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2016WinterShotcreteEMag

Nozzleman Knowledge output within the dusty air conditions of shotcrete placement. Imagine how long our work trucks would last if they were operated continuously at full speed within these conditions. Scheduled maintenance may not be enough. Because of the special needs of shotcrete air compressors, on-job personnel should be able to inspect and perform several simple but necessary inspection and maintenance steps. Air Compressor Basics A compressor head unit is coupled to the back of the engine. Engine rotation spins a pair of rotors within the compressor head at double the engine speed to compress filtered incoming air. Compressor rotors rotate within a precision housing at very close tolerances. Intake air must be clean or excessive wear will occur. The rotors are lubricated and cooled by a non-foaming lubricant (usually automatic transmission fluid) mixed with the incoming air. Next, the lubricant is removed from the compressed air as it passes through a filter/separator assembly. The filter/separator, like other filters, must be replaced routinely. It is easily identified within the compressor unit because it is contained within a tall, pressurized cylindrical tank (Fig. 1). As air is compressed, its temperature rises dramatically. This is normal and is referred to as adiabatic heating. Adiabatic heating occurs when a gas is compressed. To cool the hot air, it passes through a large intercooler (air-to-air radiator) at one end of the unit. An engine-driven fan pushes fresh air through all of the intercoolers to remove heat from the engine, compressor oil, and the compressed air (Fig. 2). An adjustable pressure regulator controls the pressure and volume of the discharged air. Modern compressors use sensors and a micro-processor unit to control engine function and emissions. Gauges display vital engine and compressor functions. The engine and all of the compressor components are contained within a special sounddeadening enclosure that is designed to draw fresh incoming air through openings at one end and push heated air out the other. Unlike older compressors, opening the doors of a modern air compressor while it is operating defeats the sounddeadening design, interferes with air flow to the cooling system, and may cause overheating. Like modern automobiles, today’s compressors are more reliable, efficient, and generate lower emissions than previous models. But, like the automobile, reliable operation will be short-lived without maintenance. Fig. 1: Due to high compressor pressure, filter/ separators are contained within a vertical steel tank near the compressor head unit Fig. 2: A cooling fan forces fresh air through the engine’s radiator and various heat exchangers Shotcrete • Winter 2016 43


2016WinterShotcreteEMag
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