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Trunions

Trunions

Trunions

(OP)
I need to install Trunion supports on a 36" sch. 40 vertical run of about 100'. What size should be used on the trunions. Thanks in advance

RE: Trunions

A trunion is an attachment of pipe or tube steel welded to the run pipe. Welding Research Council Bulletine 107 (I do not have a copy) outlines the requirements for evaluating these attachments.

Trunions produce local stresses on the run pipe that need to be evaluated. The WRC formulas consider radial force and circumfrential and longitudinal moments.

While the design of the trunion and the welds are relatively simple (use beam theory), it is importnant not to overstress the run pipe due to this type of attachment.

RE: Trunions

Hood1,

From the description, it looks like you are looking at using a pair of trunnions coming horizontally off the sides of the riser for support.  For that kind of application in a line that big, I'd consider using a lug type of arrangement that you see used on vertical exchangers.  With that orientation, the main load will be the longitudinal bending in the header and I think it would be easier/cheaper to size the gusset plates to be as long as you need to get a good section modulus and distribute the load.  

And, I'd highly recommend consulting with an engineering company and get a pipe stress or vessel engineer to do this for you.  The nature of your questions suggests that this kind of design work is not your normal function.

Edward L. Klein
Pipe Stress Engineer
Houston, Texas

All opinions expressed here are my own and not my company's.

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