Condition monitoring of seal defects in pneumatic cylinders

The target in this study is determining the possible seal defects before they occur in pneumatic cyliders which are widely used in plastics, food, textile, chemical and mechanical industries. By this advantage in hand, the operator can eliminate the sudden system shut downs and as a result also eliminates the loss of man power, time and costs. For this purpose an extra program is downloaded to the programmable logic controllers (PLC) which are controlling almost the whole system in many automatic controlling applications including pneumatic cylinders and the possible defects can be promptly realized by PLC. In this thesis, the possible defects are determined by vibtation analysis and velocity calculation. Two proximity switches are mounted to the lowest and highest limits of the cylinder. Time of the stroke movement is measured and the velocity is calculated by the measured data. Also a 5 cm long beam is installed to the cylinder body with a piezo-electric transducer bonded on it. By this transducer the vibration data are routed to the PLC as a low voltage signal. As a result of this study, it is observed that the extent of the seal defect in pneumatic cylinders is proportional to the stroke time, vibration amplitude and vibratrion energy .