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Air compressors are to be operated and maintained as per maker’s recommendations. CE to ensure that all the engineers are familiar with operation of air compressors and line up of the pneumatic system Watch keeping engineer must ensure that compressor unloaders are operating properly and are not leaking. CE must ensure that LO consumption is within the maker’s prescribed limit. Any increase in LO consumption is indication of
• Wear down of the oil scraper ring of the piston/s
• Oil separator (in screw compressor) is not working properly.
Carryover of oil to air reservoir is serious as it can lead to starting air explosion of ME during manuvering. Also carry over of oil will lead to carbonisation of oil at the valve plates thereby decreasing the compressor efficiency.
Once in 3 months compressor efficiency/performance should be tested by running the compressor to fill up empty air reservoir and record total time taken to fill the bottle. Non return valves on discharge line of the compressor is to be checked at least at interval of 6 months.

The air reservoirs provided are normally designed to meet the following requirements:
Propulsion engines reversible = 12 starts
Propulsion engines, non-reversible = 06 starts
Engines for driving electric generators and emergency generators, and engines for other purposes = 03 starts each

• To ensure above capacity is maintained, ensure that drains of air reservoir are tight and not leaking. Drain valves/ auto drains are to be maintained as per maker’s guideline.
• All efforts to be done to reduce the condensate accumulation in the air reservoir. This will also help in clean and healthy pneumatic system/ machinery.
• Prior start of manuvering condensates of air reservoirs must be drained manually.
• One air reservoir must be fully pressed up, isolated and kept as standby.
• Emergency air reservoir must be kept pressed up at all times.
• Air compressors are to be maintained in accordance with PMS routine and maker’s guidelines.
• Office permission is required for carrying out maintenance works, exceeding 2 hours, on the emergency air compressor.

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WORKING PRINCIPLE

The main air compressor takes suction from the atmosphere, via suction filter.
On LP piston downwards stroke, the suction valve opens while the delivery valve is closed.
On LP piston upwards stroke, the air is compressed. When the compressed air pressure overcomes the delivery valve’s spring tension, the delivery valve will open.
The air will flow through the 1st stage cooler.
On HP piston downwards stroke, the suction valve opens while the delivery valve is closed.
On HP piston upwards stroke, the air is compressed. When the compressed air pressure overcomes the delivery valve’s spring tension, the delivery valve will open.
The air will flow through the 2nd stage cooler and towards main air receiver.

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