Lockout-tagout is a standard safety procedure used in industry to ensure that dangerous machines are properly shut off and not started again during maintenance or troubleshooting procedures. It requires that hazardous power sources be isolated and rendered inoperative before any repair procedure is started. Two key issues exist with lockout-tagout, that can be solved through the development and implementation of a Heads-up Assisted Lockout-Tagout (HALT) system.

1) While some lockout-tagout procedures are straightforward, others can be complex and may involve multiple members of a crew, across shift changes, or long-term shutdowns. Such procedures are normally documented on-site, but may be located in distant or inconvenient locations. The HALT system will provide a means for viewing complex procedures on an HMD in the field where they are needed.

2) One weakness of the lockout-tagout system is that it relies on people to follow proper procedure. In practice, locks can be circumvented by removing the lock with bolt-cutters, which may happen if personnel on different crews or shifts wish to use equipment and don’t believe lockout is necessary. In these cases, a machine may become energized and pose a dangerous hazard for maintenance personnel who are unaware that the lockout has been removed. The HALT system, combined with a separately developed monitored locking device, provides a means to actively poll the integrity of a lockout, and inform maintenance workers in real-time if the lockout status changes.

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