SACA Safety Systems and Functional Safety 4

Question 1

What does the term 'safe state' mean in the context of functional safety?

Accepted Answer

A condition in which the system does not pose an unacceptable risk

Answer

A safe state is a defined operating condition in which a system no longer poses an unacceptable risk, even if it cannot continue normal operation.

Question 2

In IEC 61511, what is the primary purpose of a Safety Instrumented Function (SIF)?

Accepted Answer

To bring a process to a safe state upon demand

Answer

A Safety Instrumented Function is designed to bring a process to a safe state when a predetermined condition is detected, preventing or mitigating a hazardous event.

Question 3

Which failure mode is addressed by 'deenergize-to-trip' design philosophy in safety systems?

Accepted Answer

Power supply failures causing loss of safe actuation

Answer

Deenergize-to-trip ensures that loss of power causes the safety actuator to move to the safe position, preventing power failure from leaving the system in a dangerous state.

Question 4

What is the purpose of proof testing in a Safety Instrumented System?

Accepted Answer

To detect dangerous undetected faults and restore the PFD to its initial value

Answer

Proof testing exercises the full safety function to reveal dangerous undetected faults and reset the probability of failure on demand (PFD) accumulation.

Question 5

In a redundant 2oo3 voting architecture, how many channels must agree on a fault for a trip to occur?

Accepted Answer

2 out of 3

Answer

In a 2oo3 (two-out-of-three) voting system, at least two channels must detect the hazardous condition before the system initiates a protective action.

SACA - Smart Automation Certification Alliance Practice Test

SACA - Smart Automation Certification Alliance Practice Test

SACA Safety Systems and Functional Safety 4