Safety Circuit for Rotating Machinery

[kallen88]

Hello Everyone,

Just a quick question regarding safety stopping function of a rotating machine control system. Say I have 2 solenoid locks on two different movable guards and 2 e-stop buttons. I want to design a CAT 3 system to bring the rotating machine to a controlled stop with removal of power if either the doors are opened (manually overridden) or e-stop has been pressed.

Is it accepted practice (in Australia) to wire the e-stops and solenoid locks (terminals that indicate both closed and locked state) all in series to a single safety relay to achieve a CAT 3 system? Or do the e-stops and solenoid locks need to be on separate monitored systems?

Our control equipment supplier insists they need to be separate systems so he can supply us with 2 safety relays and a bunch of other equipment instead of just the one. Trying to cut down costs on this one so need to know if he is correct or trying to squeeze more $ out of me.

Thanks,

Kallen.

 

[controlsdude]

If you press the estop, then maybe you need to do a controlled stop.
You need to distingush between the estop being pressed and the door opening.
Do you monitor each device or just the string of devices at the relay? I would think you would want to monitor all devices seperatly to tell the operator which device is tripped.
As far as safety monitor, the operation of estop pb I think if you want to bring machine to controlled stop, you would want these devices seperate from a solenoid locked monitored door.

How does a solenoid lock door just by chance open? Solenoid should hold the door shut till the machine is in a safe state, then the door is solenoid opened or unlocked.

The above statements are true?

I think the OEM is justified in seperate relays to get you cat 3.

 

[ScottyUK]

Cat 3 to what standard? Sounds like the old (and obsolescent) EN 954 which was fairly explicit about performance requirements for each category. The replacements - ISO 13849-1 and EN 62061 - are far less friendly documents. Although they are more complete from a technical perspective than EN 954 I do wonder whether they have been made so awkward to apply that many practising engineers are simply ignoring them and persisting in using EN 954 instead. Something for the authors to consider in future perhaps.

You might find the following documents from Schneider helpful:

http://www.schneider-electric.co.uk/documents/legislation/Machine-Safety-Guide.pdf

http://www2.schneider-electric.com/documents/support/white-papers/WPB2110604EN_LR.pdf

My opinion is that you probably need two independent channels to achieve Cat 3 using normally-available components, but you might first want to check that you aren't working to a standard which has been superceded.