a-1-gen-mc-sp-0001

PTTEP ARTHIT FIELD DEVELOPMENTCENTRAL FACILITIES

MATERIAL REQUIREMENTS FOR SOUR SERVICE

A-1-GEN-MC-SP-0001

CONTRACT NO . A-TPD 03-0043 This cover page is a record of all revisions of the standard/specification identified above by number and title.

All previous cover pages are hereby superseded and are to be destroyed.

B1 4-8-04 Issued for Design Siva SNT Siva BMK SWA1 28-6-04 Issued for Approval Siva SNT Siva BMKR1 19-5-04 Inter Discipline Check Siva SNT Siva

Rev. No.

Date Purpose of Issue Prepared By

Checked By

Discipline Approval

Project Approval

Client Approval

PTTEP Arthit Field DevelopmentCentral Facilities

Doc. No. A-1-GEN-MC-SP-0001 Rev. B1

Material Requirements for Sour Service of 9

TABLE OF CONTENTS

1.0 INTRODUCTION 3

2.0 DEFINITION OF WET H2S OR SOUR SERVICE 3

3.0 MATERIALS FOR SOUR SERVICE 4

APPENDIX

Appendix 1—HIC Testing 8




1.0 INTRODUCTION

1.1 This Specification defines the minimum requirements for materials to be used in wet H2S service or Sour Service. The material damage can be classified in 2 categories

--Sulphide Stress Corrosion Cracking ( SSC )

--Hydrogen Induced Cracking ( HIC ), Stepwise Hydrogen Cracking ( SWC ), Stress Oriented Hydrogen Induced Cracking ( SOHIC ) and Hydrogen Blistering

1.2 SSC is a Hydrogen embrittlement phenomenon caused by diffusion of Hydrogen into the material when subjected to tensile stress. SSC occurs in the presence of hard material, high stress level and wet H2S solution. Preventive measures are controlling the material hardness and reducing the stress level by heat treatment ( in some cases ).

1.3 Blistering, Hydrogen induced Cracking ( HIC ), Stepwise Cracking ( SWC ) and Stress Oriented Hydrogen Induced Cracking ( SOHIC ) propagate in a stepwise fashion like lamellar tearing.

1.3.1 Hydrogen Blistering

Atomic Hydrogen produced during reaction with steel diffuses to the locations of non-metallic inclusions or voids present in the steel and gets converted to molecular Hydrogen. As molecular Hydrogen cannot diffuse into metal, this process increase the concentration and pressure of molecular Hydrogen at the inclusions resulting in localised yielding and blistering

1.3.2 HIC or SWC

Atomic Hydrogen diffuses to the areas of small and moderate sized laminar cracks in the metal and gets converted to molecular Hydrogen. As molecular Hydrogen cannot diffuse into metal, this process increase the concentration and pressure of molecular Hydrogen resulting in localised yielding and linking of adjacent planar cracks to form HIC / SWC in the through thickness direction.

1.3.3 SOHIC

This is a combination of HIC and SSC. This damage occurs in locations which are susceptible to laminar cracking in the presence of stress. In these cases, when the metal is subject to stress, small laminar cracks get lined up in the through thickness direction and step cracks form between them. They are generally found in weld Heat Affected Zones.

2.0 DEFINITION OF WET H2S OR SOUR SERVICE

2.1 Sour service requirements for SSC will apply when the conditions as defined in NACE MR0175 are present.

2.2 Requirements for HIC, SWC, SOHIC and Hydrogen blistering will apply when the partial pressure of H2S in equilibrium with the process media exceeds 0.0035 bar ( abs ) in the presence of an aqueous phase.




3.0 MATERIALS FOR SOUR SERVICE

3.1 General SSC requirements

3.1.1 All materials exposed to sour service media, shall meet the requirements of NACE MR0175 except as modified in this specification.

3.1.2 Materials shall be selected from those permitted in NACE MR0175.

3.1.3 All castings shall be suitably heat treated after any welding including repair welding. Recommended heat treatments are as follows

--Carbon and Carbon Manganese Steels—Thermal Stress Relief

--Austenitic and Duplex Stainless Steels—Solution Anneal

--Martensitic Stainless Steel—Reheat treat or double temper per NACE MR 0175

3.1.4 All carbon steel materials shall be supplied in normalised condition. Hot finished material is not acceptable.

3.1.5 All internal bolting inside vessels, shall meet NACE MR0175.

3.1.6 For shell & tube heat exchangers, carbon steel tube bundles need to undergo PWHT if tube ends are welded to the tubesheet.

