In a trapped key interlocking system, keys are only released when it is safe to do so. A key exchange box is where one key is traded for another: the key released by an isolation interlock is inserted and trapped, and only then are the access keys released. Nobody can restore power until every access key has been returned.
Why use a key exchange box?
Simple applications need one isolation and one access point. Complex machinery, switchgear and process plants rarely do. A key exchange box lets you:
- release several access keys from a single isolation, for multiple doors, gates or guards;
- require several isolations to be completed before any access key is released;
- give each person entering the area their own personnel key, so the system cannot be re-energised while anyone is still inside;
- enforce a defined order of operation across several stages of a process.
How the sequence works
- The isolating switch or breaker is turned off, and its interlock releases the primary key.
- The primary key is inserted into the exchange box and turned. It is now trapped.
- The access or personnel keys are released and used to open the protected area.
- To restore power, the sequence is reversed: every access key must be returned before the primary key is released.
Where they are used
Wherever several hazards or access points depend on the same isolation: switchgear rooms and substations, robotic cells and production lines, conveyors, and process plant where a set order of shutdown and access must be followed every time.
Castell, Kirk and STI
- Castell: the X, Y, Z and B key exchange boxes, and the W key selector box.
- Kirk: the Type T interlock and the Type Transfer Panel interlock.
- STI (Serv Trayvou): TMEC, Exchange ST, Exchange SL and NX Exchange.
The right box depends on the number of keys in your sequence, how they are coded and where the unit will be installed. Our engineers can help you select and configure it: talk to an expert about your application.
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