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Lockout-Tagout standards

Lockout-Tagout standards

ISO 14118 “Safety of machinery” and the US standard ANSI/ASSE Z244.

These two international standards describe the application of “Zero Energy” (No-voltage principle to avoid hazards when operating machines).

ISO 14118: Safety of machinery - Prevention of unexpected start-up

(2017)ANSI ASSE Z244.1: The Control of Hazardous Energy* Lockout, Tagout and Alternative Methods (2016)

The definition “Hazardous Energy” includes not only electrical energy but also pneumatic energy, hydraulic energy, gravity and chemical combustion gases. The definition of “Zero Energy” is described in the standard as: “De-energised principle to prevent hazards in the operation of machinery”.

The principle of zero voltage in machinery and equipment can be described as followed: When accessing the safeguarded area of a machine, all energy is isolated, all (residual) energy is dissipated and you prevent anyone from re-enabling any part of it by placing personal lockouts (lockout) on the energy source. For identification purposes, a marking (tagout) should be placed and a check should be made that the part affected by the work is indeed de-energised (tryout).

Is Lockout-Tagout mandatory?
In countries such as the United States, Canada and the United Kingdom, social laws (health and safety legislation) require the application of a Lockout-Tagout method. This makes its application in these countries a direct obligation to comply with the law. In many other European countries, “Zero Energy” is defined in technical standards (such as ISO 14118), which makes applying Lockout-Tagout not a direct obligation but a recognised way to comply with the standard.

Alternative Methods besides LOTO
When working on machines, Lockout-Tagout cannot in all cases be applied as it is not always possible or desirable to completely de-energise. For example, consider access to a robot cell where a robot needs to be programmed. Here, the movement is stopped by installing safety-controlled components in the control current that prevent (re)activation through redundancy via the safety circuit. These components must be deployed according to functional safety standards such as EN ISO 13849-1. Intervention in control flow = functional safety Isolating the energy source = Lockout-Tagout
lockout tagout standards

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