WO2014057456A2

WO2014057456A2 - Method and apparatus for inserting an elongate member into the ground

Info

Publication number: WO2014057456A2
Application number: PCT/IB2013/059274
Authority: WO
Inventors: John Reid; Zoran Jelic
Original assignee: Calordomus Limited
Priority date: 2012-10-11
Filing date: 2013-10-10
Publication date: 2014-04-17
Also published as: GB201218295D0; WO2014057456A3

Abstract

An apparatus for inserting an elongate member into the ground, comprises a barrel 102 having a bore for receiving the member 130 to be inserted into the ground,. A piston 134 is slidable along the bore of the barrel 102 to ram the member into the ground, and a breech 140 closes off end of the barrel on the opposite side of the piston from the member to form a chamber for receiving a charge 136 that is ignitable to generate a high gas pressure within the chamber. The barrel is pivotably mounted on a frame 16 for rotation between a vertical deployed position for ramming the member into the ground and an inclined loading position for inserting of the elongate member 130 into the bore of the barrel 102. The frame is weighted or anchored to the ground to withstand the reaction force on the barrel as the member is rammed into the ground by ignition of the charge.

Description

METHOD AND APPARATUS

FOR INSERTING AN ELONGATE MEMBER INTO THE GROUND

Field of the invention

The present invention relates to an apparatus and method for inserting an elongate member into the ground. The apparatus and method find application in the insertion of a tube into the ground, to form part of a ground source heat exchanger, or in driving any form of post into the ground.

Background of the invention

Ground source heating and cooling systems rely on a heat exchanger that is buried in the ground. Different prior art proposals have used heat exchangers comprising both horizontally and vertically buried pipes for extracting heat from the ground. Horizontal installation requires digging a trench and burying a flexible pipe. Such installation is very labour intensive and requires large areas of land.

Vertical heat exchanger pipes for a ground source heating system have conventionally been installed by drilling a hole, then lowering a U-tube into the hole. The drilling operation, as well as being noisy, time consuming and expensive, is messy as it brings large amounts of debris to the surface.

Object the invention

The aim of the invention is provide an apparatus that can insert elongate members, such as pipes and posts, into the ground with less upheaval than drilling.

Summary of the invention

According to an aspect of the present invention, there is provided an apparatus for inserting an elongate member into the ground as set forth in claim 1 of the appended claims.

According to a second aspect of the present invention, there is further provided a method of driving a pipe made of modular sections into the ground as set forth in claim 13 of the appended claims. Brief description of the drawings

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a schematic representation of an indirect ground source heating system,

Figure 2 is a similar schematic representation of a direct ground source heating system,

Figure 3 is a schematic representation of an apparatus for installing a ground heat exchanger having the form of a pyrotechnic pneumatic ram

Figure 4 is a section through the apparatus of Figure 3 taken in the plane IV-IV,

Figure 5 is a schematic section through an installed ground heat exchanger,

Figure 6 shows a rear view of an alternative design of an apparatus for installing a ground heat exchanger,

Figure 7 is a section through the lower end of the apparatus of Figure 6 drawn to an enlarged scale, and

Figure 8 is a section through the upper end of the apparatus of Figure 6 drawn to an enlarged scale.

Detailed description of an embodiment

In Figure 1, a heat pump is formed by a circuit 10 shown in heavy lines, through which a refrigerant flows. The heat pump circuit 10 comprises an evaporator 12, a compressor 14, a condenser 16 and an expansion valve 18. The evaporator 12 is a heat exchanger having primary and secondary coils of which the secondary coil forms part of the heat pump circuit 10 and the primary coil is connected in circuit with a ground heat exchanger 30, formed of pipes buried underground. A pump (not shown) circulates a liquid, typically a water and glycol mixture, through the ground heat exchanger 30 and the primary coil of the evaporator 12.

