Risk Assessment – Methods and Tools for Machine Safety

Risk Assessment – Methods and Tools: Machine safety stands as a cornerstone of modern manufacturing. While regulations mandate risk assessments, this process is crucial for safeguarding employee health and optimizing technological processes. Proper risk assessment prevents accidents, minimizes downtime, and supports a positive corporate image. This article thoroughly explores:

• Why risk assessment is essential.
• Relevant standards to consider.
• The step-by-step process.
• Available methods, including risk scoring, risk matrices, FMEA, and more.
• Connecting risk assessment results with machine documentation and employee training.

We will also present practical examples and common mistakes encountered by engineers and safety specialists, all within the framework of standards such as ISO 12100, ISO 13849-1, ISO 13850, and ISO 62061.

Risk Assessment: Why is it So Important?

Some engineers view risk assessment merely as a legal obligation under the Machinery Directive 2006/42/EC or the Machinery Regulation 2023/1230/EU. However, a properly conducted assessment offers tangible benefits:

1. Reduction of Accidents: Identifying hazards and implementing appropriate measures reduces the risk of injuries or occupational diseases.
2. Compliance with Regulations: These actions meet legal requirements, protecting the company from administrative penalties and civil liabilities.
3. Improved Efficiency and Quality: Process stability and the absence of emergency downtimes positively impact productivity and employee satisfaction.
4. Building a Safety Culture: Awareness of hazards encourages employees to adhere to procedures and preventive actions.

Remember, risk assessment is not a one-time task. Any machine modification, process change, or new technology introduction can create new hazards. Therefore, systematic and continuous documentation updates, audits, and training become crucial.

Legal Foundations and Standards

In the European legal area, the Machinery Regulation 2023/1230 is paramount. It requires manufacturers (or their authorized representatives) to conduct a risk assessment, implement safety measures, and document these actions. In Poland, the Directive’s provisions were transposed into national law through relevant regulations. Regulation 2023/1230 is an EU Council regulation, thus applied immediately across the EU.

The key standard describing the general principles of designing safe machines is ISO 12100. It explains the process of identifying, analyzing, and assessing risks, introduces common terminology, and indicates the hierarchy of risk reduction measures. Complementary standards include:

• ISO 13849-1 – concerning safety-related control systems.
• ISO 62061 – regarding electrical/electronic control systems of machines.
• ISO 13850 – related to emergency stops and emergency stop devices.

Familiarity with these standards is essential as they complement each other and provide coherent guidelines for machine design, operation, and modernization.

Risk Assessment: Steps of Risk Evaluation

1. Hazard Identification

The first and most crucial step in risk assessment is meticulously identifying all potential hotspots or sources of hazards. Common hazards include:

• Mechanical Hazards: moving machine parts, rotating shafts, pulleys, rotating elements, conveyor belts.
• Thermal Hazards: heated elements, furnaces, combustion zones.
• Electrical Hazards: wires, control cabinets, static electricity.
• Chemical Hazards: contact with harmful substances, vapors, leaks.
• Radiation Hazards: lasers, UV, X-rays used for quality control.
• Ergonomic Hazards: improper posture, repetitive movements, excessive physical exertion.

Analyze all phases of use: normal operation, startup, maintenance, cleaning, retooling, and even disposal. Consult both designers and operators who know the machine “inside out.”

Example: In a plastics forming plant, the safety team noticed that employees frequently handle hot semi-finished products (around 180–200°C). There was a risk of hand and forearm burns. Previous analysis did not include this phase, as it focused mainly on the mechanical risk of the injection molding machine. Adding this hazard to the list prompted the company to introduce additional thermal shields and protective gloves with appropriate parameters.

2. Hazard Analysis

At this stage, we break down each identified factor:

• What could cause its occurrence?
• How might it happen in practice?
• What are the consequences of an adverse event (from minor cuts to loss of life)?
• Can the operator avoid or mitigate this hazard?

Rely on existing accident statistics, inspection reports, or machine service information. When introducing a prototype, draw knowledge from experiences with similar solutions.

Example: In the food packaging process, operators used knives to cut foil. No one paid attention to frequent minor cuts. Closer analysis revealed a “rush” culture, and knives lacked safeguards. Consideration was given to purchasing knives with retractable blades and training operators in safe cutting techniques, significantly reducing accidents.

3. Risk Assessment

Risk assessment involves assigning a “weight” to each hazard based on factors like likelihood and consequences. Commonly used methods include:

a) Risk Matrix

Create a table where columns define consequence categories (e.g., minor injury, hospitalization, permanent disability, death) and rows define likelihood categories (e.g., negligible, low, moderate, high, very high). The intersection indicates the risk level (e.g., low, medium, high, unacceptable).

