Hi All,
I want to know about what NFPA 85 standard says regarding configuration of 2oo3 logic for a safety PLC.
Particularly, if there are 2 out of 3 transmitters/switches installed in a boiler for any tripping security (like furnace draft, inlet header pressure etc.), is it necessary to connect it to 3 different I/O cards in a Safety SIL-3 PLC? E.g if a digital input card in a safety PLC has a capacity of 16 inputs, and has TMR architecture with no single point of failure, is it still necessary to input the 3 input switches operating in 2oo3 configuration in 3 separate DI cards? Or can we connect all 3 switches in a single DI card?
Please inform in light of NFPA 85, or any other standard governing boiler safety control.
Thanks.
I want to know about what NFPA 85 standard says regarding configuration of 2oo3 logic for a safety PLC.
Particularly, if there are 2 out of 3 transmitters/switches installed in a boiler for any tripping security (like furnace draft, inlet header pressure etc.), is it necessary to connect it to 3 different I/O cards in a Safety SIL-3 PLC? E.g if a digital input card in a safety PLC has a capacity of 16 inputs, and has TMR architecture with no single point of failure, is it still necessary to input the 3 input switches operating in 2oo3 configuration in 3 separate DI cards? Or can we connect all 3 switches in a single DI card?
Please inform in light of NFPA 85, or any other standard governing boiler safety control.
Thanks.