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Wireless E-stop required functionality on loss of signal

Wireless E-stop required functionality on loss of signal

(OP)
Could one of you point me to the right code / rule regarding wireless E-stop functionality?
Specifically - can a button be labeled "E-stop" on a wireless remote, if the system is designed to NOT shut down on event of a wireless failure? I am not seeing in NFPA 79.

I ask because the other wireless systems I have seen all are fail-safe, if any remote is not working the system will not operate. My system differs and I want to label it correctly / legally.

Electrical rating of my equipment in question is NEC C1D1. We have traditional hardwired E-stop buttons elsewhere in the system.

Thanks for any code references you can provide.

RE: Wireless E-stop required functionality on loss of signal

Most such switches that I'm familiar with in aerospace demand a minimum of a hard-wired, no-software, connection. Firmware/FPGA is OK, still needs to be hard-wired. There may be "convenience" interfaces that operate through a GUI, those are not considered to be reliable. Note that this applies to military applications.

However, as a secondary system, if wireless is unreliable, the you'd be getting a truckload of false shutdowns, if the system does as you suggest.

TTFN (ta ta for now)
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RE: Wireless E-stop required functionality on loss of signal

The only way to do a "wireless" emergency stop application that I am aware of is to use a Safety Controller that has been certified to use wireless Ethernet connections as safety circuits (there are a few out there certified for this). In those cases, the fail safe mechanism required for the certification would preclude the situation you are describing (as far as I know) because if the wireless connection goes down and someone hits that e-stop button expecting it to work and it doesn't, the safety application is deemed a failure.

But being Cl1 Div 1, are you sure you are not thinking of an ESD (Emergency Shut Down) system rather than "E-Stop" in the more traditional machinery safety sense? Different systems and applications. ESD as typically implemented in the Oil/Gas/Petrochemical industry is more about executing an ORDERLY controlled shutdown PROCESS, not "Emergency Stop", because immediately stopping something can be more dangerous on a wider scale. So an ESD system receiving a wireless signal from an ESD switch that loses the wireless connection would have multiple levels of redundancy to ensure that the loss of that signal doesn't trigger a shut down needlessly. If that's what you are thinking of, using the term "E-Stop" may be what's tripping you up.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

RE: Wireless E-stop required functionality on loss of signal

In Europe wireless crane controllers are commonplace. These are equipped with an E-stop function, and as cranes are fairly onerous in terms of safety legislation I imagine that the E-stop function has to meet a fair number of approvals. Different jurisdiction, but the technology exists - if you're allowed to implement it under your rules.

RE: Wireless E-stop required functionality on loss of signal

(OP)
jraef thank you. No this is not an ESD; we're a separate system from the facility. An ESD would cut power to our equipment.

You're 1st paragraph is spot on with my concern - is there a legal or otherwise requirement for the term "E-stop" to be fail safe? I want to know if we can or should call the button "E-stop" on the remote. If the wireless connection fails, we do NOT want it to automatically stop. The operator would just have to use the local controls.

Again I'm really just looking for the right code that defines this required behavior. Anyone know which code I need to look at?

RE: Wireless E-stop required functionality on loss of signal

(OP)
Update - after a good debate here we decided to make the wireless failsafe, with a bypass on the main control panel. The bypass completely disables the wireless control, yet we can still operate the equipment should the wireless controller be out of service.

I am still curious if wireless e-stops are governed by code somewhere.

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