The importance of safety as one of the key assets is rarely questioned by anyone. We all want to be safe at home, at work, at hobbies, during transport, and in all other situations. We want to be able to trust the equipment that we are using and that using it will not cause harm to us, to the environment or to anyone else. When it is questioned whether anything can ever be regarded as being absolutely safe, safety is usually defined, also in legislative literature, as freedom from unacceptable risk. That is, freedom from an unacceptable combination of consequences and probability of an unwanted incident. What is acceptable, then again, may vary depending on the case and context.
For a long time, the need for safety has been a basic human need, and several kinds of approaches have been developed by humankind to serve that need. In many cases, unfortunately, the approaches have been thought of because of accidents, which still today serve the purpose of continuous improvement. One of the key lessons learned has been that in order to achieve safety, a combination of approaches is typically needed, so that ultimate safety is usually only achieved as a result of several approaches.
How functional safety affects the different areas of the design process?
From the beginning of a design process, we typically try to design equipment, processes and apparatus to be naturally safe by eliminating the hazards related to them. Depending on the context, this may mean, for example, changing hazardous substances in a process to harmless ones, eliminating moving parts, eliminating unstable reactions, reducing the amount of stored energy, and so on. When it is not possible to eliminate the source of the hazard, we can try isolating it so, for example, the rotating blades of a wood processing equipment are secured with a cover in order to protect an unlucky operator. When this is not possible, or when the remaining risk is still unacceptable, we may introduce instructions and protective equipment such as safety glasses, gloves and boots. We can develop systems to warn about the danger. And we can develop functional safety systems.
In short, functional safety is part of the overall safety that is dependent on the correct functionality of the system in question. That is, to ensure safety, something (the function) must be performed by a system. This kind of system implementing a safety function is what is generally called a safety system. Safety functions can be further classified to functions that must be performed continuously all the time (continuous mode functions) or when necessary (on-demand mode functions). An example of a continuous mode function could be to maintain cooling water circulation and an example of an on-demand-mode function is to trigger an emergency brake when detecting that an autonomous machine is about to collide with an obstacle.
Who should be interested in functional safety? The sequel of this blog will answer to that question better. Stay tuned.
Text: Timo Vepsäläinen