Manipulation of Safe Guards: What can designers do?

Designing safety-related machinery means more than simply complying with regulations and other legal stipulations. Consulting the relevant regulations and standards, dismissively asking “Where does it say that?!” – to ensure that only those safety measures that are strictly necessary are implemented – is no substitute for deep consideration of solutions that are not only right for safety and right for people, but are also fit for purpose.

Most of all, designers must be more sensitive to operators' demands for operability of machines and safety devices and provide a serious response, because their demands are based on practical experience. This does not make the safety-related design more difficult, but is the basis on which to build user-friendly, safety-related machinery. It's essential that the actual development and design is preceded by a detailed, candid analysis of the operational requirements, the results of which are recorded in a binding requirement specification. If not the situation may arise in which the machine and its incorporated safety measures may not be accepted. What's more they could provoke users into creating "new ideas", which are mostly not in the spirit of health and safety. These in turn could conjure up a whole new set of hazards, which were far from the minds of the original designers.

Experience shows that the fi rst part of this challenge can be met at reasonable cost and with a sufficient level of success through systematic troubleshooting, using function structures and signal flow paths. As for the second part of the task, counteracting manipulation attempts, designers must rely on their tried and trusted methods, as with any other design task. After all, safety related design is hardly a dark art!

Nonetheless: Manipulation rarely occurs voluntarily; it usually indicates that machine and operating concepts are not at their optimum. Conduct contrary to safety should always be anticipated when:

• Work practices demand actions which do not have a direct, positive impact on outcomes
• Work practices enforce constant repetition of the same work steps, or fresh approaches are always required in order to achieve work targets
• Safeguards restrict the line of vision and room for maneuvering required to perform the activity
• Safeguards impede or even block the visual/auditory feedback required to work successfully
• Troubleshooting and fault removal are impossible when the safeguards are open

In other words: Manipulations must always be anticipated when restricted machine functions or unacceptable difficulties tempt, even force, the machine user to “improve” safety concepts. Manufacturers must design protective measures so that the functionality and user friendliness of the machine are guaranteed at a tolerable, acceptable level of residual risk: predict future manipulation attempts, use design measures to counteract them
and at the same time improve machine handling.

The obligations of machine manufacturers are threefold:

1. Anticipate reasons and incentives for manipulation, remove the temptation to defeat interlocks by creating well thought-out operating and safety concepts for machinery.
2. Make manipulation difficult by design, e. g. by installing safety switches in accessible areas, using hinged switches, attaching safety switches and their actuators with non-removable screws, etc.
3. Under the terms of the monitoring obligation specified in the Geräte- und Produktsicherheitsgesetz [German equipment and product safety law], systematically identify and rectify any deficiencies through rigorous product monitoring with all operators (reports from customer service engineers and spare part deliveries are sometimes very revealing in this respect!).

The client who places the order for a machine can also help to counteract manipulation by talking to the machine manufacturer and candidly listing the requirements in an implementation manual, binding to both parties, and by talking openly about the faults and deficiencies within the process, then documenting this information.