FSOE Written Test flashcards

35 cards. Read the term and the definition here. The deck at the top of this page is optional.

Functional safety management

The set of planned and systematic activities needed to achieve and maintain functional safety throughout the safety lifecycle, including planning, competence, verification, and configuration management.

Functional safety assessment

An independent, planned review that judges whether the functional safety objectives of a system have been met, with independence level defined during safety planning.

Functional safety audit

A review that determines whether the functional safety management procedures are actually being applied as planned, distinct from an assessment of whether safety objectives are met.

Safety plan

A controlled document defining the safety lifecycle activities, responsibilities, deliverables, and verification steps for a specific project, reviewed at phase transitions.

HAZOP guide words

Standard words such as no, more, less, as well as, part of, reverse, and other than, applied to process parameters at defined nodes to identify deviations.

Risk graph

An IEC 61508-5 method using consequence, frequency or exposure, avoidance probability, and demand rate parameters to determine the required SIL target.

Layer of protection analysis

A method that multiplies an initiating event frequency by independent protection layer probabilities, and compares the result with the tolerable frequency to derive SIL.

ALARP principle

Risk must be reduced until further reduction would cost grossly disproportionate to the benefit obtained, with residual risk documented and accepted.

Required risk reduction

The ratio of initial risk to tolerable risk; the credited safety function must reduce risk by at least this factor.

PFDavg SIL bands

IEC 61508-1 Table 2 low-demand bands: SIL 1 1e-2 to 1e-1, SIL 2 1e-3 to 1e-2, SIL 3 1e-4 to 1e-3, SIL 4 1e-5 to 1e-4.

High demand PFH bands

Per hour: SIL 1 1e-6 to 1e-5, SIL 2 1e-7 to 1e-6, SIL 3 1e-8 to 1e-7, SIL 4 1e-9 to 1e-8.

Risk reduction hierarchy

Order of preference: inherently safe design first, then engineered safeguards including safety functions, then information for use.

Safety requirements specification

A precise, unambiguous, testable document defining safety function behaviour, safe state, response time, SIL, demand mode, and traceability to hazards.

Process safety time

The interval within which a safety function must act to prevent a hazard; the specified response time must be shorter than this interval.

Safe state definition

A statement of the system condition on detected fault, power loss, and demand, including whether outputs trip or hold last value.

Functional safety concept

The set of safety functions and their SIL targets derived from hazard and risk analysis, preceding the technical safety concept.

Low demand mode

A mode where the demand rate is no more than once per year and no more than twice the proof test frequency, measured by PFDavg.

Systematic capability

A measure, graded SC 1 to SC 4, of a subsystem's ability to avoid systematic failures; it limits the maximum SIL claimable regardless of random failure rate.

Architectural constraints

IEC 61508-2 tables that limit the maximum SIL of a subsystem based on its hardware fault tolerance and safe failure fraction.

SIL allocation

The process of assigning the required SIL of a safety function to the subsystems and elements that implement it, preserving overall integrity.

Diagnostic coverage

The fraction of dangerous failures detected by automatic diagnostics; λDU equals λD multiplied by one minus diagnostic coverage.

Safe failure fraction

The ratio of safe failures plus detected dangerous failures to total failures, used in the architectural constraint tables.

Beta factor model

A common cause failure model where a fraction beta of the dangerous undetected failure rate affects all redundant channels simultaneously.

Hardware fault tolerance

The number of faults a subsystem can tolerate while still performing its safety function; N means N+1 failures are needed to lose the function.

Proof test coverage

The fraction of dangerous undetected failures that the proof test actually reveals, which must be justified rather than assumed.

Software safety lifecycle

The IEC 61508-3 phases from software safety requirements through architecture, unit design, coding, integration, verification, and validation.

Techniques and measures

IEC 61508-3 Annex A and B tables listing techniques rated highly recommended, recommended, or not recommended for each software SIL.

Pre-existing software

Software not developed under the safety lifecycle; it may be used only if suitability is assessed and it is verified for the target SIL.

Software safety validation

Testing and analysis demonstrating that the integrated software and system meet the safety requirements specification in the intended application.

Verification versus validation

Verification confirms each lifecycle output meets its input requirements; validation confirms the completed system meets the user's stated needs.

Fault reaction time

The time from fault detection to reaching the safe state; it must fit within the process safety time after allowing for sensor and actuator delays.

Proof test interval

The time between proof tests; it directly sets the achieved PFDavg and therefore the achieved SIL, so changing it changes the claim.

Bypass management

Controlled, time-limited, authorised and recorded overriding of a safety function, with compensating measures defined while the bypass is active.

IEC 61511 scope

The process industry sector standard for safety instrumented systems, applying the IEC 61508 framework with SIL 1 to 4 and a sector lifecycle.

Safety manual

Documentation supplied with a certified device stating the assumptions, constraints, and proof test requirements needed for correct use in a safety function.