Functional Safety and Reliability is a hot topic that stimulates many discussions, depending on the person’s business and previous experiences. Some see it as complying with the functional safety checklist in their industry, and some see it as costing the risks. For some, it‘s a critical success factor for their brand image and competitiveness in the market.
What is Functional Safety?
According to the Oxford dictionary, safety is the condition of being protected from or unlikely to cause danger, risk, or injury. When discussing products and their development, safety is often defined as the ability of the product to be safe for its intended use. This type of safety is called Technical Safety, also known as Safety of the Intended Function (SOTIF), and is relatively easy to define because it’s passive and designed into the product. It ensures that machines and systems operate in a safe way when they work as designed.
“Functional safety focuses on electronics and related software and activates built-in safety mechanisms to reduce potential risks that could harm somebody or destroy something to a tolerable level.” – IEC
Functional Safety is a little more complicated; it’s active, like an independent control system to ensure safe operation. Safety is achieved by ‘actively’ doing something or stopping something from happening.
Functional Safety – some real-life examples
A simple example of a functional safety system is a domestic coffee maker with a sensor that detects the coffee temperature or the volume of coffee in the flask. If the sensor detects the temperature has exceeded a threshold, it switches the heating element off. Think about the negative business impact on the leading domestic appliance brand if this didn’t work!
Another example of Functional Safety is a forest machine equipped with a safety radar. Should the radar notice any movement around the vehicle, it will halt the movement of the harvester head. The normal environmental conditions of a forest machine can be anything from beautiful sunny weather to a stormy night. When operating in difficult wet snow conditions, the radar sensors can get dirty. Should this happen, the control electronics will notice the unreliable radar signal, and the vehicle will notify the operator for reliability before the safety risk. Think about the responsibility of the control electronics manufacturer!
Components of a safety-related system
The components of a safety-related system are quite basic. They are typically comprised of 3 elements
Sensors – to detect the state of something, e.g. what’s the temperature of the coffee in the coffee maker?
Logic Solver – a programable electronic device to decide what to do, e.g. if there is movement around the vehicle, then warn the operator.
Actuators – to do something, e.g. to isolate the power to the flask’s element or warn the forest machine’s operator about the current reliability and the potential safety risk.
Functional safety doesn’t mean no failures. The standards define a maximum allowable rate of unsafe failures to achieve As Low as Reasonably Practicable (ALARP). As the UK Health and Safety Executive (HSE) states “…making sure a risk has been reduced ALARP is about weighing the risk against the sacrifice needed to further reduce it.”
A common definition of Reliability is the probability that the product will perform its intended function when operating under normal environmental conditions for a specific period of time.
Whilst Reliability Analysis is a well-established branch of engineering, and even though most of the methods and techniques used are very straightforward, it is until recently an under-utilized technology. This is now changing with new proposed legislation such as the Regulation on Ecodesign for Sustainable Products. This encourages more focus on product durability, reliability, reusability, upgradability, repairability and ease of maintenance. The role of reliability in product development and equipment operation can only increase. This highlights the close relationship between Reliability and Sustainability prevalent in today’s society.
Let’s consider our two examples – the coffee maker and the forest machine. Two different products with very different markets – one high volume and one low volume and Reliability Analysis will be used differently for each product. The role of design Failure Mode and Effects Analysis (FMEA) is critical for understanding how to mitigate potential product failure during the product concept and design phases, and process FMEAs for limiting the introduction of product failures during the manufacturing phase. Effective FMEAs will go a long way to a successful product.
With the best will in the world, sometimes unexpected failures happen. Successful companies handle this by demonstrating to their customers that they are in control of the situation and have the tools and processes in place to resolve the problem. Tools such as FRACAS (Failure Reporting and Corrective Action System) can play a significant role in this.
For the coffee maker machine manufacturer, better reliability analysis during the product development phase can provide the manufacturer more confidence to offer better warranty periods – 5 years rather than 1? An interesting feature of Reliability performance often observed is that the more features present in machines (and thereby more components) the poorer the reliability performance can be – so perhaps less is more?
For the forest machine manufacturer effective reliability, availability and maintainability analysis can help define the best strategy for maintenance, spare part and logistics management – particularly for equipment operating in very remote locations – providing the machine operator the confidence that any downtime is minimal.
Support Management using Simulation
Companies add the cost of risk to the equation: fire, injury, death, brand, supplier reputation. CAE and simulation provide methods to look what’s behind what we see. Simulation models along with empirical data from prototype testing and field environment can us help design products that are safer for the customer and better for our business. A simulation model that is adjusted to empirical data is the digital twin of our product. The digital twin will help us understand the root cause of a failure, optimize your product design, and mitigate the risk of an unsafe failure.
Take control of Functional Safety and Reliability
Whatever business and industry you´re in, however you define Functional Safety and Reliability, it is undisputedly important to define the risks, manage the processes and tools, and maintain the safety of your products.