GB2071747A - Storage tank - Google Patents

Abstract

A storage tank (1) for installation adjacent to a building (3) to which a lower part of the tank is connected through an enclosed passageway (2), comprises a pressure balancing conduit (10) arranged within an insulation space (8) defined between inner and outer tank walls (4, 7), the conduit communicating with the interior of the tank atmosphere through a slot (11) at the top and with the passage (2) leading to the building (3) at the bottom. The conduit (10) defined by a plate (9) attached to the inner wall (4) also serves as an overfill protection device, a gutter (12) with drain (13) being mounted at its lower end, and accommodates ancillary pipelines (14) and/or electric cables. <IMAGE>

Description

SPECIFICATION Storage tank This invention relates to a storage tank for installation adjacent a building to which the tank is to be connected at its lower part. The connection to the building applies particularly to a kind of passage or corridor arrangement between the storage tank and a plant building supplied by the tank. However, the tank of the invention can be employed in any installation in which a tank is connected at its lower part to an enclosed space, such as a small service room built directly next to the tank.

To eliminate the formation of detrimental overpressure or subpressures within a closed tank during operations such as filling, draining or cleaning, a pressure balancing conduit is necessary to communicate the interior of the tank with the atmosphere through an opening in the top of the tank. The risk of damage occurring is particularly large if a vacuum pressure is created within the tank, since even a low vacuum can cause the tank wall to collapse inwardly. A vacuum pressure can easily arise, for example during tank cleaning when the warm cleaning liquid increases the temperature and vapour content inside the tank and then the tank is rapidly cooled down. To balance the pressure rapidly enough, the pressure balance conduit must have a sufficient cross-section area.For milk tanks of about 50 m3 capacity, for example, pressure equalizing tubes with a diameter in the range of 150-200 mm have been used. For reasons of simplicity, stack-like openings in the top of the tank have been used hitherto as pressure balancing conduits. Despite use of filter elements and the like, pollution of the tank contents by particles, small animals etc. from the ambient atmosphere cannot be eliminated completely.

Furthermore, in geographical areas with more severe climates, clogging of the conduit can occur through freezing in the screen elements or conduit openings. The pollution is obviously a difficult problem in the case of tanks holding food stuff, such as milk tanks outside dairy buildings. In such installations the freezing problem can also be accentuated due to formation of vapour and condensate due to frequent draining and filling operations and in particular the intermediate cleaning cycles.

As a remedy to the pollution and freezing problems of tanks erected beside a building, it has been suggested to provide a connection tube from the top of the tank either directly into the building or down to a corridor at the tank base. The term corridor is used in this context to mean any enclosed connection passage between the tank and the adjacent building. The passage can, for example, serve as a walk-way between the building and a manhole in the tank, as a culvert for pipes and cables between the tank and the building, or as housing for tank equipment.

During tank installation, special connection work is required for the comparatively large pressure balancing tube in addition to that necessary for the other pipelines required outside the tank, such as tubes for cleaning liquid and overflow pipes. In locations with cold climates all the tubes must be individually insulated to prevent freezing.

The aim of the present invention is to eliminate the need for piping outside the tank and reduce the connection work necessary during tank installation, and according to the invention there is provided a storage tank for installation adjacent a building with a lower part of the tank connected to the building, comprising inner and outer walls spaced apart to define an insulation space therebetween and a pressure balancing conduit open to the interior of the tank at the top thereof, said conduit being arranged within said insulation space and for communication with the building at the lower part of the tank.

The conduit preferably has a comparatively large cross-sectional area by making the crosssection elongated in the direction of the tank periphery thereby enabling the conduit to be dompletely included within the insulation space.

Hereby manufacturing advantages are also possible in that half of the conduit can be constituted by the tank inner wall while the rest of the conduit is obtained by welding a simple plate element to the tank inner wall along its two side edges.

A better understanding of the invention will be had from the following detailed description, given with reference to the accompanying drawings, in which: Figure 1 is a vertical section through an uninsulated tank embodying the invention and installed adjacent a building; and Figure 2 is a cross-section taken along the line II--II in Figure 1, and showing the tank including insulation and the outer wall or cover.

As shown in the drawings, tank 1 is at its lower part connected to a building 3 through an enclosed passage or corridor 2. The tank has a cylindrical inner wall 4 and an external outer wall or cover 7 arranged around the wall 4 and spaced from it by distance members 5, 6 so that an annular insulation space 8 is formed between the inner wall 4 and the external cover 7. In a part of the annular insulation space 8 located within the sector of the corridor connection, a plate element 9 is fixed to the inner wall 4 along its two vertical edges to form together with said wall a pressure balancing conduit 10 having a long and narrow cross-section.

The pressure balancing conduit 10 is at the top open to the tank interior through a slot 11 in the inner wall 4, this slot extending the full width of the conduit 10, and conduit 10 is open at the lower part of the tank to the corridor 2 underneath the bottom edge of the plate 9. To collect any condensate which may form and any liquid overflow, a collecting gutter 12 formed by a plate element is fixed to the inner wall 4, the gutter 12 being drained through a pipe 13.

Located within the pressure balancing conduit 10 is a pipe 14 for supplying cleaning liquid to the tank via a spreader or spraying device (not shown) mounted in the top of the tank.

As seen in Figure 2, the pressure balancing conduit 10 is made narrow enough to allow a thin layer of insulation between the conduit and the external cover 7. For installations which will never be subjected to low external temperatures, the insulation material outside the pressure balancing conduit can be omitted since, being connected to the atmosphere in the building and the atmosphere in the tank, the conduit itself provides sufficient insulation.

Advantageously, other service lines leading from the building or the corridor to the top of the tank, such as electrical cables for illumination and level control devices, can also be installed in the pressure balancing conduit. Due to the elongates slot opening in the top of the tank and the collecting gutter connected to the drain pipe, the pressure balancing conduit. Due to the elongated efficient overfill protection device.

Claims (7)

1. A storage tank for installation adjacent a building with a lower part of the tank connected to the building, comprising inner and outer walls spaced apart to define an insulation space therebetween and a pressure balancing conduit open to the interior of the tank at the top thereof, said conduit being arranged within said insulation space and for communication with the building at the lower part of the tank.

2. A tank according to claim 1, wherein the cross-section of the pressure balancing conduit is elongated in the direction of the tank periphery.

3. A tank according to claim 1 or 2, wherein the pressure balancing conduit is formed by a part of said inner wall and a plate element fixed to said inner wall along two side edges of the plate.

4. A tank according to any one of the preceding claims, wherein a line for supply of cleaning medium to the tank and/or other pipelines or cables are located within said pressure balancing conduit.

5. A tank according to any one of the preceding claims, wherein the pressure balancing conduit is arranged to serve as an overfill protection device for the tank by conveying liquid frorn the tank.

6. A tank according to any one of the preceding claims, wherein the tank is shaped as a vertical cylinder.

7. A storage tank substantially as herein described with reference to the accompanying drawings.