ASME VIII Div. II 2007 PWHT

Date 08-13-2011 17:22

Dear All
I have been confused about statement in Par. 6.4.4 (b) ".....in no case need it be less than 56°C/hr (100°F/hr)"
I my interpretation that statement is just optional or not as strong as "shall be"....So the minimum heat rate is not necessary for PWHT.

Is any one have another argument about this... Thanks before.

Best Regards

By jon20013 (*****)

Date 08-14-2011 03:51

It is optional, one could cool at a rate less than 56°C/hr (100°F/hr) but why???

By maxilimiano (**)

Date 08-14-2011 04:11

Mr.Jon,

Because that PWHT equipment is not enough to reach heating rate. Maximum rate only 20 C/hr...so linear rate start from 30 C untill holding time.

I thought, that's wrong, because of grain growth metallurgical effect..but that was allowed by ASME VIII-2... :confused:

regards

By js55

Date 08-15-2011 12:56

You're not going to see grain growth at those temps but depending upon material you might experience PWHT cracking if J-Factor elements are not controlled. Its been awhile since I've refreshed my memory on this stuff but shootin from the hip it looks like you will be spending 10 to 20 hours in the sensitive range upon heating. And if memory serves though J-Factor is normally considered an issue for service related temper embrittlment I believe the consensus right now is it is related to PWHT cracking as well. The J-factor elements have a time related segregation to grain boundaries and I believe your PWHT time frame is within that range.

By maxilimiano (**)

Date 08-22-2011 00:23

Yup, I thought you,re right..Metallography examination shall be used for judgement if we need higher confidence level.

In API RP 582, we can use Hardness Test "12.6.2.5 Unless otherwise agreed between the manufacturer
and purchaser, the maximum allowable hardness for welds shall be:
a. P-1, P-3, and P-4 material-225 Brinell ".

Another problems are NDE after PWHT,I have never found about MPI after PWHT in ASME VIII div.2...but I always find it on actual...And in ASME VII-2, i just find statement "EXTENT RADIOGRAPHY"...(Table 7.2)..ha..ha..

In my experience, we use MPI 100% if the electrical is shutdown in the middle of PWHT..