GB2454088A - An apparatus for cleaning the interior of a tank - Google Patents

Abstract

An apparatus 10 for emptying material from a tank 12 includes an upper arm 20 defining a longitudinal axis, and a lower arm 30 hinged at one end to the upper arm 20 and hinged at the other end to a suction head 34. A suction pipe 30 extends from the suction head 34 along the lower arm 30 and the upper arm 20, and can be connected to an external suction pump. Moving the upper arm 20 longitudinally moves the suction head 34 along a path radiating from a point S, and turning the upper arm 20 about its axis moves the suction head 34 along an arcuate path around S, so a large area of the base of the tank 12 can be accessed and cleaned by the apparatus 10. The apparatus 10 can be inserted through a small access hole 16 in the roof of the tank 12.

Description

Tank Emptying The present invention relates to an apparatus for emptying material from a tank and which requires only limited access; the invention also provides a method of emptying material from a tank using such an apparatus.

In this document the term tank should be construed as encompassing any type of container whose inside bottom surface is to be cleaned. The bottom surface may be flat, curved, or sloped, but the apparatus is not generally suitable if the bottom surface is very rough, or stepped. The apparatus is particularly suitable for emptying storage tanks containing sludge, and is also suitable for tanks used to store radioactive materials, and having a cover or lid, such that access is limited.

For example, sludge and debris tend to collect at the bottom of bodies of water such as tanks or ponds used to store radioactive waste, and it is required at times to empty the tank and remove all the sludge; this may be difficult owing to limited access. There are particular problems if the contents of the tank are radioactive, as it may be necessary to ensure operators of any equipment are well shielded from the tank contents, and use of electronic components within the tank may not be feasible.

According to the present invention there is provided an apparatus for emptying material from a tank, the apparatus comprising an upper arm defining a longitudinal axis, a lower arm hingedly connected adjacent to one end to the upper arm and hingedly connected adjacent to the other end to a suction head, and a suction pipe extending from the suction head along the lower arm and the upper --)-arm, the hinged connections being such that if the suction head is resting on a fixed surface orthogonal to the said longitudinal axis, movement of the upper arm parallel to its longitudinal axis causes the lower arm to turn about the connection to the upper arm.

In a preferred embodiment the suction pipe provides the structural element of the lower arm along at least the bulk of its length.

In use the apparatus can be inserted through a small hole, for example an access hole in a cover of the tank, and set up with the upper arm extending in a generally upright direction, and with the suction head resting on the bottom inside surface of the tank. Preferably the apparatus also comprises a guide block to be installed in the hole, through which the upper arm extends, the guide block allowing the upper arm to be slid parallel to its longitudinal axis and to be rotated about its longitudinal axis. Hence, in use, the intersection of the longitudinal axis of the upper arm with the bottom surface of the tank is the centre of operation -the suction head can be moved along arcuate paths (centred on the centre of operation) by turning the upper arm about its longitudinal axis, and can be moved along radial paths towards or away from the centre of operation by sliding the upper arm longitudinally.

Preferably a liquid supply line is also provided, extending along the upper arm and the lower arm to the suction head. By connecting a suction pump to the suction pipe the contents of the tank can be extracted, and any sludge on the bottom of the tank can be liquidised, if necessary, by supplying liquid along the liquid supply line, to assist the sludge extraction process.

The apparatus is comparatively inexpensive and simple, and enables tank floors to be cleaned over a large area, to remove liquids, slurries and other fluids, while requiring access through only a small aperture.

