GB2532956A

GB2532956A - Apparatus and method for removing a tank from the ground

Info

Publication number: GB2532956A
Application number: GB1421392.0A
Authority: GB
Inventors: Fitzgerald John
Original assignee: JSM CONSTRUCTION Ltd
Current assignee: JSM CONSTRUCTION Ltd
Priority date: 2014-12-02
Filing date: 2014-12-02
Publication date: 2016-06-08
Anticipated expiration: 2034-12-02
Also published as: GB201421392D0; GB2532956B

Abstract

An apparatus 30 for use in removing a tank 10 from the ground includes a drill bit 32 for drilling an annular void around the tank 10, the drill bit 32 including at least one 40 eye for aligning with an eye 24 in a tank 10 and for receiving a lifting bar therethrough. A plurality of eyes 40 at different axial positions along the drill bit 32 may be provided. The drill bit 32 may include a cylindrical wall 34 which may be a Bell Auger having teeth or milling picks at its end 38 and an Archimedes screw 36 welded to its outside. A coupling element 35 for a hydraulic rotating device may be provided. The lifting bar 42 may include a retaining clip comprising a latch 43 for locking the bar in position on the drill bit 32. A catch (45 fig. 6a) may hold the latch 43 in position. The tank may be an oil tank for electrical cables.

Description

APPARATUS AND METHOD FOR REMOVING A TANK FROM THE GROUND

The present invention relates to an apparatus and method for removing tanks from the ground, for example oil tanks for electrical cables.

Background

In the United Kingdom and around the world, significant lengths of electrical cable are underground, especially in built-up areas where it is difficult or undesirable to suspend cables from pylons.

Many of these underground electrical cables include oil under pressure to prevent the high voltage conductive core becoming inadvertently grounded.

In order to provide the oil under pressure, there are provided at various locations oil tanks which are coupled to the underground electrical cables and are pressurised in order to keep the oil in those underground cables at the appropriate pressure.

If necessary, it is possible to remove these tanks from the ground by digging a 20 trench and supporting the trench with steel braces while the tanks are removed.

Summary of the Invention

The present invention seeks to provide an improved apparatus and method for removing a tank from the ground.

According to an aspect of the invention, there is provided an apparatus for use in removing a tank from the ground, including a drill bit for drilling an annular void around a tank in the ground, the drill bit including at least one eye for aligning with an eye in a tank and for receiving a lifting bar therethrough.

Digging a deep trench and reinforcing it with steel braces as was previously done can be a difficult and expensive process. There can be safety risks of people falling into the trench, or objects falling upon people in the trench. Preferred embodiments are able to remove a tank from the ground without digging a large trench and therefore provide improvements in terms of health and safety risks.

Preferred embodiments can also be considerably quicker and more cost effective than previous methods.

The footprint of the works required for preferred embodiments of the invention can also be considerably less than for previous excavations, meaning less plant movement is required.

The at least one eye can include a plurality of eyes at different axial positions along a length of the drill bit.

The at least one eye can include a plurality of pairs of diametrically opposed eyes, each pair being at a different axial position along a length of the drill bit.

Each different axial position can be a distance from a drilling end of the drill bit corresponding to an axial distance of an eye from a base for a particular category of tank. Therefore, in embodiments of the invention, the same drill bit can be used for tanks of different lengths, since for any of a plurality of different lengths there will be an eye or a plurality of eyes than align with the eyes of the tank for placing a lifting bar therethrough.

The drill bit preferably includes an Archimedes screw. The Archimedes screw can mean that a void around the tank is cleared of material, enabling the tank to easily be pulled out of the ground with minimal resistance.

According to an aspect of the invention, there is provided a kit for removing a tank from the ground, including: an apparatus as above; and a lifting bar for inserting through an eye of the drill bit and an eye of a tank.

The lifting bar preferably includes a retaining clip for locking the bar in position when inserted through the drill bit.

According to an aspect of the invention, there is provided a method of removing a tank from the ground, including: drilling an annular void around the tank using a drill bit with at least one eye therein; aligning at least one eye in the tank with at least a first eye of the drill bit; inserting a lifting bar through the first eye of the drill bit and the at least one eye of the tank in order to link the drill bit to the tank; lifting the drill bit thereby lifting the tank so that the tank is removed from the ground.

