CN117413113A - Hydraulic down-the-hole hammer and submarine pile - Google Patents

Abstract

The invention relates to a hydraulic down-the-hole hammer. The hammer includes an elongate shaft and a piston having a central bore therethrough, the piston being slidably mounted for reciprocal movement on the shaft and arranged to strike a percussion drill bit. A front drive chamber and a rear drive chamber for the piston are disposed between the piston and the shaft, and the front chamber is separated from the rear chamber by an annular shoulder formed inside the piston bore. The hammer also includes a control valve that controls the reciprocation of the piston, wherein the control valve is disposed within the central bore of the piston. The hammer may be a disposable water hammer wherein the piston is the outermost part of the hammer. The invention also relates to a method and a system for installing a load bearing element in a seabed, a method and a system for installing a subsea anchor on a seabed, a subsea pile and a subsea anchor.

Description

Hydraulic down-the-hole hammer and submarine pile

Technical Field

The present invention relates to fluid operated hydraulic down-the-hole hammers, and more particularly to disposable or single use hydraulic down-the-hole hammers. The invention also relates to a subsea pile, and a method and a system for installing a load bearing element and a subsea anchor in a seabed.

Background

Hydraulic power down-the-hole hammers typically comprise three main components, namely a percussion piston, for transmitting impact energy to a drill bit or tool located at the front end of the down-the-hole hammer; a shuttle valve or control valve for controlling the flow of hydraulic fluid in the hammer, applying pressure to the surface of the percussion piston, thereby generating a cyclic force causing the piston to reciprocate; and one or more accumulators for receiving, storing and delivering back pressure hydraulic fluid to accommodate varying instantaneous flow demands resulting from reciprocation of the piston.

A conventional hydraulic down-the-hole hammer 100 is shown in fig. 1. In such conventional hammers, the piston 101 is generally solid and reciprocates within an outer cylinder to strike the bit 109 at the front end of the hammer. The piston drive chambers 102, 103 are arranged between the piston and the outer cylinder 104, and the control valve 105 and the accumulator 106 are positioned at the rear end 107 of the piston. Working fluid is supplied to the hammer via pressure line P and returned via return line T. A separate flushing fluid flow 108 is provided to flush cuttings from the hole. Due to the position of the control valve, the distance d between the control valve and the drive chamber _valve Relatively large. The accumulator 106 is generally upstream of the valve 105, so the distance d between the accumulator and the drive chamber _accu Even larger. The long flow path between the piston, valve and accumulator may create pressure waves that are detrimental to the hydraulic hammer components. Long flow channels also lead to pressure losses. The accumulator cannot operate effectively because the communication delay between the piston and the accumulator is large due to the distance between them.

In a typical hydraulic ram, the arrangement is similar to that outlined above, as shown in fig. 1. However, in the hydraulic hammer 200 shown in fig. 2, there is no return line T. Instead, a driving fluid is used to flush the stream 208. Furthermore, the piston 201 is completely submerged in water and only a small portion of the cross-sectional area of the piston is used to drive the piston. The remaining cross-sectional area is in an idle state because it is exposed to water at ambient pressure. This means that during operation of the hammer, the non-driving area of the piston needs to drain a large amount of water. This is accomplished by having a central bore 210 through the piston such that the front end 211 and the rear end 207 of the piston are in fluid communication with each other. The bore must be large enough to avoid significant pressure loss, which would negatively impact the performance of the hammer. The pressure loss can also be reduced by minimizing the size of the non-driving area of the piston. Increasing the size of the central bore and decreasing the size of the non-driving area of the piston results in a piston having a very small cross-sectional area, which is often too light for efficient drilling. This is solved by increasing the length of the piston in order to provide sufficient weight. However, this in turn results in a hammer that is impractical due to its length, which problem is exacerbated by the position of the valve at the rear of the piston. The existing water hammer is also complex in design, so that the production cost is high.

It is desirable to provide a hydraulic down-the-hole hammer that addresses some of the disadvantages associated with existing arrangements.

The seafloor piles may be used to anchor structures for mooring offshore structures (e.g. wind turbines) to the sea bed. The upper layer of the seabed is typically composed of soil or silt and may be fragile or unstable. Piles are load bearing elements that extend through the upper layers to lower, more stable layers of compacted soil and rock, transferring loads from the anchoring structures to the lower layers of the seabed.

Existing landpile installations involve drilling holes using a hammer that pulls casing down into the hole. Once the borehole reaches the target depth, the hammer is removed from the borehole leaving the casing in place. The steel bar is lowered from the center of the sleeve and then the hole is filled with water mortar. The sleeve may be removed before the mortar cures, in which case the mortar bonds the rebar together with the surrounding terrain material.

