Safeguarding The Hazards

The dangers associated with conveyors, the standards that relate to guarding and the best approach for adequately and cost-effectively safeguarding conveyors without affecting productivity

Conveyors are essential to the efficient operation of most quarries, continually transferring material from one location to another. Despite their apparent simplicity, however, conveyors account for a large number of injuries to workers, sometimes with fatal consequences. Many of these incidents occur during normal operations such as production activities, clearing blockages and general cleaning.

Since 1998, users of conveyors have been legally obliged to perform a PUWER (Provision and User of Work Equipment Regulations) assessment and this often reveals that existing safeguards are inadequate and that additional measures are needed. Even companies purchasing custom-built conveyors frequently find they have to design and fit extra guarding. Conveyors for carrying personnel, however, are treated differently and are outside the scope of this article.

As well as the PUWER 98 Regulations there are several other regulations, standards and codes of practice that need to be considered. Three examples are:

• BS EN 620: 2002: ‘Continuous handling equipment and systems – Safety and EMC requirements for bulk materials’
• BS 4531: 1986: ‘Specification for portable and mobile troughed belt conveyors’
• 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’. Other parts of this standard may also be relevant, including: Part 11 – Fixed slat conveyors with horizontal shafts; Part 12 – Mobile slat conveyors with horizontal shafts; and Part 18 – Conveyors and elevators with chain elements. It should be noted, however, that although the various parts of BS 5667 are listed by BSI as ‘current, proposed for withdrawal’, compliance is still required as long as they 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 stand-alone 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. Advice can be obtained from suppliers, consultants or from the HSE’s Infoline on tel: (08701) 545500.

The ultimate objective is to ensure that machinery is safe, so users should undertake a risk assessment and install the necessary safeguards to reduce the risks to an acceptable level. Procter Brothers offer a free risk assessment calculator, available via email at [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 standard or configured-to-order units.

Most hazards associated with conveyors relate to the nip points, which can easily draw in clothing, tools, fingers or limbs, depending on the size, speed and power of the conveyor. Standards such as BS 5667-19 and BS EN 620 highlight where nip points typically exist, but users should be aware that reversible belt conveyors need nip points to be 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 also be a hazard and personnel need to be protected from spilt, ejected or falling material, especially where conveyors run overhead.

After identifying the hazards by means of a risk assessment, appropriate safeguards need to be selected. Either fixed guards (ie those requiring the use of tools for their removal) or movable guards may be chosen, depending on the frequency with which access is required. For long conveyors it is seldom practical to install guarding along the entire belt (let alone fit interlocked movable guards) due to the lengths involved. In such situations, isolation procedures, safe working practices and pull-cord-operated emergency-stop controls all have an important role to play.

Welded wire mesh is often used to guard conveyors or parts thereof, 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’. For couplings, power-transmission components and conveyors there is a risk of parts being ejected, so sheet metal may be more appropriate. In some cases it is simpler and most cost-effective to use physical perimeter guarding to deny access to the conveyor, with suitable access-control systems for use during maintenance and cleaning.

To protect personnel from objects falling from overhead conveyors, guarding must be designed and constructed to withstand the high forces that might be involved. Construction materials typically include steel channel and heavy-duty expanded metal or open-grip steel flooring. Alternatively, fencing can be used to prevent access to the hazardous areas at ground level.

Care has to be taken when installing guarding to ensure that no new hazards are introduced and that plant efficiency does not suffer. For these reasons it is essential to consult with managers and workers before designing new guarding. Additional measures can also be taken, such as fitting remote greasing 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 that, as far as possible, routine cleaning and clearing of spillages can take place without disturbing the guarding, eg by incorporating rodding access points.

Finally, 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 just one example of how to improve safety where it is not possible to view all the hazardous areas from the control station.

For someone 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 can design, fabricate and install guarding far more quickly and cost-effectively than non-specialists. 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 author, Jeremy Procter, is convenor of the European Standards Committee responsible for machine guards and managing director of Procter Machinery Guarding