Return Flow Restriction

The return flow restriction may be installed in the delivery valve holder in addition to the delivery valve. It is positioned in such a way that it is between the delivery valve and the injection nozzle. With the return flow restriction it is possible to reduce wear in the high pressure system caused by the fast flow of fluids and rapid changes of pressure (cavitation). During fuel delivery the pressure of the fuel against the valve plate is so great that it overcomes the force of the spring and the fuel can flow without hindrance to the injection nozzle. At the end of the effective stroke the closing of the nozzle generates a pressure wave in the opposite direction to that in which the fuel is delivered. This can lead to cavitation. At the same time the pressure spring forces the valve plate back onto its seat and the fuel has to flow back through the throttle cross section, thus damping the pressure wave and making it harmless.