These specifications apply to the design and fabrication of skid mounted production vessels, including all associated piping, fittings and valves, etc., mounted on the skid where intended use of the equipment for H2S service is at temperatures as low as -25°F. All material shall comply with NACE Standard MR-01-75, latest edition, "Sulphide Stress Cracking Resistant Metallic Materials for Oilfield Equipment".
1 Materials
1.1 General requirements applicable to all construction components
1.All carbon and low alloy steels in contact with sour fluids shall have a hardness of Rockwell C-22 maximum.
2.The carbon equivalent:
$C.E.=C+{{Mn} \over 6}+{{Cr+Mo+V} \over 5}+{{Ni+Cu} \over {15}}$ shall be £0.45% with Cmax = 0.23%.
3.The Charpy V-notch impact value at -25°F shall be 27 Joules minimum, average of three full size 10mm ´ 10mm specimens. The lowest value of any one specimen shall be 19 Joules. Procedure for selecting specimens and adjusting values when less than full size specimens are used shall be in accordance with ASME SA-333. The largest practical specimen of full, 2/3 or 1/2 size shall be used.
4.Material used for construction must be new.
5.No repair of defects in the tubular products will be permitted.
6.Continuous tubular sections shall be used between fittings. (Joining of short sections of tubular products is not permitted).
7.Materials shall be free of protective coating, both internally and externally.
8.Material shall be marked with steel dies or marking tongs which indent the metal only as noted. Otherwise, it shall be marked with paint stencil.
1.2 Vessels
Shell and heads shall be in accordance with ASME specification SA-516, Grades 55 or 65 plus Supplementary Requirement S5.
1.3 Pipe
1.All pipe forming an integral part of the vessel and thus normally falling within the jurisdiction of ASME Boiler & Pressure Vessel Code, Section VIII, Division 1, shall be in accordance with ASME Specification SA-333, Grade 1 or 6.
2.All pipe flange connected to the vessel, but mounted on the skid, shall also be in accordance with ASME Specification SA-333, Grade 1 or 6 or as an alternative, may be made to API Standard 5L, Grade B, X42, X46 or X52, providing that it meets the "General Requirements" noted in Section 1.1, and if cold expanded, it has been tempered at 1150°F minimum after having been cold expanded.
1.4 Weld neck flanges
1.Material shall be in accordance with ASME Specification SA-350, Grade LF2, except it shall also comply with "General Requirements" noted above.
2.Identification: Flanges shall be fully identified in a permanent manner by one of the following methods:
a)Hot stamping (part above 1150°F) with rounded die impressions.
b)Cold stamping with rounded die impressions prior to final heat treatment.
1.5 Welded fittings
1.Material shall be in accordance with ASME Specification SA-420, Grade WPL-6, except it shall also comply with "General Requirements" noted above.
2.Identification: Fittings shall be fully identified in a permanent manner by one of the following methods:
a)Hot stamping (part above 1150°F) with rounded die impressions.
b)Cold stamping with rounded die impressions prior to final heat treatment.
1.6 Gaskets
1.Raised face flanged connection
a)Gaskets shall be spiral wound metal, asbestos filled, made in accordance with ANSI B16.5 Annex-E, Group 1b. Spiral round metal should be fully annealed, Type 316 stainless steel, Monel 400, or Inconel 600.
b)Metal hardness shall not exceed Rockwell C-20.
c)Gasket outside diameter shall be extended beyond the raised face by means of a centering ring equal in diameter to the bolt circle minus one bolt diameter (tolerance +0-1/8").
2.Ring joint flanged connection
a)Gaskets shall be fully annealed Type 316 stainless steel, Monel 400 or Inconel 600 made in accordance with ANSI B16.20 latest revision.
b)All ring gaskets shall be octagonal self-sealing type.
c)Hardness shall not exceed Rockwell C-20.
1.7 Valves
1.The following material shall not be used:
a)Low and medium alloy steel containing more than 1% nickel.
b)Free machining materials containing more than 0.08% sulphur.
c)Cold finished low and medium alloy steels, cold finished stainless steel and cold finished Monel K-500, in the cold finished condition.
d)AISI 400 Series stainless steel.
e)Precipitation hardened stainless steels, 17-4 PH and 17-7 PH. Use of other PH steels shall be subject to agreement between the Company and Manufacturer.
2.All steel materials for bodies and bonnets shall be capable of one of the following impact properties:
a)Charpy V-notch impact specimens when tested at -25°F shall exhibit a minimum of 50% shear fracture.
b)The Charpy V-notch impact value at -25°F shall be 27 Joules minimum, average of three full size 10mm ´ 10mm specimens. The lowest value of any one specimen shall be 19 Joules, except as modified by Section 4.4.
c)Cast materials shall conform to Charpy test requirements of ASTM A-352, Grade LCC. Forged materials shall conform to Charpy test requirements of ASTM A-350, Grade LF2.
d)All Charpy specimens shall be prepared and tested in accordance with ASTM E-23, latest edition.
e)Bolting for bonnets and flanges: see Section 13.2.8.
1.8 Bolts, studies and nuts
Materials shall be in accordance with ASTM A-193, Grade B7M for bolting and ASTM Specification A-194, 2HM for nuts. Bolts and studs made to this specification will be marked B7M and nuts will be marked 2HM.
