Use gate valves to isolate oil accessories. In the case of an oil tank positioned higher than the burner unit, and should a fire develop, oil could run out and intensify the fire. A fusible valve helps to minimize this risk. However, check valves are often used to compensate for deficiencies in oil line piping. Disadvantages Check valves increase the amount of vacuum the fuel unit must overcome to supply oil to the system and reduce the distance supply lines can be run.
Thermal expansion can cause serious problems.
NOTE Select a check valve of the soft seated type suitable for No. 2 oil, which will seat tightly with a low head. If a check valve must be used and the top of the oil tank is below the burner level, use a lift type check valve with neoprene seat. There is always a slight amount of air in suspension in oil, and if air traps are present, they will gradually fill with air, and the pump will lose its prime. Removal of air is generally very difficult. NOTE Always provide a priming Tee and plug in the Suction Line at the highest possible point to aid in priming and in expelling air.