Brief Description of the Drawings

Preferred embodiments of the invention are described below, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional view of an area of ground in which an apparatus according to an embodiment of the invention is being used in removing a tank from the ground; Figure 2 is a cross-section of the same area of ground as Figure 1 after the tanks has been removed and the void refilled according to an embodiment of the invention; Figure 3 is an artist's impressions of an apparatus according to an embodiment of the invention being used; Figure 4 is a schematic side view of a drill bit according to an embodiment of the invention; Figure 5a and b show a lifting bar for use in embodiments of the invention in an open position; and Figure 6a and b show a lifting bar for use in embodiments of the invention in a closed position.

Pressurised oil tanks are located, generally under the ground, for pressurising oil-filled cables. These oil tanks are generally buried deep underground, in cement bound sand, and accordingly are very difficult to repair.

Many oil tanks are becoming redundant as many newer cables do not use oil to provide insulation.

Furthermore, there is a risk of oil tanks leaking, especially for older tanks. This can be an environmental risk since the oil can be environmentally damaging, and is a particular risk where the tanks are located near water extraction zones.

Because the tanks are generally buried underground, it can be difficult to spot leaks from the tanks visually.

It can therefore be a risk to abandon or decommission tanks because of the potential environmental impact of an oil leak, and consequently abandoned tanks need to be monitored.

As mentioned above, it is possible to remove tanks from the ground. However, this can be a difficult process since the tanks are generally buried very deep, with 30 the base of the tank often being up to 4.5m below the surface of the ground. It is therefore often necessary to dig a very deep trench and support this trench with steel braces to prevent it collapsing while the oil tank is removed. However, digging a trench up to 4.5m deep and reinforcing it with steel braces can be a difficult and expensive process. It also can have safety risks of people falling into the trench, or objects falling upon people in the trench.

An improvement to this method can be made by embodiments of the invention. One such embodiment is shown in Figure 1.

Often, oil tanks are buried in close proximity in groups. One such group is shown in Figure 1. Although only four tanks are shown in Figure 1, groups can contain up to 32 tanks.

Figure 1 shows a plurality of oil tanks 10 which are buried in the ground 12.

In Figure 1, a small trench 14 about lm deep has been dug in order to expose a top 16 of each of the tanks 10. However, before digging the trench 14, the tops 16 of each of the tanks would be buried about lm below the surface 18 of the ground 12.

There are several different categories of oil tanks which are generally used.

These tanks are all cylindrical and have the same diameter, which is typically about 750mm. However, the different categories of tank have different lengths and therefore different volumes. The category of tank therefore affects how deep below the surface of the ground a base of the tank is located. Figure 1 shows tanks of the largest volume category in which the bases 20 of the tanks 10 are located up to 4.5m below the surface 18 of the ground 12. These tanks have a length of 3.2m from top to base.

An outer shell of the tanks 10 is a tube of concrete or concrete spun pipe which houses an oil storage element within it. Typically, the oil storage element is a metal container and the tank is lined with bitumen between the concrete tube and the metal container to inhibit corrosion of the metal container. The top 16 of the tank 10 is a hollow concrete tube or lip extending above a top of the oil storage element. In other words, the oil storage element extends from the base 20 of the tank 10 to a storage top 22 which is below the top 16 of the tank 10.

The top 16 of the tank 10 includes a pair of diametrically opposed eyes 24 in the concrete tube. It is through these eyes 24 that an oil pipe is passed when the tank is in use to connect the electrical cables to the tank. As described above, the top 16 of the tank is a hollow concrete tube above the top of the oil storage element, and therefore a straight line can pass through each of the eyes 24 in the top 16 of the tank 10 without obstruction.

Figure 1 also shows an apparatus 30 for removing a tank 10 according to an embodiment of the invention. In Figure 1, the apparatus 30 is shown removing the left-most tank 10a.

The apparatus 30 includes a drill bit 32 for drilling an annular void around the tank 10a. In this embodiment, the drill bit 32 includes a hollow substantially cylindrical drill bit wall 34 with an Archimedes screw 36 provided around the outer circumference of the drill bit wall. The drill bit wall can be a Bell Auger and the Archimedes screw can be welded to the outside of the Bell Auger.

In this embodiment, a coupling end of the drill bit 32 includes a coupling element which can be a standard coupling element for coupling to a drill such as a hydraulic rotating device.

In this embodiment, a drilling end 38 of the drill bit wall 34 is provided with cutting teeth or milling picks, preferably carbide tipped, in order to loosen the ground around the tank 10a to allow the drill bit 32 to be advanced over the tank.

