Most of the time, when we have multiple items of rotating equipment, getting the stresses and loads within compliance during the run/standby cases is among the most difficult things we do. This is because we usually don't put enough space between the equipment items to allow us to put in a lot of flexibility between the header and each individual piece of equipment.

A usual "fix" is to start backing the headers away from the equipment until the individual connections become sufficiently long that you can design in enough flexibility to reduce your loads. Your rotating equipment guys will love you, but the process people responsible for head loss calculations will probably put a price on your head.