pump acceptable grades

[mech212]

I was reading in ansi hi standards for pumps and there is a table called pump test acceptable grades , what i understand is that if we have a specific design of a pump say head of 10 bar at rated flow ,, so when the tests are made and due to fluctuations and vibrations , the readings foe example of the head must be say +-10% from the 10 bar according to certain grade ,, is this right ? also how can we choose the right grade?

 

[Artisi]

Correct, usually higher the grade higher the price. 10%+- would be standard test for off-the-shelf production pumps. Tighter tolerances would need rework, like impeller polish and attention to all wetted parts, greater accuracy with testing and measuring equipment etc.
You choose the test grade based on the performance accuracy you consider is required for your application.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)