Troubleshooting Marine Compressors
Though the problems encountered onboard differ from ship to ship, a brief guideline is given regarding the causes of the different symptoms.
1. Lube oil pressure low: causes can be leakage in pipes, suction strainer choked, oil grade wrong, gear pump faulty, faulty pressure gauge, increased clearances of the bearings, and oil level low.
2. Cooling water high temperature: causes can be cooling water valves closed, cooling water piping blocked, cooling water pump belt lose or broken, cooling water pump faulty, no flow of cooling water, and low level of cooling water in the expansion tank.
3. Compressor noisy: causes can be bearings worn, crankshaft end play high, discharge pressure high, poor foundation, small bumping clearance, piston rings worn, liner worn out causing piston slap, valves not properly seated, and valves broken or faulty.
4. First stage discharge pressure low: causes can be that the first stage suction valve is not closing fully and allowing the air to leak during the compression or it is not opening fully allowing less air to come in the chamber or the discharge valve is faulty and opening prematurely or incorrect springs have been fitted which are compressing on little pressure, intake filter fouled, leakage from piston rings.
5. First stage discharge pressure high: causes can be that the second stage suction valve is not holding and while compression high pressure air is coming to the inter-cooler and showing an increase in the pressure, inter-cooler tubes choked.
6. Second stage discharge pressure low: causes can be leakage from the piston rings, second stage suction valve faulty and allowing the air to escape, second stage discharge valve leaking or opening prematurely due to wrong springs fitted.
7. Second stage discharge pressure high: causes can be obstruction in the after cooler, obstruction in the discharge valve, air bottle pressure high, second stage discharge valve springs very stiff.
The above is just a brief exposure to the problems encountered onboard and how it must be investigated. An experienced marine engineer keeps an eye on the parameters and knows when maintenance is expected.