Leerkes Consultancy Machine safety in machine building
General
This page provides a summary of the steps, derived from the ISO 12100, ISO 13849-1/2, and EN 62061 standards, that are necessary to design machines with safety in mind.
To implement risk assessment and reduction, the designer must take the following steps:
- Conduct a risk assessment with a multidisciplinary team.
- Process for risk reduction for the hazard.
- Determination of the required performance level (PLr).
- Design of safety-related parts of the control system.
- Evaluation of the achieved performance level (PL).
- Validation process.
Leerkes Consultancy has extensive experience in performing risk assessments, design, and risk evaluation to ensure that machines are designed with safety in mind. We have years of experience in designing safe machines and working in multidisciplinary teams to perform risk assessments.
Risk assessment
A risk assessment consists of:
- Risk analysis, consisting of:
- Determination of the limits of the machine.
- Hazard identification.
- Risk assessment.
- Risk evaluation.
Determining the limits of the machine
When conducting a risk assessment, it is important to determine the limits of the machine and consider all stages of its life cycle.
This involves identifying the characteristics and performance capabilities of the machine or series of machines within an integrated process, as well as the people, environmental factors, and products associated with it, taking into account the limits of the machine.
Hazard identification
An essential part of risk assessment is the systematic identification of reasonably foreseeable hazards, hazardous situations, and/or hazardous events during all phases of the machine’s life cycle. To effectively identify hazards, a team of professionals from multiple disciplines must consider the following factors:
- Human interaction throughout the machine’s life cycle.
- Possible states of the machine.
- Unintended behavior of the operator or reasonably foreseeable misuse of the machine.
Risk assessment
The risk assessment must be carried out for each hazardous situation by determining the elements of risk:
- Severity of the damage.
- Probability of damage occurring.
- Exposure of persons to the hazard.
- Occurrence of a hazardous event.
- Possibility of avoiding or limiting damage.
Risk evaluation
Once the risk assessment has been completed, the risk evaluation must be carried out to determine whether risk reduction is necessary. If risk reduction is necessary, appropriate protective measures must be selected and implemented.
Leerkes Consultancy is highly skilled in the necessary standards, including ISO 12100, ISO 13849-1/2, and EN 62061.
Risk reduction process for the hazard
The hazard analysis and risk reduction process for a machine requires that hazards be eliminated or reduced through a hierarchy of measures:
- Application of inherently safe design methods to control systems.
- Safety measures and/or additional protective measures.
- Information for use.
Determination of required performance level (PLr)
Guidance for selecting parameters S, F and P for the risk estimation:
- Severity of injury
- S1; slight (normally reversible injury)
- S2; serious (normally irreversible injury or death)
- Frequency and/or exposure times to hazard
- F1; seldom-to-less-often and/or exposure time is short
- F2; frequent-to-continuous and/or exposure time is long
- possibility of avoiding hazard or limiting harm
- P1; possible under specific conditions
- P2; scarcely possible
The required performance level, ranging from low (performance level a) to high (performance level e), can be determined based on the chosen risk parameters in the following figure.
Design of Safety related parts of Control system
A typical safety function diagrammatic presentation is given in following figure showing a combination of
safety-related parts of control systems (SRP/CS) for:
- Input
- Logic/processing
- Output/power control elements
- Interconnecting means
Evaluation of the achieved performance level (PL)
Determine the PL for each selected SRP/CS or combination of SRP/CS that performs a safety function by estimating the following factors:
- MTTFd (mean time to dangerous failure) value for single components
- Using the classifications of Low, Medium, and High
- The DC (diagnostic coverage)
- Using the classifications of None, Low, Medium, and High
- CCF (Common cause failure)
- The minimum score required to pass is 65%
- The structure
- Using the classifications of category B, 1, 2, 3, and 4
- The behaviour of the safety function under fault condition(s)
- Safety-related software
- Systematic failure
- The ability to perform a safety function under expected environmental conditions.
The performance level can be determined by reading the chosen parameters in the following figure:
Validation Process
Software safety requirements
The primary focus for all lifecycle activities of safety-related software should be on avoiding faults introduced during the software lifecycle (as shown in the figure below). The goal of the following requirements is to ensure software that is readable, understandable, testable, and maintainable.
Verification that achieved PL meets PLr
It is necessary that the PL (Performance Level) of each individual safety function corresponds to the required performance level (PLr) of the related SRP/CS as specified in the figure. If there is no correspondence, an iterative process must be carried out as described in the figure.
If you need expert assistance in designing machines with safety as a top priority, Leerkes Consultancy can provide the support you need. With our extensive experience in risk assessments, design, and risk evaluations, we can ensure that your machines are designed with safety in mind.
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