Why functional safety is important

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When it comes to process control, safety standards continue to evolve as the industry continues to learn and improve. Standards and safety instrumented systems for functional safety are critical when it comes to continuous operations and saving lives.

Managing operational risk is one of the most demanding aspects of achieving safe, reliable, and profitable operations for any company working in high-hazard industries. Getting safety wrong in high hazard industries is not an option because incidents:

• Cost money
• Disrupt reliable operations
• Impact the environment
• Can result in massive damage
• May cause loss of life
• Threaten an organizations reputation and very existence.

And yet, a worrying trend is happening. Safety incidents are rising despite a decrease in the total number of working hours.

To keep high hazard operations safe for an entire lifetime, operators rely heavily on functional safety management and practices to ensure compliance to regulatory standards, meet legal requirements, protect the environment, protect people, and protect their capital assets.

Fundamentals of functional safety

Functional safety is fundamental to enabling the safe, reliable, and compliant operations of today’s process plants. A key component is the complex technology used for safety related automation systems. But, more importantly, is the implementation of a safety life-cycle approach that captures all assets of plant design, operations, and maintenance of those plants.

Functional safety is a very complex subject. But there are a few key various practices, standards, concepts, and implementation considerations involved with functional safety management that could help your business.

Why are safety standards important?

Standards and guidelines about evaluation and certification of control instrumentation used in safety instrumented systems, or SIS, were first introduced in 1984.

A key milestone was reached in 1996 when the International Society of Automation introduced a standard that documented the steps necessary to properly specify, design, and maintain a safety system.

• IEC 61508 – an umbrella standard that covers the functional safety of electrical, electronic, and programmable electronic systems across all industry sectors.
• IEC 61511 – a sector-specific standard for functional safety implementation, developed specifically to address functional safety in the process industry.

Both the IEC 61508 and IEC 61511 are continuing to evolve and adapt to industry needs based on practical experience gained from global implementation.

It is important to note, that these standards are not prescriptive, but performance based.  They present guidelines for best practices, but they do not identify procedures for specific implementation.

The need for functional safety

Why were these standards created? Why was the concept of functional safety developed?

Following the Piper Alpha disaster in 1988, the health and safety executive in the UK analyzed industrial incidents that caused injury or death to employees. The survey revealed that most of all safety problems were caused by human error.

Failures that were caused by design and implementations of SIS accounted for only 15% of all failures analyzed. The major source of failures was due to inadequacies in the specification of the control system (44%).

In total, 85% of all failures had nothing to do with automation and control. They had to do with the specification, installation, and operation of the equipment. They were caused by how the equipment was used, not by the equipment itself.

This realization led to the concept of the functional safety lifecycle, where safety is considered from project conception to plant decommissioning.

Managing the SIS lifecycle

The general approach to functional safety specifies 16 distinct parts for all activities required to manage safety throughout the entire SIS lifecycle. They can be broken down into three phases:

Analysis Phase – Risks are identified and analyzed, asking:

• What can go wrong?
• What is the likelihood?
• What is the consequence?
• What do I need to do manage and reduce the risk to an acceptable level?  (safety needs, target levels, specify safety requirements etc.)

Realization Phase – This encompasses risk reduction system (e.g., the safety instrumented systems) including the system design, build, test, documentation, installation, commissioning, and site testing.

Operation Phase – Businesses operate and maintain the systems and safety performance through the life of the plant, and make sure that all the assumptions used as the basis for design used in the analysis phase are validated and maintained.

Implementing a trustworthy SIS

A SIS is the last line of defense before a hazard occurs. It is a layer of protection designed to achieve or maintain a safe state of the process when unacceptable process conditions are detected.

A SIS is different from the basic process control system that controls the plant and needs to be treated differently. Above all, a SIS looks at the integrity of a safety loop from pipe to pipe. It has three major elements:

1. Sensors, which look for the initiating event that could cause the hazard
2. Logic solvers, which decide how to deal with the hazard and send a signal
3. Final elements, which, when signalled, bring the process to a safe state

Each of these elements and how they relate needs to be considered when assessing the risk. A SIS may implement one or more safety instrumented functions (SIF), which are designed and implemented to address a specific process hazard or hazardous events.

EcoStruxure Triconex Safety Instrumented System is certified by TÜV Rheinland to safety integrity level 3 and can be used in all safety and critical control applications. Risk is a product of likelihood and consequence. A trustworthy SIS is designed to reduce the likelihood of an incident or event, if does not reduce the consequence.

Learn how EcoStruxure Triconex Safety Instrumented Systems can bring higher safety and efficiency to your process control operations.