NOTICE: MSS SP-87-1991 (R 1996) was reinstated in 2011 for the purpose of making an active version available to those utilizing the Standard Practice and/or complying with nuclear-related codes and piping applications.

Pipe Fittings for Nuclear Class I applications require dimensional and testing controls beyond those presently contained in existing ANSI Standards to provide more stringent design adequacy requirements in keeping with the high reliability needed for Class I nuclear power plant piping systems.

he objective of this Standard is to provide production type fittings which are suitable for application of the stress indices and flexibility factors given in NB 3600 of the ASME Boiler and Pressure Vessel Code, Section III, Division 1, Nuclear Power Plant components. It is recognized that certain conditions will require fittings over and beyond the scope of this standard and in order not to complicate this production fitting standard, such fitting must be negotiated between purchaser and manufacturer.

This standard covers overall dimensions, tolerances and marking for wrought carbon and alloy steel (ferritic and austenitic) factory made welding fittings including long and short radius, 90 degree elbows (not reducing), 45 degree long radius elbows, 180 degree long and short radius returns, straight and reducing tees, concentric reducers and caps. Both seamless, and welded fittings manufactured to the requirements of Section III Nuclear Power Plant Components are included. In case of conflict between this standard and ANSI/ASME B16.9 or ANSI/ASME B16.28, the requirements of this standard are applicable.