There is a growing trend towards automated, driver-operated weighbridges, as they provide optimal flexibility, efficiency, and extended operating hours.
Weighbridges provide highly accurate and precise weight data, enabling operators to keep a closer track of inventory, obtain precise measurements of incoming and outgoing materials to ensure payload accuracy, and minimise onsite wastage.
Importantly, they provide legal-for-trade weight readings that can be recorded for legislative purposes and other reporting requirements.
Modern weighbridge systems can be engineered to suit the specific requirements of any mine site or industrial operation. Built for harsh environments, they can be installed at ground level, above ground or in-ground, in a range of sizes and configurations.
Most are also customisable with various accessories for different situations, such as boom gates, remote displays, and traffic control lights.
Newly developed weighbridge solutions incorporate digital technologies such as cloud storage, artificial intelligence, and surveillance equipment to combat corruption and illicit trading.
Models with integrated surveillance capabilities are particularly valuable for overseas mine sites operating in regions where security risks are higher than those typically encountered in Australia.
ENHANCED ENGINEERING AND MAINTENANCE FOR RELIABLE ASSETS
Using data analytics to detect trucks with cloned licence plates or swapped trailers, the weighbridge automatically sends measured weights and tonnages to a cloud platform, which can alert the supply chain to discrepancies in loads received.
The same cameras can also identify trucks attempting to bypass the weighbridge and alert site security.
Regular inspection and servicing of a weighbridge’s mechanical and electrical components, as part of a preventative maintenance program, is the most effective way to minimise the risk of breakdowns and costly downtime.
Moisture is one of the most common causes of weighbridge failure, as it can breach the seals of the electronic weighing system and damage load-cell connections, undermining their ability to sense force and record accurate weights.
A weighbridge’s load cells are highly sensitive and their accuracy can be compromised by shock, overloading, lightning strikes, mishandling, vibration, earth tremors, electrical surges or chemical damage.
Other common causes of breakdowns include the build-up of debris and dust, cable failure, damage to the junction box, driving too fast, and mechanical failure.
The design of weighbridges can be split into two core design concepts – pit-mounted and surface-mounted – and can vary greatly depending on the size of the feedlot, expected vehicle types and its vehicle access, weighbridge location, potentially hazardous materials being handled, and other site-specific factors.
Surface bridges are easier to relocate and ideal for temporary sites, and their engineering costs are typically lower, but they use access ramps that can impede traffic flow.
Pit designs, on the other hand, have a level gradient on the approach and exit surfaces.
The two designs can also be combined into a hybrid structure, where the bridge is installed without pit sides to allow open drainage and easy visual inspection, while the approach and exit roads remain level.
Once the choice between an above-ground/semi-pit or fully in-ground weighbridge is made, the next critical decision is the deck type (steel or steel-and-concrete) and the deck length (single or multiple decks).
The type of deck chosen can be crucial, as both types have several advantages and disadvantages.
Concrete and steel decks have long-lasting surfaces, less heat expansion, more confidence in structural integrity, and a heavy structure that resists severe deck movements.
On the other hand, they have a longer installation process, are more difficult to relocate, and are generally more expensive.
Steel-only decks also have long-lasting surfaces, but are faster and easier to install, easier to locate, and generally a less expensive option.
However, the quantity of steel used must be questioned, as it is difficult to ascertain how much structural steel is used (generally, the lower the price, the less steel is used).
A lighter steel structure can create greater movement on the load cells, potentially shortening the lifespan of other weighing components. Steel-only decks also expand more in heat than steel-concrete decks, requiring a larger buffer gap.
Operators should consider five critical design and operational issues prior to purchasing a weighbridge: the number of weighbridges and their installation location, their design and build, the key measurement-chain components (load-cells and instrumentation), integration of peripheral control equipment, and software functionality and integration.
The siting and orientation of weighbridges should account for expected traffic volumes. At higher-throughput operations, this may include dedicated inbound and outbound bridges, or even multiple inbound bridges to prevent bottlenecks.
Another solution for two-way traffic in space-constrained sites is bidirectional weighbridges, where key instrumentation and control features are mirrored at each end.
This has several benefits, including flexibility during busy periods and low impacts on site efficiency when removed for maintenance.
INNOVATIVE DESIGN IN HIGH-RISK ENVIRONMENTS
An example of innovative weighbridge design is the one installed by NWI Group for Clean Energy Fuels Australia (CEFA), which needed a new explosion-proof (Ex-rated) weighbridge solution for its LNG loading operations.
The weighbridge had several unique requirements, including the ability to handle the specific axle groups used by CEFA’s transport trucks to ensure precise weight measurement, while also delivering the necessary robustness and accuracy.
Handling LNG is a high-risk activity, as the natural gas liquefies at extremely low temperatures of about 162 degrees Celsius below zero, necessitating specialised equipment to ensure safety.
The weighbridge also needed a sophisticated display system that could show individual axle weights and the total weight on a single pole.
The solution was a 54-metre full-steel weighbridge, divided into seven independent decks to enable precise axle-group weighing and built with an explosion-proof design suitable for the harsh conditions of LNG handling environments.
This configuration allowed CEFA to monitor and control weight distribution across each vehicle, which is critical for safety and operational efficiency.
Eight display screens were installed on a single pole, one for each of the seven decks, with an additional screen displaying the total weight.
The outcome was a customised solution with a unique design that enhanced accuracy through segmented decks, improved efficiency with real-time weight data and quick assessment, provided data integration with CEFA’s logistics software, and future-proofed CEFA’s evolving logistics demands.