What Is a Solenoid Pump?

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 make use of the motion supplied by a solenoid coupled to the positive displacement characteristics of a diaphragm or piston to move the fluid, and they generally are used where low-volume, accurate pumping is required. The mechanism generally consists of a conventional solenoid coil with a plunger attached to a diaphragm or piston. When energized, the electromagnetic field that is created around the coil attracts the plunger, supplying one phase of the cycle with a spring that returns the plunger when the coil is de-energized, thus supplying the second phase. This functionality is dependent on a pulsed power supply that switches the coil on and off and typically is supplied by a separate controller.

There are two distinct mechanisms that make up the average solenoid pump. The first is a solenoid that consists of a static, wire-wound coil and a moving plunger. This part of the device functions in the same way as most solenoids in other applications and relies on the magnetic field created around the coil when an electric current is passed through it. This magnetic field acts upon the ferrous metal plunger by rapidly moving it toward the coil. When the supply of electricity is cut to the coil, 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 moving fluid through its internal space by displacing it via the action of a reciprocating element. Generally, in a solenoid pump, this element is a piston or diaphragm and is reciprocated, or moved forward and backward continuously. The movement is supplied courtesy of the solenoid plunger that is attached to the piston or diaphragm.

The reciprocating action of the solenoid pump is achieved by pulsing, or alternately switching the power supply to the solenoid on and off. This causes the plunger to move first in one direction when the magnetic field attracts it, then in the other direction when the spring returns it to idle. Of course, this action is then repeated by the piston or diaphragm. The pulsed power for the solenoid is generally supplied by a separate controller, which might be used to control the speed — and thereby the output — of the pump. The solenoid pump is capable of high levels of accuracy and is often used in precision chemical dosing and fuel supply applications.