The condenser 16 is also a heat exchanger with primary and secondary coils. In this case, the primary coil forms part of the heat pump circuit 10 and the secondary coil is connected in circuit with central heating pipes and radiators 20 serving to heat the space within a building. In operation, heat extracted from the ground is used in the evaporator 12 to heat and evaporate the refrigerant circulating in the heat pump circuit 10. The refrigerant is then compressed by the compressor 14 to raise its temperature and pressure. In the condenser 16, the refrigerant releases heat to the central heating system 20 before it returns by way of the expansion valve 18 to the evaporator 12.

Such a system is termed "indirect" because the liquid circulating through the ground heat exchanger is not the refrigerant of the heat pump 10 and only heats the refrigerant indirectly. As earlier stated, the liquid circulating through the ground heat exchanger is typically a mixture of water and glycol, the latter acting as an antifreeze.

An alternative /'direct", system is shown in Figure 2 which differs from that shown in Figure 1 in that there is no separate evaporator heat exchanger 12. Instead, the ground heat exchanger 30 forms part of the heat pump circuit 10 and is designated 30/12as it also doubles as the evaporator 12 of Figure 1, so that the heat pump refrigerant picks up ground heat directly.

Both types of system have their merits and limitations and the method of installation of the invention may be applied to either type of system. Direct heating systems are nevertheless preferred as they are more efficient and the installation method of the invention mitigates many of the disadvantages normally associated with direct systems.

The ground heat exchangers represented schematically in Figures 1 and 2 are both shown as being tubes inserted vertically into the ground. Such a generally vertical orientation is used in the present invention because it allows installation to be carried out more quickly and economically and also with less mess and

disturbance to the building occupier. Furthermore, the method may be implemented using relatively portable equipment that can be brought easily to the installation site, even when access is restricted.

A first apparatus that may be used for installing a ground heat exchanger 30 is shown in Figures 3 and 4 of the accompanying drawings. The apparatus is essentially a pyrotechnic pneumatic ram that generates at high pressure to drive a tube a fixed distance into the ground by means of a chemical reaction that takes place in a sealed chamber at the end of a barrel. The chemical reaction is preferably combustion of solid rocket propellant, but may be ignition of gun powder, black powder or other gas generating compounds.

The apparatus comprises a barrel 50 is reinforced by means of two concentric sleeves 52, 54 the outer sleeve 54 having trunnions 56. In the illustrated

embodiment, the barrel 50 is pivotably supported by the trunnions 56 in two blocks 58 that are slidably supported by means of hydraulic cylinders 60 in two vertical channels 62 that are held down on the ground by a base 64. The base 64 is itself either secured to the ground by suitable ground anchors or is weighted down sufficiently to able to withstand the reaction or recoil force on the barrel 50. The reaction force is transmitted to the base 64 by damper cylinders 66 secured to the channels 62. A sliding breech 68 closes off a sealed chamber at the top end of the barrel that receives a fuel cartridge case 70. A piston 72 acts as a movable wall of the sealed chamber and applies a downward force to the upper end of the tube 80 that is to be driven into the ground when a charge is ignited in the sealed chamber.

The tube 80 is inserted into the barrel 50 from its lower end and is fitted with a pointed cap 82 having a slightly greater maximum diameter than the tube 80. The purpose of this is to decrease the amount of surface contact and therefore friction between the outer surface of the tube and the hole it is sliding through, previously displaced by the cap 82. The tube passes through a ground plate 84 that is pressed against the ground by being clamped between the ground and the lower end of the barrel 50, when the latter is lower by means of the hydraulic cylinders 60, 62. A stop or buffer 86 is provided near the lower end of the barrel 50 to arrest the movement of the piston 72 in order to limit the depth of penetration of the tube 80 into the ground.

The tube 80 to be driven into the ground, which may need to have a length of some 30m (or more in the case of an indirect heating system) is made up of sections of about 2m in length that are driven into the ground one at a time.

For insertion of each section, in the case of the embodiment of the apparatus shown in Figure 3, the barrel 50 is first raised from the ground by the hydraulic cylinders 60, 62 and rotated about the trunnions 56 into a horizontal position in which both of its ends can easily be reached. A cartridge 70 is loaded into one end of the barrel 50 and the tube 80 is slid into it from its lower end. For the first tube section only, after the ground plate 84 is fitted over the end of the tube 80, a pointed cap is screwed , welded or otherwise affixed to the end of the tube.

