Machinery Lubrication

Machinery Lubrication May - June 2018

Machinery Lubrication magazine published by Noria Corporation

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www . | May - June 2018 | 59 ML the process of selecting the right lubricant for your engine. An SAE grade, such as SAE 40, has no single viscosity value. Instead, it denotes a viscosity range with a minimum and maximum limit. Lubricant manufacturers have the freedom to formulate their lubricants within the accepted viscosity range for a specific grade. SAE grades that contain a "W" refer to lubricant viscosity and pump ability at low starting tempera- tures. Lubricants without the "W" designation may be too thick during winter temperatures. Reasons for Low Oil Pressure e oil pressure in an engine can be low for a number of reasons. When the pressure gauge detects low oil pressure, be aware that it may be real or just an inaccurate reading. In any case, it helps to understand some of the most common causes. Not Enough Oil in the Engine Even if the correct amount of lubricant has been added during an oil change, the oil may be unduly consumed due to evaporation, burning caused by worn piston rings, and leaks through the seals or oil plug. Oil consumption increases as the engine ages, so checking the oil level and topping up may be a simple solution. However, if leaks are evident outside the engine or there are oil drops on the floor, the leaking component should be fixed as soon as possible. When an engine is old, it will burn more oil. When the engine consumes a quart of oil every 1,000-2,000 miles, an overhaul is needed. If the oil change interval is over extended, the oil level could be quite low, even if the engine is not very old. erefore, follow proper oil change intervals and check the oil level periodically. Too High or Low Viscosity When oil viscosity is too low or high, it may be detected as a loss of pressure in the oil supply to the engine. Low viscosity generates less resistance to flow through the system, which is translated as lower pressure by the pressure gauge or sensor. Viscosity that is too high may produce greater resistance from the oil being pumped, leading to a lack of lubrication in the system and consequently lower pressure. In an engine, oil viscosity is influenced by the original lubricant viscosity selected, the operating temperatures, the breakdown of viscosity index improver additives and the presence of contaminants such as glycol and soot. e engine or car manual should specify the recommended viscosit y grades according to the equipment's design and the ambient temperatures where the vehicle will be operating. A higher viscosity selection may be a concern, particularly for engine startups in cold weather. In extreme low temperatures, not only must you choose the right lubricant viscosity, but you may also need to use an oil heating system. Low viscosity can be the result of a variety of factors, such as fuel dilution, incorrect lubri- cant viscosity selection, or excessive temperatures due to overloading or a cooling system failure. Apparent Low Pressure In diesel engines, the pressure gauge typically reports real-time pressure in pounds per square inch or bars. Some lubricant manufac- turers produce lubricants with a lower viscosity that is still within the range of the SAE grade. A lower viscosity offers better fluidity through lubrication systems but may result in lower pressure in the pressure gauge. If the pressure is within the normal range, there is no cause for concern. You may find that some lubricants produce higher pressures than others. Engine Wear If the oil level on the dipstick is between "add" and "full," a possible cause of low pressure would be worn engine bearings, especially if the engine has very high mileage. Excessive wear reduces the original flow restriction, which consequently drops the pressure. If this is the case, the engine likely will need to be rebuilt or replaced. Defective Oil Pressure Gauge If the oil pressure warning light has come on but you have confirmed that the oil level is correct and the engine is running normally with no unusual noises or high tempera- tures, the problem may be a defective sensing unit. You may wish to have the oil pressure tested with a gauge. If the pressure is normal, simply replace the oil pressure sensor. However, if the warning light or low gauge reading continues after replacing the sensor, the problem is likely a bad oil pump. Pump Wear If the oil level on the dipstick is between "add" and "full" but the engine is running noisily, the oil pump may be worn. A worn pump is unable to generate the necessary pressure due to internal leaks. Stop the engine until the issue can be fixed. A pump replacement will be needed. Plugged Filter In a lubrication system, the pres- sure gauge is installed after the filter. If the filter becomes clogged with contaminants and the bypass valve does not operate correctly, it may lead to lubricant starvation. A clogged filter is often the result of an overex- tended oil. It may also be caused by water and/or soot contamination. Water typically comes from a cooling system leak, while excessive soot may

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