This is the opposite of continuous service. We could be talking about batch operations, standby pumps, level control pumps, etc.
The pump is continually moving off the best efficiency point (BEP) during the start up procedure.
Break away friction of the seal dynamic elastomer and lapped faces contributes to the problem.
The thrusting of the shaft at start up can cause seal problems.
Build a film on sliding seal components.
We experience shaft axial movement and volute radial movement as the pump comes up to operating temperature.
The frequent heating up and cooling down of the bearing case can cause bearing problems because of moisture condensation and aspiration.
Batch operations sometimes require a flushing of the lines and pump to clean out the old pumpage. The cleaners and solvents used for this cleaning can sometimes affect one or more of the seal components.