GB2203229A

GB2203229A - Vent pipes for liquid storage tanks

Info

Publication number: GB2203229A
Application number: GB08708610A
Authority: GB
Inventors: Mervyn Douglas Watts
Original assignee: WATTSWADE SERVICES Ltd
Current assignee: WATTSWADE SERVICES Ltd
Priority date: 1987-04-10
Filing date: 1987-04-10
Publication date: 1988-10-12
Anticipated expiration: 2007-04-10
Also published as: GB2203229B; GB8708610D0

Abstract

A vent pipe is mounted on a fuel storage tank (10) to conserve fuel and reduce the escape of potentially dangerous gases. The vent pipe has an upstanding inner tube (12) of metal surrounded by a sleeve (14) of a water-absorbent material. The lower end of the sleeve (14) is surrounded by a water reservoir (16). Within the inner tube (12) is fixed a helically coiled insert (18) of copper or aluminium strip. Vapours rising within the tube (12) condense on the cold inside wall of the tube and run back into the tank, the tube being cooled by the continuous evaporation of water from the sleeve (14). <IMAGE>

Description

Title: Vent Pipes for Liquid Storage Tanks DESCRIPTION Field of the invention This invention relates to a vent pipe for liquid storage tanks, especially fuel tanks.

Backqround to the invention It is generally necessary in the storage of liquid petroleum fuel to provide a vent pipe connected to the top of the storage tank. The vent pipe allows evaporated fuel to escape to the atmosphere, thereby to prevent a potentionally dangerous build up of gaseous fuel within the tank. In the case of high octane fuels such as aviation spirit, it is usual to provide a flame guard at the top of the vent pipe, which pipe conventionally takes the form of a single straight tube upstanding from the top of the tank.

The invention According to the present invention, there is provided a vent pipe for a liquid storage tank, comprising an upstanding tube of thermally conducting material, a sleeve of water-absorbent material surrounding the tube, and a source of water for continuously maintaining the sleeve in a moist condition.

In accordance with the invention, the continuous evaporation of water which takes place at the sleeve results in a cooling of the water-absorbent material which in turn results in cooling of the thermally conducting tube within it. Evaporated liquid from the storage tank, in rising through the tube, thus tends to condense on the inner wall surface of the tube and run back into the tank.

Whilst not restricted to use with fuel storage tanks, the vent pipe in accordance with the invention is especially applicable thereto, for the dual purposes of conserving fuel and reducing escape of potentionally dangerous gases into the atmosphere.

Preferably, the inner tube is made of metal, in particular a non-ferrous metal in the case of petroleum fuels. For example, said tube may be of cast bronze. The surrounding sleeve is preferably made of a synthetic sponge-type material such as that sold under the trade mark "Oasis".

A continuous supply of water may be provided by an annular reservoir surrounding the water-absorbent sleeve over a part of its length, more especially a reservoir surrounding the lower end region of the sleeve just above the storage tank.

For maximising condensation of the fuel or other liquid rising through the inner tube, the latter may contain a coiled insert of thermally-conducting material, such as helically coiled strip of copper or aluminium. The insert may be fixed to the inside wall of the tube. The internal coil causes the vapours rising in the tube to swirl, increasing contact of said vapours with the cold inside wall surface of the tube, and therebv maximising the condensation which takes place.

Pressure venting at fuel tanks requires compliance with the regulations of the Petroleum Consolidation Act. The cooled insert is arranged to have minimum effect on the cross-sectional area of the gas flow path within the inner tube, but in any event it is insured that, with the coiled insert fixed in position, the area of the gas flow path, throughout the length of the tube, is proper to comply with the said regulations.

As is conventional, a flame guard may be provided at the top of the inner tube.

Brief description of the drawings A vent pipe in accordance with the invention is exemplified in the following description, making reference to the accompanying drawings, in which: Figure 1 is a view of a practical embodiment of vent pipe in side elevation; and Figure 2 is a plan view thereof.

Description of embodiment Referring to the drawings the reference 10 denotes a liquid storage tank, more especially a storage tank for a fuel such as petroleum spirit.

The vent pipe in accordance with the invention comprises an upstanding tube 12 of non-ferrous metal, possibly cast bronze, and a relatively thick walled surrounding sleeve 14 of a synthetic sponge-type material such as that known by the trade mark "Oasis". A water reservoir 16, in which the water level is maintained automatically or manually surrounds the lower end region of the sleeve 14. The water in the reservoir 16 has free access to the absorbent sleeve 14 and is drawn into the sponge-type material thereof to keep the sleeve continuously moist for its entire height. Within the inner tube 12 is fixed a helically coiled insert 18 of copper or aluminium strip for imparting a swirling motion to fuel gasses rising within the tube and thus maximising contact thereof with the inner wall surface of the tube. The said tube 12 is surmounted by a flame guard 20.

In use, vapours rising within the tube 12 due to evaporation of liquid fuel in the storage tank 10 are caused to condense on the cold inside wall surface of the tube and run back into the tank. This effect is produced by the continuous cooling of the tube 12 which takes place due to continual evaporation of water which occurs at the surrounding sleeve 14, resulting in a cooling of the sleeve material which is transferred to the inner tube.

The embodiment above described may be modified in various ways within the scope of the invention hereinbefore defined.

Claims

1. A vent pipe for a liquid storage tank, comprising an upstanding tube of thermally conducting material, a sleeve of water-absorbent material surrounding the tube, and a source of water for continuously maintaining the sleeve in a moist condition.

2. A vent pipe according to claim 1, wherein the upstanding tube is made of metal.

3. A vent pipe according to claim 2, wherein the upstanding tube is made of a non-ferrous metal.

4. A vent pipe according to claim 3, wherein the upstanding tube is made of cast bronze.

5. A vent pipe according to any of the preceding claims, wherein the surrounding sleeve is made of a synthetic sponge-type material such as that sold under the trade name "Oasis".

6. A vent pipe according to any of the preceding claims1 wherein a continuous supply of water is provided by an annular reservoir surrounding the water-absorbent sleeve over the lower part of its length.

7. A vent pipe according to any of the preceding claims, wherein for maximising condensation of the liquid rising through the upstanding tube, the latter contains a coiled insert of thermally-conducting material.

8. A vent pipe according to claim 7, wherein the coiled insert is a helically coiled strip of copper or aluminium.

9. A vent pipe according to claim 7 or 8, wherein the insert is fixed to the inside wall of the inner tube.

10. A vent pipe according to any of the preceding claims and in combination with a fuel storage tank.

11. A vent pipe constructed and arranged substantially as herein particularly described with reference to the accompanying drawings.