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Petroleum Development Oman L.L.C.
Materials Selection & Corrosion Control for Surface Operating
Process Facilities
Document ID SP-2161
Document Type Specification
Security Restricted
Discipline Materials & Corrosion
Owner UEOC
Issue Date September 2014
Version 0
Keywords: This document is the property of Petroleum Development Oman, LLC. Neither the wholenor any part of this document may be disclosed to others or reproduced, stored in a retrieval system,or transmitted in any form by any means (electronic, mechanical, reprographic recording orotherwise) without prior written consent of the owner.
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Approval and Issue Record
Issu
e No
DateDescription
(see Revision Record for
details)
Author
(name)
Approved
(name)
1 September-14Original issue under PDO
SP-2161
Pedro RinconSteve Jones
Janardhan SaithalaCheng Ai Khoo
Nasser Behlani
Revision Record
Issue No Descrip tion of Revision
0 Original Issue under PDO SP-2161
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Table of Contents
1 INTRODUCTION...................................................................................................................................... 6
1.1 PURPOSE .............................................................................................................................. 6 1.2 SCOPE................................................................................................................................... 6 1.3 SPECIFICATION OWNERS RESPONSIBILITY ............................................................ ................. 7 1.4 R EVISION AND CHANGES TO THE DOCUMENT ................................................................. ...... 7 1.5 DEFINITION OF TERMS .......................................................................................................... 7 1.6 ABBREVIATIONS & ACRONYMS .................................................... ....................................... 8
2 HIERARCHY OF STANDARDS ........................................................... ................................................ 10
3 MATERIALS SELECTION PROCESS ............................................................ .................................... 11
3.1 GENERAL ........................................................................................................................... 11 3.2 TECHNICAL I NTEGRITY ASPECTS ........................................................................................ 11
3.2.1 Health safety and environment ................................................................ .......................... 11 3.2.2 Sustainable development .................................................................................... ............... 11 3.2.3 Philosophy ............................................................... .......................................................... 11
4 MATERIALS SELECTION METHODOLOGY ................................................................................. 14
4.1 I NFORMATION R EQUIREMENTS FOR MATERIALS SELECTION STUDY .................................. 15 4.2 DELIVERABLES OF MATERIALS SELECTION IN VARIOUS PROJECT PHASES ........................... 17 4.3 FACTORS AFFECTING MATERIALS SELECTION .................................................................... 25
4.3.1 Information required and review of factors affecting materials selection ......................... 25 4.4 APPLICATION OF CARBON STEELS....................................................................................... 25 4.5 DEGRADATION MECHANISMS ......................................................................................... .... 25 4.6 ECONOMIC ASPECTS OF MATERIALS SELECTION ................................................................. 30 4.7 NON- OPERATIONAL CONSIDERATIONS ................................................................ ............... 30
5 GENERAL MATERIALS DESCRIPTION AND SPECIFIC REQUIREMENTS ........................... 31
5.1 GENERAL R EQUIREMENTS FOR SPECIFIC MATERIALS GROUP ............................................ 31 5.1.1 Sour service ................................................................................................................... .... 31
Alloy UNS N0625 ................................................................. ................................................................... ... 33 5.2 SPECIFIC REQUIREMENTS.................................................................................................... 34
5.2.1 Metallurgically bonded clad plates ......................................................... .......................... 34 5.2.2 Welding including clad and overlay equipment ................................................................ 34
5.3 PROTECTION AGAINST CATASTROPHIC FAILURE MECHANISMS ........................................... 34 5.3.1 Chloride stress corrosion cracking .............................................. ..................................... 35
5.4 PROTECTION OF STAINLESS STEELS FOR CORROSION U NDER I NSULATION (CUI) WITHALUMINIUM. 35
5.5 SEALING MATERIALS
.......................................................... ................................................ 35 5.6 AMENDMENTS TO ISO 15156 ............................................................................................. 35
6 MATERIALS SELECTION BY EQUIPMENT SYSTEMS ............................................................ .... 37
6.1 INTRODUCTION ............................................................. ................................................ 37 6.1.1 General ........................................................ ................................................................... ... 37
6.2 VESSELS AND PIPING ...................................................................................................... .... 37 6.3 PIPING, FITTINGS VALVES AND OTHER COMPONENTS .......................................................... 40 6.4 SMALL BORE INSTRUMENT, HYDRAULIC AND CHEMICAL INJECTION TUBING ...................... 40 6.5 HEAT EXCHANGERS ............................................................ ................................................ 40
6.5.1 Shell-and-tube heat exchangers ................................................................ ......................... 40 6.5.2 Plate coolers ............................................................ .......................................................... 42 6.5.3 Air cooled heat exchangers .......................................................... ..................................... 43
6.5.4 Compact coolers (printed circuit heat exchangers)........................................................... 44 6.6 GLYCOL DEHYDRATION SYSTEM .................................................................................... .... 44 6.7 FLARE & RELIEF SYSTEMS ............................................................. ..................................... 44 6.8 R OTATING EQUIPMENT ....................................................................................................... 44
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A) COMPRESSORS FOR PDO SHALL BE DESIGNED FOR SOUR SERVICE. .................................... 44 6.9 PUMPS .......................................................... ................................................................... ... 44 6.10 BOLTING ............................................................................................................................ 45 6.11 ELASTOMER SEAL SELECTION .................................................................. .......................... 45 6.12 PIPELINES ................................................................ ........................................................... 45
6.13 DRY HYDROCARBON FLOW LINES: ..................................................................................... 47 6.14 FLOWLINES ........................................................................................................................ 47 6.15 WATER I NJECTION FLOW LINES .......................................................................................... 49 6.16 FLEXIBLES ............................................................... ........................................................... 49 6.17 MULTI SELECTIVE VALVES (MSV’S) ................................................................................ 49 6.18 UTILITIES ........................................................................................................................... 50 6.19 STEAM I NJECTION SYSTEMS ................................................................................ ............... 50 6.20 ENHANCED OIL RECOVERY (EOR) ............................................................................ 50
7 MATERIALS SELECTION STUDY ROLES & RESPONSIBILITIES ............................................ 51
8 CONTENT OF MATERIALS SELECTION REPORTS .................................................................... 51
8.1 SELECT PHASE ................................................................................................................. 51 8.2 DEFINE PHASE ................................................................................................................. 51 8.3 EXECUTE PHASE ............................................................................................................. 52
9 CORROSION MANAGEMENT FRAMEWORK ............................................................................... 52
APPENDIX A: BASIC INFORMATION REQUIRED AND FACTORS EFFECTING MATERIALS
SELECTION .......................................................... .......................................................... 53
APPENDIX B: RISK ASSESSMENT ............................................................................................................. 56
APPENDIX C: CMF TEMPLATE .................................................................. ................................................ 58
APPENDIX D: FEED AND DETAILED DESIGN MSR MINIMUM STANDARD REQUIREMENTS
TEMPLATE .......................................................... ........................................................... 59
APPENDIX E: TEMPLATE FOR REQUIRED PROCESS INFORMATION IN MATERIALS
SELECTION REPORT. ................................................................................................. 62 APPENDIX F: MATERIALS SELECTION DIAGRAMS (MSD) ............................................................... 63
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1 Introduction
1.1 Purpose
The document provides the requirements on the process of materials selection and corrosion controlfor surface equipment that shall be used during project life cycle to ensure technically proven andeconomically acceptable materials selection for PDO projects. This specification also addressessome of the roles and responsibilities of projects, function, designers, contractors and vendors toensure materials are designed, manufactured, procured and constructed to meet Company specifiedtechnical requirements within agreed delivery timeframe.
The objective of this document is to achieve designs where materials are selected to maximise thelikelihood of no loss of containment for the design life at lowest life cycle cost by:
1. Ensuring acceptable corrosion rate at lowest life cycle costs2. Minimise corrosion by using resistant materials as the primary barrier
3. Design not to use chemical treatment as a barrier for on plot facilities4. Design to ensure at least one primary barrier or two secondary barriers (e.g. CRA orcorrosion inhibitor and corrosion allowance)
Materials selection and corrosion control are elements of corrosion management, and this guidelinedevelops further clarification and interpretation of CP-208 Corrosion Management Code of Practiceand DCAF requirements.
