dummy leg weld intersection

Date 08-01-2007 09:15

Hello,

What standards are you working too would be the first question. I think that will be very important to get a clear answer here.
Second question is what does the engineer think about it? If its for a standoff support in general it would probably not be a problem. BUT that of course depends on size and type of materials, weight of whats being transfered in said pipe, stability of foundation, is it pressurized in service etc. In other words refer to the second question...what does the engineer on the project want to do. Please provide a bit more detail.

By RANDER

Date 08-01-2007 12:26

I agree with TommyJ,
I dont think you'll find the answer you need in any code (Which one are you using?) or from anyone here. Your best answer and the one that matters most will come from the Engineer or design group in charge of the project.

By engineertwo Date 08-01-2007 13:48

Thankful to Tommy J and Rander for their response.

The code is 31.3 and the line is a pressure steam line. I hasd asked the design group to provide the answer. The company standard requires " pipe shall be in full contact with the support " and " all welds shall be continuous and spot welding is not allowed".

In the case stated in my first message, the main pipe is 14 inches and the dummy leg suport is 8 inches.

I dont see that it is a problem as the support is in full contact with the pipe and welding is also continuous except at circumfrential weld of the 14" pipe(to avoid welding intersection with the pressure contained weld).

Can u please further discuss under this background.

thanks,

By Tommyjoking (****)

Date 08-02-2007 08:35

Well I agree with what was done as in not to allow the support welding to come in contact with the pressure seal weld. I assume because of support spacing design this support inadvertantly ended up directly under a seam.

"My shade tree engineering answer is: The pressure joint has already undergone inspection before the support leg was added..correct? (if not it will have to be removed anyway) Provided the reliefs cut in the support pipe are not say more than 15-20% of the circumference of the support and the rest is fully fillet welded...I doubt it would be a structural issue" However you are expanding the HAZ around that joint beyond its design as well as adding more mechanical stress to the joint. You are very much in the right to stop and question this procedure.

Having said that I think the safest thing to do here is have an engineer in the design team sign off on the change. Its pressurized pipe and there are just too many variables to consider. I do not have access to that code spec so I will not comment on its impact. Again I strongly recommend getting an engineer to buy off this modification or to submit a design change recommendation like allowing supports to be adjusted within a set limit.

Regards
Tommy

By nateprice215 Date 08-02-2007 12:57

Hello:

You mentioned that the code was B31.3, and is it possible that your plant also recognizes API 579?. I would perform a fitness-for-service on this and my guess is that it would come back fine then document it. This does not seem to be a complex analysis from a calculation standpoint.

Regards,
Nate