OT- safety relay or controller

http://www.ab.com/en/epub/catalogs/3377539/5866177/5985760/4444281/4444297/3383747/print.html

With regard to the Allen-Bradley Sipha 1 control unit;

Is it a safety relay or control unit?

The text states that:

The Sipha 1 control unit operates on 24V AC/DC and offers one normally open safety output...

Click to expand...

and

Safety Classification Sipha 1 & 2: Cat. 3 per EN954-1

Click to expand...

... which leads me to believe its a safety relay yet a couple of colleagues are saying its not a safety unit so can be over-ridden.

The units are on a bottle labelling machine.

Please share your views on this. Thanks.

Every other word on that page is safety, so I don't know why your colleagues don't feel it's a safety device. If you remove the index.html suffix from your link, you get this page:

http://www.ab.com/en/epub/catalogs/3377539/5866177/5985760/4444281/4444297/3383747/

Notice the directory listing at the top of that page...

Catalogs > Safety Products Catalog > Logic > Safety Relays > Specialty Safety Relays > Sipha™ Control Units

If AB calls it a safety relay, then it's probably a safety relay.

By the way, these are made by STI (now part of Omron), so you might want to compare pricing with the identical unit (sans the AB logo) sold by Omron.



-Eric

Thanks Eric

They seem to believe that the units are there for positional purpose, so that the machine can't operate without the modules placed in the docking stations and sensed by the coded sensors.

The term 'Control Unit' perhaps confuses... without reading the specs.

Another phrase I recall being used "... they protect the machine...".

I think your colleagues questioned these because they are non-contact (magnetic) switches, rather than the typical removable key (mechanical) switches. I somewhat question these too. I've always used the traditional guard switches with the separate key. The removable key units physically open the contacts, so I don't know how the magnetic switches achieve the same thing. Maybe just with redundant contacts? In any case, I think they meet the same safety specs. as the keyed units, so they should be okay...



-Eric

I blieve that they have coded magnets in them, you cannot just pu an ordinary magnet on them.

Alan

Many of these type are rfid coded meaning the magnet has a rfid chip in it and a regular magnet will not work nor a magnet from another switch. When any part of the unit goes bad you have to change both parts or it will not work. They are a matched set.

The Sipha sensors are magnetic and they are junk in my opinion. We replaced a Sipha system with a Sensaguard (RFID) and it is much improved. Now, our only issues have been with connectors (wash down environment). With the Sipha, we would often see a failure on one of the safety contacts, while the monitoring contact would remain in the ready state. It made troubleshooting a crapshoot. With the Sensaguard, I have not seen the individual contacts get into opposing states. They always seem to work together like they're supposed to...