The shared responsibility of machine safety
Our feelings of personal safety are tied to our perceptions, prejudices, fears, and all kinds of emotional and psychological sensations. How, in such an environment, is a machine designer to apply the scientific and logical principles of engineering to design and build a safe machine?
There are many hazardous features of modern industrial equipment, and we can deal with them in many different ways. Design improvements or the use of specialized equipment can eliminate or mitigate these hazards; some can be minimized by training or education. In any case, we are always left with some danger and risk from a machine. The difference is now we understand the danger and are confident that we have done as much as possible to minimize it.
Even when we are at our most comfortable and relaxed, there is still some remote danger. While resting in our backyard hammock an earthquake could knock us to the ground, lightning could strike, or a meteor could fall from the sky. Still, we have considered the hazards and the possibility of harm and deemed the situation safe.
Safety is defined as the freedom from intolerable risk. This simple definition contains a number of complex ideas. One idea is that there may be other, useful, definitions of safety. What this implies is that, contrary to common belief, there is no such thing as absolute safety. While I may be at ease in my hammock, another person may be terrified by the possibility of disaster. Not everyone feels equally safe in the same environment.
What each person does is define a safe environment according to his own knowledge, perceptions, and prejudices. “Normative safety” is the name for the safety we create according to our own rules.
To understand the meaning of “intolerable,” it is easier to contrast the words “tolerable” and “acceptable.” If something is acceptable, everyone in every situation, without reservation, universally allows it. On the other hand, if something is tolerable, I bear it knowing the harmful side effects that could come with it. I choose to bear the possibility of harm in return for the benefit I derive from this activity. Statistically, it is far riskier to drive a car than to walk, but we choose to drive to many nearby destinations.
Risk is the possibility of a loss or harm. This definition suggests that we can measure the possibility, or probability, of an outcome; in this case, the outcome is a loss or harm. Risk is often mistakenly interchanged with uncertainty, which is very different, is not measureable, and is related to not knowing what the outcome will be.
Understanding that risk is a fundamental part of safety has given rise to a new term in safety engineering: functional safety. This is that part of safety concerned with components and equipment and whether they can perform their safety functions as required.
The rules of safety
Because the safety reality we create is based on the rules we ourselves provide, it is essential that those rules be based on a foundation of principles and logic that is as solid and rational as possible. These rules must be broad in scope, clear in principle, and universally applicable. Here we begin to build the foundation of our safety principles:
1. Machine safety is a shared responsibility.
Primary responsibility for machine safety rests with the user of that machine. This responsibility rests with the user because with the user is where the machine spends most of its life, where there is the most interaction between persons and machine, where there is the most experience and understanding of the machine operation.
Other people and organizations have specific knowledge related to their role as designer, builder, maintainer, seller, buyer, recycler, etc., and must be responsible enough to pass on their knowledge to the end user. Every person and organization, however involved, bears responsibility to provide a safe machine.
2. An effective regulatory framework is essential.
This regulatory framework encompasses established public safety laws and regulations, and methods for those involved to decide and agree on acceptable safety practices for the engineering, design, construction, and use of machinery. This framework also includes guides for acceptable training and education regarding machine safety.
We must agree on our own normative safety world and the rules we will abide by in that world. This world is formed in part by our personal beliefs, values, and prejudices, and they affect the engineering decisions we apply to a machine safety system. We translate our beliefs and values into practicable design and construction choices. Those choices reflect what we value.
Not everyone values the same things; not everyone will always agree that every machine is safe. Components of the machine can be selected and engineered to be as reliable as possible, ensuring that they will perform safety functions consistently throughout the working life of the machine. Beyond that, we each need to understand that complete safety is not possible and to tolerate the risks of operating machines.
Everyone involved in the creation of machine bears a responsibility for its safety. A thoughtful, rational framework of safe practice is essential so that we can make the safe machine we seek.
Steve Wright is a registered professional engineer and a Certified Safety Professional. As a specialist at C&E Sales, Inc., he provides advice, training, and specification to customers with machine safety applications. He can be reached by email at firstname.lastname@example.org.