How Does a Fluid Pump Work?

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  • Written By: M. McGee
  • Edited By: Lauren Fritsky
  • Last Modified Date: 13 October 2019
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A fluid pump is a system that allows liquid to overcome gravity. Nearly all pumps share a few common pieces: and inlet and outlet for the fluid, a method of making the fluid move and a motivating force. While the inner construction and the motivation for the pump may change, most of them work using a process called siphoning. This is basically the tendency a fluid has to keep moving once it starts moving. In many cases, a pump gets the fluid going and then siphoning does a lot of the pump’s work for it.

In order to understand how a fluid pump works, it is important to understand siphoning. When fluid in a pipe begins to move, the fluid behind it will move along with it, even if that means it flows uphill. This is caused through a number of factors, but it is mostly based on pressure differences. As the liquid flows forward, it moves away from liquid in parts of the pipe that don’t flow as well. For example, the liquid in a straight section of pipe will begin to flow away from the liquid in a vertical section.


As this fluid moves away, a low-pressure area is created behind it. The water in the vertical pipe will then have a high-pressure area one side, the pressure of the fluid behind it, and a low-pressure area on the other. This will cause the fluid to move forward as soon as the pressure difference overcomes the force of gravity on the fluid. The sequence will continue indefinitely, creating steadily flowing liquid, as long as the pressure remains constant.

In many ways, a common fluid pump just adds additional motivation to this natural process. Most of the time, a fluid pump has four main parts. The input pipe and outlet pipe are simply fixed pipes that contain the fluid. In order for siphoning to work well, these pipes have as little air in them as possible. Excess air will keep the pipe pressure higher, so the siphoning requires more force to move the fluid.

The other two parts of a fluid pump are the more important parts. One is a power source and the other is a way of generating additional force or preventing force from dropping on the backside of the system. These parts are widely different in different types of pumps. For instance, a totally mechanical pump may use gravity for a power source and a one-way valve to block backpressure. A simple electric pump will use electricity for power; the power will spin a wheel in the pump, which increases the force of the flowing water and allows the siphoning to work more effectively.


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