Isolator could be turned on with castell system engaged

The potential for an operator to be injured existed when the mechanical locking system failed on the isolator switch for the mixer castell system. Although the operator had turned and removed the castell keys which should have locked the isolator in the 'Off' position. He discovered when implementing the ‘Try Out’ part of the LOTOTO system, the isolator could be turned back to the ‘On’ position.

An examination revealed that the block the castell key bolt should have engaged with had worked loose and turned 90 degrees. This meant that the bolt was not engaged in the recess of the block, this enabled the isolator to be moved with the keys out. The isolator switch locates on end of shaft. Block should turn with shaft if grub screw is done up correctly. See image

• All similar systems should be checked by competent person to ensure blocks are in correct position, grub screws are tight and blocks cannot move on the shaft.
• Isolators should be locked off with padlocks even if connected to an interlocking system
• Always check the isolator cannot be turned on as part of the ‘Try Out’ section of the LOTOTO system

Please see images below of block with castell bolt located correctly in the top and isolator switch in off position with padlock attached.