The SUNTEC AN oil pump is the basic model incorporating a pressure regulating valve with cut-off.
The gear set draws oil from the tank through the built-in filter and transfers it to the valve that regulates the oil pressure to the nozzle line.
All oil which does not go through the nozzle line will be by-passed through the valve back to the return line, in a two pipe installation or, if it is a one-pipe installation, back to the suction port in the gear-set; in that case, the by-pass plug must be removed from the return port, and the return port sealed by steel plug and washer.
The valve also has a cut-off function as follows:
During starting period when the gear-set speed is increasing, all the oil passes through a special flat on the piston, back to the return. Once the speed reaches a certain value and the flow can no longer pass through this flat, then the pressure increases rapidly overcoming the valve spring force and opens the valve.
During the stop sequence, the gear-set speed slows down and the valve closes when the gear-set capacity is lower than the flat flow.
The cut-on and cut-off speeds depend on the gear-set size, and set pressure.
Bleeding in two pipe operation is automatic, but it could be accelerated by loosening the plug in a pressure gauge port.
In one pipe operation, a pressure port must be opened to bleed the system.