FGR's and SR's

So everyone wants to do things the right way but we have to try and stay cost effective. I've been scouring the internet recently looking for a good/reliable/cost effect set of safety devices I'd like to try and use for most if not all of my jobs.

Does anyone have a favorite Safety Relay for General purpose like a few E-Stops and a light curtain? Also what Force Guided Relays do you like to use?

Thanks

I thought safety relays were force guided? I thought that is what makes them safe?

Yes and no...

The SR (Safety Relay) doesn't always have force guided contacts, it has redundant safety monitoring channels that have to make and break within an allotted time of each other to enable all other relay circuits to open/close. There are some safety relays which use transistor outputs for their circuits but those are not force guided.

FGR's (Force Guided Relays) are those whose relay circuits are mechanically linked so that they cannot operate independently of the others. This prevents any circuit that is welded shut to allowing others from opening or closing. If you design your safety circuit correct so the External reset of the SR is in series with the N/C circuit of the FGR(s), when you try to re-enable the SR again the N/C circuit on the FGR will be OPEN from another welded shut contact preventing the SR from enabling.

So while there may be some SR's out there that have an SGR circuit they are not the same.

i have used banner and piltz.

regards,
james

Tim Ganz said:

I thought safety relays were force guided? I thought that is what makes them safe?

Click to expand...

The importance of having force guided contacts has nothing to do with making the relay safe. It is about making the relay "monitorable". A "safety monitoring relay" is then used to evaluate whether the relay is functioning as expected. By having force guided contacts it creates the necessary conditions for which the monitoring relay needs to detect failure.

Redundancy is a different matter all together. As far as power side switching is concerned I don't think it should be allowed to have redundant contactors or such without also monitoring the contacts. The reason is simple, if one of the two contactors fails welded and you don't monitor your redundancy is gone and you have no way of knowing. Now you have a situation where there is a false sense of security. I think it should be mandatory for all redundant contactor setups to also have monitoring, otherwise you are contradicting the assessment that the redundancy was important in the first place.

For small stuff we use the Omron G7 series. The are very inexpensive and are an easy way to effectively expand the number of output contacts on a safety relay.

http://www.omron-ap.com/product_info/index.asp?catlvl=171

I have used Jokab quite a bit that was recently absorbed by ABB.

Damian, thanks I did know that it was to make the circuit monitor able, I misspoke. I was looking for an FGR that I could use in high current applications, ie. breaking bus current for a servo motor. I scoured the internet and found these beauties and thought I'd share them with the rest of the world.

16A continuous circuit rating, 24vdc 1.2w coil, $40 dollars from HH Barnum in Michigan.

http://www.calcentron.com/Pages/AEGHomePage/aeg_contactors/aeg_contactors_home.htm

Going to be my new go to relay.

The model number I chose was the SH05.31-NSW, also offers a nice add-on for surge suppression.