Safety Insights

Introduction to Functional Safety

HIMA Paul Hildebrandt GmbH — Fri, 18 Sep 2026 14:33:46 GMT

Today’s industrialized cities are convenient and safe to live in because of advanced appliances, machinery, and systems. Millions of citizens can co-exist comfortably in a technologically-enabled world that has been simplified by equipment and devices, both large and small. Whether the task involves preparing breakfast, travelling through busy cities, or occupying buildings, it can be easy to take for granted the role of modern technology in making our lives safer.

How to Achieve Safety: Risk Analysis

HIMA Paul Hildebrandt GmbH — Fri, 18 Sep 2026 14:33:28 GMT

Though you may not be aware of it, Functional Safety is all around us, every day and just about everywhere we go. In technical terms, we can define Functional Safety as protecting people, the environment, and equipment from design and implemented systems. In more simple terms Functional Safety seeks to reduce risks, injury, and damage that could be caused by hardware, software, and systems by implementing protective functions.

Think about the coffee maker you use every morning. A protection function monitors the temperature of the coffee and the volume of coffee in the pot. When either exceeds acceptable levels, a sensor will alert the machine and a safety function will turn off the heater or stop the machine from making any more coffee.

The objective of Functional Safety is to identify potential hazards, analyze associated risks, and implement measures to mitigate or reduce those risks. To properly reduce those risks, Functional Safety experts must thoroughly analyze risk as risk identification, analysis, and reduction are key steps in risk management. This article will explore the process of analyzing risk which is crucial to achieving Functional Safety.

By the end of this article, you will be able to:

Grasp the role of risk assessment and be able to situate risks within the safety lifecycle
Understand how a hazard can develop into damage, understand, and correctly use the basic terms associated with risk analysis
Know how to read and understand a hazard and risk analysis, such as the HAZOP study
Provide real life examples of risk analysis.

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Dependable Systems: Errors, Faults and Failures

HIMA Paul Hildebrandt GmbH — Fri, 18 Sep 2026 14:33:15 GMT

Dependability is a measure of system properties such as availability, reliability, maintainability, safety, and in some cases other characteristics such as security. In short, dependability describes a set of fundamental system properties that deals with the ability of the system to deliver a service under specified conditions within a given time that can justifiably be trusted. A systematic approach to analyzing the concepts of dependability relies on three significant aspects: the attributes of, the threats to, and the means by which dependability is achieved or enhanced as shown in Figure 1.

Figure 1: Dependability based on IEC 6005
Source: HIMA Paul Hildebrandt GmbH

In this context, a system may lose its intended functionality because it fails to fulfill a given specification due to a threat. Threats may be caused by poor development, non-sufficient specifications, or a poor manufacturing process that can lead to a loss of function. Depending on their time of occurrence and effects on the system, threats are usually categorized in a wide variety of definitions and terms.

Figure 2: Threats to a systems in the context of dependability
Source: HIMA Paul Hildebrandt GmbH

Failures, faults, and errors are the most commonly used terms and will be the focus of this paper. Although we do not focus directly on other terms, it is important to mention further terms such as defects, mistakes, bugs, malfunctions, and upsets which are either used as synonyms or as explanatory terms in some literature references.

Against this background, this module gives the main definitions relating to the threat’s terminology, shows a generic concept including definitions in accordance with safety standards, and highlights a simple interpretation as well as examples. Furthermore, the module presents an overview of the various classifications of threats.

Note: Since the standards of Functional Safety usually group safety solutions in systems, subsystems, elements, and components, it is important to note that in the following the term “system” is used as a general term for reasons of simplicity. The presented concepts can certainly be applied to other parts of a system.

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Structures of Safety Systems

HIMA Paul Hildebrandt GmbH — Fri, 18 Sep 2026 14:33:07 GMT

In Functional Safety, safety instrumented functions (SIF) implemented in safety instrumented systems (SIS) must ensure a certain level of risk reduction. The measure of the performance required from these SIFs is referred to as safety integrity level (SIL) (see Figure 1). The IEC 61508 standard defines four SILs, with SIL 1 being the least and SIL 4 the most dependable. Which SIL should be applied depends on a combination of various quantitative and qualitative factors, including risk assessments and safety lifecycle management. However, other standards may have different SIL definitions. In such standards, we can find tables with a SIL quantification based on the probability of failure of a given SIF.

In this context, several members of the Functional Safety community, especially beginners in this area, believe that the SIL of a SIF is mainly determined by a quantitative analysis that is largely reduced to the calculation of the probability of failure. However, this is definitively a false assumption. For instance, the IEC 61508 standard introduces a set of requirements that employ both qualitative and quantitative constraints in order to determine the safety integrity level of a SIF. These requirements can be categorized into three main constraint types: systematic capability constraints, architectural constraints, and probabilistic performance metric constraints (see Figure 2).These constraints can be expressed by three essential safety parameters: the safe failure fraction (SFF), the hardware fault tolerance (HFT) and the probability of failure on demand (PFD). Here, the individual parts of a SIF, e.g. sensors, the logic solver and final elements that work together to implement the individual safety loops, must comply with these constraints of the required SIL. This means that all components within that loop must meet an SFF, HFT and PFD requirement for the intended SIL.

In this module, we focus on the architectural constraints that define the structures of safety systems and highlight the various system architectures used to enhance the dependability of these systems. However, due to the complexity of the topic and the dependence with other constraints, we first introduce a set of definitions of essential terms in this context. Afterwards, we briefly describe the general structure of a SIS and a SIF, finishing with an overview of the most essential safety architectures.

Figure 1: SIS, SIF and SIL
Source: HIMA Paul Hildebrandt GmbH

Figure 2: Safety constraints classification
Source: HIMA Paul Hildebrandt GmbH

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Standards and Functional Safety

HIMA Paul Hildebrandt GmbH — Fri, 18 Sep 2026 14:33:05 GMT

For societies to be safe, systems known as safety frameworks are essential. These safety frameworks normally include safety standards and regulations that combine to make the places in which we live and work safer.

In such a vast area as safety, it is important that all the role players involved in manufacturing and deploying products and equipment understand how to act as one. In this chapter, we will focus on standards as one of the most important aspects of ensuring the continued safety of equipment and systems around us.

As described in Figure 1 below, the success of safety initiatives can be measured according to outcomes such as the number of incidences of injury or death. Having standards that everyone adheres to plays a major role in this.

When societies successfully implement safety mechanisms that impact the behaviors of ordinary people, these safety frameworks have a positive effect on safety results.

Fig 1. Systems of safety based on IEC white paper: Safety in the future, 2020
Source: HIMA Paul Hildebrandt GmbH

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Overview of Functional Safety

HIMA Paul Hildebrandt GmbH — Fri, 18 Sep 2026 14:32:56 GMT

Is the term Functional Safety new to you? Chances are that you are aware of ways that Functional Safety is present in your life – you probably just did not know until now that there is an entire industry dedicated to streamlining safety into equipment and devices we often use.