PWHT OF JOINTS

[mikaeel]

Hey what's up.I would like to find out if it is possible to PWHT 2-24" butt welds 1" thick and produce a graph without any deviations i.e. from start to soak to cool down and all the tc wires that were recorded were one on top of the other.thanks

 

[GRoberts]

Yes, it is. Try Cooper Heat MQS. They use resistance heating pads and can either sell you the equipment, or provide the service for you. Miller (the same one makes welding machines) also makes PWHT equipment using induction. It is faster, but not as flexible, so know what applications you currently have, and may soon have to determine if it would meet your needs.

 

[mikaeel]

yes thanks for the info but what I'm really asking is if you can PWHT 2-24", 1" thick butt welds and receive a perfectly plotted graph because this was done for me and people are sayiny that the tc wires were jumpered although looking at the joints it was completely burnt.

 

[GRoberts]

Are you asking if a 1" thick butt joint on two 24" wide plate (or are you talking about pipe) can be post weld heat treated in such a way as to produce a heat treat record that has no deviations from the perscribed PWHT procedure? If this is what you are asking, I would say that it is definately obtainable with a skilled operator and the right equipment. I'm not sure how jumping TC wires would produce an adequate heat treat record or what you mean by joint was completely burnt. Please elaborate if you need more info.

 

[mikaeel]

Thanks Mr. Roberts for the reply. The joints in question are 2-24" butt welds (pipe).What happened exactly is that when the cycle was started both welds were taken up to 550 degrees and then the chart was put to start printing.Therefore when you look at the chart from the beginning all you see is one straight line from start to soak to finish.When the chart reached the finish point at about 550 degrees the recorder/printer was shut off.Now all of this is within our specs but the client claims that a perfect graph is imposible and even went further to say that the chart looked as if someone drew it.I hope that this clears up what I am asking and if I can get some proof via a web site or book that this is possible.thanks

 

[Weldmedic]

Mikaeel,

The answer to your question is yes, you can come up with a very uniform chart. I have seen quite a few in this manner.
1) How close in proximity were these joints?
2) Were they pipe to pipe or were there differences such as a weld to a valve (more mass)?
3)Location and environmental conditions or Inside? Lots of variables come into play with PWHT. If you havent been involved in the field I suggest froming a close association with the PWHT Techs in the future. Look listen and ask lots of questions. This experience will serve you well...
From a personal standpoint, I have seen quite a few charts which were excellent runs. Ive also seen them run all over the page(stuck contactor, Bad UDC, or just a inattentive tech doing a dialup. Was this an Automatic runlike a Coopermaster or PC controlled or was this one run by hand? Unless there is some specific reason to question this PWHT I would offer to Brinnell test the weld and HAZ (at customer expense of course). I dont however understand why you wait so long before you start the recorder (chart paper is cheap)and the run up will allow you to evaluate how things are going. There should be TC# printed along the chart
4)BTW how many TC were on these joints and were the welds in the vertical axis or horizontal axis.(Inquiring minds like mine want to know)
A final note and Ill stop rambling for the meantime... As far as the charts go it helps for a field inspector to initial the chart in the field during the run to help establish that the chart turned in is the real Mccoy. Good luck, write back if you need any other questions.

Steve

 

[mikaeel]

Hey steve thanks for the info.Right now we are in the process of completing the hardness test and the results are quite ok.The client is very difficult to please and complain just about everything.So the bottom line is that we are just waiting to see the outcome of the tests and hopefully we wouldnot have to re-PWHT yhe joints again.