Method for reinforcing a tank wall

Abstract

 The invention relates to a method for reinforcing a tank wall, which method comprises the steps of:

• providing a tank with a steel tank wall defining an interior space;
• providing a reinforcing pressure in said interior space, which reinforcing pressure exceeds the ambient pressure on the outside of the tank wall,
     wherein the reinforcing pressure is such that the tension in at least a part of the tank wall exceeds the 0.2% yield point; and
• removing the reinforcing pressure.

Description

[0001] The invention relates to a method for reinforcing a tank wall.

[0002] Tanks used for the storage of liquids have to be strong enough to resist the static pressure of the liquid. In order to minimize use of material, like steel, conventional tanks are manufactured such that the thickness of the tank wall is harmonized with the static pressure. With a vertical tank it means that the thickness of the tank wall decreases in upward direction.

[0003] Tanks, which are used in the food industry, are generally made of stainless steel. In comparison with conventional steel the price of stainless steel is very high. Each decrease of use of stainless steel is welcomed as this results in lower manufacturing costs and provides a more competing product.

[0004] A decrease of stainless steel will also result in a lower mass of the tank, which allows lighter support constructions.

[0005] It is an object of the present invention to alleviate the above mentioned drawbacks.

[0006] According to the invention, this object is reached by a method comprising the steps of:

• providing a tank with a steel tank wall defining an interior space;
• providing a reinforcing pressure in said interior space, which reinforcing pressure exceeds the ambient pressure on the outside of the tank wall,

   wherein the reinforcing pressure is such that the tension in at least a part of the tank wall exceeds the 0.2 % yield point; and

• removing the reinforcing pressure.

[0007] When a steel plate is stretched by a tensile force, wherein the tension exceeds the 0.2 % yield point, the strength of the steel plate will increase. As a result less material is needed to build a tank with the same strength as a conventional tank.

[0008] Stretched plates with increased strength can be used to build a tank, but these stretched plates have a higher price than the normal plates and welding of these stretched plates will deteriorate the plate properties, especially the strength.

[0009] In a preferred embodiment of the method according to the invention the method comprises the step of filling the interior space with a liquid, e.g. water, for providing the reinforcing pressure.

[0010] A gas can be used to bring the tank to a desired pressure, however when something goes wrong, for example a weld ruptures, the pressurized gas will explode and cause a lot of damage. As a liquid, such as water, is less compressible, the explosion danger will be negligible.

[0011] In a preferred embodiment the tank wall comprises stainless steel.

[0012] In yet another preferred embodiment of the invention, the tank wall comprises a support wall and a plate arranged on to said support wall by a closed weld contour, which weld contour, support wall and plate define a channel for circulation of a heat transfer medium, said method comprising the step of providing a pressure in said channel, such that the plate is subjected to plastic deformation.

[0013] The plastic deformation can be preformed before the reinforcing pressure is provided, but it is preferably provided after the reinforcing pressure.

[0014] Tanks, which are especially used in the food industry, are preferably cooled. By providing a plate onto the support wall of the tank, which plate will be plastically deformed, a channel is created, through which a heat transfer medium can circulate, in order to cool the tank wall. When the channels are already provided before the reinforcing pressure is applied onto the interior of the tank, the welds between the plate and the support plate can tear, as a result of the elongation of the support plate.

[0015] The invention further comprises a tank for liquid foodstuff, comprising:

• a cylindrical steel tank wall;
• a substantially spherical top plate, arranged on one side of the tank wall; and
• a bottom plate, arranged on the tank wall oppositely of the top plate;

   wherein at least part of the tank wall is reinforced according to the method of the invention.

[0016] At least one of the tank wall, the top plate and the bottom plate comprises preferably stainless steel. Furthermore, the tank can comprise a plate, which is arranged on at least the tank wall by a closed weld contour, which weld contour, tank wall and plate define a channel for circulation of a heat transfer medium, and wherein the plate is plastically deformed.

[0017] The bottom plate can be substantially conical of substantially spherical.

[0018] These and other objects and features of the invention will be explained in conjunction with the drawings.

[0019] Figure 1 shows a perspective view of a first embodiment.

[0020] Figure 2 shows a perspective view of a second embodiment before plastically deforming the plate.

[0021] Figure 3 shows a perspective view of a second embodiment after plastically deforming the plate.

[0022] Figure 1 shows a tank 1 according to the present invention. The tank 1 comprises a cylindrical tank wall 2 on top of which an substantially spherical top plate 3 is arranged. On the opposite side of the tank wall 2 a conical bottom plate 4 is arranged. This conical bottom plate comprises an outlet 5 for filling or emptying of the tank 1.

[0023] The tank 1 is kept in an upright position by a support structure 6.

[0024] Figures 2 and 3 show a tank 1, on which outside a plate 7 is arranged, which is welded to the tank wall 2 by a closed contour weld 8. Furthermore, circular welds 9 are used to attach the plate 7 to the tank wall 2. The plate 7 is arranged with an inlet 10 and an outlet 11.

[0025] After reinforcing the tank wall 2, the inner space, defined by tank wall 2, plate 7 and closed contour weld 8 is pressurized by a fluid, such that the plate 7 plastically deforms and provides a pillow-like plate 7 (See figure 3).

[0026] Through the inlet 10 and outlet 11 a coolant can be circulated through the inner space, which is defined by the tank wall 2 and the plate 7.

Claims

1. Method for reinforcing a tank wall, which method comprises the steps of:

- providing a tank with a steel tank wall defining an interior space;

- providing a reinforcing pressure in said interior space, which reinforcing pressure exceeds the ambient pressure on the outside of the tank wall,

   wherein the reinforcing pressure is such that the tension in at least a part of the tank wall exceeds the 0.2% yield point; and

- removing the reinforcing pressure.

2. Method according to claim 1, comprising the step of filling the interior space with a liquid, e.g. water, for providing the reinforcing pressure.

3. Method according to claim 1 or 2, wherein the tank wall comprises stainless steel.

4. Method according to one of the preceding claims,
   wherein the tank wall comprises a support wall and a plate arranged onto said support wall by a closed weld contour, which weld contour, support wall and plate define a channel for circulation of a heat transfer medium, said method comprising the step of providing a pressure in said channel, such that the plate is subjected to plastic deformation.

5. Method according claim 4, wherein the plastic deformation is performed after the reinforcing pressure is provided.

6. Tank for liquid foodstuff comprising:

- a cylindrical steel tank wall

- a substantially spherical top plate, arranged on one side of the tank wall; and

- a bottom plate, arranged on the tank wall oppositely of the top plate;

   wherein at least part of the tank wall is reinforced according to claim 1.

7. Tank according to claim 6, wherein at least one of the tank wall, the top plate and the bottom plate comprises stainless steel.

8. Tank according claim 6 or 7,
   wherein a plate is arranged on at least the tank wall by a closed weld contour, which weld contour, tank wall and plate define a channel for circulation of a heat transfer medium, and wherein the plate is plastically deformed.

9. Tank according one of the claims 6 - 8, wherein the bottom plate is substantially conical or substantially spherical.

Drawing