A vacuum pump is a type of pump which is used to evacuate a gas from an enclosed space. The purpose of evacuating the gas from the sealed volume is to create a vacuum. A predecessor of the vacuum pump is the suction pump, which has been used throughout human history.
Uses of Vacuum Pumps
While the use of vacuum pump is made extensively across multiple industries, scientific laboratories also find use of vacuum pumps for the below purposes:
- Solvent evaporation by vapor pressure reduction
- Suction used for filtration or aspiration of suspended or liquid samples
- Evaluation of air molecules to improve detection sensitivity of instruments
- Negative pressure arrangement to prevent possibility of leak of hazardous chemicals
- Collection of gas samples from atmosphere or test chambers
Different Types of vacuum pumps and their use
While vacuum pumps come in different types and forms, the pumps most widely used in science laboratory settings are the rotary vane pumps, combination pumps, diaphragm pumps and scroll pumps.
RV or Rotary Vane Vacuum Pumps
This is a positive displacement pump that consists of vanes mounted to a rotor which rotates inside a cavity. Traditional oil sealed rotary vane vacuum pumps find the most commonly use since they are less costly to purchase and maintain, can be used in a variety of applications, and the contamination is flushed out with fluid changes. Rotary vane pumps use oil or inert fluids to lubricate working parts, ensure a tight seal, and remove heat, cooling the rotors in the process.
Rotary Vane pumps have very high displacement capacities, which makes them a good choice for freeze drying applications. Rotary vane pumps also work well with aqueous solvent and samples with very high boiling points and whose vapors can be trapped with ease before reaching the pump.
Diaphragm Vacuum Pumps
These are dry pumps which use a pulsing motion, to open and close valves to move the air. While they can be slightly expensive, they do not require oil, and this can save a lot of operation and maintenance costs.
Diaphragm vacuum pumps are among the most corrosion and chemical resistant pumps in use. Hence they are ideal for almost all types of samples, including acids and solvents. Diaphragm pumps are an excellent choice for both concentration and evaporation. However, they cannot be used for freeze-drying since their vacuum depth is not sufficient.
Combination or Hybrid Vacuum Pumps
Combination vacuum pumps combine the high performance rotary vane pump with the chemical-resistant diaphragm pump to create a low maintenance and durable pump. The diaphragm pump is responsible for removing the condensable vapors in the rotary vane pump without causing contamination of the oil, thus extending the life of the oil and ultimately the life of the vacuum pump.
Since diaphragm pumps are part of the combination pump’s design, these pumps are capable of handling solvents and acids better than typical Rotary Vane pumps.
Combination pumps are best suited for freeze-drying of volatile or corrosive samples since they can be used with a variety of acidic samples and others that contain harsh chemicals.
Scroll Vacuum Pumps
Scroll vacuum pumps consist of one fixed and one orbiting scroll. The orbiting scroll moves within the fixed scroll, creating a void at the inlet to draw in the gas, and discharged at the center of the two scrolls. They are well known for dry operation, low noise, minimum vibrations and compact design for lab use.
These pumps are ideal for freeze-drying since they can be used with solvent and aqueous solvent samples like acetonitrile. Scroll pumps also find their use with concentration applications.
Conclusion
Vacuum pumps prove to be an indispensable laboratory equipment . The selection of the type of vacuum pump should be on the basis of it’s application. Follow the OEM manuals with respect to periodic maintenance, to prevent damage and keep it in efficient working co
Also Read: What is a Burette? Types & Uses
