Risk assessment: the machine builder's dilemma
As the risk assessment matrix becomes ever more complex, how does the
machine manufacturer discharge its responsibilities for a particular
machine? Richard Poate sheds some light on the matter
The machine builder is obliged to ensure that equipment placed on the
market complies with a whole raft of regulations.* This responsibility
will be at least partly discharged by ensuring that the equipment carries
the CE mark, is accompanied by a Declaration of Conformity, and that a
Technical File is prepared and available to the enforcement authorities.
But even the application of all the relevant standards and regulations
does not release the manufacturer from making a risk assessment covering
all kinds of dangers and potential hazards.
If the equipment is manufactured within the European Community (EC), the
supplier must ensure that certain checks are performed before it is
supplied. The supplier should never assume that CE marking is a guarantee
of safety. For equipment manufactured outside the EC, the supplier takes
on the full legal responsibility of the manufacturer. For secondhand
equipment, the supplier may or may not be liable under the Supply of
Machinery (Safety) Regulation, depending on the age of the equipment, but
will still be responsible for ensuring that it is in a safe state under
the Provision and Use of Work Equipment Regulations (PUWER).
Machinery that is covered only by a declaration of incorporation must be
checked by the installer or assembler of the final product for compliance
with all relevant health and safety requirements, and a declaration of
conformity must be issued. In addition, the machinery supplier assumes
responsibilities, shared with employers, under PUWER in relation to the
provision of training, operating and maintenance materials and, if also
the installer of the equipment, may need to assess site-specific risks as
well as inherent machine risks.
While existing legislation deals essentially with 'hardware' issues such
as the risk of trapping, crushing, electric shock and so on, the
proliferation of software-based safety systems has led to the publication
of a new standard, IEC 61508, adding to an already heavy burden of risk
assessment and control.
CE marking and compliance with these statutory requirements should be
seen as a minimum requirement, and the machinery manufacturer is obliged
to consider an assessment of the hazards and risks associated with use of
the equipment. This can prove a very complex task, involving risk
assessment to the guidelines published in EN 1050:1997, Safety of
Machinery - Principles for Risk Assessment.
One of the complications is that the most easily recognised hazards may
not be those that apply in a particular situation. Ergonomic risk,
contact with hazardous substances such as mineral oils, treatment of
spillages, first aid provisions, must all be given due consideration. If
the supplier is assembling components into a production line, it is
required to ensure that the interaction of the machines creates no
hazard. This will demand evaluation against numerous regulations.
There is no simple, 'checklist' method for applying the principles laid
out in EN 1050 to the analysis of risk for a specific machine in a
specific working environment, and there is no substitute for experience
in recognising the dangers and devising appropriate remedies.
Risk, for any specific hazard, is a function of the severity of possible
harm and the probability of the occurrence of that harm. Severity is
quantified by taking into account the number of persons, property and
environment, which might be affected, and the nature of possible injuries
or damage to health, from a simple scratch to multiple fatalities.
Probability of occurrence of harm is much more complex, taking into
account the need for access to the danger zone, the number of persons
requiring access, and the frequency and duration of access. Reliability
and other statistical data, history of accidents and damage to health,
and risk comparisons must be taken into consideration for all hazardous
events whether of human or technical origin.
Figure 3: The complete risk management process includes re-assessment
following the implementation of protective measures, and recommendations
for warning signs to cover residual risk.
The possibility of avoiding or limiting harm rests on an assessment of
the skills requirement; awareness through general information,
observation or warning signs; and practical experience and knowledge of
the specific or similar machinery.
The risk assessor uses a number of tools in dealing with risk. General
measures can involve examination of manuals to ensure that hazards are
adequately covered, instructions are clear, and skill requirements are
identified. A 'what if' exercise will identify consequential risk and
leads to suitable preventive or protective measures. What if a person
without appropriate skills - a cleaner, for example - accesses a
hazardous area?
For each hazard, the analysis shown in Figure 1 is carried out, where S0
to S3 represent the result of damage - from no danger, through minor
(reversible) injury and serious (irreversible) injury, to death. A1 and
A2 represent duration of stay from seldom or frequently, to often or
permanent. E1 to E3 represent the possibility of avoidance - from
possible to barely possible - and W1 to W3 represent the possibility of
occurrence - from little to frequent. Clearly, a score in the top
left-hand corner denotes minimal risk, while as scores approach the
bottom right-hand corner, moderation or elimination of the hazard becomes
essential.
Considerable skill is required in order to carry out an exhaustive
assessment of risk in association with a particular machine and the
factory floor in general. Equally, skill and knowledge are required in
the implementation of measures to counter risk. There are many standards
applicable to preventive and protective devices, as Figure 2 shows.
Figure 3 summarises the complete risk management process, which includes
re-assessment following the implementation of protective measures, and
recommendations for warning signs to cover residual risk. Even then, the
manufacturer/supplier/installer may be called upon to carry out a
periodic machine safety inspection, under PUWER, to detect deterioration
of parts which would lead to danger but will not be picked up through
operator checks and normal servicing regimes.
Proper risk assessment in line with the regulations and standards is now
more important than ever, particularly in today's litigious climate. But
the task requires vast experience and a well-defined methodology which
are often outside of the in-house skills of machinery manufacturers,
suppliers and installers, and are better sourced from a professional
service provider. Manufacturers who have experienced the losses that can
accompany failure to produce a safe product, will readily appreciate the
cost/risk trade-off.
* Health and Safety Requirements of the Supply of Machinery (Safety)
Regulations 1992 (as amended); the Provision and Use of Work Equipment
Regulations (PUWER) 1998 (as amended); Electrical Equipment (Safety)
Regulations and Electromagnetic Compatibility Regulations.
Richard Poate is with TUV Product Service