Engine Lubrication Page 3

OIL COOLER :

An oil cooler is provided to cool the lubricating oil in heavy duty engines Where duty engines where the oil temperature is likely to become very high. It is necessary to keep the oil in the lubricating system cool because the viscosity of the oil decreases with the rise in temperature. An oil cooler is like a heat exchanger. The oil may be cooled either by cold water or the air stream. A water-type cooler as shown (In the picture) consists of tubes in the casing of the cooler. The heat of the oil is taken by the criculating water.

OIL PRESSURE GAUGE :

There are two types of oil pressure gauges- bourdon tube type and electrically operated type. The latter one is more widely used. An electrical resistance type gauge is shown in (the picture) . It has two units-engine unit and dashboard unit. The engine unit is fixed on the oil gallery. It consists of a variable resistance linked to a spring-loaded diaphragm. When the pressure on the diaphragm increases, the resistance decreases. The reverse action takes place when the pressure on the diaphragm decreases. The variable resistance in connected in series with a bimetal element placed in the gauge unit and is connected to a constant voltage supply. The variation in resistance causes variation in current with the increase or decrease of oil pressure. The increased current causes the needle to move towards the increasing graduation on the gauges unit due to heating effect on the bimetallic element. In some gauges units, the magnetic effect instead of heating effect is used.

OIL PRESSURE INDICATOR

It consists of tewo units- engine unit and dashboard unit. The engine unit consistsof a diaphragm-operated switch, which is connected in series to a light on the dashboard. When starting the engine, the cricuit is closed so that the light comes on. After some time, when the oil pressure buid up, the diaphragm opens the switch and the light is turned off. If the oil pressure fails to build up, the warning light stays on and this indicates to the operator that there is something wrong with the lubrication system. In such a case the engine should be shut off immediately.(in the picture oil pressure indicator) shows an oil pressure indicator system.

OIL-LEVEL INDICATOR :

The amount of oil the crancase is determined by means of a spash stick a long flat rod, which dips into the oil through a tube at the side of the crankcase.