METHOD FOR CHECKING THE FUNCTIONALITY OF EXTRUSION NOZZLES WITH REFRIGERATED SECTIONS OF PLASTIC EXTRUDERS FOR THE PRODUCTION OF FLAT OR TUBE FILMS

摘要

To check the functional capability of the cooling sections, provided with cooling-air supply lines and cooling-air removal lines, of a slot die (10) of an extruder for manufacturing flat films from thermoplastic material, the cooling-air supply lines (9) are connected as and when required to a central pressurised cooling-air feedline (4) by means of solenoid valves (2), controlled by an electronic arithmetic unit (1). In order to provide simple and reliable checking, a test program is used as a basis for closing by means of a shut-off valve (5) the cooling-air feedline (11) upstream of the branch lines leading to the individual solenoid valves (2), with the solenoid valves (2) closed. Then, by means of a pressure sensor (6) downstream of the shut-off valve in the cooling-air feedline, the pressure and the pressure drop which occur in the cooling-air feedline (4) upon opening of the solenoid valve (2) of the first cooling section to be tested are measured. In this method, an error signal is generated if the pressure and the measured pressure drop do not correspond to the typical values for the proper functions of the cooling-air feedline and of the cooling section tested. All the cooling sections are successively tested in a corresponding way.