the numbers here dont seem to add up here, I find it strange that you
would have hardness of 260-320 in the weld, but only 115-150 in the HAZ!
are you sure these readings are in the HAZ, and not outside the PWHT
zone. The numbers given are what you would expect for P11 & P22 pipe,
but not where the weld hardness is that high,
before addressing your queries, I would say that if this work has been
done at your site, why not get PWHT done again?
1- speak to your client, they may grant a concession, but I wouldn't if
I was the client
2- The allowable hardness for SH Steam and gas service are different (SH
has higher allowable values)
3- There is no way of knowing how soon something can happen, depends on
cycles, temp, environment etc...but some problems you may be faced with
are temper embrittlement, which will reduce ductility. These materials
are creep resistant materials, and this may suffer as well ( unlikely in
the short term though)
4- Not if it is done properly
Declan
On 08/09/2010 17:25, Ashfaq Anwer wrote:
>
> We are facing one serious concern regarding PWHT of weld joints of
> A335 Grade P11 & P22 piping in very high pressure superheated steam
> and syn gas service. Due to some unforeseen circumstances at our site,
> PWHT of some weld joints was not done effectively and resulted in
> higher hardness of weld joints although HAZ area hardness values are
> OK. The hardness number of weld joints is in the range of 260 - 320 HB
> which is unacceptable as per code requirements.
>
> I want to seek expert opinion on the following:
>
> 1. Can we take these weld joints is operation and defer PWHT for
> planned Outage in April 2010?
>
> 2. Is there any relaxation which can be taken in hardness readings,
> for example, welds with hardness up to 260 may be accepted and above
> this number must be PWHT again?
>
> 3. What effects can it cause after taking these weld joints in
> service? Weld failure can occur immediately or would take some time?
>
> 4. As HAZ area hardness number is standing in the range of 115 - 150,
> would repeating PWHT effect this number and further reduce the
> hardness of HAZ which may not be acceptable?
>
> Your inputs would definitely help me in making a correct decision.
>
> Regards,
>
> Ashfaq
>
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