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Selasa, 05 April 2011

Vacuum Pump

Vacuum Pump

Liquid Ring Vacuum Pump is design to remove un-condensable gas inside condenser. If accumulation of condensable gas is going to increase, the vacuum of condenser is drop and makes performance or efficiency of power station drop too.

Beginning to vacuum pump seal water heat exchanger is dirty. Inlet seal water temperature is increasing from 30C to 35C. If suction of vacuum pump pressure -0.95 Barg, some seal water is already vapor and it makes low performance of vacuum pump. Condenser vacuum is going to increase from -0.93 Barg to -0.90 Barg. And Saturation temperature increase from 41C to 52C.

Keep inlet seal water temperature below 35C.

Liquid Ring
Another vacuum producing device that can evacuate vessels containing condensable or otherwise “wet” loads is the liquid ring vacuum pump. In its approximately cylindrical body, a sealant fluid under centrifugal force forms a ring against the inside of the concentric casing

The source of that force is multi bladed impeller whose shaft mounted so as to be eccentric to the ring of liquid. Because of this eccentricity, the pockets bounded by adjacent impeller blades (also called buckets) and the ring increase in size on the inlet side of the pump, and the resulting suction continually draws gas out of the vessel being evacuated as the blade rotate toward the discharge side of the pump, the pocket decrease in size and the evacuated gas compressed, enabling its discharge.
The ring of liquid not only acts as a seal, it also absorbs the heat of compression, friction and condensation. In principle virtually any type of liquid can be used so long as it is not prone to vaporization and thus to cavitation at process condition.

Some times called a jet pump, an ejector works by converting pressure energy of a motive fluid (which may be the same as or different from the process fluid) into velocity energy (kinetic energy) as it flows through a relatively small converging-diverging nozzle.

This lowered pressure of motive fluid creates suction in a mixing chamber, into which process fluid is drawn fro the vessel being evacuated. The process fluid mixes with and becomes entrained in the motive fluid stream. This mixed fluid then passes on through a converging-diverging diffuser, where the velocity is converted back to pressure energy.

Dry vacuum Pump
Unlike ejector and liquid ring pumps, dry vacuum pumps are device that need no working fluid. These pump work by either of two mechanisms, volumetric reduction or the mixing of lower-pressure gas with higher-pressure discharge gas (as in a root blower.

Unlike liquid ring pumps, dry pump normally run hot, because there is no liquid to absorb the heat of compression. This increases the temperature of the process gas. To counteract this, some designs provide for pre-compression by recycling discharges gas that has been cooled.

OTO vacuum pump
A once-through-oil (OTO) vacuum pump is a sliding-vane type that uses once-through oil to seal clearances and lubricates moving parts. The vanes are in slots in a rotor, mounted eccentrically to the pump chamber.

As the rotor assembly rotates, centrifugal force pushes the vanes out of the slots and against the chamber walls, creating pocket whose size varies similarly to those of the liquid ring pump. Because of this variation, suction draws process gas into the pump from the vessel being evacuated, and compression occur as the vanes rotate toward the discharge side of the device, decreasing the area and forcing the gas and lubricating oil against the discharge valve. The discharge valve opens slightly above atmospheric pressure.

1 komentar:

  1. Vacuum pumps come in a variety of sizes and purposes. it works by moving liquid from one place to another through the use vacuum.