and parent metal (both tubes) shall be carried out.

All the hardness values shall be recorded.

The maximum allowable hardness at weld and parent material shall be 300HV10.

184

ERECTION WELDING PRACTICE FOR SA 213 T 91 MATERIAL . WELDING AND HEAT TREATMENT CHART Temp °C 760°± 10°C 350° 220° 100° 80° HT 1 2 3 4 5 6 7 8

SKETCH- 4

Sl. No.

Operation Temp °C Rate of cooling/Heating

1 Preheat 220°C (Min.) 120°C /hr (Max.) 2 Welding by GTAW 350°C (Interpass-Max.) 3 Cooling 80°- 100°C 120°C /hr (Max.) 4 Holding at 80-100 C to minimum 30 minutes. Holding shall continue till the

start of PWHT 5 Heating to PWHT Reach 760° ± 10°C 120°C /hr (Max.) 6 Soaking at PWHT 760° ± 10°C for 90

minutes (Min.)

7 Cooling Cooling to 350°C 120°C /hr (Max.) 8 Cooling Cooling to Room

temperature under insulation.

welding manual r01 nov 2006

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