Integrated Estop Systems (PB label)?

[Roboteck]

Hello,
If I have two (2) conveyor systems back to back(one is feeding the other). Can I design two separate Estop systems, so that Estop system #1 if pressed will shut down both systems? And Estop #2 will shut down only system 2. If that is the case, can the Estop hardware (mushroom buttons and colors and labeling) be the same or should (must) they be different?
is there any code (NEC/NFPA etc) that can be of help regarding this matter?

 

[jraef]

NFPA 79 covers machine safety.

Yes you can do what you want. The simplest logic would be as follows; Motor starter 1 (M1) feeds the conveyor motor in system 1 as above, M2 feeds the motor in system 2, the one that can shut down independently. Have ES1 feed the control power to M1, then downstream from the contact of ES1, feed control power to ES2. Have ES2 feed control power to M2. If ES1 is pushed, control power is cut to both systems, if ES2 is pushed, only M2 gets dropped out, M1 stays on.

No the E-stops do not need to be different, but you may want to do that anyway just so your operators can tell the difference (if that's important). One suggestion would be to have a "twist-to-release" E-stop for ES2, as a reminder to whomever wants to restart it that system 1 must be started first (assuming system 2 feeds into system 1).

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[powerjunx]

Roboteck, better to include audible and visual annunciation with your customize design of E-stop.

"Whenever you are asked if you can do a job, tell them, certainly I can! Then get busy and find out how to do it." Theodore Roosevelt.

 

[controlsdude]

I have designed and seen what other people have done on conveyor estops. ESTOP zones are all customer driven. But you need to take the safest approach in designing any estop system. If an estop PB is located in an area that estop will shut down any machine within view.

I know if you have conveyor on a floor with operators present a pb needs to be present on the side of the conveyor. But I advise you to use pull cords which are much better than an estop since the operator is not confused on what he is shutting down. OSHA gives you the option for either, but I recommend pullcords.

I would not advise having a conveyor system and it not shutting down the whole area. This will always confuse operators and cause confusion during an emergency. Thats all you need is someone 20 feet away and someone see it pushes your zoned estop but that equipment 20 feet away does not stop and that person is screaming bloody murder until the operator finds the right zoned estop.

Remember estops for emergencies and only emergencies. Stop buttons are for stopping areas. Maybe you need to add more pushbutton stations instead of zoning estops.

If you feel that the area can be divided into two area, then design it for two areas. Then interlock the two areas so that both zones can be easily separated into 2 zones if the customer is not happy.

I have had this argument that NFPA 79 does not cover conveyor systems but machine unit operations. Just remember its you on the witness stand when someone is sueing you because you did not take the safest approach to safety.