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MSS: Manufacturers Standardization Society of the Valve and Fittings Industry, Inc.

MSS, the Manufacturers Standardization Society of the Valve and Fittings Industry is a non-profit standards developing organization that is devoted to the development of the industry. Standards written by MSS address valves, valve actuators, valve modification, pipe fittings, pipe hangers, pipe supports, flanges, and associated seals. These materials and associated guidelines are used in almost every industry, and are found in facilities for waste management, nuclear energy, and oil refining. Standards from MSS are available both individually, directly through the ANSI webstore, and as part of a Standards Subscription. If you or your organization are interested in easy, managed, online access to standards that can be shared, a Standards Subscription may be what you need - please contact us at: StandardsSubscriptions@ansi.org or 1-212-642-4980 or Request Proposal Price.

Below are MSS's best-selling standards. To find additional standards, please use the search bar above.

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ANSI/MSS SP-58-2009

Pipe Hangers and Supports - Materials, Design, Manufacture, Selection, Application, and Installation

This document has been substantially revised from the previous 2002 edition, INCLUDING THE ADDITION OF INFORMATION FROM ANSI/MSS SP-69, MSS SP-77, MSS SP-89, AND MSS SP-90.  
  This Standard Practice establishes the material, design, fabrication, and inspection criteria to be used in the manufacture of standard types of pipe hanger components.  
  This Standard Practice establishes the allowable stress values for materials used in standard types of pipe support components and unique hanger design assemblies.  
  This Standard Practice establishes minimum design load ratings for rigid pipe hanger assemblies. 


ANSI/MSS SP-55-2011

Quality Standard for Steel Castings for Valves, Flanges, Fittings, and Other Piping Components - Visual Method for Evaluation of Surface Irregularities

This Standard Practice is intended to supplement the requirements of ASTM Specifications A216/A 216M, A217/A217M, A351/A351M, A352/A352M, A3891A389M, A487/A487M, and A744/A744M and to provide a series of reference photographs typical of the various surface irregularities common to steel pressure castings and illustrations of generally acceptable and generally rejectable quality. Table 1 of Section 5 is provided to show MSS interpretation as to the relationship between this Standard Practice and the levels of surface quality illustrated by the comparators and the photographs of the Steel Casting Research and Trade Association (SCRA TA) Comparators for the Definition of Surface Quality of Steel Castings.
For additional nondestructive examinations defining quality of steel castings, this Standard Practice may be supplemented by the following Standard Practices; SP-53 "Magnetic Particle Examination Method", SP-54 "Radiographic Examination Method", SP-93 "Liquid Penetrant Examination Method", SP-94 "Ultrasonic Examination Method", and SP-112 "Visual and Tactile Method".


ANSI/MSS SP-25-2013

Standard Marking System for Valves, Fittings, Flanges, and Unions

This standard marking system applies to valves, fittings, flanges, and unions used in piping connections which include (but are not limited to) flanged, soldered, brazed, threaded, or welded joints.


MSS SP-6-2017

Standard Finishes for Contact Faces of Pipe Flanges and Connecting-End Flanges of Valves and Fittings

Pertains to the finish of gasket contact faces of pipe flanges and connecting end flanges of valves and fittings.



MSS SP-127-2014a

Bracing for Piping Systems: Seismic - Wind - Dynamic Design, Selection, and Application

This Standard Practice establishes the material, design, fabrication, and inspection criteria to be used in the manufacture, selection, and application of standard types of bracing assemblies. This Standard Practice presents recommended guidelines for providing stability in piping systems for protection against seismic, wind, and other dynamic forces. This Standard Practice is intended for use on piping systems where formal engineered bracing design may not have been performed. Note that local and/or national building codes or regulations may supersede or augment these requirements. This Standard Practice applies to rigidly connected metallic pipe only (welded, flanged, mechanical-jointed, etc.). For other types of pipe and pipe connections, contact the applicable pipe manufacturer for information.


MSS SP-99-2016

Instrument Valves

This Standard Practice applies to small valves and manifold valves developed for and predominantly used in instrument, control, and sampling piping systems. It covers steel and alloy valves of nominal pipe size (NPS) 2 and smaller, and pressure ratings of 15,000 psi (103.4 MPa) and lower at 100 F (38 C). See MSS SP-105 for instrument valves involving code applications. This Standard Practice applies to instrument valve designs including, but not limited to, needle valves, packless valves, ball valves, plug valves, check valves and manifold valves. Instrument valves are generally of proprietary design. This Standard Practice is not intended to define or limit designs, construction, performance, envelope dimensions, or valve types.


MSS SP-93-2014

Quality Standard for Steel Castings and Forgings for Valves, Flanges, Fittings, and Other Piping Components û Liquid Penetrant Examination Method

Provides methods and acceptance standards for liquid penetrant examination of steel castings and forgings for valves, flanges, fittings and other piping components. It is applicable to examination of repairs as well as to initial examination of castings and forgings. The methods of Section 4 provide uniform procedures which will produce satisfactory and consistent results upon which the Acceptance Standards of Table 1 may be used. This Standard Practice includes the examination of pressure containing castings and forgings.


MSS SP-97-2012

Integrally Reinforced Forged Branch Outlet Fittings - Socket Welding, Threaded, and Buttwelding Ends

This Standard Practice covers essential dimensions, finish, tolerances, testing, marking, material, and minimum strength requirements for 90 and 45 degree integrally reinforced forged branch outlet fittings of buttwelding, socket welding, and threaded types.


MSS SP-99-2016a

Instrument Valves

This Standard Practice applies to small valves and manifold valves developed for and predominantly used in instrument, control, and sampling piping systems. It covers steel and alloy valves of nominal pipe size (NPS) 2 and smaller, and pressure ratings of 15,000 psi (103.4 MPa) and lower at 100 F (38 C). See MSS SP-105 for instrument valves involving code applications. This Standard Practice applies to instrument valve designs including, but not limited to, needle valves, packless valves, ball valves, plug valves, check valves and manifold valves. Instrument valves are generally of proprietary design. This Standard Practice is not intended to define or limit designs, construction, performance, envelope dimensions, or valve types.


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