PUMP AL

The gear set draws oil from the tank through the built-in fi lter and transfers it to the
nozzle line via the cut-off solenoid valve. A pressure regulating valve is used to
dump all oil which is not required at the nozzle.
In two-pipe operation, the by-pass plug must be fi tted in the return port, which
ensures that the oil dumped by the regulating valve is returned to the tank and the
suction line fl ow is equal to the gear set capacity.
In one-pipe operation, the oil which does not go through the nozzle line is returned
directly to the gear inlet and the suction line fl ow is equal to the nozzle fl ow. In that
case, the by-pass plug must be removed from the return port, and the return port
sealed by steel plug and washer.

Bleed
Bleeding in two-pipe operation is automatic (except for AL 20) : it is assured by a
bleed fl at on the piston.
For AL 20 in two pipe operation, and for all models in one-pipe confi guration the plug
of a pressure gauge port must be loosened until the air is evacuated from the system.

Cut-off
The solenoid valve of the AL 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 the suction or return line, depending
upon pipe arrangement.
As soon as the solenoid is activated, oil passes to the nozzle line at the pressure
set by the pressure regulating valve.