Fuel Oil Pumps and Suction Capacities

Single stage or double stage fuel oil pumps and their suction capacities

The limitation of a fuel oil pump feeding a burner may often be the suction side. With high suction lifts, vacuum in the suction line will evaporate the light fractions of the fuel oil and the pump will start to choke. In addition to be aware of the pressure side, it is always important to keep a close look at the suction side of the pump.

In general two types of fuel pumps feeding the burners are used

• single stage pumps
• double stage pumps

A single pump consist of only one set of pumping gears and the lift capacity is limited compared to a two stage fuel pump consisting of a double set of pumping gears.

• a single-stage pump is suited for low-level lifts up to 5-10 inches of vacuum
• a two-stage pump is suited for medium-level lifts up to 10-15 inches of vacuum

Higher vacuum levels requires use of a separate lift pump and a feeding reservoir to the fuel pump.  

The total vacuum in a fuel oil suction line can roughly be estimated:

• 1 inch of vacuum for each foot of lift
• 1 inch of vacuum for each 90^o elbow
• 1 inch for each 10 feet of 3/8 inch horizontal suction pipe
• 1 inch for each 20 feet of 3/8 inch horizontal suction pipe

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