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Concept:
To get a better understanding of how they function, consider the air tool, a device with comparable function.
In an air tool, compressed air enters the smallest compartment of the vane-housing at shop pressure, usually at 90 PSI or higher.
In so doing, it drives the vane mechanism inside the tool in a rotary motion. The compressed air is 'trying' to get from an area of high pressure back to atmosphere, thus moving the vanes as it drives to the exhaust port of the tool.
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Air flows from an area of high pressure to an area of low pressure, so the high pressure air in the small vane-compartment wants to get to the larger area vane, and ultimately, out.
The shaft inside of the vane-housing extends through seals to the outside of the end of the tool, and is attached to tooling on the end. As a result, you get rotary motion of that tooling.
The power that drives the air tool is compressed air.
The same principle works in the Rotary Vane Compressor, though, rather than compressed air being the power source to drive a shaft and do work, often it’s electricity, and the purpose is not to generate rotary motion of a shaft to drive a tool, but use the rotary motion of the vanes to compress air that you then can use to power a huge variety of compressed air-driven equipment.
In-plant installations of Rotary Vane Compressors are most commonly driven by an electric motor.
The external power supply for the Rotary Vane Compressor drives a shaft inside the barrel of the compressor and at the centre of the vane-housing. This rotates the vane-housing.
The vanes, installed in the eccentrically located centre housing, are able to slide in and out and the vane's length depends on where they are in relation to the outer barrel. Centrifugal force presses the vanes against the inner-wall of the outer barrel. This seals each vane against the outer surface, creating relatively "air tight" compartments within.
Where the volume between the vanes is largest, air enters the vane-housing through an inlet valve.
As the center shaft continues to rotate, and since it’s off-center to the cylinder, the succeeding compartments are smaller and smaller as the vanes cannot extend as far, being closer to the outer wall. A higher volume of air compressed into a smaller volume – that’s an air compressor!
When the vane-housing volume is the smallest, the air is as compressed as it can be in the cycle, and it’s released through another valve into a receiver or the shop air mains.
Features / Comments:
Sometimes Vane Compressors are used in higher demand applications. Some Vane compressors don’t have actual receivers, but are designed to run continuously, and only actually generate compressed air when a pressure switch in the system downstream from the compressor “tells” the unit that compressed air is needed. In this case, the air mains in a large plant are, themselves, the reservoirs.
Vane Compressors usually come equipped with an external enclosure, so the compressor looks like a large metal crate. Aside from the cosmetic value, the housing usually provides sound attenuation. It's usually needed.
Rotary vane manufacturers suggest their units are more compact than other types of compressors, yet can provide more compressed air output than similarly sized reciprocating units.
Rotary vane compressors claim a longer life expectancy in continuous duty applications.
Manufacturers claim that Rotary Vane units are easier to service than other types of compressors, and that they are ideally suited for moderate-pressure applications.
It is our impression that rotary vane compressors presently are not the first choice for industrial compressed air supply applications. This type of compressor seems to favour applications to do with specialty gas requirements, hobby trade, pumping, vacuum generation, and other areas outside of industrial compressed air supply.
This is, of course, subject to change, and there's every reason to think that you will find a Rotary Vane type compressor for your application, should you determine that this compressor technology is your first choice.