1.9 Instrument piping
300 Series stainless steel in the annealed condition is acceptable for instrument piping as long as its hardness is less than Rockwell C-22.
1.10 Hammer union connections
Material shall comply with relevent sections of "General Requirements".
2 Design, fabrication, testing and inspection
Design criteria, fabrication, testing and inspection procedures shall comply with Section VIII, Division 1, of the ASME Boiler & Pressure Vessel Code and as dictated by the material specification noted heretofore. Heater coils shall in addition comply with API Specification 12K for Indirect Type Oil Field Heaters. Additional requirements are as follows:
1.No backing rings on welds shall be permitted and components having different internal diameters shall be internally bevelled to form a smooth transition from one internal diameter to the other.
2.Welds shall be 100% radiographed and the radiographs interpreted by a third party testing firm in accordance with standards set forth in Section VIII, Division 1, of the ASME Boiler & Pressure Vessel Code.
3.Drawings locating each weld with correlation to a radiograph record shall be furnished by the fabricator to the Company.
4.All welds shall be preheated of from 212°F to 300°F.
5.Only low hydrogen electrodes shall be used.
6.All welds shall be stress relieved at a temperature of 1150°F to 1220°F to reduce residual stresses and limit hardness to Rockwell C-22 maximum as required by NACE Standard MR-01-75, using the technique specified in UCS-56 of Section VIII, Division 1, of the ASME Boiler & Pressure Vessel Code.
7.These specifications shall apply to all piping mounted on the skid regardless of whether or not it falls within the strict jurisdiction of Section VIII, Division 1, of the ASME Boiler & Pressure Vessel Code as defined on page 1 of that document.
8.All pressure vessels shall have 1/8" additional material thickness for corrosion allowance.
9.All pipe shall have 1/16" additional material thickness for corrosion allowance.
3 Other design criteria
1.Skids;
a)Maximum width shall be 8 (eight) feet.
b)No component shall extend over the edge of the skid.
c)Skid end design shall permit loading and unloading unit with an oil field type winch truck over a rolling tailgate.
d)Lifting eyes shall be provided to allow handling unit with a crane.
2.Vessel supports shall be of sufficient strength and rigidity to support vessel when full and absorb any vibration that may be encountered in transit or on a offshore drilling unit.
3.Pipe brackets shall be of sufficient strength and rigidity, and number, to support the piping while the unit is in operation, as well as during loading and transporting the unit.
4.Protective framing, when ordered, shall enclose all components mounted on the skid and shall be strong enough to resist distortion in event of impacts as may occur when loading or off loading onto a floating vessel by crane. Lifting lugs shall be installed on top of framework for handling unit. The framework shall be removable from the skid by removal of fastening pins or bolts.
5.Enclosure: When ordered, the top and sides of the unit shall be enclosed. The top of the enclosure may be welded checker plate installed as a permanent part of the frame. The sides shall be easily removable panels. Galvanised sheet metal panels held in place by "U"-shaped channel members it top and bottom is an acceptable method.
4 Documentation
4.1 Tubular products, weld neck flanges, welding fittings
1.Certification that material used conforms to that specified.
2.Chemical analysis of each heat of steel.
3.Hardness test results from each heat/heat treatment lot.
4.Impact test results from each heat/heat treatment lot.
4.2 Gaskets
1.Certification that gaskets were made in accordance with specifications.
2.Type of materials used.
3.Hardness test results.
4.3 Valves
1.Certification that valves are made to the requirements as specified.
2.Chemical analysis of each heat of steel used in the valve bodies and bonnets.
3.Hardness test results for valve bodies and bonnets.
4.Impact test results for each heat/heat treatment lot for valve bodies and bonnets.
4.4 Steel bolding material
1.Certification that material is in confidence with these specifications.
2.Chemical analysis for each heat of steel.
3.Heat treatment.
4.Tension test results for each heat/heat treatment lot.
a)Minimum yield.
b)Tensile strength.
c)Elongation.
d)Reduction of area.
4.5 Pressure vessels
1.Pressure vessels shall be marked as specified by Section VIII, Division 1, of the Boiler & Pressure Vessel Code and shall be accompanied by the appropriate ASME Manufacturers Data Report.
2.Vessel shell and heads:
a)Chemical analysis for each heat of steel.
b)Hardness test results for each heat/heat treatment lot.
c)Impact test results for each heat/heat treatment lot.
3.Other reports covered under Section 4.1, 4.2, 4.3 and 1.7 of these specifications.
5 Painting
1.Blast all surfaces to white metal with appropriate abrasive per SSPC-SP-#5 or NACE Publication No. 53-1.
2.Apply one coat of Americoat Dimetcote #6 inorganic zinc, or equivalent, 3.5-6.0 mils dry film thickness and allow 24 hours drying time.
3.Apply one coat of Americoat #54 red coloured tie coat, or equivalent, 1.0-3.0 mils dry film thickness and allow 2-4 hours drying time.
4.Apply two coats of Company specified paint, 4.0 mils dry film thickness. Allow two hours minimum drying time between coats.
6 Condition of acceptance
A contract for equipment made to these specifications will not be considered complete and ready for payment unless the equipment is accompanied by a full set of certifications demonstrating compliance with material specifications, welding specifications and inspections procedures by a third party as set forth herein and as specified within referenced API, ASTM and ASME publications.