Abstract: Malfunctions of plunger (15) in the mixhead (10) of a system for mixing a plurality of fluids such as polyol and isocyanate for the manufacture of polyurethane foam, which plunger induces variations in fluid pressures as the mixhead operates, are monitored by a method that includes the steps of measuring the upstream pressure of at least one fluid and generating a signal responsive thereto, and comparing the pressure responsive signal to a preselected pressure responsive signal and generating an alarm if the pressure responsive signal comparison falls outside preselected limits.

Abstract: A nozzle attachment (10) for cleaning residual material from a mixhead pour nozzle (16) having a cylindrical body (17) terminating in an end face with an axial bore (20) receiving a plunger (23) including, a sleeve (30) positioned outwardly of the cylindrical body forming a plenum chamber (52), ports (40, 41) in the sleeve communicating the plenum chamber with a source of pressurized fluid (70), and a cap (60) positioned circumferentially of the end face of the pour nozzle and providing an annular substantially radially inwardly directed orifice (65) communicating with the plenum chamber for directing pressurized fluid inwardly across the end face of the pour nozzle to remove residual material therefrom. A pressurized air supply system (70) provides air at different pressures to the nozzle attachment at selected times during the operating cycle of the mixhead pour nozzle.