Preferably the suction head is provided with castors or wheels, so it can readily roll over the surface of the tank. And preferably the suction head is provided with fins projecting to near the surface of the tank, at least on the region of the suction head which in use is closest to the centre of operation. If solid debris is lying on the bottom surface and is too large to be extracted through the suction pipe, then the suction head may be manoeuvred into a position radially beyond this debris, and the suction head can then be moved so as to drag the debris towards the centre of operation, the fins pushing on the debris. (Subsequently such debris lying directly below the access hole can be removed by conventional equipment.) The invention will now be further and more particularly described, by way of example only, and with reference to the accompanying drawings, in which: Figure 1 shows a perspective view of a tank emptying apparatus of the invention, comprising an upper arm, a lower arm, and a suction head, in use within a storage t'ank; Figure 2 shows a perspective view to a larger scale of the upper arm and its connection to the lower arm of the apparatus of figure 1; Figure 3 shows a perspective view to a larger scale of the suction head and its connection to the lower arm of the apparatus of figure 1; and Figure 4 shows a longitudinal sectional view of an alternative suction head to that of figure 3.

Referring now to figure 1, a tank emptying apparatus of the invention is shown installed in a concrete storage tank 12 containing radioactive liquid with some radioactive sludge. The tank 12 consists of a concrete base and walls 13 with a steel liner 14 at the bottom, and with a concrete cover 15 with four 300 mm square access holes 16. The apparatus 10 consists of a square section upper arm 20 which can slide longitudinally through a guide structure 22 mounted on a plate 24. This plate 24 is installed on the concrete cover 15, with the upper arm 20 extending through one of the access holes 16. In this example the upper arm 20 is of length 4 m, and 150 mm square in cross-section.

Referring also to figure 2, at the bottom end of the upper arm 20 is a hinge mechanism 26 connecting the upper arm 20 to a frame 28 forming the top end of a lower arm 30. Apart from the frame 28, the lower arm 30 consists of a rigid tube 32 extending the remainder of its length (which is also 4 m in this example). The hinge mechanism 26 allows the lower arm 30 to turn about a horizontal axis P relative to the upper arm 20, but does not allow the lower arm 30 to reach a position aligned with the upper arm 20 (at which the hinge mechanism 26 might lock).

Referring now to figure 3, a generally rectangular suction head 34 is connected to the lower end of the lower arm 30. The suction head 34 consists of a generally rectangular framework defining six parallel plates or fins 36 spaced apart in vertical planes and linked by a crossbar 37. The fins 36 are generally arrowhead-shaped, tapering to points at the front end (the end furthest from the hinge mechanism 26, as shown), and being at their widest at the rear end. The fins 36 are supported close to the surface on which they rest by a pair of wheels 38 near the front end and by a second pair of wheels 40 near the rear end.

The rigid tube 32, at its lower end, has a dog-leg section 42, and at the bottom end of that section 42 the tube 32 extends in a horizontal direction through the suction head 34 below the crossbar 37. The portion of the rigid tube 32 within the suction head 34 is a half-pipe, its bottom half being cut away; the end of the rigid tube 32 is sealed; and the suction head 34 is connected to that portion of the rigid tube 32 by circular bearings 44 on either side (only one of which is shown in figure 3) so that the suction head 34 can turn about a horizontal axis Q relative to the lower arm 30.

In this embodiment the suction head 34 is also provided with fluidising water jets 46 near the front end. These would be connected to a narrow water pipe (not shown) running the length of the lower arm 30 and the upper arm 20 to an external water supply. In addition, the suction head 34 may be provided with a mesh cover (not shown) over the lower half of the half pipe within the suction head 34, to ensure that any large items of debris cannot be sucked into the apparatus 10.

Referring again to figure 2, the guide structure 22 includes a circular support plate 50 which rests on the mounting plate 24, and can rotate about an axis orthogonal to its own plane (by virtue of a roller bearing (not shown)), and longitudinal movement of the upper arm 20 is guided by eight roller bearings 52, four on either side of the guide structure 22.

When installing the apparatus 10, the guide structure 22 including the support plate 50 and the mounting plate 24 are installed first, but without the roller bearings 52 on one side. The support plate 50 defines a rectangular slot 54 which is 150 mm by 300 mm.

