Technical Report

Example

(1)

Chartered (CEng)

Membership

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A TECHNICAL REPORT IN SUPPORT OF APPLICATION FOR CHARTERED MEMBERSHIP OF IGEM

DESIGN OF 600 (103 BAR) 820MM SELF SEALING REPAIR CLAMP AND VERIFICATION USING LIMIT-LOAD ANALYSIS METHOD

DECEMBER 2011

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Table of Contents

1. DECLARATION OF AUTHENTICITY .................................................................................... 3

2. INTRODUCTION ........................................................................................................................ 3

3. REVIEW OF DESIGN SPECIFICATION ................................................................................. 4 3.1 Review Customer Specification .............................................................................................. 5 3.2 Develop table of key design/service criteria .................................................................... 5 3.3 Determine Appropriate Standards to Apply to Design .............. Error! Bookmark not

defined. 3.4 Initial Decision on Manufacturing Process & Suitable Materials for Clamp Body

....................................................................................................... Error! Bookmark not defined. 3.5 Suitable Seal Materials .......................................................... Error! Bookmark not defined.

4. DEVELOPMENT OF DESIGN BY FORMULA CALCULATIONS TO DETERMINE BASIC STRUCTURAL GEOMETRY PRIOR TO MODELLING FOR ANALYSIS PURPOSES................................................................................................................................... 6

4.1 Determine Minimum Shell Thickness (see Appendix v, Section A) ........................... 6 4.2 Determine Clamp Body Thickness. Minimum Shell Wall Thickness ........................ 6 4.3 Determine Number, Dia., Grade of Bolts Using ASME VIII, Division2, Appendix 3-

320 (see appendix v, Section C) ......................................... Error! Bookmark not defined. 4.4 Determine Clamp Side Bar Dimensions (see appendix v, Section D) .............. Error!

Bookmark not defined. 4.4.1 Minimum Lug Height for Stress Limit - (see appendix v, Section D.1) ............................. 7 4.4.2 Bolt Prising - (see appendix v, Section D.2) .................. Error! Bookmark not defined. 4.4.3 Minimum Lug Height for Deflection Limit - (see Appendix v, Section D.3) ....... Error! Bookmark not defined. 4.4.4 Test Pressure (see Appendix v, Section D.4) .............................................................................. 8

5. PRODUCTION OF SOLID MODEL OF PROPOSED GEOMETRY .................................... 8

6. SIMPLIFICATION OF MODEL FOR ANALYSIS PURPOSES ............................................ 9

7. IMPORTING MODEL INTO FINITE ELEMENT SOFTWARE .......................................... 9

8. MESH MODEL, APPLY CONSTRAINTS & LOADINGS .................................................... 10

9. SOLVE ANALYSIS .................................................................................................................... 13 9.1 Limit Load Analysis (Protection against plastic collapse) ......................................... 14 9.2 Elastic Analysis (Protection against local failure) ......................................................... 14 9.3 Ratcheting Assessment-Elastic Stress Analysis (Protection against cyclic loading

(not fatigue) ................................................................................................................................ 14

10. INTERPRETATION OF RESULTS ........................................................................................ 15 10.1 Limit Load Analysis ................................................................. Error! Bookmark not defined. 10.2 Elastic Analysis ......................................................................... Error! Bookmark not defined. 10.3 Ratcheting Assessment – Elastic Stress Analysis ......... Error! Bookmark not defined. 10.4 Bolt Areas ................................................................................... Error! Bookmark not defined. 10.5 Deformation on Joint Plane ................................................. Error! Bookmark not defined. 10.6 Conclusion .................................................................................................................................... 15

11. COMPILATION OF REPORT SUMMARISING APPROACH & RESULTS .................... 16

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12. REVIEW BENEFITS/LIMITATIONS OF USING FINITE ELEMENT ANALYSIS FOR PRESSURE SYSTEM COMPONENTS ................................................................................... 16

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1. DECLARATION OF AUTHENTICITY

I declare that this Technical Report represents an original piece of work by Antony

Nicholls and that the statements made herein are true to the best of my knowledge.

Signature: ----------------------------------------------

Name: Adam Thistlethwaite BEng MSc CEng MIGEM

Membership No. 800117

Engineering Manager – Furmanite EMEA

Offshore Panel Chairman – Pipeline Industries Guild

2. INTRODUCTION

I will demonstrate my knowledge and understanding of engineering principles to M

Eng. Level by undertaking the design process for a high pressure self sealing repair

clamp.

My previous employer, Furmanite, kindly offered to provide me with a project

placement during November 2011 so that I could design a clamp as the subject

matter of my Technical Report.

The clamp will be designed in accordance with API Specification 6H, which requires

design to be in accordance with the methodology set out in ASME Boiler and

Pressure Vessel Code design Based on Stress Analysis.

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I will develop the basic design using formula calculations to determine basic

structural geometry (bolt sizes etc) and carry out stress analysis using finite element

analysis of a solid model of the clamp.

