Early detection of cryostorage tank failure using a weight-based monitoring system.

Abstract

To study the relationship between liquid nitrogen loss and temperature in cryostorage dewars and develop an early-warning alarm for impending tank failure. Cryostorage dewars were placed on custom-engineered scales, and weight and temperature data were continuously monitored in the setting of slow, medium, and fast rate-loss of LN2 to simulate three scenarios of tank failure. LN2 Tank weights and temperatures were continuously monitored and recorded, with a calculated alarm trigger set at 10% weight loss and temperature of - 185°C. With an intact tank, a 10% loss in LN2 occurred in 4.2-4.9days. Warming to - 185°C occurred in 37.8-43.7days, over 30days after the weight-based alarm was triggered. Full evaporation of LN2 required ~ 36.8days. For the medium rate-loss simulation, a 10% loss in LN2 occurred in 0.8h. Warming to - 185°C occurred in 3.7-4.8h, approximately 3h after the weight-based alarm was triggered. For the fast rate-loss simulation, a 10% weight loss occurred within 15s, and tanks were depleted in under 3min. Tank temperatures began to rise immediately and at a relatively constant rate of 43.9°C/h and 51.6°C/h. Temperature alarms would have sounded within 0.37 and 0.06h after the breech. This study demonstrates that a weight-based alarm system can detect tank failures prior to a temperature-based system. Weight-based monitoring could serve as a redundant safety mechanism for added protection of cryopreserved reproductive tissues.