Considering the lower arm 30, the rigid tube 32 projects a short distance beyond the frame 28; this projecting end is then connected to a flexible hose 56 which extends alongside the upper arm 20. The apparatus 10 is then inserted through the slot 54 (which is large enough to accommodate the suction head 34), SO that the hose 56 passes through the slot 54 next to the upper arm 20. And the upper arm 20 is then held upright by installing the remaining roller bearings 52.

Thus in use the apparatus 10 is installed through a suitable aperture (the access hole 16) so the upper arm is upright; the top end of the upper arm 20 may be supported for example by a crane, or an A-frame and a chain block (not shown). The upper end of the hose 54 is connected to a suction pump (not shown) outside the tank 12, and the water pipe that supplies the water jets 46 is connected to a suitable water supply. The point S directly below the upper arm 20 (i.e. the point at which the longitudinal axis of the upper arm 20 intercepts the steel liner 14) is the centre of operation. By sliding the upper arm 20 longitudinally through the guide structure 22, and by turning the upper arm 20 about its own longitudinal axis, the suction head 34 can be moved to any position over a large area (about 13 m2 in this example) of the steel liner 14. Sliding the upper arm longitudinally moves the suction head 34 along radial paths towards or away from the centre of operation S, while turning the upper arm 20 about its longitudinal axis moves the suction head 34 along arcuate paths centred on the centre of operation S. Hence water and sludge can be removed from a large area of the bottom of the tank 12.

Since the wheels 38 and 40 are aligned for radial movement of the suction head 34, the preferred mode of operation is to move the suction head 34 along a radial line, and then back to the vicinity of the centre of operation S; then to turn through a small angle, and move along a slightly different radial line, and then back to the vicinity of the centre of operation 5; and repeating the steps until the desired area has been cleaned.

Where there are items of debris on the bottom of the tank 12 which are too large to be sucked up, the suction head 34 may be moved into a position on a radial line further from the centre of operation S than such an item of debris, and the suction head 34 can then be moved along a radial line, being used as a dredge to drag the item towards the centre of operation S. In this mode of operation the rear ends of the fins 36 push the item of debris along. It will be appreciated that an item of debris that is at or next to the centre of operation S is directly below the access hole 16, 50 it can subsequently be retrieved using conventional equipment.

Referring now to figure 4 there is shown a longitudinal sectional view of an alternative suction head 70 that may be used in place of the suction head 34 described above, and which has several features in common with it, identical features being referred to by the same reference numerals as in the suction head 34. In this case the suction head 70 consists of two parallel side plates 36 linked by a crossbar 72, and supported close to the surface on which they rest by a pair of wheels 38 near to the front end and by a second pair of wheels 40 near the rear end.

The crossbar 72 is generally box-shaped, defining an open-fronted chamber 74 that communicates with the bottom end of the rigid tube 32, the portion of the tube 32 within the suction head 70 extending across the width of the suction head 70, being sealed at the other side, and having a cutout 75 in its lower half. The chamber 74 comprises an upper plate 76 and a rear plate 77 connected to the side plates 36. The rear plate 77 extends along the underside to a position just behind the tube 32.

A base plate 78 extends forward from the front edge of the rear plate 77 along the underside, and there is an opening between the front edges of the upper plate 76 and the base plate 78, and these edges are linked by four spaced-apart generally triangular shaped front fins 80, each of which is a flat plate (parallel to the plane of the figure). Similarly there are four spaced-apart rear fins 82 projecting from the rear plate 77. An inclined mesh screen 84 extends from the front edge of the upper plate 76 to a position on the base plate 78 just in front of the tube 32; the base plate 78 defines a number of large circular apertures 86. The base plate 78 and the front fins 80 are welded to each other, and are connected by bolts to the front edge of the rear plate 77 and to the front edge of the upper plate 76; the front edge of the mesh screen 84 is secured by these same bolts.

