Pressure Differential and Gear Pumps

It depends on a head/pressure analysis on your piping systems including elevations and lengths.

Please see here for a little insight:

http://www.goulds.com/pdf/CINTRO3.pdf

And this site: (it also has a free book - for centrifugal pumps, but pretty relative for your needs)

http://www.lightmypump.com/

rocles -- you'll need to know how long the 2" piping is and what fittings are present. You will also need to know the viscosity of the liquid being pumped. Gear pumps do not hold up well at viscosities below about 75 SSU unless the pressures are fairly low 20-30 psi or lower. The reason for this is that the bushings that carry the pressure loads that act directly on the gears are normally lubricated by the liquid being pumped.

The Goulds info is pretty good for centrifugal pumps. That's their business and they have almost a century of being very good at it. But if you are dealing with a viscous liquid then you may get led astray by what you encounter there. Yes centrifugal pumps can be used on liquids of moderate viscosity at substantial efficiency loss but you may have to dig deep for the correction factors and they will be all wrong for gear pumps anyway when you find them.

If you have trouble with the pipe friction calculations come back here and say so. I have old Worthington Pump price book charts for estimating pressure drops at various viscosities as well as the equivalent length corrections for pipe fittings at high viscosities. It'll take some digging to find a published or online source of this info; but I suspect it's there somewhere. Possibly in the McGraw-Hill Pump Handbook, that was edited by 4 guys from Worthington Pump.

Ed Weldon

A gear pump is a positive displacement pump, and has theoretical infinite pressure capability (less the leakage past machining tolerances). So consider the pressure differential limited by the type of pump construction such as housing thickness (maximum pressure rating) and shaft power (before it torsionally breaks). Just imagine running the pump against a blocked discharge at the very end of your piping run. What will fail due to overpressure ? Then put overpressure reliefs in place to protect all those items. The pump itself will likely have an internal relief valve to protect the casing and shaft from overpressure damage.