This Specification is intended for use by Petroleum Development Oman LLC (PDO), itsContactors/Subcontractors and Design Consultants and vendors for all PDO equipment and facilities.This specification covers all surface equipment from the connecting flanges to the Christmas tree.
“ If you are reading a hard copy of this standard, you should consider it uncontrolled and referinstead to the version cur rently on the PDO intranet live link or appropriate search database.”
1.2 Scope
The scope of this specification is to cover the surface facility materials selection for different phasesof the project from identify to operate phase.
This specification shall be read in conjunction with other Company, Shell and International standardssuch as DEP 39.01.10.11-Gen, 39.01.10.12-Gen and DEP.30.10.02.15 . This document providesfurther requirements on other company specifications (SPs), Shell DEPs and MESC SPEs and
International Standards for materials selection process and requirements.
In case of any conflict between this specification and other standards, this specification shall takeprecedence.
This standard defined the minimum Company requirements for selecting materials of constructionand corrosion control measures to support the corrosion management strategy for a facility within thecompany. It addresses requirement for identifying and evaluating all applicable corrosion threats,materials deterioration mechanisms, selecting optimum materials of construction, corrosion controlmeasures and appropriate corrosion monitoring measures and the data necessary to ensure therequirements of this standard are effectively implemented.
This standard does not cover downhole materials selection requirements. For downhole materials
selection, refer to DEP 39.01.10.02-Gen, DEP 30.10.02.15-Gen and WS 38.80.31.31-Gen.
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1.3 Specification owners responsibili ty
The owner of this specification, UEOC, as CFDH Materials and Corrosion, is responsible forauthorising all proposed deviations or amendments to the specification and for the instigation ofperiodic reviews and updates in accordance with Clauses 1.2 and 1.5.
The requirements of this specification shall remain in force indefinitely unless superseded by anauthorized revision.
The range of business areas and various life cycle stages of projects to which this standard appliesas below:
Al l PDO Development /Pro jects
Business Segment Upstream
StageIdentify
√
Assess
√
Select
√
Define
√
Execute
√
Operate
√
1.4 Revis ion and changes to the document
This specification will be reviewed and updated as and when required. The review authority will beUEOC, (CFDH Materials and Corrosion).
1.5 Defin ition of Terms
Company The term Company shall refer to Petroleum Development Oman L.L.C.
ContractorThe party which carries out all or part of the design, engineering,procurement, construction, commissioning or management of a project, oroperation or maintenance of a facility.
ShallThe word 'shall' used throughout this specification indicates a Contractrequirement.
ShouldThe word 'should' used throughout this specification indicates arecommendation.
UEOCTechnical Authority Level 1 (TA-1) for Materials, corrosion and integritydiscipline appointed by the Technical Director (TA0).
Sour Service As stipulated in SP-2041
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1.6 Abbreviations & Acronyms
Term Definition
AC Atmospheric Corrosion
ALARP As Low As Reasonably Practicable
BfD Basis for Design
CAPEX Capital Expenditure
CE Carbon Equivalent
CFDH Corporate Function Discipline Head
CMF Corrosion Management Framework
CORRAT Shell proprietary corrosion modelling computer program for corrosionrate: for calculating single point calculation corrosion rates (the mostbasic option in HYDROCOR)
CP Cathodic Protection
CRA Corrosion Resistant Alloy
CS Carbon Steel
CSCC Chloride Stress Corrosion Cracking
CUI Corrosion Under Insulation
DEP Design Engineering practice
EFC European Federation of Corrosion
FEED Front End Engineering Design
FMEA Failure Modes and Effects Analysis
GRP Glass Reinforced Plastic (fibreglass). Also known as Fibre ReinforcedPlastic (FRP) (fibre reinforced plastic) or Glass Reinforced Epoxy(GRE) (glass reinforced epoxy)
HE Hydrogen Embrittlement
HEMP Hazards and Effect Management Process
HIC Hydrogen Induced Cracking. Also known as SWC
HRC Rockwell Hardness
HSE Health Safety Environments
HV Vickers Hardness
HYDROCOR Shell proprietary corrosion modelling Shell computer program forcalculating corrosion rates
HRC Rockwell Hardness
MatHelp Shell proprietary system for accessing materials and corrosioninformation
MCI Materials, Corrosion and Inspection
MDMT Minimum Design Metal Temperature
NACE National Association of Corrosion Engineers
OCTG Oil Country Tubular Goods
OPEX Operating ExpenditureOPMG Opportunity and Project Management Guide
OR&A Operations, Readiness & Assurance
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Term Definition
PDO Petroleum Development Oman
PFP Passive Fire Protection
PTEPrincipal Technical Expert
PWC Preferential Weld Corrosion
RAM Risk Assessment Matrix
S-RBI Shell Risk Based Inspection (methodology)
SCC Stress Corrosion Cracking
SLC Service Life Corrosion - (total estimated wall thickness reduction ofcarbon steel over the life of a project the equipment)
SME Subject Matter Expert
SOHIC Stress Oriented Hydrogen Induced Cracking
SSC Sulphide Stress CrackingSWC Step Wise Cracking. Also known as HIC
TOL Top Of Line
WPS Welding Procedure Specification
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2 HIERARCHY OF STANDARDS
1. PDO Standards
• SP-2161 (2014): Materials Selection and Corrosion Control for Surface OperatingProcess
• SP-2041(2014): Selection of Cracking Resistant Materials for H2S-ContainingEnvironment
• SP-1246: Specification for Painting and Coating of Oil and Gas Production Facilities
• SP-2156 - Specification for use of non metallic materials in PDO
2. DEPs
• DEP 39.01.10.11-Gen: Selection Of Materials for Life Cycle Performance
(Upstream Facilities) - Materials Selection Process
• DEP 39.01.10.12-Gen: Selection of Materials for Life Cycle Performance (UpstreamFacilities) - Equipment
• DEP 30.10.02.14-Gen: Carbon Steel Corrosion Engineering Manual for UpstreamFacilities
• DEP 30.10.02.15-Gen: Materials for Use in H2S Containing Environment in Oil andGas Production (Amendments/Supplements to ISO 15156:2009)
3. International Standards
• ISO 15156-1: Petroleum and natural gas industries-Materials for use in H2S-containing environments in oil and gas production-Part 1: General principles forselection of cracking-resistant materials
• ISO 15156-2: Petroleum and natural gas industries-Materials for use in H2S-containing environments in oil and gas production-Part 2: Cracking-resistant carbonand low alloy steels, and the use of cast irons
• ISO 15156-3: Petroleum and natural gas industries-Materials for use in H2S-containing environments in oil and gas production-Part 3: Cracking-resistant CRA’s(corrosion-resistant alloys) and other alloys
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3 MATERIALS SELECTION PROCESS
3.1 General
Materials selection is primarily a process of short-listing technically acceptable materials for anapplication and then selecting the technically viable option with lowest life cycle cost for the requiredoperational life, bearing in mind Health, Safety and Environmental aspects, SustainableDevelopment, Technical Integrity and operational constraints. This is a multi-variable process, whichmight require several iterations before an optimal solution can be obtained. Part of this processshould also be to assess which systems require materials optimisation and which can use standardmaterials selection guidelines.
The materials selection process shall follow the Corrosion Management Framework (CMF) asdescribed in DEP. 39.01.10.11-Gen section 2.2.3.
3.2 Technical Integrity aspects3.2.1 Health safety and environment
Materials selection shall be in accordance with the HSE Hazards and Effect Management Process(HEMP). This process identifies and assesses HSE hazards, implements control and recoverymeasures, and maintains a documented demonstration that major HSE risks have been reduced to alevel that is As Low as Reasonably Practicable (ALARP). This shall be done for the full lifecycle ofassets and operations and uses the Risk Assessment Matrix (RAM). For High Risk and/or Severityhazards bow tie diagrams with links to relevant details should be used to demonstrate tolerability and ALARP.
3.2.2 Sustainable development
Sustainable development principles shall be applied as part of the materials selection process.During the past decade it has become clear that the availability of materials and the manufacturingcapacity for materials and products is rapidly becoming a major constraint on constructioncapabilities and hence, on energy production and development. Therefore, it is important to usematerials that are readily available and in ways that facilitate standardisation. Thus, one of theconsiderations should be to avoid mixing materials in such a way that they cannot be separatedeasily as this downgrades their value and limits their availability in the longer term.
