ASME 31.3 - Skillet Flange for Hydro testing

[BCG1]

The application is to insert a flange skillet temporarily on two ends to hydrostatic test a 24" line. I am using the equation found in ASME 304.5.3 for determing the thickness "t" of Blanks. Namely, equation 15, where t= d(3P/16SE)^.5 + c. I am unable to verify the customers thickness requirements using the given information:

Skillet material = SA-514 GR 100, d = 23 in, t = 1/2 in, E = 1, S = 90,000 psi (90% yield for temporary use), and c = 0. Solving for P, I get 227 psi.

Apparently, they claim that one can test up to 341 psi. I am getting a much lower number and think you will need a thicker plate to reach this test pressure. Is there an exception that I am missing when you are using a skillet for testing only? I don't have API 590 handy, but is there a different equation in there? The goal here is minimizing the spreading distance due to field conditions.

Thanks for your help

 

[deanc]

Well if the clearence is that tight and it bulges how will you get it out?

Think I would go to 1" and use some banana wedges to get it in.

 

[BCG1]

Thank you for your feedback,

I think that your concern is the risk we are trying to minimize. Most cases if it bulges out, you need to cut back on the pipe and weld in a new pup piece, which kills you in cost. My concern is that we may not be able to spread a few of the flanges to get that 1".

Any other thoughts regarding the calculations?

 

[jte]

BCG-

I think you'd find this paper

http://store.asme.org/product.asp?c...apers&category_name=&product_id=PVP2005-71164

interesting. Although it does not address SA-514 steels, you might be able to be a bit more comfortable with the proposed hydro pressures. It's a question of how much the test will dish out the blind. If you can get a 1" blind in (with a 1/8" gasket also) then you can allow a 1/2" blind to deform 5/8" (for a total "thickness" of 1 5/8") during the hydro and still pull it out.

I'm not too sure you're bound by any code on this (check local laws and regulations etc). Components which exist only to support a hydrotest and are removed from the system prior to placing the system into service don't fall into code jurisdiction. As long as they are fit for purpose i.e. they hold the hydro pressure they are acceptable. Just be sure you can pull 'em out if they dish a bit.

Keep us posted as to how this project proceeds. My guess is that if they use 1/2" blinds they will see dishing of less than 1/4".

jt

 

[unclesyd]

One of the forum members zdas04 posted this link in another thread. Look at page 9.

http://www.muleshoe-eng.com/sitebuildercontent/sitebuilderfiles/safetystdstatictest.pdf

 

[BCG1]

Thanks to all for your feedback! I need to run through the calcs that unclesyd led me to, and I have a feeling that is exactly what I am looking for. I will keep you posted on how it pans out

Regards, BCG1