Contemporary Functional Safety Standards

Monday, May 9, 2011 @ 11:05 AM gHale


By Nicholas Sheble
Functional Safety (FS) is part of the overall safety of a system or piece of equipment that depends on the system or equipment operating correctly in response to inputs.

Functional Safety implies freedom from unacceptable risk of physical injury or of damage to the health of people either directly or indirectly either through damage to property or to the environment.

FS treats the function of a component or subsystem as part of the function of the whole system. Therefore, while Functional Safety standards focus on Electrical, Electronic and Programmable Systems (E/E/PS), in practice FS methods have to extend to the non-E/E/PS parts of the system that the E/E/PS actuates, controls or monitors.

Thus, FS includes the safe management of likely operator errors, hardware failures, and environmental changes.

Any claim of Functional Safety for a component, subsystem, or system should have independent certification and adhere to a recognized Functional Safety standard.

A certified product can then lay claim to be “functionally safe” to a particular Safety Integrity Level (SIL for IEC or EN standards) or a Performance Level (PL for ISO standards), or a class for UL standards, in a specific range of applications.

IEC is the International Electrotechnical Commission. EN is European Norm. ISO is the International Standards Organization.

The certification provides customers with a test report describing the scope and limits of performance.

The primary Functional Safety standards in current use are here:
EN 50128 – Railway Industry Specific
EN 50129 – Railway Industry Specific
EN 954 – Safety of machinery and safety-related parts of control systems

EUROCAE ED-12B European Airborne Flight Safety Systems

IEC 61496 – Evaluation of safety-related electro sensitive protective equipment
IEC 61508 – Functional safety of products, components, and systems: Evaluation covers electrical/electronic/ programmable electronic (E/E/PE) safety-related systems and assessment of the proper safety integrity levels (SILs) of your product or system
IEC 61511 – Safety for instrumented systems for the process industry sector
IEC 61511-1 – Functional safety – Safety instrumented systems for the process industry sector – Part 1: Framework, definitions, system, hardware and software requirements, based on EN 61508
IEC 61511-2 – Functional safety – Safety instrumented systems for the process industry sector – Part 2: Guidelines for the application of IEC 61511-1, based on EN 61508
IEC 61511-3 – Functional safety – Safety instrumented systems for the process industry sector – Part 3: Guidance for the determination of the required safety integrity levels, based on EN 61508
IEC 61513 – Nuclear power plants – Instrumentation and control for systems important to safety – General requirements for systems, based on EN 61508
IEC 61800-5-2 – Safety of adjustable speed electrical power drive systems
IEC 62061 – Safety of machinery, the functional safety of safety-related electrical, electronic, and programmable electronic control systems, based on EN 61508
IEC 62304 – Medical Device Software
IEC EN 61508 Parts 1 to 3 is a core Functional Safety standard, applied widely to all types of safety critical E/E/PS and to systems with a safety function incorporating E/E/PS.

ISO 10218 – Safety requirements for robots used in industrial environments
ISO 13849 – Safety of machinery and safety-related parts of control systems
NASA Safety Critical Guidelines
UK Defence Standard 00-56 Issue 2
UL 1998 – Assessment of software safety and evaluation of computer/software-controlled products
UL 991 – Assessment of controls that employ solid-state devices and are intended for specified safety related protective functions.
US RTCA DO-178B North American Avionics Software
US RTCA DO-254 North American Avionics Hardware

Links to other articles relating to Functional Safety:
New Life for Machine Safety Standard
UL Certifies Industrial Devices’ Safety
UL Functional Safety Mark Program

Nicholas Sheble (nsheble@isssource.com) is a writer, engineer, and technical editor based in Raleigh, NC.



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