ANSI/MSS SP-44-2026: Steel Pipeline Flanges

An American National Standard developed and published by the Manufacturers Standardization Society (MSS) of the Valve and Fittings Industry, Inc., MSS SP-44, has been revised. The current edition is ANSI/MSS SP-44-2026: Steel Pipeline Flanges.

About ANSI/MSS SP-44-2026

Pipeline creation and maintenance makes use of heavy demands and distinctive components and processes. Line pipe is uniquely characterized by high-strength, cold worked, thin-wall of the carbon steel grade, which necessitates special considerations for the welding end of the flanges. This concern was present as far back of the establishment of this standard around fifty years ago, after MSS had received continued requests for steel pipe flanges for pipeline use, particularly in sizes larger than those covered by ASME B16.5.

The ANSI/MSS SP-44-2026 standard practice covers pressure-temperature ratings, materials, dimensions, tolerances, marking, and testing for steel pipeline flanges. In accordance with the document, the welding neck type flanges are to be forged steel, while the blind flanges can be made from either forged steel or steel plate.

The pipe sizes covered by the standard, designated as the dimensionless nominal pipe size (NPS), are NPS 12 to NPS 60, in two number intervals, with dimensional and tolerance guidelines for NPS 10 and smaller being provided by reference to ASME B16.5. Please note that international standards make use of the nominal diameter “DN” system, and the corresponding values of these are listed in the document. ANSI/MSS SP-44-2026 addresses flanges of Class, 150, 300, 400, 600, or 900.

Changes to ANSI/MSS SP-44-2026

ANSI/MSS SP-44-2026 has undergone primarily editorial updates to clarify the requirements instituted in the 2016 and 2019 editions. These changes included:

• Section 2 “Definitions” was added in accordance with MSS requirements, and the remaining sections renumbered
• ASTM A515/A515M plate material was added to the weld compatibility list, the test location was clarified, Cu+Ni+Cr+Mo was removed from Tables 1 and E1, and the metric conversions and tolerance on hydrotesting allowance were harmonized with ASME B16
• Coverage was extended to include NPS 22 Class 900
• Annex D.1 was reclassified as Annex E and the following annex as Annex F

The previous two revisions of this American National Standard were quite significant, and you can read more about them below.

ANSI/MSS SP-44-2026: Steel Pipeline Flanges is available on the ANSI Webstore.

Changes to ANSI/MSS SP-44-2019

The previous revision of this standard, ANSI/MSS SP-44-2019, was substantially revised and reformatted. As discussed in the Foreword of this document:

“MSS members worked with a task group commissioned by API Committee on Standardization of Oilfield Equipment and Materials (CSOEM) Subcommittee 21 (Materials) to completely review and improve the Standard Practice.”

As a result of these efforts, ANSI/MSS SP-44-2019, which also incorporates the 2017 errata reissue of the standard, is distinguished by the following changes:

• The PLS2 option was added, as well as the corresponding Annex D.1 for “PSL2 Quality Requirements”
• The carbon equivalent (CE) is now calculated the same way as MSS SP-75
• Clarifications note that material is to be fully killed
• Emphasis was added to show that results from test coupons should be representative of the finished flanges
• The standard now prohibits weld repair without customer approval
• The standard now clarifies the conditions under which dual slope hubs may be certified to this Standard Practice
• Requirements for traceability and retention of records were added for the manufacturer’s quality control program
• Cosmetic requirements were established
• information to be contained on the Certified Material Test Report was detailed
• To align with external standards, references to “DN” were removed (except in Section
• 2.2) within the body and Tables and replaced with NPS

This edition also incorporated the 2017 errata reissue of the standard.

Changes to ANSI/MSS SP-44-2016 (and the 2017 Reissue)

Similarly, the 2016 revision of the ANSI/MSS SP-44-2016 standard was major, and its updates included:

• Defined chemistry limits (added a Table 1 and removed external references).
• Clarified the “lot” definition.
• Made impact testing at -50 °F mandatory for grades over F42.
• Added requirement for hardness testing.
• Clarified allowable heat treatment methods.
• Changed marking requirements.
• Added tolerances for raised face height and bolt hole diameter.
• Added requirements for Manufacturing Procedure Specification and Inspection and Test Plans.
• Added Figure 4 to illustrate test locations and orientation.
• Removed ring gasket dimensions and referenced ASME B16.20A.
• Added Supplementary Requirements SR1 through SR16.
• Updated and renumbered the reference annex.

To correct publication processing related errata, the 2017 reissue, ANSI/MSS SP-44-2016 (Reissue 2017), replaced the 2016 version of the standard. A separate errata sheet was also issued in September 2017 for insertion into the 2016 edition.

Questions About ANSI MSS SP-44?

ANSI/MSS SP-44 is developed and published by the Manufacturers Standardization Society (MSS) of the Valve and Fittings Industry, Inc.

Please direct any technical questions relating to this American National Standard to the developer. You can find the contact information for all ANSI-accredited standards developers here: List of ANSI-Accredited Standards Developers (ASDs).

For further information, please refer to: Who to Contact for Standards Related Questions.