Vacuum Pump (Liquid Ring Type)
Vacuum pump is rotary positive displacement pump, liquid ring type. It is a pump in which head is developed by running the impeller in an eccentric position related to the auxiliary liquid which rotates in concentric alignment with casing. The liquid is forced in and out of cell rather like a piston, thus creating pressure or vacuum.
The pump is continuously supplied with a service liquid which,
- Seals the space between the impeller blades and walls of the casing
- Forms the liquid ring necessary to compress the gas being handled
- Absorbs and carries away the heat generated during compression
On starting up the pump, the liquid in the casing is thrown by centrifugal force to the periphery of the impeller forming the liquid ring. Air or gas enters the pump casing through the suction port where it is retained in the impeller cells.
As the impeller rotates, the eccentric position of the impeller forces the liquid ring into the cells compressing the gas, finally expelling it through the discharge port. This method of operation produces a non-pulsating vacuum.
Note: The liquid ring absorbs the greater part of the heat produced during compression, so that the gas is compressed almost isothermally.
Vacuum pumps have been designed to meet the needs of industrial users for non corrosive environment applications such as Air conditioning and Refrigeration manufacturing. They are utilized for both pre-evacuation carousels as well as integrated into leak testing and refrigerant charging equipment.
Main Features of Vacuum Pump
- Long Life: Forced lubrication and virtually vibration free operation, contribute to less wear and trouble free service life
- Modular Construction: Replacement parts interchangeable with different size models
- Cool running: Forced ventilation maintains optimum operating temperatures, extending oil and gasket life. Enhanced air flow allows the pump to run 10 degree Celsius cooler than standard rotary vane pumps. The lower temperature leads to reduced chemical activity within the pump and slows down rates of oil consumption
- Quiet: Operate at or below ambient noise levels in the production environment
- Internal Surface Protection: Inside surface of the oil case has a corrosion coating. It slows down metal corrosion and it extend service interval
- Large oil capacity: Chemical vapors that sublime from the fore line cold trap into the pump oil are more diluted due to the larger oil capacity. This minimizes the rates of oil breakdown and reduce chemical attacks within the pump
Stages of Vacuum Pump
A traditional rotary vane pump has four stages of operation.
Induction is a term that refers to the process of The gas is induced into the pumping chamber by the first 180° rotation of the rotor. The crescent-shaped area provided by the offset-mounted rotor raises the volume filled by the gas. The gas pressure reduces as the volume of the gas increases (Boyle’s law). The gas is drawn into the pump, which creates the necessary vacuum.
Isolation is a word that comes up a lot. The inlet port is sealed off from the gas being injected when the uppermost vane crosses over it.
Compression is a term used to describe the process of compress Due to the shrinking area between the rotor and stator, further rotating compresses and heats the gas ahead of the lowermost vane, lowering its length.
Exhaust. If the lowermost vane begins to rotate, the pressure in front of it rises to the point that the exhaust valve opens, allowing the gas to be discharged at a pressure marginally higher than atmospheric.
Application of Vacuum Pumps
These pumps are used as:
- Siphon pipes, turbine chambers and suction pipes of centrifugal pumps
- Condenser air pumps, vaporizers and dryers of all kinds
- Exhausting moist air, gases or vapours from vacuum impregnating tasks, disinfecting plants etc.,
- Crystallization process and other similar purposes in sugar, food stuff factories and chemical and process industries
- It is used for sewage disposal
Advantages of Two stage vacuum pumps
- Vacuum pump delivers excellent ultimate vacuum, high pumping speed, quiet and cool operation and easy maintenance.
- Durability and product support are additional highlights of these pumps.
- Enhanced features such as anti suck back device, continuous duty cycle rating and low ultimate vacuum are some extra features available in Vacuum pump.