ISO14121 – Safety of Machinery – Principles for Risk Assessment The main objective is to describe a systematic procedure for risk assessment so that adequate and constant safety measures can be adopted. These are appropriate during the design, construction, modification, use and decommissioning of the machine.
The safety of machines can be determined in 5 steps.
Documentation of the risk assessment process must be kept.
Determination of the Limits of Machinery
Defining machine limits requires the following points to be considered when assessing risk.
- Determining requirements for all phases of the machine’s life
- Defining the intended use and operation and the foreseeable misuse and malfunction
- Defining the machine’s range of use as limited by factors such as the operator’s gender, age, dominant hand, and physical abilities (e.g., impaired eyesight or hearing, size, and strength)
- Expected user training, experience, and competence
- Possibility that people may be exposed to machine hazards
- Possibility that people may be exposed to machine hazards if a foreseeable machine hazard occurs
Hazard identification means checking for all the hazardous conditions and hazardous events associated with the machine. This involves predicting hazards that may be caused by the machine, such as the following:
Mechanical hazards: Severing, entanglement, crushing, etc.
Electrical hazards: Contact with live parts, static electricity, etc.
Thermal hazards: Health disorders due to contact with high-temperature parts or working in a high-temperature or low-temperature environment
Methods for clarifying hazards include the following:
- Check lists
- Hazard and Operability Study (HAZOP)
- Failure Mode and Effect Analysis (FMEA)
- Fault Tree Analysis (FTA)
- “What-if” method
After checking for hazardous conditions and hazardous events, the risk factors are determined and the risks are estimated from the degree or possible harm and the probability of the hazard occurring.
After estimating the risk, the risks are evaluated to determine whether the level of risk must be reduced. If the level of risk must be reduced, safety measures, such as changing the design or providing safeguards, are taken.
The following actions are taken.
- Eliminate or reduce exposure to hazard as far as practical.
- Reduce the probability and severity.
- Use safeguards and safety devices.
- Determine that the performance and functional characteristics of the safety measures are suitable for the machine and its use
Risk Reduction under ISO12100
ISO 12100 (-1/-2) has been formed into JIS standard JISB9700 (-1/-2).
The main purpose of this standard is to set out a framework and directions for general machine safety, so that designers can design safe machines.
The introduction of ISO12100-1:2003 states that “The concept of safety of machinery considers the ability of a machine to perform its intended function(s) during its lifecycle where risk has been adequately reduced”. The 3-step method, which is an expression of this risk reduction methodology, has been further implemented into the “Risk Reduction Process” illustrated on the following page, but it does not yet seem to have been fully recognized in actual applications. ISO12100-2 sets out examples of various measures, a sample of which are shown below.