Machine Risk management involves two major steps: risk assessment and risk reduction.

Machine Risk Assessment

In general, any improvement to a machine’s safety begins with a risk assessment.

This operation includes a risk analysis, followed by a risk evaluation.

Machine Risk Analysis

A risk analysis has three steps:

Determining the limits of the machine;

Determining (identifying) the hazards;

Estimating the risks.

Determining the limits of the machine

The very first step in the risk management process involves establishing the limits of the risk assessment.

At the end of this step, you must be able to describe the conditions in which

the machine will be used: who will use the machine, for how long, with what materials, etc.

The machine’s life cycle (design, installation, use, unjamming, maintenance

and disposal), foreseeable uses, and the users’ expected level of experience are also established.

Only once these conditions have been determined can hazard identification and risk estimation begin.

Identifying the hazards

Hazards are the cause of all hazardous situations.

When exposed to a hazard, a worker is in a hazardous situation, and the

occurrence of a hazardous event leads to an accident that can result in harm.

Hazard identification is one of the most important steps in the machine risk management process.

The list of hazards must be carefully established.

The CSST’s information kit can be useful for this.

A list of all the energy sources or all the man-machine interfaces that can

affect the health and safety of exposed workers must be carefully established, whether they are moving elements (mechanical hazard),

electrified components (electrical hazard), machine components that are

too hot or too cold (thermal hazard), noise, vibration, visible (laser) or

invisible radiation (electromagnetic), hazardous materials or awkward postures (ergonomic hazard).

These hazards are then linked to the hazardous situations to which the workers are exposed.

Risk Estimation

Risk estimation consists of comparing the different hazardous situations identified.

This relative comparison establishes an action priority, for example.

Risk = Severity * Probability of Occurrence

Risk (R) is defined as the combination of the severity of the harm (S) and the probability of occurrence of this harm (O).

The probability of the harm occurring can be divided into three parts:

(F) : the frequency and duration of exposure to the hazard ;

(O) : the probability of a hazardous event occurring ;

(A) : the possibility of avoiding or reducing the harm.

To make this estimation easier, a risk index can be defined for each hazardous situation.

Document ED 807 from the INRS proposes a range of values to be associated with the components of the risk.

Once the ranges of values have been defined, risk estimation tools can be used.

These can be graphical tools, matrix tools, etc.

In practice, it is important to establish objective limits for factors S, F, O and A beforehand by consulting references.

The following examples showing the use of the risk graph.

Consequence / Severity of the harm (S)

The severity of the harm can be estimated by taking into account the severity of the injuries or adverse health effects.

The proposed choices are:

C1 Minor injury (normally reversible).

For example: scrape, laceration, bruise, slight injury, etc.;

C4 Serious injury (normally irreversible, including death).

For example: limb broken or torn out, serious injury with stitches, etc.

Frequency or duration of exposure to the hazard (F)

The exposure can be estimated by taking into consideration:

Need to access the danger zone (for example, for normal operation, maintenance or repairs);

Reason for access (for example, manual feeding of materials);

Time spent in the danger zone;

Number of people that must access it;

Frequency of access.

The proposed choices are:

F1 From rare to rather frequent, or short exposure;

F2 From frequent to continuous, or long exposure.

Probability of the hazardous event occurring (O)

The probability of the hazardous event occurring can be estimated by considering:

Reliability data and other statistical data;

Accident history;

History of adverse health effects;

Comparison of the risks with those of a similar machine (if certain conditions are met).

The proposed choices are:

O1 Very low (from very low to low).

Stable, proven technology recognized for safety applications, material strength;

O2 Low (from low to average). Hazardous event related to a technical failure or event caused by the action of a qualified,

experienced, trained worker with an awareness of the high risk, etc.;

O3 High (from average to high).

Hazardous event caused by the action of a worker lacking experience or specific training.

Possibility of avoiding the harm (A)

The possibility of avoidance allows the harm to be prevented or reduced in relation to:

Workers using the machine;

Rapidity of appearance of the hazardous event;

Awareness of the hazard’s existence;

Possibility of the worker avoiding or limiting the harm (for example, action, reflex, agility, possibility of escape).

The proposed choices are:

A1 Possible under certain conditions;

A2 Impossible or rarely possible.

By combining the results obtained for the four parameters, the risk index is defined by using the risk graph, which allows six increasing risk indexes to be defined (varying from 1 to 6).

