Safety manipulation: Why and How? Or practical tips and tricks

Safety requirements are mandatory for machine producers and end-users. Ignoring these obligations can lead to consequences for various parties, including plant operators and managers. For instance, after a fatal safety accident due to a removed light barrier, the maintenance and production managers were sentenced to prison, as they had tolerated the manipulation [1, 2].

Nowadays, the manipulation of safety systems is still one of the main reasons behind accidents related to machinery safety (Figure 1). According to the German Federation of Institutions for Statutory Accident Insurance and Prevention (HVBG), about 37% of safety devices are either constantly or temporarily manipulated, contributing to up to 20% of total accidents [3].

As specified by HVBG study, the main reasons behind the manipulation of safety devices are primarily related to time and production factors (Figure 2). More specifically, about 65% of the reasons were connected to time saving/optimization, and 21% were related to performance/production motives. However, only half of the operators considered safety manipulations as leading to higher accident risks.

These days, there are six essential recommendations for addressing the manipulation of machinery safety. In general, these recommendations follow the risk reduction principles described in ISO 12100, which include safe design, safety measures, and organizational means (Figure 3).

Firstly, to prevent "manipulation accidents," it is necessary to consider an efficient and user-friendly machine design with a proper safety concept. In other words, it is essential to have a comprehensive operating and safety concept that anticipates the needs of the operator. This can be achieved through a collaborative effort between machine engineers and safety equipment producers. Such cooperation may eliminate the need for retrofitting safety functions after the machine is already developed. There are five additional practices and recommendations to follow, beyond this basic principle:

• Risk Analysis and Safety Concept: As you may already guess, risk assessment and hazard identification, considering all operating modes and tasks, are vital for machinery safety. The results of the risk study should contribute to a safe machine design and coherent operating concept in the earliest stages of the machine lifecycle.
• Safety Regulations and Standards: It is essential to ensure that machinery complies with relevant safety requirements. For instance, standards such as ISO 14119 provide practical advice and emphasize the importance of designing products so that bypassing safety devices effortlessly is not possible.
• Safety Measures: Implementing safety measures, such as coded safety switches, can help prevent manipulation (Figure 5). Additionally, safety technologies like smart camera systems, including AI-based systems that differentiate between operators and workpieces, may also prevent manipulation. It is important to note that, in view of best practices and standard requirements, safety equipment should not be easily removed by unauthorized personnel. According to the HVBG report, a significant portion of manipulations were made without the use of special tools. Therefore, the utilization of one-way screws, gluing, or welding can prevent the unauthorized dismantling of safety equipment.

• Collaborative Approach: Involving machine operators and safety experts in the procurement process of machinery can be beneficial. Their participation in planning and acquiring technical equipment, as well as conducting thorough checks before commissioning the machine for production, helps identify and address potential vulnerabilities to tampering.
• Employee Training: Comprehensive safety training on the risks and consequences of manipulation, along with the importance of safety measures, can raise awareness and promote a safety culture in the working environment. Nowadays, manufacturing companies regularly highlight manipulation topics during internal training sessions for employees. These sessions include specific examples of manipulation, emphasize the associated risks and consequences, and outline the responsibility of supervisors to ensure a manipulation-free working environment [3].

In conclusion, the issue of manipulation cannot be resolved instantly and requires a long-term approach. To minimize the incentive to manipulate a protective device, it is crucial to assess whether the existing protective concept of the machine imposes unnecessary restrictions during operation. Furthermore, it is essential to ensure that discussions about the sensitive topic of manipulation are open between safety equipment producers, designers, and end-users of machinery. A better link between all parties is key to developing safety concepts that do not impose restrictions and reduce the need for manipulation.

References:

[1] Osnabrücker Zeitung: Strafprozess um den t?dlichen Arbeitsunfall eines Lehrlings an einer Glasschleifmaschine, 2013

[2] NDR Fernsehen, Tod eines Lehrlings: Gewinn vor Sicherheit? Panorama 3, 2013

[3] HVBG, Manipulation von Schutzeinrichtungen an Maschinen, Report, 2006

[4] DGUV, FBHM-022: Manipulation von Schutzeinrichtungen Verhindern, Erschweren, Erkennen, 2021

[5] Application manual for PSR safety relays, Phoenix Contact, 2012