Dear Jop,
I appreciate your reply, My purpose is to write worst load case, for threes pumps, 1 pump is in operating another 2 pumps are stand by or 2 pumps operating and 1pump is stand-by. To know how to write load case as per above logic.

Assume:
Tank=Lxh = 24'x17'
horizontal raw water pump: suction=10" disch=8"
suction=10"
discharge=8"
Design Press=100bar
Design temp 150 F
if you see closly above pic, you find trunnion support at discharge line at elblow.

As per site condition I am checking all your consideration as you said above, you need to ask,have you considering force/displacement/Wind load/friction/hanger etc. to write load case, I don't have force/displacement/hanger etc. Reply me your load case logic I will check what worst effect is projecting out from the current routing then we do changes.

* from above pic its understood that suction is side and discharge is top.