ABSTRACT
Trip-nip bars are used to prevent fingers/hands being drawn into in-running nips on machines such as printing presses. However, if trip-nip bars are improperly designed, installed or maintained, they can represent a significant entrapment hazard if the fingers/hand are drawn against them and excessive force is required before the safety mechanism trips, or even after tripping has occurred. Field tests of an entrapment hazard using the test fingers were successful and the test method is designed to be repeatable by industry during maintenance checks. It was also decided that because of the potential significance of entrapment profile and area, information on pressure-pain tolerance limit (PPTL) needed to be gathered with forces applied by a similar entrapment profile to the hazard itself. Test fingers with pressure sensitive film on the surface were inserted into entrapment hazard and compared the film results with the calibrated sheets to identify whether entrapment pressures were higher than average PPTL figures.
