ESD system - Interposing Relay Panel - SIL Capable

Hi to all,
I guess somebody could answer to my silly question:
I have to build an interposing relay panel as MCC and DCS and ESD system, the question is:
I have to use SIL certified relay on my IRP panel for ESD TRIP functionality vs MCC system ?
Thank you.
 
Whether you use SIL certified relays depends entirely on your client’s specific requirements - they do not have to be certified. If you work on the KISS principle (stupidly simple), you could argue certified relays give you another level of complexity which may / may not be advantageous. There is also an argument in the design as to how a relay would ‘fail to danger’......highly unlikely but not impossible.
In any system it is possible to obtain SIL2/3 calculations whilst using non-certified relays - however if your client doesn’t like the idea they‘d soon let you know !
 
Beware, if SIL calcs are being done the interposing relays can be quite punitive to the outcome.

Also, depending if you are in the same room or not, sometimes the line monitoring is desired to be preserved (it won't pass thru the relays) and you need special relays for this, last lot I bought were not off the shelf.
 
Hi to all,
I guess somebody could answer to my silly question:
I have to build an interposing relay panel as MCC and DCS and ESD system, the question is:
I have to use SIL certified relay on my IRP panel for ESD TRIP functionality vs MCC system ?
Thank you.
Hi Peter,

I think the other responders have the perfect question back: What is the customer requirement? Generally, SIL is thrown around industry as a basic safety "catch-all" without defining the requirements. Here are some follow up questions I would have for your customer:

If the panel you're building needs to be an ESD, what standard is being required? (IEC 61508, IEC 61511, ISO 13849-1, IEC 62061, etc.)

Based on the standard required, there may be many paths to achieving the requirements of functional safety. Does the customer have a Functional Safety Management (FSM) plan or process? How will the system you are building fit into that?

These two questions should give you a lot more information on what is expected from the system. A general rule of thumb though, if you are creating a ESD system, you should specify to which standard it was designed, and include any calculations required or independent certifications done.

As far as using SIL rated relays go, just adding them to a system won't make your system safe. Safety of a system is a function of all of its parts (one of which could be a safety relay) for a single safety instrumented function (SIF), and then it all rolls up to a Safety Instrumented System (SIS). Using safety rated relays can make approximating calculations required for these systems easier, but its also important to make sure they are being applied correctly.

tl;dr - More information is probably needed to answer this correctly. If you are using a safety rated relay, it may help estimate what type of risk reduction can be expected, but ultimately it is only a small piece of the overall safety calculation.

I hope this was helpful

I hope this helps
 
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