During an inspection by the HSE at a block plant, a spare interlock bar was found under the block operator’s seat. The spare bar could have allowed the release of the key with the gate still in the open position, this could then be used to restart the plant. This would have bypassed the interlock system that was there to protect workers. 

Operators should understand that by-passing the interlock system (or similar systems that prevent machines operating without guarding being in place) is a very serious breach of the safe system of work and could result in a serious injury or fatality.

Where a machine has a spare captive key, a process should be in place that requires a line manager to authorise the use of the key. The key must be signed in and out by the authorised person. Failure to comply with this mandatory safe system of work should result in disciplinary procedures.