Despite not being well-known, rotary vane pumps are essential in daily life. Rotary vane pumps unquestionably play a significant role in the goods you use, whether it’s moving power steering fluid in automobiles, keeping the right amount of carbonation in a soda, or moving thick liquids without compromising their quality. You can learn more about rotary vane pumps below, including what they are, how they operate, pros and cons, and several types of vane pumps.
What is a rotary vane pump?
A rotary vane pump, also referred to as a vacuum pump, is a self-priming positive displacement pump that pumps gases and liquids by means of vanes fixed to a rotor inside of a cylindrical housing. The gases and liquids are pressurised, compressed, and sent via the pump outlet. Vacuum pumps are used by automakers in a variety of systems, including power steering, air conditioning, and automatic transmissions. Rotating vane pumps are also used in the food and beverage industry for the transportation of viscous liquids, espresso makers and drink fountain dispensers. They are frequently utilised in the water treatment sector to pressurise water and feed it to membranes for reverse osmosis filtration.
centrifugal versus positive displacement pumps
A rotary vane pump is a positive displacement pump, as was already mentioned. The way that positive displacement pumps function is by sucking up a specific amount of liquid and moving it back and forth between the suction and discharge chambers. Pressure is produced by the vanes’ seals and the liquid’s flow. Positive displacement pumps are unaffected by the fluid’s input pressure and may maintain high pressures while using little suction pressure. Centrifugal pumps, on the other hand, produce an initial pressure that causes flow.
Higher viscosity liquids can be pumped using positive displacement pumps as opposed to centrifugal pumps. Frictional losses within centrifugal pumps are the cause of this. Positive displacement pumps, on the other hand, up to a point become more effective with higher viscosity liquids.
How does a rotary vane pump work?
Two or more chambers are present in rotary vane pumps, which compress, rotate, and discharge gases and liquids. The vacuum produced by these chambers pressurises the contents, enabling them to pass through the output of the pump. The vanes revolve and slide against the rotor’s interior wall. One chamber forms when the vanes turn, and the outlet valve separates it into suction and discharge sides. The fluid enters the chamber’s suction side and is compressed there as the chamber rotates. The contents of the suction chamber discharge into the discharge chamber and out the pump outlet after it has reached its maximum capacity. Finally, an exhaust valve stops contents from trying to reenter the pump, preventing backflow.
What are rotary vane pumps used for?
High-pressure vacuum pumps are commonly used for transporting freon, power-steering fluid, and transmission fluid in automobiles. On the other hand, medium-pressure pumps transport water in espresso machines and carbonated beverage dispensers. While less common than higher pressure pumps, low-pressure rotary vane pumps are used in chemical vapor deposition, a method used to create thin film for semiconductors. Other uses for vacuum pumps include:
- Dust extraction systems
- Industrial furnaces
- Vacuum filtration
- Degassing
- Crystallization
- Distillation drying
Parts of a rotary vane pump
The major components of a rotary vane pump are the following:
- Rotor
- Stator
- Vanes (also called blades)
- Cylindrical housing
- Inlet
- Exhaust valve
- Exhaust outlet
- Oil reservoir
- Splash guard
Types of rotary vane pumps
Rotary vane pumps generally perform the same function, but they can have many different types of vanes. These vane types include:
Sliding – vanes slide in and out to draw liquid in through the inlet port and into the chamber
Flexible – vanes maintain contact with the rotor walls, trapping liquid as the vanes rotate
External – vanes are fitted into the pump’s casing instead of the rotor
Rotating – vanes rotate inside the cavity to trap liquids
Oscillating – vanes draw in liquids with an oscillating pumping motion
The most prevalent kind of rotary vane pump is the sliding and flexible vane pump, which is employed in a variety of industrial applications. Espresso machines and drink fountains frequently have sliding vane pumps nearby. They move warm water through espresso grinds and pressurise CO2 tanks with it. Flexible vane pumps, on the other hand, are frequently utilised in food and pharmaceutical applications. They can safely transport solid-containing liquids like yoghurt and viscous liquids like creams without affecting the product’s quality.
Oil-lubricated vs dry-running rotary vane pumps
Dry-running and oil-lubricated work very similarly, but oil decreases wear on the pump and enhances the seals formed in the rotor.
Oil-lubricated rotary vane pump operation
Oil-lubricated vane pumps operate like dry vane pumps with a few key differences. They cannot be used in the water treatment industry because of their residual effects on the discharge.
- An oil pipe feeds the cylindrical housing oil, where it coats the vanes and walls to prevent wear.
- The vanes push against the rotor walls, forming chambers that capture air and liquid.
- The captured air and fluid are compressed and transported to a compression chamber.
- When the chamber reaches its maximum compression, it opens and discharges into the oil separator housing
- The oil separator housing removes oil particles from the air or liquid.
- Further filtration removes leftover oil particles.
- The air or liquid is discharged through the outlet.
- Dry rotary vane pump operation
- Dry vane pumps operate like oil-lubricated vane pumps with a few key differences.
Dry-running pumps use graphite vanes that contact the inner walls of the rotor. The graphite coats the walls, allowing the vanes to contact them with minimal wear.
When liquid enters, the vanes trap the liquid in the chamber, where it is compressed, rotated, and discharged.
Excess air is discharged after the fluid is compressed.
Unlike oil-lubricated vane pumps, dry-running pumps do not need any post-filtration because nothing has been added to the air or liquid.
Do rotary vane pumps need oil?
Oil is a helpful addition to a rotary vane pump in some cases, but it is not ideal for every application. Oil performs four essential functions in a vane pump:
- Seals between the rotor and vanes
- Forms a second seal between vanes and chamber
- Cools the pump by dispersing heat
- Protects components from corrosion
Oil provides seals that make vacuum pumps far more efficient than dry-running ones. However, oil can exit with pressurized gasses in a pump, making it unsuitable for some applications. Oil traps help mitigate oil expulsion, but pumps will always expel oil regardless of how high-quality the oil trap is.
Benefits of oil in a rotary vane pump
While rotary vane pumps can run completely dry, some units benefit from the lubrication oil provides. The following are benefits oil has on a rotary vane pump:
- Provides a seal that enhances the ability to form a vacuum
- Elongates the life of a pump by preventing wear
- Keeps temperatures cool by reducing friction
- Eliminates impurities and prevents them from damaging the pump
- Prevents pump from corrosion caused by reacting with gas
- Increases the efficiency of the pump by creating more effective seals
Advantages of rotary vane pumps
Rotary vane pumps have many advantages regardless of the types of vanes inside them.
- Extended lifespan due to durable vanes
- Quiet operation
- Little vibration
- Low maintenance
- Can run completely dry
- Lightweight and compact
- Discharged liquid is not sensitive to viscosity changes
- Stable flow rate with low pulsation
Disadvantages of rotary vane pumps
Rotary vane pumps are excellent at transporting liquids, but their operation does pose some risks and disadvantages.
- Poor durability when in contact with abrasive materials
- Prone to damage when operating with thicker liquids
- Proper filtration systems needed before adding liquids to the pump
- Not suitable for very high pressures