Vacuum pumps:

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Vacuum pumps

The use of a vacuum pump can be the single most important step in the development of refrigeration and Air conditioning service. The goal of the vacuum pump for the removal of unwanted materials, which create pressure cooling system. They include:
  • Moisture
  • Air (oxygen)
  • Hydrochloric acid
In addition, there are other materials that will evaporate at low micron range. These, as well as a wide range of solid materials, pulled in a vacuum pump, the same way as a vacuum cleaner sucks in the dirt. Evacuation as a rule, is performed at almost every service call is where recharge is required.

NOTE: it is not acceptable to simply add refrigerant for a system with one end open to evacuate into the atmosphere. This shortcut was the darling of many specialists of the service Department for many years, because it was fast and refrigerant was inexpensive.

Vacuum levels previously unheard of Golf evacuation are performed daily on service of persons knowledgeable about the vacuum equipment.
These service of persons found through experience that the two-stage pump is much better than a single-stage pump for deep evacuation. Cm. Fig. 1-53 and 1-54. It was designed as a laboratory instrument and with minor changes; it has been adapted to the refrigeration field. Is the right tool for vacuum evacuation in the field.

To understand the benefits of two-stage pump for single-stage pump, see Fig. 1-55. It shows the interior of a two-stage vacuum pump. This is a simplified version of the stage vacuum. It is built on the principle of the Wankel engine.

A stationary camera with an eccentric rotor, rotating inside. In sliding vanes pull gases over the fence. They squeeze them and make them into the atmosphere through the exhaust. Blades create a partition vacuum and pressure section inside the pump. Seal between vacuum and pressure sections made vacuum pump oil. These seals are a critical factor in the depth that the vacuum pump can pull. If the seals leaks, pump not be able to draw a deep vacuum. Consequently, less gas can be processed. Pump with high leakage through the seal can take a deep vacuum on a small system, but leakage reduce the rate of pumping (cfm) in deep vacuum in the region. A long pull down once the result will be.

There are three oil seals in a single stage vacuum pump. Each lock should be against a high pressure on one side and vacuum on the other side. This places a significant load on a gland. Two-stage vacuum pump reduce pressure load on a gland in half. This pump uses two cameras instead of one evacuate the system. The first chamber is called deep vacuum chamber. It pulls in vacuum, gases from deep vacuum and pushes them into the second chamber at a moderate vacuum. The second chamber, or stage, brings in these gases at a moderate vacuum and pushes them into the atmosphere. This is the work of one camera divided between the two chambers. This, in turn, cuts in half the load of each seal oil, which reduces the leakage up to 90 percent.

Two-stage vacuum pump is more effective than a single stage vacuum pump. For example, a single stage vacuum pump rated 1,5 cfm power will take a half hour to evacuate one drop of water. Two-stage vacuum pump with the same rating will evacuate drop in 12 minutes

For the evacuation of the 5-ton system, saturated with moisture, not less than 15 hours evacuation takes time, using a single stage vacuum pump. Two-stage pump with the same cfm rating can do the job in as little as 2 hours

Another advantage of the two-stage pump reliability. As you can see, if the seal is to be effective, tolerances in these vacuum pumps should be very similar between the rotor and the stator. If tolerances are not correct, gland, would not be effective. Slippage tolerance due to wear is the main cause of the vacuum pump. With single-stage pump, when tolerance in the stage of invoices, pump loses its effectiveness. With a two-stage pump, if any stage loses tolerance, the other will still pull a single stage vacuum pump.

More cfm, two-stage vacuum pumps are preferred for single-stage vacuum pumps. The cost difference between them is not great. In addition, the time saved by using two-stage pump is evident on the first evacuation...

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