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 higher suction lifts vacuum in the suction line evaporates light fractions of the fuel oil and the pump starts to choke.
In general there are two types of fuel feeding pumps used
- single stage pumps
- double stage pumps
A single stage 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 lifting pumps and a dedicated feeding reservoir to the fuel pump.
The total vacuum in a fuel oil suction line can roughly be estimated as
- 1 inch of vacuum for each foot of lift
- 1 inch of vacuum for each 90o 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