Advantages: simple and visually clear, useful in discussions with management.
Disadvantages: subjective category selection, sometimes too general.

b) Risk Scoring

The point method extends the matrix. Instead of verbal categories, assign points to each category. This yields a more precise result called the risk score. Example formula: Risk Score=P×S×E

where:

• P (Probability) – likelihood of hazard occurrence (e.g., scale 1–5).
• S (Severity) – severity of consequences (e.g., scale 1–5).
• E (Exposure) – frequency or duration of exposure (also scale 1–5).

Sometimes other factors like Avoidance or Detection replace E. The total score (e.g., 1 to 125) provides a numerical risk measure. Companies set value ranges (e.g., 1–20 = low risk, 21–60 = medium, >60 = high), aiding safety investment decisions.

Advantages:

• More precise than a simple risk matrix.
• Clear, point-based rules reduce subjectivity.
• Useful for comparing different hazards.

Disadvantages:

• Requires a clear point scale and consistent application across the organization.
• Some subjectivity remains (probability or exposure assessment may vary among experts).

c) Risk Graph

Commonly used in designing control systems compliant with ISO 13849-1. It relies on a logical diagram assessing:

1. Severity (S).
2. Frequency (F).
3. Possibility to avoid (P).
4. Probability (W).

This evaluation yields the required Category and Performance Level (PL) or SIL (Safety Integrity Level) in the context of EN 62061.

4. Risk Acceptability Evaluation

After determining the risk level (in a matrix, points, or categories PL/SIL), compare it with the company’s acceptability criteria. Each organization may have different criteria. For example, some plants consider any situation that could result in death or permanent disability as unacceptable, regardless of probability. Others allow certain risks (e.g., minimal during maintenance) if specific protective measures are implemented.

Example: In a printing company, a Risk Score above 50 is deemed unacceptable, requiring immediate corrective action. Lesser risks in the 30–50 range are “conditionally tolerated,” meaning reduction plans must be made within a reasonable timeframe, such as by the end of the quarter.

5. Selecting and Implementing Risk Reduction Measures

After identifying and assessing risks, it’s time for practical actions. According to ISO 12100, the hierarchy is:

1. Inherently Safe Design – eliminate hazards at the source, e.g., remove protruding elements, reduce moving part speed, use low voltage.
2. Technical Protective Measures – e.g., fixed guards, safety curtains, emergency stops, lockout systems, sensors.
3. Organizational and Personal Protective Measures – work instructions, training, personal protective equipment (gloves, goggles, suits).

Example: In a metalworking plant, automatic guards with magnetic sensors prevent the press brake from operating when the guard is raised. This reduced the risk of hand crushing from high to low (the risk score dropped from 64 to 16, making the risk acceptable).

Methods and Tools for Risk Assessment

1. Risk Matrix

Application: quick and simple method for initial hazard screening.
Procedure: define probability categories (e.g., A–E) and consequence categories (e.g., 1–4), then check the table for risk level (e.g., L – Low, M – Medium, H – High).

Example: An operator can insert a hand into the cutting area, leading to severe injury. Probability is “moderate,” consequences are “serious.” The matrix indicates high risk, requiring immediate action such as guards or locks.

2. Risk Score

Application: for companies preferring a numerical, more detailed risk measure.

Example formula: Risk Score=P (Probability)×S (Severity)×E (Exposure)

P, S, and E are rated on a scale, e.g., 1–5, where 1 is the lowest value, 5 the highest. The total score (1–125) is divided into risk ranges.

Example: Risk of burn from a hot element. Assume:

• P = 3 (medium chance of contact, as the operator often interacts with this area),
• S = 4 (injury could be severe – extensive burn),
• E = 3 (operator exposed several times a day).

This results in a Risk Score = 3 × 4 × 3 = 36. If company policy states that scores above 30 enter the medium risk zone (requiring additional protective measures), action is needed.

3. Risk Graph

Application: designing control systems according to ISO 13849-1 or EN 62061.
Procedure: answer questions about injury severity (S), exposure frequency (F), avoidance possibility (P), and probability (W). The diagram shows the required safety category (PL a, b, c, d, e) or safety integrity level (SIL1, SIL2, SIL3).

4. FMEA (Failure Mode and Effects Analysis)

Application: analyzing system components for potential failures and consequences.
Procedure: for each potential failure, determine its severity (Severity), frequency (Occurrence), and detectability (Detection), creating an RPN (Risk Priority Number). A high RPN indicates areas needing priority attention.

5. HAZOP (Hazard and Operability Study)

Application: especially in the chemical industry and where key process parameters (pressure, flow, temperature) must remain within specified ranges.
HAZOP Study: a team of experts considers various deviations (too high, too low, none, delay, etc.) and analyzes potential outcomes of each anomaly.

Documentation and Training as Integral Parts of Risk Assessment

Risk assessment is beneficial only when results are documented and known to employees. ISO 12100 recommends that machine manufacturers develop instructions containing:

• Detailed information on potential hazards.
• Description of applied safety measures (guards, emergency stops, warning signals).
• Safe operation, maintenance, and cleaning procedures.
• Recommendations for personal protective equipment.