3.2.3 Philosophy
Materials selection shall be based on the project life cycle and Basis for Design (BfD) document asdefined in Section 4.1 of this standard.
Materials of construction shall be selected to achieve a balance of minimum CAPEX with reducedoperating costs (OPEX) to maximise project value and minimise risks. The CAPEX shall be the rawmaterial and fabrication/construction costs. The OPEX shall be the corrosion protection andinspection/maintenance cost.
The materials selection process shall reflect the overall philosophy regarding design and operatingconditions, design life time, cost profile (CAPEX/OPEX), inspection and maintenance philosophy,safety and environmental profile, failure risk evaluations, remnant life assessments of existing similarequipment, lessons learnt via integrity studies, compliance with local and international regulations
and other specific project requirements.
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General Princip les
A high level materials selection, aimed at identifying unusually high cost materials is carried outduring the project Select phase and feeds into the Level 1 (CAPEX and OPEX) cost estimate (+40%/–25 %). For main process stream items, initial materials selection is carried out in the Select phase
of a project. Materials selection for secondary process streams is usually carried out in the projectDefine phase as part of the Front End Engineering Design (FEED). During the FEED, materialsselection may be optimised, with the approval of the Materials and corrosion Function, as moreinformation becomes available in order to reduce costs to a minimum in line with specific projectparameters and risk philosophy. At this stage, more refined judgements on corrosion rates, lifepredictions and risk assessments shall be carried out to ensure that the proposed materials selectionwill be fit for purpose. For long-lead and/or bulk items (e.g. Line pipe), key materials decisions shouldbe made as early as possible in the project, preferably during the Select phase, i.e., ahead of FEED.If the new project will make use of and tie into existing installations, the materials in place and theircurrent condition should be ascertained in the Select phase. Operations personnel shall be includedin the project team or consulted for these types of developments.
Materials selection is a risk based decision making process with the aim of selecting materials that
give rise to major accident hazard risks that are tolerable and ALARP. The tools of materialsselection decision making and the means of assuring (calibrating) the decision are summarised in thediagram from SP-2062. - HSE Specification: Specifications for HSE Cases:
Figure 1: Risk based decision making process
The materials selection philosophy should be one that will not require PDO values to be called upon,i.e. acceptance can be achieved by no more than internal (including Shell) peer review. In practice,the majority of materials selection decisions will be driven by reference to the GU-611 PDO codes ofpractice, specifications, procedures and guidelines; that is to say, the ‘standard materials selection’option described in this document.
The selection process is structured based on:
a) Standard materials selection
Guidance on the selection of technically proven and economically acceptable materialsselection for most equipment is given in Section 6 of this standard. Selection is based upon
the stated information on the environmental conditions for each system. Standard materialsselection is used to fill in the details for the systems that do not require materials optimisation.Some optimisation may be required on some process systems, if conditions are encounteredthat are not adequately covered in this standard, or if it is required to consider other materials
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choices, in the interest of potential cost savings. This will generally require justification basedon a life cycle cost analysis and a technical integrity verification.
For carbon steel applications, the process of corrosion control option selection, corrosioncontrol system availability and corrosion allowance selection shall follow the requirements of
DEP 30.10.02.14-Gen.
b) Experimental evaluation (specialist consu ltation)
Experimental work might be necessary to evaluate materials for specific applications. It shallbe carried out in accordance with the material testing methodology selected for the failuremodes anticipated. Where this is required to assess the suitability of the lowest cost option, itshould be carried out ahead of the Field Development Plan (FDP, in the project select phase).
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4 MATERIALS SELECTION METHODOLOGY
The standard materials selection process includes the following steps:-
a) Define the requirements and the environment
The intended design life of the proposed equipment shall be stated.
The internal and external environments for the equipment shall be defined, including any non -routine or non-operational conditions that might be encountered. The variables characterising ofthe corrosive environment shall be quantified for normal operating conditions and to some extent,for unusual or upset conditions.
At this point, the operation has to be characterised, e.g., in terms of manning levels, access byoperators, capabilities of operators, in-house or contract operated, access to supplies, spareparts availability, etc.
b) Assess the applicability of carbon steel and define possible corrosion control options
As an initial step in the materials selection process, the suitability of the potentially low costoption involving the use of carbon steel should be thoroughly investigated and evaluated to serveas a baseline against which to compare more corrosion resistant, and possibly more costly,alternatives. Part of this process will involve the calculation of the Service Life Corrosion (SLC)for the proposed operating conditions.
For the carbon steel option, possible corrosion control options to protect the steel from prematurefailure should be investigated. These could include chemical corrosion control, coatings, cathodicprotection and control of process fluids, e.g., pH stabilization and dehydration. The results ofthese studies could lead to a lower value of SLC being appropriate. This will often result in morethan one corrosion control option being taken forward for further consideration (e.g., carbon steel
with a corrosion allowance and inhibition system versus carbon steel with a (different) corrosionallowance and a dehydration system). The availability of these solutions should be taken intoaccount. For example, it is notoriously difficult to achieve a consistently high availability ofcorrosion inhibitors, so if this is considered, the training and organizational responsibilities shouldbe realized.
c) Make materials choices
Typical materials shall be selected with the aid of the guide tables for each type of equipment(see Section 6 of this standard). While a material included is technically acceptable, it will notnecessarily be the most cost-effective choice. This will often lead to more than one technicallyacceptable materials being taken forward for further consideration (e.g., carbon steel with acorrosion allowance versus one or more alternative corrosion-resistant materials).
d) Develop corrosion management framework
See Section 9 of this standard.
e) Assess economics of choices
In the final analysis, selection of the corrosion control option (which includes materials selection)is often an economic decision, assessing the total cost of each alternative over the total life of thesystem, including quantification of the risks and uncertainties (life cycle cost). These include therisk of failure of corrosion control, the economic impact of corrosion control, RBI, sandmanagement, inhibition and the possibility of market changes, whereby certain materials couldbecome more or less economic. Where the risk of failure of corrosion control is high, theconsequences should be taken into account, e.g., enhanced corrosion control measures, andenhanced inspection and repair. These will be reflected in the economic consequence of failure,as assessed in S-RBI. Operations personnel should be involved in the life cycle cost assessment
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to ensure all operating costs are considered. This work shall be completed as part of thecorrosion control options selection report and the materials selection report. It is the responsibilityof the project engineer to complete the life cycle costing. The Life cycle cost shall be completedas per DEP.82.00.10.12-Gen Life cycle costing.
f) Maintain live documents
The Corrosion Management Manual, RBI Plan and Maintenance Reference Plan are livedocuments for the lifetime of the facility. These shall be updated whenever there are (approved)materials substitutions (e.g., during procurement and fabrication), changes to the corrosioncontrol system and changes to the operation and process, and as monitoring, inspection andmaintenance data are collected during the lifetime of the facility. Service company personneloften carry out this type of data collection. Personnel involved shall be made aware of theimportance of this work.
The activities associated with the materials selection process can be represented by the flow chartshown in Figure 2.
Figure 2: Standard materials selection process
4.1 Information Requirements for Materials Selection Study
SELECT Phase
It is expected that the initial inputs will come from the defined DCAF deliverables of the Assess phaseas per the PDO DCAF Description. The process may be initiated with this information and constantlyrevisited as the inputs are further refined and the Select phase deliverables are matured ready forDefine. Materials, corrosion and Inspection (MCI) TA2 will define the required deliverables for eachproject.
Activi ty 1: Definerequirements and environment
• Production Profile – possibly Hydrocarbon Production Forecast (DCAF24 → DCAF 1482)
• Water Management Assessment (DCAF 18, GU-672 Assess andSelect)
Activity 1Activity 2
Activity 3
Activity 4
Activity 5
Activity 6
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• Operations & Maintenance Philosophy (DCAF 216 and 218)
• Risk Management Plan & Risk Register (DCAF 84 → DCAF 201) • Pipelines Flow & Flow Assurance Study (focus on scale and sand
management) – Preliminary (DCAF 33 → DCAF 110 Pipelines Flow &Flow Assurance Strategy Reports)
• Pipeline & Flowline System Conceptual Design Report (DCAF 117)
• Heat & Materials Balance Report (DCAF 108)
• Process Flow Schemes (DCAF 112)
• Chemicals Requirement Report – Preliminary (DCAF 1272)
• Utility Flow Schemes (DCAF 1360)
• Equipment Listing (DCAF 1496) Activi ty 2: Determine threatsand barriers for carbon steeland other materials (FMEA)for all materials
• Section 4.5
Activi ty 3: Assess feasibility ofcorrosion allowance andcorrosion control
• SP-2041
• DEP Specification 30.10.02.14-Gen
• DEP Specification 30.10.02.31-Gen
• If the operating conditions are beyond currently qualified corrosion
inhibitors, the likelihood of successfully qualifying an inhibitor may beassessed using the NACE paper by A Crossland, et al.
