GB2251021A - Tank with secondary liquid containment - Google Patents

Abstract

A storage tank (1) for liquids consists of a main storage tank (2) surrounded by a secondary outer container (3) to retain overfill or leakage from the storage tank. The walls of the container and tank are spaced about 1-8mm apart except for an area between the walls defining a containment zone (7), preferably about 10% of the volume of the storage tank. Conveniently the containment area may be at one end of the container, which may be rectangular or cylindrical. A sighting glass (9) may be provided to indicate the amount of liquid in the containment zone and means (9a) may also be provided for drawing off liquid from the containment zone and for discharge and drainage of the inner storage tank. An inspection cover (16) to the inner tank may also be provided. <IMAGE>

Description

STORAGE VESSELS FOR LIQUIDS The present invention relates to storage vessels for liquids in which the main storage tank is surrounded by a secondary tank capable of retaining any overfill or leakage.

Storage vessels for liquids such as fuel oils and chemicals have in the past been contained in catchpits to retain any leakage or spillage from the tanks. More recently double walled storage vessels have been developed with a space between the inner and outer walls acting to retain overfill or leakage. Convenient means are provided to withdraw liquid from the space within the inner and outer walls as and when necessary.

British Patent 2177149 discloses a double walled vessel in which reinforcing means are provided between the inner and outer walls and act to maintain the relative positions of the two containers.

We have now developed an improved form of storage vessel comprising a tank positioned within an outer container and in which the tank walls are adjacent to the inner walls of the container except for one area of wall, conveniently at the end of the vessel, wherein a containment zone is provided between the outer and inner walls of the tank or container. The volume of the containment zone may conveniently amount to about 10% of the volume of the storage tank and the gap between the outer container and the tank walls at other areas may be as little as l-8mm, preferably about 1-2mm.

The vessel preferably includes an inspection cover to the inner tank and there may be provided a means, such as a sighting glass, for observing the presence of liquid in the containment zone. Preferably also means are provided extending into the containment zone for drawing off any liquid collecting therein. Discharge and drain means extending through the outer container and communicating with the tank are also provided.

The vessel may be rectangular or cylindrical; where the tank is cylindrical in shape then it will normally be positioned with its major axis substantially horizontal.

The double wall vessel of the present invention has the advantage of taking up less ground area than current storage vessels with catchpits is more readily constructed and is less expensive, Embodiments of the present invention will now be described with reference to the accompanying drawings in which: Figure 1 is a side view of a rectangular storage vessel of the present invention; Figure 2 is a plan view from above of the vessel of Figure 1; Figure 3 is a side view in direction A of Figure 1; Figure 4 is a side view of a cylindrical container according to the present invention, Figure 5 is a plan view from above of the storage vessel of Figure 4 and, Figure 6 is a section through B-B of Figure 4.

Referring to Figures 1 - 3, a rectangular steel double-walled storage vessel, generally indicated at 1, consists of a tank 2 having walls 21, 22, 23 and 24 and a base 25, an outer container having walls 31, 32, 33, 34 and a base 35, and a top 4 shared by both the tank 2 and the outer container 3. In use the vessel may be located on a plurality of steel supporting sections 6. Walls 31-33 of the outer container 3 are spaced adjacent to the corresponding walls 21-23 of the tank 2 with a gap lmm wide therebetween. The distance between walls 34 and 24 of the outer container and tank is sufficient to provide a containment zone 7 equal to about 10n of the capacity of the inner tank 2. Base 25 of inner tank 2 rests on base 35 of the outer container 3.

As indicated above top 4 is shared by the tank 2 and outer container 3 and is welded to the side portions of outer container 3 around all four walls to provide a liquid tight seal. The walls 21-24 of tank 2 extend up to and touch top 4 and are welded thereto to provide a liquid tight seal.

An overflow coupling 8 is provided in top 4 between inner tank 2 and containment space 7. A sight glass 9 extends upwardly from the bottom of container space 7 and includes a drain valve 9a at the base thereof to permit liquid to be withdrawn from space 7.

A fill pipe 10 extends from a side of the tank to entry port 11 in the top of tank 2. A suitable valve 12 and the closure cap 13 is fitted to the end of pipe 10.

