MSS SP-137-2020提供了金属法兰、配件、阀门和阀门及其他管道部件的压力边界零件的材料正识别（PMI）方法和验收标准。本标准实施规程涵盖的PMI测试所用仪器应为光谱仪或X射线荧光仪。本标准实施规程适用于制造过程中最终检验或过程检验时的识别过程。PMI测试仅用于材料等级鉴定，不能替代制造商的测试报告或实验室的化学分析。

MSS SP-137-2020 provides methods and acceptance standards for Positive Material Identification (PMI) of metal flanges, fittings, valves, and pressure boundary parts of valves and other piping components.The instrumentation used for PMI testing covered by this Standard Practice shall be optical spectroscopy or X-ray fluorescence.This Standard Practice is applicable to the identification process, at point of final inspection or in-process inspection during manufacturing.The PMI test is for material grade identification only and does not substitute for a manufacturer's test report or a laboratory's chemical analysis.