Gear Pump
A gear pump is a fixed displacement pump that carries oil from suction to discharge in the tooth spaces of two meshing gears. On mobile equipment typical continuous working pressure is 180-250 bar and displacement is in the 4-40 cm3/rev range. Its simple construction makes it tolerant of contamination and inexpensive.
The operating principle is directly volumetric: each revolution sweeps the displacement volume of oil, so flow rate comes out directly proportional to speed. A 20 cm3/rev pump theoretically delivers 30 l/min at 1,500 rpm; since volumetric efficiency is typically 85-95%, actual flow is slightly below that.
- Strength: few parts, low cost, resistance to oil carrying particles.
- Weakness: high noise level, fixed flow; it keeps pumping oil even when no work is being done.
- Wear symptom: movements slowing down at the same speed and oil temperature rising.
Most tractors, truck mounted cranes, and small work machines run with a gear pump and an open center valve. This is the most common arrangement you will meet with AXI's retrofit kits: because flow is fixed, how far the lever is opened directly determines speed, so being able to use the intermediate positions of the joystick is the only way to do precise work.
Where this term is used: What Is a Hydraulic Lever Retrofit Kit? Definition, Components, Operating Principle