Activi ty 4: Assess CRA andnon metallic options and rerunthreats and barriers
• Section 4.5 of this standard
• SP-2041
• DEP Specification 39.01.10.12-Gen (as amended by this document)DEP Specification 30.10.02.15-Gen
Activi ty 5: Identify gaps andopportunities for qualificationtesting
• Project Schedule – Level 2 (DCAF 186)
Activi ty 6: Make materialschoices and develop corrosionmanagement framework
• Concept Selection Report (DCAF 99)
• Equipment specifications (PDO and DEP)
• Facility Status Reports/Current Status Reports (for brownfield projects – see CP 114)
• DEP 31.38.01.84-Gen
• DEP 30.10.02.11-Gen
DEFINE Phase
Activi ty 1 to 6
• Basic design package (DCAF 235)
• Chemical requirements Report (DCAF 250)
• Operations and maintenance philosophy (DECAF 363)
• Process flow scheme (PFS) (DCAF 242)
• Process engineering flow scheme (DCAF 243)
• Utilities flow scheme (UFS) (DCAF 1390)
• Utilities engineering flow scheme (DCAF 1391)
• Equipment listing (DCAF 1497)
• Pipelines flow and flow assurance design and operability report.(DCAF 248)
• Operations and maintenance philosophy (DCAF 363)
• Rotating equipment type selection report (DCAF 273)
• Pipeline design report (DCAF 315)
• Reliability, availability and maintainability report (DCAF 332)
• Performance standards & assurance tasks for safety criticalelements/equipment (DCAF 384)
• Maintenance and integrity strategy (DCAF 409)
EXECUTE Phase
Activi ty 6• Operations and maintenance philosophy (DCAF 49)
• Chemical requirement reports (updated) DCAF 1224)
• Heat and materials balance report final (DCAF 420)
• Pipelines flow and flow assurance report final (DCAF 679)
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• Process flow scheme (DCAF 1213)
• Process engineering flow schemes (PEFS & P&IDs), (DCAF 1214)
• Utility flow schemes (UFS) (DCAF 1435)
• Utilities engineering flow schemes (UEFS/P&IDs), (DCAF 1449)
• Equipment listing (DCAF 1498)
• Vibration assessment report (DCAF 487)
• Detailed HAZOP report (DCAF 449)
• Asset Reference plan (DCAF 438)
• Reliability, availability and maintainability report (DCAF 486)
• Process control (DCAF 46)
• Process control narrative (DCAF 683)
• Line List
OPERATE Phase
Assurance • Assurance process (design conditions vs actual and futureoperating conditions. Including IOW
• Assessed corrosion rate
4.2 Deliverables of materials selection in various project phases
The following MCI deliverables and requirements shall be implemented for any project regardless ofthe scope and value. These are as per PDO version of DCAF.
Table 1: Mandatory deliverables and requirements for Select phase from Materials Corrosion andInspection discipline
ORPPhase
ID Name Accountable
DisciplineDescription
Select 47Erosion ManagementPhilosophy (DG3a)
MaterialsCorrosion andInspection
• SP-2161
• DEP 39.01.10.11-Gen
• DEP 39.01.10.12-Gen (MC CFDH)
• Materials and Corrosion Engineer specifiesthe acceptable velocity ranges for materialsof construction with respect to corrosion. TheErosive velocity calculation is done by theprocess engineers.
• At this stage the overall philosophy should bedefined together with the integrity impact andneed to interface with other disciplines. Thedetailed materials selection and details ofinspection techniques will be covered later inthe Preliminary Corrosion and ErosionManagement Manual in the define phase(ID300).
• Provide input on the materials limitation withrespect to erosion velocity. And input intoPreliminary Corrosion and ErosionManagement Manual in the define phase(ID300).
Select 60CorrosionManagementPhilosophy (DG3a)
MaterialsCorrosion andInspection
• CP 208 - Corrosion Management Code ofPractice
• Mandatory for all projects.
• Recommendation made in CorrosionManagement Strategy shall be embedded inthe Corrosion Management Philosophyincluding inspection requirements.
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Select 210
Initial Materials Selection Report (including Corrosion ManagementStrategy) (DG3a)
MaterialsCorrosion andInspection
• SP-2161
• DEP 39.01.10.11-Gen
• DEP 39.01.10.12-Gen (MC CFDH)
• DEP 30.10.02.14-Gen
• CP 208 - Corrosion Management Code ofPractice
• Mandatory for all projects.
• The corrosion management strategyincluding initial failure mode effect analysisand the preliminary (high level) materialsselection reports are based on are basedinformation provided by the project that shallinclude the required minimuminformation/deliverables as per DCAF for thisphase of the project (e.g. H&MB, etc.).Thisshould normally consist of referring to theapplicable standards and mention anyimportant choices that are made, e.g. carbonsteel + corrosion inhibition versus corrosionresistant alloy. This also includes the
deliverable of materials threats analysis andthe erosion management philosophy.
• Materials selection reports shall be preparedby function (UEOC) for any project. Thereport shall be peer reviewed and signed offby at least two Materials and CorrosionEngineer TA2s from the Function other thanthe author of the report.
• External peer review shall be completed forprojects above 1 bln
Table 2: Mandatory deliverables and requirements during the Define phase for Materials Corrosionand Inspection discipline
ORPPhase
ID Name AccountableDiscipline
Description
Define 64MCI Failure Modesand Effects AnalysisReport
MaterialsCorrosion andInspection
• SP-2161
• DEP 39.01.10.11-Gen
• DEP 39.01.10.12-Gen (MC CFDH)
• Mandatory for all projects to be made part ofthe materials selection report. The reportshall be endorsed and approved by Materialsand Corrosion Engineer TA2 from Function.
• This is an FMEA of the corrosion controlsystems; for each mode of operation andcorrosion risks, analysis looks at the barriersand monitoring that need to be in place.
Define 297Materials SelectionReport - updated
MaterialsCorrosion andInspection
• SP-2161• DEP 39.01.10.11-Gen
• DEP 39.01.10.12-Gen (MC CFDH)
• Mandatory for all projects
• Based on the preliminary report (ID 210), thisreport shall include detailed assessment toensure the agreed materials selection for allaspects of the projects is properlydocumented independently from the Selectphase report based on the updated designbasis.
• The updated Materials selection shall be peerreviewed by PDO Materials and CorrosionEngineer TA2 other than the author of the
report and Materials and Corrosion EngineerTA2 from Function. The final endorsementand approval shall be by Materials andCorrosion Engineer TA2 from Function.
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• For projects more than 100 mln USD or fornew field development including EOR/severesour environments, the Materials selectionreports shall be endorsed and approved byMaterials and Corrosion Engineer TA1.
• For projects 1 billion and above, materials
selection shall be endorsed by DRB1.• This is one of Materials, Corrosion &
Inspection key deliverables which requiresinteraction with many disciplines.Presentations to key disciplines arerecommended to ensure everyone is awareof the choices and implications. Theconsequence of materials selection must beunderstood / agreed by the Operator.Philosophy should be presented toOperations representative and if necessary tothe Operator’s Management to ensure allconsequences are understood / agreed. Thecontrol also includes deliverable of pipeline
preservation / transportation / storage andetc.
• Long lead items finalized at FEED stage shallbe endorsed and approved by Materials andCorrosion Engineer TA2 from Function.
• Materials selection report shall be alignedand verified with the HAZOP, and ALARP.MCI TA shall participate in HAZOP and ALARP assessment.
