What is Trapped Key Interlocking?
Often referred to as Castell or Castle Key Locks; Trapped Key interlocking is the sequential control of dangerous machinery and hazardous processes for industrial safety applications. mGard is the only modular range of mechanical Trapped Key interlocks that have been independently certified to PLe; the highest safety rating on the market.
It is called 'Trapped Key' as it works by releasing and trapping keys in a predetermined sequence that cannot be intentionally defeated or circumvented by unauthorised means. Therefore, Trapped Key interlocks have been designed to minimise the motivation for defeating the interlocking device in accordance ISO 14119: Safety of Machinery - Interlocking devices associated with guards.
The principles of Trapped Key interlocking apply to all industries where it is essential to isolate all energy sources before safe access into machinery or protected areas can be achieved. As an example, after a machine's control circuit has been isolated by means of a 'Key Switch,' a key is released that can be used to grant access to the guard doors around the perimeter of a dangerous machine.