A significant part of the world’s freight travels via container ships. These vessels are constructed to optimize the use of space onboard and containers are stowed in an increasingly sophisticated fashion.

Vessel capacity is measured in TEUs (Twenty-feet Equivalent Units) – a system that indicates how many 20-foot containers a ship can carry. Nowadays, most containers are twice as large requiring the FEU (Forty-feet Equivalent Units) system. The first container ships date back to the 1950s and loaded fifty containers. Today, ships carry thousands of containers.

Small vessels (less than 1000 TEU’s) are used primarily to traffic smaller ports; larger vessels are used for longer journeys.

Emma Maersk is the world’s largest container ship with a capacity of 14,000 TEUs. Even larger vessels will likely emerge in the future. The trend is therefore towards larger and larger container ships in order to reduce transport costs per unit transported. The flow of containers between continents and between countries is enormous. At any point in time, there are 5 – 6 million containers on the road or at sea. Every year, 300 million containers are unloaded from ships. Twenty percent of the containers carry food.

Sooner or later, the container must be cleaned and the use of water and various chemicals can be significant. In some parts of the world, water may be in short supply. And the use of chemicals can have adverse effects on the environment and health. In hot countries, the temperature inside the container can become very high. In combination with chemical cleaners and disinfectants, the job of cleaning a container becomes one with many risks.

Cleaning (blasting) with dry ice

Kerstin and George Eriksson began using dry ice blasting about five years ago.

“The method had been in Sweden since the 1940s but for various reasons it was only used for special applications,” says Kerstin Eriksson at IBC Robotics. “We realized early on that dry-ice-blasting offered advantages from an environmental and safety standpoint. Water and chemical usage is minimized.”

“We started working manually cleaning everything from industrial frying pans to railway wagons. Dry ice blasting worked great but it was physically demanding. Then I saw an industrial robot in action and thought that this should be able to work for us. I contacted the Royal Institute of Technology, scientists at the Robot Valley and Mälardalen University. We started from an ABB robot that researchers and developers modified into a prototype for testing. Now delegations from ports around the world visit the Combi Terminal in Eskilstuna to see how it all works.”

Dry cleaning method

So here is how the robot works: The robot, dry ice and other peripherals are stored in a container of the same size as a traditional container. The equipment is docked to the container to be cleaned and the robot is introduced via a beam on wheels. Inside the container, the robot moves around and sprays dry ice pellets on all surfaces. When dry ice hits the surface a “micro-explosions” occurs releasing the impurities.

Using dry ice (see box) for cleaning is a completely dry and clean method. The only thing that remains after treatment is the dirt that is sandblasted away from the container walls. The dirt is sucked up by vacuum cleaner underneath the robot.

In traditional cleaning with water and detergent, a separation process occurs in which dirt and water are separated, and then time is required for the water in the container to evaporate. This is avoided when using a robot and dry ice.

IBC Robotics’ robotic cleaner is patented in Sweden and other European countries. A worldwide patent application is pending.

The article was published in November 2011