FAQ

working principle of self-sealing nozzle on the fuel dispenser

When refueling, the main valve is opened, the pressured oil will enter into the cavity between main and auxiliary valves inside the nozzle body and push through the auxiliary valve overcomes the force of spring, , then it will be discharged out of the nozzle. The auxiliary valve is used to prevent the liquid oil from flowing out of the cavity between main and auxiliary valves inside the nozzle when main valve is closed. If the main valve is not yet closed when fueling is over in process of preset refueling, the auxiliary valve may prevent oil in the nozzle and the static-conductive delivery hose from flowing out.

When oil passed through the auxiliary valve, the pressure inside the upper chamber in switching-membrane will be reduced . However, since the upper chamber in switching-membrane is open to the environment through an inclined hole in reducing sleeve, intake pipe, and the intake mouth of nozzle, external air may be supplied to the upper chamber in switching-membrane. So the pressure inside the upper chamber in switching-membrane may be kept equal to that inside the lower chamber (equal to atmospheric pressure), and the switching-membrane is maintained in its equilibrium position.

When the oil intake inside, negative pressure is established inside the upper chamber since it isolating from the ambient atmosphere. However, atmospheric pressure is still maintained inside the lower chamber; thus, a pressure difference ΔP appears between the upper and lower chambers. When ΔP is reach a certain value, the switching membrane haunches up and move the fitted self-sealing stem upward.

The steel ball is pushed and drops into self-control stem hole. Under the action of pulling force of switching handgrip, the self-control stem moves downward. The ejector pin of main valve moves downward since the pivot-point of switching handgrip move down. The main valve is closed, then with the stop of oil supply (in other words, the nozzle is self-sealed).