How to Check if a Machine is Safe: A Comprehensive Guide

How to check if a machine is safe? This question is crucial for engineers and business owners involved in building or upgrading machinery. Ensuring that safety measures are not only well-designed but also effective in practice is paramount. This article provides a step-by-step guide on verifying the effectiveness of preventive and risk-reducing measures, which standards to apply, and how to maintain proper documentation and compliance with regulations. By following this guide, you will know what to focus on and which mistakes to avoid, ensuring your machine is truly safe.

Why is Verifying Risk Reduction Measures So Important?

Consequences of Inadequate Verification

Many serious workplace accidents stem not only from design flaws but also from neglect during the evaluation and verification of safety measures. Even if machine design is exemplary and initial steps like risk assessment are performed at a high level, insufficient or superficial testing of safety devices can allow potential hazards to go unnoticed. As a result, workers may face significant danger, and the company could incur severe penalties and reputational damage.

The Importance of Compliance with Legal Requirements and Harmonized Standards

Harmonized standards serve as a key reference point for assessing machine safety, outlining the minimum safety and quality requirements for safety systems. To receive a CE mark, machines must meet the requirements outlined in the machinery directive and other applicable directives, such as ATEX for equipment operating in explosive environments. Adhering to these standards not only enhances safety but also simplifies the certification process and minimizes legal risks.

Basic Steps for Verifying the Effectiveness of Risk Reduction Measures

Documentation Verification

The verification process begins with ensuring that all records in the design documentation and risk assessment protocols are consistent and complete. Documentation should include:

1. Results of previous risk assessments, including descriptions of hazards and risk reduction measures.
2. Descriptions of technical solutions applied, such as protective barriers, light curtains, and emergency stop switches.
3. Evidence of compliance with relevant standards and regulations, including test confirmations, certificates, and attestations.
4. Detailed descriptions of operational procedures and emergency protocols.

If there are gaps in the documentation, such as missing explanations of how a safety system should function in practice or absent test information, these must be addressed. It’s also crucial to ensure that the documentation aligns with actual technical solutions, as changes may occur during machine construction that are not always reflected in the original documentation.

Design Analysis in Terms of Harmonized Standards

Before testing the device in practice, it’s advisable to consult harmonized standards to verify that design assumptions and safety mechanisms meet their requirements. This includes checking:

• The type and effectiveness of guards, such as fixed guards, interlocking guards with control systems, and adjustable guards.
• The architecture of safety control systems, ensuring they meet the required performance level (PLr, SIL, etc.).
• The placement and ergonomics of protective elements, like emergency stop buttons and limit switches.
• Documentation regarding hazardous zones, including EX zones if applicable.

Expert support is often crucial at this stage, as specialists can help assess the design’s compatibility with the latest industry requirements and guidelines.

Testing in Real Conditions

The most reliable stage is testing the machine in its intended work environment to verify:

1. The effectiveness of guards and other safety components:
   • Do guards prevent access to dangerous areas during machine operation?
   • Do light curtains effectively detect human presence?
   • Do interlocking systems stop the machine within the required time?
2. The proper functioning of safety control systems:
   • Do position sensors, emergency stops, and other detection elements trigger the required responses?
   • Can the device resume normal operation only after the threat has been removed and appropriate restart conditions are met?
   • Is there logical consistency between automation modules and safety elements?
3. Adherence to ergonomics and employee procedures:
   • Do operators have safe access to control elements?
   • Is there a risk of unintentional machine activation?
   • Are start, emergency stop, and restart procedures adequately described, understandable, and practiced?

Depending on the results of real-world tests, modifications to the design may be necessary. Subsequent tests should verify whether the introduced corrections effectively eliminate identified issues.

Audits and Inspections by Independent Entities

In industrial practice, inviting an independent expert entity to assess safety is a common and recommended solution. An external machine audit can identify errors and non-compliances that engineers involved in the project may have overlooked. This perspective is invaluable for confirming that the protection system is designed and implemented to the highest standards.

Criteria for Evaluating the Effectiveness of Risk Reduction Measures

Level of Risk Reduction

The primary indicator of the effectiveness of safety measures is the level of risk reduction they provide. Both standards and the risk assessment process allow for determining an acceptable level (PLr or SIL). Verification should demonstrate that the installed protective measures achieve the required level. If not, more advanced safety technologies or additional organizational measures may be necessary.

