Steel fittings : Limitations on SMYS : SR 5, MSS-SP-75

[nipra03]

I am seeking any help regarding the rationale behind the limitation on actual yield strength to 20000 psi as specified by supplementary requirement SR 5 of MSS-SP-75, spec. for butt welded steel fittings.
This requirement is not reflected in ASME B16.9.
I have been told it is to ensure better weldability and to prevent manufacturers from deliberately specifying higher grade material as lower grade Secondly if this is true then it is reasonable to conclude this requirement should be limited to welded fittings and flanges only and need not include blind flanges or spacer rings etc.

Any feedback appreciated.

 

[BigInch]

Obviously it can only apply to welded fittings.
If you want higher strength, specify the WPHY grade you want.

 

[LittleInch]

nipra, your quote is not complete. SR 5 states "actual yield strength shall not exceed specified by more than 20000 psi.

The SRs are supplementary requirements which are only valid if you ask for them.

MSS- SP 75 is for welded fittings ( elbows, tees, caps, reducers etc)

Flanges and related items like blinds are to MSS-SP-44.

Therefore I believe your supposition is correct as MSS-SP 75 does not cover flanges.

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