Figure 4-8: Booster pump 4-8 Fuel Units and Oil Valves Figure 4-9: Fuel de-aerator Chapter 4 Fuel Units and Oil Valves Most fuel pump manufacturers say that the maximum vacuum for a one pipe system is 6"; therefore to convert from two pipe to one pipe, your calculated vacuum must be less than 6". If you need over 6", consider installing a de-aerator in the oil line, especially if the line comes out of the top of the tank, so the pump will not get air bound. Fuel de-aerators Fuel de-aerators shown in Figure 4-9 have been developed to eliminate air problems caused by excessive vacuum. Here is how the system works: 1. Oil is drawn from the tank to the deaerators through a single pipe. A dual-pipe system, operating between the unit and the oil pump allows the device to remove the air. Only the amount of oil that is burned is replaced from the oil tank. The single pipe system eliminates the need to circulate unnecessary oil and its impurities throughout the system. 2. The surplus oil is pumped back to the deaerator, instead of back to the tank. 3. De-aeration increases the pump’s suction capacity while reducing its sensitivity to minor leaks in the suction line. 4. As surplus oil cycles through the de-aerator loop, it absorbs heat from the ambient air and the pump gears’ friction, reducing cold oil problems. burners, the use of a booster pump is required, Figure 4-8. The installation and associated piping of a system using a booster fuel pump is fully described later in this section. Avoid two pipe systems Two pipe oil systems should be avoided if possible. With a two-pipe system you are filtering way too much oil. The average oil pump, pumps over 15 gallons of oil an hour. The average burner fires at 1 gallon per hour. This means you are filtering over 15 gallons of oil for every one burned. You are using up the filter 15 times faster than needed. You are cleaning the oil tank through the filter. This is very expensive and inconvenient. The second problem is that the average return line is under about two pounds of pressure. A lot of oil can leak out of a small pinhole under two pounds pressure in the hundreds of hours a year a burner runs. The burner will not be affected by a return line leak. The only way you know you have a leak is when the customer runs out of oil or the oil shows up in the sump pump pit. This is way too late! If these were not reasons enough, it appears that two pipe systems are sludge machines. Copper is a catalyst that can affect hydrocarbons. Prolonged exposure to copper causes little hydrocarbon molecules to clump together into big, long hydrocarbon strings. They can plug up nozzles, strainers, and filters. Since we pump over 15 gallons an hour and burn only one, think of how many times each little hydrocarbon molecule has to travel back and forth to the burner through all that copper pipe before it is finally burned. On each trip the fuel gets a bit less stable and a few more hydrocarbon strings show up in the tank.
NORA Oilheat Technicians Manual
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