However, there are many difficulties with subsea pile installation, which means that this land installation method is unsuitable. One common method of securing a subsea anchor to the seabed is to use driven piles, wherein the piles are driven into the seabed by large underwater hydraulic hammers. Alternatively, a suction pile installation method may be used when the hollow pile is dropped onto the seabed, forming a seal between the pile bottom and the seabed. And then drawing water from the hollow center of the pile, creating suction, pulling the pile further into the sea floor.

The subsea piles as described above may be used to secure a subsea anchor to the sea floor. Such a subsea anchor may comprise a frame or template secured to the seabed using one or more piles. The wind turbine or other offshore structure may then be moored or otherwise secured to the sea floor anchor.

A method for installing such a subsea pile anchor is disclosed in US patent application publication No. US 2015/023779. The method includes placing a frame on a seabed, positioning a subsea rig on the frame, and driving a pile anchor into the seabed using the rig. Mortar is then pumped around the pile anchors, bonding the piles to the ground. This process may be repeated for several pile anchors to secure the frame to the seabed. The offshore structure can then be moored to the anchor using the mooring connection on the frame.

These mounting methods have a number of disadvantages. The installation speed of driven piles and suction piles is relatively slow. For driving piles, underwater hammers are bulky, complex and expensive, and require large support vessels. The suction method is only suitable for soft and sandy areas of the seabed, but cannot be used for areas with boulders or obstacles.

It is desirable to provide a method and system for installing piles or load bearing elements in the seabed, for example for anchoring a structure such as a wind turbine, which overcomes some of the disadvantages associated with existing methods.

Disclosure of Invention

According to one aspect of the present invention, there is provided a hydraulic down-the-hole hammer comprising:

an elongated shaft;

a piston having a central bore therethrough, the piston being slidably mounted for reciprocal movement on the shaft and arranged to strike a percussion drill bit, wherein a front drive chamber and a rear drive chamber for the piston are provided between the piston and the shaft, and wherein the front chamber is separated from the rear chamber by an annular shoulder formed inside the piston bore; and

a control valve for controlling the reciprocating movement of the piston, wherein the control valve is arranged within the central bore of the piston.

The term "front" is used herein to refer to the end of the hammer that faces the percussion drill bit, i.e., the drilling end of the hammer. The term "rear" is used herein to refer to the end of the hammer that is remote from the percussion drill bit, i.e., the uppermost end of the hammer during drilling.

This arrangement has several advantages. Since the valve is disposed within the piston, the distance of fluid between the valve and the drive chamber is minimized, thereby eliminating harmful pressure waves. The pressure loss is also very low. Because the drive chamber is inside the piston, rather than between the piston and the outer sleeve, the seal diameter is reduced compared to conventional hammers. This reduces leakage that is particularly important for hydraulic hammers due to the low viscosity of the working fluid. The production cost of the hammer is also lower due to the simple design.

Preferably, the control valve is disposed inside the shaft.

In a preferred embodiment, the piston has a single or unitary structure, that is, it is formed as a single piece. Since the annular shoulder of the piston that divides the front and rear chambers is disposed inside the piston bore, the piston can be manufactured and assembled into a single piece hammer.

Ideally, the piston is configured to strike an annular shoulder at the rear end of the percussion bit or drill bit. An annular shoulder may be provided on the skirt of the drill bit. The advantage of this arrangement is that the impact force is directly transferred to the bore of the drill bit at the point where the highest impact energy is required for the borehole.

In some embodiments, the hammer may include at least one accumulator disposed at the rear end of the piston. Because the valve is disposed within the piston, one or more of the accumulators may be positioned closer to the piston than in conventional arrangements, thereby reducingLess d _accu And thus efficiency is improved.

In one embodiment of the hammer, the working fluid is water. In this embodiment, the rear chamber may be connected to the pressure fluid channel and the control valve may be arranged to connect the front chamber to the rear chamber when the piston is moved in the rearward direction and to connect the front chamber to the flushing fluid channel through the shaft and the percussion bit when the piston is moved in the forward direction. Since the rear chamber is connected to the pressure fluid channel throughout the piston cycle, there is a constant pressure in the rear chamber and an alternating pressure in the front chamber.

In some embodiments, the hammer may further include an outer wear sleeve such that the piston is received within the wear sleeve. As with conventional hammers, the outer wear sleeve may protect the piston from wear during drilling. The percussion drill bit may be arranged at the front end of the wear sleeve. In one embodiment, the hammer is a closed loop hammer and the flushing fluid passage may be provided between the piston and the wear sleeve and through the percussion drill bit. This means that the entire outer surface of the piston can be exposed to the flushing flow, thereby providing very efficient cooling of the piston.

