SUMMER INTERNSHIP REPORT

ON

STUDY OF FABRICATION OF SPOOLS & CYCLE TIME

Submitted by:- Prasoon Kumar

(B.Tech-Mechanical, 3rd Yr, VIT University, Vellore)

Guided by:- Mr Pankaj Chauhan

Mentor:- Mr Partha Ghosh

Submitted to:- Mr Siddharth Brahmbhatt

SUMMARY

The 4-week summer internship was carried out at the Piping Centre facility of L&T (Larsen & Toubro) situated in Hazira Manufacturing Complex, on the outskirts of Surat city. The piping centre falls under the umbrella of L&T-HED (Heavy engineering division) and involves the fabrication of pipe spools in accordance with the order coming from various industries. The training programme provided me with the idea of how pipe spools get manufactured, various processes involved, purchase of materials, project planning, quality assurance, packaging and the logistics of final product developed.

The training was scheduled from 09.06.2016 (9th of June) to 14.07.2016 (14th of July) and was successfully carried out in ‘Production’ department under the mentorship of Mr. Partha Ghosh (Head- Production). The training started off with the first and the foremost thing to be followed in any industry or shop floor i.e. Safety Induction, this enlightened me with the precautionary and safety measures to be followed while a person is at the shop floor. The entire manufacturing of pipe spools is carried out at the shop floor whereas the finished goods (FG) yard and the open fabrication yard occupy a separate space. The major departments of piping centre are as follows:-

1) Production 2) Welding & Maintenance3) Quality Assurance/ Quality Control4) PMG (project management group) & Planning5) Supply Chain Management (involves logistics, stores etc.)6) EHS (environment, health and safety)7) HR (human resource)8) Design9) BDM (business development & marketing)10) IT11) Finance

I got to know about the functioning of each and every department and how they are connected to one another. During the programme, I was assigned the task of observing and noting down the cycle time for each and every process carried out involved in the manufacturing of spools and suggest any improvisations as per the knowledge gained. The task also comprised of understanding the process flow of pipe spools right from the stage when the raw materials come till the final stage where they get dispatched as ‘SPOOLS’. The entire functioning of Production department was thoroughly explained along with the pros & cons of every process involved. I also got a brief idea regarding the overall business of piping centre.

ACKNOWLEDGEMENT

In an organization, no goal or objective can get accomplished successfully if people working their fail to work together as a TEAM. Here at piping centre, I got the sheer support and guidance of numerous talented young officers who were always ready to impart me with their endless energy and knowledge whenever asked upon. The immensely experienced personalities occupying the prime positions in each and every department on the shop floor enlightened me with their rich working experience, wisdom, professionalism and can-do attitude towards their job. All these ‘SIR’ tried their level best in making me understand each and every process going on at L&T- Piping Centre.

In Production department- energetic officers namely Mr Dharmesh Tailor; Mr Hardik Chauhan; Mr Pragnesh; so called machine expert Mr Rajesh Patel; Mr Yogesh Vispute; my guide Mr Pankaj Chauhan and my mentor Mr Partha Ghosh (Head- Production), all these brilliant minds cleared all my doubts and queries as and when required thus making my concepts crystal clear related to the manufacturing processes.

In Welding department, Mr Mohnish and Mr Vimal bear the golden badge for tolerating me as I disturbed them frequently with my doubts and queries. Mr Suprabhat Das Gupta (Head- Welding) shared his level of expertise and knowledge with me and told me about the concept of HIRA (Hazard identification and risk assessment), a rare entity to be found in any industry.

Mr Mehul Patel from EHS department made me go through the various safety methods which are followed at Piping centre to avoid any kind of mishap. Mr Ashish Saraf from Stores gave me an overview of how and from where the materials are received, the selection of vendors, placing of purchase order and the handing over of pipes to PPS (pipe preparatory shop) for further processing. The officers from Quality, PMG-Planning and Maintenance departments also helped me in going through the basic functioning of their respective departments.

From the cores of the HR, Mr Darshan Joshi; Mr Siddharth Brahmabhatt and Ms Sonali Dash beared the pain of catering to my day-to-day queries, sometimes related to stupid issues. They always stood firm behind me and were always ready to extend any kind of support related to the training.

I would like to express my sincerest thankfulness and gratitude to all the above officers for sparing time from their busy schedule and sharing their knowledge and experience with me.

Last but not the least, I whole-heartedly thank Mr Vinay Desai (Head- HR); Mr Binoy Shaw (Head- Manufacturing); and Mr F.N. Chokshi (General Manager and Head- L&T Piping Centre) for allowing me to keenly observe the proceedings of L&T-Piping Centre and providing me an opportunity to work with such a great and terrific bunch of engineers. This training couldn’t have been possible without the sheer support of these personalities.

This 1-month training provided me with the cutting edge to use the culmination of imagination and engineering thus creating something innovative which is useful, both for the society as well as for the organizations.

ORGANIZATION CHART

Strategic Business Unit (SBU) Head

Head-Production

Head-Finance Head-HR

Head-Welding &

Maint.

Head-PMG &

Planning

Head-SCM Head-EHS Head-IT

Head-Quality Head-BDM

Co-ordinator

Co-ordinator

Co-ordinator

Co-ordinator

Co-ordinator

Co-ordinator

Co-ordinator

Co-ordinator

Co-ordinator

Co-ordinator

SCM- Supply Chain Management

EHS- Environment, Health & Safety

BDM- Business Development & Marketing

PMG- Project Management Group

Introduction SPOOLS Overall plant layout Overall process flow of Pipe spools PMG (project management group) & Planning

Overall operation Role of PMG Role of planning

EHS (Environment, health & safety) department HIRAC (Hazard identification & risk assessment control) Method to tie-up and lift-up the pipe spools

Crane matrix at LTPC Pump house & Compressor house Production department function

Responsibilities Workflow matrix and organization structure Pipe schedule Fit-up of pipe spools Bend marking procedure Cojafex Hot induction bending machine SAFOP Edge preparation machine & Insert used Bandsaw cutting machine Blasting booth & operation Painting booth & operation Difference between fabrication of alloy steel, carbon steel and

stainless steel spools Fabrication of stainless steel (SS) spools in enclosure Cleats and Tack welding PPS (pipe preparatory shop) and colour coding of spools Fittings & Forgings for pipe spools Differences between SAFOP EP & LATHE Cycle time study for Alloy steel & carbon steel spools Spot check report

Welding department function Responsibilities Workflow matrix and organization structure Definition of Welding and its types SAW (sub-merged arc welding)

SMAW (shielded metal arc welding) GTAW (gas tungsten arc welding) FCAW (flux cored arc welding) WPS (welding procedure specification) Pre-heating & Post-heating process Introduction to heat treatment furnace Need for heat treatment & types used at LTPC Welding cycle for P91 material & standard procedure which is

to be followed Microstructure variation of P91/P92, P11/P22, SA106 (Carbon

steel) spools in parent material, welded area & heat affected zone (HAZ).

Inter-pass and pre-heat temperatures for different materials Defects in welding Electrode grading and identification depending on welding

process and material Role of each & every alloying element added Shielding gas, backing gas & trailing gas

Quality Assurance/Quality Control Responsibilities Radiography testing (RT) and film preparation Ultrasonic testing (UT) Magnetic particle testing (MPT) Positive material identification (PMI) Dye-penetrant testing (DPT) IRN/ICS & DCN

Conclusion

Piping Centre Facilities & Capabilities

The Piping Centre is located in L&T’s sprawling 763-acre manufacturing complex at Hazira, (a major port, 21 km from Surat, 300 km from Mumbai, and just eight kilometres from the Arabian Sea). Equipment fabricated can be shipped out on barges or via road through NH 6 and NH 8. Spread over 30 acres, the Centre has a covered shop area of 16200 sq.m including two bays (340x30m each), and a manufacturing capacity of 12000 MT per year. The Centre is certified by ISO, IBR and ASME (for S, PP and R stamps).

The Centre is an impressive assembly of technology, expertise, people and processes- all primed to provide cutting-edge piping solutions to companies in the core sector. Around 350 experienced piping engineers and skilled workmen deliver solutions based on the Centre’s all-round capabilities that encompass design, engineering, fabrication, project management and SCM. This translates into cost-effective, on-time delivery of world-class solutions, augmented by support during erection and beyond through the life-cycle of the plant.

The Piping Centre Advantage End-to-end quality piping solutions minimising rework/disruption at site. SAP-enabled integrated ERP system Proven capability of handling CS/LAS/SS material including P91/P92/WB36 up to

120 mm thickness & API 5L Grade material e.g. X65, X70, etc On-site welding minimised, reducing cost and time Eighty per cent of critical welding done using mechanised processes with best-in-

class equipment. Induction and cold bending machines. Can bend pipes of any thickness or diameter

for super-critical power plants.

SPOOLSRaw material is received at piping centre and finally gets dispatched as a ‘Spool’. A spool is a combination of:-

1) Straight sections/pipes2) Fittings3) Forgings4) Extended Supports

As per orders and rough sketch received from clients pertaining to thermal power plants, oil refineries, fertilizer companies, nuclear power plants etc, a refined drawing is constructed by the Design department which may or may not comprise of the above four sections. The final combination is termed as a ‘Spool’. In other words, the various parts clubbed together to form a pathway for transmission of fluids via pipes is a ‘Spool’.

Straight sections comprise of only straight pipes with no bends at all.

Fittings are used so as to provide a branch connection to all other pipes. At LTPC, various fittings used are- Tees, elbows, bends, and reducers.

Forgings are parts which have been formed by forging method. These are used either to connect smaller pipes to bigger pipes or to install some kind of measuring device such as pressure gauges, valves, temperature gauges etc. Forgings used at LTPC are- Weldolet, Sockolet, Threadolet, Thermowell, Nozzles, Flanges etc.

Extended supports as the name suggests are provided as a support for the mother pipe. This prevents any kind of unwanted movement of the mother/header pipe. Ex- Trunnion sections with base plate.

Each and every pipe spool is finally characterized with these details which is collectively termed as Material Identification (MI):-

1) Spool number2) Batch number3) Heat number (given after heat treatment)4) Material description (which type of material as per ASME grade, ASTM etc.)

Overall Plant Layout

Open Fabrication Yard

Finished

Goods

Yard

Stores

Paint Shed

Maintenance Shed

Pump house & Compressor house

Sub Station

Welding School

Canteen

Workmen Restroom

Security Gate-

9

Bay 2 Bay 1

Bay 1Bay 2

Pipe Preparatory Shop (PPS) Bay 1

PPS Bay 2

Admin Bldg

Overall Process flow of spools

Material Received

Raw material inspection

Unique identification no generated by LTPC

Material details to be fed in SAP

IBR ??

IBR Inspection

MIN generated

Material handed over to PPS

PPS handover to contractor

MIN generated against spool

MIN handover to PPS

MIN submitted to store by PPS

PPS to contractor

Fit-up operation

Weld visual BSR (before stress relieve)

NDE (non-destructive examination)

NDE

PWHT (post weld heat treatment)

Weld visual ASR (after stress relieve)

NDE

Hardness test (only in alloy steel)

FD (final dimensioning)

Weld removal by grinding

NDE

Welding operation

NDE performed again

YES NO

OK NOT OK

Spool offered to IBR

IRN signed by IBR

TPI visit

Painting inspection Blasting & Painting

Painting offered to quality control

Painting report generated

SCN generated

FG yard

IBR- Indian Boiler Regulation

SCN- Stores credit note

TPI- Third party inspection

FG- Finished goods

IRN- Inspection release note

MIN- Material issue note

PPS- Pipe preparatory shop & Piping production system

Project Management Group (PMG) & PlanningThis group of engineers is responsible for the procurement of materials as per the requirements of the Client. Once the pipe spools are ready for dispatch, it is the responsibility of this department to communicate with the client & get things done within the stipulated time period.

Role of PMG

This involves 2 different wings, Engineering & Purchase which work together. The Engineering wing is responsible to construct a proper design of the pipe spools as per the requirements & standards set by the client. The Purchase wing then releases a Purchase order as a part of material procurement. The selection of Vendors for the materials is done either by the client, or the vendors are recommended by the officials of LTPC as per previous experience.

On arrival, the materials are directly sent to the stores where a Goods Receipt Note (GRN) is signed. Now as per the design, the PMG department prepares a BOQ (Bill of quantity) based on which, materials are procured from the stores.

The role of PMG again comes into picture when the pipe spools are ready to dispatch. The PMG makes contact with the client asking for their consent regarding how they want the materials to be delivered. PMG also releases MIN (Material Issue note) to the PPS for further processing.

Role of Planning

The primary function of this group is to cater to the needs & complaints of various departments such as Production, Welding, Quality, EHS etc if any flaw in the material gets detected.

EHS DepartmentThis department is responsible for monitoring & ensuring whether all said safety procedures are being followed properly inside the shop floor or not. It sets safe standard procedures to carry out a particular work so that there is no kind of irreparable loss. Some of the rules are:-

1) A person should always walk inside the shop floor wearing safety gadgets such as Safety shoes, helmet & protective goggles.

2) A person is allowed to walk only on the path painted with green & yellow colour inside the shop floor, called as ‘Gang Way’.

3) A person is supposed to maintain certain distance from all kinds of manufacturing processes going on inside the shop floor, in case the person is an outsider.

HIRAC

HIRAC stands for Hazard identification & risk assessment control. This unique thing is rarely seen at any other industry. A HIRAC register is prepared pertaining to each & every process going on inside the shop floor. Related to a particular process like for ex- Blasting, all kinds of possible hazards are first identified & later classified as significant & non-significant as per the criticality of the Hazard. A hazard is anything which has the potential to cause harm to a person. After the categorization of the identified hazards, methods are chalked out to curb them or to reduce them to their lowest level possible.

Proper grading of the hazards is also done before & after the application of the precautionary measures. The risks in doing a particular activity are also analysed & actions are taken accordingly. A HIRAC register is prepared to for each & every activity & is reviewed or revised on a regular basis.

EHS Certifications of LTPC:-

1) OHSAS 18001- Standard for safety2) ISO 14001- Environmental standard3) ISO 9001- Quality standard

Tie-up & Lift-up of spools

Inside the shop floor, certain standard procedures are followed for the lifting-up & tying up of spools. These procedures have been set by the EHS department in order to curb any kind of mishap. Some of the important points for the same are:-

1) For safe lifting up of spools, the crane hook & the spool centre of gravity should be lying on the same line.

2) Sling angle:- It is the angle between the spool & the tied belts/ropes. For safe operation, sling angle should always be greater than 45 degrees.

3) Included angle:- It is the angle between the 2 arms of the tied rope/belt. For safe operation, included angle should be less than or equal to 60 degrees. Lower the included angle, lesser the stress on slings & better is the lifting capacity.

Crane Matrix at LTPCThere are a total of 23 cranes of different make & capacity at LTPC. The crane break-up stands as follows:-

1) Inside shop floor (Bay 1 & Bay 2)- 15 cranes (Electrically operated cranes or EOT’s & Jib cranes)

2) At PPS- 2 cranes (Goliath type)3) FG Yard & open fabrication yard- 6 cranes (Goliath type)

Inside shop floor

1) No. of 10 Tonne (T) cranes- 5 EOT’s of double gudder & 1 EOT of single gudderMake- Two 10 T cranes are of Anupam & rest of them are of ElectroMech

Span- 28.587 m2) No. of 20 T cranes- 3 EOT’s of double gudder

Make- ElectroMechSpan- 28.587

3) No. of 3T cranes- 6 Jib cranesMake- ElectroMech

At PPS

1) 5 T Goliath type A-shaped crane, No.- 1Make- ElectroMechSpan- 7.5 m

2) 7.5 T Goliath type A-shaped crane, No.- 1Make- ElectroMechSpan- 7.5 m

At FG yard & OF yard

1) FG yard- One 7.5 T & one 10 T crane, Make- ElectroMech, Span- 15 m2) OF yard- Two 10 T & two 5 T cranes, Make- Anupam, Span- 8.5 m

Pump house & Compressor houseCompressor house

Type of compressor- Screw type, No.- 3 (1 Working + 2 Standby)

Air pressure- 6 bar

Oil used for filtering of lubricant from air- Servo Oil 68

No. of air receiver tanks- 2

Pump house

Water tank capacity- 1500 Kl (approx.), Treated water comes from the Boiler area.

Ph (potenz of hydrogen) inside shop floor- 7

Pressure of water- 3.5 to 4 kg/cm^2

4 pumps of 1.2 KW each for suction of water from the tank which is further supplied to the softening plant.

2 pumps of 4.5 KW each which sucks the softened water from the tank.

Production Department functionProduction Department is responsible to manufacture spools as per drawings and as per applicable quality standards (i.e. ITP/QAP) and Weekly Production Plan given Production Planning. It covers manufacturing activities of spools from design release to final completion up to readiness for dispatch.

Organization structure

Production department

Manufacturing of spools

3LTPC-PD-FLC006

NCR Management

3LTPC-PD-FL003

Drawing & DCN Management

(Online through PPS)

3LTPC-PD-FLC005

Head- Manufacturing

Production Head

Production co-ordinator

Engineer, Production

Supervisor, Production

Workmen (eg- Operators, Welders

etc)

Rigger/Helper

Pipe schedule

Pipe schedule is nothing but a standard to decide the thickness of the given pipe with the outer diameter (OD) being known to us.

For ex- A given pipe is of 4.5 inch OD then, its thickness can be determined as per SCH (schedule) 30 or 40 whichever is desirable. Pipe schedule is an easy method for determining the pipe thickness.