Define 298Corrosion Inhibition System Design & Test Proposal
MaterialsCorrosion andInspection
• DEP 30.10.02.14-Gen
• DEP 31.01.10.10-Gen
• PR 1103 - Chemical Injection
•
Mandatory for all projects where applicable• Materials selection report identifies the
requirement of corrosion inhibitor. Unless acorrosion inhibitor (CI) application duplicatesan existing application, tests are required toqualify the CI. Corrosion inhibition testingprotocol and the test results shall beevaluated by Materials and Corrosion TA2.
• This document defines the use of availabilityrequirements for corrosion inhibitors, testprogram and an update of ID 301 thePreliminary Chemical Compatibilities Matrix.
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Define 300
CorrosionManagementFramework -Preliminary
MaterialsCorrosion andInspection
• Mandatory for all projects.
• Corrosion Management Framework (CMF)covers corrosion risks, means of mitigation,monitoring and demonstrating integrity. Thereis synergy with the CMF, Safety CriticalElements / Technical Integrity Framework
and RBI. Incorporates data from PerformanceStandards for Safety Critical Elements (ID384), the Materials Selection report (ID 297)and the CI System Design (ID 298). Itincludes deliverables of critical flow velocityreport, erosion mgt manual, integrity mgtphilosophy, CP designs and for sour systemssulphur depositions evaluation, oxygeningress into the pipeline, potential corrosionimplications such as:-
a) Execute Failure Mode and Effects Analysis
b) Produce preliminary CorrosionManagement Framework
c) Pipeline Integrity ManagementPhilosophy
d) Include erosion and sand handlinge) Corrosion and inspection integrity
management philosophyf) Inspection strategy shall be
included.
• This report shall be reviewed by PDOMaterials and Corrosion Engineer TA2 otherthan the author of the report and Materialsand Corrosion Engineer TA2 from Function.The final endorsement and approval shall beby Materials and Corrosion Engineer TA2from Function.
Define 302Welding & WeldInspectionSpecifications
MaterialsCorrosion andInspection
• Shall refer to PDO welding and NDTspecifications
• Generate welding and weld inspectionspecifications (or instruct contractor to dosuch).
• For CRAs materials grades not listed in SP-1173, the specifications shall be developedand approved by Materials and CorrosionEngineer TA2 from Function.
Table 3: Mandatory Deliverables and requirements during the Execute phase for Materials corrosionand inspection discipline
ORPPhase
ID Name Accountable
Discipline Description
Execute LocalRule
UpdatedMaterialsSelection Report
MaterialsCorrosion andInspection
• Mandatory for all projects.
• Materials selection peer review sessions shallbe organized by the Materials and CorrosionEngineers from the projects or the author ofthe report and ensuring participation fromProcess, Mechanical, Rotating and Pipelineengineering. This report shall be approved byMaterials and Corrosion Engineer TA2 fromFunction.
• For projects more than 100 mln USA or fornew field development including EOR/severesour environments, the Materials selectionreports shall be endorsed by TA1.
• A final Materials selection report shall begenerated during Execute phase to ensurethe outcome of the FEED and DDassessment is included in the final
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deliverable. This report shall be approved asindicated in Section 8.
• This report should be completed and peerreviewed before material is procured.
• Long lead items finalized at FEED stage shallbe endorsed and approved by Materials and
Corrosion Engineer TA2 from Function.
Execute 51
Set-up andOptimisation ofCorrosionControl System
MaterialsCorrosion andInspection
• Mandatory for all projects.
• Prove that all corrosion control equipment isworking and operators understand theprocedures; demonstrate that corrosion isunder control. This first requires the corrosionand erosion monitoring systems to be testedand accepted.
• To be signed off by Corrosion Control TA2from Function.
Execute 77
CorrosionInspectionManagementSystem Selectionand Population
MaterialsCorrosion andInspection
• Mandatory for all projects.
• There are many different CIMS used in theShell Group, e.g. Pacer, IMSA, etc (seetoolbox). The correct system has to be
selected for the operating region, the systemhas to be set up and populated withequipment and a baseline generated.Communicate with business unit to determinewho has ultimate responsibility and what therequirements and expectations are.
• To be signed off by Materials Corrosion &Inspection TA2 from Function.
Execute 79CorrosionInhibitorSelection Report
MaterialsCorrosion andInspection
• Mandatory for all projects and newequipment.
• Developed from the philosophy document(ID60), and the Corrosion ManagementFramework (1194) and linked to PerformanceStandard for Safety Critical Elements (ID
452).• To be signed off by Corrosion Control TA2
from Function.
Execute 82
Approval byFunction -Inspectors &Jointers for Nonmetallic forcontractor staff
MaterialsCorrosion andInspection
• Mandatory for all projects if the material isapplicable for the project.
Execute 87
Approval byfunction:-Calculation of PELiner thickness
MaterialsCorrosion andInspection
• Mandatory for all projects if the material isapplicable for the project.
Execute 88
Approval byfunction:- use ofexternal MCIconsultancies,test laboratoriesand testrequirements
MaterialsCorrosion andInspection
• Mandatory for all projects if the material isapplicable for the project.
Execute 168
Approval byFunction -operators forspecialized NDTprocesses
MaterialsCorrosion andInspection
• Mandatory for all projects if the material isapplicable for the project.
Execute 170
Approval byFunction -
ContractorsweldingEngineers & NDTlevel III
MaterialsCorrosion andInspection
• Mandatory for all projects if the material isapplicable for the project.
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Execute 171
Approval byFunction:- GRE1000 hrs testpressure,material and typeof joints type
MaterialsCorrosion andInspection
• Mandatory for all projects if the material isapplicable for the project.
Execute 173
Approval byfunction:- Newcoatingapplicators orcoating products
MaterialsCorrosion andInspection
• Mandatory for all projects if the material isapplicable for the project.
Execute 174
Approval byfunction:- Newcoating testingprogram
MaterialsCorrosion andInspection
• Mandatory for all projects if the material isapplicable for the project.
Execute 175 Approval byfunction:- Newshrink sleeves
MaterialsCorrosion andInspection
• Mandatory for all projects if the material isapplicable for the project.
Execute 176
All specializedmaterial and
weld qualificationtesting
MaterialsCorrosion andInspection
• Mandatory for all projects if the material is
applicable for the project.
Execute 177
Approval byfunction:- CPdesign for buriedpipelines, tanksand submarineloading liners
MaterialsCorrosion andInspection
• Mandatory for all projects if the material isapplicable for the project.
Execute 178
Approval byfunction:- Approval of Wellcasing corrosionprotectionstrategy
MaterialsCorrosion andInspection
• Mandatory for all projects if the material isapplicable for the project.
Execute 182
Review andapproval of thecorrosionmonitoring plansfor corrosioninhibitors, CP,DCVG, CIPS
MaterialsCorrosion andInspection
• Mandatory for all projects if the material isapplicable for the project.
Execute 183
Approval ofpipeline andequipmentintegrity reportincluding RBAand RBI reports
MaterialsCorrosion andInspection
• Mandatory for all projects if the material isapplicable for the project.
Execute 217 Approve Assessedcorrosion rate
MaterialsCorrosion andInspection
• Mandatory for all projects if the material is
applicable for the project.
Execute 484
Field Inspection Plan / RBI Plan /BaselineInspection / CIMS (for Operate)
MaterialsCorrosion andInspection
• Mandatory for all projects.
• Developed from the Corrosion ManagementFramework (ID300, Define Phase andID1194, Execute Phase) and linked toPerformance Standard for Safety CriticalElements (ID 452 - Execute Phase. Thisincludes the selection and population ofCIMS (Corrosion Inspection ManagementSystem and the Field Inspection Plan / RBIPlan.
• Inspection plan shall be included.
