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Screw Compressors - engineered for performance
Screw compressors generally come in two basic designs: dry screw compressors or wet/oil-flooded screw compressors. Both compressor types consist of rotors that are closely mated. Dry screw compressors do not have any oil in-between the screws. A dry screw compressor consists of two rotors, a closely mating pair that are installed in a tight clearance cylindrical bore. Wet or oil-flooded screw compressors have oil in-between the screws.
An oil-flooded screw compressor also has a pair of closely mating rotors that are installed in a tight clearance cylinder bore; however, oil-flooded screw compressors do not require clearances to be as tight as those that are required for the dry screw compressors. The subsequent sections of this chapter describe the various aspects (similarities and differences) of these two types of screw compressors.
In a typical screw compressor there are two screws (male & female) that are fitted together in stationary housing. As the rotors rotate, the air of gas is compressed by direct volume reduction between the two rotors.
These compressors are semi-hermetically (bolted together), allowing easier repair work to be carried out. There are also a hermetic compressors, which are usually designed for specific needs and requirements.
They are good energy conservers – Rotary screw machines are generally energy efficient, and they generate less heat than normal air compressors. They consume less oil than other oil flooded air compressors. In addition, they have minimum oil carryovers.
Screw compressors offer higher capacity output; larger compression ratios and smoother control to deliver energy savings in large applications. As an evolution of the compressor, they are more modern and, with fewer moving parts, require less maintenance.
Semi-Hermetic Screw Compressors
This is one type of screw compressor. They are efficient, robust and durable. The screw compressor is design for 100% duty cycles and are built for work.
With a broad range of compressors now existing in the engineering world, one common way to differentiate them is by the way in which they are designed.
The word hermetic is derived from the word hermit, meaning to be isolated from the outside world and similarly, hermetic means to be tightly sealed. Hermetic seals in engineering terms therefore refer to airtight seals used to maintain a closed system of operation.
A hermetic compressor, by definition, is when the main compressor and the engine are both sealed inside the outer casing so that they can operate in an isolated environment. As such, this term is used to categorize compressors into three distinct types:
An open compressor unit is the most common type, as the engine and the compressor are separate entities and a semi-hermetic compressor is a unit that therefore features elements of both designs. With the body of the compressor along with the engine sealed inside the casing during operation, but in such a way that it can be opened for inspection and maintenance if and when needed.
Screw and Reciprocating Compressors - are available in Semi-Hermetic, Hermetic and Open options.
Advantages of a Hermetic System
One major benefit of having the mechanical process sealed during operating conditions is the protection from contamination of the closed system. By preventing air into the system, dust particles are unable to dirty the lubricant and the moving parts which would in-turn cause increased deterioration of the components and a shorter lifespan.
Often incorporating a simple design, hermetic compressors are often able to run at a lower level of running cost, although this is often at the price of increased noise and vibration compared to open compressors. As such, they’re suitable for non-intensive purposes, such as the circulation of gas and liquids around a closed system that makes them ideal for use in temperature control equipment. As a fully hermetic system can’t be opened, this does limit them to a short to medium term lifespan, as they need to be completely replaced if a problem occurs to them.
PCE Repairs all Types of Screw Compressors
Comprehensive services are carried out on all leading brands of screw compressors, to OEM standards and with OEM parts. They carry the same 12 month Guarantee that an OEM product would offer too.
Our workmanship is guaranteed
Our repaired and exchange units carry the same one year warranty as the original manufacturer. We also offer an extended warranty.
Serving a wide market
Our client base includes government, semi-government organisations, supermarket chains, shopping centres, mining houses, hospitals, refrigeration and air-conditioning companies, as well as professional maintenance companies and consultants.