rajm008,
Agree with Artisi and bimr.
Each kind of pump has standard performance curve with standard impeller diameter.And also has others non standard curves with non standard impellers(e.g.open,semi-open,closed,different diameter/flow channel).Forget your Max/Min diameter things,choose the standard impeller for each size pump.And you could find tolerance of the impeller as per established standard.
Ul pumps can only have closed impellers. So if i go for the tolernce will i get a range of pumps ? Becauase tolerance of impeller will give the same output as the rated one right? I need to get a range of pump outputs
rajm008,
Why do you keep fixating on "tolerance" ? +/- 1mm dimension is ok for your impeller tolerance.
You need a range of pump outputs ? Just test the standard impeller with changed flow rate/head/speed/NPSH.Then you will get the curve you need.
I'm not familiar with UL testing requirements, but one way to get a range of impeller sizes approved would be to start testing with the maximum impeller size the casing will accept, and then remove the impeller and trim it to the smallest acceptable diameter for that casing size and repeat the testing. I would think that having a impeller in the middle of the size range, and then applying the affinity laws to determine an acceptable range for certification would also be acceptable, but that would need to be confirmed with the testing authority.
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.)