It is essential to take a view of the complete pump system. As detailed in ASME EA2 the fundamental starting point of any assessment is to understand the requirements of the system, what is the function of the system and what is the output performance?
Benefit can be gained from performance testing of pump sets, but unless the complete system is considered partial or inappropriate, conclusions can be reached resulting in costly exercises that do not offer the best returns in energy saving and resulting CO2e reduction. Recirculation through control valves and non-return valves can often be overlooked. Subsequent pump overhaul or upgrade can actually increase the system losses.
Oversized pumps can sometimes be improved by using variable speed drives (VSD) but an investigation is required into the system characteristics to determine how suitable this option may be. In high static head conditions, VSD may not be appropriate.