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Bridge that gap

The National Measurements Office (NMO) found that more than 25% of UK weighbridges were outside of their legally allowable tolerances. As a result, the year ahead will see the NMO focus its efforts and increase inspections in this area. 

“The only way to ensure that your weighbridge is inspection-ready and operating efficiently for your business, is to ensure regular housekeeping, supplemented with an effective preventative maintenance and calibration contract,” says Avery Weigh-Tronix product manager service Mo Bott.

These inaccurate weighbridges end up charging customers incorrectly, increasing the likelihood of fines and potentially losing revenue for the business. Ultimately, the weighbridge could be shut down by trading standards. This would have detrimental effects on the company’s ability to operate, seriously affecting profitability and reputation.

Such a significant statistic means that the NMO will be conscious of weighbridge inaccuracy and will be focussing its inspections accordingly. The latest NMO report sets out a risk matrix that places weighbridges in the ‘very likely’ bracket for potential failure and as having ‘very high’ impact of risk.

The current economic times have seen companies looking to save cost, sometimes changing their service provider to cheaper alternatives. But this can be counterproductive if the new provider is not fully competent in this area of expertise, neither having the qualified staff (Approved Verification Officers) or the correct training and tools for maintenance and equipment calibration.

It may be tempting to cut costs by reducing the service cover on equipment, downgrading service supplier or even risking a period without cover.  However, these measures would be a false economy should a company be fined or shutdown. Equally, an organisation could be charging customers unfairly or losing substantial revenue depending on the direction that the weighbridge is inaccurately weighing.

In the industry, accuracy is important and a service and maintenance contract ensures this. Service contracts can incorporate a calibration test conducted by an engineer, to confirm correct readings. Once a calibration inspection is complete, companies are issued with a calibration certificate.  Having a provider carry out regular examination gives peace of mind when trading, as well as during an inspection. 

It is best to work alongside a provider to devise a bespoke service package. The type and frequency of a contract will be dependent upon a range of factors, including how the equipment is used, frequency of use, the age of the equipment and the harshness of the operating environment.

Having the right service and maintenance contract in place is essential to ensure reliability of equipment. However, it’s also important to ensure that your company undertakes good housekeeping with daily, weekly, monthly and twice yearly tasks and checks.

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 and 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.

Once a week check the load cell assemblies for debris build up, which should be removed carefully without damaging the load cell cables. A weigh check using a loaded vehicle should also be carried out each week. 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.

EXAMPLE DIAGRAM

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.

Each month 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. 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 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.

Having accurate weight data is important to a company’s operations. If the weighbridge data is incorrect in the first instance, there will be a domino effect throughout the whole organisation.  For example, reliable information is needed in order to collect landfill charges, create invoices for goods purchased and make informed changes and efficiency savings.

“Take heed of the NMO report, and ensure that your weighbridge is inspection-ready as well as operating efficiently for your business,” Bott adds. “Make sure that your company has a clear weighbridge housekeeping regime in place as well as a reliable service contract provider.”

Case study - Cory Environmental

Cory Environmental, which has a maintenance and calibration contract with Avery Weigh-Tronix, says it has not had any downtime due to an out-of-calibration weighbridge in five years across its 14 sites. The company manages in excess of 3.5m tonnes of waste and recyclables each year. At its Walsall facility alone, an average of 250 Heavy Goods Vehicles pass over the site’s two weighbridges on a daily basis.

The maintenance and calibration contract with Avery Weigh-Tronix includes one calibration and two plant maintenance visits a year and calibration certificates are available online. The contract also includes 24 hour support and Avery aims to respond to emergency call outs within eight hours.

“Having accurate weighing data is important to the operation of our business,” says Cory Environmental director of resource management Alistair Holl. “Firstly it enables us to legally charge by weight and it also means that we can conduct statistical analysis on these figures. None of this would be worthwhile if the weighbridge was not calibrated correctly in the first place. Having an out of tolerance scale would make everything we do with the data thereafter meaningless.”

“Having an accurate weighbridge is the first step in keeping our business honest, accurate and profitable.”

 Chris McAllister is product manager at Avery Weigh-Tronix

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