The drill bit wall 34 includes a plurality of eyes 40 therethrough. Each of the eyes 40 is part of a pair, with a first eye 40 of each pair being diametrically opposite a second eye of that pair. Both eyes of a given pair are at the same axial distance from the drilling end 38. Each pair of eyes is located at a different axial distance from the drilling end 38 so that when the drilling end 38 of the drill bit 32 is aligned with the base 20 of the tank 10a, a pair of the eyes 40 can align with the eyes 24 in the tank.

In this embodiment, the drill bit is substantially 3.2m long, substantially the same as the largest category of tank so that the drill bit can completely slide over any category of tank. However, the length of the drill bit can be selected for the category of tank being removed. Preferably, the drill bit is at least as long as the tank being removed.

In order to make the drill bit useable with different categories of tank, the pairs of eyes 40 are provided at distances from the drilling end 38 which correspond to the distance of the tank eyes 24 from the tank base 20 for the different categories of tank. Accordingly, when the drill bit is placed over a tank, the eyes 40 corresponding to that category of tank can be aligned with the eyes 24 of the tank.

Figure 4 shows the schematic side view of a drill bit 132 according to another embodiment of the invention. As can be seen from Figure 4, the drill bit 132 includes a plurality of eyes 140 at different axial distances from a drilling end 138 of the drill bit 132.

As can be seen in Figure 4, certain distances are marked, although it will be appreciated that the distances are not to scale with each other.

In the embodiment of Figure 4, a first eye 140a is located at an axial distance of about 1.2 metres from the drilling end 138. A second eye 140b is located at an axial distance of about 1.72 metres from the drilling end 138. A third eye 140c is located at axial distance of about 2.15 metres from the drilling end 138. In this embodiment each eye 140 is one eye of a pair, the other eye of the pair being at a diametrically opposite point of the drill bit.

The eyes 140 are each arranged to correspond to the height of eyes of different categories of tanks so that the drill bit 132 can be used with any of the three categories of tanks corresponding to the three pairs of eyes provided in the drill bit 132 In the embodiment of Figure 1, the drill bit 32 is longer than in the embodiment of Figure 4. The drill bit of Figure 1 can include the arrangement of eyes as in Figure 4 but with an additional pair of eyes at an axial distance from the drilling end 38 of about 3 metres for use with the largest category of tank shown in Figure 1. It is to be appreciated that the positioning of the eyes is not clearly represented in the schematic drawing of Figure 1.

Referring again to Figure 1, the eyes 40 have a diameter preferably substantially equal to that of the eyes 24 of the tank. However, in all embodiments, the eyes 40 have a diameter at least as great as a diameter of a lifting bar 42, which is typically 50mm, which can be used to link the drill bit 32 to a tank by insertion through a pair of eyes 40 of the drill bit and the eyes 24 of the tank.

The lifting bar 42 is a solid bar, typically steel, capable of withstanding the weight of a tank, typically capable of withstanding a weight of 1 ton. At either end the bar is provided with a retaining clip which can be positioned in an open position to allow the end of the bar to pass through the eye, or a closed position to prevent the end of the bar passing through an eye. The bar could therefore be said to be a safety pin.

Figures 5a and 6a show schematic diagrams of one end of the lifting bar 42. Figure 5a shows the end of lifting bar in an open position and Figure 6a shows the end of a lifting bar in the closed position. The bar is typically about 50mm in diameter and about 900mm in length.

As can be seen, the retaining clip 41 includes a pivoted latch 43, or flop over plate, 5 and a catch 45. The latch 43 preferably has a length greater than the diameter of the bar 42 and greater than a diameter of the eyes of the tank and drill bit. The latch is pivoted about a pivot 47 which is at or near an outer perimeter of the bar 42 at or near the end of the bar so that in the open position the latch extends longitudinally beyond the end of the bar. The latch 43 forms an angle 49 with the end of bar 42. The pivot 47 is configured to prevent the angle 49 from significantly exceeding 90°. In other words, the pivot 47 allows the latch 43 to move freely between an angle 49 of about 0° and about 90°.

The catch 45 is configured to allow the latch 43 to pass in a direction of decreasing angle 49, but not in a direction of increasing angle 49. In other words, the catch is configured to allow the latch 43 to pass in a direction towards the end of the bar 42 but not in a direction away from the bar 42. This can for example be achieved by the catch 45 including a member with a free end angled towards the end of the bar which can be displaced by the latch 43 when moving in an angle of decreasing angle but which after the latch has passed springs back into position and prevents movement of the latch 43 in a direction of increasing angle 49.

