In order for ships air compressors to work effectively, at any time, you should know what the most common problems can occur and their causes. You need to know how to take care of vents; How to hold and replace the air valves; Maintenance of pneumatic cylinders and pistons; And like the bearings adjust, crank pins and links. You should be able to replace and repair the lubrication , cooling, control and air systems.
A clean, dry air is essential to the proper operation of the compressors. To do this, the air intake filters should be regularly inspected and cleaned; If the filter is clogged there is a loss of capacity. A clogged air screen or inlet filter can also lead to extraction of oil from a compressor crankcase, around the rings or through oil seals to cause an explosion. Remove the filter element and clean with a jet of hot water or steam or by immersing in a strong solution of sodium hydroxide. The filter housing must be drained and replaced. When the filters are soaked in oil, dipping in clean oil, intermediate and complete emptying must be done before the filter at the inlet changes. Do not clean the filter with petrol or kerosene! Vapors can accumulate and explode in the compressor or the receiver. Make sure that no rain or dew on the inlet side be present and a means to drain the water from suction tube be provided. The lines should be as short and direct as possible. To supply air compressor air to the divers, avoiding compressor absorbs every internal combustion engine exhaust. You should also avoid possible inlets fumes from the fuel tank, spilled oil or gasoline.
The inlet and exhaust must be clean and kept in good condition. The valves if have leakage are generally contaminated and cause a loss in capacity. Valves are removed by loosening the fastening screws or clamps and then removing the cover plates. Each relief valve , if provided, can be lifted. Each valve should be checked to ensure that it returns to the same port from which it was removed. The valves removed for inspection should not be removed for cleaning if the conditions so require. Usually, dirt or carbon in the valve hole can be removed without removing the valve. This is done by soaking the valves in kerosene, then giving a stiff, light brushing or light scraping. The action of the valve is to be tested by inserting a screwdriver through the seat opening; The valve must lift and close freely. If necessary, remove the valve, check the arrangement of the various parts so that the corresponding relationship is maintained with the valve assembly. (The periodic reports on board show damage to the piston and valve parts if connected poorly mounted valves in the way of the piston lugs protrude.) Before replacing the cylinder in a cylinder, replace the air valves, check the seals and replace them. Plates coated with copper or asbestos thin and thin copper. Alternatively, they can be used together of compressed asbestos temporary 1/16 inch. Each valve assembly is inserted into the same hole that has been removed. Since it may be difficult in many cases to distinguish between the suction valve and the pressure valve, care must be taken when the valves are inserted into the cylinder. Make sure the suction valves are open to the center of the cylinder and exhaust valves are clear. Failure to do so will result in serious injury or loss of capacity. Then, the valve cap in the cylinder ensures that the gasket is in place; Lower even coverage of nuts and again do not tilt the lid. Tighten the set screw of the valve or clamping screw, pulling the valve in its seat. If no special lock in the threads of the screw of the valve to prevent leakage leakage must be placed through a locking nut in a recess around the screw and placing welding or fuse wire.
CYLINDERS AND PISTONS
The cylinders on pistons should be inspected only AFTER the manufacturer’s technical manual has been consulted. Be careful when removing heads, particularly where metal-to-metal joints are involved, to prevent damage to the joint.
If replacement of piston rings is required because they are worn or broken, take accurate measurements of the cylinder liners. Standard size rings may be used in oversize cylinders if the oversize does not exceed 0.003inch per inch of cylinder diameter. The liner may also need to be replaced if it is badly worn or out of round. When replacing piston rings, first fit them to the cylinder to check for proper end clearance. You can file the ends, if necessary, to make them fit. The side clearance of the rings should be such that the rings will fall easily into the piston grooves, which should be deep enough for the ring thickness. Ring splits should be staggered. After you assemble the piston, wire the rings tight with a soft copper wire so that they will enter the bore easily. This wire can be removed through the valve ports after the ring has started into the cylinder bore.
When reassembling the air cylinders and heads, be sure they are all drawn down evenly, especially on multistage compressors where the heads contain cylinders for third and fourth stages. Otherwise, the result will be excess wear on the cylinders and pistons.
