GB2262302A

GB2262302A - Liquid storage tank

Info

Publication number: GB2262302A
Application number: GB9211919A
Authority: GB
Inventors: Simon Mark Fowler
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-10-08
Filing date: 1992-06-05
Publication date: 1993-06-16
Anticipated expiration: 2012-06-05
Also published as: GB9121274D0; GB9211919D0; GB2262302B

Abstract

A tank 12 is contained entirely within a bund 10 and a cover extends from the tank to cover the whole of the bund. There is a small gap 40 between the cover and the top of the bund for venting purposes, and a skirt 36 protects against entry of foreign matter. A manhole 38 provides access to the tank 12 via the cover 34, and a scavenging pipe 42 and suction pipe 50 pass sealably through the manhole to the bottom of the tank. <IMAGE>

Description

LIQUID STORAGE FACILITY TECHNICAL FIELD OF THE INVENTION This invention relates to storage facilities for storing harmful or unpleasant liquids out-of-doors.

The facility comprises a storage tank mounted in a vessel which is commonly referred to as a catchpit or bund, to retain the liquid in the event of the storage tank failing. The facility may be used with a wide variety of contaminatory liquids, mineral oils being one example.

BAGKGPOUD Conventionally, the tank and its bund are either rectangular or cylindrical. Pollution control regulations require that the capacity of the bund shall be at least 110% that of the tank. the bund is conventionally open-topped, and the tank is connected to an external dispensing system for the liquid through a delivery pipe which extends from a lower part of the tank and through the wall of the bund at a low level.

Among the disadvantages of the above arrangement are the following.

Because the bund is open-topped, it accumulates rainwater which reduces its capacity and necessitates regular draining of the bund. For this purpose the bund has to be provided with a suitable drainage facility in the form, generally, of a drain tap. If the storage tank fails, its contents spilling out into the bund will mix with the rainwater and other detritus, so rendering them useless and, incidentally, creating an additional disposal problem. Also, it has been found in practice that the drain tap tends to be left open in order to avoid the need to attend regularly to drainage. This practice automatically negates the purpose of the bund, which is to provide a safe receptacle into which spillage or leakage from the tank can be collected.

In addition, the storage tank must be vented to prevent pressure build-up during filling, and this can cause liquid to be sprayed out beyond the bund in the event of overfilling.

Finally, the need for a delivery pipe passing through the wall of the bund complicates manufacture and also gives rise to sealing problems between the pipe and the bund wall. This also introduces an inherent weak point in the structure of the bund.

The present invention addresses these problems, among others.

SUMMARY OF THE INVENTION The present invention proposes a storage facility for harmful liquids, comprising a storage tank mounted in a bund, the storage tank having a cover which extends outwardly so as to cover the whole of the storage tank and the bund leaving a small gap between the top of the bund and the cover, the storage tank being vented into the bund.

Since the bund is covered it is less likely to collect foreign matter, and by venting the tank into the bund, which is itself vented to atmosphere via the gap between the bund and the cover, spillage is less likely during filling.

To reduce the risk of foreign matter entering the bund the cover preferably has a depending peripheral wall or lip which is spaced from and extends below the top of the bund.

The tank preferably has a dispensing pipe which passes sealably through the cover through which liquid may be drawn from the tank. In addition, the tank preferably has a scavenging pipe which passes from the lowest part of the tank sealably through the cover. Thus, the pipes do not present a potential point of failure in the tank or the bund. The pipes preferably pass sealably through a manhole lid mounted in the cover.

The storage tank is preferably seated on bearers on the base of the bund. In a preferred arrangement the storage tank and the cover can be lifted as one from the bund for ease of repair and maintenance or replacement of the tank in the event of failure.

BRIEF DESCRIPTION OF THE DRAWINGS The following description and the accompanying drawings referred to therein are included by way of non-limiting example in order to illustrate how the invention may be put into practice. In the drawings: Figure 1 is a vertical section through a storage facility of the invention, taken on the line I-I of Fig. 2, and Figure 2 is a similar vertical section through the storage facility taken perpendicularly to that of Fig. 1 on line II II.

