# Does IEC61511 allow an ESD system on a control network?

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#### PC Tan

I came across a technical specification which mentioned "The IPS (Instrumented Protective System aka ESD) shall not have a direct connection to the PCN (Process Control Network)." That means that any connection of the ESD system shall be via the DCS controller. The PCN is a network where other subsystems such as MOV systems, TGS systems, CCTV systems etc also reside on. Is this requirement mandated by IEC61511 or is it this particular specification's requirement?

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#### Ikhtiander

Hi PC Tan,

On IEC61511 11.7.3 Communication Inteface Requirements (2) only stated that:

"The SIS shall be able to communicate with the BPCS and other peripherals with no impact on the SIF"

So no specific requirements that the network connected SIS and BPCS should be separated from network connected BPCS to other peripherals (like HMI, flowmeter, etc) with condition that the network communication performance have no impact to SIF. Regarding impact to SIF, I mean, network PFD-contribution not compromising the overall SIL of the complete safety function.

Hope this help

Aan

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#### PC_Tan

Thanks Ikhtiander. Yes, it helps tremendously.