The design will demonstrate conformance to the requirements of the referenced

standards for gross plastic deformation, progressive plastic deformation, bolt areas

and service stresses and deflection on the joint faces.

My role in the project will be as Design Engineer with responsibility for the product

design.

Drawing number UKE06163-DWG-03 (see Appendix i) refers to a self sealing clamp

suitable for an 820mm pipe which was originally designed to ASME VIII Division1.

My project will use the same customer specification and drawing as the basis for a

design to ASME VIII Division 2. Division 1 is based on design by rule (code

specified Formulae) and Division 2 is design by analysis (more rigorous calculations

involved). There are also numerous differences regarding material testing, NDE

requirements and low temperature impact testing that should be reviewed prior to

selecting a design approach. In short: Division 2 provides an engineered vessel with

calculated stresses closer to real stresses, combined with more rigorous testing,

allowing for savings in material costs (thinner parts may be used).

3. REVIEW OF DESIGN SPECIFICATION

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3.1 Review Customer Specification

The customer specification details are recorded using a Furmanite

Specification Sheet (see Appendix ii) which utilises drop down boxes to limit the

range of options and to guide the sales department. This information was used

to define the specification of the clamp designed.

3.2 Develop table of key design/service criteria

Furmanite uses a Design Specification Review process (see Appendix iii) which

set out the design requirements in a standard tabular manner which aides the

review process and contributes to the design of a fit for purpose product.

Furmanite’s offers self seal clamps that conform to API 6H. The key

requirements for the project are:

Feature Requirement

Design Pressure 103.42 Bar (1500 Psi)

Design Temperature

-29°C to 40°C

Nominal Pipe Dimensions

Nominal pipe O/D 820.00mm

Pipe tolerance as per API 5L will be apply (+ 0.75%, -0.25%) Ovality limits will be assumed to be within the envelope defined above.

Max –826.15mm Min –817.95mm

Defect Envelope 152mm Between Seals

Materials Shell Material - ASTM SA 516 Gr 60

Bolted Lugs – ASTM SA 516 Gr 60

Bolts – ASTM A193 B7

Nuts – ASTM A194 2H

Corrosion Allowance

3.2mm corrosion allowance

Design Calculations

Generally in accordance with the requirements of ASME VIII Div. 2

Content Methane

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Sections redacted.

4. DEVELOPMENT OF DESIGN BY FORMULA CALCULATIONS TO DETERMINE BASIC STRUCTURAL GEOMETRY PRIOR TO MODELLING FOR ANALYSIS PURPOSES

4.1 Determine Minimum Shell Thickness (see Appendix v, Section A)

The determination of the shell thickness is derived from the basic formula for

hoop stress:

t

DPH

2

Where

H = hoop stress (MPa)

P = internal pressure (MPa)

D = Inside diameter (mm)

t = thickness of wall (mm)

I have calculated the minimum wall thickness in accordance with ASME VIII

Division 2, 2007 Part 4.

Main Shell thickness mmtD 729.33min.

Actual corroded shell thickness mmtDa 000.39

The final shell wall thickness of 42.5mm exceeds the minimum

requirements.

4.2 Determine Clamp Body Thickness. Minimum Shell Wall Thickness

Requirements & General Membrane Stress Intensity Limits (at design &

test conditions) Based on Formula for Cylindrical Shells Given in ASME

VIII 2, Appendix 4-222. (see Appendix v, Section B).

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API 6H requires a check using a calculation for general membrane stress at

test pressure. The maximum membrane stress ( mfactP ) must not exceed 83% (

mP ) of the yield stress ( yplateS ) for the plate material

It can be seen that:

%888.81mfactP and is less than mP

Sections redacted

4.4.1 Minimum Lug Height for Stress Limit - (see appendix v, Section D.1)

The maximum bending stress occurs in the plane of the bolt

centrelines. The effective length of the lug in this plane is reduced by

the bolt holes and is calculated as follows:

BCi

ni

i BiLLe DNLL

1

Where the index i is used to identify each of the n different stud/bolt

sizes used in the sector.

The minimum allowable height for the bolting lug 1minLH , to meet the

stress limit, is given by:

2

42

1min

LH mmHL 54.811min

Sections redacted

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4.4.4 Test Pressure (see Appendix v, Section D.4)

The clamp will be tested in excess of the design pressure (a proof test)

and so the lug and bolt arrangement needs to be designed to prevent

excessive lug separation in the seal region at the test pressure.

The deflection due to bending and possible prising of the lugs should

be within the recommended allowable limit, SaY :

It can be seen from Appendix V section D.4 that the actial prising is

mmYSt 0898.0

5. PRODUCTION OF SOLID MODEL OF PROPOSED GEOMETRY

A 3D Computer Aided Design (CAD) package was used and I worked with the

Furmanite design engineer who developed the 2D design into a 3D solid model

which was then imported into the Finite Element Analysis (FEA) software.

The creation of a 3D model creates geometry that the FEA software can interpret

and use to mesh the structure (see Figure 1).

