Dear All,

While analyzing the saddles for Horizontal vessels, is it a must to add the additional piping loads and moments at the various locations where nozzles are attached.
While using the Force / Moment dialog for Horizontal vessels dialog box for BW, BS, SRSS and Algebraic methods are all frozen. However all these options are made available when the vessel is vertical. Why is the option not available for horizontal vessels?
For Horizontal Vessels in the the Force / Moment dialog it says that Moments should be converted to equivalent forces on Horizontal vessel for support load consideration. Can you please specify by which methods this can be performed? Will Moments acting at the nozzle to shell junction will have any effect on the saddle design?

regards.

Hello Maroof,

The saddle analysis is primarily driven by the weight load on the saddle support. Other important parameters are the distance from the tangent line and the distance between the saddles.

If you have external loads that are substantial and will affect the saddle design, you should enter them in the Force/Moment dialog. Vertical, longitudinal and transverse forces are included in the saddle design. As you noted moments are not available. Unfortunately, the literature and Code specific analysis do not provide a way to perform the moment to force conversion that would be meaningful to the saddle analysis. It should be possible to model the saddle in a structural analysis program like GT STRUDL.

Currently in PV Elite forces and moments applied to nozzles are only used in the local stress calculations (107, 297, Annex G etc.). They will not affect the saddle calculations.

I hope this helps.

Dear Scott,

Many Thanks for your immediate reply.
Agreed that the PV-Elite forces and moments will not affect the saddle calculations.
But in cases where the diameter of the vessel is small and you are having a large opening (more than half), loads due to the piping will have a substantial impact on the saddle design.
In case there is some method for Moment to force conversion, kindly update on the same.

regards,

Maroof

Hello Maroof,

In small vessels, the saddles are so strong that even doing the analysis is really a formality. The stresses are very low however you load them.