Purchasing Guide for Wellhead & Christmas Tree ... - Stream Flo

API Specification 6AAPI Specification 6A (ISO 10423) is the recognizedindustry standard for wellhead and christmas treeequipment that was formulated to provide for theavailability of safe, dimensionally and functionallyinterchangeable wellhead and christmas treeequipment. This specification includes detailedrequirements for the manufacture of tubularsuspension equipment, valves, and fittings usedat the location of oil and gas wells to contain andcontrol pressure and fluid flows.Specification 6A also serves as the referencesource for the design of flanged end and outletconnections for use at 2,000 to 20,000 psimaximum rated working pressures and a familyof gate valves for use over these same pressureranges.Since API Specification 18th Edition waswithdrawn, this booklet covers the 19th Editionwith references to the 17th Edition.Abbreviated TermsAQL Acceptable Quality Level PQR Procedure Qualification RecordCRA Corrosion Resistant Alloy PR Performance RequirementDAC Distance Amplitude Curve PSL Product Specification LevelER Equivalent Round QTC Qualification Test CouponFEA Finite Element Analysis r.m.s. Root Mean SquareHAZ Heat Affected Zone RL Repair/Remanufacture LevelHBW Brinell Hardness R mUltimate Tensile StrengthHIP Hot Isostatic Pressing ROE Radius of ExposureHRB Rockwell Hardness Scale B SSV Surface Safety ValveHRC Rockwell Hardness Scale C TC Test CouponNDE Nondestructive Examination UNS Unified Numbering SystemNPT National Pipe Thread USV Underwater Safety ValveOEC Other End Connection WPQ Welder Performance QualificationOEM Original Equipment Manufacturer WPS Welding Procedure Specification1

Material ClassesMaterial ClassBody, Bonnet, End &Outlet ConnectionsMinimum Material RequirementsPressure-Controlling Parts,Stems & Mandrel HangersAA - General Service Carbon or Low-alloy Steel Carbon or Low-alloy SteelBB - General Service Carbon or Low-alloy Steel Stainless SteelCC - General Service Stainless Steel Stainless SteelDD - Sour Service a Carbon or Low-alloy Steel b Carbon or Low-alloy Steel bEE - Sour Service a Carbon or Low alloy Steel b Stainless Steel bFF - Sour Service a Stainless Steel Stainless Steel bHH - Sour Service a CRAs bcd CRAs bcdZZ - Sour Service User Defined User DefinedaAs defined by NACE MR0175/ISO 15156 in compliance with NACE MR0175/ISO 15156.bIn compliance with NACE MR0175/ISO 15156.cCRA required on retained fluid wetted surfaces only. CRA cladding of low alloy or stainless steel ispermitted.dCRA as defined in Clause 3 of this International Standard. NACE MR0175/ISO 15156 definition of CRAdoes not apply.API 6A Annex O: Material Class ZZNACE MR0175/ISO 15156 includes provisions for the qualification of materials for a specific sour serviceapplication which is outside the parameters defined in that standard by means of testing or documentedfield history. This can include MR0175/ISO 15156 or the use of materials not addressed in MR0175/ISO15156. For such sour service applications, equipment may be described and marked as Material Class ZZ.It is the responsibility of the purchaser to evaluate and determine the applicability of the documenteddata for the intended application. For material Class ZZ, the manufacturer shall meet materialspecifications supplied or approved by the purchaser and shall maintain traceable records to documentthe materials of construction, regardless of PSL.More NACE InformationMaterial Classes DD, EE, FF and HH require compliance to NACE MR0175 (ISO 15156) and responsibilityfor the choice rests with the purchaser.Examples of DesignationsClass FF-1.5 means:a) material class FFb) rated at 1.5 psia H 2S maximum allowable partial pressureClass NL means:a) where no H 2S limit is defined by NACE, NL shall be used for marking (i.e. DD-NL).8

Product Specification Levels (PSL)API Specification 6A (ISO 10423) recommends productspecification levels (PSLs) for equipment with qualitycontrol requirements for various service conditions. PSLsapply to primary equipment:••••tubing headstubing hangers, hanger couplingstubing head adapterslower master valvesAll other wellhead parts are classified as secondary. ThePSL for secondary equipment may be the same or lessthan the PSL for primary equipment.PSL Decision TreeRecommended minimum PSL for primary parts of wellhead and christmas tree equipment.startrated workingpressure≥103.5 MPa(15,000 psi)high H 2Sconcentration?yesPSL3G34.5 MPa(5,000 psi)gas well?yes33Gnono≤34.5 MPa(5,000 psi)no32gas well?yesrated workingpressure>34.5 MPa (5,000 psi)3no≤34.5 MPa (5,000 psi)2rated workingpressure>34.5 MPa (5,000 psi)2rated workingpressure>34.5 MPa(5,000 psi)gas well?yes≤34.5 MPa (5,000 psi)13≤34.5 MPa(5,000 psi)no219

