The majority of containers around the world are packed while attached to a trailer or chassis. This can make getting a verified container weight that complies with the SOLAS VGM requirement a challenge for shippers and their logistics partners. With this in mind, it's time to review the best ways to weigh a container on a chassis.
The most common way of weighing containers on a chassis is by weighbridge. A weighbridge is a large platform scale, typically mounted onto a concrete foundation and is large enough to weigh an entire road vehicle and its contents.
A weighbridge may be situated on the shipper's site, or the trucking company might run the container over an off-site weighbridge that is en-route to a terminal. Installing a weighbridge on-site is expensive. They also take up a lot of space. On the other hand, weighing en-route to the terminal can stack up well financially, although this largely depends on the volume of containers you're weighing and the cost per weigh.
In terms of the accuracy, a weighbridge is high at around 0.2% to 0.5%. If you are using the weighbridge for SOLAS VGMs or to support trading of cargo by weight, you should make sure the weighbridge is certified legal-for-trade. Despite their accuracy, weighbridges are not ideal if you want to weigh 2 x 20' containers on a chassis, or if you want to confirm the container's load distribution.
Weighing a container a weighbridge can also be very quick, assuming there are no queues and the container, truck and chassis can all be weighed in one process. In some regions, it is necessary to weigh in the truck empty (to get an accurate tare weight), and then weigh out with the truck, trailer and container. Removing the container for this purpose can seriously slow down the weighing operation and add to the cost per weigh.
If the weighbridge is off-site, your container shipment may experience delays due to travelling distances to and from the weighbridge, and queues and congestion once you are there. These delays and distances can add costs if you are check weighing on a weighbridge, i.e. from having to return back to the shipper's yard if the container is found to be over or under a target weight.
All up, weighbridges can be a good solution for weighing a container on a chassis, however shippers should not ignore alternatives that might be faster, more accurate, more economic or allow weighing to take place in a better location in the logistics process.
Axle weigh pads are lightweight, portable scales designed for weighing static or in-motion (WIM) vehicles. The weight is transmitted by cable or wirelessly to a central indicator. They are an economic option, quick to install and can be used at multiple sites.
If the truck is weighed in motion, the container weight verification process can take only 2 minutes, although WIM systems tend to be less accurate and may not be certifiable. For more accurate weight verification or certified equipment, the truck can be weighed while stationary, although this weighing process can take around 15 minutes.
Axle weigh pads need a large, flat surface. They also have several limitations that are similar to a weighbridge; they won't confirm load distribution, they can't weigh 2 x 20' containers, and the process can delay haulage operations. In order to get high accuracy, the pads must be recessed into the ground, and the same truck must weigh in and out. Unfortunately, many axle weigh pad systems are not certifiable as legal-for-trade.
To weigh containers sitting on a chassis, a weighing system can be fitted to the truck's suspension system and calibrated to give an indication of the load on the truck. The biggest benefit of this system is that you can weigh at any time and at any location, as long as the container is on the chassis. It is also very quick, being able to generate a container weight within 1 minute.
However, there are downfalls with this system. The accuracy of a trailer suspension weighing system is low, at around 3% - 5%, which is not certifiable. There are also other variables such as the tare weight of the truck and trailer unit, as well as fuel, and calibration of this weighing system, which will affect the accuracy even further.
Trailer suspension systems don't cater for a trailer that is holding more than one container. Also, there is a dedicated truck and trailer combination that have to be paired for the system to work. This is not usually very practical in shipping
BISON C-Legs are the most portable and accurate solution on the market for weighing containers on a chassis. These are an attractive choice to shippers who may have limited room on-site, and for those who don't want to deal with the cost and timing of weighing on a weighbridge, yet still require a highly accurate weight. The C-Legs have an added advantage over a weighbridge, that they allow the shipper to verify the container weight and load distribution on-site immediately after, or even during the container packing process.
BISON C-Legs are OIML certified and Type Approved in Europe, New Zealand and other countries. The system works by attaching one of the four scales to each corner of the container and lifting it just clear of the chassis. The scales then transmit a highly accurate container weight via Bluetooth to a smartphone App. The App is then able to confirm the weight distribution, capture photos and shipment details, and send a weight certificate and related data by email or to your server.
These container scales equip shippers to accurately weigh containers on a chassis in any location, without reliance on more capital-intensive weighbridges, cranes and container handlers, which are not always available at the right time or in the right place. They are a portable and cost-effective solution for shippers, forwarders and other operators who would like to verify container weights simply and easily, at the most convenient time and location.
At BISON, we firmly believe it is smart practice to weigh containers at the pack point. Not only does this conform to the CTU Code's best practice guideline, but it puts the shipper in control of the very serious VGM compliance obligation and avoids potential headaches down the road with overweight, underweight or unbalanced containers. So, out of the four options we have listed for how to weigh a container on a chassis, BISON C-Legs are our pick! You can watch the BISON C-Legs in action here.
Regardless of whether you're weighing a container on the ground or on a chassis, it's vital that you supply a verified gross mass before shipping takes place. To make life easier for you, we've outlined all the weighing options in more depth in one easy e-Book, Container Weighing Options Compared.