In another embodiment, the working fluid of the hammer is water and a flow ring is provided between the piston and the outer wear sleeve to provide fluid communication between the front and rear ends of the piston. A flushing fluid passage is provided through the shaft and the percussion drill bit. Because the drive chamber of the ram is disposed within the piston bore, flow communication between the front and rear ends of the piston may be provided by a flow ring external to the piston, rather than through the piston bore as in conventional water hammers. Such a flow ring has an inherently large flow area even though the radial clearance between the piston and the wear sleeve is small. This means that the cross-sectional area of the piston can be increased compared to a conventional water hammer, allowing for a sufficient piston weight with a short piston. The arrangement of the valve within the piston further reduces the length of the hydraulic hammer.

According to one aspect of the invention, the piston is the outermost component of the hammer. That is, the hammer does not include an outer wear sleeve for receiving the piston. By omitting the conventional outer wear sleeve from the hammer, the cost of the hammer is reduced, allowing it to be used as a single use, sacrificial or disposable hammer. Since the piston is the outermost part of the hydraulic hammer, it is subject to wear from the cuttings. However, since the hammer is disposable, the piston only needs to last for a time sufficient to drill a hole. For example, the hammer may remain in the hole when the hole has been drilled.

A flushing port may be provided in the shaft extending from the central bore of the shaft to an outer surface of the shaft at the front end of the piston. This allows a portion of the flushing water to drain between the piston and the impact surface of the drill bit, flushing the cuttings away from the impact surface to avoid damage thereto.

In various embodiments of hammers according to this invention, the shaft may include a coupling element at a forward end thereof, wherein the coupling element couples the percussion bit to the hammer and transmits rotational drive to the hammer.

Engagement means may be formed on the coupling element, which engagement means may engage with complementary engagement means formed inside the drill bit, whereby rotational drive from the shaft may be transmitted to the drill bit. In one embodiment, the coupling element is formed with a central bore and the flushing port is provided in the coupling element, extending from the central bore of the coupling element to the outer surface of the coupling element at the front end of the piston. The engagement means may comprise a plurality of axially extending splines formed on the exterior of the coupling element and the complementary engagement means may comprise a corresponding plurality of axially extending splines formed on the interior of the drill bit. In other embodiments, the engagement means may comprise a portion of the coupling element having a hexagonal or square cross-section, and the complementary engagement means may comprise an interior of the drill bit formed with a correspondingly shaped inner wall.

The hammer may further comprise a bit retaining means on the coupling element adapted to engage with a complementary retaining means on the bit to retain the bit in the hammer. The bit retention means may comprise a first thread formed on the front end of the coupling element externally of the coupling element and the complementary engagement means may comprise a second thread formed on the inside of the bit. The hammer bit may be assembled to the hammer by screwing the bit onto the coupling element such that the first thread is in front of the second thread. This arrangement retains the drill bit in the hammer and allows limited longitudinal movement of the drill bit.

In another embodiment, the bit retaining means comprises a bit retaining ring comprising a plurality of partial annular sector portions and the complementary engagement means comprises a shoulder formed inside the bit. In this embodiment, the coupling element may comprise a chuck.

According to one aspect of the invention there is provided a method for installing a load bearing element (e.g. a subsea pile) in a seabed, the method comprising:

drilling a hole of a desired depth in the seabed using a hydraulic down-the-hole hammer, wherein the down-the-hole hammer is operated by supplying a working fluid to the down-the-hole hammer;

Stopping the supply of working fluid to the hammer when the hammer is disposed or positioned in the bore;

supplying mortar to the hammer to at least partially fill the hammer and a hole in which the hammer is disposed or positioned with mortar; and

the mortar is allowed to cure so that the hammer and mortar form a load bearing element in the seabed.

Filling the hammer and/or hole may include partially filling the hammer and/or hole with mortar such that the hammer is bonded to the seabed material forming the hole. In certain embodiments, the hammer and/or the hole may be completely filled with mortar. The mortar may be provided to the hammer until the mortar is substantially flush with the seabed surface.

This approach has a number of advantages over existing methods of installing subsea piles. In particular, the methods disclosed herein allow for faster installation. In addition, piles can be installed in various seabed types using down-the-hole hammers, even in terrains where little sand or soil is present, where rock or boulders are present. However, since the hammer itself forms part of the carrier element, it need only be disposable and therefore can be manufactured less expensively than a typical hammer for driving piles into the sea floor.

The hammer may be a hammer according to any of the above embodiments. The hammer used to perform the method may be a disposable, single use or sacrificial hammer, wherein the working fluid is water, such as the hammers described above. In one embodiment, the disposable or sacrificial hammer does not include an outer wear sleeve. Instead, the piston is the outermost part of the hammer.

In one embodiment, a drilling rig is connected to the hammer and drilling rig are lowered to the seabed prior to drilling. The drill may be operated to provide rotational and feed forces to the hammer during drilling. After filling the borehole with mortar, the drill can be disconnected from the hammer and brought to the surface. In some embodiments, a drill rod may be disposed between the drilling machine and the hammer, and the drill rod is poured into the borehole with the mortar along with the hammer, such that the hammer, drill rod, and mortar together form a load bearing element or subsea pile.