API Marking Requirements and LocationsLocationMarkingWellheadEquipmentConnectorsand FittingsCasting andTubingHangersLooseConnectorsValves andChokesActuatorsISO 10423nameplateand/or bodynameplateand/or bodynameplateand/or bodyOD ofconnectornameplateand/or bodynameplateand/or bodytemperatureclass orrating (4.2.2)nameplateand/or bodynameplateand/or bodynameplateand/or bodyOD ofconnectornameplateand/or bodynameplateand/or body(actuatorscontainingretained fluid)material class(4.2.3)nameplateand/or bodynameplateand/or bodynameplateand/or bodyOD ofconnectornameplateand/or bodynameplateand/or body(actuatorscontainingretained fluid)productspecificationlevel (1.4)nameplateand/or bodynameplateand/or bodynameplateand/or bodyOD ofconnectornameplateand/or bodynameplateand/or body(actuatorscontainingretained fluid)performancerequirement level(4.1)nameplateand/or body-nameplateand/or bodyOD ofconnectornameplateand/or bodynameplateand/or bodynominal size(bore if required)nameplate orbody, andconnector ODnameplate orbody, andconnector ODnameplateand/or bodyOD ofconnectornameplateand/or bodynameplateand/or bodythread size(threadedproducts only)nameplate orbody, and/ornear eachthreadnameplate orbody, and/ornear eachthreadnameplateand/ornear eachconnectorOD ofconnectornameplate orbody, and/ornear eachthread-end and outletconnector sizenameplate orbody, andeachconnector ODnameplate orbody, andeachconnector OD-OD ofconnectornameplateand/or body-rated workingpressure (4.2.1)nameplate orbody, andeachconnector ODnameplate orbody, andeachconnector OD-OD ofconnectornameplate orbody, andeachconnectorOD-ring gasket typeand numbernear eachconnectornear eachconnector-OD ofconnectornear eachconnector-date ofmanufacturenameplateand/or bodynameplateand/or bodynameplateand/or bodyOD ofconnectornameplateand/or bodynameplateand/or bodymanufacturer’sname or marknameplateand/or bodynameplateand/or bodynameplateand/or bodyOD ofconnectornameplateand/or bodynameplateand/or bodyserial number(if applicable)nameplateand/or bodynameplateand/or bodynameplateand/or bodyOD ofconnectornameplateand/or bodynameplateand/or bodyhardness testvalues(if applicable)adjacent totest locationadjacent totest locationadjacent totest locationadjacent totest locationadjacent totest locationadjacent totest location10

ParameterQuality Control RequirementsBodies, Bonnets, End and Outlet Connections, and Hub End ConnectorsSubclause ReferencePSL 1 PSL 2 PSL 3/3G PSL 4Tensile Testing 7.4.2.1.1 7.4.2.2.1 7.4.2.2.1 7.4.2.2.1Impact Testing 7.4.2.1.2 7.4.2.2.2 7.4.2.3.2 7.4.2.3.2Hardness Testing 7.4.2.1.3 7.4.2.2.3 7.4.2.3.3 7.4.2.3.3NACE MR0175 7.4.1.5 7.4.1.5 7.4.1.5 7.4.1.5Dimensional Verification 7.4.2.1.4 7.4.2.1.4 7.4.2.3.4 7.4.2.3.4Traceability - 7.4.2.2.5 7.4.2.3.5 7.4.2.3.5Chemical Analysis - 7.4.2.2.6 7.4.2.2.6 7.4.2.2.6Visual Examination 7.4.2.1.5 7.4.2.1.5- -7.4.2.2.7Surface NDE - 7.4.2.2.87.4.2.2.97.4.2.3.8 7.4.2.3.8Weld NDEGeneralExamination VisualNDE SurfaceRepair WeldsNDE VolumetricHardness Testing7.4.2.1.6-----7.4.2.1.67.4.2.2.117.4.2.2.127.4.2.2.137.4.2.2.14-7.4.2.1.67.4.2.3.107.4.2.2.127.4.2.3.117.4.2.2.137.4.2.3.127.4.2.3.13No weldingpermittedexcept forweld overlays(see 7.4.2.4.9)Serialization - - 7.4.2.3.14 7.4.2.3.14Volumetric NDE - - 7.4.2.3.15 7.4.2.4.11Thread MarkingsThe thread type marking in accordance withISO 11960 shall be as follows:STCLCBCXLLPNUEUCasing: short threadCasing: long threadCasing: buttressCasing: extreme LineLine pipeTubing: non-upsetTubing: external upset11

