INSTRUMENTATION AIR COMPRESSOR
In an instrumentation industry the field control devices like control valves are mostly pneumatic instruments, which need pressurized air to operate. An instrument air compressor controls and supply air for operating valves in pneumatic instruments. Air compressors ensure that the air passing through to power these process control equipment is of the correct pressure and temperature.
COMPONENTS OF AN INSTRUMENTATION AIR COMPRESSOR :
• PRE FILTER • COMPRESSOR • DRYER • AFTER FILTER • BUFFER VESSEL • DISTRIBUTION SYSTEM
• PRE FILTER
Air inlet of air compressor is connected to the pre-filter. Pre-filter is used to filter out dirt particles from entering air line and connected instruments The Pre-filter are effective solid particle filters, which removes solid particles down to microns from inlet air to compressor.
An air compressor increases the pressure of inlet air by reducing its volume. In air compressor atmospheric air is drawn in through an intake valve via a pre-filter, more and more air is pulled inside a compression chamber mechanically. Since the amount of pulled air is increased in compression chamber, volume is reduced and pressure is raised automatically.
By Compressing Mechanism compressor can be classified as
• Reciprocating type
A reciprocating air compressor use piston to compress air and store it, Reciprocating compressor can be a single-stage or double-stage configuration. In single-stage only one piston is used while in double-stage two pistons are used. Double-stage configuration is used for high pressure.
• Rotary type
In Rotary type there are screw type and vane type
1.Screw type: Spinning helical screws or rotors are used for compressing air, as the screws mesh towards each other; air is compressed and stored inside the tank.
2.Vane type: Here High-speed rotating impeller is used for compressing air, which is directed towards a diffuser that converts the velocity of air into pressure.
During air compression temperature also increase thus we use inter coolers and after coolers in compressor to maintaining the final temperature
During air compression, temperature and moist level of the air increase. To remove the moist from the pressurized air we use a dryer. The most commonly used dryer materials are silica gel and activated carbon.
• AFTER FILTER
Instruments are so sensitive that the air supply of an instrumentation industry should be too clean and the maximum allowable dust particle is down to micron, to achieve this we use after-filter.
• BUFFER VESSEL
A Buffer vessel is an integral and important part of air compressor; it is the reservoir of compressed air. Buffer vessel minimizes pulsation in the air compressor caused by a reciprocating compressor or a cyclic process
• DISTRIBUTION SYSTEM
The Distribution is the last and final stage of an instrumentation air compressor system. Compressed air distribution has the job of transporting the compressed air without losing pressure, quality and quantity of air. Thus distribution has direct impact on the performance of the compressors. so there should be no pressure lose during distribution.