What is the rule for adding a reinforced pad when specify a pipe shoe

[babyfatface]

What is the rule for adding a reinforced pad when specify a pipe shoe?
Project requires 6” above using reinforced pad same thickness as pipe . I would like to know the reason behind that.

 

[JohnBreen]

There is no "rule". Some company standards call for re-pads for "T" shoes and/or trunnion supports. Most company standards are based upon experience, i.e., lessons learned. You will sometimes hear these pads referred to as "doubler plates".

The only rational reason would be to offset the effect of punching shear on the pipe wall if the pipe load is heavy and the pipe wall is thin enough to feel the effect (the "pad" spreads the load over a larger area). On the other hand you have to be careful with welding appurtances to pipe walls if the pipe is hot as in some cases it can cause non-trivial temperature gradients and the associated stresses.

Regards, John

 

[STYMIEDPIPER]

There are a few other reasons depending on the application.
1. Depending on the client and /or Code requirements the piping spools may be required to be pressure tested in the fabrication shop. In this case, welding to the pipe spool after testing is not permissible without additional cost/time to retest. Hence, if a doubler plate was welded to pipe spool during fabrication prior to testing , a support can be attached via welding to the doubler without creating any retest concerns.
2. Also, a slightly oversized doubler plate provides a little flexibility at the site to field attach a support to line up with embedded studs, steel, walls, etc.
3. Doubler plates are highly recommended on tanks when piping is routed up/down sidewall and pipe supports are necessary to be attached to tank wall.

 

[babyfatface]

Thanks both for your valuable input.
I did not see any pertinent requirement in B31.3 and I am not so sure if there is other manufacture code that may cover this aspect. If so ,please inform here.