Fit-up of spools

Fit-up is the pre-fabrication arrangement before welding. Moreover, it is a kind of inspection in which all surfaces and parts of a spool are checked thoroughly before they go for welding process. Fit-up also involves pre-heating so as to ensure that no cracks are formed either on the welded part or heat affected zone (HAZ). Proper alignment of spools is ensured by virtue of cleats and ‘Tack’ welding before the pipe spools undergo joining process. Tools used for fit-up are:-

1) Plumb bob2) Line dori arrangement3) Spirit level4) Measuring Tape5) Angles (Right angle)6) Marking punches7) Measuring scale8) Cleats9) Pipe stand10) Pre-heating burners

There are a few check points for fit-up, after examining these points only will the shop engineer give clearance for welding. The check-points are:-

1) ID (internal diameter) & OD (outer diameter) of surface must be free from all dust & plasma cutting.

2) Grinding of both ID & OD at bevel end (max. 50 mm length) must be done.3) The flange surface should be covered with a metallic tape.4) Ensure that all fitting surface are neat & clean.5) Drawing requirements such as Batch no, Heat no, Material description etc should be

there.

Bend Marking

If the pipe section is required to undergo hot induction bending process then, the post bending heat treatment (PBHT) of bent pipe is done after which it is brought for bend marking in which the dimensions of pipe are thoroughly checked. The dimensions which are checked & calculated are:-

1) ID & OD

2) Thickness of pipe at all sections i.e. straight and bent sections3) Arm 1 & Leg 14) Arm 2 & Leg 25) Hypotenuse of bent pipe6) Bending arc length7) Angle of bend

Ex- Consider the top view of a pipe which has to undergo a 90 deg. Bend, the length of raw material which needs to be supplied for the same is decided on the basis of Arm 1, Arm 2 and Bending Arc length.

Radius of bend= 5D, Here D refers to the outer diameter of pipe

Consider a 90 deg. Bend pipe. Leg 1 refers to the smaller length measured

from the extreme corner of the bend as shown, whereas Leg 2 refers to the

larger length. The dimensions are calculated based on few formulae

which are:-

1) Arm 1= Leg 1- Radius of bend2) Arm 2= Leg 2- Radius of bend3) Bending arc length= [(2π∗Radius∗θ)÷360 ¿ + Shrinkage losses

Here, Ɵ (theta) refers to the angle of bend. 4) Total length= Arm 1+ Arm 2+ Bending arc length

In case the angle of bend is other than 90 deg then, the value of radius of bend also changes.

5) New radius= tan θ2∗Original Radius

Here, original radius means radius at the time of 90 deg bend. This is because as the angle of bend decreases, the pipe spool opens up.

Methods to check the dimensions of the bent pipe are:-

1) Water checking- In this, a thin tube filled with water is used to check the ID & OD of pipe. The tube is fixed on one end of the pipe while another person tries to match the water level inside the tube with ID & OD of the pipe. If the water level matches at the other end then, it means that the checking is successful. This water checking is done

Arm 1 Arm 2Bending arc length

Leg 1

Leg 2

to check whether the bent pipe is on same plane or not. There shouldn’t be any kind of rotation of pipe due to bend.

2) Centre line checking- This is done using measuring tape & right angles. The angles are tightly fixed to the OD of the pipe and then, OD is measured using a tape. A point is marked at half of OD. Another point is marked in the same manner on the straight section of the pipe. The Centre line of pipe is achieved by joining the obtained two points. A very important point to be mentioned is that the centreline of pipe is NEVER measured at the bend section, reason being the ovality of the bend which will yield a variety of readings.

3) The ovality or roundness of the pipe is measured in terms of X & Y co-ordinates using an instrument called Calliper.

4) The thickness of the bent pipe at each & every section is measured using an instrument called D-meter. This uses ultrasonic waves in determining the thickness of pipe. The various sections on the pipe where the thickness is supposed to be measured are coated with grease or any other lubricant so as to prevent the probe of D-meter from getting damaged. The probe sends ultrasonic waves and hence, we get the thickness.

5) Arm 1&2, Leg 1&2, Hypotenuse and Bending arc length are measured with the help of tape and line-dori arrangement.

The bend marking of a spool takes about 30 min. on an average.

COJAFEX Hot Induction Bending Machine

Principle of induction bendingInduction bending uses inductors to locally heat steel by induction. This results in a narrow heat band in the shape to be bent. The shape is firmly held by a clamp at the desired radius, which is mounted on a free pivoting arm. The shape is pushed through the inductor by an accurate drive system which causes the hot section to form the bend at the set radius. The bent part is then cooled by water, forced or still air to fix the bend shape.

The bending process is continuous and highly automated from start to finish.

Areas of application

Induction bends find their way in the following industries:

Petrochemical Chemical Power Generation (conventional and nuclear) Oil and gas (incl. expansion joints) Compressor and pump stations (fluids and gasses) Offshore Shipbuilding Construction

Common material groups which can be bent are:

Carbon steels Low alloyed steels

High alloyed steels

Fine grain steels

Stainless steels Austenitic

Martensitic

Duplex

Special alloys

Samples of steels routinely bent for various industries are:

Offshore Duplex/Super Duplex

Power P91 / P22 / WB36 / P92

Pipe line API 5L X52 / X65 / X70 / X80 – X100

PetrochemicalA106 Grade.B / Grade.C / P1/ P9, A312TP304, TP316

Other Aluminium, Titanium

Major advantages of induction bending are: Cost efficiency. Straight material is less costly than standard components (e.g. elbows) and

bends can be produced faster than standard components can be welded. Elbows can often be replaced by larger radius bends, reducing friction, wear and required

pump capacity.

Induction bending reduces the number of welds in a system.o No welds at the critical points thanks to the tangents. o Less non-destructive testing, saving cost.

Induction bends are stronger than elbows with uniform wall thickness Stock of elbows and standard bends can be greatly reduced. Straight pipe is more readily available than elbows, reducing time to market Bends can be made from the same base material as the straight pipe. Induction bending does not need bend dies or mandrels. A simple clamping/ inductor set

covers a wide range of radii and wall thicknesses Induction bending is a clean process. No lubricants necessary.

In induction bending, AC current is passed through the inductor. Because of varying current there is a change in flux related to bulk pieces of metal, as a result eddy currents are introduced which provide the heating effect thus facilitating the bending process. Inductor is incorporated for heating as it heats the pipe uniformly throughout its thickness. The important parameters to be monitored in the bending machine are:-

1) Intrados (inner wall) temperature2) Extrados (outer wall) temperature3) DBB (distance between bends)4) POB (plane of bending)5) Bending angle6) Pusher speed7) Bending length8) Wall thinning

Machine Name:- Cojafex PB1400RMake:- Cojafex, NetherlandsLead screw (bending arm) motor:- 1445 rpm, 7.5 KWWater pressure:- 6 barAir pressure:- 5 barModes:- Manual & Auto, any mode can be switched at any timeNominal Diameter:- 6”-56” (with pusher insert frame), 6”-32”(without pusher insert frame)Outside Diameter:- 150-1430 mm (with pusher insert frame), 150-820 mm (without pusher insert frame)Wall thickness:- 5-100 mmPipe length:- 0-18350 mm

Straight start:- Refers to the length of the pipe that remains unbent before the first bend is made, max. value is 14000 mmShort clamping:- Pipe is clamped over a length of 460 mm, allowing a minimum straight start of 630 mm.Long clamping:- Pipe is clamped over a length of 860 mm, allowing a straight start of 1030 mm.Intrados temperature range:- 600-1200 deg. CelciusExtrados temperature range:- 600-1200 deg. CelciusDOB (degree of bend):- 0-180 degreesROB (radius of bend):- 550-10200 mmPOB (plane of bend):- (-)360 to 360 (+) deg.Minimum allowable R/D:- 1.5

Pertaining Dangers1) Resulting from machine operation

Bending arm rotation Bending arm clamp open/close Bending arm clamp radius displacement Machine radius displacement Pusher displacement Inductor/heating installation

2) Resulting from manipulation of the pipeMain groups on the machine

0- General1- Bend arm2- Pusher3- Inductor table4- Guide rolls5- Heating installation/open water system6- Hydraulic unit9- Pipe loaderThe various parts of the machine are sorted under these major groups mentioned.

Coding for various partsAC- AC motorAP- air pressure controlAV- air valve

CC- water pressure heating installationCI/CO- heating installation input/outputF- Thermic fuseFR- flow switchFT- flow meterLS- Inductive limit switchMC- motor controllerMG- magnetPC- photo cellPM- linear potentiometerPR- pressure switchPT- pressure sensorPY- pyrometerWV- water valveLocation of remote control units

1) The bridge2) Bending arm clamp3) Head of the machine4) The pusher

Functioning of major parts1) Bending arm/bending arm clamp- It is used to hold the pipe. The pressure at which

pipe is clamped is determined by the wall thickness & the outside diameter of the pipe. Clamp radius, together with the machine radius determines the radius the pipe will be bent at.

2) Support roll- It comes primarily in action during loading in order to make the pipe slide smoothly in the pusher clamp.

3) Lift roll- It acts as a support when the pipe is lifted up.4) Bend roll- It is needed to guide the pipe through the machine & absorb the forces

exerted on the machine by the pipe. Size:- 600 mm diameter 5) Side roll- It is needed to ensure that the pipe will always stay against the bend roll.

Size:- 150 mm diameter 6) Inductors- It is a set of air ring, inductor, quenching ring, nozzle unit

Inductor heats the pipe and is made of Copper (Cu). The quench ring sprays water or air onto the pipe to quench the bent

section. It is a pair of brass or copper half rings. The design is of half ring so that uniform quenching can be done on either sides of the pipe.

Air ring blows air under the inductor to make sure that water stays off the heat band.

The nozzle unit is used to provide additional quench at the extrados of the pipe.

Important facts1) A greater temperature difference between inside & outside radius decreases wall

thinning.2) Higher bending temperature reduces bending forces, leading to lower ovalities.3) A water quench allows for higher bending speed, thus decreasing production time.4) Steels with high Carbon content should preferably be bent with air quench, in order to

prevent cracking at outside radius.5) Air-quench increases ovality as it leads to a wider heat band.6) Lubricants used in Cojafex- Alvania EP2, Omala 150, Tellus T68

Edge preparationTwo different pipe sections are joined via butt weld at LTPC. In order to have a strong joint, the edge preparation of pipes is done i.e. grooves are made at their end sections so as to have a strong weld right from the root. Generally, a gap of 3-4 mm is maintained between the edge prepared sections so that the filler wire used for welding can get inside and form a strong weld. The first 2 passes are performed using GTAW (gas tungsten arc welding) and are termed as ‘Root pass’ & ‘Hot pass’. Further passes of welding are then performed either using SMAW (shielded metal arc welding) or SAW (sub-merged arc welding) depending upon the requirement. Grooves at LTPC- Single V groove, Double V groove (bevel angle:- 30-35 deg, root gap:- 2-4 mm, root face:- 1.5-2.5 mm), J groove, Compound groove (10-20 deg; 10-37.5 deg)

Butt welds

Butt welds are welds where two pieces of metal are to be joined are in the same plane.These types of welds require only some preparation and are used with thin sheet metals that can be welded with a single pass. Common issues that can weaken a butt weld are the entrapment of slag, excessive porosity, or cracking. For strong welds, the goal is to use the least amount of welding material possible. Butt welds are prevalent in automated welding processes, such as submerged-arc welding, due to their relative ease of preparation. When metals are welded without human guidance, there is no operator to make adjustments for non-ideal joint preparation. Because of this necessity, butt welds can be utilized for their simplistic design to be fed through automated welding machines efficiently.

Butt joint geometries

There are many types of butt welds, but all fall within one of these categories: single welded butt joints, double welded butt joint, and open or closed butt joints. A single welded butt joint is the name for a joint that has only been welded from one side. A double welded butt joint is created when the weld has been welded from both sides. With double welding, the depths of each weld can vary slightly. A closed weld is a type of joint in which the two pieces that will be joined are touching during the welding process. An open weld is the joint type where the two pieces have a small gap in between them during the welding process.

V-joints

Single butt welds are similar to a bevel joint, but instead of only one side having the beveled edge, both sides of the weld joint are beveled. In thick metals, and when welding can be performed from both sides of the work piece, a double-V joint is used. When welding thicker metals, a double-V joint requires less filler material because there are two narrower V-joints compared to a wider single-V joint. Also the double-V joint helps compensate for warping forces. With a single-V joint, stress tends to warp the piece in one direction when the V-joint is filled, but with a double-V-joint, there are welds on both sides of the material, having opposing stresses, straightening the material.

J-joints

Single-J butt welds are when one piece of the weld is in the shape of a J that easily accepts filler material and the other piece is square. A J-groove is formed either with special cutting machinery or by grinding the joint edge into the form of a J. Although a J-groove is more difficult and costly to prepare than a V-groove, a single J-groove on metal between a half an inch and three quarters of an inch thick provides a stronger weld that requires less filler

material. Double-J butt welds have one piece that has a J shape from both directions and the other piece is square.

Machines used at LTPC for edge preparation

1) SAFOP TUB-MATIC 1200 CNC Machine Cutting tool:- made of HSS (High speed steel) Make:- SAFOP Hydraulically driven:- 92-95 kg/cm^2 (clamping pressure) Oil grade:- Servo oil (32-64) Insert used for cutting:- CNMG triangular 4235 Centering tool is used to adjust the centre of pipe with the spindle OD range:- 89-1100 mm Thickness:- 15-120 mm Pipe thickness upto 22 mm:- J groove, thickness greater than 22 mm:- V

or Compound groove No. of SAFOP machines:- 2 Has got 2 different motions, longitudinal (Z motion) & tool motion (X). For hardened P91 material, 90 rpm of spindle & 70 mm/min feed rate of

tool. For carbon steel spool, 100 rpm of spindle & 90-95 mm/min feed rate.

Edge preparation in progress.

2) High speed Bevelling machine Make:- Nanjing Auto Electric Operation:- Pipe bevelling/edge preparation Capacity:- 2”-24” (outer diameter) Feed speed:- 0.27-16 mm/min Input power:- 12.1 KW

Inserts used

Turning

C N M G 4 3 2

Shape Clearance Angle Tolerance Groove /

Hole Size (IC) Thickness Radius

Milling

S E K N 4 2 A F T N

Shape Clearance Angle Tolerance Groove

/ HoleSize (IC) Thickness Radius

Wiper Lead Angle

Wiper Clearance

Angle

Cutting Edge

Preparation

Cutting Direction

Shape           

Code Letter Description Diagram Nose AngleA 85° parallelogram   85°B 82° parallelogram   82°

C 80° diamond 80°

D 55° diamond 55°

E 75° diamond 75°

H hexagon   120°

K 55° parallelogram 55°

L rectangle   90°

M 86° diamond 86°

N 55° parallelogram 55°

O octagon 135°

P pentagon 108°

R Round full radius

S Square 90°

T Triangle 60°

V 35° diamond 35°

W Trigon 80°

X sp. parallelogram 85°

Clearance or Relief Angle    

Code Letter Angle DiagramN 0°

A 3°

B 5°

C 7°

P 11°

D 15°

E 20°

F 25°

G 30°

Tolerance            

Code Letter

Corner point(inches)

Thickness(inches)

InscribedCircle (in)

Corner point(mm)

Thickness(mm)

InscribedCircle (mm)

A .0002" .001" .001" .005mm .025mm .025mm

C .0005" .001" .001" .013mm .025mm .025mm

E .001" .001" .001" .025mm .025mm .025mm

F .0002" .001" .0005" .005mm .025mm .013mm

G .001" .005" .001" .025mm .13mm .025mm

H .0005" .001" .0005" .013mm .025mm .013mm

J .002" .001" .002-.005" .005mm .025mm .05-.13mm

K .0005" .001" .002-.005" .013mm .025mm .05-.13mm

L .001" .001" .002-.005" .025mm .025mm .05-.13mm

M .002-.005" .005" .002-.005" .05-.13mm .13mm .05-.15mm

U .005-.012" .005" .005-.010" .06-.25mm .13mm .08-.25mm

Hole / Chip breaker               

Code Letter Diagram Hole Hole Shape Chip breaker Type

Null No None

A  Yes Cylindrical None

B Yes 70-90° double countersink None

D Yes Cylindrical None

E No None

F No Double-sided

G Yes Cylindrical Double-sided

H Yes 70-90° single countersink Single-sided

M Yes Cylindrical, or double countersink Single-sided

N No None

P Yes Cylindrical Hi-double positive

Q Yes 40-60° double countersink None

R No Single-sided

S Yes Cylindrical Hi-double positive

T Yes 40-60° double countersink Single-sided

U Yes 40-60° double countersink Double-sided

W Yes 40-60° double countersink None

Z Yes Cylindrical Double-sided hi-double positive

Size     

ANSI Code No.

