Equipment reliability - Pump wear

When we are faced with the prospect of installing a new pump, we have to take a look at several factors to decide what the best course of action will be. For example, we have to look at:
– Fit for purpose
– Initial cost
– Life-cycle maintenance costs
– Electrical efficiency
– Ease of maintenance
– etc.

An additional consideration is how the characteristics of the pump vary over time.  It is fairly straight forward to calculate flow rates and pressures using the specs of a new pump.  However, how do these specs vary over time?  As the pump wears, how will the characteristics of the pump change, and how will this affect the overall fitness of the pump for the service environment?

Here is a nice article that describes how pump nameplate characteristics will change as the pump wears, and what to expect as the components wear.