ASSESSMENT OF AIRSHAFT FAILURES IN PAPER REELS

Airshafts are commonly used in manufacturing processes for fitting to a reel that is used for winding rolls of material such as paper, card and plastic film. An airshaft is designed so that, on fitting into a r eel, it can be readily expanded, thereby achieving a firm attachment: it may also be easily contracted prior to dismantling to facilitate re moval. Their efficient design makes them ideal for quick and firm atta chment onto a reel and then mounting onto bearing housings to enable t he winding or unwinding of rolls of stock material with the minimum of equipment down time. The inherent shape and functionality of an airsh aft means that failure by fatigue and fracture is a major concern. The airshaft, for example, has a cross-section which changes along its le ngth and it is subjected to significant bending stresses, which altern ate with rotation. The weight of the roll of material will also change appreciably during operation and, in addition, the inflated inner tub e pressure further increases stress levels at critical locations. This paper analyses the service failure of a specific airshaft, from both fatigue crack initiation and crack propagation considerations, and dis cusses how the failure might have easily been avoided. Copyright (C) 1 996 Elsevier Science Ltd.