Abstract
Appendices to a report on the self tripping light curtain safety device for machine presses were presented, including a fault tree analysis, failure mode analysis, reliability formulae and probabilities, operation sequence of control relays, tables of raw production data, productivity data plots, a computer program for monitoring and recording physiological data, worker questionnaires, and physiological data plots. The analytical procedure and fault tree results of fault tree analysis were described, based on system components. Safety was differentiated into self tripping safety (probability that the press will not operate while the curtain is obstructed) and guard safety (probability that the press will stop operating when the curtain is broken). Failure mode analysis included description of basic failure modes of light curtain unit electronic components, failure modes for relays, and failure rate data for each functional block. Actual probability values for guard safety and self tripping safety were calculated by reliability formulae. Mean time between self tripping accidents was calculated to be 5 x 10(14) hours, and probability of guard malfunction in a single press cycle was calculated as 1.5 x 10(-18). Sequences of relay operations in various modes were described. Finally, actual production and physiological data from an evaluation of the light curtain were included, along with a computer program used in monitoring and recording of physiological data.
