What is a solenoid pump?

A part of a solenoid consists of a wire-wound static coil and a movable plunger.

A solenoid pump is a fluid transfer device that makes use of the reciprocating motion of an electromagnetic solenoid plunger to transport fluid through a sealed suction chamber. These pumps take advantage of the motion provided by a solenoid coupled with the positive displacement characteristics of a diaphragm or piston to move fluid and are generally used where accurate, low-volume pumping is required. The mechanism usually consists of a conventional solenoid coil with a plunger connected to a diaphragm or piston. When energized, the electromagnetic field that is created around the coil attracts the plunger, feeding one phase of the cycle with a spring that returns the plunger when the coil is de-energized, thus providing the second phase. This functionality relies on a pulsed power supply that cycles the coil on and off and is typically provided by a separate controller.

There are two distinct mechanisms that make up the middle solenoid pump. The first is a solenoid consisting of a wire-wound static coil and a movable plunger. This part of the device works in the same way as most solenoids in other applications and depends on the magnetic field created around the coil when an electric current passes through it. This magnetic field acts on the ferrous metal plunger moving it rapidly towards the coil. When the electricity supply to the coil is cut off, a spring pulls the plunger back to its idle or neutral position.

The second part of the solenoid pump is a positive displacement pump mechanism. Positive displacement refers to the mechanism that moves the fluid through its internal space, displacing it through the action of an alternate element. Generally, in a solenoid pump, this element is a piston or diaphragm and is alternated or moved back and forth continuously. Motion is provided courtesy of the solenoid plunger which is connected to the piston or diaphragm.

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The reciprocal action of the solenoid pump is achieved by pulsing or alternately turning the solenoid power supply on and off. This causes the plunger to move first in one direction when the magnetic field attracts it and then in the other direction when the spring returns it to idle. Of course, this action is then repeated by the piston or diaphragm. Pulsed power to the solenoid is usually provided by a separate controller, which can be used to control the speed – and therefore the output – of the pump. The solenoid pump is capable of high levels of accuracy and is often used in chemical metering and precision fuel delivery applications.

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