PMI on ASME Materials 1

[Sharik]

A company has a lot of unidentified carbon steel piping which they would like to use for ASME B31.3, General Service conditions. Is it acceptable to do PMI with a machine such as the SpectroTest Spark Analyzer, determine the chemical composition of the piping and then certify it acceptable for ASME Code use? Must samples also be cut out for tensile and yeild strength tests?

 

[metengr]

The positive material identification (PMI) will not help because you need to know the carbon content of the unidentified steel.

What you can do is remove a sample, send it to a test lab and have a full chemical analysis performed along with hardness testing to type the material.

 

[Sharik]

The Spectro Test Model TXC25 Spark Analyzer does actually give all the element values for the test pieces, even carbon steel. But the output report gives specifications which would also be for: SA-106 B, SA-53 B, SA-105, SA-333 6, etc. So it doesn't really help and I don't see how an NDE company can use this equipment and indicate on their report, the unidentifed piping is SA-106 B.

 

[metengr]

By having a materials lab perform a full chemical analysis AND hardness testing you can type the material as meeting the chemical and mechanical properties (UTS using the hardness conversion) of a specific specification. I have done this many times. All the Code requires is responsibility and traceability associated with identification of unknown material.

 

[Sharik]

What does the hardness have to do with material identification? There are no references to hardness in ASME Section II, Part A for SA-106 B. There are requirements for tensile and yield strengths though.

The only requirements for hardness values I can find are for the maximum hardness values for welded connections after heat treatment (B31.3, Table 331.1.1). And these maximum values are for alloy steels.

 

[metengr]

What does the hardness have to do with material identification?

The hardness test is used to assist in identification. How? It is used to determine approximate tensile strength (from a hardness conversion) and if the unknown material has been subjected to heat treatment. Chemical analysis alone is not sufficient to type the material.