Gaskets & NACE MR0175

[dgrande]

I am designing building an ASME Code Pressure Vessel per MR0175. The vessel is going to have solid metal RTJ type gaskets used for a Manway Closure. These gaskets are either going to be Soft Iron or Gr. 304SS.

The question is: Do these gaskets need to meet MR0175? I realize that they will be exposed to the process fluid, but gaskets usually are not considered to be subject to corrosion. Plus, if these gaskets were Soft Iron or Gr. 304SS Jacketed gaskets, it would be impossible to perform any type of hardness testing on them.

Any input would be greatly appreciated.

 

[SJones]

Ideally, they would have to meet ISO 15156 hardness requirements and - as per good sealing practice - hardness requirements can be specified for these type of gaskets. An example of this can be seen in API 6A and the Flexitallic ring joint catalogue. In the scheme of things, it is misleading because the gaskets will work harden after flange tightening in any case.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[dgrande]

For RTJ gaskets, the hardness will be easy to verify. The problem is that if I apply NACE to RTJ gaskets, then I will have to apply it to metal jacketed gaskets & then I will not be able to verify hardness values.

 

[vesselguy]

Correct me if I'm wrong, but NACE MR0175/ISO15156 does not apply to gaskets.

 

[dgrande]

vesselguy,

I believe that you are correct. I was just looking for some confirmation.

 

[SJones]

Only if you can guarantee no tensile stresses WHATSOEVER.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[Riadsala]

Note also that there are a lot of cheap gaskets out there which may deviate (significantly!) in hardness from their certified level. The only way to be sure is to order forged gaskets and have each hardness tested....

Riadsala
Metallurgist in the Offshore O&G industry