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2016WinterShotcreteEMag

Nozzleman Knowledge Watch For Compressor Warning Signs It is normal for compressed air discharge to be warm, but very hot discharge air may be a sign of initial mechanical malfunction. Very hot discharge air is the first warning sign of an overheating condition. If ignored by on-job personnel, overheating can cause almost immediate engine, compressor head, or filter/separator damage. Excessively hot discharge air can be caused by clogged filters, low compressor head oil levels, excessive tolerances within the compressor head, or plugged cooling fins within the cooling system. If heat cannot be released as quickly as it is created, the compressor will begin to overheat. By far the most common cause of excessively hot discharge air for compressors used in shotcrete service is dirty filters or partially clogged cooling system exterior fins. Because of the shotcrete environment, oil, cement dust, and dirt tends to quickly plug filters. Dirty air, drawn by the engine’s cooling fan tends to build up and clog some (or all) of the cooling system’s exterior fins. Check for clogged fins by looking at them through the protective fan guard (Fig. 6). Keep cooling system exterior fins clean by routinely flushing the sticky residue out of the cooling fins with plenty of water. The amount of trapped material released during flushing can be surprising! Modern compressors use protective heat sensor safety switches that will shut down the compressor if an overheating condition is occurring. If very hot discharge air is detected, or a shutdown occurs, check for clogged cooling fins, dirty air filters, or low compressor head lubricant. A common warning sign of potential compressor failure that on-job personnel should watch for is an oily odor in the discharge air. Because shotcrete service compressors normally operate at near-full-throttle conditions, the filter/ separator assembly is prone to failure. As media material within the filter/separator breaks down, its effectiveness at removing all oil from the discharge air diminishes. Not only are filter/ separators susceptible to damage from heat and full throttle use, they can be permanently damaged by improper on-job compressor shutdown procedures. To avoid damage, compressors should be idled for a few minutes following full throttle use to cool engine, compressor, and turbocharger components, then shut off. Compressors are designed to automatically bleed stored compressed air SLOWLY after shutdown. Never throw open an air valve to drain stored air. A sudden collapse in internal pressure can distort and permanently damage the filter/separator assembly. If an oily odor is noted in the discharge air, discontinue use and replace the filter/separator. A compressor failure during shotcrete operations can occur at any time. Fortunately, compressors often display warning signs well Fig. 5: The air compressor’s battery is often in a difficult-to-reach area Fig. 6: Cooling fins clogged with dirt and oil area common cause of overheating Shotcrete • Winter 2016 45


2016WinterShotcreteEMag
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