It is always essential to choose the right tool for the right job, especially when you are using vacuum technology for your applications. It is a fact that no two vacuum technologies are the same, and no single vacuum pump is applicable for all industrial uses.
Sometimes you come across the situation where you have to decide between the liquid ring vacuum pump and dry screw vacuum pump in the process industry. Selecting the right vacuum pump can help you ensure smooth and efficient operation, improving consistency and maximizing return on investment.
The dry screw vacuum pump and liquid ring vacuum pump both are positive displacement pumps. However, the main difference between them is that the dry screw vacuum pump does not use fluids to create a vacuum, whereas the liquid ring vacuum pump uses liquid to create the vacuum.
Many apprentices are often confused between both of them. So let us understand the difference between a dry screw vacuum pump and a liquid ring vacuum pump.
Difference between Dry Screw vacuum pump and Liquid Ring vacuum pump
- Based on working principle
The liquid ring vacuum pump consists of a cylindrical housing partially filled with sealing liquid to create a vacuum. The vacuum generation is done through a rotating multi-blade impeller mounted on a shaft positioned eccentrically within the housing. The rotation of the impeller creates a centrifugal force, and a liquid ring is created. This liquid ring creates the vacuum needed for an operation.
Dry screw vacuum pumps generate vacuum through the rotation of two screw rotors arranged parallel to each other, rotating in the opposite direction. The rotor's movement decreases the volume of the trapped gas and results in the compression of the gas, moving it out through the exhaust. No lubrication is required in the compression chamber as the rotors do not contact each other during the compression process. As a result, this is referred to as dry technology.
- Based on discharge temperature
The inherent design of a liquid ring pump has the benefit of allowing using a variety of liquids as sealants, including solvents, oil, water, or other compatible fluids. As the liquid is in contact with the compressed gas/vapors in the process, the gas compression is considered isothermal. The final discharge temperatures at the outlet are controlled between 45 and 150°F. Hence the liquid ring vacuum pump offers great flexibility as different gases can be either condensed or passed through it.
Due to the constant-pitch design or progressive pitch design of dry screw vacuum pumps, the gas/vapor is transported at constant volume to the discharge port. The compression process is considered adiabatic, with discharge temperatures as high as 450°F. Such high temperatures can cause safety concerns with this pump technology.
- Based on operation conditions
The liquid ring vacuum pump can take the dirtiest application and have a high tolerance for harsh environments, violent saturated air, or vapor loads. Since the gas compression process is isothermal, the pump is suitable for pumping flammable, explosive, and toxic gases.
The dry screw vacuum pump is not suitable for pumping gases contaminated with oil, dust, or water vapor. They can be applied to a relatively dry clean gas stream only.
- Based on operation and maintenance cost
Liquid ring vacuum pumps have only one moving part - impeller, and there is no metal-to-metal contact between the rotating parts and the casing. With these design characteristics, liquid ring pumps are easy to maintain, and there is no need to replace the accessories for 2-3 years.
Dry screw pumps require the replacement of lubricants and require expensive inlet filtration systems to be maintained regularly. Hence the complete repair and maintenance of dry screw pumps incur high costs.
- Thus, we conclude that, from the above differences between the liquid ring vacuum pump and dry screw vacuum pump, you will now be able to decide the right pump for your industrial application. Picking the right vacuum pump will ensure you a smooth operation with a high return on your investments.
