burners atomize the oil by fuel-oil pressure. The
fuel-oil system of a pressure-atomizing burner consists
of a strainer, pump, pressure-regulating valve, shutoff
valve, and atomizing nozzle (fig. 4-39). The nozzle and
electrode assembly includes the oil pipe, nozzle
holder, nozzle, strainer, electrode insulators,
electrodes, supporting clamp for all parts, and static
disk. The oil pipe is a steel rod with a fine hole drilled
through it. This hole reduces oil storage in the nozzle to
a minimum that prevents squirting at the nozzle when
the burner shuts off.
The air system consists of a power-driven blower
with means to throttle the air inlet, an air tube that
surrounds the nozzle and electrode assembly, and
vanes or other means to provide turbulence for proper
mixing of the air and oil. The blower and oil pump are
generally connected by a flexible coupling to the
burner motor. Atomizing nozzles can be furnished to
suit both the angle of spray and the oil rate of a
particular installation. Flame shape can also be varied
by changing the design of the air exit at the end of the
air tubes. Oil pressures are usually about 100 psi, but
pressures considerably greater are sometimes used.
Electric ignition is almost exclusively used.
Electrodes are located near the nozzle but must not be
in the path of the fuel oil spray. The step-up
tran sform er provides the high voltage (usually 10,000
the electrode tips.
volts) necessary to make an intense spark jump across
Figure 4-37.Cutaway view of a typical oil-fired furnace.
Figure 4-38.Oil-fired floor furnace.