Emergency Stop Usage

[jakeparsons03]

We are starting to look into placing e-stops for different kinds of machinery throughout a new chemical plant (all green space as of today). My main goal is to make sure that their plan (whatever that may be) is code compliant. I have a few questions to clarify from the research I have done.

1. From what I read E-Stop locations must be determined by an accredited risk analysis. Is this right?
2. When I have put in E-stops in the past I have wired them in line with the starter command signal. Category 0 E-stops are required to physically remove power from the system. Technically, removing power from the starter opens the relay on the motor causing power to be physically removed. Is that considered a Cat-0 Stop?

 

[petersonra]

e stops are not a category zero stop. A disconnect switch is a category zero stop.

What makes you think you even need an eStop push button?

 

[EC Dan]

Not sure I agree with that. Isn't a push button E-Stop in conjunction with an emergency stop safety module considered category 0? In our applications, the safety module interlocks all contactor coil circuits and VFD enable circuits, so although it does not directly cut-off the power circuit it seems to me to satisfy the conditions of category 0 stop.

 

[BillyMac59]

An e-stop is a catagory 0 element as per the Pilz training I took last week. Your risk assessment will determine the need for their usage and location. Once you determine your minimum requirements based on the RA, you can investigate the desire for more stringent control versus the expense.

 

[petersonra]

I think you are right about a contactor that immediately removes power being a category 0 stop.

My brain was somewhere else while I was typing.

I was thinking along the lines of a VFD where the estop is wired into either the enable or the safe torque off function. Those are not category 0.