Unloader valves should be used to protect the pump. The full flow from the pump must pass through the unloader valve for satisfactory operation. Should the actual operating pressure exceed that of the adjusted pressure the unloader valve will act as a pressure regulator, bypassing excess fluid to ensure the adjusted pressure is not exceeded. The valve will switch to pressure free bypass when the spray gun is shut off and the line pressure between gun and valve remains dormant.

The valve can be used to control several spray guns simultaneously. Several pumps can also be connected to a common discharge line. For specialist applications our unloader valves are available in alternative materials, eg bronze, stainless steel.

Unloaders designated PL are particularly suited to centralised and multi pump ring main systems. These unloaders are supplied with a plate and seat instead of the normal kick back valve cone. This reduction in mass tends to change the resonant frequency of the pipework, and has increased the service life of certain difficult installations.