In today’s era of landfill charges and LATs reporting, the weighbridge is at the heart of
a waste organisation’s data collection. Downtime can bring an operation to a halt so an effective preventative maintenance programme is vital says Chris Thorpe, service manager for Avery Weigh-Tronix.
Weighbridges are precision weighing instruments designed to meet stringent weights and measures regulations while operating in extremely harsh environments.
Collecting and reporting waste data is essential for waste disposal authorities, transfer stations and landfill operators. In modern waste management the weighbridge is like a cash register for an organisation. Landfill charges, waste sorting & recycling transactions and landfill taxes all need accurate data.
Indeed, with charges set to increase by 100% over the next three years for active waste going to landfill, it pays to recycle and importantly measure or weigh the different categories of waste. With the weighbridge and its software at the heart of this reporting regime, it is essential that it remains operational and also reports weight data accurately.
Having the right service and maintenance agreement in place is essential, but there is much that weighbridge operators can do to ensure that equipment stays reliable. Perhaps the first thing is to be aware of the most common causes of damage or failure.
For example, if the load cell or weighbar is left in water or even in very damp conditions it can fail prematurely. This is one of the most common causes of inaccurate weighing and leads to rejection by trading standards officers.
Second, “shock loading” can cause excessive movement of the weighbridge platform damaging the structure. This can be due to the heavy braking of a vehicle, impact damage caused by a loading shovel or by heavy loads dropped directly onto the weighbridge or into a vehicle positioned on it.
Another common problem is electrical disruption, including mains borne interference through the weighbridge indicator supply or a lightning strike, either directly or via dissipation when the surrounding ground becomes electrically charged. Modern weighbridge designs generally incorporate protection against lightning, but it is important to check the weighbridge for damage after any thunderstorm.
So, assuming you already have a maintenance contract in place, what else can an operator do to help keep the weighbridge operational and legally compliant?
The answer lies in housekeeping and good practice, with daily, weekly, monthly and twice yearly tasks. These simple tasks are important as accumulation of dirt, debris, water or slurry will affect the integrity of the weighbridge. In the short term this will lead to inaccurate weighing and, if allowed to continue, the load cells or weigh bars will fail, making the weighbridge unusable.
On a daily basis, for example, it is best practice to visually inspect the platform to ensure it is free from debris. Check that the side and end frames are not fouled. Next ensure that the digital display reads zero before the vehicle drives onto the platform.
Make sure that vehicles approach the platform slowly and avoid sudden braking and for an accurate weight reading ensure that all of its wheels are on the weighbridge.
For pit-mounted installations where T section rubber is fitted, check it is located correctly and that any pit drainage system and/or automatic pumps are working correctly. For surface mounted weighbridges make sure there is clearance between the superstructure and the ground .
Weekly tasks involve carefully checking the load cell assemblies for debris build up, which should be removed carefully without damaging the load cell cables.
You should also carry out a weekly weigh check using a loaded vehicle. Compare the vehicle’s weight when it is weighed at each end of the weighbridge and in the centre of the platform. If discrepancies of ± 2 indicated divisions are found then it should be reported.
In the example below, the weight is displayed in 20kg increments. At 25980Kg the weight is acceptable at -1 indicated division, but at 26060kg at the front end of the platform it is unacceptable with +3 indicated divisions.
For a pit-mounted weighbridge, check the pit monthly for possible “ponding” of water, debris build up or other damage to the leading edge of foundations, and the side and end frames of the platform. If the platform has moved excessively since the last inspection, then report it to your maintenance service provider.
You should also repeat the end-middle-end test as detailed in the weekly tasks and record the readings. After doing this jet wash the weighbridge to remove any loose debris and any material beneath the platform, taking care to avoid the load cells or weighbars. Rebalance, or zero, the weighbridge and repeat the end-middle-end test noting the readings. Compare these before and after results and report any discrepancies.
Finally, once every six months you should check the weighbridge for any signs of structural damage. For example, inspect the foundations for any significant movement or cracks and report any signs to your maintenance service provider. For surface mounted weighbridges visually check the load cell cables and again report any damage.
Never electrically weld on the weighbridge structure without consulting your service provider as this can seriously damage your loadcells or weighbars.
Also if the weighbridge needs cleaning out then you must take into account that waste can produce methane and other dangerous gases. For pit mounted weighbridges, you must ensure that suitably certified gas detectors are used in compliance with the Confined Space, Health and Safety legislation, both before and during such work.
With proper care your weighbridge will give longer trouble free operation in between planned maintenance visits. But remember not to get carried away by ‘DIY service’. Do not attempt to carry out detailed repair or maintenance work as this may affect its operation and contravene Weights and Measures regulations.
This is where a planned maintenance contract is essential, taking into account the way a weighbridge is used and its frequency of use, as this will vary from one organisation
to another. Maintenance contracts can be flexible to meet your needs. Avery Weigh Tronix often finds that a basic package is fine for a new weighbridge in its first year, with extra cover added progressively as the equipment ages.
A basic package will typically only include a scheduled preventative maintenance visit or visits – ranging from monthly to annual visits. Additional features can include emergency cover for breakdowns, labour costs for repairs, parts and even replacement of load cells or weighbars.
