Switchgear and protection: trapped key interlocking vs LOTO

There are two potential options when considering a mechanical safety system for switchgear applications. The choice is between a trapped key interlocking system or a padlock-based lock-out / tag-out (LOTO) system. Both systems:

  • Provide a method of isolating switchgear.
  • Allow safe personnel access when maintenance of machinery is required.
  • Are available in full stainless steel or brass versions.
  • Offer a comprehensive range of products with different forms and sizes to suit the needs of the equipment concerned.

However, in terms of safety, trapped key interlocks (TKIs) offer significantly higher levels of protection compared with LOTO.

Trapped key interlocks safeguarding a switchgear installation

This is due to the four reasons given below:

  1. TKIs are durable with a proven track record of withstanding harsh operating environments through decades of operation.
  2. TKI’s force workers to follow a strict process which prevents them from deliberately skipping or inadvertently missing steps. The equipment is interlocked together in such a way that steps cannot be overlooked or ignored.
  3. In an environment where staff may be unfamiliar with operations and speak a range of different languages, the enforced procedure of TKIs negates miscommunication or misunderstanding of operating practice.

    Misunderstandings are a risk when staff speak a range of different languages

  4. When there is a need for full-body access, TKIs provide a personnel key that protects workers from potential danger and puts them in control of the process. Until the personnel key is returned, the switchgear cannot be returned to the live state.

By: Adam Felton, Technical Marketing, Castell Safety International Ltd.

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