Safety Relays CID2

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fifty60_4802GND

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I have an interesting puzzle of a problem. I am doing a study to find as many CID2 labelled components that I can. I am finding most everything that I intended to find. However, I am stuck on finding a safety relay. By safety relay I mean for an E-Stop circuit. I want to be able to monitor for welded contacts on the estop circuit. Traditionally I do this with a safety relay or a safety PLC. I am not finding any good CID2 options for this.

One thing I considered is using dual contacts from the Estop directly to cut power to the control power circuit. This would work great, but I would also like to have the monitoring for welded contacts that the Safety Relays provide. Anyone ever find a good approach to this? It seems like I pretty much have to locate the safety relay out of the hazardous area, or use purged/pressurization, or explosion proof enclosures.

To clarify, by Safety Relay I mean a dual channel input that monitors the inputs for simultaneous operation.
 
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fifty60_4802GND

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petersonra

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fifty60_4802GND said:
Hi Petersonra, not quite, I would like to find a safety relay that monitors the input for discrepencies like welded contacts. Basically two input have to be made and broken within a fraction of second or the output will not come on. Like this:
Click to expand...
solid state relays are not afflicted with contact welding.
 
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fifty60_4802GND

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I want to bring an estop into the safety relay. I haven't been able to find an estop with solid state. The estop actually has CID2 sealed contacts. I want to bring two NC contacts back to a CID2 safety relay
 
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fifty60_4802GND

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I can do everything that the Safety Relay can do except monitor the circuit for a failed contact. For example, a simple latching circuit that depends on two circuits ran through two seperate Estop contacts gives me redundancy in the safety circuit, all done in hardware.

However, the safety relay also has monitoring where if only one of the circuits breaks, it will not allow the output to come on after that single contact is made again. Both contacts have to make at the same time, both contacts have to break at the same time.

I cannot find a single CID2 rated safety relay that does this. I can definitely find SS safety relays, but they do not have monitoring.
 
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petersonra

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fifty60_4802GND said:
I can do everything that the Safety Relay can do except monitor the circuit for a failed contact. For example, a simple latching circuit that depends on two circuits ran through two seperate Estop contacts gives me redundancy in the safety circuit, all done in hardware.

However, the safety relay also has monitoring where if only one of the circuits breaks, it will not allow the output to come on after that single contact is made again. Both contacts have to make at the same time, both contacts have to break at the same time.

I cannot find a single CID2 rated safety relay that does this. I can definitely find SS safety relays, but they do not have monitoring.
Click to expand...
latching circuits are never found in a safety circuit. You keep talking about bringing in an "estop", presumably an estop PB. Then you talk about welded contacts. That would be an issue with power relays. Why don't you sketch up what it is you want with a regular safety relay and note the part you cannot get.
 
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fifty60_4802GND

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The Estop PB has two of NC versions of the below contact. My understanding is that the safety relay is monitoring for both sets of these contacts to make and break simultaneously. If only one breaks, the machine will shut down but will not be allowed to start up.

Would welded contacts not be an issue with these because there is no coil involved with them? I know a coil not being energized correctly can weld the contacts....

1590158433611.png
 
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petersonra

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engineer
fifty60_4802GND said:
The Estop PB has two of NC versions of the below contact. My understanding is that the safety relay is monitoring for both sets of these contacts to make and break simultaneously. If only one breaks, the machine will shut down but will not be allowed to start up.

Would welded contacts not be an issue with these because there is no coil involved with them? I know a coil not being energized correctly can weld the contacts....

View attachment 2552440
Click to expand...
contact welding has zero to do with the coil at all. it has to do with a contact literally being welded together so it cannot open. this is usually due to a failing contact or possibly due to excess current. you might, and i say might, get contact wear if the coil is intermittently energized, which might eventually lead to contact welding. the chances of getting welding in a PB wired to a safety relay approaches zero. In any case it would be detected if one contact was on and the other off and it would fault.

I think I have finally figured out what you really want. I am not aware of a safety relay that is listed for C1D2.

It would not be real hard to put the safety relay inside a small XP enclosure though.
 
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