Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/1222953
www . machinerylubrication.com | March - April 2020 | 33 ML A low-flow switch activates when flow drops below a desired level. is condition can be caused by a clogged filter, pump malfunc- tion, power interruption or depleted fluid. e signal from the switch can give valuable warning time to take corrective measures. A differential pressure switch signals that the pressure is elevated after passing through the filter. is indicates the filter needs to be replaced. Heat Exchangers e purpose of a heat exchanger is to reduce the temperature of the oil before returning it to the bearing. Heat exchangers transfer heat from the fluid to either the air or to water (Figure 4). An air-cooled heat exchanger uses a fan to blow air over the oil as it passes through a series of smaller tubes. e tubing for a water-cooled heat exchanger is routed through a cylinder that has a contin- uous supply of water passing through it. e heat exchanger is sized to the number of British thermal units (BTUs) required to be removed per hour. is is calculated using the temperature of the oil as it exits the bearing and the temperature required when returning to the bearing. e heat exchanger size is dependent on the air or water available for cooling. An air-cooled heat exchanger cannot reduce the oil temperature to less than the surrounding air temperature. Warmer ambient temperatures will create the need for a larger heat exchanger. A water-cooled heat exchanger offers increased efficiency with a lower water temperature and a higher flow rate of water. Heat exchangers can be manually operated by an attendant or controlled automatically using a temperature switch or readings from a temperature gauge. ey can also be wired to operate continuously. Immersion Heaters An immersion heater works in contact with the oil in the system reservoir. It raises the temperature of the fluid. A typical use would be to start up the system in cold climates. The oil is heated to reach its optimal viscosity before circulating to the bearing. e heater uses a built-in thermo- stat to shut off when the predetermined temperature is achieved. Installation Environment e operation of a circulating oil system can be affected by its surroundings. Temperature, altitude and exposure to the elements should be taken into consideration in the design. e space available for the unit affects the propor- tions of the tank, the mounted position of the components and the piping configuration. e bearing should be at an elevation higher than the circulating oil system so oil can return to the system by gravity (Figure 5). e return line must be vented and two sizes larger than the supply line to avoid backup. e pressure required to supply oil to the bearing can be affected by the elevation to the bearing, reductions in pipe size and any restrictions caused by manifolds or nozzles. Reservoirs and Piping A standard reservoir is welded steel. e cover is a heavy-gauge steel. It is used as a plat- form for mounting system components. e piping and fittings usually are made of iron with national pipe thread (NPT) fittings. e entire system requires painting or some type of protective coating to avoid corrosion. Reservoirs and piping can also be stainless steel. e connections may be welded, and some fittings are flanged. Circulating oil systems should be tested for leak detection and compo- nent operation before being put into service. Getting What You Ask For ere is not one size that fits all when it comes to circulating oil systems. Work closely with the bearing manufacturer to determine optimal operating conditions. Tell your lube skid builder what you need the system to do. Factor into the design the fail-safes, mainte- nance and durability that suit your application. e system will be as good as the forethought put into it. ML