There are multiple inherent safety issues involved with cryogenics. You have extreme cold, oxygen deficiency hazards (ODH), high-pressure inert gases, high-voltage motor control centers and a host of rotating equipment. One must be constantly aware of the changing conditions of the system as it cools down and warms up as the associated hazards can change with the state of the refrigeration cycle.
We can push crash buttons to shut down various components and close isolation valves associated with the section of the system we need to work on, but we still have to verify that it’s safe. For this we have many devices built into the system to help with diagnosing problems, monitoring operations, as well as checking the system’s condition to be able to perform maintenance safely. There are temperature readouts, pressure readouts, flow indicators, current draw readouts and voltage meters built into each system, as well as hand held tools and meters to also help with the verification process.
Some of our cryogenic systems are housed in different buildings, such as Meson Central Cryogenics Test Facility housing the compressor and refrigerators that supply liquid helium and liquid nitrogen to the experiments housed in the Meson Detector Building, about 200 meters away. There’s also the FAST facility, with the compressors in Lab B and the refrigerators and experiments about 500 meters away in the FAST building. All of these buildings have built-in safety systems to help assure our safety while we are working in them. In-house ODH monitors will sound an alarm if the oxygen levels falls below 19.5 percent and will trigger ventilation fans to start. Most buildings also have ventilation fans that run constantly and all are checked weekly. Any failure of the ventilation system will trigger an alarm.
Training, experience, intimate knowledge of the system, and written, approved procedures are all necessary to assure the safety of all personnel involved with maintenance and monitoring of our cryogenic systems. Remove any one of these components and the potential for an injury increases. Multiple personnel are used in all our procedures and will include a trained, experienced lead person, an in-training assistant and in some cases an assistant observer. The written procedures are a dynamic document. As we perform the procedure and newer people get involved, we learn different, more effective and even safer ways to conduct our cryogenic activities. Procedures are updated to reflect these lessons learned.