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N990 Close Coupled Bronze Rotary Gear Pumps
Oberdorfer Bronze gear pump. Close coupled bronze rotary gear
pumps. Available as pump end only PEO or coupled to a NEMA standard
Pump housings and gears are made of top quality bronze, shafts
are from stainless steel 303. Bearings are designed of high
performance carbon-graphite material selected for wear resistance
and long service life.
Gear pumps are positive displacement pumps. Each shaft
revolution displaces a definite amount of liquid relatively
unaffected by the back pressure in the discharge line. Shaft speed
and flow are directly proportional. Recommended pressure limits are
100 psi for water and non-lubricants, 150 psi for oil and
Maximum shaft speed is 1750 rpm.
A relief valve is necessary in the system if the discharge line
contains any throttling devices, such as a shut-off valve, a spray
nozzle or other restrictive device. This will return the liquid to
the suction side or to the tank. The relief valve is also available
as part of the pump itself (R-model pumps). However, built-in
relief valves are only good for intermittent service. If used
continuously, the pump will over heat. A built-in relief valve is
strictly a safety device against overpressure. It will not work
successfully as a pressure or flow control device. For this purpose
a separate relief valve in the pressure line must be used.
Service life will be increase substantially if the liquid
pumped is clean and has a lubricity value. These pumps have
extremely close tolerances. Fine abrasives like sand, silt, or
powder in suspension will destroy pumping ability.
Liquids compatible with bronze, stainless steel and the
graphite bushing can be pumped. Solvent resistant packings and
Teflon® packings are also available.
Temperature extremes are detrimental to service life and should
be avoided. Basic metals of construction allow temperature range of
40F to 400F. The acrylic graphite packing is rated to 500F.
Freezing liquid in the pump can deform or damage the pump.
Viscous liquids such as molasses or oils require a lower
pumping speed, in extreme cases as low ass 200 R.P.M. Liquids with
specific gravities heavier than wate such as dry cleaning fluids
require an increase in motor horsepower directly proportional to
the increase in specific gravity over water.
A rotary gear pump is capable of lifting water on the suction
side as high as 20 feet. Though gear pumps are self-priming, a foot
valve is recommended. For pumping water directly from streams or
ponds, a wire mesh strainer must be used at the beginning of the
suction line to prevent stones from entering the pump. Strainer and
foot valve are commercially available as combination units.