Reliability estimates for oxygen monitors

This paper presents results of a task to analyze operating experience data to determine ´fail to operate´ and ´spurious alarm´ failure rates for fixed oxygen monitors at the DIII-D fusion facility. These monitors are used near gas storage and cryogenic systems to protect personnel from anoxia if gaseous or cryogenic nitrogen or helium was inadvertently released into the room. Studying monitor reliability supports personnel safety assessment and can potentially improve monitor performance. The DIII-D Trouble Report database was used to determine the number of monitor faults, and operations data supplied the operating times and numbers of monitors. The oxygen monitor fail to operate value was found to be ∼1E-06/hour, and the spurious alarm value was ∼1E-05/hour. These reliability values compared favorably to values from non-fusion applications reported in the literature.