I agree. When a VSD is not ...

I agree. When a VSD is not used, the final performance of the coupled pumpset is all you need to measure. Please note that pump performance from a bulk manufacturing process will differ slightly (up or down) and performance will also deteriorate as the mechanical clearances wear. Therefore consider what is your actual requirement and how this can be achieved over time.

If your question is to get a fair tender process and ensure the salespeople are not 'exaggerating the truth', then base penalties upon your most important requirement, as I have done previously with efficiency and whole life energy cost of operation the determining factor.