This web site has been created to help all Instrument Engineers to view,contact and correspond with Instrument vendors and to know the technical details on Instrumentation world.This web site was developed by the under signed, who is an Instrument Engineer, Graduated from from PSG College of Technology.,Coimbatore.,India is serving the world of Instrumentation for the past 2 1/2 decades.Suggestions are welcome to improve the site. I thank tripod for giving me an opportunity to use their web site for creating this web site.Please contact me at the email metioned below.
L.N.Ramachandran
Details on Instrument Air Compressor
This is to give the fundamental details on instrumentation and this is basically to guide the new students who can be explained the requirements of Instruementaion.
Instrument Air Compressor
Instrument Air compressors are installed in plant to provide Instrument air to the plant field Instrumentation. Normally the compressor is Receiprocating compressor with two stages.The pressure normally delivered would be in the range of 100 psig.The Instrument air compressor or non lubricant rype and of three stages. The Compressor has lube oil pumps and cooling water system to cool the engines. Some compressors have air cooled system.The folllowing gives the basic diagrams of compressor along with connected instruments.
Basically the Instrument devices are as follows:
Low lube oil Pressure switch
Low cooling water flow switch
Stage high Temperature switches (normally 3 stges)
Loading Unloading Solenoid valves.
Pressure and temperature Gauges to show Pressure and Temp values.
Logic panels are installed to handle the logic with switches and relays.
Normally as soon as the start command is given the compressor starts in unloaded state with Lube oil timer acted. When the lube oil pressure raises more than 15 psi the timer cut off and the low lube oil pressure safety is introduced.After few minutes of running the compressor loads automatically by energisng the solenoid valves.The Proction such as high discharge temparature and low cooling water flow are in line for protecting the compressor.The compressor goes in loading unloading depends on the dischage pressure of compressor.
Normally two compressor will be in the system. One will be in duty and other as standby. The selector switches are provided for choosing any compressor in duty or standby. Sometimes this is also called lead and lag. Normally at 110 psi both compressor in unloaded state and between 90 and 110 one compressor swings between load and unload. ie at 90 psi loads and 110 psi unloads. In case the demand incleases and the pressure drops below 80 psi the second compressor comes in line and at 100 psi the compressor which is in lag will unload and stoped after a while and time is set by timer in control logic.The control logic can be 220/110Vac or 24V DC.
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