• Exciting promises in experimental tankers
Page 54
Page 55
If you've noticed an error in this article please click here to report it so we can fix it.
A small Swedish design firm has come up with a range of lightweight tankers that can carry dangerous goods. The payload advantage is considerable. Hans Stromberg, of our Swedish sister magazine Lastbilen, has been looking at the work of this innovative company
TANKS and containers for carrying or storing dangerous liquids can be built lighter and safer than with other present methods of construction, says Lars Gunnar Oberg, owner of Dynatrans, a small design company in the Swedish town of Gothenburg.
The method he proposes is based on one of his own designs, an insulated tank made of two layers of steel sheet with a load-carrying layer of cellular vinyl plastic in between, the plastic being bonded to the metal.
This type of design is at present used in tanks for other liquids, usually foodstuffs such as milk and orange juice.
Even cocoa, butter and tallow are transported in these containers, which can be equipped with heating or cooling apparatus and agitation to keep an even temperature throughout the liquid.
Lars Gunnar Oberg worked for a Swedish oil company for several years. He also worked for Volvo, in Sweden as well as in the UK. In 1977 he started his
own company, Dynatrans. His business concept is to design transport systems for bulk products. This means tanks, containers, handling equipment and ancillary equipment such as pumps and metering units.
Dynatrans is a small, hightechnology company. Five people do the design work, whereas the actual building is done by other companies.
The product range is large and varied. For the Swedish market, Dynatrans has designed a system for motor gas distribution by rail and road.
Several oil companies have started to build up distribution and sales channels for vehicle fuel.
The Dynatrans system consists of tanks for liquid gas, built on 40ft container frames. The tanks are filled in Gothenburg on the Swedish west coast. They are transported by rail to suitable terminals where they are collected by lorries. When loaded on to the road vehicles, pumps and metering units are mounted on the tanks, which are emptied at the derv/petrol stations. The empty units are then returned to their point of origin. This system does away with the
need for storage facilities all around the country.
A similar Dynatrans system is used in Brazil, where Dynatrans do Brezil, and a wholly owned subsidiary, and Brazilian interests have a joint company, Congas. This company produces self-service units for sale of motor alcohol, which is a widely used motor fuel in Brazil.
The fuelling units are self-con
tamed and built into containers in a factory. They are transported to the locations, which more often than not are situated in remote areas of the country. This concept is based on a system for self-service petrol stations which was started in Sweden by an oil company several years ago. Lars Gunnar Oberg was responsible for the Swedish system before he started his own business.
Dynatrans designs transport solutions and has not become specialised in any particular genre. What matters is neither the material that is transported nor which company does the transporting nor for whom.
"Our customers can be found anywhere within the industry handling material in bulk," says Lars Gunner Oberg. And the list of customers is long: Shell and Gulf, shipping companies, freight terminals, stevedores, breweries, the Swedish monopoly for sales of wines and spirits, etc. Basically, the only common factor among the customers is that they handle bulk goods.
Sometimes the customer has problems that are rather specialised. One customer wanted to transport dangerous goods from one point to another. The return load was to consist of food. The problem was solved, and the same vehicle is used for transport in both directions. A trailer was built with three tanks, two for food and the middle tank for dangerous goods, says Lars Gunnar Oberg.
The tank for dangerous goods was made in the traditional way, but the tanks for food transport were made in the new, metal and plastic material, which has proved to be a breakthrough for Dynatrans.
When designing a tank for milk or other foodstuffs, the traditional method is to use a 3-4 millimetres thick steel sheet. This means that the tare weight is around 3.5 tonnes. "Our method, with two one-millimetre layers of steel with a core of load-carrying insulation reduces the tare weight to 1.5 tonnes and means that the useful load increases by two tonnes for the same kerb weight," says Lars.
This method was first tested a couple of years ago for milk coi !acting vehicles in Sweden, and it has now got its international breakthrough.
Recently Dynatrans got an order for 100 milk containers from Switzerland, the containers being transportable by road and rail. During the transport these containers are kept cool by normal cooling units.
"We can build tanks with thicker layers of insulation, but we have opted for a compromise, in which a certain degree of cooling is needed," he said. "By going the middle road we can keep the useful load up and get a better economy."
This philosophy, but inverted, is applied to some other very special transport solutions designed by Dynatrans.
Tallow is transported all along the Swedish coast, from the north to southern Sweden in in sulated containers. The problem is, that unless the temperature is around 60°C the tallow solidifies and the container cannot be emptied. "A heating unit with agitation did the trick, but we had to do quite a bit of research before we had a practical design," he said.
Lars Gunnar Oberg explains that the sandwich of steel and plastic is superior to traditional methods of insulation. Since there are no metal parts connecting the inner and outer shells, the insulation is unbroken which makes it more efficient.
The vinyl plastic is also superior to the polyurethane foam hitherto used. It is a more efficient insulation material and it retains its capacity for many years. In fact, it outlasts the vehicle by a healthy margin.
Vibrations and moisture do not affect the material, whereas the traditionally used polyurethane is reduced to powder after a couple of years.
The Swedish navy has tested vinyl foam insulation in its submarines and also in commando landing craft, vessels which have to withstand rough handling to a degree unknown to civilian road vehicles. "It costs more, but we think it is worth the higher price," says Lars Gunnar Oberg.
The qualities of this material got Dynatrans to turn its interest to the design of tanks for dangerous goods. Lars Gunnar Oberg says that, from an engineering point of view, there is
one fundamental fault built into
every single tank trailer.
Traditionally, tanks are built from thick high-tensile steel, in order to survive accidents. But then the kingpin and the wheel assembly are welded on to the tank, to the outer and inner shells. Welding reduces the strength of the material, increasing the risk for the tank to be ripped open at one of the welding seams in an accident Lars Gunnar Oberg has a solution:
"The inner shell should not be weakened by welding. If it is not, it stands a better chance of surviving a crash intact. With a double-walled tank, designed along. the same lines as our lightweight tanks, with a load-carrying core between the two layers of steel, the loads from the kingpin and wheel assembly are taken up by the outer shell only. If that shell is ripped open it does not really matter, because the insulating load-carrying core and the inner shell will survive intact more often than not, and that is basically the idea behind the special rules that govern the design of this kind of tank."
So far the Dynatrans method cannot be used for this type of tank, according to the rules and regulations in most countries, but rules are surely not there to stop development, so there seems to be a fair chance for Dynatrans to get into that market with its new ideas.
If, and when, that day comes, this small, highly innovative company will be ready. It has taken the step into the world market with its other designs, not only in European and South America but also on other continents.