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Safety and SIS · Glossary

What is Safe State?

condition after a tripSafety and SIS

Safe state is the process condition a safety function must reach to prevent the hazardous event, such as a valve closed or a heater off.

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Safe State Explained

The safe state is defined in the SRS for each SIF. It may require several actions together, such as closing fuel valves and opening a vent.

Design must ensure the safe state is reached on loss of power or air, usually by de energise to trip logic and fail safe valves.

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Frequently Asked Questions

What is Safe State?

Safe state is the process condition a safety function must reach to prevent the hazardous event, such as a valve closed or a heater off.

Is shutting down always safe?

Not always; some processes need controlled shutdown or continued cooling. The safe state must be chosen by analysis.

What is de energise to trip?

Loss of power or signal causes the trip, so wiring failures fail safe.

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