CleaverBrooks CBLE, Operation And Maintenance Manual

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Burner Operation and Control
2-16 750-91 (revised 2009)
Model CB-LE Packaged Boiler Manual
2.10 — Atomizing Air
Air for atomizing the fuel oil (referred to as “primary” air) is pumped by the air pump into the air-oil receiver tank
and delivered under pressure through a manifold block to the oil burner nozzle.
The atomizing air mixes with the fuel oil just prior to the oil leaving the nozzle.
Atomizing air pressure is indicated by the air pressure gauge on the burner gun.
Air pressure from the pump also forces sufficient oil from the tank to the pump bearings to lubricate them and also
to provide a seal and lubrication for the pump vanes. As a result, the air delivered to the tank contains some lube
oil, however, most of it is recovered through baffles and filters in the tank before the air passes to the burner.
Some of the primary air is also used to assist the oil pressure regulators of the fuel oil controller. Further explana-
tion is given in chapter 5.
2.11 — Oil Fuel Flow: Light Oil
Fuel oil is delivered into the system by a supply pump which delivers part of its discharge to the oil burner. Excess
oil is returned to the oil storage tank through the fuel oil relief valve and oil return line. Normally the pump oper-
ates only while the burner is in operation, although a positioning switch is often provided so that either continuous
or automatic pump operation can be obtained (See Figure 2-10).
The oil flows through a fuel oil strainer to prevent any foreign material from flowing through the control valves
and nozzle. The fuel oil controller contains in a single unit, a metering valve, a regulator, and a gauge required to
regulate the pressure and flow of oil to the burner. The adjustable regulator controls the pressure. To assist in the
regulation, back pressure is created by an orifice nozzle located in the oil return line immediately downstream of
the fuel oil controller.
The programming relay energizes or de-energizes the solenoid oil valves to permit or cut off oil flow to the burner.
Two valves, operating simultaneously, are used. The valves are closed when de-energized. They cannot be opened
(energized) unless the combustion air proving switch and the atomizing air proving switch are closed. The two
switches are satisfied, respectively, by sufficient combustion air pressure from the forced draft fan and pressurized
air from the air pump.
The oil flow to the burner is controlled by the movement of the metering stem in the oil metering valve, which var-
ies the flow to meet load demands. The metering valve and the air damper are controlled simultaneously at all times
by the modulating motor to proportion combustion air and fuel for changes in load demand.