The main purpose of an oil pump is to create pressure that allows oil pumping in the desired direction.
Depending on the type of control there are adjustable and non-adjustable oil pumps. The main difference is that in the devices of the first type maintenance of constant pressure is provided by adjusting productivity, and in the second type devices by a pressure reducing valve.
Gear pumps and rotary pumps are most commonly used in the industry. They got their names due to their design.
Structurally, a gear pump consists of two gears placed in one housing. One of them is the driving gear, and the second one is the slave gear. Oil flows through a suction passage and then is captured by the gears and pumped into the system through a special channel. To calculate gear pump productivity, you need to know its crankshaft speed. These two values are in direct proportion. If oil pressure exceeds a certain threshold value, then there a relief valve, and part of the oil is passed into the suction chamber.
Rotary oil pumps consist of two rotors: a male rotor and a female rotor, placed in one housing. First, oil is pulled into the pump, and then it is captured by rotor blades and pumped into the system. As with the gear pump, a pressure reducing valve provides protection from overpressure. This design is peculiar to unregulated rotary pumps.
Adjustable rotor oil pumps have a more advanced design. They have the obvious advantage of being able to provide constant pressure throughout the crankshaft speed range. Technically, pressure control function is provided by changing the cavity volume between the mail rotor and the female rotor when the stator is rotated.
The usage of adjustable pumps allows reducing power consumption and the amount of expendable oil and its deterioration.
Adjustable rotary pump operates as follows. Increasing of crankshaft speed results in a pressure drop in the system and increases the demand for new oil. This pressure drop results in a shifting of the stator by an adjusting spring. The position of the female rotor also changes. As a result, the volume of the suction chamber increases, thus increasing productivity.
If the crankshaft speed is reduced, oil consumption is also reduced, and the pressure in the system increases. The increased pressure compresses the adjusting spring, which changes the position of the stator which makes the rotor move. This reduces the amount of sucked fluid and the pump performance is reduced.
Oil pumps are widely used in different equipment. Particularly, in GlobeCore plants designed for processing of various types of oil.