DETAILED DESCRIPTION OF THE DRAWINGS The oil storage facility shown in the drawings comprises a bund 10 and a storage tank 12 contained entirely within the bund. The bund 10 is a vessel which is rectangular in plan view and having side walls 14, a rear wall 16 and a front wall 18. The tank 12 is also rectangular in plan and comprises side walls 20, a rear wall 22 and a front wall 24. The base 26 of the tank is supported firmly on bearers 28 which lie on the base 30 of the bund which is in turn supported on further bearers 32. The bearers spread the load as evenly as possible over the bund base 30 and over the ground G.

The walls 20, 22 and 24 of the tank 12 are securely welded along their length to an overall cover 34 which is thereby secured to the storage tank 12. The cover 34 is slightly pitched to shed water, as shown in Fig.

1, and extends outwardly on all sides beyond the tank 12 to cover the whole of the bund 10. The cover 34 terminates in a downturned peripheral skirt portion 36 which protects the bund from ingress of rain and other foreign matter.

There is a small gap between the cover 34 and the top edges of the bund walls 14, 16 and 18, for venting purposes. In addition, this reduces the risk of the cover sitting on the walls of the bund due to manufacturing tolerances and the like, which might otherwise result in the tank 12 being suspended in the bund 10.

A manhole 38 is provided in the cover 34 for access to the inside of the tank 12. The lid of the manhole 38 also sealably contains a scavenging pipe 4 and a suction pipe 50, both of which extend downwardly within the tank 12 to terminate just above its base 26. The scavenging pipe 42 may be connected to a suitable pumping facility, not shown, for the removal of unwanted liquid and/or dirt from the tank. To this end, it is preferred for the base 26 of the tank to be formed with a slope with the pipe 42 directed into the lowest part of the base, angled if necessary, for the collection of unwanted matter.

The tank 12 is vented into the bund through a venting channel 40 formed in the cover 34, the bund being, in turn, vented to the outside air via the gap between the bund walls and the cover 34. As an alternative to the venting channel 40, a venting pipe (not shown) can be welded into the upper portion of the tank, or venting apertures can be formed in the cover 34 above tank 12 and above the space between the tank and bund with the apertures being covered by a weather shield. If the tank 12 is inadvertently overfilled it will overflow into the bund via the venting channel 40, or its equivalent.

A suitable anti-siphon valve or stopcock, not shown, can be provided to prevent the possibility of liquid being siphoned out of the tank through the pipes 42 and 50.

Should the tank 12 develop a leak it will fill the bund and then overflow down the walls 14, 16 and 18 of the bund through the gap between the bund 10 and the cover 34. The leak will thus be clearly visible. If necessary, the repair or replacement of the storage tank can quickly and easily be achieved by lifting the storage tank and cover out of the bund, to which they are not permanently secured.

The manufacture of the storage facility is also relatively simple, involving a minimum amount of welding.

Claims

1. A storage facility for harmful liquids, comprising a storage tank mounted in a bund, the storage tank having a cover which extends outwardly so as to cover the whole of the storage tank and the bund leaving a small gap between the top of the bund and the cover, the storage tank being vented into the bund.

2. A liquid storage facility according to Claim 1, in which the cover has a depending peripheral wall or lip which is spaced from and extends below the top of the bund.

3. A liquid storage facility according to Claim 1 or 2, in which the tank has a dispensing pipe which passes sealably through the cover through which liquid may be drawn from the tank.

4. A liquid storage facility according to Claim 3, in which the dispensing pipe passes sealably through a manhole lid mounted in the cover.

5. A liquid storage facility according to Claim 1 or 2, in which the tank has a scavenging pipe which passes from the lowest part of the tank sealably through the cover.

6. A liquid storage facility according to Claim 5, in which the scavenging pipe passes sealably through a manhole lid mounted in the cover.

7. A liquid storage facility according to any preceding claim, in which the storage tank is seated on bearers on the base of the bund.

8. A liquid storage facility according to any preceding claim, in which the storage tank and the cover can be lifted as one from the bund.

9. A liquid storage facility which is substantially as described herein.