GB2258001A - Storage tank for volatile solvents - Google Patents

Abstract

A storage tank (10) for holding volatile solvents has an aperture (20) provided in the top thereof which is closable by a slidable door (22). When the door (22) is closed escape of solvent vapour is prevented by means of an inflatable seal (24) provided around the periphery of the aperture (20). An expandible bag (62), (Fig. 3, not shown) is provided in the container to store any vapour emitted from the solvent when the door (22) is closed. A pulley system is provided in the tank for moving baskets (60) (Fig. 2, not shown) housing material to be cleaned in the solvent. Seals are provided to prevent release of solvent via the pulley system. <IMAGE>

Description

STORAGE-TANK This invention relates to a storage tank and particularly but not exclusively to a storage tank for volatile fluids.

It is known to contain volatile liquids within a storage tank with a door provided at the top of the storage tank. Such tanks are used in one application as a reservoir for cleaning solvents. Unclean solid articles such as articles made from metal, ceramic and glass are immersed in the solvent reservoir for cleaning purposes. The solvents are often volatile.

Cooling coils are provided above the reservoir of solvent in order to condense any solvent vapour which may rise towards the door.

Conventional storage tanks usually comprise either a cover which may be manually lifted or a roller shutter door. When the former cover is lifted off the main body of the tank a vacuum is created resulting in solvent vapour rising above the cooling coils into the atmosphere. When roller shutter doors are used the vapour layer in the storage tank is more stable, but as the roller shutter door has hinged slats the door cannot be sealed resulting in vapour loss.

The present invention has been made from a consideration of these problems.

According to a first aspect of the present invention there is provided a storage tank for holding at least one fluid, wherein said storage tank comprises an aperture and a door movable from a first position in which the door closes the aperture and a second position in which the aperture is open and the aperture may be substantially sealed by an expandible seal when the door is located in the first closed position. The seal is preferably inflatable.

In a preferred embodiment of the invention the door is solid and contains no perforations, apertures or the like so that no vapour may pass through the door when closed. The door is preferably a sliding door.

The storage tank may also contain an inflatable container which may act to store solvent vapour.

According to a second aspect of the present invention there is provided a storage tank for holding at least one fluid wherein the storage tank comprises an expandible storage container which is operative to store vapour from the fluid.

The expandible storage container may comprise an inflatable bag. This container acts to store any vapour emitted from the solvent so as to prevent a pressure build up within the sealed storage tank. This expandible container is preferably used when the stored fluid is to be heated and/or the nature of the fluid is such that it emits a large amount of vapour at the operating temperature of the storage tank.

The expandible container may comprise a valve which may be used to close the container when appropriate. The valve is preferably closed when the door of the storage tank is open.

The storage tank may comprise a system such as a pulley system for moving objects within the storage tank. If so it is likely that at least a part of that system is located in an outer chamber sited outside the inner chamber containing the reservoir of fluid.

As part of the system is moving between the inner and outer chambers, such as a belt running over the pulleys, then the inner chamber containing the reservoir must have an aperture through which the belt may pass. This aperture also acts as a means for escape of fluid vapour.

According to a third aspect of the present invention there is provided a storage tank comprising a chamber for storing a fluid and transporter means for moving a body within the storage tank, wherein at least a part of the transporter means extends between said chamber and a part of the storage means outside said chamber and wherein a seal is provided around said part of the transporter means such that escape of fluid from the chamber past said part of the transporter means is substantially prevented.

The transporter means may comprise a pulley system, which may be driven by a drive shaft or compressible fluid operated device such as a hydraulic or pneumatically operated piston.

In order that the invention may be more readily understood specific embodiments thereof will now be described by way of example only with reference to the accompanying drawings in which: Fig. 1 is a perspective view of one storage tank in accordance with the present invention; Fig. 2 is a cross sectional view through the vertical plane passing through the line II-II of Fig.

1; Fig. 3 is a cross sectional view through the vertical plane passing through the line II 1-111 of Fig. 1; and Fig. 4 is a cross sectional view of a second storage tank in accordance with the present invention.

Referring to Figs. 1 to 3 a storage tank 10 comprises four side walls, only two of which 12,14 are illustrated, a base 16 and a top 18. The top 18 comprises an aperture 20 which opens at the front of the storage tank 10. A door 22 is slidably received within the top 18 and is movable between a first position in which the door 22 is wholly retracted as shown in Fig. 1 and a second position in which the door 22 covers the aperture. An inflatable seal 24 extends around the periphery of the aperture 20. Once the door 22 is in the second closed position the seal 24 may be inflated so as to seal the aperture 20 and prevent escape of fluid vapour from the storage container 10. The seal 24 may be deflated before the door 22 is opened.

The container comprises an inner chamber 26 for receiving a solvent system 28. In this instance the solvent system 28 is a mixture of an alcohol and a fluid sold under the trade mark FLUTEC. Cooling coils 30 are provided in the inner chamber 26 above the top of the solvent reservoir 28. The cooling coils 30 act to cool and condense any solvent vapour which may rise into the vicinity of the cooling coils 30 so as to minimise the amount of solvent vapour within the storage tank 10.