The risk estimation tools, are often used at the time of risk evaluation.

Reference provides more information on the conditions that help determine whether the safety objective has been met.

For example, an air compressor is located in the work area; two in-running nips exist between the belt and the pulleys:

Severity of the harm: S2, high (loss of at least one finger);

Duration of exposure: F2, because the compressor is in the work area where the workers move around;

Occurrence: O3, because the worker is not trained in using the targeted machine;

Possibility of avoidance: A2, because the finger cannot be removed from
the in-running nip once it has been caught, if the compressor starts automatically;

Calculated risk index: 6.

Once all the hazardous situations have been estimated, the different risk

indexes must be compared to ensure consistency in the entire analysis.

Machine Risk Evaluation

The last step in the risk assessment process consists of making a judgement

about the estimated risk level.

At this step, it is determined whether the risk is tolerable or not.

When the risk is considered intolerable (high risk index, as in the case of

the compressor in the previous example),

risk reduction measures must be selected and implemented.

In order to ensure that the chosen solutions fulfill the risk reduction

objectives without creating new hazardous situations,

the risk assessment procedure must be repeated once the solutions have been applied.

Machine Risk Reduction

Once the risk assessment step has been completed, if the evaluation

prescribes a reduction of the risk (which is considered intolerable),

means to be applied to achieve the risk reduction objectives must be selected.

The figure below illustrates the hierarchy in the risk reduction measures.

Hazard elimination and machine risk reduction

As stated in section 2 of Québec’s Act respecting occupational health and safety, eliminating the hazard is the first objective.

The risk must be eliminated in order to make the situation safe: this is called inherently safe design.

According to section 4.1 of ISO 12100-2:2003: “Inherently safe design measures are the first and most important step in the risk reduction process […].

Inherently safe design measures are achieved by avoiding hazards or reducing risks by a suitable choice of design features of the machine itself […]”

It is therefore at the machine design step that the worker’s safety is ensured.

The designer tries to improve the machine’s characteristics: creating a gap

between the moving components in order to eliminate the trapping zones,

eliminating sharp edges, limiting the drawing-in forces or limiting the energy levels (mass, velocity, acceleration) of the moving components.

Guards and protective devices

They are fixed or interlocking guards or interlocking

guards with guard locking, rank just below inherently safe design in terms

of effectiveness in the hierarchy of risk reduction measures.

Protective devices and electro-sensitive protective devices come next,

such as safety light curtains, pressure mats, surface detectors or two-hand controls.

The document, Amélioration de la sécurité des machines par l’utilisation

des dispositifs de protection10, presents an introduction to the use of these devices.

Fixed guards and guards with interlocking devices

One of the best ways of reducing exposure to a hazard is to prevent access to it by installing a guard.

Ideally, it is “fixed” and a tool must be used to remove it.

However, the guard may have to be opened for periodic access to the

danger zone, for example, for production, unjamming or maintenance purposes.

These “movable” interlocking guards or interlocking guards with guard

locking must send a stopping signal to the machine as soon as they are opened.

If the machine stopping time is short enough for the hazard to stop before the worker can reach it, an interlocking guard is used.

However, if the hazard stopping time is longer, an interlocking guard with

guard locking is used which, in addition to performing the functions of the

interlocking guard, locks the guard in the closed position until the hazard has completely passed.

Protective devices

If a guard, either fixed or movable, cannot be considered, one must determine whether a protective device can be used.

A protective device11 is defined as any safeguard, other than a guard.

For example, it can be an optoelectronic protective device (safety light curtain, surface detector),

a validation device, a pressure mat, a two-hand control, etc.

These devices are specially designed to reduce the risk associated with a hazardous situation.

Warnings, work methods and personal protective equipment

Procedures, warnings, work methods and personal protective equipment are not considered as being the most effective means.

Although essential in situations where no other solution seems to provide

satisfactory results, their effects on safety improvement are considered less significant.

They are often used with other risk reduction methods.

Training and information

In all cases where the hazard cannot be eliminated, workers must receive

training so that they are informed about the nature of the residual risk to

which they are exposed and the means that are used for reducing this risk.

This training is in addition to the general training that the employer must

provide to the workers for the purpose of using the machine.

Verification of the final result

In order to ensure that the chosen solutions fulfill the risk reduction objectives without creating new hazardous situations,

the risk assessment procedure must be repeated once the solutions have been applied.