In use, the bar 42 is oriented so that the pivot 47 is on a lower side of the bar in order for the weight of the latch 43 to hold the latch at a large angle 49 from the bar 42 so that the latch 43 is disposed in a substantially longitudinal direction.

Once it is desired to lock the latch, the bar 42 can be rotated about its longitudinal axis so that the pivot 47 is on an upper side of the bar 42. The weight of the latch 43 causes this to fall in a direction of decreasing angle 49 where it is caught by the catch 45 and held in a closed position as shown in Figure 6a. The latch 43 is of sufficient length to extend transversally beyond the outer perimeter of the bar 42 and can prevent the bar 42 from being withdrawn through an eye.

A clip similar to the clip shown in Figures 5a and 6a is also provided at the other 5 end of the bar 42 and preferably on the same side of the bar so that the clips are both in the open position in the same orientation of the bar and rotation of the bar simultaneously closes both clips.

Figures 5b and 6b show, respectively, the lifting bar 42 in the open position and in the closed position. Only one end of the bar is shown with retaining clips in Figures 5b and 6b, although in practice both ends are generally provided with such clips.

In use, the trench 14 is dug to expose the top 16 of the tank 10a or group of tanks which it is desired to remove.

The oil cables coupling the tank to the electrical cables are then disconnected from the tanks. In some methods, the tanks can be depressurised. However, in general tanks are not depressurised to below 1 atmosphere so that they do not suck in moisture or other materials from the atmosphere.

The drill bit 32 is coupled to a drill 44. In this embodiment, the drill 44 is coupled to an excavator 46 capable of lifting at least two tons. The drill can be a hydraulic rotating device which are commercially available In one embodiment, a torque head is used producing 40 ton of torque.

The drill bit 32 is aligned over the top 16 of the tank 10a to be removed.

The drill 44 is operated to rotate the drill bit 32 and the drill bit 32 is pressed down over the top 16 of the tank 10a in order to drill an annular void around the tank 10a.

As the drilling proceeds, the Archimedes screw displaces soil or other material from around the tank and lifts the soil or material to the surface thereby to clear the void. In the preferred embodiment the drill bit is configured to clear a void of about 50mm around the tank.

Drilling is continued until the drilling end 38 of the drill bit 32 substantially aligns with the base 20 of the tank 10a, and the eyes 24 of the tank substantially align with the eyes 40 in the drill bit which correspond to the category of tank being removed.

The lifting bar 42 with the retaining clips in the open position is then inserted through a first eye 40 of the pair of eyes in the drill bit that has aligned with the eyes of the tank, through the eyes 24 of the tank, and through the second eye 40 of the pair of eyes in the drill bit 32.

The lifting bar 42 is locked to the drill bit for example by rotating the lifting bar to close the retaining clips at either end of the lifting bar as described above.

The drill bit 32 is thus locked to the tank 10a.

The excavator 46 is operated to provide a vertical lifting force to the drill bit.

This vertical lifting force is transferred to the tank via the lifting bar which is positioned through eyes of the drill bit and the tank.

Since the drill bit, in particular through the use of the Archimedes screw, has cleared a void around the tank, the vertical lifting force is easily able to lift the tank out of the ground vertically upwards and thereby to remove the tank from the ground.

In some embodiments, the excavator can be gimballed in order that the drill bit can pivot about its coupling to the excavator. This can mean that the excavator once it has removed the tank from the ground can rotate the tank through 900 when placing it down, for example to lie it down on its side on a truck for transporting the tank elsewhere.

Immediately after removing the tank from the ground, a filler material 50 is inserted into the void left by the tank in order to prevent anything or anybody from falling into that void, and in order to prevent the void from collapsing. This is shown in Figure 2. Examples of filler material that can be used are pea shingle or rapidly setting foam concrete. Pea shingle is advantageous as it is self-compacting which eliminates the need to enter the excavation.

If a neighbouring tank in a group of tanks is also to be removed, the filler material should be left to securely strengthen the void before the neighbouring tank is removed. In such a situation, rapid setting concrete is preferred as a filler material to secure the void. Once the void is secure, the neighbouring tank can be removed using the same method as above.

The method described herein means that it is not necessary to dig a deep reinforced trench with the potential associated health and safety risks In other words, it avoids heavy duty shoring.

Furthermore, the footprint of the works during removal of a tank is much smaller, minimal back fill is required, and there are less plant movements.

The method can be more than 50% faster and more cost effective than previous methods.

