The incident

Electric heaters are commonly used with liquid helium dewar systems to aid cryogenic transfer. Cryogenic fluid vendors supply these heaters.

During the operation of a dewar heater, a worker experienced a mildly uncomfortable sensation from coming into contact with electrical current leakage. Despite the discovery, the worker continued to operate the heating system. Luckily, there were no injuries as the leakage was in the pico-amperage range. There was a delay in realizing and reporting the incident because the worker felt only a mild sensation, which could have resulted from other hazards in the complex work environment of the Lab.

The key findings from the incident include:

  • Time Pressures and Resource Limitations: Helium’s strategic nature and limited availability presented a safety and scheduling risk to our team. Its availability for experiments is not guaranteed, and the Lab is capped at a specific monthly volume. For instance, the Lab’s monthly limit is 1,500 liters of liquid helium, and the tests require an average volume of 750 liters.
  • Communication Challenges: Notifying off-normal events may take many forms within work teams. In this event, a worker reported an electrical equipment malfunction to a supervisor; however, the significance of this incident was only apparent after the worker completed the job.
  • Selection of PPE: Our magnet assembly and testing test team is highly adaptable. They quickly adjusted to changing conditions, finding an off-label usage for cryogen personal protective equipment (PPE) to insulate themselves from the stray current. In hindsight, we would have asked the team to pause work and confirm that safety controls were still appropriate. (Consult the Electrical Safety Manual 6.9.3 for a description of paused work).

Lessons learned from the incident:

  • Equipment Damage: The incident showed the potential for damage to equipment during transportation, stressing the importance of inspecting equipment upon receipt.
  • Dependency on Liquid Helium: The success of operations conducted at the facility relies on the availability of liquid helium, making it imperative to plan for and manage this dependency effectively while safely managing the operations and minimizing work disruptions.
  • Avoiding Tunnel Vision: Intense focus on tasks can lead to tunnel vision. Incorporating breaks or pauses into a work plan may help workers identify and navigate changes to expectations within their workspace.
  • The Importance of Communication: Effective communication is vital for the success of our operations. Recognizing and improving communication skills within a team is an ongoing process. Pre-job discussions are opportunities to frame in advance what an abnormal condition may look like. Three-part communication is another strategy when communicating abnormal conditions to help ensure effective communication.
  • Complexity of Unwanted Events: Unwanted events often arise from unforeseen interactions within complex operations. Pre-job discussions and thorough post-event analyses are essential for effectively identifying potential risks and planning accordingly.



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