Safeguarding the Hazards Presented by Conveyors
By Jeremy Procter, Convenor of the European Standards Committee responsible for Machine Guards, and Managing Director of Procter Machine Guarding
Conveyors are perhaps the simplest form of automation, transferring parts, assemblies or loose material from one place to another so as to avoid manual handling. Nevertheless, despite their apparent simplicity, conveyors account for a large number of injuries to workers, sometimes with fatal consequences. For example, figures published by the HSE (Health and Safety Executive)*, indicate that in the food and drink industries some 30 percent of all injuries caused by machinery are attributable to conveyors – which is more than any other class of machine – with 90 percent of conveyor injuries occurring on flat belt conveyors and 90 percent of the injuries involving well known hazards such as in-running nips, transmission parts and trapping points between moving and fixed parts. Furthermore, 90 per cent of injuries occur during normal operations such as production activities, clearing of blockages, and general cleaning.
Since 1998, users of conveyors have been legally obliged to perform a PUWER assessment – which often reveals that existing safeguards are inadequate and that additional measures are needed. In addition, companies purchasing off-the-shelf, configured-to-order or custom-built conveyors frequently have to design and fit extra guarding. Elsewhere, companies are in a slightly better position if they build new conveyors in-house and are able to take safeguarding into account at the design early stage.
The PUWER 98 Regulations (Provision and User of Work Equipment Regulations, 1998) have already been mentioned, but there are several other regulations, standards and codes of practice that need to be considered. Three such examples are BS EN 620: 2002, ‘Continuous handling equipment and systems – Safety and EMC requirements for fixed belt conveyors for bulk materials’, BS 4531: 1986, ‘ Specification for portable and mobile troughed belt conveyors’, and BS 7300: 1990, ‘ Code of practice for safeguarding of the hazard points on troughed belt conveyors’.
Another is BS 5667: Part 19: 1980, ‘Specification for Continuous mechanical handling equipment – Safety requirements. Part 19, Belt conveyors – examples for guarding of nip points’. Several other parts of this standard may also be relevant, such as Part 11 (fixed slat conveyors with horizontal shafts), Part 12 (mobile slat conveyors with horizontal shafts), Part 14 (live roller conveyors with positive or friction drive), Part 18, (conveyors and elevators with chain-elements), and more. Note, however, that the various parts of BS 5667 are listed by BSI as ‘Current, proposed for withdrawal’, but compliance with them is required so long as they do remain current.
Ensuring that a conveyor complies with the relevant standards and codes of practice is relatively straightforward, but the question of CE marking is a more difficult area. While there are some situations where a conveyor will be supplied as a standalone machine – and will, therefore, need to be CE marked – there are others where the conveyor needs a certificate of Conformity so that it can be incorporated within a larger machine that is then CE marked as a whole. If in doubt, seek advice from suppliers, consultants, or contact the HSE’s confidential Infoline (telephone 08701 545500).
But whatever course of action is taken, bear in mind that the ultimate goal is to ensure that the machinery is safe, so users should undertake a risk assessment and install the necessary safeguards to reduce the risks to an acceptable level. To help with such risk assessments, Procter Brothers offers a FREE Risk Assessment Calculator that can be downloaded, or requested by sending an email to [email protected].
In line with general good practice, the objective should be to design-out hazards, rather than safeguarding them but, in reality, this is unlikely to be feasible where conveyors are already operating or have been purchased as off-the-shelf or configured-to-order units.
Most hazards associated with conveyors relate to the nip points, which can easily draw in clothing, tools, loose hair, fingers or limbs, depending on the size, speed and power of the conveyor. The standards, such as BS 5667-19 and BS EN 620, highlight where nip points typically exist, but be aware that reversible belt conveyors need nip points guarded for both directions of travel (unless reversing is only used for maintenance and cleaning operations, in which case safe working practices, hold-to-run and reduced speed/power controls may be adequate).
Other hazards exist in the vicinity of transmission components, couplings and tensioners. The moving edge of the belt can, itself, be a hazard, and personnel need to be protected from spilt, ejected or falling objects, especially where conveyors run overhead such as is common in the white goods and automotive industries.
Having identified the hazards by means of a risk assessment, appropriate safeguards need to be selected. It is highly likely that fixed guards (ie those requiring the use of tools for their removal) or movable guards will be chosen, depending upon the frequency with which access is required. For long conveyors, it is often not practical to interlock every movable guard due to the large numbers involved. In such situations, isolation procedures, safe working practices and rope-operated emergency stop controls have an important role to play.
Welded wire mesh is frequently used to guard conveyors, with a mesh aperture size and guard geometry to suit the requirements of BS EN 294: 1992, ‘ Safety of machinery. Safety distances to prevent danger zones being reached by the upper limbs’ (more about BS EN 294). For couplings, power transmission components, and conveyors where there is a risk of parts being ejected, sheet metal may be more appropriate, and clear polycarbonate is popular in the food, drink and pharmaceutical industries. In some cases, it is simpler and more cost-effective to use physical perimeter guarding to deny access to the conveyor, with suitable access control systems for use during maintenance and cleaning, and/or for loading and unloading parts or assemblies. Occasionally it is appropriate to use safety mats or light barriers to stop the conveyor in the event of the hazardous area being entered.
To protect personnel from objects that might fall from overhead conveyors, guarding must be designed and constructed to withstand the high forces that might be involved (for example, conveyors handling car bodies). Materials of construction typically include steel channel and heavy-duty expanded metal or open grip steel flooring.
Care has to be taken when installing guarding to ensure that no new hazards are introduced, and that plant efficiency does not suffer. For that reason, it is essential to consult with managers and workers before designing the new guarding. Additional measures can also be taken, such as fitting remote grease points so that the conveyor can be lubricated without having to remove guards, and belt alignment mechanisms that can be operated from outside the guards. Guarding should also be designed, so far as possible, such that routine cleaning and clearing of spillages can take place without disturbing the guarding – such as by incorporating rodding access points. Lastly, the importance of education, training, safe systems of work, power lock-offs and effective supervision should not be underestimated. Safe start-up procedures, typically with warning sounders and a time delay, are an example of how to improve the safety of long conveyors where it is not possible to view all the hazardous areas from the control station.
For somebody who has undertaken a PUWER assessment and concluded that additional conveyor safeguarding is required, the task may seem daunting. Nevertheless, it is possible to save time and money without cutting corners. Specialist guarding contractors, such as Procter Machine Guarding, can design, fabricate and install guarding far more quickly and cost-effectively than non-specialists. For instance, Procter’s draughtsmen typically create guard drawings in a fraction of the time that it would take draughtsmen more used to working with general machinery. Experience and an in-depth knowledge of the appropriate standards also help to get the designs right so that they meet the operational and standards requirements first time, without having to be modified ‘in situ’.
The Procter Service
Procter offers free on-site surveys, after which detailed quotations are prepared. Fabrication takes place in Procter’s own facilities, and finishes can be applied in the customer’s choice of colour. The company also supplies and installs remote grease points, guard interlocks, or any other associated hardware that may be required to complete the project. For perimeter guarding, Procter offers the unique modular Angel guarding system that is extremely quick and simple to specify and install.
In addition to the bespoke and modular guarding, Procter Machine Safety also designs, fabricates and installs access platforms, ladders, and other equipment that may be required alongside the conveyors, or which customers need so as to comply with the new Working at Height Regulations.
To find out more about conveyor guarding or other products and services from Procter Machine Guarding, please contact Procter Machine Safety.
* Source: HSE Information Sheet FIS25, ‘Safeguarding flat belt conveyors in the food and drink industries’, April 2001.