This invention relates to a container for storage or transport of liquids, with the aim of maintaining the temperature of the liquid as constant as possible by means of insulation, the container insulation being disposed within the container and fastened to the walls of the container.

The insulation consists of wood blocks placed closely together and fastened to the inner wall of the container. The next layer of wood blocks are disposed closely adjacent each other and fastened to the preceding layer, and/or at right angles to the preceding layer so as to achieve maximal density of the insulation. The number of wooden layers is determined by the thickness of the timber and of the insulation power desired for the container.

In previously known insulated containers, the insulating material is disposed on the outer side of the container. There are a number of cases where cargo tanks of ships have been provided with insulation on the inner side, however, in thoses cases, the insulation has been made of glass building blocks, or as an alternative, the insulation material has been shielded by an inner tank made of thinner sheet metal in order to protect the insulating material from direct contact with the liquid/oil stored in the container. Insulation provided on the outer side of a ship cargo tank is a costly solution, requiring freely placed tanks and/or an empty air space around the insulated tanks. Currently known bitumen or oil tanks provided with glass block insulation on the inner side or with insulation material shielded by a thin inner tank require an extremely costly manufacturing method, in addition to precious materials.

Previously known solutions comprising wood insulation materials disposed within the container have been disclosed by relatively old patent specifications, such as e.g. GB 800,008, GB 921,696, US 2,859,895, US 3,026,577 and US 3,030,669. GB patent specification 800,008 recommends balsa wood, which is a lightweight kind of timber whose insulating coefficient is fairly good.

The present invention has the purpose of providing a container insulation that is light, durable, straighforward and inexpensive and whose insulation power is equal, or even superior to that of containers provided with thick insulation materials on the outer side. The container in accordance with the invention is characterised by an insulation made of thermally treated timber with a high insulation coefficient and good dimensional stability. The timber may consist of quite ordinary Finnish softwood, such as spruce or pine. Various embodiments of the invention are described in the dependent claims of the set of claims. The invention yields the following benefits: thermally treated timber

- has an insulation coefficient by approx. 25% higher than that of commonly known usual timber. This results in a low temperature maintained on the outer side of the container.

Does not vary under alterations of temperature and moisture

- Does not absorb liquids

Has a service life much longer than that of untreated timber

- Is not exposed to fire hazards since placed within the container - Is harmless to the environment and easily replaceable, consequently will not form hazardous waste

- Is chemically resistant and stands hot liquids and gases

- Increases the strength of the inside of the container.

Disposing the insulation on the inner side of the container is a better solution for technical considerations of space as well. It enables thicker insulation to be readily provided e.g. in the upper parts and in the lid of the container, where heat tends to escape. In ships, ballast tanks in contact with containers insulated in accordance with the invention are not exposed to heat or condensation damage, since a low temperature is maintained outside the container.

The invention is described below with the aid of a number of examples and with reference to the accompanying drawings, in which:

Figure 1 illustrates a container wall viewed in partial section from within the container.

Figure 2 illustrates an enlarged section II-II of figure 1.

Figure 3 is a cross-sectional view of a ship provided with an insulated container surrounded by ballast tanks.

Figure 4 illustrates an insulated pressure vessel. Figure 5 illustrates a rock container.

Figure 6 illustrates an insulation comprising two layers of thermally treated timber and figure 7 illustrates an embodiment in which the second thermally treated timber layer has been replaced with cellular plastic, such as polyurethane.

The purpose of the container may be storage or transport of liquids, with the aim to maintain the temperature of the liquid on a level as constant as possibleby means of insulation. The insulation 2, 2a, 2b of the container is situated within the container and fastened 3 to the walls 1 of the container. The insulation 2, 2a, 2b consists of thermally treated timber, whose insulation coefficient is high and dimensional stability is good. The container may be a transportable container or an oil cistern. It may also be a ballast tank 5 in a ship. The container may be a pressure vessel (figure 4) allowing storage of a liquid, such as water, under high pressure, e.g. 15 - 25 bars, and at a temperature e.g. in the range 170 - 200°C, and applicable as an energy source for a turbine or a steam engine. The container may consists of a cavity in the soil, such as a container cavity excavated by blasting in the rock (figure 5). Insulation of a second, lighter material, such as cellular plastic 4, e.g. polyurethane, polystyrene or the like, may be provided between the timber insulation 2 and the container wall 1.

Calculations and empirical tests have proved that, say, the transport of heavy oil at a temperature of 60°C consumes 4 to 10 tons of oil per day for heating of the oil, depending on the tank volume. When a container in accordance with the invention is used, the consumption is cut to 0.4 to 0.5 tons of oil per day. A substantial economy is thus achieved.

Thus, the insulation coefficient of a cargo container or any other similar container insulated in accordance with the invention will be high enough even for profitable transport of heat energy from the cooling water of a nuclear power plant to adequate sites for energy recovery, such as district heating, for instance. At present, the heat energy of cooling water is conducted off-shore.

An insulation disposed within the container makes it very easy to measure the surface temperature on the outside of the receptacle, tank or cargo container and thus to calculate the loss of heat, and if necessary , to provide supplementary insulation where desired.