A drain valve 14 and a draw-off valve 15 communicating with the inner tank 2 are provided at the base of the outer container 3.

An inspection cover 16 and lifting lugs 17 are provided at the top of the vessel to enable it to be moved. Also provided in top 4 is a vent 18 communicating with containment space 7. The tank 2 is vented to the containment space 7 via coupling 8.

In the construction of the vessel 1, the tank 2 is formed from steel plate and is then positioned on a base 35 of outer container 3. The walls 31-34 of the outer container are then welded in position, finally the top plate 4 is welded onto the walls of the outer container and the fitments are secured in place.

In use any leakage from the inner tank 2 drains into the narrow gap between walls 21-24 of tank 2 and the walls 31-34 of the container 3 and into the containment space 7. Any overflow from the top of the inner tank 2 flows into the containment space 7 via coupling 8. The sight glass 9 provides a visual indication of the build-up of liquid in the container space which can be drawn off through valve 9a.

Referring to Figures 4, 5 and 6, storage vessel 100, supported on a cradle 141, consists of a inner tank 101 having domed end walls 102 and 103 and an outer coaxial tubular container 120 partially surrounding tank 101 and having domed end portions 121 and 122 parallel to domed end portions 102 and 103 of inner tank 101. The space between the domed end walls 102 and 121 defines a containment space 130 which has a volume of approximately equal to 10% of the volume of tank 101.

The edges 124 and 125 of the outer container 120 and the edge portion 126 of domed end 122 are welded to the inner tank 101; portion 123 of outer container 120 is welded to the top of tank 101 at edge 127 and to domed end 121 thereby completely sealing the tank to the outer container, top 104 being common to the tank and container.

The gap between the walls of the tank 101 and the outer container 120 and between domed end walls 103 and 122 respectively varies from approximately 0 at the base (where the two are in contact) to about 6mm at the widest point.

A sight glass 131 extends from the base of containment space 130 and includes a drain valve 132 to enable liquid contained in space 130 to be removed as necessary. A vent 133 is located in the top of portion 123 of outer container 120 and communicates with space 130. The tank 101 is vented to containment space 130 via a channel 141.

A fill pipe 134 extends from the top 104 and contains a suitable valve and cap 135 at the end thereof.

Top 104 also includes a manhole inspection cover 138 and lift lugs 136 and 137.

Draw off and drain valves 139 and 140 are provided at opposite ends of inner tank 101, drain off valve 140 having a portion extending through container space 130.

When in use, any leakage from the inner tank will run into the gap between the tubular walls of the tank and container and the containment space 130 where its presence will be indicated by sight glass 131 and can be drawn off through valve 132 as necessary.

Claims (13)

1. A storage vessel comprising an outer container and an inner storage tank located within the container and substantially surrounded thereby, the inner tank being positioned within the container to provide a containment zone between a section of the opposed inner and outer walls of the container and tank respectively, the remainder of the said opposed inner and outer walls being adjacent to each other.

2. A vessel according to claim 1 wherein the containment zone is located at one end of the container.

3. A vessel according to claims 1 or 2 wherein the containment zone has a volume equivalent to 10n of the volume of the storage tank.

4. A storage vessel according to any one of the preceeding claims wherein the inner and outer walls of the container and tank respectively, other than in the containment zone are 1-8mm apart.

5. A vessel according to claim 4 where the inner and outer walls are 1-2mm apart.

6. A vessel according to any one of the preceeding claims wherein the storage tank and outer container are rectangular.

7. A vessel according to any one of claims 1-5 wherein the storage tank and outer container vessel are cylindrical.

8. A vessel according to claim 7 wherein the container and tannic are positioned with the major axis substantially horizontal.

9. A vessel according to any one of the preceeding claims wherein a sighting glass is provided parallel to the containment zone for observing the presence of liquid in the said zone.

10. A vessel according to any one of the preceeding claims wherein means are provided to draw off liquid from the containment zone.

11. A vessel according to any one of the preceeding claims wherein discharge and drain means for the storage tank extend through the outer container and communicate with the storage tank

12. A vessel according to any one of the preceeding claims including an inspection cover located in the top of the inner storage tank.

13. A storage vessel substantially as herein described with reference to the accompanying drawings.