With an automatic system, the truck engine is left idling until the driver opens the nozzle to begin delivery. The initial flow operates the flow switch that triggers the throttle actuator and increases the truck engine’s speed to a pre-set pumping rate for the balance of the delivery. When the driver closes the nozzle, the flow switch senses the cessation of the flow and releases the throttle actuator, thus returning the engine to idle speed. Action is nearly instantaneous.

The flow switch looks somewhat like an angle check valve. A discharge line check delivery valve is generally required on fuel trucks by weights-and-measures ordinances to prevent product from flowing back through the delivery meter when the hose is rewound. The flow switch contains a built-in hose pressure bleed valve. This valve permits high pumping pressure, trapped in the hose at the nozzle shutoff, to bleed back slowly through the check valve until the hose pressure drops to 25 psi and the relief valve closes to hold this pressure in the hose during rewind. This relief valve may be blocked out at installation if not permitted by local regulations.

By using the flow switch /angle check valve for automatic flow control, the pumping rate is controlled from the nozzle. This reduces wear and tear on the hose, pump and engine.

The flows switch and check valve are combined into one unit. The unit is available with air or an electric switch and furnished with NPT or BSP threading as well as a hose pressure bleed valve.

The flow switch/angle check valve controls the truck engine speed. The valve is used with centrifugal and positive displacement pumps. Auxiliary bypass dlla138s1191 valves with positive displacement pumps reduce the pressure at idle speed, which increases the flexibility of the hose. The hose is locked during pumping and while driving to prevent hose reel movement. The flow switch/angle check valve has interlocking air emergency brakes. A great deal that can be said for tried and true technology that works well and can be depended on.