Compressed Air Systems

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

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

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

Positive Displacement • 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 impeller (low press/ high CFM applications) • 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

Questions?

Compressed Air Systems