The barrel 50 is then rotated about the trunnions 56 to point downwards, into a generally vertical position, and lowered to the ground by the hydraulic cylinders to trap the ground plate 84 and force the pointed tip 82 into the ground.

Apparatus that does not require rotation of the barrel within a frame are alternatively possible. Such alternative apparatus may allow loading of the tube section into the barrel through the breech end of the barrel.

The gas and pressure generating propellant is then ignited to generate a very high pressure in the sealed chamber at the top of the barrel, thereby forcing the tube 80 into the ground. The tube 80 continues to be driven into the ground until the plunger 72 is arrested by the stop 86.

At the same time as forcing the tube 80 into the ground, an equal and opposite force is applied to the barrel 50 acting to move it upwards. The recoil of the barrel is absorbed by the dampers 66 and the force acting upwards on the channels 62 is resisted by the weighting or anchoring of the base 64 to the ground.

The pyrotechnic pneumatic ram does not launch the tube into the ground but pushes using a piston that remains in contact with the end of the tube at all times. In this way, the apparatus controls the depth of penetration of the tube with each charge that is fired. By combining rocket propulsion with gun propulsion, the ram offers greater control in that the pressure rise in the sealed chamber is more gradual, and venting of the produced combustion gases can serve to generate a counter-recoil force.

It should be emphasised that the plunger remains in contact with the tube from prior to ignition of the charge, during the driving period where the tube displaces the earth around it until after the point where the piston is arrested to prevent the tube from being driven too far into the ground. This is important because the tube is inserted into the ground in modular sections until a total desired length is achieved. It is therefore essential to be able to access the upper end of a tube section after it has been driven into the ground to allow it to be joined the next section. The upper exposed end of each inserted tube section may remain above ground level after it has been driven into the ground. For the purposes of aesthetics, it may be desirable to excavate the ground around which the tube is to be inserted so that the resulting exposed tube can be re-buried when plumbed so that the installation remains invisible.

In other proposed embodiments, additional bracing may be connected directly or indirectly to the barrel. Available options are ground anchors that tether the barrel to the ground, although these are unsuitable when the ground surface is predominantly concrete. In such situations, the barrel may be supported either directly or indirectly by a platform for receiving additional weights. Preferably the platform supports either a bag or tank suitable for storing the large volumes of water that would be required to resist the recoil force on the barrel. In addition the use of water as a weight which may be pumped in and out, makes the apparatus more easily collapsible and mobile.

To insert each subsequent tube section, the barrel 50 is raised by the hydraulic cylinders 60 to clear the top of the tube section last inserted into the ground and is again rotated into a horizontal position to receive the next tube section through its lower end and a fresh cartridge at its upper end. The insertion of the next tube section moves the piston 72 back to the upper end of the barrel.

The barrel 50 is now rotated once again to its vertical position and the tube section 80 disposed within the barrel 50 is securely and permanently attached, preferably by screwing or welding, to the tube section(s) that have previously been inserted into the ground. A further chemical reaction is now initiated to drive the new section of tube into the ground and the process is repeated until the tube in the ground achieved the desired depth.

Because the pointed cap 82 has a slightly larger diameter that the tube 80, the hole in the ground that it creates is wider than the tube so that the latter does not encounter an increasing frictional resistance as it is driven into the ground. However, after insertion of the tube is completed, the ground will in time expand under its own pressure to close the gap surrounding the tube and make good thermal contact with the tube. Should this fail to happen, the gap between the surrounding the tube could be filled with viscous fluid, that will harden with passing of time. The ground heat exchanger requires two conduits with the coolant or refrigerant flowing down through one and up through the other. These two conduits may suitably be concentric. Instead of being formed by two separate pipes, they are formed by one pipe inside the other, as shown in Figure 5.

