Unsafe stacking of waste bales can result in them falling and/or stacks collapsing leading to serious injuries. The principles set out in this page are aimed at the stacking of bales of waste material such as paper, plastics, and metals.
Some of the principles may also be relevant to non-baled waste materials that are routinely stacked ‘loosely’ such as tyres.
Stack stability
The type of material being baled, as well as the shape, size, weight and density of bales, will all affect stack stability. Stack configurations and methods of stacking may differ considerably from one bale type to another.
Consider:
- the physical properties of the baled material (for example the size, weight, composition and density of the material and bale), and the effect it might have on the stability of any stack it may form part of, or be located close to
- the effect, over time, that the baled material has (or is likely to have), on the configuration of other bales or stacks, for example if the material is likely to break up or compress further
- when the material is stored outside, if the weather will have an impact on stability, for example due to heavy rain or high winds
- placing and removing material in and around stacks and bale storage areas which may affect their continuing stability, for example the potential of stacks being struck by moving vehicles or from nearby materials being stored unsafely
How to improve stack stability
Stack stability may be improved by:
- positioning stacks on firm level ground, with an adequate drainage slope, typically of about 1.14 degrees
- stacking bales evenly
- using pyramid constructions for stacks of single bales – with a wide base narrowing as it gets higher
- constructing stacks to maximise stability, for example by interlocking bales or by inserting boards between layers to improve rigidity
- alternating layers, so the lower supporting bales are stabilised by overlapping and interlocking upper bales
- inserting lengths of timber at the outer edges of the stack, to give an inward lean on the outer faces
- avoiding stacking single rows too high (though actual heights will depend on material type and solidity of bales)
- surrounding stacks on 3 sides (small zones) then interlocking in the fourth direction
- using forklift truck protectors (where there is a risk of stacks being hit by vehicles)
- leaving gaps between stacks and walls, unless the wall has been built to withstand the force of the stack leaning against it
- providing a safe system of work for the restacking of bales where the existing stack has a sheer or unstable face, following the placing or removal of adjacent material
How bale stacks can become more unstable
The stability of bale stacks may also be affected by:
- water absorption (especially paper and card bales stored outside)
- rusting of wires and straps, if bales are left outside for long periods of time
- poorly produced bales (which should be identified for re-baling and not stacked)
- uneven or rough ground
Reducing other risks
The risk of being struck by falling bale(s), or the collapse or unintended movement of a stack can be reduced by:
- segregating pedestrians, pedestrian routes and foot paths from stacks and storage areas
- routinely checking the condition of stacked bales, especially after periods of adverse weather (if stored outside) or if they have suffered impact damage
- devising a safe system of work for the removal of bales (if one should become damaged or falls)
- where potentially unsafe stacks are identified, putting measures in place to prevent pedestrians from approaching them on foot until they are made safe
- assessing and implementing the use of vehicle protective systems, such as falling object protection systems (FOPS), as a form of protection for operators dismantling unstable stacks or storage areas
Training and instruction
All operators, team leaders and managers involved with the stacking and storage of bales (or who may use the areas where bales are stacked and stored), should receive suitable information, instruction, training and supervision. This should ensure reasonably practicable precautions that have been identified are:
- implemented
- maintained effectively
You can find more guidance on training for the waste industry.