In addition, it is at no point necessary for any individual to enter the excavation, and the void is only exposed for a very short time between the tank being removed and the filler material being added.

It is also not necessary to remove a large amount of earth from the ground, with consequent storage issues, in order to remove the tank since only a small void around the tank needs to be removed in order to remove the tank.

Various modifications can be made to the above embodiments.

In some embodiments, it is not necessary for the drill bit 32 to be provided with a plurality of pairs of eyes 40. Instead of pairs of eyes as described above, the drill bit 32 can be provided with eyes each having a diametrically opposed bar support so that the lifting bar can be inserted through a chosen eye 40 of the drill bit 32, through the eyes 24 of the tank, and into the bar support diametrically opposite the chosen eye 40 of the drill bit 32 in order to link the tank to the drill bit 32. The bar support can be configured to prevent the supported end of the bar moving upward beyond the bar support in response to a vertical upward force being applied to the bar.

It is not necessary for the drill bit to be continuous. There can be provided for example longitudinal or helical gaps in the drill bit provided they are not at the locations where an eye or bar support need to be located.

Although in the method described above, a filler material is inserted into the void left by the tank immediately after removing the tank, this is not necessarily in all embodiments. In some embodiments, a new tank can be inserted into the void to replace the old tank, and then reconnected to the oil cables that were disconnected from the removed tank. In other embodiments, a liner, such as a concrete liner, can be inserted in order to secure the void to prevent it collapsing, but to keep it as an open hole rather than filling it.

All optional and preferred features and modifications of the described embodiments and dependent claims are usable in all aspects of the invention taught herein. Furthermore, the individual features of the dependent claims, as well as all optional and preferred features and modifications of the described embodiments are combinable and interchangeable with one another.

Claims

CLAIMS1. An apparatus for use in removing a tank from the ground, including a drill bit for drilling an annular void around a tank in the ground, the drill bit including at least one eye for aligning with an eye in a tank and for receiving a lifting bar therethrough.
2. An apparatus according to claim 1, wherein the at least one eye includes at least one pair of diametrically opposed eyes for receiving a lifting bar therethrough.
3. An apparatus according to any preceding claim, wherein the at least one eye includes a plurality of eyes at different axial positions along a length of the drill bit.
4. An apparatus according to any preceding claim, wherein the at least one eye includes a plurality of pairs of diametrically opposed eyes, each pair being at a different axial position along a length of the drill bit.
5. An apparatus according to claim 3 or 4, wherein each different axial position is a distance from a drilling end of the drill bit corresponding to an axial distance of an eye from a base for a particular category of tank.
6. An apparatus according to any preceding claim, wherein the drill bit is for drilling an annular void with an inner diameter substantially equal to an outer diameter of a tank.
7. An apparatus according to any preceding claim, wherein a length of the drill bit is at least as great as a length of a tank to be removed.
8. An apparatus according to any preceding claim, wherein the drill bit includes an Archimedes screw.
9. An apparatus according to any preceding claim, wherein the drill bit includes a substantially cylindrical drill bit wall.
10. A kit for removing a tank from the ground, including: an apparatus according to any preceding claim; and a lifting bar for inserting through an eye of the drill bit and an eye of a tank.
11. A kit according to claim 10, wherein the lifting bar includes a retaining clip for locking the bar in position when inserted through the drill bit.
12. A kit according to claim 10 or 11, including an excavator for lifting the drill bit.
13. A kit according to claim 10, 11 or 12, including a drill for rotating the drill bit.
14. A method of removing a tank from the ground, including: drilling an annular void around the tank using a drill bit with at least one eye therein; aligning at least one eye in the tank with at least a first eye of the drill bit; inserting a lifting bar through the first eye of the drill bit and the at least one eye of the tank in order to link the drill bit to the tank; lifting the drill bit thereby lifting the tank so that the tank is removed from the ground.
15. A method according to claim 14, wherein inserting the lifting bar includes inserting the lifting bar through the first eye of the drill bit, the at least one eye of the tank and a second eye of the drill bit, the second eye being diametrically opposite the first eye.
16. A method according to any of claims 14 to 15, wherein inserting the lifting bar includes closing a retaining clip of the lifting bar to prevent the lifting bar detaching from the drill bit.
17. A method according to any of claims 14 to 16, wherein the at least one eye of the tank includes first and second eyes.
18. A method according to any of claims 14 to 17, including excavating a top of the tank to expose the at least one eye of the tank.
19. A method according to any of claims 14 to 18, including filling a hole left by the tank after its removal with a filler material.