Trapped Key Interlocks

Machinery Directive 2006/42/EC

We are proud to announce that our Trapped Key Interlocks conform to the directive.

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Trapped key interlocking is a very effective means of controlling access to hazardous machinery. The technology forces operating and maintenance personnel to follow a predetermined sequence of events that will ensure the machinery is isolated before access is permitted.

The ISS Safety range of trapped key interlocks are robust, easy to operate and can be easily fitted to a wide range of applications. The all stainless steel range are robust, durable, easy to install, invulnerable to dirt, sand, snow, ice, moisture and proven in all types of hostile environments. Our range includes bolt and access interlocks, power control and isolation switches, key exchange boxes, timers and motion control sensors.

(HST-K) System Key

Manufactured of stainless steel the keys are coded so that they only fit the lock for which they are intended thus ensuring a high degree of safety. The user selects an engraving for the key that is of relevance to them. This appears on the key, the respective lock and its dust-cap.

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(HST-LS) Switchgear Interlocks

The common usage for the HST-LS interlock is to either lock 'ON' or 'OFF' electrical switchgear/control units. The standard unit is fitted with a 9.5mm square x 48.5mm long shaft that can utilise actuating levers or specific switchgear adaptors to operate motor or rotary handled isolators. Turning the key moves the shaft through 90 degrees isolating the supply and releasing the key. Manufactured of stainless steel and supplied with protective flip caps as standard.

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(HST-B) Single & Dual Key Bolt Interlocks

The HST-B range can be used to lock 'ON' or 'OFF' electrical switchgear circuit breakers, disconnectors and earthing devices by extended the bolt into a corresponding slot in a cam connected to the switchgear operating handle or toggle. Only when the switchgear is in the desired position can you release the key. Variations include single or double key units, orientation of the housing (left or right), bolt length/diameter, with either front or rear fixings and fitting a position limit switch to provide status information. Manufactured of stainless steel and supplied with protective flip caps as standard.

Please see the application gallery for more examples of this product.


(HST-S) Control Switches

The HST-S range of switches are used for isolating machinery, after the voltage has been removed via a switch which is directly controlled by the key movement the previously trapped key can be withdrawn and used to continue on in an interlocking sequence. Whilst the key is released the machine is 'OFF' and in a safe condition. The HST-S units are available with multiple lock portions, varying switches for isolation, in either a cast aluminium housing or panel mounted version. The lock portions are manufactured of stainless steel and supplied with protective flip caps as standard.

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(HST-M) Solenoid Released Control Switches

The HST-M range of solenoid controlled trapped key interlock switches are designed to control access to machines with run down times or when access to a safety door needs to be controlled by the Safety PLC. When the key is removed the power to the machine is isolated via a switch which is directly controlled by the key movement. This movement can however only commence when a signal has been sent from a control source to energise a solenoid which is locking the key in place. Once the solenoid is energised the trapped key can be withdrawn and used to continue on in an interlocking sequence. The HST-M units are available with multiple lock portions, varying switches for isolation, varying solenoid voltages for access permission and in either a cast aluminum housing or panel mounted version. The lock portions are manufactured of stainless steel and supplied with protective flip caps as standard.

Please see the application gallery for more examples of this product.


(HST-MTD) Mechanical Time Delay Units

The HST-MTD range of time delay units are designed to control access to machines with run-down times. In normal running condition the secondary keys are trapped in the unit, to release theses a primary key needs to be inserted and trapped. After inserting the primary key a pre-set timer runs down allowing the secondary keys to be withdrawn. The primary key remains trapped until all secondary keys have been returned to the unit. The HST-MTD units are available with varying run-down times and multiple lock portions. The lock portions are manufactured of stainless steel and supplied with protective flip caps as standard.

Please see the application gallery for more examples of this product.


(HST-TS) Single & Dual Key Access Interlocks

The HST-TS access interlock comprises a lock and locking bolt element and can be used on sliding or hinged doors. Single key units (HST-TS1) are designed for part body access whilst the dual key versions (HST-TS2) are used for full body access when a personnel key is required. For ease of mounting the HST-TS range is available in different housing orientations (left or right) and with either front or rear fixings. The locking bolt element can be supplied with a chain if the application requires. Manufactured of stainless steel and supplied with protective flip caps as standard.

Please see the application gallery for more examples of this product.


(HST-TZ) Single & Dual Key Slam Access Interlocks

The HST-TZ door interlock comprises a lock and slam-type locking catch mechanism. Inserting and trapping the key releases the catch allowing the guard to open. Locking the guard is done in reverse fashion with the catch being inserted by pushing the guard closed and turning the key. Single key units (HST- TZ1) are designed for part body access whilst the dual key versions (HST-TZ2) are used for full body access when a personnel key is required. For ease of mounting the HST-TZ range is available in different housing orientations (left or right) and catch entry from the front or rear. Manufactured of stainless steel and supplied with protective flip caps as standard.

Please see the application gallery for more examples of this product.


(HST-WA) Key Exchange Boxes

The HST-WA range of exchange boxes are used to increase the number of keys available in an interlocking sequence. The operating principle is such that no secondary keys can be removed from the unit until all primary keys have been inserted and trapped. The primary keys remain trapped until all secondary keys have been returned. HST-WA key exchange boxes are available in every possible combination of primary and secondary key numbers and are generally used for larger interlocking sequences. The lock portions are manufactured of stainless steel and supplied with protective flip caps as standard.

Please see the application gallery for more examples of this product.

Please note: This is only a small selection of the ISS Safety range of Trapped Key Interlocks, other variations and specials available upon request. ISS Safety employ technically qualified personnel who cover the UK. All of our safety engineers are qualified to "NEBOSH" National safety standards and are capable of providing advice on the use and application of the most appropriate interlocking system. To discuss a particular safety application or to receive a visit from one of our engineers please call us on +44 (0)20 8732 5505 or send an e-mail to [email protected].

STEP files available on request

Please contact us to receive a STEP (ISO 10303) file for use in your CAD project.