Colin Crowley, Technical Sales Engineer UK & Ireland, Itoh Denki Europe
In any application where people are required to work in close proximity to moving equipment, safety must always be a key consideration.
Safety of individual operatives is of course absolutely critical, to ensure compliance with local and international regulation and minimise the risk of any legal or reputational implications emanating from safety breaches.
Alongside this, consideration must also be given to the safety of the products being handled and processed, particularly where these are fragile, hazardous or valuable.
Product manufacturers in the EU are governed by CE standards of safety which cover everything from mechanical and electrical risk to the risk of electronic interference, and risks emanating from the motion of equipment when in service. These apply to both the manufacture of equipment and its installation and maintenance, meaning that designers, installers and system integrators must pay careful attention to their obligations.
CE regulations still currently apply to systems being installed and used in the UK. However, from January 2024, these systems will instead be covered by UKCA guidelines. The good news is that these will be largely the same as the current CE regulations. However, anyone involved in the design, installation and configuration of moving equipment must still pay careful attention to all aspects of these guidelines to ensure compliance and protection for people and products.
Ensuring operative safety on conveyor lines
While system installation and configuration must always be undertaken in a way which ensures operative safety, the creation of safe conveying systems should be considered at a far earlier stage – the actual system design itself.
Traditional conveyors mainly rely on powerful 400V motors driving extended lengths of conveyor, often using long shafts and round pulleys, or chains and sprockets for heavier loads, such as pallet conveying systems. Indeed, for many years, this was the only way to convey multiple heavy loads each weighing up to 1 tonne or even more.
This means a great deal of power going through the system at any one time, with the potential for serious injury if, for example, an operative’s hand were to come into contact with the conveyor, chain or sprocket, given the high torque forces involved.
Covers for chains provide a way to mitigate some of the risk to operatives working nearby, but modern system designers have discovered ways to do away with chains and sprockets altogether, even for systems handling pallets.
Modern conveying systems based on mechanical rollers are now typically divided into much smaller, modular sections, each with its own less powerful motor. This divides the power needed to move a product along a line, with the torque at any point being much lower, meaning the system is much more forgiving, should a hand or finger come into contact with the conveyor.
The conveying mechanism itself is much safer too. These systems no longer rely on fast-moving chains and sprockets to move goods along the line; instead, rubber pulleys are used to link each roller to its neighbour. Once again, the safety advantages are considerable, while the need for additional covers – and the associated cost – is negated.
This type of system has become the norm for the handling of smaller loads, but larger versions are now available which can handle loads of up to 1 tonne, meaning they are starting to service on pallet conveying lines where they confer all the same safety benefits while again slashing the cost of additional safety measures. Maintenance is, by definition, much safer too.
Making diverter and transfer systems safer
There have also been significant advances when it comes to safety in the area of diverter and transfer systems on conveyor lines.
This is an area of application where pneumatic systems had been the preferred choice for many years. However, the use of pneumatic equipment always presents safety challenges given its typically high noise levels, high operating pressures, and the need for air compressors, with serious ramifications should a piece of equipment fail without warning. These issues drove pioneers in this area to design more compact systems which could function effectively without the need for pneumatic power.
Diverter systems were often typically based on a pneumatically-powered arm which must operate with sufficient force to change the direction of a product which is already in motion. The high pneumatic pressure and force in use mean there is the risk of serious injury if this component comes into contact with an operative working on the line. This challenge has in the past been countered with the placement of barriers and grills around the conveyor and diverter, but this again comes at a cost.
However, modern diverter systems are modular and employ a number of small multi-directional wheels which can be programmed to safely divert loads at any angle. This does away with both the need for a fast-moving arm with high torque and for pneumatic power to power it; and the cost, noise, maintenance and safety issues associated with pneumatic power and air compressors are removed at a stroke.
Perhaps even more importantly, the diverter systems themselves are powered by 24V DC power, compared with previous system powered by 400V three-phase power whose installation requires extensive cabling and earthing, alongside specialist, expensive and more regular maintenance typically entailing complete line closure. 24V DC powered systems, however, are much safer given the lower current passing through them, and can simply be swapped in and out when needed, with routine maintenance such as belt or motor replacement able to be undertaken by an in-house operative without the need for specialist external support.
Systems able to handle loads of up to 50kg are now commonplace, but capacities of up to 250kg are shortly to be introduced.
Ensuring product safety
Avoiding shock and collision is critical to minimising damage to boxes and their contents and ensuring they arrive safely at their eventual destination. The key here is to avoid unnecessary contact between individual boxes by ensuring some distance is maintained. This is especially important when boxes are having to travel up or down gradients, and is thrown into focus if power is lost or there is a need for a sudden line stoppage. In this instance, boxes must not collide with each other or fall off the conveyor.
The use of servo-driven magnetic brakes is key here as these systems still work even in the event of a power outage. Meanwhile, if it is necessary to stop the line for another reason, mechanical braking systems can also be used to block the rollers where the product is on an incline or decline, bringing the system to a complete stop.
The safety advantages to operatives offered by electrically-powered diverters extend to the products too – the arms operate at high speed so can pose a risk of damage to boxes and their contents, but wheeled systems by definition do not use arms so not create heavy contact with boxes in this way. Moreover, these systems divert loads off and onto the line without any need to raise or lower the loads, again cutting the risk of damage significantly.
All of these factors should be considered from the very earliest stage of system design, ensuring both people and products come to no harm resulting from the handling process and that goods are reliably and safely conveyed to their eventual destinations.