Inscribed Circle Size ISO Code No. (metric cutting edge length) by shape code letter of insert

decimal in. fractional in. C D R S T V W

0.5 .0625" 1/16

1.2 (5) .15625" 5/32 S4 04 (4mm) 03 (3mm) 03 (3mm) 06 (6mm)

1.5 (6) .1875" 3/16 04 (4mm) 05 (5mm) 04 (4mm) 04 (4mm) 08 (8mm) 08 (8mm) S31.8 (7) .21875" 7/32 05 (5mm) 06 (6mm)  05 (5mm)  05 (5mm) 09 (9mm) 09 (9mm) 03 (3mm)

2 .25" 1/4 06 (6mm) 07 (7mm) 06 (6mm) 06 (6mm) 11 (11mm) 11 (11mm) 04 (4mm)2.5 .3125" 5/16 08 (8mm) 9mm 07 (7mm) 07 (7mm) 13 (13mm) 13 (13mm) 05 (5mm)3 .375" 3/8 09 (9mm) 11 (11mm) 09 (9mm) 09 (9mm) 16 (16mm) 16 (16mm) 06 (6mm)

3.5 .4375" 7/16 11mm 13mm 11 (11mm) 11 (11mm) 19 (19mm) 19mm 7mm4 .5" 1/2 12 (12mm) 15 (15mm) 12 (12mm) 12 (12mm) 22 (22mm) 22 (22mm) 08 (8mm)

4.5 .5625" 9/16 14mm 17mm 14 (14mm) 14 (14mm) 24mm 24mm 9mm5 .625" 5/8 16 (16mm) 19 (9mm) 15 (15mm) 15 (15mm) 27 (27mm) 27 (27mm) 10 (10mm)

5.5 .6875" 11/16 17mm 21mm 17 (17mm) 17 (17mm) 30mm 30mm 11mm6 .75" 3/4 19 (19mm) 23 (23mm) 19 (19mm) 19 (19mm) 33 (33mm) 33 (33mm) 13 (13mm)

6.5 .8125" 13/16

7 .875" 7/8 22 (22mm) 27 (27mm) 22 (22mm) 22 (22mm) 38 (38mm) 38 (38mm) 15 (15mm)8 1" 1 25 (25mm) 31 (31mm) 25 (25mm) 25 (25mm) 44 (44mm) 44 (44mm) 17 (17mm)

10 1.25" 1-1/4 32 (32mm) 38mm 31 (31mm) 31 (31mm) 54 (54mm) 54 (54mm) 21 (21mm)

1.26" 32 (32mm)

Thickness          

ANSICode No.

ISOCode No.

DecimalValue

FractionalValue

Milli meterValue

.5 (1) - 0.03125" 1/32 0.79mm

.6 T0 0.040" 1.00mm

1 (2) 01 0.0625" 1/16 1.59mm1.2 T1 0.078" 5/64 1.98mm

1.5 (3) 02 0.094" 3/32 2.38mm

T2 0.109" 7/64 2.78mm

2 03 0.125" 1/8 3.18mm2.5 T3 0.156" 5/32 3.97mm3 04 0.187" 3/16 4.76mm

05 0.219" 7/32 5.56mm

4 06 0.25" 1/4 6.35mm5 07 0.313" 5/16 7.9mm6 09 0.375" 3/8 9.53mm

8 0.5" 1/2 12.7mm

Radius     

ANSICode No.

ISOCode No.

DecimalValue

FractionalValue

Milli meterValue

Null Null Wiper flat Wiper flat Wiper flatV M0 0 0 0

0.2 00 0.004" 0.1mm

X 0.004" 0.1mm

0  00 0.004" 0.2mm

0.5 0.008" 0.2mm

Y 0.008" 0.2mm

1 04 0.016" 1/64 0.4mm

05 0.020" 0.5mm

2 08 0.031" 1/32 0.8mm

10 0.040" 1.02mm

3 12 0.047" 3/64 1.2mm4 16 0.062" 1/16 1.6mm5 20 0.078" 5/64 2mm6 24 0.094" 3/32 2.4mm7 29 0.109" 7/64 2.9mm8 32 0.125" 1/8 3.2mm

Wiper Lead Angle        

Code Letter AngleA 45°D 60°K 60°E 75°L 75°P 0°S 75°

Wiper Clearance Angle       

Code Letter AngleC 7°D 15°E 20°F 25-26°G 30°N 0°P 11°

Cutting Edge Preparation     

Code Letter Edge PreparationF SharpE HonedT T-landS honed T-landX special chamfer

Cutting Direction        

Code Letter DirectionR right-hand cutting onlyL left-hand cutting onlyN both right-hand and left-hand cutting

Bandsaw Cutting Machine

At LTPC, the cutting of pipe spools is done using state-of-the art bandsaw cutting machine. Depending upon the capacity of the machine, the cutting blade moves over 2 or 4 rollers and forms a rectangular band. Because of hydraulically driven piston cylinder system with oil as lubricant, the bandsaw slowly & steadily comes down thus cutting the marked pipe section.

The teeth of blade is made of HSS (high speed steel) and rest of the blade body is made up of spring steel, which is also used in making suspension system of automobiles. HSS and spring steel are together joined with the help of Electron beam welding (EBM).

Types of bandsaw machines at LTPC

1) ITL Bandsaw machine Make:- ITL No. of machines:- 1 Operation:- Pipe cutting (straight i.e. 90 degrees) Blade pressure:- 48-50 kg/cm^2 4 roller bearings rotate along with the blade Minimum diameter of pipes:- 89 mm Maximum diameter of pipes:- 1260 mm Maximum weight of pipe:- 12000 kg Cutting speed:- 20-100 m/min Saw motor:- 25 HP, 1445 rpm Hydraulic motor:- 3 HP, 1440 rpm Hydraulic Oil:- Servo oil 68 Blade size:- 10900 (length) mm by 67 (width) mm by 1.6 (thickness) mm

S.No. Blade Type Material Grade Pipe Thickness

1) 2/3 TPI (teeth per inch)

M-42/M-51 10-25 mm

2) 1.4/2 TPI M-42/M-51 25-50 mm

3) 0.75/1.25 TPI M-42/M-51 >50 mm

Here, as the thickness of pipe increase, the no. of teeth per inch (TPI) decreases. Slow cutting rate is preferred at higher thickness so as to prevent the cutting blade from frequent failure, that’s why low TPI at higher thickness. It also reduces the wear & tear of teeth.

ITL feed rate (standard)

Scale mm/min

1 0

2 4

3 7

4 10

5 16

6 22

7 30

8 37

9 40

10 58

In case of P91 material, speed scale along the thickness section- 2 (4 mm/min), speed scale along the hollow section- 3 (7 mm/min)

In case of carbon steel material, speed scale along the thickness section- 2 (4 mm/min), speed scale along the hollow section- 4 (10 mm/min)

Cutting lubricant:- Blasocut 4000 strong (Make- Blaser Swisslube) No. of clamps:- 4 Minimum cuts if blade is operated at prescribed speed:- 60-70 cuts

2) Make:- Nanjing Auto Electric Co. LTD. Operation:- Pipe cutting No. of roller bearings:- 2 Capacity:- 2”-24” (outer diameter)

Motor:- 5.5 KW, 1440 rpm No. of machine:- 1

In both types of cutting machines, a vertical column is attached to the blade-roller set up. This column is used as a scale cum sensor and also used to protect the unnecessary breakage of the blade. The OD of the pipe is initially marked on this vertical column, the bandsaw-bearing roller setup starts coming down as the cutting of pipe commences. A sensor also moves along the column. As soon as the sensor reaches the bottom most marked position on the column, an immediate signal is sent to another sensor which immediately takes the entire set up upwards, thus preventing the blade failure. This column is used to ensure that the pipe has been cut completely, as the bottom section of the pipe being cut is mostly not clearly visible. The column-sensor system also prevents the blade from touching the machine bed.

Bi-metal bandsaw joining process, Electron beam welding

Electron beam welding (EBW) is a fusion welding process in which a beam of high-velocity electrons is applied to two materials to be joined. The workpieces melt and flow together as the kinetic energy of the electrons is transformed into heat upon impact. EBW is often performed under vacuum conditions to prevent dissipation of the electron beam.

Electrons are elementary particles possessing a mass m = 9.1 · 10−31 kg and a negative electrical charge e = 1.6 · 10−19 C. They exist either bound to an atomic nucleus, as conduction electrons in the atomic lattice of metals, or as free electrons in vacuum.

Free electrons in vacuum can be accelerated, with their orbits controlled by electric and magnetic fields. In this way narrow beams of electrons carrying high kinetic energy can be formed, which upon collision with atoms in solids transform their kinetic energy into heat. Electron beam welding provides excellent welding conditions because it involves:

Strong electric fields, which can accelerate electrons to a very high speed. Thus, the electron beam can carry high power, equal to the product of beam current and accelerating voltage. By increasing the beam current and the accelerating voltage, the beam power can be increased to practically any desired value.

Using magnetic lenses, by which the beam can be shaped into a narrow cone and focused to a very small diameter. This allows for a very high surface power density on the surface to be welded. Values of power density in the crossover (focus) of the beam can be as high as 104 – 106 W/mm2.

Shallow penetration depths in the order of hundredths of a millimeter. This allows for a very high volumetric power density, which can reach values of the order 105 – 107 W/mm3. Consequently, the temperature in this volume increases extremely rapidly, 108 – 1010 K/s.

The effectiveness of the electron beam depends on many factors. The most important are the physical properties of the materials to be welded, especially the ease with which they can be melted or vaporize under low-pressure conditions. Electron beam welding can be so intense that loss of material due to evaporation or boiling during the process must be taken into account when welding. At lower values of surface power density (in the range of about 103 W/mm2) the loss of material by evaporation is negligible for most metals, which is favorable for welding. At higher power density, the material affected by the beam can totally

evaporate in a very short time; this is no longer electron beam welding; it is electron beam machining.

Blasting booth & operation

Blasting of pipe spools is done before painting operation as a part of surface cleaning and removal of dust particles. Blasting operation ensures a stable coating of paint on the pipe spools. The operation is performed using pressurized air.

Materials used for blasting:- Cu (copper) slag, Grits, Shots, Garnet.Garnet- Used only for SS (stainless steel) spools & looks like sandGrit- Triangular shaped (1 mm size) of grade G40 & G25 at LTPC, can be used on Carbon steel (CS) as well as Alloy steel (AS) spools.Shots- Made of iron scrap & are round in shape (1.5 mm size), can be used on both CS and AS spools.Cu slag- Use & throw material, can be used on both CS & AS spools

Blasting shop make:- Redemaco Engg. Pvt. Ltd. Blast room size:- 15 m (length) by 7 m (width) by 6 m (height) Blast nozzle:- 2 nos. (Tungsten carbide lined), orifice diameter- 9.5 mm Compressed air:- 40-50 CMPH (miles per hour) i.e. around 6.5 bar pressure Load capacity:- 15 Tonnes (T) Cleaning capacity:- 6-8 sq./hour/nozzle Blasting system:- Remote controlled blast hopper with pressure vessel, mushroom

valve, exhaust & outlet metering valve & mixing tube. No. of blasting shops:- 2

Painting booth & operation

Painting of pipe spools is done once they are done with blasting operation. This ensures a stable coating of paint over the spool. Pipe spools are painted with a variety of paints as per the demand from the client and ability of the spool to sustain a certain value of temperature & pressure in the area where the spool will be roped in for use. The main purpose of painting operation is to protect the spools from rusting & corrosion.

Painting shop make:- Redemaco Engg. Pvt. Ltd. Paint shop size:- 15 m (length) by 7 m (width) by 6 m (height) Spray painting equipment:- Model- Graco NXT Xtreme 50:1 Maximum operating pressure:- 359 bar (outlet), 7 bar (inlet)

Recommended paint mix:- 50:1 Outlet per cycle:- 250 cc Air filter:- 10 micron (mesh size) No. of painting shops:- 2 Method of paint application:- Air spray (airless gun), roller, brush Thickness of paint:- 20-25 microns (dry) & 100-125 microns (wet) for single coating Type of paint used:- Red oxide (red colour), Aluminium paint (grey colour) All surfaces should be clean, dry & free from contamination before painting starts. Painting is not required on SS (stainless steel) spools as they are already corrosion

resistant due to excessive Chromium (Cr) content. Masking tapes are used at the prepared edges of pipe spools so as to distinguish the

portion to be welded from rest of the portion of pipe. Tape is used till 4” (maximum) from the edge and sometimes till 2”-3”.

Another paint is applied over masking tape to distinguish the weldable portion.Weldable primer (black in colour), Zinc (grey colour)

Fabrication of Alloy steel (AS), Carbon steel (CS) & Stainless steel (SS) spools

Parameters CS Spool (SA106) AS Spool (P91) SS Spool (Austenitic) 304

C (Carbon) content

Cr (Chromium) content

Mo (Molybdenum content)

0.1-0.3%

Not required

Not required

0.07-0.13%

9%

1%

<0.08%

18-32%

Very less

Pre-heating temperature (deg.

Celsius)

Thickness upto 19 mm:- 20-25 deg.

Thickness greater than 19 mm:- 80-100

deg.

225 deg. Not required

Inter-pass temperature (deg.

Celsius)

300 deg. 325 deg. 175 deg.

Post-heating temperature (deg.

Celsius)

Not required 350-400 deg. Not required

Soaking temperature in PWHT (deg.

Celsius)

625 + 15 deg.

625 – 15 deg.

745-770 deg. 720-725 deg.

Blasting Cu slag, Grits, Shots can be used for surface cleaning

Cu slag, Grits, Shots can be used for surface cleaning

Use of only garnet is allowed

Contamination Less contamination Less contamination High Contamination

Painting Required, either red oxide or Al paint

Required, either red oxide or Al paint

Not required

Observations & Inference

1) With the diffusion of alloying elements and increase in the content for same, there is an increase observed in all kinds of temperatures such as pre-heat, inter-pass, post-heat & PWHT. This is because of varying mechanical properties of alloying elements which contribute in increasing the hardness & strength of the material. Greater the hardness, higher is the temperature.

2) Pre-heating and Post-heating processes are not required in case of SS (Stainless steel) spools. The main purpose of pre-heat and post-heat is to avoid the formation of cracks in the welded portion and Heat affected zone (HAZ). H2 (Hydrogen gas) diffusion plays an important role in crack formation. The coating of the pipe spool (when they come as raw material) is such that it has an affinity to absorb the moisture present in the environment. Now during welding process, because of the extremely high Arc temperature, the decomposition of Hydrogen (H2) & Oxygen (O2) occurs and thus, hydrogen diffuses into the welded area causing embrittlement. In case of SS spools, the microstructure (Austenitic) is such that it doesn’t get affected much because of Hydrogen diffusion. Therefore, there is no need of any pre-heating or post-heating.

3) The contamination risk in case of SS spools is very high. Once they get contaminated by foreign particles, the passive Chromium oxide (Cr2O3) layer will get weared off thus leading of rusting of pipes. As a precautionary measure, the fabrication of SS spools is done in an Enclosure.

4) Painting is not required in case of SS spools as they are already corrosion resistant due to high Chromium content.

5) In case of CS spools, post-heating is not required compared to AS spools. This is because of the fact that CS has got a microstructure of α-ferrite + pearlite and AS has got a microstructure of martensite (P91) & bainite P92). As we know, martensite & bainite are relatively harder than ferrite-pearlite matrix, so more heating is required to remove the stresses developed due to welding.

SS spools in Enclosure

As the fabrication of SS pipes are carried out in an enclosure at LTPC due to high risk of contamination, certain good engineering practices are adopted for the same purpose. The practices are:-

1) Use of identified Grinding Wheels/Wire Brushes on SS jobs.2) Handle SS jobs with clean Nylon Ropes/Belts/PU Coated Chain Hooks.3) Use cotton gloves for handling SS components.4) Avoid direct contact of SS and CS materials.5) Use shoe covers while working on SS Plates/Pipes.6) Cover SS jobs when not in use.7) Use low-chloride chalks, markers, thermal chalks on SS jobs.8) Use plastic- covered wooden pieces or Teflon block for resting SS components.9) Use PVC Pallet for storing SS fittings. 10) Do not use metallic tools, grinding wheels etc. once used on CS jobs.

Cleats & Tack welding

Cleats and tack welding are pushed into service before the commencement of welding process. Cleats are nothing but trapezoidal clamps used to hold the two jobs which are required to be welded, so as to curb any sort of misalignment. Cleats are mostly made up of the same material on which the welding is supposed to be done. The number of cleats to be used depends upon the OD of the job. The cleat matrix is as follows:-

1) 18” (job OD):- 4 cleats2) 18”-24”:- 6 cleats3) 24”- 3 m:- 8 cleats4) 3 m and above:- depends upon arc distance on the job OD

Once the jobs get properly aligned and are done with the initial GTAW process (root pass & hot pass), cleats are slowly removed either by hammering action or by grinding.

Portion of cleat to be kept inside the job groove:- 0.5-0.66 times the job thickness

Tack Welding is a GTAW process and is used to fix the cleats to the base metal. It doesn’t involve any pass, it involves spot welds. A fillet weld of 6 mm is used to fix the cleats.

Pipe Preparatory Shop (PPS) and Colour coding

PPS

PPS receives pipe material from store. It cuts pipe in required length and makes edge preparation. After making full kit (Pipe and fittings), PPS delivers material to shop.

Preparatory activities like marking, cutting, edge preparation and grinding

Standard Colour Coding of pipe material identification

1) Plain CS:- no colour2) Low temperature CS:- Yellow3) Carbon steel (NACE):- Green4) SS Grade 316/316L:- Blue5) SS Grade 321/321L:- Blue + Yellow6) SS Grade 347/347L:- Blue + Green7) SS Grade 304/304L:- Black8) SS Grade 317/317L:- Blue + Black9) SS Grade (NACE):- Blue + Red10) Alloy steel grade P91:- Red11) Alloy steel grade P92:- Red + Green12) Alloy steel grade P22:- Yellow + Green13) Alloy steel grade P11/P12:- White + Red14) Alloy steel grade P36/WB36:- Yellow + Red15) Duplex SS:- White + Blue

Fittings & Forgings

Fittings & Forgings are also a part of pipe spool. Fittings are given to provide a branch connection for other pipes. Whereas, forgings are given either to connect large pipes to small pipes or to install some kind of measuring instrument.

At LTPC, fittings used:- Elbows, Tees, Reducers, Cap.

Forgings used:- Weldolet, Sockolet, Threadolet, Thermowell, Flanges etc.