• To be signed off by Material Corrosion &Inspection TA2 from Function.
http://sww.wiki.shell.com/wiki/index.php/Field_Inspection_Plan/RBI_plan/Baseline_Inspection/CIMS_for_Operate_%28DCAF_ID_484%29http://sww.wiki.shell.com/wiki/index.php/Field_Inspection_Plan/RBI_plan/Baseline_Inspection/CIMS_for_Operate_%28DCAF_ID_484%29http://sww.wiki.shell.com/wiki/index.php/Field_Inspection_Plan/RBI_plan/Baseline_Inspection/CIMS_for_Operate_%28DCAF_ID_484%29http://sww.wiki.shell.com/wiki/index.php/Field_Inspection_Plan/RBI_plan/Baseline_Inspection/CIMS_for_Operate_%28DCAF_ID_484%29http://sww.wiki.shell.com/wiki/index.php/Field_Inspection_Plan/RBI_plan/Baseline_Inspection/CIMS_for_Operate_%28DCAF_ID_484%29http://sww.wiki.shell.com/wiki/index.php/Field_Inspection_Plan/RBI_plan/Baseline_Inspection/CIMS_for_Operate_%28DCAF_ID_484%29http://sww.wiki.shell.com/wiki/index.php/Field_Inspection_Plan/RBI_plan/Baseline_Inspection/CIMS_for_Operate_%28DCAF_ID_484%29http://sww.wiki.shell.com/wiki/index.php/Field_Inspection_Plan/RBI_plan/Baseline_Inspection/CIMS_for_Operate_%28DCAF_ID_484%29http://sww.wiki.shell.com/wiki/index.php/Field_Inspection_Plan/RBI_plan/Baseline_Inspection/CIMS_for_Operate_%28DCAF_ID_484%29http://sww.wiki.shell.com/wiki/index.php/Field_Inspection_Plan/RBI_plan/Baseline_Inspection/CIMS_for_Operate_%28DCAF_ID_484%29http://sww.wiki.shell.com/wiki/index.php/Field_Inspection_Plan/RBI_plan/Baseline_Inspection/CIMS_for_Operate_%28DCAF_ID_484%29http://sww.wiki.shell.com/wiki/index.php/Field_Inspection_Plan/RBI_plan/Baseline_Inspection/CIMS_for_Operate_%28DCAF_ID_484%29
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Execute 488
Welding,Fabrication and InspectionProcedures
MaterialsCorrosion andInspection
• PQR, WPS, NDT procedures, heat treatmentprocedures shall be authorised at projectlevels except for below mentioned areas. Tobe signed off by Welding and NDT.TA-2.
• PQR, WPS, heat treatment procedures
involving for CRAs (25% Cr and above), lowtemperature applications, >X65 steels (withinthe standards) shall be approved by thematerial and corrosion function (UEOC). Tobe signed off by Specialized Welding & NDTTA-2.
• Advanced NDT technique procedures suchas AUT, Phased Arrays, TOFD, andradioscopy. To approved and signed off bySpecialized Welding & NDT TA-2.
• Non-metallic, bonding procedures, PE linedfusion bonding procedures shall be approvedby and signed Materials and Corrosion TA2in Non-metallic from Function.
Execute 1194CorrosionManagementFramework
MaterialsCorrosion andInspection
• Mandatory for all projects.• Update of the preliminary document,
developed in the Select phase (ID 300) andPerformance Standards for Safety CriticalElements (ID 384).
ExecuteFinal Materialselection Report
MaterialsCorrosion andInspection
• Mandatory for all projects.
• Update of the preliminary document.
• To be approved by Materials and CorrosionTA2 from function.
Table 4: Mandatory Deliverables and requirements during the operate phase for Materials corrosionand inspection discipline
ORPPhase
ID Name AccountableDiscipline
Description
Operate 25Risk BasedInspection
MaterialsCorrosion and
Inspection
• Mandatory for all operations.
• Risk Based Inspection (RBI) covers theverification of the integrity of the assets. Itincludes analysis (using S-RBI see toolbox),inspection planning and work packdevelopment for internal and externalcorrosion, non-intrusive inspection (NII)analysis, inspection execution, storing thedata in CIMS (see toolbox), inspection dataanalysis, fitness for purpose assessment,
external corrosion analysis and modelling(using ECM/EXCOR see toolbox), corrosionmodelling. Local legislation requirements forinspection (review and reporting), reporting toasset custodian and feedback of data into theCMF (ID NEW above).
• RBI shall be approved by Materials Corrosionand Inspection TA2 from Function.
http://sww.wiki.shell.com/wiki/index.php/Welding%2C_Fabrication_%26_Inspection_Procedures_%28DCAF_ID_488%29http://sww.wiki.shell.com/wiki/index.php/Welding%2C_Fabrication_%26_Inspection_Procedures_%28DCAF_ID_488%29http://sww.wiki.shell.com/wiki/index.php/Welding%2C_Fabrication_%26_Inspection_Procedures_%28DCAF_ID_488%29http://sww.wiki.shell.com/wiki/index.php/Welding%2C_Fabrication_%26_Inspection_Procedures_%28DCAF_ID_488%29http://sww.wiki.shell.com/wiki/index.php/Corrosion_Management_Framework_-_preliminary_%28DCAF_ID_300%2C_1194_%26_1197%29http://sww.wiki.shell.com/wiki/index.php/Corrosion_Management_Framework_-_preliminary_%28DCAF_ID_300%2C_1194_%26_1197%29http://sww.wiki.shell.com/wiki/index.php/Corrosion_Management_Framework_-_preliminary_%28DCAF_ID_300%2C_1194_%26_1197%29http://sww.wiki.shell.com/wiki/index.php/Corrosion_Management_Framework_-_preliminary_%28DCAF_ID_300%2C_1194_%26_1197%29http://sww.wiki.shell.com/wiki/index.php/Corrosion_Management_Framework_-_preliminary_%28DCAF_ID_300%2C_1194_%26_1197%29http://sww.wiki.shell.com/wiki/index.php/Corrosion_Management_Framework_-_preliminary_%28DCAF_ID_300%2C_1194_%26_1197%29http://sww.wiki.shell.com/wiki/index.php/Welding%2C_Fabrication_%26_Inspection_Procedures_%28DCAF_ID_488%29http://sww.wiki.shell.com/wiki/index.php/Welding%2C_Fabrication_%26_Inspection_Procedures_%28DCAF_ID_488%29http://sww.wiki.shell.com/wiki/index.php/Welding%2C_Fabrication_%26_Inspection_Procedures_%28DCAF_ID_488%29http://sww.wiki.shell.com/wiki/index.php/Welding%2C_Fabrication_%26_Inspection_Procedures_%28DCAF_ID_488%29
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4.3 Factors affecting Materials selection
4.3.1 Information required and review of factors affecting materials selection
Shall be as per DEP.39.01.10.11-Gen, Section 2.3.3 with the following amendments:-
a) Section 2.3.3.2. Replace Table 1 with the Table A.1 in Appendix A of this document.b) Remove reference to EFC 17 as worst case for chloride when not other information is
available.c) Add the following:
Chlorides carry over evaluation:
For gas production environments (produced gas or without produced water) and downstreamof separator. Salt accumulation scenarios shall be evaluated as part of materials selectionprocess.. Presence of formation water shall be included in the evaluation. Assumptions of
lower Chloride levels can only be determined with a proper salt materials balance studiesapproved by the respective technical discipline authority (process) and supported byoperation and maintenance philosophy.
d) Section 2.3.3.4 and Appendix E Table E.1 for low temperature requirements shall bereplaced by DEP.30.10.02.31-Gen.
4.4 Appl ication of carbon steels
Shall be as per DEP 39.01.10.11-Gen, Section 2.4. and DEP 30.10.02.14-Gen
4.5 Degradation mechanisms
A standardised checklist of corrosion threats is compiled by reference to DEP 39.01.10.11, API RP571 and the Energy Institute (EI) Guidance for Corrosion Management. Materials and CorrosionEngineer shall be consulted to ensure all the degradation mechanisms are evaluated including all thenormal and upset operating scenarios.
The following table contain the possible damage mechanisms that shall be evaluated duringmaterials selection process and the mandatory requirements associated to each damagemechanism.
DamageMechanism
Description
CO2 Corrosion
CO2 corrosion is one of the most common forms corrosion resulting in wallthickness loss in carbon steel oil / gas preproduction systems. CO2 corrosion iscaused by electrochemical reactions between the steel and carbonic acid.
The Hydrocor model has been developed for predicting the likely ‘worst case’corrosion rate of carbon steel. Hydrocor is a model for quantifying thecorrosivity of the operating environments associated with the production andtransportation of water-wet hydrocarbons in carbon steel facilities. Thepredicted corrosion rate is used to identify Service Life Cycle (SLC) and todetermine the appropriate corrosion allowance for a carbon steel system or
whether Corrosion Resistant Alloy (CRA), non-metallic materials or othercorrosion mitigation method is required. The HYDROCOR model (Appendix F)or an alternative model approved by TA1 shall be used for corrosion modellingin systems containing CO2. The aim of calculating the CO2 corrosion rate is to
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establish the SLC and thereby decide what corrosion allowance might beneeded or whether a CRA is required.
