With over half a million in the world today and growing annually, ISO tank containers are becoming an increasingly common means of transporting liquids, gases and even powders. In addition to carrying traditional hazardous and non-hazardous goods, ISO tanks also carry a wide range of perishable and non-perishable food and food-grade products including orange juice, wine and even liquid chocolate.
Generally, ISO tanks are weighed to determine the amount of contents inside, or the contents remaining inside them. Weighing is the fastest method to determine the quantity of contents of an ISO tank.
Exporters and shippers also need to weigh ISO tanks to comply with VGM regulations. Like regular containers, ISO tanks require verified gross mass (VGM) declarations before being loaded on ocean-going vessels.
Having an accurate measure of the contents or remaining contents, gives an accurate estimate of the total value of the product. Common users include gas and fuel distributors, chemical producers, or any organisation that needs to deliver ISO tankers to a customer for later retrieval - billing the customer for the amount used.
The weight information is also useful for consumers to determine the quantity of the contents remaining inside the tank container. For expensive products like helium, the accuracy and economics of the weight information are very relevant.
The two most common methods for weighing ISO tank containers is to either weigh a truck with chassis and container on a weighbridge, or to weigh the ISO tank container directly with container scales..
Let’s examine each of these options in more detail.
Weighbridges (also known as truck scales) are a very common method of weighing heavy vehicles and the goods they carry. The weight of the ISO tank container can be calculated by weighing the entire truck, trailer and container on a weighbridge and by deducting the tare weight of the vehicle. Then the weight of the contents can be calculated by deducting the tare weight of the ISO tank.
Provided the weighbridge is well maintained, it is generally an accurate method for measuring a truck’s weight. The main challenge is accurately determining the tare weight of the truck and trailer.
One option is to weigh the truck and trailer without the ISO tank. This requires the ISO tank to be lifted off the trailer with expensive handling equipment, which may not be available.
Another option is to use the declared tare weight of the truck and trailer is used. Unfortunately, in this case, there are various sources of error to consider.
The variation in the truck’s fuel load means that the weight calculation can easily be out by hundreds of kilograms. This is compounded by the accumulation of mud or ice in winter months. The presence or absence of the driver or a passenger, or other equipment can also throw off the readings.
In sum, relying on a declared tare weight can lead to expensive errors.
In some regions weighbridges are scarce, making them uneconomical or expensive to use. The cost of a weighbridge, civil works and installation, and the cost of maintenance can make weighbridges unfeasible at some sites, even if sufficient space is available.
What is the cost of inaccurate weight information? This depends entirely on the value of the contents. In an extreme case, an uncertainty of ±100 kg on the accuracy of a tank container of helium is ±4000 USD of uncertainty on the value. It is obviously worth getting it right.
Weighing ISO tanks on a Weighbridge Pros
Weighing ISO tanks on a Weighbridge Cons
A novel alternative to weighbridges is weighing an ISO tank containers with portable scales known as BISON C-Jacks. As well as providing accurate weight measurements, the C-Jacks can be used at the site where the tank containers are situated, providing immediate information to the producer or consumer. It provides real-time information when filling a tank container, or when consuming the contents, and it allows the quantity of residual contents to be easily determined.
The C-Jacks can be used to weigh ISO tanks on the trailer-chassis, or on the ground.
To weigh tank containers, the C-Jacks scales are used with stands. Four C-Jack scales are fitted to the lugs on the lower corners of the container, and the stands are placed under the scales. The container is then lifted with hydraulic bottle jacks a small height above the trailer-chassis, to bring the full weight of the container to bear on the scales. Finally, the weight is read with either the master display, or a smartphone App.
Weighing tank containers on the ground is even easier. The C-Jack scales are attached to the container in the same fashion, but the hydraulic bottle jacks are placed directly on the ground. The tank container is lifted a few centimetres clear of the ground and weighed. The entire process, including setting up and packing away, takes one person around 5 minutes.
In both cases, the C-Jacks allow tank container to be weighed where it stands, exactly when it needs to be weighed. No waiting, no heavy equipment or transport to weighbridges required. By weighing the ISO tank containers directly on the chassis or on the ground in this manner eliminates the uncertainty from tare weight of the truck and trailer.
Weighing ISO tanks with a Container Scale Pros
Weighing ISO tanks with a Container Scale Cons
Weighing the contents of an ISO tank containers is a must when your business depends on accurate product levels. For organisations with high volumes of containers and where speed and efficiency is more important than accuracy, consider using a weighbridge. However, if you ship high-value product, the accuracy and portability of BISON’s C-Jack container scales make them the clear winner.
BISON C-Jacks are a fast, portable, and highly-accurate complete ISO tank weighing system. C-Jacks give you the power to weigh ISO tanks any time, any place.