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Figure 1 - Featured 3D solid Model:

6. SIMPLIFICATION OF MODEL FOR ANALYSIS PURPOSES

Sections redacted

7. IMPORTING MODEL INTO FINITE ELEMENT SOFTWARE

I imported the de-featured 3D model (volume), which was now 1/8th of the final

product into ANSYS FEA software as Parasolid file (this is in binary format and can

communicate and migrate 3D solids which are understood by the FEA software)

which defines volumes, areas, lines and points.

Orientation of the clamp was important as Furmanite use standard macro’s in

ANSYS and manipulation and analysis are easier if conventional axis orientation is

observed. For a straight clamp the X axis lies across the half joint plane, Y axis is

normal to the half joint face and Z axis along the main centreline.

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8. MESH MODEL, APPLY CONSTRAINTS & LOADINGS

The meshing process required the volume to be divided into shell and lug

components in order to develop regular elements with minimum distortion to make

the analysis as accurate as possible. In the meshing process, I utilised 20 node

bricks for the shell and 10 node tetrahedrons for the lugs. The shell/lug interface

was meshed using 13 node pyramids, which provide a good transition between the

20 node bricks and 10 node tetrahedrons (see Figure 5).

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Figure 5 - Finite Element Mesh

Once the meshing was completed, I used a macro to define the bolting constraints

using real constant sets (see table 1), the key steps being:- create lines representing

the bolt centres (red line in Figure 5), create pre tension sections at the mid-length

point of the bolt line (green point in Figure 5) and link bolts to clamp volumes using

constraint equations which defined a rigid region.

Table 1 Real Constant Set

Real Constant

Set

Representing

Minor Thread Dia.

Minor Section Area

Area Moment of Inertia

TKY and TKZ AREA IYY and IZZ

inch mm mm2 mm4

Full Bolt 2.25 UN8 5.3254E+01 2.2274E+03 3.9479E+05

A contact surface was then defined at the half joint faces (where opposing lugs

contact one another). As only one lug was being modelled, the contact surface was

defined as being rigid and fully constrained.

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It was necessary to ensure that the model had sufficient constraints to prevent rigid

body motion, whilst at the same time not over constraining the model and inducing

unrealistic stresses and strains. As the clamp has three planes of symmetry, there

was no requirement for additional constraints. The model therefore had 6º of

freedom, that is, the model was fixed from moving in the X, Y and Z axis and rotating

(ROT) in the X, Y and Z axis. The model was then saved to the database.

The following material properties were used for the analyses; Yield Stress, Tangent

Modulus, Young’s modulus and poisons ratio(yield stress only applies to the elastic-

plastic (limit) analysis).

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Table 2 Material Properties

Material ID1

(Solid Structure)

Young’s Modulus (E) MPa 205000

Poisson’s Ratio 0.3

Yield Stress MPa 207

Tangent (Plastic) Modulus 0

Plasticity Model Bilinear Kinematic Hardening

Material ID2

(Bolts)

Young’s Modulus (E) MPa 205000

Poisson’s Ratio 0.3

Yield Stress MPa 723

Tangent (Plastic) Modulus 0

Plasticity Model Bilinear Kinematic Hardening

Material ID3

(Joint Contact)

Coefficient of Friction 0

9. SOLVE ANALYSIS

ASME VIII, Division 2, Part 5 design-by-analysis, requires that four potential failure

modes be considered:

a. Protection against plastic collapse

b. Protection against local failure

c. Protection against collapse from buckling

d. Protection against failure from cyclic loading

Failure modes a), b) and d), are all applicable to the clamp and conditions being

analysed, as the material thickness and configuration are established through

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design-by-analysis rules. The clamp will not be subjected to loads that will induce a

compressive stress field and so mode c) is not applicable in this case.

Each of the analysis runs were performed on an ANSYS model. The primary

pressure loading was applied to a set of areas called “AP_1” which represents the

pressure area of the sectioned clamp (see Figure 6).

Figure 6 - Areas on which internal pressure was imposed

9.1 Limit Load Analysis (Protection against plastic collapse)

Sections redacted

9.3 Ratcheting Assessment-Elastic Stress Analysis (Protection against cyclic loading (not fatigue)

Sections redacted

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10. INTERPRETATION OF RESULTS

Sections redacted

Figure 7 – Deflection of Half Joint Face at Test Condition

10.6 Conclusion

The design was shown to meet the requirements of the referenced standards

for gross plastic deformation, progressive plastic deformation, bolt areas and

service stresses. Deflection on the joint faces was also within acceptable

limits. The design was therefore considered to be acceptable.

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11. COMPILATION OF REPORT SUMMARISING APPROACH & RESULTS

The results of the analysis were compiled into a standard design validation report

(see appendix IX) that sets out the design specification and performance of the

clamp.

12. REVIEW BENEFITS/LIMITATIONS OF USING FINITE ELEMENT ANALYSIS FOR PRESSURE SYSTEM COMPONENTS

Sections redacted