PRCI Report 214

L51721e

Battelle Memorial Institute

Need: Fittings specified to be in accordance with MSS SP-75 have been found by purchasers to have fitting yield strengths less than the matching specified pipe without the marking required in MSS SP-75 17.1c. As will be discussed, there are two strength requirements in MSS SP-79 Section 8 Tensile Properties.

Benefit: The report provides guidance for the evaluation of as-received fittings. The types of fittings considered are elbows, tees, caps and reducers conforming to Manufacturers Standardization Society Standard Practice 75, Specification for High Test Wrought Butt Welding Fittings (1993 edition).

Result: Guidance for estimating the burst strength of fittings is in the form of functionality relating burst-strength rations to ultimate tensile-strength ratios. Also concepts are presented that allow for the estimation of yield pressure for a fitting. The latter is given as a first approach to the subject as the yield pressure of a fitting has not been precisely defined.