cisco_kid
Member
Regarding conveyor systems:
Our current design guidelines incorporate and Emergency Stop circuit to remove power to all output modules that control moving equipment. The PLC program is written to monitor the E. Stop circuit, among other things. An MCR is programmed, which must be reset using a START pushbutton following any stoppage, safety or other.
I was recently questioned by a new designer on whether or not it was wise to not use a hardwired MCR circuit. My interpretation of NFPA 79, 9.4.3.4.2 (2) would indicate that a programmable circuit is acceptable.
I read through a previous post in which there was much discussion of hard wired vs. programmable E. Stop circuit, but little discussion of the MCR circuit.
Any thoughts are appreciated.
Our current design guidelines incorporate and Emergency Stop circuit to remove power to all output modules that control moving equipment. The PLC program is written to monitor the E. Stop circuit, among other things. An MCR is programmed, which must be reset using a START pushbutton following any stoppage, safety or other.
I was recently questioned by a new designer on whether or not it was wise to not use a hardwired MCR circuit. My interpretation of NFPA 79, 9.4.3.4.2 (2) would indicate that a programmable circuit is acceptable.
I read through a previous post in which there was much discussion of hard wired vs. programmable E. Stop circuit, but little discussion of the MCR circuit.
Any thoughts are appreciated.