Tools Air Compressor

Air Compressor How it works .Compressed air supply equipment explained, use and types for automotive use.

Guide 

The compressor may be a screw, vane or reciprocating piston type. The piston main airline type is often used in the paint trade or for air tools in the general automotive repair shop and DIY home use, although very large and continuous air demands can be economically met with the modern screw and rotary types with reduced noise levels.

The compressor must be of sufficient capacity to cater for work loads. The output rating in cubic metres, litres or equivalent cubic feet, per minute, must be calculated on the basis of actual total air consumption when all equipment is in use.

Compressors may be rated according to piston displacement, displacement at a specified pressure, or free-air displacement at various speeds. The rating which equates to actual output is the free-air displacement at operating speed as this will depend on the volumetric efficiency, which is approximately 75 per cent of the piston displacement for single-stage compression and 85 per cent for two-stage.

For pressures under 5.95 bar (85 psi), single regulated air stage compression is normally used; when pressure requirements are higher, greater economy and efficiency is obtained with a two-stage compressor. With two-stage compression, less power is required; nevertheless, the drive motor power rating can be regarded as an approximate guide to actual air delivery The compressor pressure rating or working air pressure must be selected to maintain a minimum pressure which is equal to the highest-pressure requirement of any equipment in the range to be used. On larger-capacity compressors and when there is continuous air demand, it is advantageous to have an automatic unloader control mechanism which will allow the motor to idle without load when the required pressure is developed in the system and to reload the compressor when the air pressure drops. Auto-Matic start and stop facilities are normally fitted to small compressors for which the air demand is intermittent. Dual-control versions may be used when demands fluctuate.

These are fitted with automatic start/stop and load/unload controls with a time control to stop the compressor when a predetermined motor idling period (unloaded conditions) has elapsed. When there is a high usage of compressed air, as in large refinish premises, an effective cooling device is essential to reduce the temperature of the compressed air and to obtain maximum moisture separation from the air.

Compressors must be sited in a cold area with cold air intake as hot environments and inlet air will reduce efficiency.

• Weekly check
  Compressor oil level, safety valves.
• Monthly check
  Intake filter, external cleanliness (to aid cooling), lubrication and cleanliness of electric motor, tightness of bolts, fittings, etc.
  The compressor reservoir must be of sufficient capacity to eliminate air pressure fluctuations