Risk Assessment – The Machine Manufacturer’s Dilemma
By Richard Poate, TUV Product Service
Machinery manufacturers and suppliers are confronted by a bewildering array of legal requirements ensuring the safety of users, but even the application of all relevant standards and regulations does not release the manufacturer from making a risk assessment covering all kinds of dangers and potential hazards. As the risk assessment matrix becomes ever more complex, how does the manufacturer discharge its responsibilities for a particular machine?
Statutory requirements
The machine builder is obliged to ensure that equipment placed on the market complies with the essential 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), and possibly also Electrical Equipment (Safety) Regulations and Electromagnetic Compatibility 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.
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 PUWER
Machinery which 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 undertake to assess site-specific risks as well as inherent machine risks.
While existing legislation deals with essentially ‘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 the requirement to ensure functional safety to an already heavy burden of risk assessment and control.
Risk assessment
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 – crushing, cutting, entanglement and so on – are not the only ones which may apply in a particular situation. Ergonomic risk, contact with hazardous substances such as mineral oils, treatment of spillages, first aid provisions, etcetera 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.
Principles of risk assessment
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, for example ranging from a 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. 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.
Risk analysis methodology
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 skills 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, for example, a cleaner, accesses a hazardous area?
For each hazard, the analysis shown in Fig. 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.
Fig. 1 A risk analysis for each hazard shows which ones demand moderation or elimination.
Dealing with risk
It will already be apparent that 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 Fig. 2 shows, and as part of its Machinery Risk Assessment service, TUV Product Service is able to recommend measures based on its knowledge of the standards, years of experience, and close relationships with manufacturers. One important aspect of recommending protective solutions is to ensure that they are not so complicated and time-consuming that operators are tempted to disable them in order to get on with the job.
Fig. 2 Many standards apply to measures protecting employees from risk.
Fig. 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.
Fig. 3 The complete risk management process includes re-assessment following the implementation of protective measures, and recommendations for warning signs to cover residual risk.
An additional requirement
As mentioned earlier, existing legislation deals with essentially ‘hardware’ issues such as the risk of trapping, crushing, electric shock and so on, but the proliferation of software-based control systems has led to the publication of the standard IEC 61508 (and ifs sector-specific derivatives), adding the requirement to ensure functional safety at all stages of the lifecycle. Although not currently a mandatory requirement, this standard is being increasingly used in many areas of industry as manufacturers and employers become more aware. Given the complexity of simulating fault conditions in order to test the functionality of software-based safety systems, assessment by a professional service provider, such as TUV Product Service, gives a high level of confidence.
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 inhouse skills of machinery manufacturers, suppliers and installers, and better sourced from a professional service provider. Manufacturers who have experienced the losses which can accompany failure to produce a safe product, will readily appreciate the cost/risk tradeoff.
For further information contact TUV Product Service Limited, Segensworth Road, Titchfield, Fareham, Hampshire P015 5RH
Tel: (01329)443322. Fax: (01329)443421.
Email: info@tuvps.co.uk URL: http://www.tuvps.co.uk/
Due to matters beyond our control TUV have found it necessary to run a fill-in article for this issue. The series will be back on track in Issue 50.
This article first appeared in Engineering Talk, July 2003 and a shortened version in Design Products & Applications, August 2003.
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