Unipartners

WRITTEN BY THIJS GHERING

It is not unlikely that you, the reader, has at least once seen a container that is used for shipping products across the world with a cargo ship or train. Chances are that this would have been a so-called 20ftcontainer, as this is the most used variant worldwide. However, there is another type of container that is used extensively around the globe, the tank container. In 2019, a total of 604,700 tank containers were used worldwide, which is a 10.8% increase compared to 2018. This significant growth is one of several reasons that constant innovation is key in the competitive world of bulk transport.

Because that is what tank containers are mostly used for, bulk transport. The transportation of all the (semi)-raw materials you can think of, like oil, corn, chalk, cacao, chocolate, flour, milk, rice and many, many more. It is important to mention that every time such a container is to be filled with product, the truck driver has to climb on top of the container in order to open the manhole covers. And it is exactly this action that, in the twentyfirst century, could be automated to increase the safety of the truck drivers and the efficiency of the loading operation. At least that is what they thought at Van Den Bosch, a top-10 European bulk transport company that leads through constant innovation.

Van den Bosch

Ever since it was founded in 1964, Van den Bosch has been driven by the will to do things differently. To challenge everything that is standard, traditional, and customary. Among other things, they innovate with the ground-level controlled manhole cover. “These kinds of innovations fuel our business and enable us to positively change supply chains. Because of that we see ourselves as the Supply Changer in Bulk.”As mentioned, the goal of Van Den Bosch was to come up with a manhole cover that can be opened and closed by the truck driver without having to climb on top of the tank container. At the start of this project,

Van Den Bosch was already in a first stage collaboration with a possible manufacturer. Unfortunately, there was no technical data at this initial stage, so everything had to be started from scratch. The research focused on the design of the cover, the costs of production and materials, and on meeting the requirements set by Van Den Bosch. The two most significant requirements by Van Den Bosch were that the cover should be able to withstand an internal pressure of 4 bar and it should be operated pneumatically instead of hydraulically due to food transport regulations.

Design

The most crucial part of the automated cover design is, of course, the cover itself. The cover, which is made of aluminum for weight reduction, pivots around the base structure. This base structure is designed such that it can easily be mounted to the original tank container without any additional modifications. The rotation of the cover on and off the manhole is actuated and can be controlled by a terminal at the bottom of the tank container. The power needed to actuate the cover is provided by the truck itself. Once the cover is rotated exactly above the manhole, it should also be closed tightly with at least 4 bar as required by Van Den Bosch. In order to do this, a special seal is used, which is explained in the next paragraph.

Figure 1: Original manhole cover design

Seal

The manhole cover is equipped with a seal that can close the cover airtight. In order to withstand the 4 bar internal pressure of the tank, the cover should be pressed on the tank with a pressure higher than 4 bar. In that case, the cover will remain closed due to the greater force acting on the cover from the outside. Several methods were tested to close the lid with sufficient force. The initial method, putting pressure on the lid with a spring-loaded mechanism, was disregarded as it took too much additional moving parts to operate it from ground level. It turned out that the best method yielded a seal that would inflate and seal the lid in all directions as it expanded. The principle of this seal is visualized by the figure below.

Cost analysis

When all necessary parts are known and detailed CAD-designs are available, the total production cost per unit can be assessed. In order to estimate these costs, multiple manufacturers and suppliers are consulted for every required part. The two most valuable components are the machined aluminum cover and the inflatable seal. All the actuators that are necessary for operation also contribute significantly to the total cost. Remaining costs are for wearing friction parts, additional assembly accessories and the rotational hinge. The estimated cost per automated cover is calculated for orders of at least 20 pieces. Exact prices can unfortunately not be given in this article due to confidentiality agreements.

Figure 2: Inflatable seal

Further research

With this analysis, a feasibility research on the automated lid is completed and presented to Van Den Bosch. Consequently, Van Den Bosch has new insights regarding one of many innovations that could potentially be beneficial for the transport industry in the future. The specific investigation with respect to the construction, materials and costs involved allows the company to request the right activities from the actual manufacturer of the lid. Additional advice is given in an elaborate report that consists of possible design alterations for reduced costs, models for in-house production of the automated lid and a discussion on possible complications when used on different types of tank containers. These points of optimization are not considered in the feasibility study as they require extensive research that was not accounted for in the project specification.