I made a jet/venturi pump from a 2" T ,1" discharge and 1/2" air inlet through a 1/8 nozzle,air at 120psi. Suction is 2" pipe about 5' long. Problem is that I'm only getting about 3gpm. Would decreasing the diameter of the suction allow for better flow? Or would I do better increasing the diameter of the discharge? Would steam @ 100 psi give better rate? Trying to give a hand to our sump pumps at work(poultry plant) which keep clogging up and burning out.Results in a flooded boiler room On the other hand the air lift I made works quite well.

Using the internal standard I work to and assuming the following:Boiler Feed Water13/4 Chrome

impellersDesign Temperature 248 deg FImpeller suction specific speed < 9300 US unitsNPSHr :    30ftOperation between 80 and 110% of BEP40,000 hour impeller life requiredThe NPSH margin for these circumstances is 1.88If you don't want a 40,000 hour impeller life it is 1.57Sorry I can't publish the whole standard.  But if you give me details of the duty conditions I can suggest what NPSH margin I would recommend.Typically you see rarely see margins for critical BFW pumps of less than 1.5
I agree the old HI standard wasn't a thing of beauty either.The problem I think we would both agree on is the issue of experience that you mentioned in Vacuum pump one of your posts.On a recent tour of engineering contractors in Europe I was struck by how young many of them were.  The majority looked like they had come straight out of university and taken up residence there.Now I admit this might be my prejudice or my increasing years (or both).  So I apologize in advance to the experienced engineering contractors.Unfortunately experience takes time and being given the chance to break a few things.  These days everyone seems to be in too much a hurry for that.

2011-08-15

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