3.1.7 Nitrile ( NBR ) and Hydrogenated Nitrile ( HNBR ) elastomers are acceptable for H2S levels of 10 to 100 ppm and 100 to 1000 ppm respectively based on seal geometry and temperature. For H2S levels upto 5%, FKM “Viton “ type fluoroelastomers or TFEP “ Aflas “ shall be used. Above 5% H2S level, EFKM perfluoroelastomers ( Chemrez or Kalrez ) shall be required. PTFE has excellent H2S resistance.

3.2 General HIC / SWC Requirements

3.2.1 Lower pH and higher CO2 in the presence of H2S, will increase Hydrogen diffusion rate and hence increase the susceptibility to HIC / SWC.

3.2.2 Material should be supplied in Normalised condition. TMCP and Quenching and Tempering is acceptable subject to Purchaser’s approval.

3.2.3 Heat Treatment

Vessels shall undergo PWHT irrespective of wall thickness. PWHT requirements for piping shall be as per ASME B 31.3 and NACE MR0175. For Carbon steel, minimum PWHT temperature and time should be 610 Deg C and 1 hour.

3.3 Plates

3.3.1 Carbon steel plates shall conform to ASTM A 516 or A 537 specification with modifications as listed below. Increase of strength increase susceptibility to HIC / SWC. Maximum tensile strength allowed for process vessel plates is 80 Ksi.

3.3.2 Manufacturing Process




Clean steel with homogenous microstructure provides optimum HI / SWC resistance. Very low Sulphur and Phosphorous and inclusion shape control using Calcium decrease the susceptibility to HIC / SWC. The steel shall be vacuum treated, fully deoxidised, desulphurised and dephosphorised. Calcium treatment shall be applied for inclusion shape control except that it need not be applied to plates with very low Sulphur levels ( below 0.001 % ). The Calcium content should not exceed 3 times Sulphur content. Manufacturing or rolling process shall ensure a homogenous microstructure without any ferrite / pearlite banding. One specimen shall be examined for microstructure for the degree of banding as per ASTM E 1268

3.3.3 Based on product analysis, the steel composition shall be restricted as follows, except where the standard material specification is more restrictive:

Element

Max % Element Max %

C 0.20 V 0.015

Mn 1.30 Nb 0.015

P 0.01 Ti 0.02

S 0.002 B 0.0005

Si 0.40 Cr + Mo 0.3

Cu 0.40 Ni + Cu + Cr + Mo

0.7

Ni 0.40 V + Nb 0.02

Cr 0.30 Carbon Equivalent ( per Section 3.1.3.2 )

0.43

Mo 0.12

Carbon Equivalent based on the following formula, shall not exceed 0.43

3.3.4 Thru thickness ( Z quality ) steel provides better resistance to HIC / SWC. All plates shall meet the through thickness testing requirements of ASTM A770 S3, with a minimum area reduction of 35%. HIC tested plates in accordance with this specification is acceptable in lieu of through thickness tested material.

3.3.5 Plate material shall be HIC tested in accordance with this specification

3.3.6 Lamination Check

Plates shall be ultrasonic tested for laminations in accordance with EN 10160, grade S2E2.

3.4 Flanges and Forgings




3.4.1 All carbon steel flanges and forgings shall conform to ASTM A105N or A 350- LF2 with the following composition restrictions

Carbon : 0.25 wt % max

CE : 0.43 max

3.5 Seamless Pipes

Seamless pipe shall be in accordance with ASTM A 106 Grade B or A 333 Grade 6 with the following composition restrictions

Carbon : 0.23 wt % max

CE : 0.43 max

Sulphur : 0.010% max

3.6 Seamless Fittings

Seamless fittings shall be in accordance with ASTM A 234-WPB or A 420-WPL6. The requirements on Carbon Content, Sulphur content and CE shall be based on forging or pipe whichever is used as raw material, to make the finished product.

