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'A' trapped key

Overview

The GIS utilizes trapped key interlocking. Trapped key interlocks are also known as Castell or Kirk key among other names. Trapped key interlocks utilize a series of keys and locks for sequential control of equipment and machinery. The system is configured to ensure that a defined sequence of events takes place to reduce hazards before personnel are exposed to them.

Trapped key systems function by requiring that a key, or possibly several keys, be used to enter a hazardous area, or before beginning to use equipment that may cause interferences. The only way to obtain the key(s) is by first isolating the source(s) of hazardous energy. This primary key can only be removed after hazardous energy is isolated from the machine. The use of multiple keys ensures that multiple sources of hazardous energy are removed or that a specific sequence of events must happen.

If a safeguarded area requires full-body access, then a personnel safety key must be obtained prior to entering the safeguarded area. Personnel safety keys are released when the primary key (obtained when isolating hazardous energy) is used to unlock access to the safeguarded area. The personnel safety key must be kept in the control of the person entering the safeguarded area at all times.

Trapped keys allow access to hazardous zone. However, trapped keys do not provide adequate protection for purposes of lockout/tagout. Use of trapped key alone is only allowed under the minor serving exemption for tasks that are routine, repetitive, and integral to the use of equipment for production.

Trapped Key Components

Trapped Key

The Trapped key is a stainless-steel, weatherproof key which is designed specifically for use with the Prosafe Trapped Key Locks. When used with a trapped key lock, this product forms a robust mechanical type of interlocking unit which is ideal for environments where electrical interlocking systems may be unsuitable or expensive to install and maintain, such as areas with explosive atmospheres.

Rotary Trapped Key Interlock Switches

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Key Rotary Switch

Rotary Trapped Key Interlock Switches are used for electrical isolation of machinery to improve safe access. Once the power has been turned off, the key can be withdrawn and used in the next sequence of operation such as unlocking an access door or in an exchange unit.

Trapped Key Solenoid Release Unit

Trapped Key Solenoid Release Unit electrically isolates machinery to improve access safety. The unit consists of a rotary trapped key interlock switch (see above) and a solenoid. The trapped key can be removed once an external signal is given to its internal solenoid locking mechanism. An indicator light on the solenoid release unit shows when the trapped key can be removed—that is, when power is applied to the solenoid. The solenoid signal only needs to be present when key removal is necessary.

Trapped Key Interlock Exchange Unit

Exchange Units for Trapped Key Interlock Switches are used in an interlocking sequence to link together other devices. These units allow more complex operating sequences. Used to trap and release keys in a pre-determined sequence. Primary keys remain trapped until all secondary keys have been re-inserted, rotated, and trapped in the key exchange unit.

Trapped Key Bolt Interlock

Trapped Key Bolt Interlock Switches allow access to hazardous areas only when an appropriate key is inserted into the interlock. Bolt interlocks provide a method of helping prevent access through gates. With these bolt interlocks, there is no need to run power wires to the gate.

Access & Chains Trapped Key Interlock

Access/Chains Trapped Key Interlock Switches allow access to hazardous areas only when an appropriate key is inserted into the interlock. These access interlocks provide a method of helping prevent access through gates. They are actuated by a lever.

Trapped Key Maps

Graphical representations of trapped key sequences.

• Coudé

• Enclosure

• Telescope

Other Resources

Trapped Key Roadmap

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