COOLING SYSTEM

The generation of heat always accompanies the compression of air. In most low-pressure air compressors, the heat from compression is dissipated before the temperature gets too high. Aluminum cylinders have cooling fins, and a fan forces cooling air past the cylinders. In most medium-pressure and high- pressure air compressors, the compressor has to be cooled with pump-circulated water. The cooling water is circulated in much the same fashion as in an automobile engine with the coolant passing through jackets in the cylinder walls, cylinder heads, and so on. In addition, compressors are fitted with other cooling devices, known as intercoolers and aftercoolers. Generally, these devices consist of a series of tubes, either air-cooled or water-cooled, through which the compressed air charge flows after leaving the cylinders. These devices cool the compressed air. INTERCOOLERS are placed between the stages or cylinders of multistage compressors. Thus they cool the compressed air charge before it is drawn into the next cylinder. The AFTERCOOLERS cool the final discharge of air from the compressor. Both the intercoolers and the aftercoolers are of the same general construction, except the aftercoolers are designed to withstand a higher working pressure.

Perhaps the most important advantage of these coolers is they aid in keeping the air charge in a compressed state. In other words, hot air has a tendency to expand, and if the compressed air charge is not cooled, it, too, tends to expand and thereby liberate much of its pressure or energy.

COMPRESSOR LOCATION

Locate the compressor unit so that it is reasonably level. The design of this unit permits a 15-degree lengthwise and a 15-degree sideways limit on out-of- level operation. The engine, not the compressor, is the limiting factor. When the unit is to be operated out of level, keep the engine crankcase oil level near the high level mark (with the unit level) and have the compressor oil gauge show nearly full (with the unit level). The mechanical parking brake lever is near the bumper. Set the brake by pulling or pushing the lever as directed by a decal or a stencil located beside the lever on the unit. The parking brake should always be set once the air compressor is on location to prevent accidental rolling of the unit, which could cause not only mechanical damage but also possible injury to 6-47 personnel. As an added precaution, the wheels should be chocked when possible.

Open the side curtains on both sides of the enclosure and leave them open whenever the unit is in operation. When the side curtains are closed and the engine running, the flow of air through the oil cooler and engine radiator is restricted. The curtains may be left closed for a few minutes during starting procedures in cold weather to ease engine warm-up. However, when the compressor goes to work, open the side curtains. For specific operating instructions, check the instruction plate attached to the unit being used.

ENGINE

The heart of the compressor is the engine that furnishes power for the compressor and produces air for the pneumatic tools used during drilling. Know how to start, operate, and maintain the compressor engine properly. In most cases, the general operating procedure is similar to that given below.

Check the engine oil level. If necessary, add oil as recommended in the engine manual. Do not overfill. Check the engine cooling system. The radiator should be filled to the bottom of the filler neck. If necessary, add soft, clean water until full. In cold weather, use a permanent antifreeze with a rust inhibitor. Ethylene glycol solutions are recommended because they do not evaporate and only water is added to maintain a full system. Two fuel tanks are furnished-one on each side. The two tanks are cross- connected to permit filling from either side of the unit. Clean fuel is vitally important. Ensure clean fuel is poured or pumped into the tanks. Be sure no condensate (water) lies in the bottom of the fuel tanks. Drain off any water that may be there. Clear away obstructions in the vents of the fuel tank.

Lubricate all parts of the engine as recommended in the manufacturer's engine manual. Make periodic checks of the oil filter, the fuel filter, and the fuel oil pump screen. Ensure the rain cap on the exhaust pipe swings freely,, so a back pressure on the engine exhaust cannot be created. Check the battery cells for the proper liquid level. A pair of two-stage dry-type air cleaners filters the intake air for the compressor suction and engine air-intake manifold. Both cleaners are under the canopy at the compressor end of the unit.

The first stage of the air cleaner uses centrifugal precleaning which rotates the intake air and separates a large portion of the dust collected in the dust cup. The dust cup should be checked and emptied daily.