Safety Instrumented Systems Design & Validation Flashcards
7 cards from real SIL practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Safety Instrumented Systems Design & Validation flashcards as text
What is the primary purpose of a Proof Test in an SIS?
Answer: To verify that the SIS will perform its safety function on demand
A proof test is a periodic test performed to reveal dangerous undetected failures, confirming the SIS can perform its intended safety function on demand.
Which IEC 61511 clause governs the Management of Functional Safety for SIS?
Answer: Clause 5
IEC 61511 Clause 5 addresses the Management of Functional Safety, including the safety management system and competency requirements.
During SIS design, what does 'architectural constraints' refer to in IEC 61511?
Answer: Hardware fault tolerance requirements based on SIL and safe failure fraction
Architectural constraints define the minimum hardware fault tolerance (HFT) required based on the target SIL and the safe failure fraction (SFF) of the subsystem.
A 1oo2 voting architecture means the SIS initiates a safety action when:
Answer: At least one of two sensors detects a hazardous condition
In a 1oo2 (1-out-of-2) architecture, a safety action is triggered when any one of the two sensors detects the hazardous condition, improving availability.
What is 'Systematic Capability' (SC) in the context of SIS hardware?
Answer: A measure of the device's ability to avoid systematic failures based on its development process
Systematic Capability (SC) rates a device's resistance to systematic failures, reflecting how rigorously the device was designed and manufactured to IEC 61508.
Which document formally records the results of an SIS validation and confirms it meets the SRS?
Answer: Validation Test Report (VTR)
The Validation Test Report (VTR) documents the validation activities performed and confirms the SIS meets all requirements defined in the Safety Requirements Specification.
In SIS design, what is the significance of the 'demand rate' on SIL selection?
Answer: Higher demand rates require higher SIL to achieve the same risk reduction
A higher demand rate means the SIS is called upon more frequently, so a higher SIL may be needed to maintain the same acceptable residual risk level.