Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/1222953
32 | March - April 2020 | www . machinerylubrication.com BEARING LUBRICATION determined primarily by the pump's capability. Adjusting the bypass relief valve so less oil passes through to the bearing will increase system pressure. Pumps and Motors Motors are available in different voltages, frequencies and phases to best suit the available power sources. e typical motor is rated as TEFC (totally enclosed, fan cooled) and is suitable for many industrial environments. A system located in an area with combustible vapors and dust may need to be rated as explosion proof. e class, division and group must be identified for an explosion-proof motor. Filtration A circulating oil system typically uses three methods of filtration. e reservoir is equipped with a baffle that partially separates the two sides. e fluid comes into the reservoir on one side of the baffle where sediment tends to settle. e oil passing over the top of the baffle benefits from this initial phase of passive filtration. As the fluid is drawn out of the reservoir, a second level of filtration is achieved when it passes through a mesh strainer. Final filtration occurs prior to the fluid exiting the system, usually with something like a 23-micron filter. It is advisable to clean the strainer and change the filter on a regular maintenance schedule. Gauges e gauges on a circulating oil system offer a means of moni- toring the operating conditions. A pressure gauge between the pump and bypass relief valve is used to verify that the pump is operating as intended and that the bypass relief valve is preventing excessive pressure buildup. e temperature of the fluid in the tank is visible using a thermometer built into the liquid-level gauge. A temperature gauge installed in the piping gives feedback on the temperature of the fluid after passing through a heat exchanger. A differential pressure gauge is used to measure the amount of pressure lost while passing through the filter. Loss of pressure indicates the filter may need replacing. Switches Signals obtained from switches can be interpreted by electronic controls to send information to monitoring stations, manage how the unit functions, activate alarms or shut down equipment. A temperature switch provides the ability to signal a high tempera- ture or activate the heat exchanger. A liquid-level switch can indicate that the oil level in the tank is low because of system loss or because fluid is not returning fast enough from the bearing. A liquid-level switch can also be used to signal when the tank level is high due to an unexpected restriction of flow in the piping or at the bearing. Figure 4. Examples of an air-cooled heat exchanger (top) and a water-cooled heat exchanger (bottom) Figure 5. Elevation and venting of a circulating oil system Needle control valve at bearing inlet Vented return line Return line pitched toward circulating oil system Travels under pressure Returns via gravity Cooled oil exits Hot oil enters Hot oil enters Cool water enters Cooled oil exits Used water exits