When a compressor piston has been replaced, the piston end clearance must be checked. This is done by inserting a lead wire through a valve port or indicator connection. Jack the compressor over. When the piston has moved to the end of its stroke, the lead will be flattened to the exact amount of clearance. The wire should be long enough to permit a reading near the center of the piston. These readings should be taken after any adjustment or replacement of the main, crank pin, wrist pin, or crosshead bearings. Methods of adjusting the clearances vary according to the compressor design. You should consult the manufacturer’s instructions for suggested adjustment.
From time to time other miscellaneous adjustments are required on compressors, including those pertaining to wrist pins, crosshead shoes, reduction gears, couplings, and V-belt drives. The manufacturer’s technical manual will give you specific information forth care, adjustment, and replacement of all fitted bearings. Refer to the manufacturer’s instructions for detailed information on when and how to make these adjustments.
Wrist pin bushings are replaced when necessary. This is done when they are worn to the point of becoming noisy. In making a replacement, be sure the oil hole in the bushing is properly lined up with the oil hole in the connecting rod. After being pressed into the rod, the new bushing must be reamed.
Crosshead shoes are provided with shim or wedge adjustment. Wear should be slight, but adjustment should be made when the travel of the piston rod causes movement in the stuffing boxes.
Alignment of reduction gears and pinions should be checked periodically, especially on a new compressor. Misalignment may be caused later by settling, straining, or springing of foundations; pipe strains on turbine-driven compressors; bearing wear; or springing due to heat from a turbine.
Flexible couplings require very little maintenance when they are properly lined up. Some types require occasional lubrication to prevent excessive wear of springs and bushings. A noisy coupling is an indication that the bushing is worn and requires replacement.
V-belt drives require adjustment for belt tension. Belts generally stretch slightly during the first few months of use. A loose belt will slip on the motor pulley and cause undue heating and wear on the belt. A tight belt will overload the bearings. Belts should be protected against oil and high temperatures. To prevent rapid deterioration, belts should not be used at temperatures above 130°F. V-belts are usually installed in sets of two or three. If a single belt is worn or deteriorated, the complete set should be replaced to ensure that each belt will carry its share of the load.
Proper care of a compressor lubrication system includes the following:-
- Keep the oil at a normal level in the reservoir at all times to maintain proper oil temperature.
- Change crankcase oil periodically, and at the same time clean and flush the crankcase and clean the oil filter.
- Maintain proper lube-oil pressure by keeping the oil pump in good working order and adjusting the bypass relief valve.
- Keep the oil cooler free from leaks (since pressure on the water side exceeds that of the oil) to prevent oil contamination and emulsification.
- Properly adjust the lubricator for the specified quantity of oil feed.
Proper care of a compressor cooling system includes the following inspections and maintenance procedures:
- Periodically inspect the intercoolers and aftercoolers
- Remove collections of gummy oils or tarry substances from the cooler tubes by washing tube nests with a suitable solvent and drying them thoroughly before reassembling.
- Correct any leakage in tube nests to prevent leaks of water into the compressor while secured or leaks of air into the water side during operation.
- Inspect and clean the cylinder water jackets periodically with a cleaning nozzle.
When filling the cooling water system after the compressor has been drained, open the water inlet slightly to allow the water to rise slowly in the cooler shells and water jackets. Vent valves fitted to the water spaces should be opened to permit entrapped air to escape and to remove any air pockets.
Because of the great variety of regulating and unloading devices used on compressors, you will have to consult the manufacturer’s technical manual for information regarding the adjustment of these device son particular compressors.
If a control valve fails to work properly, it should be taken apart and cleaned Some valves are fitted with filter filled with a sponge or woolen yarn to prevent particles of dust or grit from being carried into the valve chamber. These filters remove gummy deposits from the oil used in the compressor cylinders. When repacking, use only genuine wool. Cotton will pack and stop the airflow. Relief valves are very important for safe compressor operation. They should be set as specified by the manufacturer and lift-tested by hand each time the compressor is placed in operation. To check the setting periodically, test by raising the pressure in the spaces to which they are attached.
Since an Engine man may encounter so many types of compressed air systems, air dryers, and air compressors both ashore and aboard Navy vessels, this chapter presented only general procedures and facts. To maintain, repair, and overhaul specific compressed air systems, air dryers, or reciprocating air compressors, you must refer to the manufacturer’s technical manuals. A definite preventive maintenance schedule with frequency and assignment of responsibility is required. You should have the manufacturer’s manual handy to establish minimum requirements and to follow its recommendations for maintenance.
Author Amit Article Requested By: Rauhjek