Gearpump Suction Side Question
Gearpump Suction Side Question
(OP)
Hello all. I've browsed these forums before, never posted until now.
My question is concerning the suction port of external gear pumps. On most, I notice there is a certain degree cut out of the gear wall,lets say 3/4" for a 3/8-1/2" port, thats typically equal on the pressure side and suction side.
Typically the gear tooth makes contact at almost 6 o'clock on the suction, and a tad after 12 o'clock on the pressure.(looking at the left cog) I'm curious how much the amount of wall contact influences the pressure capabilities or other characteristics of the gear? Attatched is an example. I am asking if the left gear will be as powerful and effecient as the left gear? Or does each tooth sealing against the wall surface provide an extra amount of pressure holding power? And before you wonder, yes there is a reason I want to be able to port gears this way!
Sorry for such an immature question. I'm no fluid expert! Any help or insight is greatly appreciated.
My question is concerning the suction port of external gear pumps. On most, I notice there is a certain degree cut out of the gear wall,lets say 3/4" for a 3/8-1/2" port, thats typically equal on the pressure side and suction side.
Typically the gear tooth makes contact at almost 6 o'clock on the suction, and a tad after 12 o'clock on the pressure.(looking at the left cog) I'm curious how much the amount of wall contact influences the pressure capabilities or other characteristics of the gear? Attatched is an example. I am asking if the left gear will be as powerful and effecient as the left gear? Or does each tooth sealing against the wall surface provide an extra amount of pressure holding power? And before you wonder, yes there is a reason I want to be able to port gears this way!
Sorry for such an immature question. I'm no fluid expert! Any help or insight is greatly appreciated.





RE: Gearpump Suction Side Question
Another leakage path comprises the clearance between tooth faces in the central mesh; there is just one such path, but its geometry is constantly changing.
Wait, it gets worse; in parallel with all of that is the clearance between the planar faces of the gears and the planar faces of the housing end caps, i.e. two capillary slots whose major planes are parallel to the paper.
So, you can probably port the gear housings as you describe, but you shouldn't be expecting miracles, and you may not even be able to measure the difference it makes.
Mike Halloran
Pembroke Pines, FL, USA
RE: Gearpump Suction Side Question
Tooth tip clearance and end face clearance both play a role in controlling leakage.
Ted
RE: Gearpump Suction Side Question
What we're wanting to accomplish is: having a gear identical or very similar to the left gear in performance characteristics,but to be able to put large,increasing amounts of pressure on the reservoir, without the oil working against the gear. ie: putting 400psi on the oil tank will have the oil pushing against the gear in both directions.I think would push the gear backwards with no load on the pressure side.. If this gives anyone any ideas, don't hold back!
Would just like to have some insight before calling up a manufacturer.
RE: Gearpump Suction Side Question
Use the common pump configuration. No sense in reinventing the wheel. This will then not require a special pump with your proposed inlet configuration.
Be aware the pump shaft seal must be able to withstand whatever pressure is on the inlet port in either case. Up to your tank pressure of 400psi. Most pumps have a low pressure shaft seal, 50psi or less, unless you specifically request higher pressure capacity seal.
Ted
RE: Gearpump Suction Side Question
In a working system, the pressure works against the gear. The pressure in the tank isnt whats desired, its a bi-product of somthing else. But yes we do need a certain amount of pressure to get rid of the suction and cavitation problems. We are already useing an accumulator on the resevoir,but the pressure still works against the gear over 50psi. There is no pressure leakage, you physically hear the motors bog. We are turning the gear at speeds in excess of 10,000 rpm, at 6-8 cubic cm/revolution, with several thousand pounds of load. With the pump running, as soon as the pressure is put on the return tank, the gear slows CONSIDERABLY.
RE: Gearpump Suction Side Question
A system schematic would be helpful at this pont.
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Ted