Reliability and Maintenance Over Time

A safety system must not only be designed to activate in an emergency but also meet reliability requirements throughout its operational life. This necessitates regular inspections, maintenance, and periodic testing. Verification in this context involves checking whether a risk reduction measure can be maintained in the required state, such as frequent sensor calibration and checking the condition of wiring and contacts.

Readability and Intuitiveness for the Operator

The most advanced safety system can be ineffective if operators do not know how to use it or respond to signaled threats. Therefore, verification should also include:

• Training for personnel operating the device.
• Clear labeling of control and protective elements.
• Simple and understandable procedures, such as start/stop sequences and the ability to quickly disconnect the machine in case of failure.

Common Problems and Mistakes in the Verification Process

1. Too superficial evaluation of safety functionality, such as only visually checking whether guards are installed without dynamic tests or stopping time measurements.
2. Lack of integration of safety systems with the machine control system, resulting in theoretical operation of safety measures that can be bypassed or deactivated in practice.
3. Insufficient documentation confirming compliance with standards, such as missing test reports or protocols, hindering CE marking and formal declaration of conformity.
4. Failure to consider the work environment, as machines may function correctly in a lab but face more challenges in harsh production conditions, such as dust, vibrations, high temperatures, or ATEX zones.

The Importance of Modernization and Continuous Improvement

In today’s industrial sector, machines often undergo modernization, which can involve redesigning machines from scratch or adapting existing solutions to new production needs. Each modernization requires re-verification of risk reduction measures. Even minor modifications, like installing a new vision camera or changing a controller, necessitate verification to ensure:

• No new hazards arise from new functions.
• Existing safety measures remain sufficient and work correctly with new elements.
• No additional compliance tests with current standards are needed.

Only a positive result of such re-evaluation allows for continued operation or issuing updated documentation, such as a declaration of conformity.

Example Methods and Tools for Verification

Checklist

This basic yet effective tool helps systematize the review process. A well-constructed checklist allows for step-by-step evaluation of specific safety areas:

• Are all dangerous machine elements adequately shielded?
• Are emergency devices, like emergency stops and safety switches, easily accessible and labeled?
• Is the documentation complete, current, and consistent with the actual state?

HAZOP Analysis

This methodology, widely used in the process industry, can also be applied to machine assessment. HAZOP involves systematically reviewing each stage of the technological process and identifying potential deviations from design assumptions that could lead to hazardous situations. In machine safety verification, this helps reveal weaknesses in control systems or human-machine interactions.

FMEA (Failure Mode and Effects Analysis)

In the context of safety, FMEA focuses on identifying potential failure causes (failure modes), their effects, and assessing how severe, frequent, and detectable they are. FMEA-based verification allows tracing whether installed risk reduction measures effectively counteract the most dangerous failure scenarios.

Acceptance Tests: SAT and FAT

In large machine and production line projects, FAT (Factory Acceptance Test) and SAT (Site Acceptance Test) are used. FAT is conducted before shipping the finished machine from the manufacturer’s facility, while SAT occurs at the destination after integration with the production system. Safety verification is a crucial part of these tests, confirming whether the device meets contractually agreed requirements and safety standards.

Documenting Verification Results

After completing the verification process, meticulously documenting its results is essential. A standard report should include:

1. Description of the methodology and scope of verification, such as which tests and analyses were conducted and the criteria used for evaluation.
2. Results with photographs and measurements, such as whether emergency stop times fall within standard limits and sensor tolerances.
3. Conclusions and recommendations, indicating whether safety measures are adequate or require changes, and which have priority.
4. Signatures of responsible individuals, including those who conducted and supervised the verification.

This report is invaluable for external audits or potential accident investigations.

Safety Verification, CE Marking, and Declaration of Conformity

For a device to be marketed in the European Union, it must bear the CE mark and have a declaration of conformity. Issuing this declaration requires meeting essential requirements outlined in regulations, primarily the machinery directive and the new EU Machinery Regulation, and confirming through documentation and tests that risk has been reduced to an acceptable level.

Verifying the effectiveness of risk reduction measures is an integral part of the certification and conformity assessment process. Without thorough verification, serious doubts may arise about the correct marking of the device, potentially leading to the withdrawal of the declaration of conformity and the need to remove the product from the market.

Conducting a thorough verification not only protects the health and lives of employees but also builds the image of a reliable manufacturer and avoids legal consequences. In an era of rapidly changing regulations and technological advancements, staying updated with industry developments and utilizing expert support is crucial.

FAQ: How to Check if a Machine is Safe