IDEM Safety Switches SKORPION – Trapped Key Interlocking with Key Exchange

Designed and manufactured in the United Kingdom, Skorpion, IDEM’s Trapped Key System has been developed to provide extremely robust mechanical coded key safeguarding and interlocking for hazardous machinery.

The system works on the principle of releasing coded mechanical keys in a pre-determined sequence to ensure machine power is isolated before any access can be gained to hazardous or dangerous machinery.

After the machine control has been isolated (first key turned in the system) the key from the isolator can then be used to release other trapped keys to enable access to the guarded areas. After release of the first key (power isolation) safeguarding can be achieved without the need for electrical wiring, this makes the system ideal for use in harsh environments.

Operating Principle

A trapped-key guarding system relies upon the transfer of keys between a power isolation switch (or control switch) and a locking mechanism fixed on a guard.

The essential feature of the system is that a removable key is trapped either in the guard lock, or in the power isolation switch.

The interlock on the guard is arranged so that the key can be released only when the guard has been closed and locked.

This allows transfer of the key from the guard to the power isolation switch.

Closing the switch traps the key, so that it cannot be removed while the isolator switch is in the ON position.

If there is more than one source of power, and therefore more than one circuit breaking element to be actuated, then a key-exchange box is necessary, to which all keys have to be transferred and locked in before the access key, which is of a different coding, can be released for transfer to the guard lock.

Where there is more than one access guard, the key exchange box will accommodate an equivalent number of access keys.

Where a number of operations have to be carried out in a pre-determined sequence, then the transferable key is locked in and exchanged for a different one at each stage.


* No reduction of integrity due to the distance between movable guard and control system.

* High mechanical integrity, robust fixings and holdings suitable for all types of guards.

* Eliminates the need for electrical wiring to each movable guard.

* Available in Stainless Steel 316 – making it suitable when the movable guard is placed in harsh or hostile environments.

* Suitable for CIP and SIP cleaning processes and can be high pressure hosed with detergents at high temperatures.

* Can be used where the movable guard requires to be removed completely.

* All keys are coded in the factory and it is virtually impossible to override the system.

* A trapped key system provides a quick yet safe and reliable access to machinery.

* Use of a trapped key system can also prevent shortcuts and enforce a logical set of procedures that need to be satisfied.

* Until the isolator key is returned to its original position within the lock, there is no way to enable the machinery to be re-started.

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