Welds and their surrounding heat-affected zones may have lower resistance toCO2 corrosion than the parent metal. This phenomenon is known as
Preferential Weld Corrosion (PWC). This may arise for a number of reasons,partly geometrical, partly chemical and partly metallurgical. Corrosion control bymeans of inhibition has been shown to prevent PWC, provided that a suitablecorrosion inhibitor is selected and injected to provide a sufficiently highconcentration. See also DEP.39.01.10.11 (Appendix B). It should be assumed,for sweet production systems, that the corrosion rate of the weld and heataffected zone is three times that of the surrounding parent steel.
For more details information, refer to:
• DEP 39.01.10.11-Gen Informative, Section 2.4.3
• EI Guidance, Annex B1
• API RP 571, Section 4.3.6
• NORSOK M-601
H2S Corrosion
Compared to CO2 corrosion of steel, H2S may not cause severe metal weightloss corrosion because the corrosion product, iron sulfide (FeS) usually forms aprotective film on the steel surface. However, whenever the film is imperfect ordamaged, a corrosion cell is set up between FeS covered surface and the baremetal, resulting in very localised, accelerated corrosion (e.g., pitting corrosion).Therefore, the corrosion failure mode in sour systems is pinhole leaks, whichare extremely dangerous, considering the health risks associated with H2S.
For carbon steel, the Hydrocor model can be used for corrosion rate predictionin H2S containing systems. The empirical correlation included in Hydrocor forsour conditions is only verified up to 50
oC and 15 bar ppH2S. Above these
values/levels, the corrosion prediction is not considered reliable. Sour corrosionmodelling typically gives over prediction as Hydrocor model provides a worst
case pitting scenario, depending on factors like whether sulphur is present ornot. Testing shall be carried out to optimise the corrosion assessment withlaboratory testing and reviewing operating field analogues.
For more details information, refer to:-
• DEP 39.01.10.11-Gen Informative, Section 2.4.4.2
• API RP 571, Section 5.1.1.10
Elementalsulphur
The presence of elemental sulphur increases the corrosivity of the environmentfor pitting corrosion, stress corrosion cracking and particularly weight losscorrosion thus assessment for elemental sulphur deposition shall be carried outfor high H2S content reservoir (>2Mol%). The presence of chloride ions greatlyenhances sulphur corrosion.
Where elemental sulphur is likely to form in carbon steel systems, sulphursolvents shall be used to prevent the sulphur depositing. Hydrocarbon liquidsare generally good sulphur solvents. The volume of liquid hydrocarbon presentand its capacity to dissolve sulphur should be assessed to determine whetherany additional sulphur solvent is required. In sour systems that contain oxygen,sulphur can form in situ. All potential sources of oxygen in sour systems shouldbe reviewed and where required eliminated or minimized.
CRA materials are not immune to elemental sulphur (pitting/cracking). Theapplication limits in SP/DEP/ISO 15156 for CRA do not include any presence ofElemental sulphur.
Top-of-LineCorrosion Top of line corrosion is due to condensation rateDEP 39.01.10.11-Gen Specification, Table 2
Amine Corrosion • API RP 571, 5.1.1.1,
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• EFC 46
Erosion-Corrosion
• DEP 39.01.10.11-Gen Informative, Appendix D;
• EI Guidance, Annex B12;
• API RP 571, 4.2.14
OxygenCorrosion
In aqueous corrosion, oxygen is a more corrosive gas than CO 2 and H2S. For
bare carbon steel system, pitting corrosion will occur when exposed toseawater even with only traces amount of oxygen, but the rate of corrosion isproportional to the mass transfer rate of dissolved oxygen to steel surface. Ifoxygen is continually maintained at < 10ppb, a bare carbon steel or lower gradeCRA should be acceptable with minimum expected corrosion downstream ofthe oxygen removal point. However, during upset conditions, which areunavoidable in almost all cases, the dissolved oxygen concentration can reachfully aerated levels. For carbon steel systems the corrosion rate is proportionalto the rate at which oxygen reached the steel. For hydrocarbon productionsystems oxygen is deemed an operationally avoidable corrodent. Where it mayhave an impact is in utility water systems for example. Aqueous oxygencorrosion rates can be predicted with HYDROCOR.
CRA oxygen corrosion is a form of galvanic attack where the normal protectivepassive surface oxide film fails at one small point and becomes a small anodeto the surrounding intact surface, resulting in very rapid localised pitting attack.Oxygen pitting attack on a CRA is often more rapid than on CS, withpenetration rates as much as 6 times higher.
Materials selection for hydrocarbon application does not consider presence ofoxygen in the system. The facilities shall be designed to avoid any potentialingress of oxygen.
The application limits of CRAs defined in company standards are based onoxygen free conditions.
CreviceCorrosion
Crevice corrosion tends to occur within a tight gap, or underneath deposits (see
also UDC) where an occluded environment can develop, e.g. a tube to tubesheet joint. It can also be considered under flange face corrosion as describedin EI Guidance, Annex B8.Likelihood of crevice corrosion shall be minimized by materials selection anddesign considerations.
Pitting Corrosion
Considered separately to pitting caused by other corrosion threats, in thiscontext it is applied to CRAs with passive films in production and utilityenvironments. In production environments the key parameters are temperatureand chloride content, whilst in utility environments it will generally be oxygen(oxidiser) content, flow rate, temperature and chloride content.Likelihood of pitting shall be minimized by materials selection and designconsiderations.
Under DepositCorrosion
(UCD)/dead leg
The deposition of solids creates a shielded environment that providesconditions for other degradation mechanisms, such as MIC, to occur. Solids instraight piping runs are considered to settle out when film velocities are lessthan 1 ms
-1. Loosely adherent scale can also creates a shielded environment in
the same way as settled deposits. Dead leg corrosion, detailed in EI Guidance, Annex B4, Shall be assessedduring all phases of the project.
GalvanicCorrosion
Galvanic corrosion occurs when two dissimilar alloys are coupled in thepresence of a corrosive aqueous solution. The more active materials will be theanode and will be preferentially corroded, while the other, more noble materialswill be the cathode and is protected from corrosion. A large ratio of cathode toanode surface area must be avoided because the galvanic attack isconcentrated in the small areas of the anode.
For more details information, refer to
• EI Guidance, Annex B5
• API RP 571, Section 4.3.1
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MicrobialInduced
Corrosion (MIC)
Microbiologically Induced Corrosion (MIC) is a corrosion resulting from thepresence of active biological microorganisms from contaminated well operatingfluids, a contaminated reservoir, contamination during construction, surfacecommissioning fluids, seawater injection, the design or practice of disposing
surface water in oilfiled pipelines, open drain systems, etc. Microorganismstend to attach themselves to solid surfaces, colonise, proliferate and formbiofilms, which can create a corrosive environment at the biofilm / metalinterface radically different from the bulk medium in terms of pH, salts anddissolved gas. As a consequence, either a galvanic corrosion cell and / oracidic action may develop causing metal attack. Instead of causing generalcorrosion, MIC is a localised attack and may take the forms of pitting corrosion,crevice corrosion, under deposit corrosion, selective dealloying and galvaniccorrosion.
Once bacteria are present in the system it is almost impossible to eliminatethem. Bacterial surveillance program shall be performed during fieldcommissioning and after any significant new activity. Methods to mitigate
bacteria presence is chemical treatment (commonly with biocide), operationalpigging and robust surveillance program in place. The likelihood of MIC canalso be assessed using HYDROCOR.
For more details information, refer to:-
• EI Guidance, Annex B4 API RP 571, Section 4.3.8
Preferential Weld
Corrosion
Welds and their surrounding heat-affected zones may have lower resistance toCO2 corrosion than the parent metal. This phenomenon is known asPreferential Weld Corrosion (PWC). This may arise for a number of reasons,partly geometrical, partly chemical and partly metallurgical. Corrosion control bymeans of inhibition has been shown to prevent PWC, provided that a suitablecorrosion inhibitor is selected and injected to provide a sufficiently high
concentration.
