SIL Safety Lifecycle & Management 3

Question 1

In IEC 61511, who is ultimately responsible for ensuring the safety lifecycle is properly implemented for a safety instrumented system?

Accepted Answer

The process owner / asset owner

Answer

IEC 61511 places ultimate responsibility for implementing and maintaining the safety lifecycle on the asset owner/operator.

Question 2

What is the term for the maximum allowable probability of failure on demand for a SIF operating in low-demand mode at SIL 2?

Accepted Answer

≥10⁻³ to <10⁻²

Answer

SIL 2 in low-demand mode requires a PFDavg between 10⁻³ (inclusive) and 10⁻² (exclusive).

Question 3

When a modification is made to a Safety Instrumented System during operation, which lifecycle activity MUST be triggered?

Accepted Answer

Management of change (MOC) process

Answer

Any modification to a SIS must go through a formal Management of Change process to assess impact on functional safety before implementation.

Question 4

What does 'architectural constraints' refer to in the context of IEC 61511 SIL verification?

Accepted Answer

Hardware fault tolerance requirements based on safe failure fraction and SIL target

Answer

Architectural constraints in IEC 61511 link Safe Failure Fraction (SFF) and Hardware Fault Tolerance (HFT) to determine the maximum achievable SIL for a given hardware configuration.

Question 5

Which of the following best describes 'demand mode' operation of a Safety Instrumented Function?

Accepted Answer

The SIF is activated only when a hazardous condition is detected

Answer

In demand mode, the SIF remains dormant and activates only when a process demand (hazardous event) occurs.

(SIL) Safety Integrity Level Certified Practice Test

(SIL) Safety Integrity Level Certified Practice Test

SIL Safety Lifecycle & Management 3