Air systems

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Author:
scott.spears
ID:
161150
Filename:
Air systems
Updated:
2012-07-05 17:51:55
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Air systems
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Description:
Air systems
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  1. How many stages of air compressor are there?
    single and two stages
  2. what are the 3 catergories of air compressors and what pressure are they?
    • low pressure (two stage usually a non-differential piston 150 PSI or less),
    • medium pressure (two stage usually with a differential piston 151 to 1,000 PSI)
    • high pressure (four stage above 1,000 PSI).•Air compressors onboard Army watercraft are the medium pressure type
  3. what are the two cycles of the Air compressor
    •All compressors operate using two strokes (suction & compression).
  4. when does the suction stroke begin
    •The suction stroke begins when the piston moves away from top dead center (TDC).
  5. when does the compression stroke start
    •Compression stroke starts as the piston moves away from BDC and continues until piston reaches TDC again.When the pressure in the cylinder equals the pressure on the opposite side of the inlet valve, the inlet valve closes
  6. what are two types of pistons commonly used?
    •Differential•Trunk Type
  7. What are differential pistons different then trunk pistons?
    •Differential pistons are modified trunk pistons having 2 or more different diameters fitted into special cylinders.
  8. What are some benifits of trunk pistons?
    •TRUNK TYPE distributes the side pressure over a wide area of the cylinder walls.Trunk pistons with long skirts are used¬† to eliminate cylinder wall wear (Side thrust
  9. what is the purpose for the safty valve or pressure relief valve and where is it located?
    •Are constructed to protect the weakest area in the air system so it does not exceed 110% of the maximum allowable working pressure during maximum flow conditions. Usually located before the intercooler to protect from any potential blockage
  10. what are the two types of starting systems and what one does the army use?
    ¬†mechanical load-less starting and hydraulic load-less starting.•Army watercraft use hydraulic load-less starting and dual control.•This feature allows oil pressure to build and lubricate all components before compressing air. Load-less starting is accomplished by connecting a hydraulic valve (un-loader) to the lubrication system.
  11. what is the pressure switch for and what PSI does it work?
    •The Pressure Switch – is automatic in operation and is adjusted to start and stop the unit at the minimum and maximum desired air receiver pressure by cutting in and out the power to the electric motor.Standard pressure switches are equipped with a fixed 30 PSIG differential
  12. what are the two ways of cooling and what type does the army use?
    •Air compressors are also either air cooled or water cooled.•Air cooled models are cooled by cast iron fan blades, incorporated into the drive sheave (pulley), blowing air across a finned intercooler, then across the finned cylinders and cylinder head.•Water cooled models are cooled by circulating cool water first through the intercooler which is an integral part of the cylinders through the water jackets surrounding the cylinders, then through the cylinder head.•Quincy air compressor onboard Army watercraft are belt driven, air cooled units.
  13. what are the two types of lubercation and what one does the army use?
    •Air compressors are either pressure lubricated or splash lubricated.Army watercraft have pressure lubrication
  14. what is the normal oil pressure under normal operation?
    •Normal oil pressure is between 18 - 20 PSIG at rated speed & temperature.•For receiver pressures above 200 PSIG maintain a minimum oil pressure of 25 PSIG.
  15. If the oil is milky in color, what are the probable causes
    •Compressor does not run long enough to get hot and vaporize the moisture•System pressure running back through the discharge valves•Leaking water jacket or cylinder head
  16. What should NEVER be used to clean air filters, cylinders, or air passages
    •Distillate fuel or gasoline•What cools the Quincy Air Compressor?•Air being moved across the compressor by the pulley
  17. •Un-loaders remove all but what type of load from the compressors during start up?
    •Frictional load

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