Progressively finer strainers should be provided at various points in the oil

Progressively finer strainers should be provided at

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more than 3 holes per linear inch) is positioned on the entry pipe to the storage tanks. Progressively finer strainers should be provided at various points in the oil supply system to filter away finer contaminants such as external dust and dirt, sludge or free carbon. It is advis- able to provide these filters in duplicate to enable one filter to be cleaned while oil supply is maintained through the other. Fuel Oils
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1. Fuels and Combustion 5 Bureau of Energy Efficiency The Figure 1.1 gives an illus- tration of the duplex system of arrangement of strainers. The Table 1.3 gives sizing of strainers at various locations. Pumping Heavy fuel oils are best pumped using positive displacement pumps, as they are able to get fuel moving when it is cold. A circulation gear pump running on LDO should give between 7000- 10000 hours of service. Diaphragm pumps have a shorter service life, but are easier and less expensive to repair. A centrifugal pump is not recommended, because as the oil viscosity increases, the efficiency of the pump drops sharply and the horsepower required increases. Light fuels are best pumped with centrifugal or turbine pumps. When higher pressures are required, piston or diaphragm pumps should be used. Storage Temperature and Pumping Temperature The viscosity of furnace oil and LSHS increases with decrease in temperature, which makes it difficult to pump the oil. At low ambient temperatures (below 25°C), furnace oil is not easily pumpable. To circumvent this, preheating of oil is accomplished in two ways: (a) the entire tank may be preheated. In this form of bulk heating, steam coils are placed at the bottom of the tank, which is fully insulated; (b) the oil can be heated as it flows out with an outflow heater. To reduce steam requirements, it is advisable to insulate tanks where bulk heating is used. Bulk heating may be necessary if flow rates are high enough to make outflow heaters of adequate capacity impractical, or when a fuel such as Low Sulphur Heavy Stock (LSHS) is used. In the case of outflow heating, only the oil, which leaves the tank, is heated to the pump- ing temperature. The outflow heater is essentially a heat exchanger with steam or electricity as the heating medium. TABLE 1.3 SIZING OF STRAINERS Location Strainer Sizes Mesh Holes/Linear inch Between rail/tank lorry decanting point and main storage tank 10 3 Between service tank and pre-heater 40 6 Between pre-heater and burner 100 10 Figure. 1.1 Duplex Arrangement of Strainers in a Pipeline
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Temperature Control Thermostatic temperature control of the oil is necessary to prevent overheating, especially when oil flow is reduced or stopped. This is particularly important for electric heaters, since oil may get carbonized when there is no flow and the heater is on. Thermostats should be provided at a region where the oil flows freely into the suction pipe. The temperature at which oil can readily be pumped depends on the grade of oil being handled. Oil should never be stored at a temperature above that necessary for pumping as this leads to higher energy consumption.
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  • Spring '17
  • Jerome Ramos

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