subject: Liquid Ring Vacuum Pumps - Solving Pressure Issues With Booster Blowers [print this page] Liquid ring vacuum pumps are popular choice when processing wet loads of gas. Its central assembly is designed to handle liquid loads without fear of breaking the pump. Even an enhanced pumping power can be recognized as the searing vapors squeeze in the colder liquid ring.
In severe cases where a liquid ring vacuum pump is not on hand, a dry or oil sealed vacuum pump can be utilized but again only in severe cases. Nonetheless, the liquid ring vacuum pump depends on the physical materials of the sealant to resolve its vacuum level limit which is mostly around 25mmHg.
When a stronger vacuum power is necessary, an additional pumping peripheral can be used like a blower or rotary booster. Connecting a rotary booster to the vacuum pump suction can lower the working pressure to about 4 to 10mm. Aside from getting a better performance, savings in time and money can also be realized compared to buying a new and larger vacuum pump.
A typical booster blower consists of two interlocking rotors to lock-in and pass on gas. The rotors revolve in opposing ways and are kept in harmony by peripheral gears. T he locked-in pocket of gas is then moved about to the boundaries of the housing and the rotor. The gas is running at an even rate when it is set loose at the outlet port. To sustain an invariable clearance involving the cylinder and the rotors, the lobes are kept in harmony by using timing gears.
The reverse-gassing of a blower is entirely dependent on these clearances. Booster blowers depend on detached lubricating liquid tanks situated on both end of the cylinder to lubricate the seals, bearings, and gears. Labyrinth seals are used to prevent the leakage of oil to the pumping compartment. The normal revolving velocity can go as high as 3-4000 rpm and are made from various materials to handle and process the mass of gas.
While the compression totally takes place at the outlet port of the blower, there is a small percentage for the condensed gas to transfer its heat to the cover of the blower and as a result blowers are usually restricted in their compression ratio. Usually for gas discharge velocity greater than 10mm, the theoretical boundary is 2.3:1. Mechanical malfunction might occur when the blower lobes and the outlet nozzle experience overheating caused by intense heat due to high compression ratios.
Elevated compression ratio can be reached if the pump operates at less than 10mm pressure. A huge gain like 50:1 is possible. This is reachable by linking a blower to a diminutive vacuum pump to have the power of a bigger vacuum pump. The pump's pressure will go lower than the vapor pressure ceiling of the liquid ring if this system is enforced.
Computing the temperature rise from point to point of the booster blower is rather plain and simple. The formula is based on the idea that when the pressure go down, the temperature rise coefficient also go down. The formula goes like this:
Temperature Rise = T x TRC x (K-1)/(K) x (SR-1)/VE
Where:
T = Absolute temperature of the inlet gas
TRC = Temperature Rise Coefficient
SR = Staging Ratio
VE = Volumetric Efficiency
To exemplify things; we have a blower at 10mm pressure with a staging ratio of 2:1 plus 100F of inlet gas temperature, we get 90F temperature rise. By editing the staging ratio to 3:1, we get 180F. Finally, by editing the inlet pressure to 1mm we get 24F.
By adding stages of compound booster blowers, we can lower the operating pressure to less than 4mm. It can also be done by blending ejectors and blowers. Running pressures as little as an mm are viable.
