What is a Gear Pump and How Does It Works?


Dec 20th, 2018

What is a Gear Pump and How Does It Works?

Many people make use of automobiles every day without knowing the components which make them. However, getting to know some of these components and some maintenance tips would provide a great benefit to the users as well as owners of automobiles in different sectors. One of the crucial components of every automobile is the gear pump and this content would provide the crucial things which you need to know about the subject. Some of which include what a gear pump is and where it can be found.

What is a Gear Pump?

The gear pump is one of the essential pumps which are used in automobiles, this type of pump has gears in it which have the ability to provide pressure energy to the fluid in the pumps. Thus, the gear pumps transfer the fluid from one part to another with the aid of gear mechanism. If the pressure of the system remains constant then they will provide you with the fix rate also. The gear pump works by using positive displacement rotary pumps which helps you to transfer liquid or fluid with the aid of its gear. It has more than two internal gears which create vacuum pressure to push the fluid in the pump.

The gear pumps make use of high-pressure and comes in small sizes so as to provide a pulseless and stable fluid flows as compared to other pumps like peristaltic and diaphragm pumps. There are many other benefits of the gear pumps which make it superior than other pumps like a self-priming pump, can pump high viscosity fluids, user-friendly pump as it is easy to operate and to maintain as well.

Gear pumps comes in two major types:

  • External gear pumps include two external gears (inside the pump housing), one being a drive and the other being an idle gear.
  • Internal gear pumps include one external gear and one internal gear located inside the external gear (both inside the pump housing).

Gear pumps include tight tolerances and rigid gear & housing designs which allow for pumping liquids at higher pressures when compared with other kinds of pump.

Tolerance, Flowrate and Speed

Gear pumps are not a good choice for pumping liquids with solids in them due to the tight tolerance as well as resulting damage to the gears and other components. Additionally, gear pumps generally do not pump fluids of high flowrate and lower discharge pressure applications. Most gear pumps likewise need to be run at much lower speeds so that it can work effectively. The higher the viscosity of the liquid being pumped, the lower the speed of gear pump required.

Since gear pumps are positive displacement pump, they will provide minimal variation in the flowrate even with an increase or decrease in the discharge pressure in the system. This implies that the horsepower required for a given gear pump will increase as the pressure increases. The horsepower required for a specific gear pump will also increase as the viscosity increases, this will increase the discharge pressure in the piping system due to the increase in the frictional losses of the more viscous liquid on the piping walls as well as other plumbing components in the system.

Pressure Relief

Another essential requirement for gear pump system is to include a pressure relief valve in the discharge piping so as to relieve pressure back to the storage tank or other liquid supply source whenever the downstream valve is shut off. Some gear pumps include a built-in pressure relief valve which provide the same critical pressure but only for very short time periods. This is because the built-in pressure relief valves are internal to the gear pump and simply recirculate the liquid inside the gear pump itself. Recirculation inside the gear pump for other than very short time periods will cause the liquid to build heat quickly and will eventually ruin seals, packings or other key gear pump components.

Sometimes, gear pump bearing composes of a specially designed surface layer of PTFE formulations and is specifically applied for the high PV value. It can be used in medium, high-pressure gear pump, ram pump, and vane pumps and so on. As it is without lead, it makes the bearing lubricating condition cleaner, and in accordance with environmental request.

Although there are many other applications that use gear pumps, the most common example is the hydraulic gear pump that is used in the transmissions of many vehicles. Since it is so commonly used on vehicles, the proper maintenance becomes rather necessary because good maintenance tips might be able to save you the considerable expense.

The most important component you should pay attention to is the gear pump bearing because defective bearings allow the gears in the pump to shift position in the chamber, rather than remaining straight and true. Thus, you should check them to ensure their proper performance. And if pump bearings have some problems, you have to remove them by using a bearing puller.

Besides, you should check the teeth in the gears for signs of wear and tear. A brand-new gear pump usually ships with a clearance of about 0.005 to 0.007 inches between the teeth of the gears and the chamber wall. This clearance is just enough for a piece of very thin wrapping paper. Therefore, you can use this type of paper to check the clearance between the gear teeth. If the paper slides in and out between the teeth too easily, then the gears have been worn due to scrubbing or poor lubrication.

In addition to the pump bearing and gears, you should also check some other related components like the pin that holds the gears into their shafts because this will contribute to the reliable operation of the pump. The failure of the pin will result in its malfunction.


In summary, when asked any automobile user what is a gear pump, he or she would be able to provide a befitting answer after reading the content of this article. He or she would also be able to tell the specific place where gear pump is within a vehicle. Visit www.carpart.com.au for more awesome blog post about car parts.