AMBAC International nozzles are of the closed, differential, hydraulically-operated type. They utilize a spring-loaded valve seating adjacent to the spray orifice to close the orifice after each injection of fuel into the combustion chamber. The valve is operate hydraulically by the pressure of the fuel oil delivered by the injection pump.A wide variety of nozzles are manufactured to meet the requirements of the many combustion systems and engine sizes, but essentially there are two basic groups,pintle and hole type nozzles.