PWHT of .337" M.W SA217 C5 ( P5B ) 2

[JIPMKWA]

Hello,

We have a 4" SCH. 80 ( .337" M.W ) SA217 C5 Valve that we are going to weld to a piece of 4" 335 - P22. So it's a P5B to P5A weld. Our procedure calls for a minimum of 2 HOUR soak time on P5B Material - to give all of the martensite time to temper.

** My question is the ramp up time since it is so thin. I know B31.1 has a heating and cooling rate where as Section I simply says to bring it up "slowly "

0 - 600 no limit and then Above 600, heating and cooling shall not exceed 600/hour divided by one half the maximum thickness of material in inches at the weld.

So we'll say we have an 1/8" weld crown that would put at us at .337 + .125 = .462 divided by .5 = .231 ( approx. 1/4" ). So 1/4 of 600 degrees is about 150 degrees per hour ? Looking at around 4 1/2 hours to go from 600 degrees to 1300( our PWHT target temperature). Is this correct.



Thank you for your time

 

[metengr]

No. First, you do not include weld reinforcement for thickness in PWHT. You use the surrounding base material thickness in the weld region, which controls the rate of cooling.

Second, using B31.1, the rate shall be no greater than 600 deg F/hr or 600 deg F/ 1/2 the thickness. In your case, the 600 deg F/ .5 x .337 > 600 deg F/ hr. Therefore, you are bound by 600 deg F/hr rate for this thickness.

The time for PWHT is based on Table 132 in B31.1 where the time is 1 hr/inch of thickness. Under 2", this applies resulting in a time of 1 hr/inch * .337" = 1/2 hour at PWHT temperature.

 

[JIPMKWA]

So in my case it works out to 3,540 degrees per hour but the max is 600 degrees per hour.


As far as ASME Sec. 1 is concerned, what does "slowly" mean to you ? Should you just go with B31.1's requirements ?

Thanks again.

 

[metengr]

I worked on the revision in Section I 2010 which introduced the cooling rate for material over 2" in thickness in
Appendix A. Under 2" thickness, either 400-600 deg F/hr heat-up or cool down rate is slow enough to avoid thermal stresses which can result in distortion or cracking.