The Working Of A Gear Pump
Gear pumps use the motion of the rotating gears to move liquids. A gear pump works on the basic principle of positive displacement where fluid is trapped and transported in a consistent and predictable manner.
It works in the following way:
At the start-up stage, the gear pump starts working when the energy is supplied to the drive shaft then the driver or power gear begins to revolve by utilizing the power of the prime mover.
The driven or idler gear (that meshes with the power or driver gear) also revolves with the rotation of the power gear, but it rotates in the reverse direction. When these two gears start to rotate, a partial vacuum starts generating on the suction side of the pump.
When the vacuum is generated, then the suction-side fluid is drawn into the gear cavity.
As the gear rotates, the liquid is carried in the cavity between the housing and the gear.
The fluid being carried between the gear teeth and the housing move as the gear teeth rotate. This fluid is transported from the inlet side to the outlet side. At the outlet side, the gear begins to mesh, squeezing the liquid out of the gear cavity. This squeezing creates pressure and forces liquid out of the discharge side of the pump.
Since the driver and driven gears of a gear pump are meshed with each other, there is little room to no for the fluid to return back to the suction side.
For more information watch here: THREE Pumping Principles and How They Work
Advantages & Disadvantages of Types of Gear pumps
Gear pumps are a popular type of positive displacement pump used for fluid transfer and metering applications. They operate by using rotating gears to trap and transport fluid from the inlet to the outlet of the pump. Gear pumps are known for their simplicity, compact design, and reliable performance. The selection of the correct type of gear pump depends on the specific needs of the application. Both Internal and External Gear pumps has its own design variations and features that cater to different requirements, making gear pumps versatile and widely used in various industries.
Disadvantages of Internal Gear Pumps | |
|---|---|
The maintenance is easy | It has a higher price than an external |
Low NPSH needed | Cantilever load on the bearing |
Operates at moderate pressure | Medium pressure limit |
It has only two moving components | Usually needs average speed |
Best suitable for high viscous fluids | |
Only a single stuffing box | |
Non-pulsating release | |
Normal operation in any direction | |
One-sided adjustable clearance | |
Its flexible design allows you to customize your application. | |
Its flexible design allows you to customize your application. |
Advantages of External Gear Pumps | Disadvantages of External Gear Pumps |
|---|---|
High speed | Four bushings in liquid area |
High pressure | No solids allowed |
No overhung bearing loads | Fixed End Clearances |
Relatively quiet operation | |
Suitability to pumping hazardous or hygienic fluids | |
Resistance and long-lasting performance | |
Design accommodates wide variety of materials |
Advantages and Disadvantages Of A Gear Pump
Advantages Of Gear Pump | Disadvantages Of Gear Pump |
|---|---|
These pumps are very simple and compact with very few numbers of moving parts | As meshing gears are used, abrasive fluids cannot be used in the gear pump. |
The maintenance cost of this type of pump is low | These pumps are noisy. Interlocking gears tend to be loud |
It has a low cost | The size of gear pumps is limited so it cannot be used for large bulk flow rates. |
Gear pump can be used for generating very high pressure up to 3000 psi | Not easy to repair after wear |
It can be used to pump highly viscous fluids like oils which cannot be pumped using centrifugal pumps | They supply pulsating flow |
There are very low chances of leakage while pumping high viscous liquid like oil in the gear pump. Hence, the efficiency of this pump increases when pumping highly viscous liquids | |
This pump is very less sensitive to contamination | |
Gear pumps can run in both directions. Hence, a single pump can be used for both loading and unloading purposes |
Considerations when selecting a gear pump
Just like other pumps, gear pumps also have limitations that must be accounted for.
Difficult to Repair – Maintenance of gear pumps can be easy. But when it comes to fixing some of their issues, industries may have to spend some more time as gear pumps are more difficult to repair. Despite the best precautions, gear pumps generally succumb to wear of the gears, casing, and bearings over time. As clearances increase, there is a gradual reduction in efficiency and increase in flow slip: leakage of the pumped fluid from the discharge back to the suction side. Flow slip is proportional to the cube of the clearance between the gear teeth and casing so, in practice, wear has a small effect until a critical point is reached, from which performance degrades rapidly.
Distinctive Operating Noise – Another limitation of gear pumps is that they can emit a quite distinctive noise. Gear pumps may be known for their radial force imbalance and large flow artery, which makes them generate noise during operations. With applications that may be sensitive to noise, it might be better if other types of pumps will be maximised.
If the pump is expected to handle abrasive solids it is advisable to select a pump with a higher capacity so it can be operated at lower speeds to reduce wear. However, it should be borne in mind that the volumetric efficiency of a gear pump is reduced at lower speeds and flow rates. A gear pump should not be operated too far from its recommended speed.
For high temperature applications, it is important to ensure that the operating temperature range is compatible with the pump specification. Thermal expansion of the casing and gears reduces clearances within a pump, and this can also lead to increased wear, and in extreme cases, pump failure.
For more information on selection the correct gear pump please click here: How to Select the Right Gear Pump?