Share thisAn increase in flooded cages revealed valves damaged by the handling processes.
A new 12,000 cage mouse barrier facility utilizing individually ventilated cage racks with an automatic watering system designed with quick disconnect water valves was opened in 2005. Use of an automatic watering system was expected to have a lower incidence of flooded cages as compared to the incidence of flooded cages using water bottles. However, over time the facility experienced a significant increase in the number of floods with the automatic watering system as compared to when the facility originally opened and to other facilities using water bottles.
A thorough investigation, which involved the automatic watering system vendor, was initiated. This investigation included analyzing all of the components of the valves, the automatic watering system, and the procedures for handling and processing the valves. The investigation discovered both internal damage to the valves and that the current handling processes would likely lead to further valve damage.
Prior to refurbishing the valves to address the internal damage, we wanted to ensure our handling processes would not lead to any further damage. Our goal was to identify a method to handle and store the valves which would protect them from physical damage during cage wash, autoclaving, and storage. Ideally, finding one piece of equipment to contain the valves through this entire process would best serve our needs. Modified test tube racks were found to be the best solution. The procedures for handling and processing the valves were then adapted for use of these modified test tube racks.
Internal Valve Analysis
As flooded cages were found and documented, the valves were associated with these cages were removed from circulation. Batches of these valves were sent to the automatic watering system vendor for analysis. The vendor analyzed all components of the leaking valves to determine if there was any damage to the valves that could lead to the flooded cages. The analysis revealed that the valves had suffered damage to an internal silicone diaphragm over time, which possibly resulted in valve malfunction, and therefore flooded cages.
Handling Process
At the time of review, handling the valves involved all dirty valves being placed in a plastic bucket located in the housing room. Once half to¾full, these buckets were then taken to the cage wash where they were poured into metal baskets for processing through the tunnel washer. Once cleaned, the valves were then bagged in clear autoclave bags about 50-75 per bag, and then autoclaved and stored for later use. The settings of the autoclave cycle being used were also analyzed by the vendor. It was found that the cycle used was drawing a deep vacuum greater then negative -20 inches of mercury. Autoclaving valves with a vacuum draw greater then negative -15 inches of mercury had been found to cause damage to the silicone components of the valves over an extended period of time. Thus, at the time of investigation, autoclave practices were potentially contributing further to valve damage due to deep negative vacuum cycles, weakening the silicone of our valves.
Force testing of the valves from our facility compared to new, unused valves was also conducted by the vendor. This testing found that the weight of the combined valves in a pile could result in further damage to the weakened internal silicone diaphragms and also to the valve stems.
The Immediate Changes
After identifying the causes for valve damage, we set forth to adjust these various factors to prevent further valve damage.
The decision was made to have all of our valves refurbished by the vendor. This included disassembling the valves, replacing all silicone components, reassembling the valves, and then testing all functional characteristics. The valves were then date stamped so they could be identified as refurbished valves.
The second adjustment made was to the autoclave cycle used for sterilizing the valves. We programmed a liquid cycle with no vacuum draw to be used for processing valves only.
The Ultimate Goal
Our main goal was to identify a method to handle and store the valves once they were refurbished to protect them from physical damage throughout the cage wash processing, autoclaving, and storage.