Fittings

A fitting is used in pipe systems to connect straight pipe or tubing sections, to adapt to different sizes or shapes, and for other purposes, such as regulating or measuring fluid flow. The term plumbing is generally used to describe conveyance of water, gas, or liquid waste in ordinary domestic or commercial environments, whereas piping is often used to describe high-performance (e.g. high pressure, high flow, high temperature, hazardous materials) conveyance of fluids in specialized applications. The term tubing is sometimes used for lighter-weight piping, especially types that are flexible enough to be supplied in coiled form.

Elbow

Short radius or regular 45° elbow (copper sweat)

Long radius or sweep 90° elbow (copper sweat)

An elbow is a pipe fitting installed between two lengths of pipe or tubing to allow a change of direction, usually a 90° or 45° angle, though 22.5° elbows are also made. The ends may be machined for butt welding, threaded (usually female), or socketed, etc. When the two ends differ in size, the fitting is called a reducing elbow or reducer elbow.

Elbows are categorized based on various design features as below:

Long Radius (LR) Elbows – radius is 1.5 times the pipe diameter Short Radius (SR) Elbows – radius is 1.0 times the pipe diameter 90 Degree Elbow – where change in direction required is 90° 60 Degree Elbow – where change in direction required is 60° 45 Degree Elbow – where change in direction required is 45°

A 90 degree elbow is also called a "90 bend" or "90 ell". It is a fitting which is bent in such a way to produce 90 degree change in the direction of flow in the pipe. It is used to change the direction in piping and is also sometimes called a "quarter bend". A 90 degree elbow attaches readily to plastic, copper, cast iron, steel and lead. It can also attach to rubber with stainless steel clamps. It is available in many materials like silicone, rubber compounds, galvanized steel, etc. The main application of an elbow (90 degree) is to connect hoses to valves, water pressure pumps, and deck drains. These elbows can be made from tough nylon material or NPT thread.

A 45 degree elbow is also called a "45 bend" or "45 ell". It is commonly used in water supply facilities, food industrial pipeline networks, chemical industrial pipeline networks, electronic industrial pipeline networks, air conditioning facility pipeline, agriculture and garden production transporting system, pipeline network for solar energy facility, etc.

Most elbows are available in short radius or long radius variants. The short radius elbows have a center-to-end distance equal to the Nominal Pipe Size (NPS) in inches, while the long radius is 1.5 times the NPS in inches. Short elbows are widely available, and are typically used in pressurized systems.

Long elbows are typically used in low-pressure gravity-fed systems and other applications where low turbulence and minimum deposition of entrained solids are of concern. They are readily available in acrylonitrile butadiene styrene (ABS plastic), polyvinyl chloride (PVC) for DWV, sewage and central vacuums, chlorinated polyvinyl chloride (CPVC) and copper for 1950s to 1960s houses with copper drains.

Reducer

Reducer fittings, bronze threaded (left) and copper sweat (right)

A reducer allows for a change in pipe size to meet hydraulic flow requirements of the system, or to adapt to existing piping of a different size. Reducers are usually concentric but eccentric reducers are used when required to maintain the same top- or bottom-of-pipe level. Material – ASTM A234 WPB

Tee

Pipe tee (copper sweat)

A tee is the most common pipe fitting. It is available with all female thread sockets, all solvent weld sockets, or with opposed solvent weld sockets and a side outlet with female threads. It is used to either combine or split a fluid flow. It is a type of pipe fitting which is T-shaped having two outlets, at 90° to the connection to the main line. It is a short piece of pipe with a lateral outlet. A tee is used for connecting pipes of different diameters or for changing the direction of pipe runs. They are made of various materials and available in various sizes and finishes. They are extensively used in pipeline networks to transport two-phase fluid mixtures. They are categorized as:

Equal Unequal

When the size of the branch is same as header pipes, equal tee is used and when the branch size is less than that of header size, reduced tee will be used. Most common are tees with the same inlet and outlet sizes. Some of the industrial tees are Straight Tee, Reducing Tee, Double Branch Tee, Double Branch Reducing Tee, Conical Tee, Double Branch Conical Tee, Bullhead Tee, Conical Reducing Tee, Double Branch Conical Reducing Tee, Tangential Tee, and Double Branch Tangential Tee.

The above tees are categorized on the basis of their shapes and structure. They can also be classified on the basis of the application they are required to perform.

Cap

Pipe cap (copper sweat)

A type of pipe fitting, usually liquid or gas tight, which covers the end of a pipe. A cap is used like plug, except that the pipe cap screws or attaches on the male thread of a pipe. A cap may have a solvent weld socket end or a female threaded end and the other end closed off. In plumbing systems that use threads, the cap has female threads. Industrial caps can be round, square, rectangular, U-shaped, I-shaped and may have a round hand grip or a flat hand grip.

Forgings

Weldolet is the most common of all branch connections, and is welded onto the outlet pipe. The ends are bevelled to facilitate this process, and therefore the weldolet is considered a butt-weld fitting. Weldolet's are designed to minimize stress concentrations and provide integral reinforcement.

 

Sockolet utilizes the basic Weldolet however the branch affixes by way of a socket inside the olet. The bore matches the outlet bore, and the existence of a counter bore roughly the size of the OD of the outlet provides a socket where the pipe can sit, facilitating installation and welding. The Sockolet is considered a socket fitting, and manufactured in 3000#, 6000# and 9000# classes.

Threadolet utilizes the basic Weldolet however the branch affixes by way of a thread just inside the top of the olet. The bore matches the outlet bore, and the existence of this threading facilitates installation, as no welding is necessary. The Threadolet is considered a threaded fitting, and manufactured in 3000# and 6000# classes.

Thermowells are tubular fittings used to protect temperature sensors installed in industrial processes. A thermowell consists of a tube closed at one end and mounted in the process stream. A temperature sensor such as a thermometer, thermocouple or resistance temperature detector is inserted in the open end of the tube, which is usually in the open air outside the process piping or vessel and any thermal insulation. The process fluid transfers heat to the thermowell wall, which in turn transfers heat to the sensor. Since more mass is present, the sensor's response to process temperature changes is delayed.

Cutting of Trunnion section

x=[ (branch ID )2 ]÷ [Header OD ×4 ]

  The portion marked with ‘x’ is required to be removed from the

  trunnion section which is connected to mother/header pipe. A

  semi-circular curvaceous profile is to be obtained. The value of

  ‘x’ obtained from the formula thus provides a breakthrough in

  Forming the required profile. The profile is cut henceforth.

Radial Drilling Machine No. of machines:- 2 Model no:- BR-7524 Make:- Batliboi Private Limited, Udhna, Surat

x

Differences between SAFOP EP and LATHELATHE

1) Job rotated while tool is stationery with cross travel2) Headstock and Tailstock both are present3) No need of centring when 3 jaw chuck is used (self-centred)4) Multi operations can be done (Drilling, boring etc.)5) Feed of tool has to be given manually adjusted6) Coolant is used 7) Chuck used to hold work8) In manual lathe machine difficult to achieve better finish with more accuracy. 9) Non circular jobs can also be machined by use of 4 jaw chuck

SAFOP EDGE PREPARATION MACHINE

1) Job is held stationery and tool is rotated2) Only Headstock is present3) Cantering of work is necessary4) Only edge preparation –facing and id machining up to 100 mm can be done5) Feed of tool is CNC controlled6) Coolant is not used (So machine is designed for dry cutting. So generated heat is

taken by chips-dark blue chips to increase insert life)7) Hydraulic clamp used to hold work8) Better finish and accuracy due to CNC operation9) Only circular pipes are machined

Cycle time study for Alloy steel & Carbon steel spoolsCarbon Steel

SPOOL DETAILS

LTC, P.O.NUMBER:EPC/EM1/21000-48009/JKCC

SPOOL NO. - SPL-M4-104-006-SP-24

PROJECT: 2X660 MW SHREE SINGAJI TPP (STAGE-II)

CLIENT: MPPGCL

MATERIAL: SA 106 Gr. C

OD: 460 mm X THK: 60 mm

LENGTH: 7835 mm

LENGTH MEASUREMENT DATE: 10/6/2016Spool no. SPL-M4-104-006-SP-24 Project: MALWAMaterial CS Size Ø460x60 mm thick

Sr. No. Activity name Starts End Total time

1 Locating & identifying the pipe 08:15 08:22 00:07

2 Length marking with whitener 08:22 08:27 00:05

Total time 00:12Tools Used:

1) Measuring Tape2) Right Angle3) Whitener4) Drawing

DATUM MARKING Date: 11/6/2016Spool no. SPL-M4-104-006-SP-24 Project: MALWA

Material CSSize Ø460x60 mm

thick

Sr. No. Activity name Starts End Total time

1 Loading 16:30 16:40 00:10

2 Drawing analysis and centre line marking 16:40 16:5

0 00:10

3 Marking datum point 16:50 16:55 00:05

4 Transferring points to side 16:55 17:10 00:15

Total time 00:40

Tools Used:

1) Surface plate2) Spirit level3) Water level pipe4) Set squares5) Measuring tape6) Line Dori 7) Stand8) Chalk9) Divider

LOADING Date: 10/6/2016Spool no. SPL-M4-104-006-SP-24 Project: MALWAMaterial CS Size Ø460x60 mm thickSr. No. Activity name Starts End Total time

1 Belt Wrapping 12:00 12:02 00:022 Centre Setting 12:02 12:05 00:033 Job Lifting 12:05 12:15 00:104 Placing 12:15 12:17 00:025 Belt Unwrapping 12:17 12:20 00:03

Total time 00:20

UNLOADING Date: 10/6/2016Spool no. SPL-M4-104-006-SP-24 Project: MALWAMaterial CS Size Ø460x60 mm thickSr. No. Activity name Starts End Total time

1 Belt Wrapping 12:40 12:42 00:022 Centre Setting 12:42 12:44 00:023 Job Lifting 12:44 12:56 00:124 Placing 12:56 12:58 00:025 Belt Unwrapping 12:58 13:00 00:02

Total time 00:20

Tools Used:

1) 10T EOT crane 2) 10T nylon belt3) Supports4) Crane controller remote

CUTTING Date: 10/6/2016Spool no. SPL-M4-104-006-SP-24 Project: MALWA

Material CSSize Ø460x60 mm thick

Sr. No. Activity name Starts End Total time1 Loading 14:00 14:20 00:102 Setting machine and parameters 14:20 14:30 00:103 Cutting 14:30 15:30 01:004 Unloading 15:30 15:50 00:20

Total time 01:40

Tools Used:

1) Band Saw cutting machine2) Band saw cutting blade3) Stand

Sr no. Parameters Actual Observed1 Blade type 2/3 TPI Ok2 Material Grade M-42 OK3 First cut feed 2(4) mm/min 24 First cut speed 20 19.95 Further cuts feed 3(7) mm/min 56 Further cuts feed 25 24.57 Wheel pressure 3-4Mpa 48 Coolant Swisslube Ok

EDGE PREPARATION 13-06-2016Spool no. SPL-M4-104-006-SP-24 Project: MALWA

Material CSSize Ø460x60 mm

thickSr. No. Activity name Starts End Total time

1 Loading & setting 18:10 18:25 00:152 Centring 18:25 18:35 00:103 Facing major 18:35 18:39 00:044 Facing check 18:39 18:41 00:025 Facing final 18:41 18:43 00:026 Edge preparation OD 18:43 18:55 00:127 Edge preparation ID 18:50 19:00 00:10

Total time 00:55

Tools Used:

1) SAFOP Edge preparation machine2) Centring tool3) Cutting tool4) Hydraulic clamps5) Electronic Jack6) EOT crane7) V- block Support (Ø 460- Ø760)

Sr no. Parameters observed

1 Hydraulic Clamp pressure 92kg/cm^2

2 Electronic jack pressure 450kg/cm^2

3 groove profile J (20,5)

4 Cutting tool used 5-6

Fit up-first trunnion section DATE: 13/6/2016Spool no. SPL-M4-104-006-SP-24 Project: MALWA

MATERIAL CS

Size Ø460x60 mm thick

Sr no. Activity Starts End Total time1) Fit-up trunion and mother pipe 09:25 10:05 00:40 2) Marking centres on base plate 10:05 10:15 00:153) Grinding both the parts 10:15 10:30 00:15

4)Alignment of base plate and

trunnion 10:30 10:35 00:05

5)Tack weld of trunnion and base

plate 10:35 10:50 00:15

6) Fit up check 15:45 15:55 00:15Total time 01:30:00

Fit up-second trunnion section Date: 13/6/2016Spool

no. SPL-M4-104-006-SP-24 Project: MALWA

Material CSSize Ø460x60 mm

thickSr. No. Activity name Starts End Total time

1) Fit-up trunion and mother pipe 11:00 11:20 00:402) Marking centres on base plate 11:30 12:00 00:303) Grinding both the parts 12:00 12:15 00:15

4)Alignment of base plate and

trunnion 15:15 15:35 00:20

5)Tack weld of trunnion and base

plate 15:35 15:40 00:05

6) Fit up check 15:45 11:55 00:15Total time 02:10:00

Tools Used:

1) Measuring Tape2) Thread3) Stand4) Steel Scale5) Spirit level6) Chalk7) IPad- to check drawing and calculate slope8) Drawing9) Cleat10) Overhead Crane11) GTAW welding tools12) Rod to maintain root gap 3-4 mm

Parameters to be checked

S.no Parameters Remark Tool used

1 Spool No. Validated Visually

2 Material CS validated -

3 Internal diameter and thickness Validated Measuring tape

4 Orientation from drawing Validated Template

5 Distances mentioned in drawing Validated Line dori setup

7 Root gap Validated 4mm 4mm dia. tongs

8 No. of cleats 8 visually

WELDING (GTAW) Date: 14/6/2016Spool no. SPL-M4-104-006-SP-24 Project: MALWA

Material CSSize Ø460x60 mm

thickSr. No. Activity name Starts End Total time

1) Loading 12:05 12:15 00:102) Purging setup 12:15 12:25 00:103) Miller machine setup 12:25 12:55 00:304) Pre Heat(100°C) 12:55 14:25 01:305) Root pass (0-180°C) 14:25 15:00 00:356) Root pass (180-360°C) 15:00 15:30 00:307) second pass 16:00 16:50 00:50

Total time 03:20

Tools Used:

1) Tungsten Electrode2) ER-70S2 Filler Wire3) DC Power Supply4) Argon Gas5) Burner (natural gas)6) Gloves7) Welding helmet8) Thermochalk 100 and 350C9) Cobalt glass shield

Sr no. Parameters Actual Observed1 Pre-heat Temperature 100 Thermochalk ok2 Inter-pass Temperature 350 Thermochalk ok3 Filler wire ER-70S2 Ok

4 Material CS Ok5 Welding position 5G Ok7 Consumable diameter 2.4 mm Ok8 Current 70-175 A 1209 Voltage 8-15V 1010 Argon gas flow rate 8 to 15 lpm Ok11 Current and polarity DCEN Ok12 Speed/Bead length 60 60

WELDING (SMAW) DATE: 15/06/2016Spool no. SPL-M4-104-006-SP-24 Project: MALWA

MATERIAL CS

Size Ø460x60 mm thick

Sr no. Activity Starts End Total time1 Welding ( SMAW ) 1 14:00 14:20 00:20

Grinding 14:25 14:30 00:052 Welding ( SMAW ) 2 14:40 15:10 00:30

Grinding 15:20 15:23 00:033 Welding ( SMAW ) 3 15:35 16:05 00:30

Grinding 16:10 16:14 00:044 Welding ( SMAW ) 4 17:00 17:30 00:30

Grinding 17:35 17:39 00:045 Welding ( SMAW ) 5 10:00 10:30 00:30

Grinding 10:45 10:49 00:046 Welding ( SMAW ) 6 11:45 12:15 00:30

Grinding 12:20 12:25 00:057 Welding ( SMAW ) 7 14:10 14:40 00:30

Grinding 15:00 15:05 00:05

8Welding ( SMAW ) 8 (final

layer) 16:00 17:00 01:009 Grinding and brush up 10:30 10:45 00:1510 Welding for 2nd trunion 07:3611 welding base plate-1 00:1512 welding base plate-2 00:15

Total time 15:57:00

Tools Used:

1) Millers induction preheating machine2) Electrode wire3) DC supply

4) Welding tools5) Grinding machine6) Chisel7) Welding helmet8) Glass wool9) Thermocouples10) Argon gas11) Circular metal discs

MAGNETIC PARTICLE TESTING Date: 18/6/2016Spool no. SPL-M4-104-006-SP-24 Project: MALWA

Material CSSize Ø460x60 mm

thickSr. No. Activity name Starts End Total time

1 Testing 23:10 23:20 00:102 Defects check 23:30 23:35 00:05

Total time 00:15

Tools Used:

1) Magnetic particle liquid mixture (5000ml water with 50g 9CD and 50g 12AD)2) Yoke machine3) Chalk4) Spray bottle

DIE PENETRANT TEST Date: 18/6/2015Spool no. SPL-M4-104-006-SP-24 Project: MALWA

Material CSSize Ø460x60 mm

thick

Sr. No. Activity nameStart

s End Total time in Minutes1 Cleaning of Spool 14:10 14:15 00:052 Applying DIE 14:15 14:18 00:033 Waiting for DIE to absorb 14:18 14:23 00:054 Cleaning of DIE 14:23 14:25 00:025 Applying Developer 14:25 14:28 00:036 Examination for defects 14:28 14:33 00:05

Total time 00:23

Tools/Materials Used:

1) Die/Penetrant2) Developer3) Cleaning Agent4) Dry cotton

BEFORE STRESS RELIEVING RADIOGRAPHIC TESTING Date: 20/6/2015

Spool no. SPL-M4-104-006-SP-24 Project: MALWA

Material CSSize Ø460x60 mm

thick

Sr. No. Activity nameStart

s EndTotal time in

Minutes1 Loading Pipe to RT Enclosure 22:10 22:25 00:152 Setup 23:40 23:55 00:153 RT 00:30 00:37 00:07 4 Developing  09:00 09:08 00:085 Stop bath 09:08 09:09 00:016 Fixing 09:09 09:16 00:077 Running water 09:16 09:20 00:048 Soap solution 09:20 09:25 00:05

