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IEC 61508 – the real story

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PLANT managers take on the enormous responsibility to provide a safe working environment for their personnel, maintain their equipment to ensure optimal productivity and efficiency, and implement the right systems to prevent hazardous events, or minimise the impact should one occur.

In addition to the potential hazards to personnel, the process and even the surrounding environment, a single plant shutdown can be financially devastating. Repair costs, equipment replacements, and lost time and production are only a few of the exorbitant expenses that may be incurred just to get the plant back up and running again.

With this in mind, plant managers seek solutions that can provide the high-level functions they desire, without jeopardising the high level of safety they require.

The International Electrotechnical Committee (IEC) responded to the safety concerns of plant managers and those seeking a way to demonstrate “good recognised practice” in the design, implementation and operation of their safety-related systems to their stakeholders and health and safety regulators. Based in Geneva, Switzerland, the IEC prepares and publishes international standards for all electrical, electronic and related technologies. The organisation has served as a basis for national standardisation, and as a reference when drafting international tenders and contracts.

The IEC initiated two formal studies on the functional safety of electronic systems.

The first study addressed the hardware issues, while the second focused on software.

Draft standard IEC 1508 emerged in 1995, after the two studies were combined, and provided a risk-based approach to identifying safety requirements in a system. Industry feedback was incorporated into further revisions until the IEC formally released international standard IEC 61508 in 2002.

Formally titled “Functional Safety of Electrical/Electronic/Programmable Electronic Safety-Related Systems”, IEC 61508 is a process-based standard and applies to the entire life cycle of the product.

The manufacturing company, as well as all of their processes and resources used to develop and manufacture the product, is managed for the goal of optimal safety. From its earliest concept and design stages, through its manufacturing, application, maintenance and ultimately its final decommissioning, all phases of the safety product must be compliant.

IEC 61508 can be applied directly to any process that uses electrical, electronic or programmable electronic products and systems for safety.

The intent of the standard’s authors was for the standard to be used alone or as a model to develop further industry or product-specific standards. For example, IEC 61511 was developed for the designers, integrators and end users in the process sector - and IEC 61513 for the nuclear arena.

Worldwide growth

MANY nations have affirmed their commitment to safety standard IEC 61508.

Significant evidence can be seen throughout nations such as the United States and Europe, where companies are confidently undergoing the arduous process of certification while furthering their knowledge and application of the standard.

Australia too is applying the standard in the process sector with the adoption of AS61508 (the Australian version of IEC 61508).


THOUGH the standard continues to build positive momentum in the industry, some manufacturers are exploiting the standard’s popularity by making misleading claims.

Manufacturers’ websites and product literature boast such claims as “IEC 61508-Compliant Products,” “Meets IEC 61508 Requirements” and “Approved to IEC 61508”. Such ambiguous statements have fuelled a great deal of confusion for end users, who need to truly understand what the consequences are.

IEC 61508 does not just focus on the product but, more importantly, the process under which the product was developed. Therefore, a company cannot legitimately develop an IEC 61508 compliant product without the company’s development processes first being evaluated and compliant to the standard.

Testing misconceptions

THE idea of “process based” and its importance can further be demonstrated with the concept of testing.

Most electrical and electronic devices are subjected to a series of tests to confirm that the units have been properly built to function and withstand the demands of the application in which they will reside.

Manufacturers produce “faultless” specifications of their products that offer assurance for optimal performance in a safety application.

Testing is of course essential; however, when it comes to the safety of the plant, and life and limb are at stake, why do we rely solely on the final testing data? It is not feasible to test for every possible failure mode of a system used to perform safety functions simply by testing the finished product.

In addition, when reviewing manufacturers’ test data, the misconception is that the manufacturer repeatedly produces exact duplicates of the actual product that has undergone the testing.

Testing is an important facet of IEC 61508, but the standard extends further than conventional product evaluations because it ensures that all of the processes in a product’s lifecycle (conception, design, manufacturing, installation, etc.) are compliant to the standard, not just a specific unit sent to a testing facility.

Get the facts

ONLY a certificate and a supporting “restrictions in use” report issued by an internationally accredited certification body is authoritative evidence of compliance to IEC 61508.

A savvy end user recognises the significance of certification and should not only ask a manufacturer if the safety instrumented system is certified to IEC 61508, but should carefully review the manufacturer’s approval report that verifies certification and details of exactly how the safety instrumented system is to be used.

Many companies are stepping up to the challenge and joining forces in an effort to better understand and apply the standard.

So whether manufacturers act voluntarily to implement IEC 61508, are enticed by incentives offered by insurance companies, or forced by government regulation in the future, random failures, incorrect system data and basic human error will ultimately force the standard into common practice on specifications and quotes for safety related equipment.

* Commentary by Kristina Balobeck, Moore Industries-International .

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