Description
The gear set draws oil from the tank through the built-in filter and transfers it to the nozzle line via the cut-off solenoid valve. A pressure-regulating valve dumps all oil that is not required at the nozzle.
In two-pipe operation, the by-pass plug must be fitted in the return port, which ensures that the oil dumped by the regulating valve is returned to the tank and the suction line flow is equal to the gear set capacity.
In a one-pipe operation, oil that does not go through the nozzle line is returned directly to the gear inlet, and the suction line flow is equal to the nozzle flow. In that case, the by-pass plug must be removed from the return port, which is sealed with a steel plug and washer.
Bleed
Bleeding in two-pipe operation is automatic (except for AL 20) : it is assured by a bleed flat on the piston.
For AL 20 in two-pipe operation and for all models in one-pipe configuration, the plug of a pressure gauge port must be loosened until the air is evacuated from the system.
Cut-off
The AL pump’s solenoid valve is of the “normally closed” type and is situated in the nozzle line. This design ensures an extremely fast response, and the switching can be selected according to the burner operating sequence and is independent of motor speed.
When the solenoid is non-activated, the valve is closed, and all oil pressurized by the gear set passes through the regulator to the suction or return line, depending on the pipe arrangement.
As soon as the solenoid is activated, oil passes to the nozzle line at the pressure set by the pressure regulating valve.