A supply of water for fluidising any sludge is supplied through tubes 46 to a spray bar 88 mounted at the front of the mesh screen 84. The spray bar 88 defines a large number of small holes (e.g. 1 mm diameter) along its length, arranged to spray water down the front face of the mesh screen 84. In addition fluidising water can be supplied to a rear spray bar 90 mounted at the bottom edge of the rear plate 77 and arranged to produce water jets through small holes that are inclined so the water jets spray in a direction between downwards and forwards.

Thus in use the suction head 70 may be moved around the bottom of a tank 12 in the same way as described for the suction head 34, the sludge reaching the front face of the mesh screen 84 either through the gaps between the front fins 80 or through the apertures 86 in the base plate 78. The sludge is at least partly liquidised by the water spray from the spray bar 88, and is sucked through the mesh screen 84 into the chamber 74 and so extracted through the rigid tube 32.

It will be appreciated that the tank emptying apparatus 10, with the suction head 34, and the alternative suction head 70, are shown by way of example only, and that they may be modified in many different ways while remaining within the scope of the present invention. For example of there may be different numbers of fins; and in a context where a tank contains only sludge, so there is no requirement to drag objects, then the rear fins 82 may be omitted.

In particular, especially when the bulk of the material has been removed and there only remains small quantities of liquid and sludge on the base of the tank, the base plate 78 and the front fins 80, and the mesh screen 84, are removed. These are replaced by a generally L-shaped front plate (not shown), with a non-perforated front portion that extends down from the front edge of the top plate 76, and then a perforated or mesh portion extending along the underside, taking the place of the base plate 78. This is fixed using the same bolts as before. This ensures that the suction is greatest at the underside of the suction head 70.

Claims (10)

1. Claims 1. An apparatus for emptying material from a tank, the apparatus comprising an upper arm defining a longitudinal axis, a lower arm hingedly connected adjacent to one end to the upper arm and hingedly connected adjacent to the other end to a suction head, and a suction pipe extending from the suction head along the lower arm and the upper arm, the hinged connections being such that if the suction head is resting on a fixed surface orthogonal to the said longitudinal axis, movement of the upper arm parallel to its longitudinal axis causes the lower arm to turn about the connection to the upper arm.
2. 2. An apparatus as claimed in claim 1 wherein the suction pipe provides the structural element of the lower arm along at least the bulk of its length.
3. 3. An apparatus as claimed in claim 1 or claim 2 also comprising a guide block through which the upper arm extends, the guide block allowing the upper arm to be slid parallel to its longitudinal axis and to be rotated about its longitudinal axis.
4. 4. An apparatus as claimed in any one of the preceding claims wherein the suction head is provided with castors or wheels, so it can readily roll over a surface of the tank.
5. 5. An apparatus as claimed in any one of the preceding claims wherein the suction head is provided with fins whereby it may be used as a dredge.
6. 6. An apparatus as claimed in any one of the preceding -12 -claims wherein the suction head is provided with liquid injection nozzles to fluidise any adjacent sludge, and the apparatus comprises a liquid supply line to provide liquid to the liquid injection nozzles.
7. 7. An apparatus for emptying material from a tank substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.
8. 8. A method of emptying material from a tank by use of an apparatus as claimed in any one of the preceding claims.
9. 9. A method as claimed in claim 8 wherein the intersection of the longitudinal axis of the upper arm with the bottom surface of the tank is the centre of operation, and wherein the method entails repeated movements of the suction head along radial paths away from and towards the centre of operation, interspersed by movements of the suction head along arcuate paths centred on the centre of operation.
10. 10. A method as claimed in claim 8 or claim 9 wherein the intersection of the longitudinal axis of the upper arm with the bottom surface of the tank is the centre of operation, and there is solid debris in the tank that is too large to be extracted through the suction pipe, wherein the method comprises manoeuvring the suction head into a position radially beyond this debris, and then moving the suction head radially so as to drag the debris towards a position closer to the centre of operation.