Compressed Air Systems “…order up a two-can jam in the back of the bus!” - EM2(SS) Barrow

Introduction Air systems are vital to ship operations Starting diesel and gas turbine engines Torpedo ejection Deballasting air (EMBT Blow) Prairie masker Compressed air represents stored energy - capable of doing work at a later point Used extensively both in high pressure and low pressure applications

Air Compressors (PV  RT) Used to compress air from inlet pressure (atm) to a higher pressure (PV  RT) Classified according to: Type of displacement Staging Type of Drive (prime mover) Operating Pressure Capacity

Air Compressors Type of displacement Type of displacement Positive: used for high pressures Non-positive: used for lower pressures Staging Staging Number of compression steps used in compression process Type of drive system Type of drive system Classified according to prime mover (almost all electric motors)

Air Compressors Operating (discharge) pressure Operating (discharge) pressure Low (<151 #) Medium ( #) High (>1000 #) Capacity Capacity Volume of air compressed CFM (cubic feet per minute)

Positive Displacement Reciprocating Piston Reciprocating Piston Piston assembly with valves to control flow Can either be single stage or multi-stage

Positive Displacement Rotary Compressor Rotary sliding vane (not used) Rotary sliding vane (not used) Rotary impeller (low press/ high CFM applications) Liquid piston (not used much)

Positive Displacement Rotary Compressor Rotary sliding vane (not used) Rotary impeller (low press/ high CFM applications) Rotary impeller (low press/ high CFM applications) Liquid piston (not used much)

Positive Displacement Rotary Compressor Rotary sliding vane (not used) Rotary impeller (low press/ high CFM applications) Liquid piston (not used much) Liquid piston (not used much)

Non-Positive Displacement Centrifugal compressor Radial flow Axial Compressor Axial Flow

Support Systems Cooling Most cooled by fresh water systems Remove heat from compression process Intercoolers used between stages Aftercooler used after final discharge Receivers Storage tanks for reserve air capacity Used on ALL compressors to lower pulsations Safety features Auto shutdown

Specific Uses of Air High Pressure Torpedo Ejection Emergency Blow Hydraulics Remotely-operated valves Low Pressure Prairie Masker system Potable water Pneumatic tools & valves

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