After insertion of the outer tube 80 into the ground, an inner tube 90 is lowered into it to divide the outer tube 80 into two fluid flow paths of preferably approximately equal cross-sectional area. Liquid is pumped into the tube 90 via a control valve 96 and after flowing to the bottom of the tube 80 flows back up through the annular space between the tubes 80 and 90.

Figures 6 to 8 show in more detail an alternative design of a pyrotechnic pneumatic ram that differs from that shown in Figures 3 and 4. The pneumatic ram 100 in Figures 6 to 8 has a barrel 102 supported by trunnions 104 in a frame 106 made up of iron girders. In this embodiment, the barrel 102 is not reinforced by separate sleeves and its trunnions 104 are directly secured to the frame 106 instead of being mounted on hydraulic cylinders. Thus, the barrel 102 can be rotated about the trunnions 104 but cannot be raised or lowered in the frame 106. As will be described in greater detail with reference to Figure 7, the lower end of the barrel 102 is spaced from the ground by an anvil 108 and a damper 110 is arranged at the lower end of the barrel 102.

The frame 106 is constructed of vertical pillars 114 that are strengthened by means of cross braces 112. At the lower end, the pillars 114 are connected to horizontal girders 116 which form a platform supporting heavy blocks 118 , or water tanks, the weight of which opposes the reaction force on the barrel 102. The blocks 118 are preferably made of a very dense material, such as lead, in order to minimise the volume that they occupy during transportation.

As can be seen from Figure 7, the frame 106 includes a ground plate 120 having a central hole 122 in the position where a tube is to be inserted into the ground. The anvil 108 is a heavy metal block formed of two halves that are intended to be placed around the end of the tube 130 that is to be driven into the ground. The dumper 110 arranged below the lower end of the barrel 102 is made up of Belleville springs and its purpose is to arrest the piston acting to drive the tube 130 into the ground. Referring now to Figure 8, which shows the upper end of the barrel 102, the tube to be driven into the ground is connected to a plunger 132 that is itself connected to, and me regarded as part of, a piston 134 of greater outside diameter 5 down the tube 130. A propellant charge 136 is mounted for movement with the

piston 134 and is retained against the piston by a perforated plate 138 that also moves with the piston 134. The breech 140 in this case is screwed into the end of the barrel 102. l o From the above description, it will be seen that this embodiment of the

apparatus differs from that of Figures 3 and 4 in the following respects :

(i) a screw breech is used in place of a sliding breech,

(ii) the barrel has only a single wall without sleeve reinforcements,

(iii) a damper is arranged at the lower end of, and outside, the barrel to 15 absorb the momentum of the descending piston in place of the hydraulic cylinders

66,

(iv) an anvil is placed below the lower end of the barrel, avoiding the need for lifting cylinders 60, and

(v) the piston has a plunger extension.

20

The apparatus of Figures 6 to 8 operates as follows. For the first tube section to be inserted into the ground, the barrel 102 is rotated about the trunnions 104 into a horizontal position. For this to be possible, it is necessary first to loosen bolts 142 that hold the damper 110 tight against the anvil 108. While the barrel 102 is

25 horizontal, the tube 130 is fed into it and connected at one end to the plunger 132 of the piston 134. A propellant charge 136 is secured to the upper face of the piston 134 and held in position by means of the perforated plate 138. The breech 140 is then screwed into place. The barrel is next rotated into a vertical position in which the lower end of the tube 130, after having been fitted with a pointed cap, is aligned with

30 the hole 122 in the base plate 120. The two halves of the anvil 108 are next

positioned about the tube 130 and the bolts 142 are tightened to clamp the damper 110 that is attached to the barrel 102, down against the anvil 108.

The propellant charge 136 is next ignited to drive the piston 134 downwards 35 and force the tube 130 ahead of it into the ground. On reaching the lower end of the barrel 102, the piston 134 collides with the Belleville springs of the damper 110 and is brought to a gradual stop. The secure connection between the damper 110 and the barrel 102 reduces the recoil force on the barrel. The lower end of the plunger 132 will at the end of the stroke of the piston 134 be approximately level with the surface of the ground. After reduction of the gas pressure in the combustion chamber of the barrel, the Belleville springs will again expand to raise the piston 134 slightly thereby separating the plunger 132 from the tube 130 that has been inserted in the ground.

