AS-I safety

Hi. Has any one had any experience with a schneider AS-I safety system. That is are there any glaring pitfalls etc. Regards Alan Case

We evaluated ASI safety systems a short while ago.

Personally I am sceptical about reliability. It seems to me (at least from the way it was described) that the sysstem sends multiple messages over the bus, and if an error is detected it will fail safe, i.e it will trip or estop.

Now we have been using ASI bus for machine I/O for about 2 years now. It's simplicity and ease of adding extra I/O is great. But it's not without it's problems. One problem I experienced a while back was a single I/O module that would very occasionally fail to communicate over the bus properly. When I say very occasionally I mean once or twice a day. It was a bugger of a fault to fix. Substituting a new module did not fix it. Disconnecting a lot of other modules on the bus did not fix it. It turned out to be a simple grounding fault in the end, we had grounded the I- of one of the sensors, and because the I+ and I- are derived from the ASI bus, it didn't like that.

So my point is, had we been using ASI safety bus in that instance, we would have had a spurious estop occurring once or twice a day. Not many customers would tolerate that.

Also, we supply machines for use all round the world. A lot of our customers are particularly cautious about safety systems, and is one area they usually examine in detail. Not one that I have yet mentioned it to would accept ASI safety bus. They all want a traditional hard wired circuit to a tried and tested make of dual circuit safety relay.

It's certainly a system to keep an eye on for the future, but at the moment it doesn't have sufficient industry acceptance.

ASi-safe

I've used ASi safe many times with no real problems. It was the Siemens package (monitor, estops and guard modules).
I've used it with S7-200 and 300 plc's, and there's an ASi master available for the SLC (made by SST). (Never used this - does anyone know if it's any good?)
End users have been somewhat sceptical as to its safety (philistines) but achieving category 4 safety is in excess of what we'd offer using traditional methods.
I'm not sure what happens if a module (EStop for instance) goes down as each is coded and the monitor is 'taught' these codes. Apparently it is possible to replace a module without a laptop but I've never done it.
I found it is still fairly new technology and tech support wasn't great, but after commissioning one system it is pretty straight forward.
We sell a lot of machinery to the US, but not with ASi safe. How would it be received?

We have been using the AS-i system here at the company I work at in Canada with great success. I've done about 4-5 projects myself and there is a rather good interface that WoodHead SST makes for both PLC5 and the SLC 500. To this day, we have had very little issues with the AS-i system.