Total time 01:02

Tools Used:

1) Radiation source2) Film3) IQI4) Crank Case5) Lead Box6) Developer7) Stop Bath8) Fixer9) Wetting Agent10) Soap solution

Parameters Observed1 Isotope used for radiation Iridium 1922 Type of RT Panoramic3 Source side/Film side Source side4 Film size 15x6”5 Film type AGFA D7

6 No. of films used 97 Developing temperature 20C

8 IQI type ASTM 1C

PWHT(Resistance Heating) Date: 22/6/2016Spool no. SPL-M4-104-006-SP-24 Project: MALWA

Material CSSize Ø460x60 mm

thick

Sr. No. Activity name Starts End Total time

1 Loading 10:15 10:35 00:202 Thermocouple mounting 14:00 14:15 00:153 NiChrome wire setup 14:15 15:00 00:454 Stress relieving 16:00 21:00 05:005 Soaking 21:00 22:00 01:006 cooling upto 300C 22:00 02:00 04:007 left in glass wool 02:00 04:00 02:00

Total time 13:20:00

Tools Used:

1) Crane2) Resistance heating machine3) Thermocouple4) Nichrome wire5) Glass wool6) Capacitor discharge welding machine7) Recorder8) Support

Sr no. Parameters Actual Observed1 Loading temperature 300 Room temperature2 Rate of heating 80C/hr OK3 Soaking temperature 625C OK4 Rate of cooling 80C/hr OK5 Number of thermocouples elbow 6

nozzle 3

AFTER STRESS RELIEVING RADIOGRAPHIC TESTING Date: 23/6/2015Spool no. SPL-M4-104-006-SP-24 Project: MALWA

Material CSSize Ø460x60 mm

thick

Sr. No. Activity nameStart

s EndTotal time in

Minutes1 Loading Pipe to RT Enclosure 15:30 15:45 0:152 Setup 3:00 3:25 0:253 RT 3:25 3:35 0:10 4 Developing  09:00 09:08 00:085 Stop bath 09:08 09:09 00:016 Fixing 09:09 09:16 00:077 Running water 09:16 09:20 00:048 Soap solution 09:20 09:25 00:05

Total time 01:15

Parameters Observed1 Isotope used for radiation Iridium 1922 Type of RT Panoramic3 Source side/Film side Source side4 Film size 15x6”5 Film type AGFA D76 No. of films used 97 Developing temperature 20C8 IQI type ASTM 1C

FINAL DIMENSIONS CHECK Date: 27/6/2016Spool no. SPL-M4-104-006-SP-24 Project: MALWA

Material CSSize Ø460x60 mm

thickSr. No. Activity name Starts End Total time

1 Labelling/Tag Preparation 14:30 14:40 00:10

2 Levelling of Spool 14:10 14:15 00:053 Measurement of Spool 14:15 14:30 00:154 Quality/TPI 14:40 14:55 00:15

Total time 00:45

Sr no. Parameters Actual Observed1 Orientation check Template Ok2 Length measurement

Major length 7835 78343 Inner Diameter

X 460 460.5Y 460 460.7

SHOT BLASTING DATE:28/6/2016Spool no. SPL-M4-104-006-SP-24 Project: MALWA

MATERIAL CSSize Ø460x60 mm

thick

Sr no. ActivityStart

s End Total time1 Loading 10:20 10:35 00:152 Shot Blasting 14:10 15:55 01:453 Unloading 15:55 16:43 00:08

Total time 02:08

Tools Used:

1) EOT crane2) Shot blasting compartment3) Support roller tray4) Blower5) Grit

Sr no. Parameters observed1 Blower pressure 6.5 bar2 Shot/grit grit3 Grade G40

PAINTING DATE:28/6/2016Spool no. SPL-M4-104-006-SP-24 Project: MALWA

MATERIAL CSSize Ø460x60 mm

thickSr no. Activity Starts End Total time

1 Loading 19:05 19:15 00:06

2 Coating 1 (one side) 19:15 19:19 00:04

3 other side deposition cleaning 19:19 19:22 00:03

4 Coating 1 (other side) 19:22 19:27 00:05

5 Drying 19:27 14:00 18:33

6 Coating 2 (one side) 14:00 14:04 00:04

7 other side deposition cleaning 14:04 14:06 00:02

8 Coating 2 (other side) 14:06 14:11 00:05

9 Drying 14:11 09:00 18:49

10 Unloading 09:00 09:15 00:15

Total time 38:06:00

Sr no. Parameters observed

1 Airless machine pressure 3.5kg/cm^2

2 Paint type

Red Oxide Zinc Phosphate (ROZP) paint

3 Dry film thickness (55-60microns) 69

SUMMARY

Spool Fabrication Time Date: -Spool

no. SPL-M4-104-006-SP-24 Project: MALWAMateria

l CS Size Ø460x60 mm thick

Sr. No. Activity name Total time1 Length Measurement 00:122 Cutting 01:403 Datum Marking 00:404 Edge Preparation 00:555 Fit Up 03:40

6 Root Welding 03:209 Welding (SMAW) 15:5711 Magnetic particle testing 00:1512 Die penetrant test 00:2313 BSR Radiography test 01:0214 PWHT(Resistance Heating) 13:2015 ASR Radiography test 01:1516 Final dimensions check 00:4517 Shot blasting 02:0518 Painting 38:06

Total fabrication time 3 day,1 h,1 min.Total fabrication Days for completion 30 days*

Alloy steel

SPOOL DETAILS:

LTC, P.O.NUMBER:EPC/EM1/21000-48009/JKCC

SPOOL NO. - LTPC-M4-102-004-SP04

PROJECT: 2X660 MW SHREE SINGAJI TPP (STAGE-II)

CLIENT: MPPGCL

MATERIAL: SA 335 GR P91

OD: 728 mm X THK: 44 mm

LENGTH: 9514 mm

DETAILED TIME STUDY OF ACTIVITIES

LENGTH MEASUREMENT DATE: 3/6/2016Spool no. M4-102-004 SP04 Project: MALWAMaterial P91 Size Ø 728x44 mm thick

Sr. No. Activity name Starts End Total time

1 Locating & identifying the pipe 09:15 09:27 00:12

2 Length marking with whitener 09:27 09:32 00:05

Total time 00:17

Inspection Date: 3/6/2016Spool no. M4-102-004 SP04 Project: MALWAMaterial P91 Size Ø 728x44 mm thickSr. No. Parameter Actual Observed

1 Minimum Length 3420 OK2 Length of job 9514 9520

Tools Used:

5) Measuring Tape6) Right Angle7) Whitener8) drawing

LOADING Date: 3/6/2016Spool no. M4-102-004 SP04 Project: MALWAMaterial P91 Size Ø 728x44 mm thickSr. No. Activity name Starts End Total time

1 Belt Wrapping 12:00 12:02 00:022 Centre Setting 12:02 12:05 00:033 Job Lifting 12:05 12:15 00:104 Placing 12:15 12:17 00:025 Belt Unwrapping 12:17 12:20 00:03

Total time 00:20

UNLOADING Date: 3/6/2016Spool no. M4-102-004 SP04 Project: MALWAMaterial P91 Size Ø 728x44 mm thickSr. No. Activity name Starts End Total time

1 Belt Wrapping 12:40 12:42 00:022 Centre Setting 12:42 12:44 00:023 Job Lifting 12:44 12:56 00:124 Placing 12:56 12:58 00:025 Belt Unwrapping 12:58 13:00 00:02

Total time 00:20

Tools Used:

5) 10T EOT crane 6) 10T nylon belt7) Supports

8) Crane controller remote

SHOT BLASTING (PREBENDING) DATE: 3/6/2016Spool no. M4-102-004 SP04 Project: MALWA

MATERIAL P91

Size Ø 728x44 mm thick

Sr no. Activity Starts End Total time1 Loading 10:10 10:30 00:202 Shot Blasting 12:20 12:40 00:203 Unloading 12:40 13:00 00:20

Total time 01:00

Tools Used:

1) Shot blasting compartment2) Support tray3) Blower4) Grit5) EOT crane

Sr no. Parameters observed1 Blower pressure 6.5 bar2 Shot/grit grit3 grade G40

PRE BENDING SETUP Date: 3/6/2016Spool

no. M4-102-004 SP04 Project: MALWA

Material P91 Size Ø 728x44 mm thick

Sr. No. Activity name Starts End Total time1 Loading 12:00 12:20 00:202 Thickness measurement 15:20 15:27 00:073 Polypropylene inner coating 15:30 15:40 00:104 Parameters check 15:40 15:50 00:10

Total time 00:47

BENDING Date: 4/6/2016Spool

no. M4-102-004 SP04 Project: MALWA

Material P91 Size Ø 728x44 mm thick

Sr. No. Activity name Starts End Total time1 Material Check 09:20 09:21 00:012 Program 09:24 09:29 00:053 Loading 09:30 09:50 00:204 Pusher Clamped 09:50 10:00 00:105 Machine up 10:02 10:05 00:036 Bending Arm Setup 10:07 10:15 00:087 Machine down 10:17 10:20 00:037 Bend Roll Positioning 10:20 10:25 00:058 Side Roll Positioning 10:25 10:30 00:059 Temperature Setting 10:30 10:32 00:0210 Inductor Setting 10:32 10:35 00:0311 Preheating 10:40 10:55 00:1512 Bending * 06:3013 Inductor open 10:00 10:15 00:1514 Bending arm clamp open 10:15 10:17 00:0215 Machine up 10:20 10:25 00:0516 Inductor removed 10:25 10:27 00:02

17 Machine down Pusher clamp open 10:30 10:35 00:05

18 Unloading 10:40 11:00 00:20

Total time 08:39

*Note: The machine had issues of overcurrent due to which it stopped automatically for safety reasons. This happened twice in a matter of 20 minutes due to which preheating had to be done again. Bending was delayed and hence completed on Monday morning

Tools Used:

1) Cojafex hot induction bending machine2) EOT crane & belt

3) Reducer4) Adapter5) Insert6) Inductor ring7) Bending arm

Sr no. Parameters Actual observed1 Length 9514 95202 Straight start 1237 Ok4 Bend angle 90 Ok5 Bend radius 3580 3577

6 Intrados temperature 950 9327 Extrados temperature 1050 10418 Quenching type Air Ok9 Inductor start length 10 Ok

10 Inductor trans length 60 Ok11 Transformer ratio 10:2 Ok12 Heat Power 650KW Ok13 Pusher speed 17mm/min Ok14 Frequency 623Hz Ok15 Clamp size B732 Ok16 Inductor type L-50 Ok

PBHT Date: 11/6/2016Spool

no. M4-102-004 SP04 Project: MALWA

Material P91 Size Ø 728x44 mm thick

Sr. No. Activity name Starts End Total time

1 Loading 01:30 01:50 00:202 Polypropylene coating 04:50 05:10 00:203 Thermocouple mounting 05:20 05:25 00:054 Boogie in 08:40 08:45 00:055 Normalizing (1040 C) 08:45 21:36 13:516 Soaking 21:36 22:36 01:007 Air cooling(upto 90C) 22:36 10:36 12:008 Tempering (750 C) 10:37 20:20 09:439 Soaking 20:20 22:10 01:5010 Air cooling 22:10 10:10 12:00

Total time 50:14:00

Tools Used:

1) HT Furnace2) EOT crane3) Thermocouple4) Capacitor Discharge welding machine5) Glass wool6) Piers7) Ceramic Bricks8) Boogie9) Burners10) Combustion Blowers11) Exhaust blowers12) Graph recorder13) Moom plate

Sr no. Parameters Actual Observed1 No. of thermocouples 6 Ok2 Rate of heating 80C/hr OK3 Soaking temperature (Normalizing) 1040-1080C 10564 Soaking temperature (Tempering) 750-780C 770

SHOT BLASTING (POST BENDING) DATE: 12/6/2016Spool no. M4-102-004 SP04 Project: MALWA

MATERIAL P91

Size Ø 728x44 mm thick

Sr no. Activity Starts End Total time1 Loading 09:10 09:30 00:202 Shot Blasting 11:20 16:40 04:203 Unloading 17:00 17:20 00:20

Total time 05:00

MAGNETIC PARTICLE TESTING Date: 13/6/2016Spool no. M4-102-004 SP04 Project: MALWA

Material P91 Size Ø 728x44 mm thick

Sr. No. Activity name Start End Total time

s1 Loading 11:00 11:20 00:202 Testing 14:30 14:45 00:153 Defects check 14:45 14:50 00:10

Total time 00:42

Tools Used:

5) Magnetic particle liquid mixture (5000ml water with 50g 9CD and 50g 12AD)6) Yoke machine7) Chalk8) Spray bottle

BEND MARKING Date: 13/6/2016Spool no. M4-102-004 SP04 Project: MALWA

Material P91 Size Ø 728x44 mm thick

Sr. No. Activity name Starts End Total time1 Loading 14:00 14:20 00:202 levelling check 15:20 15:25 00:05

3 finding ovality, thickness and marking centres 15:25 15:35 00:10

4 Attaching Dori and marking centre line 15:35 15:45 00:10

5 Marking points P1,P2,P3,P4 15:45 15:55 00:106 Marking Datum point 15:55 16:00 00:057 Transferring points to side 16:15 16:30 00:158 Marking for cutting operation 16:30 16:50 00:209 Marking check 17:30 17:55 00:25

Total time 02:00:00

Tools Used:

10) Surface plate11) Spirit level12) Water level pipe13) Set squares14) Measuring tape15) Dori

16) Stand17) Chalk18) Outside calliper19) Dmeter20) Divider

Readings for Spool No. 9LTPC M4 101 008 SP03 OD 485mmThickness 75mm

Ovality

X 485 483 485 485 490Y 483 485 486 484 485

Thickness D-meter

1 84.3 83.5 85.2 77.8 752 76.4 77.1 76.1 78.7 75.13 66 67.2 66.9 71.9 73.9

Drawing readings

Parameter Actual ObservedLeg1 2440 2437Bal1 1030 1032Leg2 3168 3169Bal2 1708 1706Hypotenuse 3999 4001

CUTTING Date: 14/6/2016Spool no. M4-102-004 SP04 Project: MALWA

Material P91 Size Ø 728x44 mm thick

Sr. No. Activity name Starts End Total time1 Loading 09:00 09:20 00:202 Setting machine and parameters 09:20 09:30 00:103 Cutting 09:30 11:25 01:554 Loading and setting other end 14:00 14:15 00:155 Cutting 14:15 16:05 01:50

Total time 04:30

Tools Used:

4) Band Saw cutting machine5) Band saw cutting blade6) EOT crane7) Stand

Sr no. Parameters Actual Observed1 Blade type 1.4/2 TPI Ok2 Material Grade M51 OK3 First cut feed 2(4) mm/min 24 First cut speed 20 19.95 Further cuts feed 3(7) mm/min 46 Further cuts feed 25 22.97 Wheel pressure 3-4Mpa 48 Coolant Swisslube Ok

EDGE PREPARATION 15-06-2016Spool no. M4-102-004 SP04 Project: MALWA

Material P91 Size Ø 728x44 mm thick

Sr. No. Activity name Starts End Total time1 Loading & setting 08:45 09:40 00:552 Centering 09:40 09:50 00:103 Facing major 09:50 09:56 00:064 Facing check 09:56 09:58 00:025 Facing final 09:58 10:01 00:036 Edge preparation OD 10:05 10:15 00:107 Edge preparation ID 10:15 10:20 00:05

Total time 01:31

Tools Used:

2. SAFOP Edge preparation machine3. Centering tool4. Cutting tool5. Hydraulic clamps6. Electronic Jack7. EOT crane8. Support

Sr no. Parameters observed1 Hydraulic Clamp pressure 92kg/cm^22 Electronic jack pressure 450kg/cm^23 groove profile Compound V (20,10)4 Cutting tool used 3-4

IF TRUNNION IS ATTACHED TO THE ABOVE SPOOL FOLLOWING IS THE TIME CYCLE

FITUP 6-6-2016Spool no. 9LTPC M4 101 003 SP13 Project: MALWA

Material P91Size Ø 400x47 mm

thick

Sr. No. Activity name Starts End Total time

1 Fit-up trunion and base plate 1 08:00 08:40 00:401a) Marking centres on base plate 08:00 08:05 00:051b) Grinding of circular marking 08:05 08:10 00:051c) Grinding of trunion face 08:10 08:25 00:151d) Loading of trunion 08:25 08:30 00:051e) Aligning of trunion and baseplate 08:30 08:35 00:051f) Spot weld 08:35 08:40 00:05

2 Fit-up trunion and base plate 2 10:00 10:40 00:40

3 Fit-up trunion 1 14:00 15:20 01:203a) Support setup 14:00 14:05 00:053b) Loading of main pipe 14:05 14:20 00:153c) Levelling of main pipe 14:20 14:25 00:05

3d) Marking of trunion centre on mother spool 14:25 14:40 00:15

3e) Loading of trunion 1 14:40 14:45 00:053f) Centres match- trunion 14:45 14:55 00:103g) Spot weld of cleats 14:55 15:00 00:053h) Loading of trunion 2 15:00 15:05 00:053i) Centres align- trunion 15:05 15:15 00:103j) Spot weld of cleats 15:15 15:20 00:05

