Refrigeration Compressors by Secop
For a refrigeration system to be effective, there has to be a means of extracting heat from where it is not wanted and dumping it somewhere else. The most common form of refrigeration system is the vapour-compression system, which is not only used in refrigerators of all sizes but also to air condition everything from automobiles right on up to massive spaces such as airports, hospitals, and oil refineries. It consists of four main components: the compressor, the condenser, the throttle valve (or „thermal expansion valve“), and the evaporator.
The role of the compressor is to take in vapor that has absorbed heat from the environment and compress it down to a superheated state.
There are three main types of refrigeration compressor:
Hermetically sealed, semi-hermetic, and open. Of the three, the hermetically sealed unit is the easiest to maintain: if it breaks down, replace it. The shell is cast as a single unit – there is no way to open it up for repair or maintenance. This is most often seen in items where the cost of repairing the compressor is generally more than the cost of replacing the entire unit (a household refrigerator, for example). The semi-hermetic unit is constructed of a large cast shell with a cover that is bolted on and gasketed. It can be opened up for repair and maintenance. Both of these systems ensure that no gas will discharge. It’s possible to leave them dormant for years and they will still fire right up if you flip the switch. One thing to keep in mind, however, is that sealed refrigeration compressors can totally mess up the entire system requiring the whole thing to be discharged and refilled.
On the other hand, the open system (most often used for vehicle air conditioners) must be used on a fairly frequent and consistent basis as it is designed to keep washing down the seals and gaskets, which are made from natural leather or synthetic rubber, with lubricant. If not, the seals and gaskets dehydrate which results in the gas leaking out. Even with frequent and regular use, an open-compressor system needs regular maintenance as the gas does discharge gradually over time. The big advantage of open systems is they can run off of non-powered systems such as a turbine or the engine of a car.
As with all vital machinery, it is very important to adhere to a routine maintenance schedule, as missing or ignoring problems or symptoms often results in a repair situation that is far worse than it needed to be.