Whilst undertaking a maintenance task on a piece of plant, it was observed that the isolator switch worked correctly and the LOTOTO process was a success. The lock was applied and the machine was tried out successfully. When attempting to remove the lock after the task, it was noticed that, with the lock still in place, the isolator switch could still turn back to the ON position with slight resistance.

An investigation showed that the isolator switch locking mechanism (in blue circle below) was damaged internally, but external visual checks showed that it was in full working order.

• Include an isolator function check on the pre-start check sheets.

• When locking out check the isolator does not turn back.

Please review the recently published  MPA and British Precast guidelines on LOTOTO.

MPA LOTOTO Guidelines

British Precast LOTOTO Guidelines