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Why You Should Consider Illuminated E-Stop Buttons for Your Next Project BOM

GERRIE ROCKWELL AUTOMATION GROUP - Safety - June 2020

By Christian Bidner  

estop button

Illuminated Emergency Stop Buttons have been around for years, so why are we now hearing more about them?

Before I get into more details, lets discuss what an Emergency Stop does, and how it should be implemented into a Safety Function…

CSA Z432-2016 provides design guidance in section 7.15.1.1 “ …shall be fully in accordance with NFPA 79, ISO 13850 and IEC 60204, override all other machine controls, causing all moving parts to stop, and remove drive power from the machine actuators. Final removal of energy to the machine actuators shall be ensured and shall be by means of electromechanical components.

Exception: Drives or solid state output devices…”

Any time the standards says ”shall”, it is a requirement and not an option for the designer.

This tells me what it does, but what about Illumination?

First: CSA Standards do provide core requirements for Emergency Stop system designs, but further information and more detailed designs considerations can be found in ISO 13850 Emergency Stop Function- Principles of Design. Notice this standard is referenced in CSA above…

In ISO 13850 contains a section that pertains to Detachable or Cableless operator control stations (4.3.7) and inside this it details one of the measures to avoid confusion between active and inactive Emergency Stop devices:
Device color changing through Illumination of the active Emergency Stop device

This makes sense... If you are using a Cableless Pendant and you want to ensure the Emergency Stop is active, an LED indication would provide you with this feedback.
 Also, IEC 60204 Safety of Machinery-Electrical Equipment of the Machines-Part 1, stipulates that “Emergency Stop devices should be located at each controls station…” and that “There can be circumstances where confusion could occur between active and inactive emergency stop devices caused by disabling of the controls station. In such cases means shall be provided to minimize confusion.”(10.7.1)

Again, this makes sense, how to you know an Emergency Stop is active unless you can observe it. So, an Illuminated Emergency Stop could be one method to know it is active, on a panel.

To further this point:

Some large machines may have multiple Emergency Stops, and some of these could even be zoned for separate parts of the machine. To know which Emergency Stop device is active or has been activated, in what area of control, can be a challenge, especially if the devices are wired in series. A blinking LED verses a Solid LED can be a great way to know which device is active, and which may have been activated and now requires resetting. Visual indications like this would save time, confusion and help get a machine get back up and running faster. The more a machine runs the more productive it is, and the more money can be made.

Some plants have lighting problems that may leave the machine essentially in the dark... I have personally seen this several times, in different industries across Canada. Lighting may not seem like a big issue, while the machine is being built on a well-lit production floor. However, once the machine lands at a customer site, due to lighting, in can be a challenge to see all the push buttons and controls at a panel. Therefore, trying to identify an Emergency Stop switch, when looking at a panel with other lit devices may be a challenge and defeats the purpose of being “easily identified and actuated” per ISO 13849 (4.3.1). Having an Illuminated Emergency Stop button, would help eliminate the confusion and direct the eye to the correct device, when an emergency situation arises, and action on the part of an operator need to take place.

Though CSA Standards do not specifically call out for Illuminated Emergency Stop Push Buttons, ISO and IEC standards that are references in the CSA lead you in that direction.In particular ISO 13850 and IEC 60204. Both these build standards try to make the designer think about the safety function and the best way to help operators understand their machines. Therefore. Illumination of E-Stops is a great way to understand the current statues of the Emergency Stop Function, and what is needed to reset the machine, so a restart may occur.

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If you have any questions, please feel free to contact myself at Gerrie Electric.

Christian Bidner

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About The Author

Christian Bidner, FS Eng.TÜV Rheinland, Machinery 12038/16, is an experienced Safety and Machine Guarding Professional with over twenty years of experience helping customers develop solutions tailored to their needs

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