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Understanding Requirements

Swagelok fluid system components made from either 316/316L or special alloys are available as products which meet the requirements of the NACE MR0175/ISO 15156 sour gas standard.  Valves and fittings from alloys 6HN (UNS N08367) and 2507 are available from bar stock and forgings which are manufactured with processes which have been qualified to the stringent requirements of the NORSOK M-650 supply chain qualification standard. 

NACE Requirements

The NACE MR0175/ISO 15156 standard lists prequalified materials for use in upstream oilfield equipment where sulfide-induced stress corrosion cracking may be a risk in sour environments, i.e., in oil/gas/seawater mixtures where hydrogen sulfide (H2S) is present.

The standard allows the use of tube fittings produced from cold-drawn 316 stainless steel and 6-Moly, respectively, in instrumentation and control systems. Nickel alloys can also be used in strain-hardened condition for instrumentation and control systems, and to handle process fluids.

The document includes:

  • Requirements for material conditions and properties
  • Environmental conditions for use of the materials
  • Qualifications for material use under specific sour gas conditions

Material Matters

Read more about selecting fluid system components for sour oilfields in Offshore Magazine.

NACE MRO175 / ISO 15156 Overview

NACE Requirements for Alloy 2507 Super Duplex Tube Fittings

NACE MR0175/ISO 15156 standard requirements for alloy 2507

For a Swagelok alloy 2507 tube fitting to function correctly, the nut and ferrules must be made from cold-drawn bar stock. This material has the strength necessary to grip to alloy 2507 tubing (which has a high surface hardness) and to hold to the high working pressures listed in Swagelok Tubing Data.

Swagelok alloy 2507 tube fittings with ordering numbers having the -SG2 designator meet NACE MR0175/ISO 15156 requirements for use in any equipment, according to Table A.24 of the standard, if the fittings are wetted internally, but not externally, by sour gas.

Material Matters

For more information, access Swagelok’s full data sheet: NACE MR0175-Compliant Alloy 2507 Super Duplex Tube, Pipe, and Weld Fittings.

NACE MR0175/ISO 15156 standard:

  • Straight tube fitting bodies are produced from solution annealed alloy 2507 bar stock
  • Shaped tube fitting bodies are produced from solution annealed alloy 2507 forgings
  • External threads of a tube fitting body that are not wetted by the system fluid may be produced by thread rolling
  • Internally wetted threads are cut
  • Tube fitting nuts are produced from cold-drawn alloy 2507 bar stock but are not wetted by the system fluid
  • Back ferrules are produced from cold-drawn 6-Moly bar stock but are not wetted by the system fluid
  • Front ferrules are produced from cold-drawn alloy 2507 bar stock
  • Nose of the front ferrule comprises a wetted surface; it is under compression and, therefore, not subject to stress corrosion cracking or sour gas cracking, as the standard states a tensile stress component is required to enable these cracking modes
  • Port connectors and plug inserts are produced from solution-annealed alloy 2507 bar stock 

NACE Requirements for Alloy 625 Standard and Medium-Pressure Tube Fittings

For a Swagelok alloy 625 tube fitting and medium pressure tube fitting to function correctly, the nut and ferrules must be made from cold-drawn bar stock. This material has the strength necessary to grip to 625 tubing and to hold to the high working pressures listed in Swagelok Tubing Data and Swagelok Medium and High-Pressure Fittings and Adapters—Special Alloy Materials.

Fittings with bodies made from cold-drawn bar stock meet the requirements of NACE MR0175/ISO 15156 Table A.14. Fittings meeting the requirements of Table A.13 are produced as follows:

  • Straight fitting bodies are produced from annealed bar stock
  • Shaped fitting bodies are produced from annealed forgings or annealed bar stock
  • Nuts are produced from solution-annealed and cold-drawn bar stock, but are not wetted by the system fluid
  • Back ferrules are produced from solution annealed and cold-drawn bar stock, but are not wetted by the system fluid
  • Front ferrules are produced from solution annealed and cold-drawn bar stock
  • Nose of the front ferrule comprises a wetted surface; it is under compression and, therefore, not subject to stress corrosion cracking or sour gas cracking, as the standard states a tensile stress component is required to enable these cracking modes
  • Plugs, port connectors, and tube adapters are produced from annealed bar stock

NACE Requirements for 6-Moly Alloy Tube, Pipe, and Weld Fittings

The NACE MR0175/ISO 15156 standard contains tables that describe material requirements and environmental limits for materials used in upstream sour gas applications. The NACE MR0175/ISO 15156 tables that define requirements for 6-Moly alloys are Tables A.8 and A.11.

Table A.8 specifies the environmental and material limits for highly alloyed austenitic stainless steels used for any equipment or components in any type of sour gas installation.

Table A.11 defines the environmental and material limits for highly alloyed austenitic stainless steels used as instrument tubing, control-line tubing, compression fittings,
and surface and downhole screen devices.

Material Matters

For more information, access Swagelok’s full data sheet: NACE MR0175/ISO 15156-Compliant 6-Moly Alloy Tube, Pipe, and Weld Fittings.

nace-6-moly

NORSOK Standards

NORSOK standards (developed by the Norwegian petroleum industry) outline material and supply chain requirements focused on:

  • Ensuring the safety and cost-effectiveness of operations
  • Replacing oil company specifications
  • Providing a basis for international standardization process
  • Withdrawing standard upon publication of international standard

In response to the growing interest in NORSOK-approved products, Swagelok is pleased to quote orders for tube fittings, pipe fittings, and select general industrial valve products manufactured from NORSOK-certified material. We offer products manufactured from 2507, 254, and 6HN bars and forgings that meet the requirements of the NORSOK M-650 supply chain qualification standard.

Details of the standard are listed in this table:

NORSOK standards chart

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For more information, check out these additional helpful reference materials from Swagelok.



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