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SIL 2 VSD

Rob Eagle
Anyone know who else does Variable Speed Drives (VSD), other than the Siemens (G120), that can contribute to a SIL 2 safety function?  Even better if they have EMPHASIS certification as well.  Looking for a 7kW drive.


By the way BS EN 61800-5-2 refers to them as PDS(SR)s.


Thank you.


Rob
  • 0
    Hello Rob,


    Could you give some more details about the application please? You could use almost any VSD as part of a SIL2 safety function depending on how it was implemented. The Siemens G120 has some additional intelligence in the control unit I think, I don't know the model well though.


    Jonathan
  • 0
    Hello Jonathan,


    Sorry, should have said that the VSD shall perform the safety function in a continuous demand mode.  The safety function requires the VSD to continually control the speed of a fan on a nuclear vent system, the safe state is the fan running in a controlled manner to maintain dynamic containment for a glovebox.


    Rob
  • 0
    I'm afraid I've no experience with safety functions for continuous demand mode, so I can't offer any specific advice.


    Just out of curiosity though, in your application is the VSD control unit actually performing the evaluation of the inputs to the safety system (i.e. that the fan is running in a controlled manner)? Or is the VSD (or external sensors) giving an input to the safety system (your safety PLC/DCS/relays) which is then evaluating the inputs against the safe operating condition?
  • 0
    Having thought through this a bit more a standard high quality VSD would be more suitable as I need high availability rather than high safety, a 'Safe' VSD will probably reduce overall availability due to its design intent to move to a safe state on detection of the slightest error and with its greater complexity this is more likely.


    Two independent fan units, duty/standby, with a SIL 2 duty changeover controller is the current thinking.


    Thanks for you help.

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