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Anti-tamper mechanism on trapped key interlocks

A Rockwell Automation - Allen-Bradley Guardmaster product story

Edited by the Engineeringtalk editorial team Nov 21, 2001

The new Guardmaster-Prosafe range of electro-mechanical trapped key interlocks are manufactured from 316 stainless steel and have a unique anti-tamper mechanism

Guardmaster is consolidating its position as a full solution supplier for machinery safety equipment with the introduction of the new Guardmaster-Prosafe range of electro-mechanical trapped key interlocking and control solutions.

Units in the Prosafe range are manufactured from 316 stainless steel and have a unique anti-tamper mechanism which makes them the most practicable method of safety power interlocking for installations in a wide range of industries: - process, nuclear, automotive, machine tools, brick and block - where safe access to hazardous areas is required, following the electrical/pneumatic/mechanical isolation of machinery.

By using a combination of Guardmaster-Prosafe system components, virtually any safety interlocking or operational sequencing requirement can be catered for - with the added advantage that electrical wiring to a safety gate, hatch or door is not required.

The Prosafe mechanical design, based upon the premise that no one key can be in two places at once, enables the key interlocks to be configured to ensure a predetermined sequence of events takes place, or that hazards have been reduced before operators can become exposed to them.

The Prosafe range is fully inclusive, satisfying the bulk of mechanical interlocking requirements with a series of complementary products, including isolators, key exchange units and lock out/tag out devices, all of which employ the same dependable key principle and are tested to 100,000 operations (equivalent to 27 years service at 10 operations per day).

This inbuilt reliability, combined with a robust, corrosion resistant construction, means that the Guardmaster-Prosafe range is ideal for use in applications where the environment is arduous or aggressive, and in applications where the nature of the atmosphere (i.e explosive) makes the use of other electrical interlock systems impractical or expensive to install.

In these, and indeed, all types of operating environments, the unit's excellent environmental credentials are further improved with a weather cap and key seals.

In addition, unique colour-coded keys and ID tags can be provided, adding to a greater degree of security and tamper-resistance.

Interlocks in the Guardmaster-Prosafe range are offered in single key and dual key access configurations, both of which have unique stainless steel coded keys and barrels to satisfy even the most complicated of interlocking systems.

The units have a direct drive mechanism to give the positive operation described in the "Safety of Machinery" standard BS EN 292.

They are CE marked and are fully tested and approved to standards EN1088, IEC 60947-5-1 and GSET 19.

In addition to these approvals, the Guardmaster-Prosafe range is the only one to carry the prestigious BG mark, a sign of safety, independently tested by the German Berufsgenossen-schaftliches Institutfur Arbeitssicherneit, 'BIA'.

The BG mark is complemented, while switches and sensors within the range carry the necessary 'BASEEFA' approvals, and isolator switches UL, CSA and TUV approvals.

The Guardmaster-Prosafe single key access units are designed for the interlocking of hatches, guards and doors on machines where full body access is not required.

With single key access units the key, after it has been turned to release the guard locking unit, remains trapped and cannot be removed until the guard is closed and locked again.

Therefore, it is impossible to open the guard without first isolating the power source, and it is also impossible to switch on power to the machine without closing and locking the guard.

Guardmaster-Prosafe dual key interlocks are designed for applications where full body access to an enclosure is required.

They can be used in one of two modes: Sequential Key Exchange, with one key in and one out, or Dual Key Insertion with both keys trapped to operate.

In the former mode, one key, the primary, remains trapped after being inserted and rotated.

The secondary key is then inserted and turned, allowing the guard to be opened.

The secondary key can now be removed and used as the next stage of an interlocking sequence for a robot teach mode or be retained as a personnel key to ensure that machinery cannot be restarted whilst the key holder is inside the hazard area.

Further details of the new Guardmaster-Prosafe range are contained within the new EJA/Guardmaster catalogue, which is also available on mini-CD for maximum convenience.