If replacement parts are fitted, you may need to get the weighbridge re-verified to ensure it meets weights and measures legislation – check whether your service supplier can do this for you as not all service and repair companies have the necessary skills, tools and experience.
To meet your due diligence obligations you should also have your weighbridge calibrated regularly – at least once a year. Again your maintenance service provider should be trained and qualified to offer this service.
If the worst should happen you should also check your contract for response times. Even in the remotest regions of the UK, an eight hour response time is achievable and much shorter response times are available for critical operations.
In summary your weighbridge is one of the most important elements of your business. Without it operating properly, you risk mis-measurement. Even worse, if the problems build up and the weighbridge becomes inoperable it could slow or even close down your operation.
Finally there is the nightmare scenario, of non-compliance with Weights & Measures and the risk of legal action by Trading Standards with all the damage to your reputation, to say nothing of the direct financial losses.
Even though your weighbridge looks a simple, robust, heavy duty piece of kit that can ‘look after itself’, a few minutes spent on basic housekeeping each day, an hour each week and a couple of hours each month, will make all the difference to its reliable, trouble free operation.

A major magnetic equipment manufacturer has successfully solved numerous Aluminium Recycling problems world wide. Master Magnets Ltd is a world leader in the field of Metal Separation applications, they are now willing to share the secrets behind their success.
The recycling of aluminum generally produces significant cost savings over the production of new aluminum even when the cost of collection, separation and recycling are taken into account. Over the long term, even larger national savings are made when the reduction in the capital costs associated with landfills, mines and international shipping of raw aluminium are considered.
The environmental benefits of recycling aluminium are also enormous. Only around 5% of the CO2 is produced during the recycling process compared to producing raw aluminium (and an even smaller percentage when considering the complete cycle of mining and transporting the aluminium).
Also, open-cut mining is most often used for obtaining aluminium ore, which destroys large sections of the world’s natural land.
Recycling Aluminium has been further improved through Master Magnets high performance ‘Eddy Current Separator’. In the late 80’s Master Magnets recognised a need in the market for a machine which can separate Aluminium (Non Ferrous) from other metals and non metallic’s (E.g Iron and Plastics). Therefore Master Magnets launched the Eddy Current Separator into the market place.
Operating Principle
An Eddy Current Separator basically consists of a short belt conveyor with its drive at the return end. Inside the delivery pulley a rotor fitted with magnets spins at high speed generating a high frequency alternating magnetic field. In a similar manner to electric motors the alternating magnetic field sets up an electric current in conducting metals within its influence, which in turn produces a magnetic field opposing that of the rotor. Conducting metals are therefore repelled by the rotor, and tend to jump away from it. In operation non metallics are discharged as from a normal conveyor. Non ferrous metals, because of the repulsive force, take a higher trajectory passing over a splitter plate placed between the two flows.
The separating efficiency depends on the frequency of the alternating magnetic field, the strength of the magnets, the speed of the conveyor and the position of the splitter plate. All of these factors should be taken into account when selecting a machine for a particular application. In order to allow non ferrous metals to be repulsed by the rotor, material on the conveyor should ideally be in a monolayer, so throughput will depend on the density and particle size of the material, and the width and speed of the conveyor.
Applications
Eddy Current Separators are increasingly used wherever separation of non ferrous metals from a product stream can give a more valuable product, whether the end use is in recycling, reduction of waste, raw material production or any other process where separation is beneficial. Typical examples of applications are :-
• Separation of non ferrous metals in auto shredder residue
• Separation of non ferrous metals from solid waste incinerator ash
• Sorting aluminium beverage cans from non metalllics
• Removal of contamination from crushed glass cullet
• Extraction of contaminants from process lines
• Separation of non ferrous dross from foundry sand
• Non ferrous metal removal in WEE recycling plants
• Removal of aluminium components in UPVC window recycling
At the heart of many Material Recycling Facilities (MRF’s) an Eddy Current Separator will remove non ferrous metals from domestic, commercial and industrial waste.
Technology from Master Magnets
Master Magnets ECS designs incorporate the latest generation neodymium-iron-boron rare earth magnetic elements to give the high field strengths necessary for efficient separation. Careful design of the rotor within the outer pulley shell ensures that the product is as close as possible to the magnets, as does the selection of high quality thin section conveyor belts.
Various combinations of rotor size and magnetic design are available depending on the application. The standard rotor functions well on such applications as municipal waste recycling. The ‘Fines’ rotor will treat small particle sizes where high rejecting forces are required, and a special design treats coarse, light material such as beverage cans. All are available in widths from 300mm to 1500mm depending on the throughput required.
Master Magnets’ latest version of the eddy current separator is lower in cost and specifically designed for can sorting.
Master Magnets can supply a complete solution to a non ferrous separation problem, from laboratory sample testing to design and installation of a complete separation plant. After careful consideration of the operational requirements the plant will be designed to give a long and trouble free life, and to produce separated materials to the customer’s specification. In house experience will be drawn on to ensure that hoppers, feeders, conveyors, magnetic separators, and all other parts of the plant are compatible, and together function efficiently.
For more info, call 0844 560 7706 and quote ‘Recycling Aluminium TS35’.