Hardness test location 1

[SiggiN]

Hi all!

I was hoping someone could clarify the rational behind selection of hardness test location after final machining on pressure containing parts (PSL 3 subsea application)?

Background/context:
For the most part API 6A will be the governing standard in my case, according to 10.4.1.4 parts shall be individually tested to confirm NACE values (I'm assuming this is after final machining).

10.4.2.4.1 does hint at a location for PSL 3; "[...] additional test on each end connector face [...]", if this is not possible then test on "[...] nearest accesible surface".

As an example suppose the geometry has a varying cross section and is machined from bar such as this flange:

Where would you specifiy hardness test location?

Thank you!

Regards
Siggi

 

[jmec87]

My best guess for the reason behind the PSL3 requirement to hardness test on each end connector face is to minimize the risk of a hard area in/near the wetted surfaces that might not be caught by hardness testing far away on a large body. You generally can't hardness test the bore directly, so the closest you can get is the end connector face. In some cases (such as a top connector and some threaded connectors), it is physically impossible to hardness test the end connector face, which is why the "nearest accessible surface" clause was added in API 6A 21st Edition.

For your weldneck flange example, you would have to hardness test on the flange face (left side of your image). Per the definition in API 6A 21st Edition 3.1.28, "a weld preparation is not an end connector", so API 6A does not require you to hardness test at the weld preparation.

Per API 6A 10.4.2.4.2, "[Hardness] Tests shall be performed at a location determined by the manufacturer's specifications...", so it is up to the manufacturer to specify the hardness test location.

Note that while NACE MR0175 specifies hardness limits, it does not specify the number, type, or location of tests required to verify conformance to those limits (except for welding).