4 Cleat welding 01:55

 4a) Preheating (80-90C) 1 15:50 16:25 00:354b) Cleat welding 16:25 16:45 00:204c) Preheating (80-90C) 2 17:00 17:40 00:404d) Cleat welding 17:40 18:00 00:20

5 Fit-up check 9:00 9:30 00:30Total time 05:05

Tools Used:

13) Measuring Tape14) Thread15) Stand16) Steel Scale17) Spirit level18) Chalk19) IPad- to check drawing and calculate slope20) Drawing21) Cleat22) Overhead Crane23) GTAW welding tools24) Burner25) Grinding machine

S.no Parameters Remark Tool used

1 Spool No. Validated Visually2 Material CS validated PMI

3 Internal diameter and thickness Validated Measuring tape

4 Orientation from drawing Validated Template

5 Distances mentioned in drawing Validated Line dori setup

7 Root gap Validated 4mm 4mm dia tongs8 No. of cleats 8 visually

WELDING (SMAW) DATE: 08/06/2016Spool no. 9LTPC M4 101 003 SP13 Project: MALWA

MATERIAL P91

Size Ø 400x47 mm thick

Sr no. Activity Starts End Total time1 Loading 08:00 08:15 00:15

Purging setup 08:15 08:30 00:152 Miller machine setup 08:30 09:00 00:30

3 Pre Heat(225C) 08:45 10:30 01:454 Welding ( GTAW ) 11:35 12:10 00:355 Welding ( SMAW ) 1 14:00 14:20 00:20

Grinding 14:25 14:30 00:056 Welding ( SMAW ) 2 14:40 15:10 00:30

Grinding 15:20 15:23 00:037 Welding ( SMAW ) 3 15:35 16:05 00:30

Grinding 16:10 16:14 00:048 Welding ( SMAW ) 4 17:00 17:30 00:30

Grinding 17:35 17:39 00:049 Welding ( SMAW ) 5 10:00 10:30 00:30

Grinding 10:45 10:49 00:0410 Welding ( SMAW ) 6 11:45 12:15 00:30

Grinding 12:20 12:25 00:0511 Welding ( SMAW ) 7 14:10 14:40 00:30

Grinding 15:00 15:05 00:05

12Welding ( SMAW ) 8 (final

layer) 16:00 17:00 01:0013 Grinding and brush up 10:30 10:45 00:1514 Welding for 2nd trunion 07:3615 welding base plate-1 00:1516 welding base plate-2 00:15

Total time 15:57:00

Tools Used:

12) Millers induction preheating machine13) Electrode wire14) DC supply15) Welding tools16) Grinding machine17) Chisel18) Welding helmet19) Glass wool20) Thermocouples21) Argon gas22) Circular metal discs

GTAW parameters

Sr no. Parameters Actual Observed1 Pre-heat Temperature 225 241

2 Inter-pass Temperature 325 Thermochalk ok3 Filler rod type ER 90SB9 Ok4 Filler rod dia 2.4mm Ok5 Current 70-150A 170A6 Voltage 8-15V 10.2V7 Current and polarity DCEN Ok8 Speed/Bead length 70 70

SMAW 3.15mm dia electrode parameters

Sr no. Parameters Actual Observed1 Pre-heat Temperature 225 2182 Inter-pass Temperature 325 Thermochalk ok3 Filler rod type E901-B9 Ok4 Filler rod dia 3.15mm Ok5 Current 90-130A 187A6 Voltage 18-28V 22.8V7 Current and polarity DCEP Ok8 Speed/Bead length 100 100

SMAW 4mm dia electrode parameters

Sr no. Parameters Actual Observed1 Pre-heat Temperature 225 2112 Inter-pass Temperature 325 Thermochalk ok3 Filler rod type E901-B9 Ok4 Filler rod dia 4mm Ok5 Current 120-180A 215A6 Voltage 18-28V 23.5V7 Current and polarity DCEP Ok8 Speed/Bead length 100 100

BSR WELD VISUAL PREPARATION DATE:11/6/2016Spool no. 9LTPC M4 101 003 SP13 Project: MALWA

MATERIAL P91Size Ø 400x47 mm

thick

Sr no. ActivityStart

s End Total time

1 Loading to buffing location 14:3014:4

5 00:15

2 Buffing 14:4515:1

2 00:27

3 Weld visual 15:1215:3

5 00:23

Total time 01:05

BSR DIE PENETRANT TEST Date: 12/6/2015Spool no. 9LTPC M4 101 003 SP13 Project: MALWAMaterial P91 Size Ø 400x47 mm thick

Sr. No. Activity nameStart

s End Total time in Minutes1 Cleaning of Spool 10:10 10:20 00:102 Applying DIE 10:20 10:27 00:073 Waiting for DIE to absorb 10:27 10:40 00:134 Cleaning of DIE 10:40 10:49 00:095 Applying Developer 10:49 10:55 00:066 Examination for defects 10:55 11:10 00:15

Total time 01:00

Tools/Materials Used:

1) Die/Penetrant2) Developer3) Cleaning Agent4) Dry cotton

PWHT (FURNACE) Date: 15/6/2016Spool no. 9LTPC M4 101 003 SP13 Project: MALWA

Material P91 Size Ø 400x47 mm thick

Sr. No. Activity name Starts End Total time1 Loading 22:10 23:00 00:502 Thermocouple mounting 23:00 23:05 00:053 Polypropylene coating 23:10 23:30 00:20

3 Boogie in 01:55 02:00 00:054 Stress relieving 02:00 09:20 07:205 Soaking 09:20 12:00 02:406 cooling in furnace upto 300C 12:00 19:30 07:309 air cooling 19:30 02:30 07:00

Total time 25:50:00

Tools Used:

1) HT Furnace2) EOT crane3) Thermocouple4) Capacitor Discharge welding machine5) Glass wool6) Piers7) Ceramic Bricks8) Boogie9) Burners10) Combustion Blowers11) Exhaust blowers12) Graph recorder13) Moom plate

Sr no. Parameters Actual Observed1 No. of thermocouples 6 Ok2 Rate of heating 80C/hr OK3 Soaking temperature 745-765C 760

ASR WELD VISUAL PREPARATION DATE:16/6/2016Spool no. 9LTPC M4 101 003 SP13 Project: MALWA

MATERIAL P91Size Ø 400x47 mm

thick

Sr no. ActivityStart

s End Total time

1 Loading 10:1010:2

5 00:15

2 Weld visual 11:0011:1

0 00:10

3 Check for visual defects 11:1011:1

3 00:03

4 Grinding portions near weld area 11:15 11:2 00:05

0

5 Hardness test 11:2011:2

5 00:05

Total time 00:38

Tools Used:

1) Hardness tester2) Grinding machine3) Support stand

ASR DIE PENETRATION TEST Date: 16/6/2015Spool no. 9LTPC M4 101 003 SP13 Project: MALWAMaterial P91 Size Ø 400x47 mm thick

Sr. No. Activity nameStart

s End Total time in Minutes1 Cleaning of Spool 12:00 12:10 00:102 Applying DIE 12:10 12:17 00:073 Waiting for DIE to absorb 12:17 12:30 00:134 Cleaning of DIE 12:30 12:40 00:105 Applying Developer 12:40 12:45 00:056 Examination for defects 12:45 01:00 00:15

Total time 01:00

Tools/Materials Used:

1) Die/Penetrant2) Developer3) Cleaning Agent4) Dry cotton

FINAL DIMENSIONS CHECK Date: 17/6/2016Spool no. 9LTPC M4 101 003 SP13 Project: MALWA

Material P91 Size Ø 400x47 mm thick

Sr. No. Activity name Starts End Total time

1 Labelling/Tag Preparation 14:30 14:40 00:10

2 Levelling of Spool 14:10 14:15 00:053 Measurement of Spool 14:15 14:30 00:15

4 Quality/TPI 14:40 14:55 00:15

Total time 00:45

SHOT BLASTING DATE:19/6/2016Spool no. 9LTPC M4 101 003 SP13 Project: MALWA

MATERIAL P91 Size Ø 400x47 mm thick

Sr no. ActivityStart

s End Total time

1 Loading 12:0512:1

9 00:14

2 Shot Blasting 14:1417:0

5 02:51

Total time 03:05

Tools Used:

1) EOT crane2) Shot blasting compartment3) Support roller tray4) Blower5) Grit

Sr no. Parameters observed1 Blower pressure 6.5 bar2 Shot/grit grit3 grade G40

PAINTING DATE:19/6/2016Spool no. 9LTPC M4 101 003 SP13 Project: MALWA

MATERIAL P91 Size Ø 400x47 mm

thickSr no. Activity Starts End Total time

1 Loading 17:05 17:15 00:102 Coating 1 (one side) 17:15 17:25 00:103 other side deposition cleaning 17:25 17:28 00:034 Coating 1 (other side) 17:28 17:40 00:125 Drying 17:40 12:20 18:30

6 Coating 2 (one side) 12:20 12:31 00:117 other side deposition cleaning 12:31 12:33 00:02

8 Coating 2 (other side) 12:33 12:45 00:129 Drying 12:45 07:25 18:4010 Unloading 07:25 07:40 00:15

Total time 38:25:00

Tools Used:

1) Red Oxide Zinc Phosphate (ROZP) paint2) Airless Machine. Pressure 3.5kg/cm^23) Stencilling Machine4) Support stand5) Masking tape6) Zinc coating7)

Sr no. Parameters observed1 Airless machine pressure 3.5kg/cm^2

2 Paint type

Red Oxide Zinc Phosphate (ROZP) paint

3 Dry film thickness (40microns) 44.9

SUMMARY

Spool Fabrication Time Date: -Spool

no. M4-102-004 SP04 Project: MALWA

Material P91 Size Ø 728x44 mm thick

Sr. No. Activity name Total time1 Length Measurement 00:172 Shot blasting 01:003 Pre bending setup 00:474 Bending 08:395 PBHT 50:146 Shot blasting 05:007 Magnetic particle Testing 00:428 Datum marking 01:409 Cutting 04:30

10 Edge preparation 01:3111 Fit-up 05:0512 Welding 15:5713 Weld visual 01:0514 BSR Die Penetrant test 01:0015 PWHT 25:5016 Weld visual 00:3817 ASR Die Penetrant test 1:0018 Final dimensions check 00:4519 Shot blasting 03:0520 Painting 38:25

Total fabrication time 6 day, 23 hr. 10 minTotal fabrication Days for completion 27 days

Differences between CS and P91 spool time cycle

P91 spool includes a bend. Following are the extra processes done

- Shot blasting is required before bending to remove layer of painting and contaminants- Bending operation is done on spool which is a time taking process - PBHT process is done ( normalising & tempering ) which is a 50 hour cycle - After PBHT again short blasting process is done which due to higher surface hardness

takes lot of time- MT ( magnetic particle test ) is done- Bend datum marking is done which includes thickness and ovality measurement

Following are the differences in various process followed in manufacturing of both the spools

P91

1. Thickness of spool is 44 mm.2. In cutting operation speed & Feed is lower due to harder material (following PBHT)

so it takes more time

3. Thickness and hardness is high so it takes more time for edge preparation ( compound V )

4. Fit up takes more time preheating is also required for cleat welding.5. Preheating is required Before welding preheating temperature is 225 °C (To achieve

preheat temperature take more time)6. Preheating is done using induction heating which takes more setup time. 7. PWHT takes more time due to higher hardness of p91. 8. Weld visual is done after welding and PWHT as it is alloy steel

CS

1. Thickness of spool is 60 mm.2. In cutting operation takes less time because in CS speed & feed is higher due to

relatively lesser hardness ( no HT before cutting) 3. Fit-up takes relatively lesser time due to lesser parts and no need of preheating for

cleat welding4. Preheating temperature is 80 C for thickness >19mm ( preheating takes lesser time)5. Preheating is done using gas burner so less setup time6. Welding between pipe and elbow with use of SAW process which is a faster process7. BSR RT, PT, MT and ASR RT is done so NDE takes more time8. PWHT takes lesser time due to lower thickness and hardness of CS9. No weld visual required due to it not being an alloy steel

Spot Check ReportSpot check of welding being done by contractors is noted by Production, Quality and welding department every day in LTPC. Spot check includes each and every detail about welding, welder, electrodes, welding positions etc. All the details about the spot check is mentioned below.

1) Job no. /spool no. __________ 2) Welding process __________

Specified in WPS Actually observedConsumable type/sizeConsumable batch no.Pre-heat temp. (°c)Inter-pass temp. (°c)VoltageCurrentMin. bead Length(SMAW)Min. travel speed

3) Shielding gas flow (LPM) _____________4) Welding Position _____________5) Post heating temperature(°c) _____________6) Electrode stub length _____________7) Any arc strike OK? _____________8) Welding cable OK? _____________9) Heating arrangement available? _____________10) Temp. stick available? _____________11) Purging Ok? _____________12) Portable oven Hot? _____________13) Stub bin Available? _____________14) Is joint clean/ edge burnt _____________15) Restart Ground _____________16) Welder stamp punched? ______________

17) Machine calibration due date ______________18) Slag removal hammer available ______________

After checking all the parameters the person needs to write whether there is corrective action to be taken or not. Every person from production, welding and quality should do one spot check every day. Spot check make the welders do his job according to the WPS. If they are making any kind of mistakes related to safety and welding procedure, we can correct them.

Welding Department functionWelding & Metallurgy department is providing services to LTPC in the areas like welding, heat treatments and developmental activities related to welding engineering and metallurgy. Welding department is responsible for monitoring various welding processes going on inside the shop, setting up of WPS (welding procedure specification) for a particular project, proper examination & verification of qualified welders, heat treatments, bending processes & enlightenment of any new development made in the field of Welding engineering.

Organization structure

Welding processes performed at LTPC1) GTAW (Gas tungsten arc welding)2) SMAW (Shielded metal arc welding)3) SAW (Sub-merged arc welding)4) FCAW (Flux cored arc welding)

Heat treatment processes at LTPC1) PBHT (Post bending heat treatment)- involves either normalizing or tempering as and

when required.2) PWHT (Post welding heat treatment)

Head, Manufacturing

Manager, Welding

Welding EngineerWelding Engineer

Welding Engineer

3) Pre-heating process4) Post-heating process

Bending processInduction bending using Cojafex Hot Induction bending machine

Welding and its typesWelding is a process to join two similar or dissimilar metals- with or without the use of filler wire, with or without the application of heat & pressure.

It is a fabrication process that joins materials, usually metals or thermoplastics, by causing fusion, which is distinct from lower temperature metal-joining techniques such as brazing and soldering, which do not melt the base metal. In addition to melting the base metal, a filler material is often added to the joint to form a pool of molten material (the weld pool) that cools to form a joint that can be as strong, or even stronger, than the base material. Pressure may also be used in conjunction with heat, or by itself, to produce a weld.

Some of the best known welding methods include:

Shielded metal arc welding (SMAW) – also known as "stick welding or electric welding", uses an electrode that has flux around it to protect the weld puddle. The electrode holder holds the electrode as it slowly melts away. Slag protects the weld puddle from atmospheric contamination.

Gas tungsten arc welding (GTAW) – also known as TIG (tungsten, inert gas), uses a non-consumable tungsten electrode to produce the weld. The weld area is protected from atmospheric contamination by an inert shielding gas such as argon or helium.

Gas metal arc welding (GMAW) – commonly termed MIG (metal, inert gas), uses a wire feeding gun that feeds wire at an adjustable speed and flows an argon-based shielding gas or a mix of argon and carbon dioxide (CO2) over the weld puddle to protect it from atmospheric contamination.

Flux-cored arc welding (FCAW) – almost identical to MIG welding except it uses a special tubular wire filled with flux; it can be used with or without shielding gas, depending on the filler.

Submerged arc welding (SAW) – uses an automatically fed consumable electrode and a blanket of granular fusible flux. The molten weld and the arc zone are protected from atmospheric contamination by being "submerged" under the flux blanket.

SAW (Sub-merged arc welding)

Submerged arc welding (SAW) is a common arc welding process. The first patent on the submerged-arc welding (SAW) process was taken out in 1935 and covered an electric arc beneath a bed of granulated flux. Originally developed and patented by Jones, Kennedy and Rothermund, the process requires a continuously fed consumable solid or tubular (metal cored) electrode. The molten weld and the arc zone are protected from atmospheric contamination by being "submerged" under a blanket of granular fusible flux consisting of lime, silica, manganese oxide, calcium fluoride, and other compounds. When molten, the flux becomes conductive, and provides a current path between the electrode and the work. This thick layer of flux completely covers the molten metal thus preventing spatter and sparks as well as suppressing the intense ultraviolet radiation and fumes that are a part of the shielded metal arc welding (SMAW) process.

SAW is normally operated in the automatic or mechanized mode, however, semi-automatic (hand-held) SAW guns with pressurized or gravity flux feed delivery are available. The process is normally limited to the flat or horizontal-fillet welding positions (although horizontal groove position welds have been done with a special arrangement to support the flux). Deposition rates approaching 45 kg/h (100 lb/h) have been reported — this compares to ~5 kg/h (10 lb/h) (max) for shielded metal arc welding. Although currents ranging from 300 to 2000 A are commonly utilized, currents of up to 5000 A have also been used (multiple arcs).

SMAW (Shielded metal arc welding)

Shielded metal arc welding (SMAW), also known as manual metal arc welding (MMA or MMAW), flux shielded arc welding or informally as stick welding, is a

manual arc welding process that uses a consumable electrode covered with a flux to lay the weld.

An electric current, in the form of either alternating current or direct current from a welding power supply, is used to form an electric arc between the electrode and the metals to be joined. The workpiece and the electrode melts forming the weld pool that cools to form a joint. As the weld is laid, the flux coating of the electrode disintegrates, giving off vapours that serve as a shielding gas and providing a layer of slag, both of which protect the weld area from atmospheric contamination.

