External piping load global impact on pressure vessel ASEM VIII Div. 1

[abehong]

Hello:

I need to clarify one thing with some experienced engineer which is not clear for me for long time. The impact of external piping load on vessel and its support from global point of view. Normal engineer practice is to conduct local stress analysis due to the impact of external nozzle load ( 3 forces and 3 moments ) using WRC 107 or FEA method. As per UG-22, it only requires to consider the superimposed static reactions from weight of attached equipment or piping ( not mentioned load because of thermal expansion). However, it requires to consider the load for vessel support design due to externally applied piping moment and forces as per Appendix G . As per the explanation regarding local loads in Pressure Vessel Design Manual, by Moss , the corresponding stressed due to local load are confined to a small portion of the vessel and normally fall off rapidly in distance from the applied load. So my interpretation is that it should do local stress checking due to external piping load , but does not need to consider the stress impact on the whole vessel from the global stress point of view. However, it shall consider the applied external piping load (force and moment) for vessel support design.

Thank for your consideration

Abraham

 

[gr2vessels]

The external nozzle loads affect the vessel in two ways;- one is the local stressing of the junction of nozzle to vessel, but there is an overall impact on entire vessel. It's a good idea to evaluate the global effect on the supports and the foundation, particularly for tall vessels or long horizontal shells. You'll be surprised to find that the global effects would require stronger supports and additional foundation strength. Sometimes it require additional thickness on the shell also.
As an equipment designer, you are suppose to evaluate if the effect is negligible or not. It's not much comfort that the shell remained intact after the vessel fall over as consequence of a weak support.
Cheers,
gr2vessels