Hardness on P1 after PWHT

[bob74r]

We are currently doing 100% Hardness on P1 material after PWHT. These spools are locally Heat Treated and is completed purely for thickness (close to an inch)
Client spec does not state anything on hardness testing and these spools are built to b31.3.
I personally believe this is a good practice in which we will keep on doing but I am curious if this is actually a code requirement? (mind you have seen P1 material come back hard due to improper stress relieving though in one case I had a 4" come back close to 350 BHN but chrome rod was used instead of carbon)
331.1.7 states "(a) Where a hardness limit is specified in Table 331.1.1 at least 10% of welds, hot bends, and hot formed components in each furnace heat treated batch and 100% of those locally heat treated shall be tested."
Table 331.1.1 does not state a max hardness for P1 material
Now I wouldn't be asking this question but 331.1.1 also does not state a max hardness for P9 and some P5 (I seriously hope anyone dealing with P9 is doing 100% hardness after PWHT)
This questions is just for my information, as curious if i am missing something or if I always have been and will be performing extra NDE. (Id rather perform too much NDE and take the bullet for the $ that costs then have an unknown issue continue..... wrong rod example)

 

[DVWE]

Most industry standards for hardness on P1 after PWHT is 200 BHN max. Occasionally I have seen allowables up to 225 BHN. There are plenty of other specs such as API and NACE which specify hardness limits for P1.

As far as you doing extra testing, why not? Especially if you have your own equipment, it's not much of an expense. Now when you have to sub-contract it, I can see a bean counter having some issues with that.

 

[stanweld]

B31.3 does not require hardness testing of carbon steels after PWHT. Expected hardness values after PWHT have a wide range from 120 BHN to approximately 200 BHN. Of the many hubdreds of tests that I have had conducted,the vast majority of values are within 140 to 160 BHN after PWHT.

 

[metengr]

I personally believe this is a good practice in which we will keep on doing but I am curious if this is actually a code requirement?

No. Most hardness testing is performed for QC reasons on P1 material to validate PWHT or a client specification requires hardness testing for service OR for corrosion service conditions. Just to conduct hardness testing because it is a ni ce thing to do is overkill.

We have Grade T9 and T5 and some P5 butt welds in steam service, and I do not conduct hardness testing. We have hold points and require PWHT charts for in-situ PWHT. Never had a problem.

Now for creep strength enhanced ferritic steels, this is a different matter.

 

[deco0404]

Stanweld is right, we work in Vickers and for P1's the average is 140-150Hv

Declan

 

[PAN]

Declan,

Do you mean HV 5? Please advise...

 

[mpdjw]

Just to clarify, the term P1 on its own can sometimes be misleading. P1 can refer to either of the following:

The material grouping in ASME IX (carbon steel)
The specific material grade from ASTM A335 (0.5Mo low alloy steel - which has a material grouping of P3)

Which is it in this case?

It may not matter because some recommended practices such as API 582 have the same 225HB limit for P1, P3 and P4 materials. (unless they are subject to sour service or other specific process conditions).