Hydraulic Gear Pump

In hydraulic drive systems hydraulic pumps are used to allow the system to carry out its functionality. Using mechanical power, a hydraulic pump turns it into hydraulic energy which also allows for different pressures at the inlet and outlet of the pump. There are three common types of hydraulic pumps and one of them is gear pump.

In hydraulic gear pumps, the mechanical action applied on the gears allow for the transfer of fluid. The pump works when mechanical energy causes the rotation of gears within causing the teeth of the gears to unmesh, allowing a vacuum to form in the inlet. This vacuum sucks in the liquid and fixed enclosed volume of liquid are transferred as the gears mesh at the outlet. Corresponding to the movement of the gear, proportional and pulse free liquid is transferred in gear pumps.

The use of hydraulic gear pump is mostly seen in places requiring the pumping of highly viscous fluids. They are also required in highly durable environments as hydraulic gear pumps are the best when it comes to working with abrasive contaminated liquids. Primarily hydraulic gear pumps can be seen with spur gears but other types of helical, bevel and screw gears are also used depending on the use cases. And overall, there are two types of hydraulic gear pumps;

External Gear Pump
As the name suggests, external gear pumps are the types of pumps where equal sized gears are brought together to interlock at a specific point while independently situated on separate shafts. In most cases external gear pumps have one driven and one ideal gear, but in some case both the gears are driven. In external gear pumps, the meshing and unmeshing happens between the gears and pressure is created as well as fluid is moved with the help of the tight tolerance between the gears and the casing. Since the gears interlock at the outlet, no fluid is allowed to seep through to the inlet side. External gear pumps are used in high pressure situations and requirements with high flow rates as the independent shafts allows for better security and strength.
Internal Gear Pump
Internal gear pumps on the other hand have one gear inside the other with teeth of the larger gear on the inside and smaller gear on the outside. The smaller gear is mounted off the center of the casing, portion of one side meshing with the larger gear while a big portion of the smaller gear sitting against a crescent shaped partition. The larger gear in internal gear pump is the one that is moved, it allows a vacuum to form when larger gear unmeshes from the smaller gear. The liquid is forced into the void which in turn gets trapped against the underside of the crescent partition. As the gears mesh again, the liquid is forced out of the internal gear tooth and through the outlet. Internal gear pumps have high suction capability and is used mostly in high viscous environments.

There are clear considerations to make when choosing hydraulic pumps and here are some advantages afforded by gear pumps;

Pressure and Temperature
Gear pumps are ideal for pressures of up to 3000 psi, depending on the design of gear pump used, pressure requirements are met for most environments and conditions. Gear pumps are also good for variable temperature environments.
Sound
While the older forms of gear pumps were noisy to operate the newer iterations are quieter. They do still produce noise, they are mechanical machines, but sound pollution is drastically reduced in gear pumps allowing for newer areas of use.
Metering and dosing application
Flow control is possible for gear pumps and can be used for metering and dosing applications.
Gear pumps do not have fluid
Gear pumps do not have fluid restrictions so different types of liquids can be introduced to the pump. This also allows for blending and mixing applications rarely afforded by other pumps.
Mitigated with the normal wear and tear
Gear pumps are reliable as the case for catastrophic break down is mitigated with the normal wear and tear of the gears.
Can be used with corrosive or contaminated liquids
Gear pumps are the only pumps that can be used with corrosive or contaminated liquids. You can certainly use other pumps for this purpose, but gear pumps do the task over a longer period of time without causing much damage to the pump.

While gear pumps are perfect for certain conditions, there are also limitations attached with using the pump, such as;

Work with contaminated liquids and corrosive fluids
While the pump can work with contaminated liquids and corrosive fluids, solid wastes are not allowed in the pump. Gear pumps have low clearances. The spaces between the gears and casings are limited which does not allow for solid transfer without doing catastrophic damage to the working of the pump.
Rate of gear pumps is not changeable
The flow rate of gear pumps is not changeable as is the case for other types of hydraulic pumps.
Precise tolerance
Gears need to have precise tolerance to not allow backflow of fluid which requires precise machining work.
Lubrication helps in elongating the lifespan
They are self-priming pumps and while they can work in dry conditions, lubrication helps in elongating the lifespan of the gear as well as its functioning. But lubrication can also contaminate the fluid being pumped and it is unadvisable to dry run gear pumps over a long period of time.
Close tolerances
Due to the close tolerances of the gears and casing, normal wear and tear can be seen. While this wear of gears prevents against the catastrophic failure of the pump, it turns the pump useless and repairs are as expensive as buying a new pump.

Eurobalt Engineering Provides Gear Pumps and Hydraulic Drive Systems

As part of our initiative to be a one stop shop for all things hydraulics, Eurobalt Engineering has been working for years to brings its own pumps to the market. We have studied the leading pump brands and considering our gear pumps to be at the same level as some industry leaders. So, when you are buying hydraulic cylinders with our company, we can offer the complete hydraulic drive system including hoses and other requirements. So, please give us a call or send an email with your requirements and we would be glad to be of some assistance for your hydraulic gear pump needs.