Ok let me explain the full story..sorry, I should have done this from the start..the decision was made based on Engineering review that we should fit larger impellers on our Pumps. (6 single stage vertical turbine pumps rated at 8287 usgpm @ 191 feet of head)The larger impellers were supposed to give us 10,000usgpm @ 191 feet of head at around 595 BHP. We supplied the manufacturer with the pump's wet end (column pipes, suction bowl and strainer all assembled together). Manufacturer claimed that due to poor condition of bowl, pump was requiring more than 600 BHP to produce the flow we wanted. (Motors are rated at 600HP). We were able to get 9,730 usgpm @ 599 BHP. So, we settled for that, however, when we installed the pumps, we found that we had to close down on the discharge valve far too much to keep the power within 600hp and this is turn was causing too much recirculation and damaging the pump's bearings. Now, we are forced, in an attempt to save the motors and bearings, to trim the impellers. The manufacturer recommended a trim from 16.614 inches down to 16.417 inches to safely operate within the 600 horsepower limit. So this is why I would like to know what are the procedures in performing this trim and also, an associate told me that instead of trimming the impellers' O.D., you can actually leave it and trim the vanes of the impeller. I haven't spoken to manufacturer about that yet but I'm not really certain if that's adviseable as won't this affect the pump's flow passages? And won't you also have to trim the corresponding vanes on the diffuser as well?...Ok well that's the full story.
Thanks Again!!