Compressed Air Systems

1
Compressed Air Systems

• 62B-300

2
PRESSURE CLASSIFICATIONS

• LOW PRESSURE 0-150 PSI
• MEDIUM PRESSURE 151-1000 PSI
• HIGH PRESSURE ABOVE 1000 PSI

3
HPAC COMPRESSOR

• Characteristics
• Motor Driven
• Four or Five Stage
• Oil Lubricated
• Reciprocating
• Water cooled
• High Pressure/Low Volume

4
HPAC Piston Cylinder Arrangement

• Differential Trunk style (Piggyback)
• First and Third stage
• Second and Fourth stage
• Each cylinder is externally water cooled
• Air flow includes a cooler between each stage
• Pistons and rings are oil lubricated

5
HPAC Lubrication

• Piston and Rings (Cylinder Lubricator)
• Crankshaft and Bearings
• Attached gear pump driven by the crankshaft
• 50 PSI normal oil pressure
• Low pressure switch safety device
• High temperature switch safety device

6
HPAC Air Cooling

• Air cooled between each stage
• Coolers have separators at each outlet
• Separators collect condensate and oil
• Automatic drain valve assembly timer controlled
• Also operated by unloading system (compressor at
  full discharge pressure)

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Cooler/Separator
AIR FLOW
AUXILIARY MACHINERY COOLING WATER
WATER REMOVED FROM AIR
8
COOLING SYSTEMS

• FRESH WATER
• Cylinder water jackets
• Provided by attached pump(figure three)
• SEA WATER
• Auxiliary machinery cooling water system
• Firemain backup(figure four)

9
Temperature Monitor

• High temperature alarm system
• Air discharge from each stage
• Maximum of 400o F
• Cooling water temperature of 125o F

10
HP Air System

• Manual or Automatic mode
• at 2850 PSI, compressor starts
• at 3000 PSI, compressor stops
• In manual mode, the compressor must be manually
  restarted

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HP AIR USERS

• Diesel Starting Air (3000/150 PSI)
• HP/LP augment (3000/80 PSI)
• HP/MP reducing
• Torpedo Launch Air
• Missile movement (3000/300 PSI)
• Air Valve operation
• Gun System (3000/1500 3000/1505 PSI)

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HP Air System
13
LP Air System
TYPE I
DEHYDRATOR
AIR RECEIVER
FROM
3000/80 PSI
REDUCER
1 LPAC
TO CONTROL
TYPE II
TO ELECTRONIC
AIR
DEHYDRATOR
DRY AIR
CIRCUIT
VITAL AIR
TYPE I
DEHYDRATOR
AIR RECEIVER
PRIORITY
VALVE
PRIORITY
VALVE
NON-VITAL AIR
2 LPAC
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Main LP Air Branches

• Control Air
• Propulsion plant
• Air operated valves and controls
• Electronics Dry Air
• Type II dehydrators
• Wave guides in radar and electronics systems
• Non-Vital (Ship Services)

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Low Pressure Air Compressor

• Motor Driven
• Two Stage, reciprocating
• Oil Free
• 100 SCFM at 125 PSI

Compressor Location
Main Machinery Rooms Auxiliary Spaces
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Compressors Subsystems

• Seawater Cooling
• Freshwater Cooling
• Condensate Drain System

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Seawater Cooling System
FRESH WATER/SEA WATER HEAT EXCHANGER
AFTER-COOLER
OVERBOARD
INTER-COOLER(S)
FROM AMCW
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Fresh Water Circuit
Expansion Tank
SecondStage Cylinder
FirstStage Cylinder
FirstStage Cylinder
Strainer
Hi-TempShutdown
Thermometer
ThermostaticValve
Water Pump
Fresh Water/ Sea Water Heat Exchanger
19
Condensate Drain System

• Removes moisture from air system
• Collects in low point holding tanks
• Tank for each air cooler
• Electro-mechanical timer regulates blowdown
  sequence
• Condensate drains include monitors for high level
  shutdown
• Can be accomplished manually

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CONTROL SYSTEM

• AUTOMATIC TEMPERATURE SHUTDOWN - STOPS
  COMPRESSOR AUTOMATICALLY WHEN COOLING WATER
  TEMPERATURE RISES ABOVE SAFE LIMITS
• LUBE OIL PRESSURE- INCORPORATES A TIME DELAY FOR
  INITIAL START UP.
• START/STOP CONTROLS - PRESSURE OPERATED SWITCHES
  OPEN OR CLOSE START/STOP CONTACTS AT A PRE-SET
  PRESSURE
• CONSTANT SPEED CONTROLS - REGULATE AIR PRESSURE
  IN THE RECEIVER.
• AIR UNLOADING SYSTEM- USED WITH CONSTANT SPEED
  CONTROL COMPRESSORS. UNLOADS CYLINDER AIR
  PRESSURE

21
Control System

• Several operational modes
• Automatic Start - Pressure actuated (switch)
• High Start - 115 to 125 PSI
• Low Start - 110 to 120 PSI
• Activated by a pressure switch (air system)
• If no demand for air - 6 minutes
• Selector switch

22
Safety Devices

• Low Oil Pressure shutdown (15 PSI)
• Cylinder Water High temp (160o F)
• High Air Temp (any stage 350o F)
• Final Air High Temp (125o F)
• First Stage Relief (40 PSI)
• Second Stage (140 PSI)
• High Liquid level
• Low Air Pressure Alarms

23
Priority Valve

• Protective Valve between Vital and Non-Vital air
  supplies
• Conserves pressure to vital air supplies
• Spring Loaded
• Fully closed at 85 PSI
• Fully open at 100 PSI

Engineering Spaces 80 PSI
Remote Spaces 75 PSI
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LP Air System Pressure- System Setup

• System in Auto- 2 compressors
• Highand Low designation
• Activated by change in receiver pressure
• Maintaining system at 125 PSI (normal)
• Providing all ship services
• Vital and Non-Vital Air service

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What Happens

• 125 PSI- Both compressors unloaded
• 115 PSI- Lead compressor starts
• 110 PSI- Lag compressor starts (both)
• 100 PSI- Priority valve begins to close to
  protect vital air supplies
• 85 PSI- Priority valve fully shut (supplying only
  vital systems)

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Whats Next

• 80 PSI- Engineroom low pressure alarm
• 75 PSI- Fireroom low pressure alarm
• 65 PSI- Master Air Lock (ABC system)
• gt40 PSI- Final control elements go to fail fail
  position
• Local Manual Control
• Plant response is severely limited
• Loss of Electronics Dry Air

27
SAFETY