Manipulation of safeguards

Dealing with safeguards and their manipulation is an issue in which the true causes have long been largely taboo. It's a situation that's diffi cult to understand, for without negative feedback, where can you start to make positive changes in the design of plant and machinery?
This situation has now changed: the confederation of commercial trade associations has published a study showing that safety equipment had been manipulated on almost 37 % of the metal processing machinery examined. In other words: in a good third of cases, manipulations have been detected and examined, although it's safe to assume that the unreported number may be somewhat higher.
One fact that hasn't changed, however, is the number of accidents recurring on machinery on which the safeguards are manipulated, as the BG bulletins regularly show. The report also reveals that in at least 50 % of all cases, the reasons for manipulation can be traced right back to the design
departments.
The legal position is clear: European and domestic law (e. g. EC Machinery Directive, EN standards, Geräte- und Produktsicherheitsgesetz [German equipment and product safety law]) mean that it is the responsibility of machine manufacturers only to place on the market products that have an adequate level of safety.  Manufacturers must establish all the potential hazards on all their machines in advance and assess the  associated risks. They are responsible for developing a safety concept for the respective products,  implementing that concept and providing the relevant documentation, based on the results of the hazard  analysis and risk assessment. Potential hazards must not be allowed to impact negatively on subsequent users, third parties or the environment. Any reasonably foreseeable misuse must also be included. Operating  instructions should also clearly defi ne the products' intended use and prohibit any known improper uses.
Design engineers must therefore make reasoned decisions regarding situations in which events may be above and beyond what you would normally expect. This is a subject which is generally familiar and is considered these days, as CE marking clearly shows. Or is it? Despite the formal declarations from manufacturers that they themselves have taken responsibility for complying with all the essential health and safety requirements, behavior-based accidents continue to occur on machinery. Although the plant or machinery complies with the formal specifications, the design still failed to meet needs or satisfy safety requirements.
Design engineers should never underestimate the technical intelligence and creativity of machine users, and how dubious practices for defeating safeguards can be revealed: It begins with crude but effective access to the mechanical structure of the signal fl ow chain and extends to skillfully filed keys for type 2 safety switches. It includes loosened, positive-locking shaft/hub connections on switch cams, which are difficult to detect, as
well as sophisticated short and cross circuits and disguised, carefully hidden but rapidly accessible override switches in N/C / N/O combinations, in the connection lead between the control system and the safety switch. This is only a small sample of the manipulations that are detected; it is by no means all.
Design engineers should also consider that machine workers generally have a fair level of technical understanding and manual dexterity and also have considerably more time to become annoyed at ill-conceived operating and safety concepts and consider effective “improvements” than the designers had in their  development and implementation. Quite often they will have been reliant purely on the normative specifications, without being aware of the realistic, practical requirements.
The task of working out potential manipulations in advance is therefore contradictory: Design engineers with little experience in this area are supposed to simulate the imagination and drive of the machine operators, who may frequently work under pressure but still have enough time and energy to work out alternative solutions. They are supposed to incorporate their expertise into their designs and, under today's usual time constraints, convert this into safety measures which are manipulation-proof. A task that's not always easy to resolve.
BGIA has developed a check list of manipulation incentives, which performs a valuable service in predicting potential manipulations. From the author's point of view, however, enormous progress would be made if designers in future would increasingly put themselves in the user's position and honestly and candidly ask themselves what they would do with the available operating and safety concept.