Vacuum pumps are used in a wide range of applications in various industries. The vacuum pump removes gas from the sealing volume to create a slight vacuum. Due to the change in the pressure gradient, the liquid is released into the vacuum. There are three types of vacuum pumps: centrifugal pumps, positive displacement pumps, and receiving pumps.
A centrifugal pump is a most efficient type than other types of vacuum pumps.
Type of vacuum pumps
The vacuum pumps have the following types:
1) Diaphragm pump
The diaphragm is quickly bent by a rod mounted on an engine-driven camshaft, causing gas to flow from one valve to the other. It has a compact structure and low maintenance costs. The life of the diaphragm and valves is generally greater than 10,000 hours.Diaphragm pumps are used to support small hybrid pumps in high vacuum cleaning applications. It is a small volume pump widely used for sample preparation in research and development laboratories.
2) Liquid Ring Vacuum Pump
In this vacuum pump, gas compresses by turning the eccentric impeller into the pump body. The liquid enters the pump, and under the action of centrifugal acceleration, a movable cylinder ring is created inside the pumping chamber. This liquid ring creates a series of seals in the space between the impeller blades that form the compression chamber.
The eccentricity between the impeller and the pump body causes a circular variation in the volume of the blades and rings.It compresses the gas and discharges it through a port at the end of the chamber. The pump has a simple and stable design because the shaft and impeller are the only moving parts. It is very tolerant of processing disturbances and has a large capacity.
3) Scroll Pump
The scroll vacuum pump uses two non-rotating vortices, but the internal vortex surrounds and sucks a certain volume of gas, reducing it in volume. It is pressed to reach the minimum volume and the volume in the centre of the spiral where the exit is located. The high-pressure spiral polymer (PTFE) spiral seal provides an axial seal between two volts without the need for lubrication in the refining gas stream.
4) Root pump
Root pumps are mainly used as a vacuum booster to remove large amounts of gas.
The two blades grill without touching and rotate in opposite directions to transport gas in one direction through the pump continuously. It improves the performance of the primary/reserve pump, increases the pumping speed by approximately 7:1 and increases the final pressure by approximately 10:1. Root pumps can have two or more impellers.
5) Screw pump
The screw pump uses two rotating screws, one for the left hand and one for the right hand, which are rotated without contact with each other. The gas rotates from one end to the other. The design of the screw is due to the reduction of the space between them as the gas passes and is compressed, which leads to a reduction in pressure at the end of the inlet. The pump has high performance, excellent fluid carrying capacity and can withstand dust and harsh environments.
Disadvantages of Vacuum pumps
- Productivity is low, generally around 30, even better up to 50.
- The low vacuum is not limited only by the structural design, but above all, it is limited by the saturated vapour pressure of the working fluid.
- In water as a working fluid, the maximum pressure can reach 200. In oil as a working fluid, the maximum pressure can reach 130 Pa.
Applications of Vacuum pumps
- Since the vacuum pump is rotary with respect to isothermal gas compression, it can absorb flammable and explosive gases. Since there is no drain valve or friction surface, it can absorb dust, impermeable gases and wetting agents. With these unique features, despite its low efficiency, it is still widely used.
- Liquid ring vacuum pumps are often used in water purification, food processing and pharmaceutical manufacturing.
- Vacuum pumps are used for drying, steam recovery, etc.
- Food industry: used to remove water in the food production process.
- Repair of water bodies: used for the treatment of damaged water, dirty groundwater, etc.
- The vacuum pump can also use to intensify or assist machine equipment. In vehicles with hybrid and diesel engines, an engine mounted pump (usually on a camshaft) is used to create the vacuum.