GTAW (Gas tungsten arc welding)

Gas tungsten arc welding (GTAW), also known as tungsten inert gas (TIG) welding, is an arc welding process that uses a non-consumable tungsten electrode to produce the weld. The weld area is protected from atmospheric contamination by an inert shielding gas (argon or helium), and a filler metal is normally used, though some welds, known as autogenous welds, do not require it. A constant-current welding power supply produces electrical energy, which is conducted across the arc through a column of highly ionized gas and metal vapours known as a plasma.

GTAW is most commonly used to weld thin sections of stainless steel and non-ferrous metals such as aluminium, magnesium, and copper alloys. The process grants the operator greater control over the weld than competing processes such as shielded metal arc welding and gas metal arc welding, allowing for stronger, higher quality welds. However, GTAW is comparatively more complex and difficult to master, and furthermore, it is significantly slower than most other welding techniques. A related process, plasma arc welding, uses a slightly different welding torch to create a more focused welding arc and as a result is often automated.

FCAW (Flux cored arc welding)

Flux-cored arc welding (FCAW or FCA) is a semi-automatic or automatic arc welding process. FCAW requires a continuously-fed consumable tubular electrode containing a flux and a constant-voltage or, less commonly, a constant-current welding power supply. An externally supplied shielding gas is sometimes used, but often the flux itself is relied upon to generate the necessary protection from the atmosphere, producing both gaseous protection and liquid slag protecting the weld. The process is widely used in construction because of its high welding speed and portability.

GTAW is a constant current process whereas SAW is a constant voltage process.

WPS (Welding procedure specification)

Welding department sets a standard procedure for the welding of joints depending upon the project order received. The welders are required to strictly adhere to the WPS and do welding accordingly. Spot checks are carried out at regular intervals by shop engineers in order to make sure that the welding is being done right as per the procedure & parameters specified in WPS. WPS accounts for:-

1) Project:- Ex- RRVUNL, MPPGCL, NTPC-NABINAGAR etc.2) Type of welding process to be used:- GTAW/ SMAW/ SAW 3) Electrode grade & size4) Current & Voltage range for the specified welding process5) Type of flux used and its grade6) Technique regarding how to do welding:- Weave beads/ Stringer beads etc.7) Type of Material:- P91/ P92/ P11/ P22 (Alloy steels); SA106 P1 (Carbon steel)8) Inter-pass & pre-heat temperatures9) Post-heat temperature10) Soaking temperature in PWHT11) ROH (Rate of heating) & ROC (Rate of cooling) in post-heating12) Precautionary measures to be taken while welding

Pre-heating & Post-heating process

Pre-heating

The pre-heating of pipe spools is done before the welding processes at areas which lie in the vicinity of the groove to be welded. The main purpose of pre-heating is to prevent the formation of cracks in the welded area & heat affected zone (HAZ).

Higher the temperature difference, faster is the cooling rate and hence more chances of stress development & crack formation. The pre-heating in the nearby area of the portion to be welded reduces the temperature difference between welded area & the area surrounding it. Pre-heating also evaporates the moisture which may be present on the surface of pipe spool, thus preventing the diffusion of Hydrogen (H2) gas which eventually causes crack formation.

Pre-heating slows down the cooling rate because of which coarse grains are formed in the microstructure of the welded material. Coarse grains result in:-

Reduced hardness of the material Improves material ductility Improves material toughness

Pre-heating is not required in case of SS spools as there is not much risk to the microstructure (Austenitic) of the base material even after Hydrogen diffuses into it.

Pre-heating temperature is always measured at the heat affected zone (HAZ) i.e. area near to the welded zone.

At LTPC, pre-heating of spools is done in three ways namely:-

By using torch burners which uses LPG as fuel:- The groove is heated sometimes from outside & sometimes from inside by placing the burners which look like a cylindrical gun. The burners make use of LPG in heating the surface.

Resistance heating:- This makes use of AC and nichrome wire (60-70 % Ni + 40-30 % Cr) which is coated with Ceramic beads from outside. At first, glass wool is kept over the surface to be pre-heated over which, several coils of nichrome wire are applied. Another layer of glass wool is applied over the coils of wire so as to prevent any kind of heat loss with glass wool playing the role of refractory. Because of the resistance offered by the wire to the flow of current through it, the wire gets heated up eventually heating the entire required surface. Ceramic beads are used in order to prevent nichrome wire from sticking to the surface.

Melting point of Nichrome:- 1500-1600 deg. Celsius

Melting point Ceramic:- 2300-2500 deg. Celsius

Induction heating using Miller machine shown above:- This also makes use of AC but is slightly different and faster than resistance heating. In this process, a cable is taken from the miller machine which contains both Cu (copper) wire and water flowing tube. Thermo-couples are placed at appropriate positions where the temperature needs to be determined. Cu wire gets heated up because of the flow of varying current, thus facilitating the heating process. The water circulation inside the cable is used to cool down Cu wire thus preventing it from getting over-heated. In this also, Cables are placed over glass wool. Melting point of Cu:- 1000 deg. Celsius

Post-heating

The main objective of post-heating is same as that of pre-heating, to prevent the formation of cracks in welded area & heat affected zone (HAZ). Post-heating should commence immediately after the completion of welding. Same methods are used for post-heating also which are incorporated for pre-heating. The post-heating temperature for various materials are:-

1) P91/P92:- 350-400 deg. Celsius for minimum 2 hrs, Rate of heating (ROH) & Rate of cooling (ROC)- 100 deg.Celsius/hr

2) P22/P11:- 300-350 deg. Celsius for minimum 2 hrs, ROH & ROC- 100 deg. Celsius/hr

The above temperatures are as per RRVUNL (Rajasthan rajya viduyt utpadan nigam limited) project.

Heat treatment furnace

PBHT (Post bending heat treatment) & PWHT (Post welding heat treatment) are performed inside the furnace.

The furnace is divided into 8 zones as shown in the figure. Zone 1&8 have got 3 burners whereas rest of the remaining zones have got 4 burners each.

There is 1 spark plug for every for every 2 burners & there are a total of 16 spark plugs in all.

Number of normal air inlets:- 30 No. of burners:- 30 Fuel used:- Mixture of Natural gas (Methane) & air Cooling blowers:- 2 inlets No. of air exhaust outlets:- 2 Type:- Bogie Hearth heat treatment furnace Manufacture:- SECO WARWICK ALLIED Pvt. Ltd. Load capacity:- 70 tonne for charge (pipe spools) + 15 tonne for piers Chamber dimensions:- 12 m (length) by 6 m (width) by 3.6 m (height) Design temperature:- 1150 deg. Celsius

Piers are made of P22 material and serve as a stand for keeping the pipe spools. On the periphery of the furnace, bricks made up of refractory are kept to provide support to the piers.

PWHT temperature for various materials at LTPC:-

1) P91/P92:- 760 deg. Celsius2) P11/P22:- 730 deg. Celsius3) SA106 (Grade A/B/C):- 630 deg. Celsius

PBHT time & temperatures for normalizing & tempering of various materials:-

Zone 1

Zone 82 3 4 5 6 7

Air outlet

S.No. Material Normalizing Tempering

1) Carbon steel/mild steel

Soaking temp:- 900-960 deg. Celsius,

Soaking time:- 1.25 min/mm

Not applicable

2) P11 (1.25% Cr, 0.5% Mo)

Soaking temp:- 920-960 deg. Celsius,

Soaking time:- 1.25 min/mm

Soaking temp:- 680-730 deg. Celsius,

Soaking time:- 2.5 min/mm

3) P22 (2.25 % Cr, 1% Mo)

Soaking temp:- 920-960 deg. Celsius,

Soaking time:- 1.25 min/mm

Soaking temp:- 690-760 deg. Celsius,

Soaking time:- 2.5 min/mm

4) P91 (9% Cr, 1% Mo)

Soaking temp:- 1040-1080 deg. Celsius, Soaking

time:- 1.25 min/mm

Soaking temp:- 750-780 deg. Celsius,

Soaking time:- 2.5 min/mm

5) WB36 Soaking temp:- 900-980 deg. Celsius,

Soaking time:- 1.25 min/mm

Soaking temp:- 580-680 deg. Celsius,

Soaking time:- 2.5 min/mm

Need for heat treatment & types used at LTPC

Heat treatment is a method used alter the physical & sometimes chemical properties of a material. Any type of heat treatment involves 3 stages- Heating, Soaking & Cooling.

In heating stage, the material is heated up to a certain temperature. In soaking stage, the material is kept at that temperature for a certain time period. In cooling stage, the material is cooled down to room temperature or any other desired temperature with the help of relevant cooling medium.

Cooling medium & rate of cooling decides the phase microstructure. If cooling rate is high then, fine grains will be formed. If cooling rate is slow then coarse grains will be formed.

Objectives of heat treatment are:-

1) To relieve the internal stresses set up during hot/cold working.2) To refine the grains & grain structure.

3) To improve machinability.4) To improve ductility or toughness.5) To improve red or hot hardness.6) To improve formability.

Heat treatments used at LTPC

1) Normalizing:- In this, cooling medium is air. It is carried out by heating approx. to about 70-90 deg. Celsius above the upper critical temperature i.e. A3 or Acm (912 deg. Celsius & 1050 deg. Celsius respectively) line in Fe-C phase diagram, followed by cooling. It is applied mainly to unalloyed & low-alloyed hypo-eutectoid steels.

2) Tempering:- The martensite of quenched tool steel is exceedingly brittle & highly stressed. Consequently, cracking & distortion of the object are liable to occur after quenching. The ductility & toughness of Martensite may be enhanced & these internal stresses are relieved by heat treatment called tempering.

Martensite at low temp. tempering (150-400 deg. Celsius):- TroositeMartensite at high temp. tempering (730-760 deg. Celsius):- Sorbite

Welding cycle for P91 & Procedure to be followed

P91 material is an alloy steel under SA335 and consists of 9% Cr, 1% Mo. It has got a tensile strength of 585 MPa. The weld heat treatment cycle is as follows:-

Pre-heating (till 225 deg. Celsius)Welding in range of 225-325 deg Post-heating (350-400 deg for 2 hrs)Cooling at 100 deg/hrHeating to 760 deg (PWHT)Soaking at 745-770 deg (PWHT)Cooling (PWHT).

Procedure & Important measures (as per RRVUNL CHHABRA PROJECT- WPS)

1) Pre-heating requirements shall be followed for tack welding, natural gas burners may be used for tacking purposes & socket welds on materials 3” & under.

2) Only GTAW used for tacking, root pass & hot pass. Inert gas backing shall be maintained till hot pass is welded.

3) Weld groove should be thoroughly cleaned prior to welding atleast 25 mm from the edge of weld joint on each side.

4) Pre-heating shall be maintained at a distance of 75 mm or 1.5 times (whichever is less) the max. base metal thickness welded in all directions from the centre of the joint.

5) In case of drop in required minimum pre-heat temperature after 9.5 mm thickness or 25% the weld groove (whichever is less) is filled, the weld shall be post heated for 1 hr before it cools down to ambient temp. examined by PT (Penetrant testing) or MPT (Magnetic particle testing) & again pre-heated to 225 deg before resuming welding.

6) Post heating should commence immediately after welding. 7) For SMAW, weaving shouldn’t be more than 3 times the diameter of electrode used.

It means that the weave length should always be less than 3 times the dia. of electrode used. It’s a good practice to curb wastage of material.

Microstructure Variation

A microstructure is the microscopic view of a material which involves the beautiful arrangement of grains & grain boundaries. With the various heat treatment & bending processes which are performed at LTPC, the microstructure of the base metal is also liable to change depending upon the process. The various regions of a microstructure are termed as a Phase, phases may differ from each other both in terms of composition as well as crystal structure. The variation in the microstructure of various materials used at LTPC as per the process is shown below:-

Carbon steel (SA106 Grade A/B/C)

Base material:- α-ferrite + banded pearlite

Here is a microstructure of High carbon steel (0.6-1% carbon content). The white portion which can be seen is α-ferrite whereas the lamellar portion shown is pearlite (α-ferrite + Fe3C). Fe3C is known is Iron carbide or cementite. The black portion is more because of high C content.

HAZ (Heat affected zone):- Equi-axed grains of ferrite & pearlite, grain size as per ASTM (American society of testing & materials) no. 10

Weld metal:- Acicular ferrite (basket weave structure)

P91/P92 (Alloy steel SA335)

Base material:- Untempered martensite

Martensite is formed when samples are austenitized and are quenched at a very fast rate. The structure so formed is very hard and complete with stresses know as martensite. The white portion in the structure is ferrite and the sharp needles are pearlite, needle like structure due to fast cooling rate.

HAZ & Welded area:- Tempered martensite

Untempered martensite is heated to a temp. around 760 deg (slightly above lower critical temp. line) so as to remove the developed hardness & stresses due to fast quenching. The final structure after PWHT is tempered martensite.

P11/P22 (Alloy steel SA335)

Base material:- ferrite + Untempered bainite + martensite (very low percentage), grain size as per 8.5

This microstructure is a matrix of ferrite & bainite. Bainite is formed when austenitized sample undergo moderate cooling. Bainite gets formed in the range of 270-540 deg (as per TTT & CCT) when cooled down from temperatures slightly above 912 deg. Celsius. In case of bainite, the pearlite needles so formed are blunt & not sharp.

Austempering of materials may be done in order to achieve 100% bainite structure.

HAZ & Welded area:- ferrite + tempered bainite

Inter-pass & pre-heat temperatures for different materials

Pre-heat temperature is the temperature up to which the materials are pre-heated before the commencement of welding.

Inter-pass temperature as the name suggests is the temperature between 2 passes of the weld. It is the temperature above which welding process is not done as excessive heat may melt the already solidified molten metal thus disturbing the entire joint. Welding of the material is done between pre-heat & inter-pass temperature.

Material Pre-heat temp. (deg. Celsius)

Inter-pass temp. (deg. Celsius)

P91/P92 225 325

P11/P22 175-200 275

P1 (Carbon steel) Upto 19 mm thickness:- 20-25, above 19 mm thickness:-

80-100

300

Defects in WeldingA welding defect is any flaw that compromises the usefulness of a weld metal. There is a great variety of welding defects. Welding imperfections are classified according to ISO 6520 while their acceptable limits are specified in ISO 5817 and ISO 10042.

Major causes

According to the American Society of Mechanical Engineers (ASME), welding defect causes are broken down as follows: 45 percent poor process conditions, 32 percent operator error, 12 percent wrong technique, 10 percent incorrect consumables, and 5 percent bad weld grooves.

Cracks

Arc strike cracking

Arc strike cracking occurs when the arc is struck but the spot is not welded. This occurs because the spot is heated above the material's upper critical temperature and then essentially quenched. This forms martensite, which is brittle and may lead to higher chances of micro-cracks. Usually the arc is struck in the weld groove so this type of crack does not occur, but if the arc is struck outside of the weld groove then it must be welded over to prevent the cracking. If this is not an option then the arc spot can be post-heated, that is, the area is heated with an oxy-acetylene torch, and then allowed to cool slowly.

Cold cracking

Residual stresses can reduce the strength of the base material, and can lead to catastrophic failure through cold cracking, as was the case with several of the World War II Liberty ships' hulls. Cold cracking is limited to steels and is associated with the formation of martensite as the weld cools. The cracking occurs in the heat-affected zone of the base material. To reduce the amount of distortion and residual stresses, the amount of heat input should be limited, and the welding sequence used should not be from one end directly to the other, but rather in segments.

Cold cracking only occurs when all the following preconditions are met:

Susceptible microstructure (e.g. martensite) Hydrogen present in the microstructure (hydrogen embrittlement) Service temperature environment (normal atmospheric pressure): -100 to +100 °F High restraint

Eliminating any one of these will eliminate this condition.

Crater crack

Crater cracks occur when a crater is not filled before the arc is broken. This causes the outer edges of the crater to cool more quickly than the crater, which creates sufficient stresses to form a crack. Longitudinal, transverse and/or multiple radial cracks may form.

Hat crack

Hat cracks get their name from the shape of the cross-section of the weld, because the weld flares out at the face of the weld. The crack starts at the fusion line and extends up through the weld. They are usually caused by too much voltage or not enough speed.

Hot cracking

Hot cracking, also known as solidification cracking, can occur with all metals, and happens in the fusion zone of a weld. To diminish the probability of this type of cracking, excess material restraint should be avoided, and a proper filler material should be utilized. Other causes include too high welding current, poor joint design that does not diffuse heat, impurities (such as sulfur and phosphorus), preheating, speed is too fast, and long arcs.

Underbead crack

An undercut crack, also known as a heat-affected zone (HAZ) crack, is a crack that forms a short distance away from the fusion line; it occurs in low alloy and high alloy steel. The exact causes of this type of crack are not completely understood, but it is known that dissolved hydrogen must be present. The other factor that affects this type of crack is internal stresses resulting from: unequal contraction between the base metal and the weld metal, restraint of the base metal, stresses from the formation of martensite, and stresses from the precipitation of hydrogen out of the metal.

Longitudinal crack

Longitudinal cracks run along the length of a weld bead. There are three types: check cracks, root cracks, and full centerline cracks. Check cracks are visible from the surface and extend partially into weld. They are usually caused by high shrinkage stresses, especially on final passes, or by a hot cracking mechanism. Root cracks start at the root and extent part way into the weld. They are the most common type of longitudinal crack because of the small size of the first weld bead. If this type of crack is not addressed then it will usually propagate into subsequent weld passes, which is how full cracks (a crack from the root to the surface) usually form.

