What Is a Gear Pump?
A gear pump category belongs to the positive displacement pump, consisting of a continuous delivery rotary pump. With the help of gear meshings, mechanical energy is converted into fluid energy, and this creates zero suction. The space that is in the middle of the gear meshing, which carries a high level of viscous fluids towards the surface of the wall and then to the output. This pump works effectively for extended levels of viscous liquid such as oil as it does not require any priming.
The gear pump is a type of positive displacement rotary pump. In a gear pump, a fluid moves a certain amount of fluid using an interlocking gear and then moving it with the gear rotating. These pumps deliver a pulse-free flow that is directly proportional to the rotational speed of the gear.
Gear pumps are mainly used to develop high pressure. The gear pump is a positives displacement pump & also a fixed displacement pump. A positive displacement pump means that this pump provides a constant flow at a certain speed regardless of the change in pressure, & a fixed displacement pump means that it rejects a certain amount of fluid per revolution of the shaft.
The gear pump was invented around 1600 by Johannes Kepler. In a gear pump, there are usually two gears. One gear is the driver gear or power gear, and the other is the gear or idle gear. The driver gear is connected to some key movers or to a mechanical power source.
Driver gear is also known as masters gear, and driven gear is also known as slave gear. The driver gear is rotated either using an electric motor or using an I.C. engine, or using a hand.
Components of Gear Pumps:
#1. Driver Gear
The driver gear is connected to the prime mover. It rotates using power from the prime mover.
#2. Driven Gear or Idle Gear
The driven gear is forged with the drive gear, and the driver rotates the gear.
Both the driver gear & the driven gear are packed inside the casing of the gear pumps.
#4. Inlet Section or Suction Side
This is the section in the gear pump through which fluid enters the gear pump. The low-pressure liquid enters the pump from the inlet section.
#5. Outlet Section or Discharge Side
This is the section in the gear pump through which pressurized fluid is transported to the required area. High-pressure liquid flows from the pump to the outlet section.
#6. Prime Mover
In gear pumps, prime movers are used to providing power to the shaft in which the driver gear is mounted. It can be an electrical motor or an I.C. engine, or it can be manual labor.
#7. Safety Valve or Release Valve
A safety valve or release valves are installed on the discharge side so that the pump can be protected from being damaged if additional pressure arises when it is released.
Types of Gear Pump:
Typically, There Are Five Types of Gear Pumps:
- External Gear Pump
- Internal Gear Pump
- Lobe Pump
- Ge-Rotor Pump (Generated Rotor Pump)
- Screw Pump
#1. External Gear Pump
In an external gear pump, an external gear is used to pump fluid. In an external gear pump, two helical or spur gears are meshed with each other and placed inside the casing.
The gear used in this type of pump is external meshings types. In this type of pump, any gear type, either helical gear or spur gear, or any other type of gear, can be used. One of the two gears is the driving gear, and the other is the driven gear.
The driven gears will also rotate when the driver gear is rotated as both gear is in mesh with each other. In the external pump, partial vacuums are created at the inlet of the pump.
#2. Internal Gear Pump
In an internal gear pump, the gear used to pump the fluid has an internal trap. In the internal gear pumps, the inner gear is smaller and has outer teeth, and the outer gear is the larger gear and has the inner teeth. Between the two gears of the internals gear pump, a crescent seal is provided that fills the gap between the two gears.
As the teeth in the inner gear mesh with the outer gear, a partial vacuum is created, causing the fluid to enter the gap between the crescent seal and the inner gear. After that, the fluid gets trapped between the inner gear and the crescent seal and travels from the inlets to the outlet of the internal gear pump.
#3. Lobe Pump
This is another type of external gear pump. In lobe pumps, vans are used in place of gear teeth. The number of lobes can be 3 or 4, depending on the requirements.
Two lobes are fitted inside the casings. The lobe is designed in such a way that the lobes almost hold each other instead of touching and rotating in the case of an external gear pump. Due to the large size of vans and the low number of vans, high discharge is achieved.
#4. Ge- Rotor (generated rotor) pump
This pump has two generating rotors. One rotor has external teeth, & the other has internal teeth. The rotor with the outer teeth rotates inside the rotor with the inner teeth.
The number of teeth of the inner rotors is one less than that of the outer rotor. The shaft of the prime movers is coupled to the internal rotor. Therefore, the internal rotor is called the driver rotor.
Near the top of the Ge-Rotor pumps, the pocket size, i.e., the space between the outer and inner rotor, is negligible. Pocket size increases up to 180 degrees in the outer rotor teeth. So, the fluid is sucked near the inlets due to the vacuum between the inner rotor teeth and the outer rotor teeth.
After 180 degrees, when the fluid reached the bottom of the Ge-Rotor pump, the pocket-size begins to decrease, allowing the fluid to be transported through the outlet.
#5. Screw Pump
It is named screw pump because the screws are used in this pump to increase the pressure of the fluid. In this pump, the inlets are divided into two parts and have an outlet.
In screw pumps, one shaft has a left-hand screw, and the other shaft has a right-hand screw. Two inlets are present at the ends, & the outlet is in the opposite direction.
When the pumps are started, the liquid fills the gap between the threads of the screw at the edge of the inlet, and it moves axially along the screw from the inlet to the outlet due to the rotation of the liquid screw.
Working of Gear Pump:
On starting the gear pump, the driving shaft is started by providing power and begins to rotate the driving gear using power from the prime mover. The driver also rotates the forged gear along with the gear as the driver rotates the gear but in the opposite direction. As both gears start rotating, a partial vacuum is created on the suction side.
As soon as the vacuum is created, the liquid in the suction side is sucked towards the gear. After that, sucked liquid gets trapped between the gears & the casing.
Then the liquid trapped between the casing and gear teeth travels along with the rotation of the gear teeth and moves from the suction side to the discharge.
Similarly, the discharge gear from the suction side to the discharge side also has a liquid flow, and the high-pressure liquid discharges the pump from the discharge side.
The fluid from the suction side cannot directly go to the discharge and also from the suction side to the discharge as the two gears are fully engaged, and there is no lag for the fluid to flow.
Advantages of Gear Pump:
- These pumps are very simple & compact, with a very small number of moving parts.
- The maintenance costs of this type of pump are very lows.
- It costs less.
- Gear pumps can be used to generate very high pressures up to 3000 psi.
- It can be used to pumps highly viscous liquids like oil that cannot be pumped using centrifugal pumps.
- There is a very lows probability of leakage when pumping a high viscous liquid like oil into the gear pump. Therefore, the efficiency of this pump increases when pumping highly viscous fluids.
- Gear pumps can run in both directions. Therefore, a single pump can be used for both loading and unloading purposes.
- This pump is much less susceptible to contamination.
Disadvantages of Gear Pump:
- Meshing gears are used, friction fluid cannot be used in gear pumps.
- These pumps make a lot of noise.
- The size of gears pumps is limited, so they cannot be used for large bulk flow rates.
Applications of Gear Pump:
- These are used in applications where precise dosing is necessary.
- Since the gear pump is not overly affected by the output pressure, it can also be applied in applications where there is an unbalanced supply.