Quality Control Requirements for WeldingWeld Type Stages PSL 1 PSL 2 PSL 3/3G PreparationPressure containingNon-pressure containingRepairPreparation - - aCompletion -a, b and(c or d)a, b, (c or d),and eno weldingpermittedPreparation - - a no weldingCompletion - a a and e permittedPreparation - h hCompletion -a, b, and(f or g)a, b, e and(f or g)no weldingpermittedWeld metal overlay (ring Preparation - - b bgrooves, stems, valve-boresealing mechanisms and Completion - b b bchoke trim)Weld metal corrosivePreparation a a a aresistant alloy overlay(bodies, bonnets and end Completion a,b a,b a, b, i a, b, iand outlet connections)a Visual examination.b Penetrant testing inspection for non-ferromagnetic materials and magnetic particle testing forferromagnetic material.c Radiation (radiography or imaging) examination.d Ultrasonic examination.e Hardness test (weld).f Ultrasonic examination only if weld is greater than 25% of wall thickness or 25 mm (1 in),whichever is less.g Radiation (radiography or imaging) examination only if weld is greater than 25% or wallthickness for PSL 2 or 20% of wall thickness for PSL 3, or 25 mm (1 in), whichever is less.h Penetrant or magnetic particle as applicable for material defects only.i Measurement of overlay thickness, testing of bond integrity and volumetric examinationshall be according to the manufacturer’s specifications. If the overlay is considered part of themanufacturer’s design criteria or of the design criteria of API 6A, volumetric examinations shallbe in accordance with the methods and acceptance criteria of 7.4.2.3.15.Note: preparation = surface preparation, joint preparation, fit up and preheatcompletion = after all welding, post-weld heat treat and machining12

Relative CorrosivityThe minimum partial pressure of carbon dioxiderequired to initiate corrosion and the relativeeffect of increasing partial pressures on thecorrosion rate are strongly influenced by otherenvironmental factors:a) temperatureb) H 2S levelc) pHd) chloride ion concentratione) sand productionf) water production and compositiong) types and relative amounts of producedhydrocarbonsFinally, the purchaser should consider future service of the well when selecting a material class. Thisshould not be limited to anticipated changes in the acid gas partial pressures for production or increasedwater production with or without increased chloride content, but also should include consideration ofoperations such as acidification or other well treatments.Relative Corrosiveness of Retained Fluidsas Indicated by CO 2Partial PressureRetained Fluids Retained Fluids Retained Fluids Mpa Retained Fluids (psia)general service noncorrosive 30)sour service noncorrosive

Severity of Sour Environment• determined in accordance with NACE MR0175/ISO 15156-1 with respect to SSC of a carbon or lowalloy steel6.50.3 kPa(0.05 psi)1in situ pH5.54.53.5023Key0 Region 01 SSC Region 12 SSC Region 23 SSC Region 32.50.11 10 100 1000H 2 S partial pressure, kPaIn defining the severity of the H 2S containing environment, the possibility of exposure to unbufferedcondensed aqueous phases of low pH during upset operating conditions or downtime, or to acids usedfor well stimulation and/or the back flow of stimulation acid after reaction should be considered.Note 1: The discontinuities in the figure below 0.3 kPa (0.05 psi) and above 1 MPa (150 psi)partial pressure H 2S reflect uncertainty with respect to the measurement of H 2S partialpressure (low H 2S) and steel’s performance outside these limits (both low and highH 2S).Note 2: Guidance on the calculation of H 2S partial pressure is given in Annex C.Note 3: Guidance on the calculation of pH is given in Annex D.The cracking behavior of CRAs and other alloys in H 2S containing environments can be affected bycomplex interactions of parameters, including the following:a) chemical composition, strength, heat treatment, microstructure, method of manufacture andfinished condition of the materialsb) H 2S partial pressure or equivalent dissolved concentration in the water phasec) acidity (in situ pH) of the water phased) chloride or other halide ion concentratione) presence of oxygen, sulfur or other oxidantsf) exposure temperatureg) pitting resistance of the material in the service environmenth) galvanic effectsi) total tensile stress (applied plus residual)j) exposureThese factors shall be considered when using this part of NACE MR0175/ISO 15156 for the selection ofmaterials suitable for environments containing H 2S in oil and gas production systems.14

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