The unloader valve functions as a safety device. Unloader valves control the direction of the flow of water exiting the pump. A positive displacement pump always delivers water, regardless of whether the spray gun is open or closed. When the spray gun is closed, the unloader valve redirects the flow of water back to the inlet side of the pump. This prevents the build up of dangerously high pressure and guards against the failure of component parts. Pressure cleaners are installed with either a Trapped Pressure Unloader or a Flow Actuated Unloader.
Spray guns start, stop, and direct the flow of water from the pressure washer’s nozzle. Squeezing the trigger releases pressure. Releasing the trigger interrupts the flow of water to the nozzle, although the pump continues to run. Without an outlet for releasing this water, pressure would continue to build. A very dangerous situation would result.
Flow Actuated: Unloader valves respond to the interruption of water flow to the nozzle. These valves sense any decrease in flow from the valve to the spray gun and initiate the bypass loop in response. Unlike Trapped Pressure valves, no pressure is trapped, so no “kick back” occurs when water is re-released. With Flow Actuated unloader valves, operators cannot regulate pressure by downsizing the orifice size of nozzles. Flow Actuated valves detect the loss in flow, and react by cycling repeatedly.
If a company is member of the SIR (Dutch Waterjetting Association) it’s in Benelux “out of the question” to work with Trapped Pressure Unloader because to work safe the hose have to be direct pressure less by leaving the gun trigger
Max. working pressure : 150 bar ( 2.100 psi)
Max. Flow : 200 ltr./min. (45 gpm)
Max. temp. : 60°C
Inlet / by-pass connection : 1” Female (BSP ore NPT)
Outlet connection : 1” Female (BSP ore NPT)
Part Number NPT thread : 200530
Part Number BSP thread : 200532