vessel nozzle loading 5

[heaterguy]

If a customer gives Fx-500 pounds, Fx-500 pounds, Fz-500 pounds, Mx-1,500 foot-pounds, My-1,500 foot-pounds, and Mz-1,500 foot-pounds, do we apply all six forces at once, one at a time or just F or M forces?

"Each vessel nozzle shall be designed for the following loads"

 

[RossABQ]

I am a piping design guy, and also write or provide spec input to some of the plant owners who have this kind of language on nozzle loads in their specs. The client's intent in most of the specs is really to avoid a nozzle that is acceptable for pressure but won't take even incidental loading from the attached piping during erection or maintenance. (The example cited sounds like a blanket load that should not be applied to a small nozzle) Contractors are notorious for hanging pipe (even large stuff) with #9 wire or nylon straps while they set the permanent supports. They need to be attached to a nozzle at this point to set the piping. Even when permanently supported, adjustment of the hangers to achieve the (piping) design intent is a crap-shoot.

Most of these same clients also have it in their hanger/support specs for us (the piping designers) that external piping shall not impose "any" loads on the equipment nozzles in "any" thermal or operational condition!

 

[4Pipes]

Going back to the original post, I would fully agree that the nozzle loads are definitely not right. On a general point, it is one of the few times I have seen such a situation.
The normal situation is for vessel vendor to design his shell on PD/2t and ignore nozzle loads even if they are specified. He buys his material, presents his drawings and gets them knocked back on client review. A

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but I've cut the plate - it will take 6 months to reorder...... The problem is then smartly put onto the purchaser to accept loads for a vessel that is only of use in zero gravity. Even when local loads are taken into account at the nozzle, there is the small matter of getting the net affect of the pipe loads, eccentric platform loads, seismic loads of attached mass etc to the holding down bolts and through all parts between. I came across a newly installed vessel where the desigm overturning moment was one third of the total calculated taking all loads and inertias into account. Unusal only by scale. No prizes for guessing which load was used for the HD bolts and civil design.

Vessels don't fall over very often so its only a real problem if you have to prove it. However, even that is never a problem - in my 30 years insurers and public inspectors only ever look at what they paid to look at - never the big picture.