For more details information, refer to:-
• DEP 39.01.10.11-Gen Informative, Appendix B
• EI Guidance, Annex B6
IntergranularCorrosion
Principally occurring in austenitic stainless steels it is characterised by attackalong grain boundaries where precipitation of chromium carbides, nitrides orintermetallics has reduced the corrosion resistance of adjacent materials. Thiseffect is known as ‘sensitisation.’
Strong Acid (WellWorkover)Corrosion
See DEP 39.01.10.11-Gen Specification, 3.3 for mandatory requirements. Poststimulation mitigation and management approach are given in RMP31.40.00.50 (for sour service).
Internal Cracking
Sulphide StressCracking
SP-2041; DEP 39.01.10.11-Gen Specification, 2.4.4.3; EI Guidance, Annex B2; API RP 571, 5.1.2.3, ISO 15156.
SSC is a rapid form of cracking that can cause catastrophic failure. Control ofthis form of cracking SHALL [PS] be through selection of materials notsusceptible to cracking under all expected modes of operation (including startup and shutdown). Materials selection shall be carried out using DEP30.10.02.15 AND SECTION 5 of this SP.
Many of the requirements of DEP 30.10.02.15-Gen. are related to hardness
restrictions, and it uses both Rockwell C (for non-welded materials) and Vickers10 kg (22 lb) (for welded materials). Approximate hardness conversion tablesare given in ASTM A370. Note that the conversion factors do not apply to alltypes of materials. For hardness conversions of martensitic and
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austenitic/ferritic materials the Principal shall be consulted.
Hydrogen
Induced Cracking
SP-2041; DEP 39.01.10.11-Gen Informative, 2.4.4.4; EI Guidance, Annex B2; API RP 571, 5.1.2.3 Where no HIC testing for certain product forms is requiredby Table 4 the need for such testing should be evaluated based on the criticalityof the components in question.
HIC requirements SHALL be as per SP-2041. SP-2041 replaces HICrequirements in section 2.4.4.4 of DEP.39.01.10.11. The test method has beenshown to be very sensitive to small variations; therefore a control sample ofknown HIC sensitivity shall be included in HIC tests to make sure that theresults are calibrated against a standard.
Stress OrientedHydrogen
Induced CrackingEI Guidance, Annex B2; API RP 571, 5.1.2.3
Amine StressCorrosionCracking
API RP 571, 5.1.2.2; EFC 46
Hydrogen
Embrittlement
DEP 39.01.10.11-Gen Specification, 2.4.4.6; API RP 571, 4.5.6
Chloride StressCorrosionCracking EI Guidance, Annex B11; API RP 571, 4.5.1
Liquid MetalEmbrittlement
API RP 571, 4.5.5
CorrosionFatigue
API RP 571, 4.5.2
External co rrosion
Atmospher icCorrosion
EI Guidance, Annex B9; API RP 571, 4.3.2
Corrosion UnderInsulation
EI Guidance, Annex B10; API RP 571, 4.3.3
Crevice andPitting Corrosion
EI Guidance, Annexes B9 and B11
GalvanicCorrosion
EI Guidance, Annex B5; API RP 571, 4.3.1
High temperatureoxidation
API RP 571, 4.4.1
Sulphidation API RP 571, 4.4.2 Applicable to such items as flare tips operating with H2S
Soil Corrosion API RP 571, 4.3.9. Including MIC corrosion.
External Cracking
Chloride StressCorrosionCracking
EI Guidance, Annex B11; API RP 571, 4.5.1
HydrogenEmbrittlement
DEP Specification 39.01.10.11-Gen, 2.4.4.6; API RP 571, 4.5.
Liquid MetalEmbrittlement
API RP 571, 4.5.5
CorrosionFatigue
API RP 571, 4.5.2
Mechanical Degradation
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Erosion by Solidsand Liquids
DEP Informative 39.01.10.11-Gen, D.2.1, D.2.2; EI Guidance, Annex B12; APIRP 571, 4.2.14
External
Abras ion & Wear
DEP Specification 31.38.01.29-Gen
Issues that may fall under this categorisation are: piping clashes, fretting andwear at pipe supports.
Fatigue Cracking API RP 571, 4.2.16 and 4.2.17; Energy Institute Process Pipework FatigueGuidelinesHigh Temperature Creep and Stress Rupture
HighTemperature
Creep and StressRupture
API RP 571, 4.2.8
Thermal Fatigue API RP 571, 4.2.9Low Temperature
Embrittlement
DEP Specification 30.10.02.31-Gen; API RP 571, 4.2.7
Long RunningDuctile Fracture
DEP 31.40.00.10-Gen Specification, 8.1.6 Applicable to gas and multiphase pipelines where fluid decompressioncharacteristics can drive initiated cracks for substantial distances
Galling Galling is a form of adhesive wear and occurs by dynamic metal-to-metalcontact between two surfaces sliding relative to one another when there is poor,or non-existent, lubrication. It can occur at flange/gasket interfaces and lead topoor sealing.
Non-Metallic SealDegradation
DEP 39.01.10.12-Gen Specification, Appendix CRapid gas decompression is a major cause of elastomeric seal failure in highpressure gas service. Seals can also fail by ageing where the serviceenvironment induces chemical or physical changes. Supporting information forstudy is given in UK HSE Research Reports 320 and 485.
Refer to DEP30.10.02.13 for non metallic testing requirements.
4.6 Economic aspects of materials selection
Shall be as per section 2.5, DEP 39.01.10.11 –Gen.
4.7 Non- operational considerations
Materials selection shall consider all the operating modes including non operational considerations asper section 3 of DEP 39.01.10.11-Gen.
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5 GENERAL MATERIALS DESCRIPTION AND SPECIFIC REQUIREMENTS
5.1 General Requirements for Specific Materials Group
5.1.1 Sour serviceIf hydrogen sulfide concentration (H2S) is present in the equipment over the lifecycle in any phasethe service shall be considered as sour service and the requirements of SP-2041 andDEP.30.10.02.15 shall applied. Concentration of H2S shall be determined in accordance with DEP25.80.10.18-Gen.
When assessing materials suitability, the pH and H2S partial pressure shall represent not only normallife cycle exposures but also exposures as can reasonably be expected to occur during an upset or ina stratified flow condition (e.g., normal packer fluid pH versus condensing water pH after tubing toannulus leak, or pH of flowline fluid versus condensing water pH during stratified flow.
For vessels, internal protective coatings are acceptable to protect carbon and low alloy steels againstHydrogen Induced Cracking (HIC) or stepwise cracking, provided that the coating integrity is ensuredby means of a suitable coating maintenance program and that a program to detect and monitor HICformation and growth is in place. (Informative: For practical purposes, this shall only apply tovessels).
Stainless steels
The production stream phase behaviour SHALL [PS] be reviewed to identify if flashing conditions orsalt deposition from carryover fluids are present, which conditions concentrate fluid salinity. In theevent flashing conditions are present, either a salinity of 250 g/l (expressed as NaCl) or the greatervalue equivalent to salt saturation in water at operating conditions shall be assumed when selectingand testing the materials. Any testing shall be done in representative water chemistry.
The temperatures given in Table 5.1 shall be used to assess the risk of pitting corrosion, crevicecorrosion and chloride stress corrosion cracking of the most common stainless steel type used inUpstream in offshore and onshore salt laden environments (e.g. desert environment). The risk forother stainless steel types shall be referred to the MCI TA2 from Function.
Table 5.1: Typical stainless steel temperature limits.
Stainless
steel type(1)
Threshold
for pitting
corrosion
Threshold
for crevice
corrosion
Negligible
risk of
CSCC
Significant
risk of
CSCC316L(2) 5oC 35
(4) Assumes PREN > 40
Contact of zinc with stainless steel items SHALL[PS] be prevented, including zinc coatingcontamination and contamination by zinc in fire scenarios from other equipment.
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Ferritic and Martensitic stainless steels such as those of the 13Cr family are susceptible to bothsulphide stress cracking (SSC) and stress corrosion Cracking (SCC) and therefore their applicationshall be in accordance to DEP.30.10.01.15.
Austeni tic stain less steels containing less chromium, nickel and molybdenum than AISI 316, such
as AISI 304, shall not be used / applied in PDO production facilities as defi