3.7 Welded Pipe and Fittings

Welded Fittings shall be in accordance with ASTM A 234 WPB or A 420-WPL6. Plate used for manufacture of these welded fittings shall conform to the requirements specified for plates in this specification. Welding procedures used shall also meet this specification.

3.8 Valves

All the wetted parts shall meet the requirements of NACE MR0175. Items which are not freely vented to atmosphere such as insulated and buried valve and bolts inside flange protectors etc., where leakage could cause a sour environment, shall meet NACE MR0175 and this specification. Where plated components are used, the parent metal on which the plating is deposited, shall conform to this specification. Any welding or weld repair on a cast component which is exposed to the sour medium, shall undergo PWHT. All valve springs shall be made of materials meeting NACE MR0175. In addition, UNS N07090 ( Nimonic 90 ) is also acceptable. Packing shall be compatible with the stem material. Uninhibited graphite or carbon type packing is not acceptable

3.9 Bolting

All bolting shall be ASTM A 193-B7 and A 194-2H or A 320-L7 and A 194-7 if the flanges are not insulated or covered by flange protectors. Otherwise these bolting shall be ASTM A 193-B7M and A 194-2HM or A 320-L7M and A 194-7M.

3.10 Pipelines

Line pipe specifications for sour service shall be in accordance with the respective technical specification. Production control tests need to be carried out on all line




pipes used on pipelines to demonstrate their acceptable resistance to HIC using NACE TM0284 method. HIC testing and other requirements shall be as per this specification. For welded linepipes, the plates used and welding / fabrication shall meet the requirements of this specification.

3.11 Welding Requirements

3.11.1 Normally forgings or flanges will have higher carbon content and higher carbon equivalent compared to plates or pipes. Material used for welding procedure qualification tests shall have CE equivalent or higher than the material used for production.

3.11.2 All pipework shall use a minimum of 2 weld passes

3.11.3 Weld metal deposit shall not contain more than 1% Nickel.

3.10.4 Each Welding Procedure Qualification test shall include a macro and hardness test. The readings shall extend from unaffected base material on one side, across the weld to unaffected base metal on the other side. The traverses shall be as specified below. One 2 mm below the outer surface, one 2 mm below the inner surface and one across the centre. The distance between measurements across the weld shall not exceed 2 mm. No part of the weld, HAZ or base metal shall exceed 248 HV 10. for Carbon Steel. For other materials, the maximum hardness requirements shall be as per NACE MR0175.

3.10.5 The production welds shall be transverse weld hardness tested using portable Vickers hardness tester as per ASTM E 110. The hardness tests shall be carried out on the inside surface for vessels and outside surface for piping. Where PWHT is mandatory, production hardness tests shall be carried out only after PWHT. One set of hardness measurement shall be carried out for each welding procedure and for each 10 m length of finished weld. No part of weld, HAZ or base metal shall exceed 248 HV 10 for Carbon Steel. For other materials, the maximum hardness requirements shall be as per NACE MR0175.




Appendix-1

HIC Testing

Material inspection certificates shall be as per EN 10204, type 3.1C

HIC sensitivity tests shall be carried out in the solution prescribed below. The plate materials shall be tested at a frequency of one test per heat (the thickest & thinnest plates of the same heat shall be tested).

Testing shall be done as per NACE TM0284 using Solution A.

The acceptance criteria shall be as follows:

CLR% (max)

CTR% (max)

CSR% (max)

Average 5 1.5 0.5

Single 7 2 0.7

CLR—Crack Length Ratio

CTR—Crack Thickness Ratio

CSR—Crack Sensitivity Ratio

The maximum individual crack length on any section shall not exceed 5 mm. If any specimen fails to meet the above acceptance criteria, the heat of steel tested shall be rejected.

One specimen shall be examined for microstructure for the degree of banding as per ASTM E 1268. Micro indentation hardness tests are not required.

Following information shall be provided in addition to that required by NACE TM0284:

Location and dimension of specimens

Full chemical analysis of material tested including analysis for micro alloying elements

Results of cracking evaluation indicating individual CLR, CTR and CSR for each section and also averaged over 3 sections, and acceptable / not acceptable.

Photomicrographs of the specimens showing cracking and / or blistering, together with photomicrographs of adjacent material structures and of bulk material structure (samples) used to assess microstructure banding:

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