Understanding the standards for safety guard switc...
Interlocking devices associated with guards
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New safety standards clarify how to select safety guard mechanical switches and how to diagnose if their series wiring creates a dangerous fault masking situation.
On April 30, 2015, the standard “ISO 14119 Safety of Machinery – Interlocking Devices Associated with Guards” goes into effect and it will give the machine builder and end user better guidance on switch selection and new technology.
It is common for machine builders and end users to wire their mechanical switches in series and in many cases not realize they are reducing their safety coverage due to “fault masking”.
New technology and stronger worldwide harmonization of standards has led to the most significant standard change for interlocking devices since 1995. The original standard “BS EN 1088:1995 Safety of Machinery – Interlocking devices associated with guards. Principles for design and selection” is being replaced by ISO 14119.
Additional clarification of diagnostic coverage calculations to meet ISO 13849‐1 will be provided in the technical report “ISO/PDTR 24119 Safety of Machinery – evaluation of the fault masking serial connection of guard interlocking devices with potential free contact” which as of March 2015 is currently in development.