Root and toe cracks

A root crack is the crack formed by the short bead at the root (of edge preparation) beginning of the welding, low current at the beginning and due to improper filler material used for welding. Major reason for happening of these types of cracks is hydrogen embrittlement. These types of defects can be eliminated using high current at the starting and proper filler material. Toe crack occurs due to moisture content present in the welded area. It acts as a part of the surface crack so can be easily detected. Preheating and proper joint formation is must for eliminating these types of defects.

Transverse crack

Transverse cracks are perpendicular to the direction of the weld. These are generally the result of longitudinal shrinkage stresses acting on weld metal of low ductility. Crater cracks occur in the crater when the welding arc is terminated prematurely. Crater cracks are normally shallow, hot cracks usually forming single or star cracks. These cracks usually start at a crater pipe and extend longitudinal in the crater. However, they may propagate into longitudinal weld cracks in the rest of the weld.

Distortion

Welding methods that involve the melting of metal at the site of the joint necessarily are prone to shrinkage as the heated metal cools. Shrinkage then introduces residual stresses and distortion. Distortion can pose a major problem, since the final product is not the desired shape. To alleviate certain types of distortion the workpieces can be offset so that after welding the product is the correct shape. The following pictures describe various types of welding distortion:

Transverse shrinkage

 

Angular distortion

 

Longitudinal shrinkage

 

Fillet distortion

 

Neutral axis distortion

Gas inclusion

Gas inclusions is a wide variety of defects that includes porosity, blow holes, and pipes (or wormholes). The underlying cause for gas inclusions is the entrapment of gas within the solidified weld. Gas formation can be from any of the following causes: high sulphur content in the workpiece or electrode, excessive moisture from the electrode or workpiece, too short of an arc, or wrong welding current or polarity.

Lack of fusion and incomplete penetration

Lack of fusion is the poor adhesion of the weld bead to the base metal; incomplete penetration is a weld bead that does not start at the root of the weld groove. Incomplete penetration forms channels and crevices in the root of the weld which can cause serious issues in pipes because corrosive substances can settle in these areas. These types of defects occur when the welding procedures are not adhered to; possible causes include the current setting, arc length, electrode angle, and electrode manipulation. Defects can

be varied and classified as critical or non critical. Porosity (bubbles) in the weld are usually acceptable to a certain degree. Slag inclusions, undercut, and cracks are usually non acceptable. Some porosity, cracks, and slag inclusions are visible and may not need further inspection to require their removal. Small defects such as these can be verified by Liquid Penetrant Testing (Dye check). Slag inclusions and cracks just below the surface can be discovered by Magnetic Particle Inspection. Deeper defects can be detected using the Radiographic (X-rays) and/or Ultrasound (sound waves) testing techniques.

Lamellar tearing

Lamellar tearing is a type of welding defect that occurs in rolled steel plates that have been welded together due to shrinkage forces perpendicular to the faces of the plates. Since the 1970s, changes in manufacturing practices limiting the amount of sulfur used have greatly reduced the incidence of this problem.

Lamellar tearing is caused mainly by sulfurous inclusions in the material. Other causes include an excess of hydrogen in the alloy. This defect can be mitigated by keeping the amount of sulfur in the steel alloy below 0.005%. Adding rare earth elements, zirconium, or calcium to the alloy to control the configuration of sulfur inclusions throughout the metal lattice can also mitigate the problem.

Modifying the construction process to use casted or forged parts in place of welded parts can eliminate this problem, as Lamellar tearing only occurs in welded parts.

Undercut

Undercutting is when the weld reduces the cross-sectional thickness of the base metal and which reduces the strength of the weld and workpieces. One reason for this type of defect is excessive current, causing the edges of the joint to melt and drain into the weld; this leaves a drain-like impression along the length of the weld. Another reason is if a poor technique is used that does not deposit enough filler metal along the edges of the weld. A third reason is using an incorrect filler metal, because it will create greater temperature gradients between the center of the weld and the edges. Other causes include too small of an electrode angle, a dampened electrode, excessive arc length, and slow speed.

Electrode GradingThe electrodes are categorized as per the welding process. The colour of electrode also varies as per the material to be welded. The classification of electrodes is done as per AWS (American welding society).

For SMAW

Grading:- E XXX Y Z - XX

E- Electrode

XXX- Chemical composition

Y- Special alloying element

Z- High Carbon or Low carbon

XX- Type of coating used

Example- E 308 Mo L-16, Special alloying element is Molybdenum.

For GTAW & SAW

Grading:- ER XXX Y Z

ER- Electrode or Rod

XXX- Chemical composition

Y- High Carbon or Low carbon

Z- special alloying element

Role of alloying elements addedCarbon equivalent (C.E.) = C + (Mn ÷ 6) + [(Cr + Mo + V)] ÷ 5 + [(Ni + Cu)] ÷ 15

The concentration of various elements is to be fed in the above formula to get Carbon equivalent. Alloying elements are added with an intention to improve the mechanical properties of the material such as Hardness, toughness, tensile strength, corrosion resistance etc. The role of each & every element has been covered in this section.

C (Carbon)

The addition of this element increase hardness, strength and reduces toughness of the material.

Mn (Manganese)

It increases tensile strength, hardness, toughness & also acts as a de-oxidiser in molten pool. Mn range:- 0.5-0.9 %

Si (Silicon)

It preserves BCC (Body centred cubic) lattice of Fe at all temperatures.

P (Phosphorus)

It decrease toughness & temper embrittlement. Its content should be less than 1%.

S (Sulphur)

This element decreases toughness, forgeability.

Cu (Copper)

This increases forgeability

Cr (Chromium)

It increases hardenability, high temperature strength & hardness.

Ni (Nickel)

It increases strength, toughness & also acts as an Austenite stabilizer.

Mo (Molybdenum)

It increase hardenability & pitting corrosion resistance.

Nb (Niobium)

It acts as a carbide stabilizer in SS.

V (Vanadium)

It increases hardenability and is also used in HSS cutting tool.

Al (Aluminium)

It acts as de-oxidizer, N2 (nitrogen) fixing agent, grain refining additive.

N (Nitrogen)

It facilitates grain refinement & increase toughness.

Sensitization

This is a type of defect which is generally seen in case of Austenitic stainless steels (AISI 304 & 316). Because of high Cr content, when the material is subject to service temperatures such

As 400-600 deg. Celsius then, C shows great affinity to form carbide with Cr and forms a stable Chromium carbide (Cr23C6). If the material is kept at the same temperature for a longer duration then, the chromium carbide layer starts depleting thus forming a void at its position. The void so formed is highly prone to attack by foreign materials added & corrosion.

At LTPC, even materials such as P91/P92, P11/P22 also possess a good Cr content and are often heated to temperatures above 700 deg. Celsius as a part of PWHT. Here we don’t get to see sensitization because of low Cr content when compared to that in Austenitic SS (18-32% of Cr). In case of alloy steels, Cr shows very less tendency to form carbide with Carbon.

Shielding Gas, Backing Gas, Trailing Gas

All varieties of gases use Argon (Ar) as the primary element.

No. of Ar tanks at LTPC:- 2 Make:- Linde & Praxair Capacity:- 6 Kl (kilo litres) Pressure:- 18 kg/cm^2

Shielding Gas

Argon is the only element. It is used to shield the welded portion from oxidation while GTAW is in progress. Discharge is through Argon torch. Flow rate is 8-15 litres per minute (lpm).

Backing Gas

Again, Argon is the only element. It is used in materials with Cr content greater than 2.25%. The groove which is supposed to be welded is packed properly from inside. Argon torch is passed inside via a small opening made in the packing material. The gas is used to heat up the groove and is continued for maximum 3-4 weld passes of SMAW. It provides additional backing in preventing oxidation of weld portion. Flow rate is 10-20 lpm.

Trailing Gas

As the name suggests, it moves behind the electrode holding the filler wire. It goes on shielding the portion which has already been welded.

Automatic Welding Machine Column & Boom type

Operation:- Pipe Welding TIG, MIG, SAW Capacity:- 2”-24” (OD) Make:- Nanjing Auto Electric Co. Ltd., China Welding source:- Miller USA Input power:- 22 KW Boom lifting stroke:- 900 mm Boom lifting speed:- 420 mm/min Boom forward & backward stroke:- 420 mm Boom forward & backward speed:- 400 mm/min No. of machines:- 7

Quality Assurance/Quality ControlQuality department is providing services to LTPC in the areas like QA (Quality Assurance), QC (Quality Control) & interface with product related statutory bodies. Quality engineers are responsible to check the quality of a particular operation carried out on the pipe spools like for ex- quality of welded portion, quality of edge prepared, quality of packing of spools etc.

The department makes an ITP (Inspection testing plan) which varies with the material & type of order, a thorough study of the ITP is done thenafter. The observations of each & every inspection are noted down and the presence of any flaw is immediately reported by raising NCR (Non-conformity report) indicating that a particular examination was not done properly.

Quality engineers are also responsible to check the quality of incoming raw material as per the MTC (Material testing certificate) given by the vendor. The MTC is thoroughly analysed and orders for the final dispatch of spools is given thereafter. All types of NDE’s (Non-destructive examinations) come under the control of quality department.

Radiography testing & Film preparation

This examination is used to analyse the inside surface defects. It makes use of γ (gamma) radiations in determining the defects.

Source used

1) Iridium 192 (Ir):- Used for pipe thickness up to 50 mm, Energy- 0.49 MeV2) Cobalt 60 (Co):- Used for pipe thickness above 50 mm, Energy- 1.17, 1.31

MeV

Here, Cobalt 60 & Iridium 192 are obtained from the bombardment of Cobalt 59 & Iridium 191 respectively by neutrons.

Exposure time

It is defined as the time duration for which the film is supposed to be exposed to the incoming γ radiations.

Techniques of RT

1) Panoramic:- In this technique of RT, the source through which radiations get emitted is kept at the centre of the pipe spool & beneath the portion which has to be tested. As a result, radiations are emitted in all possible directions and we can get an image of the welded surface, wherever the RT film has been placed. If the portion to be tested is not near to the extreme ends of the pipe, but somewhere in between, in that case Spiders are put into action which decide the centre of the pipe as well as serve as a stand for the source. The instrument through which the radiations are emitted is known as a Camera.

2) SWSI (Single wall single image):- This is similar to panoramic testing, but in this the source need not to be placed at the centre. The radiations are supposed to penetrate through a single wall, the film is attached on the outer side of the wall & thus an image of the surface is obtained which is later on prepared in the Dark Room.

3) DWSI (Double wall single image):- In this method, the source is placed at one end of the pipe cross-section & the film is placed on the other end so that the radiations will have to penetrate through double walls.

4) DWDI (Double wall double image):- Films are placed on 2 different walls (ex- upper wall & lower wall) and the source is kept at a certain distance in the pathway of the films.

Pentameter

Pentameters are used to ensure that a sharp image of the portion to be tested is formed on the films. Pentameters are termed as Image Quality Indicators (IQI). Pentameter can be either wire-type or hole-type.

IQI (wire type) grades at LTPC:-

1) 0-9 mm thickness (1A)2) 10-49 mm thickness (1B)3) 50-100 mm thickness (1C)

Film Development

Exposed filmBrought to Dark roomDipped inside DeveloperStop BathFixerRunning WaterWetting Agent

The film is kept inside two sheets of Lead (Pb), inner & outer as Lead prevents the incoming of back-scattered radiations & surrounding light source- thus preventing the film from getting disturbed.

Developer:- It helps in the development of image formed in the film. Film should be kept inside developer for maximum 8 min. Developer is changed after every 2-3 days.

Stop bath:- This contains pure water. It obstructs the over-development of image due to the action of the developer. Film should kept inside this for maximum 1 min. It is changed after every 5-6 days.

Fixer:- This solution is acidic in nature & is responsible for the removal of Silver Bromide (AgBr) from the existing film. It’s function is to fix the image formed.

Running water:- This is used to wash any kind of dust particles settled down on the film. It is changed in every 6-7 hrs.

Wetting agent:- This is used to improve the properties of gelatine in the film. Because of this wetting agent, water particles will not settle on the film & will easily get washed away. It prevents the formation of any water marks on the image.

Film preparation is performed in a Dark room where the temperature is kept between 18-22 deg. Celsius so that normal can’t spoil the film.

Film thickness:- 2 mm for Co60 & 1mm for Ir192

Film matrix:- Polyester + Gelatine + AgBr + Gelatine

Ultrasonic testing

This method too is used to check & examine the inside surface defects. It makes use of the highly energetic Ultrasonic waves. A probe is kept on the surface which emits Ultrasonic waves. The waves retreat and are detected by another probe, hence indicating presence of a defect.

Ultrasonic travelling speed in different mediums

Steel:- 5920 m/s

Aluminium:- 6300 m/s

Perplex/Plastic:- 2750 m/s

Water:- 1450 m/s

Air:- 332 m/s

UT Machine:- GE Sensing & Inspection Technologies USM 35

Frequency of waves:- 1-5 MHz

UT Techniques

1) Pulse echo & through transmission, through transmission is mostly carried out in concrete at low frequency (0.1-0.4 MHz)

2) Normal beam & angle beam3) Contact & immersion

1 & 2 are performed at LTPC.

Zones in Sound beam

1) Dead Zone2) Near Zone or Fresnel Zone3) Far Zone or Fraunhofer Zone

Visual Display

These displays are used to evaluate the soundness or quality of material. Various scans are A- Scan, B-Scan, C-Scan out of which, B&C Scans are recordable.

Magnetic Particle Testing

This type of testing is used to detect surface defects by virtue of Magnetic field lines.

A machine known as ‘Yoke’ is used to detect the defects. Yoke has got two poles, North & South poles. The magnetic field lines flow in between the poles. The machine is kept on the surface of the pipe spool to be tested & is moved over it in a random fashion. The presence of any surface defect will stand as a hindrance to the flow of magnetic field lines.

In order to facilitate the flow of magnetic field lines, a solution of Iron particles + Water is continuously sprayed on the surface along with the machine movement. The path of magnetic field hindered by the defect will get fulfilled with the iron particles coming over that particular portion, hence completing the flow of magnetic field lines. A zig-zag irregular line will appear over the defective surface, line being formed by the iron particles.

If there are zero defects then, iron particles will get accumulated at North & South poles of the machine respectively. The defects portions are grinded at a later stage.

Positive Material Identification (PMI)

This examination is governed by the properties of X-rays. It is used to determine the percentage of various alloying elements in alloy steel such as P91/P92/P11/P22 etc.

This also uses a gun-type machine which emits highly energetic X-rays on the portion to be tested. The X-rays excite the atoms of each & every element, absorbing the frequency of the elements released in the excitation process. The returning X-rays give information about the concentration of alloying elements.

Analyser used:- Metorex X-Met 2000, Niton Metal alloy analyser (800 series)

Methods not acceptable for alloy testing in PMI:-

1) Spark testing- It may hamper the base material. Temperature is around 3000-4000 deg. Celsius.

2) Chemical spot testing3) Electro-analyser4) Eddy current separators5) Thermo electric separators

Dye- Penetrant Testing (DPT)

This method is used to check & examine surface defects. This unique method is based on the capillary action of Dye used.

The process

A combination of 3 different solutions is used in DPT. The solutions are- Cleaner, Dye & Developer.

1) Initially, cleaner is applied on the joint & is allowed to stay for maximum 2 min, known as Dwell time.

2) Thenafter, Dye is applied on the joint using brush. The minimum dwell time for the dye being 10 min. The dye is allowed to get dry.

3) Cleaning of the joint is done again using cleaner & cotton.4) In the terminating stage, developer is applied in the form of spray on the joint to

distinguish between the defect & non-defective area in the welded zone.

Developer:- Liquid powder made of chlorine & sulphur

Cleaner:- Chlorine & sulphur mixture

IRN/ICS & DCN

IRN- Inspection release note

ICS- Inspection clearance sheet

DCN- Design change note

ICS or IBR is given by the quality department which stands as a clearance that now the pipe spool is ready for further inspection by TPI (Third part inspection) or IBR (Indian boiler regulation). These notes are usually given after FD (final dimension).

In case there is a flaw in the structure of the pipe spool which differs from the figure shown in the approved design, a DCN can be raised to report this difference so that the material can be changed accordingly.

ConclusionThe 4-week training programme at L&T’s piping center facility situated at Hazira Manufacturing Complex brought the motto of L&T- “It’s all about Imagineering”, in true sense for me. The various processes at the shop floor & the working culture of L&T through which I went in these 4 weeks taught me the very important lesson of smart work in an organization, supported by the services which technology can offer in today’s world.

The learnings gained at LTPC are:-

The variety of processes inside the shop floor provided me with an in-depth knowledge about machinery & manufacturing. I got to know about what is a ‘Pipe Spool’ & how it is manufactured for various industries.

I got to know about various welding processes & their specifications. WPS (Welding procedure specification) came as a new entity as I got to see such thing for the first time. The various heat treatment processes going on, the need to do them & the technicalities associated with them made my concepts crystal clear & profound.

A study conducted on the time cycles for Carbon steel & Alloy steel (P91) along with the comparison done between the two cycles gave me an idea about the time consumption in a particular process due to variation in size & material. The cycle time study also gives me a breakthrough regarding in what ways the time invested can be reduced in a particular process.

A comparison was done between the fabrication of Carbon steel, Alloy steel (P91) & Stainless steel, the observations & inference were noted down which gave me knowledge about why there is a difference in the manufacturing of spools of these 3 different materials.

I also came to know about HIRAC (Hazard identification & risk assessment control) which involves a detailed analysis on process related hazard & their mitigation.

At LTPC, I got an overview of how a particular project is managed, right from the preparation of design to the placing of purchase order till the monitoring of processes & finally ensuring that the Pipe spool reaches to the client safely.

The experience gained at L&T Piping centre is definitely going to provide me the wisdom & zeal to achieve success & give my level best in upcoming future endeavours.