Page 6 - Webster Service Manual

1
FUEL UNITS
GENERAL INFORMATION
OIL HEATING TERMINOLOGY
As with most major industries, oil heating has devel-
oped a language of its own which contains a number of
terms not encountered elsewhere The following list
includes the terms which are most common to the oil
heating industry.
Single-stage fuel unit
:
unit with one set of gears for both
suction and pressure.
Two-stage fuel unit
:
unit with two sets of gears, one for
suction and one for pressure.
One-pipe system
:
one line, an inlet line, from tank to
fuel unit.
Two-pipe system
:
two lines, one inlet and one return
line, from tank to fuel unit.
Bypass plug
:
small hex socket head pipe plug used to
close internal port and convert unit from one pipe to two
pipe operation.
Bleed
:
to remove air from system.
Lift
:
oil drawn from a level below pump expressed in feet
of lift or inches of mercury.
Head of oil
:
column of oil over fuel unit expressed in psi
or feet.
Inlet port
:
port which receives oil from tank.
Bypass port
:
port which discharges surplus oil back to
tank in two-pipe system.
Return line port
:
same as by-pass port.
Valve differential
:
number of pounds per square inch the
pump pressure must drop from operating pressure to
close nozzle valve.
Delivery
:
gallons per hour pumped from the nozzle out-
let assembly of the fuel unit.
Gear Set Capacity:
Total amount of oil being displaced
by the pumps gear set(s).
HOW A
FUEL UNIT WORKS
The fuel unit performs three basic functions:
1.
Supply the Oil
.
The pumping action,of the fuel unit is
accomplished by the gearset. In a single-stage fuel unit
there is only one set of gears. Their function is to draw
oil from the tank and deliver the oil to the nozzle under
sufficient pressure to ensure the oil is properly atomized
for combustion. A single-stage fuel unit is generally