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 - with direct repercussions for both cash flow and adherence to legislation - making an effective preventative maintenance programme vital, says John Coughlan of 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 this era of waste management, the weighbridge is like the cash register for an organisation. Landfill charges, waste sorting and recycling transactions and landfill taxes all rely on accurate data.
Indeed, with charges for active waste going to landfill set to increase by 100% over the next three years, is important that we measure or weigh the different categories of waste. Such information is, after all, the basis of many financial transactions in our industry.
Landfill operators need to record the waste's weight in tonnes, the area of origin, the waste disposal authority, the European Waste Code category (EWC), the EWC standard description, any treatment at the landfill, the identification of the waste transfer station (if used) and the date and time of the deposit.
Clearly the weighbridge and its data collection software is at the heart of this reporting regime. It is therefore essential that it remains operational and also reports weight data accurately.
Weighbridge downtime could potentially bring a landfill site or waste transfer station grinding to a halt. Equally, waste collection agencies rely on this information and some may have their own weighbridge facilities to record and manage their biodegradable waste over time.
Consider the environment in which a weighbridge operates, not only is there mud, waste debris and water to contend with, but on a busy landfill site, for instance, a weighbridge may need to weigh more than a hundred heavy goods vehicles a day. Each of these will approach the weighbridge and brake, potentially causing shock loading.
While it is true that such structures are built to cope with these demands, it is wise to take a few simple precautions. After all, prevention is better than cure, but how many people actually put that principle into practice?
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 either 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, both within the load cell and by fitting lightning conductors, but it is important to check the weighbridge for damage after any thunderstorm.
So, assuming you already have a maintenance contract in place and are aware of the most common problems, 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 a year tasks.
These simple tasks are important because an 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. Some sites use traffic calming humps to overcome this potential issue.
For pit-mounted installations check that, if T section rubber is fitted, it is located correctly and check 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 to enable effective cleaning of the area
Weekly tasks involve checking the load cell assemblies for debris build up, which should be removed carefully without damaging the load cell cables.