Hardness after PWHT

[akvtech]

Where can I find the requirements for hardness testing of vessels after PWHT and/or the maximum hardness values of various metals typical to pressure vessel fabrication (P4, P5 etc..)

 

[metengr]

There is no hardness requirement in ASME Section VIII for service. However, if you want general guidance for hardness requirements after PWHT look at B31.3 Piping Code.

 

[akvtech]

Do you think it reasonable to ask the vendor to prove up the PWHT effectiveness with brinells (I prefer from the process side) on these 2-1/2" to 3-1/2" thk reactor vesels (SA-387-11 CL2) Otherwise all I have is a chart.

 

[jamesl]

It is common practice to require prodcution hardness testing (after PWHT) on P4 materials.

 

[DVWE]

Do you think it reasonable to ask the vendor to prove up the PWHT effectiveness with brinells (I prefer from the process side) on these 2-1/2" to 3-1/2" thk reactor vesels (SA-387-11 CL2) Otherwise all I have is a chart.

Absolutely it is reasonable to ask that. But these type of requirments are typically spelled out in the Purchase Order stage.

Also, look to API 582, API 934, and Nace MR0175 for hardness requirements for P-No. 4. Usually, it is 225 BHN Maximum.

 

[akvtech]

Thanks to all for your replies...I am affecting the change in our standard so it will be part of future RFQ and POs.

 

[Guest102023]

If you are talking about heat-affected zone hardness, forget about using Brinell directly. Another suitable method, converted to BHN via ASTM E140 will be OK. Don't forget you will need to prepare the surface and then etch to locate the HAZ.

(Personally I believe Brinell should be confined to foundries.)

 

[Duwe6]

Typical practice is to just Brinnell the center of the weld cap, into a flat spot ground or filed into the cap. Post-PWHT hardness will tell you if the stress-relief was effective.

The 'Main Event' is the chart from a calibrated chart recorder hooked up to the PWHT thermocouples. If you have *any* doubts about the veracity of the PWHT contractor, you need to have your in-house QC or Eng take the Brinnell readings. Hardness readings are much easier to fake than a chart recording.

 

[akvtech]

Brimstoner...Vickers or other hardness tests are ok as results can convert to BHN. I choose to sample a cross section of base metal away from the haz, in the haz and of the weld. Its a preference thing that gives me an snap shot of the entire cross section. And taken on the side that is in the process environment on thicker vessels.
Thanks

 

[Guest102023]

akventech,
I was not considering cross sections, just measurements on the PV.
I have also found through my own informal lab trials that conversion via E140 is not very 'accurate'. I always preface reported results with 'approximate equivalent values'.