The next step is training. Even the best documentation is useless if operators and maintenance staff do not understand or are unaware of the implemented solutions. Conduct:

• Induction training for new employees.
• Periodic updates for all when process changes occur.
• Practical workshops on emergency button operation, LOTO procedures, warning signal interpretation, personal protective equipment use.

Example: In a soft drink manufacturing plant, new robots were introduced for palletizing. The production manager organized short, practical workshops where operators learned to operate control panels, reset alarms, and perform emergency stops. This reduced handling errors and potential incidents with robots.

Risk Assessment: Sample Risk Assessment Scenario with Point Methods

Assume a small furniture company purchased a new panel saw. The owner decided to conduct a risk assessment, involving a safety specialist and an experienced operator. They also plan to implement a point-based risk score.

1. Hazard Identification:
   • Hand contact with the saw blade.
   • Material kickback.
   • Wood dust causing respiratory issues.
   • Electric shock risk from damaged wires.
2. Hazard Analysis:
   • During cutting, workers often hold narrow pieces close to the blade.
   • The machine lacks an adequate dust extraction system.
   • The electrical installation in the hall hasn’t been checked for a long time.
3. Risk Assessment (Risk Score):
   • Hand cutting hazard: P = 4 (quite high, operator frequently interacts with the blade), S = 5 (could lead to amputation), E = 4 (exposure dozens of times a day). Risk Score = 4 × 5 × 4 = 80 (very high).
   • Material kickback: P = 2 (rare but possible), S = 3 (bruises, possibly fractures), E = 3. Risk Score = 2 × 3 × 3 = 18 (medium).
   • Wood dust: P = 3 (depends on wood type and exposure time), S = 2 (usually irritation, occasionally asthma issues), E = 4 (all day). Score = 3 × 2 × 4 = 24 (medium).
4. Acceptability Evaluation:
   • The company considers scores above 50 as high risk requiring immediate action.
   • Focus on the hand cutting hazard (score 80). Wood dust and kickback scores are in the 18–24 range, categorized as medium.
5. Implementing Risk Reduction Measures:
   • Install a guard over the blade with a locking system (cutting cannot begin without the guard closed).
   • Introduce pushers and guides to keep hands away from the blade.
   • Additional dust extraction system and training on the necessity of using filter masks.
6. Reassessment (Risk Score):
   • Hand cutting: Now P = 2 (guard + pushers), S = 5, E = 3. New score = 2 × 5 × 3 = 30 (reduced from 80 to 30).
   • Risk deemed medium, acceptable with implemented instructions and further safeguards.
7. Documentation and Training:
   • The company owner documents the modifications, describing them in the operating instructions.
   • Operators undergo training on new accessories (pushers, masks) and proper maintenance of the extraction system.

Risk Assessment: Best Practices and Common Mistakes

Best Practices:

1. Interdisciplinary Involvement: engineers, safety specialists, operators, and service technicians participate in risk assessment.
2. Periodic Updates: update risk assessment whenever the process changes or machines are modified.
3. Complete Documentation: risk assessment report understandable to all stakeholders.
4. Regular Training: one-time training is insufficient; reminders and practical workshops are crucial.
5. Applying the Safety Measures Hierarchy: first eliminate hazards through design, then use technical measures, and finally organizational measures.

Common Mistakes:

1. Treating Risk Assessment as a Formality: copying records from other projects can overlook specific hazards.
2. Underestimating Probability: operators often work in suboptimal conditions, drastically increasing risk.
3. Ignoring Practitioners’ Input: engineers in offices may not be aware of operators’ “tricks” that create unforeseen dangers.
4. Lack of Control Over Implemented Safeguards: if a guard or lock hinders work, employees may remove or bypass it, negating the effect.
5. Failure to Reassess After an Accident: any incident is an alarm signal. Reevaluate the process and previous analyses.

Risk assessment is not just a formal requirement but a real tool that protects people, enhances quality, and boosts production efficiency. Standards like ISO 12100, ISO 13849-1, ISO 13850, ISO 62061, or essential requirements define general frameworks, but each organization must adapt them to its specifics. The choice of method (risk matrix, Risk Score, Risk Graph, FMEA, HAZOP) depends on process complexity and the assessment team’s preferences.

Need Help with Machine Risk Assessment?

We offer comprehensive risk assessment services and risk assessment training, based on years of experience and current standards. We assist in selecting optimal risk assessment methods (such as Risk Score, risk matrix, or Risk Graph), provide practical technical solutions, and advise on creating documentation that meets current legal requirements.

If you want to streamline the risk assessment process in your facility, contact us. Together, we’ll choose a strategy, organize training, and implement best practices. Our goal is to ensure top-level safety – so that people work in safe conditions and the company avoids costly consequences of potential negligence.

FAQ: Risk Assessment