Emergency Stop

[LMAO]

I know that E-Stop is supposed to be fail-safe (most the time hardwired to to breaker UV) but is there actually any code/standard (NEC, CE, API, ABS, etc) explicitly requiring E-Stop to be fail-safe?
In other words, what prevents me from connecting the E-stop push bottom to a PLC to turn off a VFD?

Thanks

 

[justdavemamm]

See this thread:
http://forums.mikeholt.com/showthread.php/107746-Emergency-Stop-(E-STOP)-wiring-practice

 

[weressl]

I know that E-Stop is supposed to be fail-safe (most the time hardwired to to breaker UV) but is there actually any code/standard (NEC, CE, API, ABS, etc) explicitly requiring E-Stop to be fail-safe?
In other words, what prevents me from connecting the E-stop push bottom to a PLC to turn off a VFD?

Thanks

It depends on the definition of the E-Stop. The NEC does not deal with this.

ISA has some rules, definitions and methods to determine the reliability of safety systems.

ISA/ANSI S84.01 ? 1996, "Application of Safety Instrumented Systems for the Process Industries"​

In general terms neither a PLC - unless it is a specifically designed safety PLC - nor an ASD(VFD) are components that are recognized as valid parts of a safety-instrumented system. You would need a hardwired, special contactor - or 2 or 3, dependent on what safety level is required - to have assurance that you comply with the system stoppage requirements.