Most of the problems you will encounter are associated with temperature of the liquid rather than the flow rate. Non soluble powders can cause vane wear. Because the discharge is at the center of the pump, heavy particles are forced away from the discharge ports by centrifugal force and collect at the periphery. If a steady flow of liquid enters the pump it will not cause damage, but the power requirement will increase. Many manufacturers recommend installing a separating chamber or trap to prevent a solid liquid stream from entering the pump.
Most manufacturers encourage the return of the pump for any repairs.
This means that you will need a supply of spare pumps in your inventory. The sealing liquid flow rate is critical for the pump's performance. Too little is as bad as too much. The manufacturer has a recommended flow rate, so try to follow it. To get a better vacuum you need either a booster pump, sealing liquid with a lower vapor pressure, or an added heat exchanger.