OL

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 is used to by-pass all oil which is not required at the nozzle.
One-pipe installation
The oil which 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, and the return port sealed by steel plug and washer.
Two-pipe operation
The by-pass plug is fitted in the return port, which ensures that the oil by-passed by the regulating valve is returned to the tank and the suction line flow is equal to the gear set capacity.

Cut-off
The solenoid valve of the OL pump is of the “normally closed” type and is situated in the nozzle line. This design ensures 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 suction or the return line, depending upon pipe arrangement.
– activated, oil passes to the nozzle line at the pressure set by the pressure regulating valve.

Bleed
In one-pipe operation, the bleeder valve must be loosened ( or a pressure port must be opened) until the air is evacuated from the system.
Bleeding in two-pipe operation is automatic : it is assured by a bleed flat on the piston.