In order to insert the next tube section, the bolts 142 are released and the halves of the anvil 108 are removed to allow the barrel 102 to be rotated for connection of the upper end of the next tube section to the plunger 132. At the same time, a new propellant cartridge is fitted to the piston 134. The barrel 102 is next rotated back into a vertical position and the tube sections are secured to one another, preferably by the use of a screw thread connection and suitable O-rings, though alternatively they may be among others, welded, pressed or compression fitted to each other. The two halves of the anvil 108 are then assembled around the tube 130 and the bolts 142 art tightened in readiness for the next firing.

While the apparatus of the invention has been described above by reference to the installation of a ground heat exchanger, it will be clear that the apparatus may be used to insert other pipes into the ground, for example for well bore holes, or for inserting solid post into the ground, for example in the installation of fencing or ground reinforcement piles.

Claims

1. An apparatus for inserting an elongate member into the ground, comprising

a barrel having a bore adapted to receive the member to be inserted into the ground, the barrel being weighted or anchored to the ground,

a piston slidable along the bore of the barrel and having one side operative to contact elongate member, and

a breech closing off an end of the barrel on the opposite side of the piston from the elongate member to define with the piston a variable volume chamber for receiving a charge that is ignitable to generate a high gas pressure within the chamber,

characterised in that gas pressure generated by ignition of a charge within the chamber acts on the piston to cause the piston to push the elongate member into the ground while remaining in contact with the elongate member, and

a stop is provided to limit the stroke of the piston and thereby limit the degree of penetration of the elongate member into the ground.

2. An apparatus as claimed in claim 1, wherein the stop includes a spring damper.

3. An apparatus as claimed in claim 1 or 2, wherein the barrel is mounted on a frame for pivotable movement between a vertical deployed position and a horizontal or inclined loading position.

4. An apparatus as claimed in any preceding claim, wherein the barrel is movable vertically by means of hydraulic cylinders.

5. An apparatus as claimed in any of claims 1 to 3, wherein the barrel is vertically fixed and an anvil is provided between the end of the barrel and the ground to act as the stop.

6. An apparatus as claimed in claim 5 wherein the anvil is formed of separable parts.

7. An apparatus as claimed in claim 5 or 6, wherein the anvil is clamped between the barrel and a ground plate that forms part of a frame supporting the barrel.

5 8. An apparatus as claimed in any preceding claim, wherein a plunger is provided on the piston for engaging and radially retaining an end of the elongate member.

9. An apparatus as claimed in any preceding claim, wherein the breech is0 a screw breech.

10. An apparatus as claimed in any of claims 1 to 8, wherein the breech is a sliding breech. 5

11. An apparatus as claimed in any preceding claim, further characterised by a platform connected to a or the frame supporting the barrel and adapted to receive weights to withstand the vertical reaction force on the barrel.

12. An apparatus as claimed in claim 11, wherein the platform carries a o bag or tank for receiving water to serve as the weight to oppose the vertical reaction force on the barrel.

13. A method of driving a pipe made of modular sections into the ground, the method comprising the sequential steps of

5 a) inserting a pipe section into a barrel having a piston for pushing the pipe section into the ground;

b) igniting a charge within barrel to cause movement of the piston and pipe section towards the ground; and

c) arresting the piston while in still contact with the pipe section to limit0 the penetration of the pipe section into the ground,

d) joining a further pipe section to the pipe section previously inserted into the ground,

e) repeating steps a) to c) to drive the joined pipe sections a controlled distance into the ground; and

5 f) repeating steps a) to e) to drive further pipe sections into the ground until a desired length of pipe has been achieved.

14. A method as claimed in claim 13, wherein the initial pipe section is connected to a tapered nose for displacing the earth as it is driven into the ground.

15. A method as claimed in claim 14, wherein the tapered nose section is of slightly larger diameter than the tube to reduce the friction