The inner chamber 26 comprises an upstanding wall 32 which divides the base of the inner chamber 26 into two sections 34,36. A connecting pipe 38 extends between the bases of the two sections 34,36.

Two slides 40,42 are movable by a pulley system 44 from a lowermost position 40a,42a to an intermediate position 40b,42b and out of the storage tank 40c,42c. One slide 40 is received in the left hand section as illustrated 34 and the other slide 42 is received in the right hand section as illustrated 36. The pulley system 44 comprises a rotatable drive shaft 46 located below the connecting pipe 38. An endless belt 48 passes from the left side of the shaft to a wheel 50 provided on an upper shaft 52 which is shorter than the drive shaft 46. The upper shaft 52 extends from the outside to the inside of the inner chamber 26. A second wheel 54 is provided at the end of the upper shaft 52 which is inside the inner chamber 26. This end is connected by a second endless belt 56 to a further wheel 58 located towards the base of the chamber 26. One side of the second belt 56 is connected to the left hand slide 40. This slide 40 can therefore be moved up or down by appropriate rotation of the drive shaft 46 which drives the upper shaft 52 and causes the second belt 56 on which the slide 40 is located to rotate.

The right hand slide 42 is operated in a similar manner.

A rotating seal 60 is provided around each upper shaft 52 to prevent vapour escaping from the chamber 26.

The right hand section of the chamber 26 comprises transducers which may be excited by high frequency current so as to cause vibration. This vibration causes air pockets in the form of bubbles to rise and impact with the solid material being cleaned imploding the material and providing an enhanced cleaning action.

In use the material to be cleaned is located in a wire basket 60 which is placed on a slide 40,42. The basket 60 is lowered into the alcohol/Flutec solvent system 28 located in the left section 34. The basket 60 is then raised above the solvent layer 28 into the intermediate position 40b where alcohol/Flutec vapour aids the cleaning process. The basket 60 is then removed from the storage container 10 and placed on the right hand slide. The basket 60 is lowered into the solvent mixture in the right hand section 36 and the transducers are excited. The basket 60 is then raised above the fluid solvent into the intermediate position 42b where it is cleaned by the vapour. The basket 60 is then raised and the clean solid material is removed.

The solvent system 28 may be heated when the storage tank 10 is in use. As the storage tank 10 is a closed system and a large amount of solvent vapour may be produced an expandible vapour storage container 62 is provided which opens into the rear of the chamber 26. As excess vapour is produced this passes into the expandible bag 62. A valve 64 is provided at the entrance to the bag 62 such that the bag 62 may be closed when the door 22 is open. This minimises vapour losses. When the storage tank 10 is not in use, overnight for example, the door 22 is closed and the valve 64 is left open. The vapour in the bag 62 gradually empties into the chamber 26 and condenses.

Referring to Fig. 4 a second storage tank 70 is similar to that previously described except in that the means for moving the slides comprises two hydraulically operated pisons 72 rather than a drive shaft. These pistons may be used to move the belt 74 up or down as required so as to move the slides.

Seals 76 are provided as previously described.

It is to be understood that the above described embodiments have been described by way of illustration only. Many modifications and variations are possible.

Claims (13)

1. A storage tank for holding at least one fluid, wherein said storage tank comprises an aperture and a door movable from a first position in which the door closes the aperture and a second position in which the aperture is open and the aperture may be substantially sealed by an expandible seal when the door is located in the first closed position.

2. A storage tank as claimed in claim 1, wherein the seal is inflatable.

3. A storage tank as claimed in claim 1 or claim 2, wherein no perforations or apertures are provided through the door.

4. A storage tank as claimed in any preceding claim, wherein the door is mounted for sliding movement.

5. A storage tank as claimed in any preceding claim, wherein said tank comprises an expandible storage container operative to store solvent vapour.

6. A storage tank for holding at least one fluid wherein the storage tank comprises an expandible storage container which is operative to store vapour from the fluid.

7. A storage tank as claimed in claim 5 or claim 6, wherein the expandible storage container comprises an inflatable bag.

8. A storage tank as claimed in any of claims 5 to 7, wherein the expandible container comprises a valve for closing the container.

9. A storage tank as claimed in claim 8, wherein the valve is operative to be closed when the door of the tank is in the second open position.

10. A storage tank as claimed in any preceding claim, wherein the tank comprises a chamber for storing a fluid and transporter means for moving a body within the storage tank, wherein at least a part of the transporter means extends between said chamber and a part of the storage means outside said chamber and wherein a seal is provided around said part of the transporter means such that escape of fluid from the chamber past said part of the transporter means is substantially prevented.

11. A storage tank comprising a chamber for storing a fluid and transporter means for moving a body within the storage tank, wherein at least a part of the transporter means extends between said chamber and a part of the storage means outside said chamber and wherein a seal is provided around said part of the transporter means such that escape of fluid from the chamber past said part of the transporter means is substantially prevented.

12. A storage tank as claimed in claim 10 or claim 11, wherein the transporter means comprises a pulley system.

13. A storage tank substantially as described herein with reference to the accompanying Figs. 1 to 3 or 4.