Requirement of PWHT

[sakib321]

Dear All,


we want to weld the tube with tube sheet( by using ER-70s3
my question is that is there any requirement of heat treatment for it ?

the detail are as under

MAterial of Tube A 334 Gr 1 with thickness 2mm

MAterial of tube sheet with A 350 LF1 thickness 80mm

Construction Code ASME VIII Div i


for service condition see the snap attach(Detail Drawing can be download from http://www.megaupload.com/?d=APVZYX48 )

Apart from this what precaution we should take during welding. As i think so there will be chances of Cracking due to croygenic condition.


please comments

[ashfaqanwer]

Both the materials you have mentioned fall in P.No. 1 and Group No. 1 as per ASME Sec. IX.
For PWHT requirements as per code, refer to UCS-56 Note (2)(c)(2) in ASME Sec. VIII Div. 1, it has been mentioned that PWHT is not mandatory for the tube to tubesheet joints with groove welds not over 19 mm or fillet welds with throat thickness less than 19 mm. But the exception of UW-2 has been mentioned.

And in your case due to handling of lethal service, ammonia, as per UW-2, it is recommended that you must perform post weld heat treatment of tube-to-tubesheet weld joints no matter what the thicknesses and the P.No.s / Group Nos. are. See UW-2 for more details.

If you want to seek any clarifications, please do not hesitate.

[sakib321]

thanks a lot its helpful

[arcpro]

We have 05 exchangers handling ammonia with tube and tubesheet materials belonging to P.No. 1 and G.No. 2 welded with ER70S-3.
For all the cases, tube-to-tubesheet joints have been post weld heat treated.

[sakib321]

actually i had never seen the PWHT of tube to tube sheet joint
is any one have detailed step for it ??
then kindly share

[ashfaqanwer]

Hello Sakib,
I have just seen the detailed drawing due to slow internet connection.
The type of tube-to-tubesheet joint in your case is a seal welded and expanded without grooves.
I am sure about the requirement of post weld heat treatment for a strength weld (with groove in addition to fillet) due to lethal service but I am slightly in a doubt for seal welds. I will see if I can find any reference.
Meanwhile, you may go through the following thread which you may find interesting:
http://www.thepetrostreet.com/forums/vi ... ?f=14&t=67

I could not understand your last post. Do you require PWHT procedure for tube-to-tubesheet joint?

[mechcolor]

I would like to add my bit of advise.
"As per code ASME Sec. VIII there is no requirement of PWHT on tube-to-tubesheet weld joints of P.No.1 materials. Additionally, seal welding with 2.5 mm leg fillet would not be causing any metallurgical changes to the tube or tubesheet material which may ask for PWHT. Now coming to the lethal service, yes PWHT is recommended for all thickness welds as per UW-2."

In short, if the weld was post weld heat treated at the time of manufacturing then you may do that and I would recommend to seek advise from OEM.

[ben]

UW-2 rules over UCS-56 and PWHT is mandatory to handle lethal service. So if you have to comply with the code requirements, you have to conduct PWHT.
Executing PWHT would be a job to do. It's easy to do in shops but in field it's never easy. How many seal welds have to be made?