According to another aspect of the invention there is provided a system for installing a load bearing element in a seabed, comprising:

a hydraulic down-the-hole hammer;

a working fluid supply, wherein the hammer is connectable to the working fluid supply to drill a hole of a desired depth in the seabed;

a mortar supply, wherein the hammer is connectable to the mortar supply when arranged or positioned in the hole to allow the hammer and the hole to be filled with mortar.

The system may include a drilling rig configured to provide rotational and feed forces to the hammer during drilling, wherein the drilling rig is connected to the hammer and descends with the hammer to the seabed prior to drilling.

The system may further comprise at least one drill rod or pipe connected between the drilling machine and the hammer. The drill rod may be sacrificial and may be grouted into the bore with the hammer such that the hammer, drill rod and mortar together form a load bearing element or a subsea pile.

The working fluid supply and the mortar supply may be provided at a sea level above the seabed, and the system may further comprise an umbilical, wherein the hammer is connectable to the working fluid supply and the mortar supply via the umbilical. In one embodiment, the working fluid pump is configured to provide a supply of working fluid to the hammer, and the mortar pump is configured to provide a supply of mortar to the hammer. The pump may be provided on the vessel or rig at or near the sea surface. The umbilical may include one or more cables or hoses arranged to connect the hammer and/or drill to surface equipment (e.g., working fluid pumps and mortar pumps). The umbilical may include a single channel that is selectively connectable to the working fluid supply and the mortar supply. Alternatively, the umbilical may include a first channel connectable to a working fluid supply to supply working fluid to the hammer and a second channel connectable to a mortar supply to supply mortar to the hammer.

The hammer may have a central bore through which mortar is supplied to the hammer and the bore. The drill rod may also have a central bore through which working fluid and mortar are supplied to the hammer, respectively. The working fluid of the hammer may be water. The piston of the hammer may be the outermost part of the hammer. The hammer may be a hammer according to any of the above embodiments. Preferably, the hammer is a disposable or sacrificial water hammer as described above.

In one embodiment, the percussion drill bit has a larger diameter than the piston, such that the diameter of the borehole is larger than the diameter of the piston, and an annular cavity is present between the piston and the wall of the borehole.

In one embodiment, the diameter of the percussion drill bit may be less than or equal to 300mm. The resulting load bearing elements may be referred to as micropiles, which may be preferred over larger piles because they are smaller, lighter, cheaper, easier to install, and produce less noise and vibration.

According to one aspect of the present invention there is provided a subsea pile comprising:

a hydraulic down-the-hole hammer disposed or positioned in a hole in the seabed; and

a curing mortar disposed within the hammer and between the hammer and the wall of the hole such that the hammer is bonded to the material of the seabed through the mortar.

The hammer may be a hammer according to any of the above embodiments. For example, the hammer of the subsea pile may be a disposable, single use or sacrificial hammer, wherein the working fluid is water. In one embodiment, the disposable or sacrificial hammer does not include an outer wear sleeve. Instead, the piston may be the outermost component of the hammer.

The subsea pile may further comprise at least one drill pipe or drill pipe connected to the hammer and disposed in a hole in the seabed, wherein the cured mortar is further disposed within the drill pipe or drill pipe and between the drill pipe or drill pipe and the hole wall, such that the drill pipe or drill pipe is also bonded to the material of the seabed by the mortar.

In one embodiment, the subsea stake may be a subsea mini stake having a diameter of less than or equal to 300 mm.

The subsea piles may comprise a mortar column into which a hydraulic down-the-hole hammer and optionally a drill pipe are embedded.

According to one aspect of the present invention there is provided a method for installing a subsea anchor on a seabed, comprising:

connecting a drilling rig and one or more hydraulic down-the-hole hammers to an anchor frame, wherein the drilling rig is configured to provide rotational and feed forces to each of the one or more hammers;

lowering the anchor frame to the seabed;

supplying working fluid to the or each hammer such that the or each hammer drills a hole of a desired depth in the seabed;

stopping supply of working fluid to the or each hammer when the or each hammer is located in its respective aperture and supplying mortar to the or each hammer to at least partially fill the hammer and the aperture in which the hammer is located with mortar;

Allowing the mortar to cure such that the or each hammer is bonded to the material of the seabed by the mortar; and

disconnecting the drilling machine from the anchor frame.

The or each hammer may be a hammer according to any of the embodiments described above. For example, the or each hammer used to perform the method may be a disposable, single use or sacrificial hammer in which the working fluid is water. In one embodiment, the or each disposable or sacrificial hammer does not include an outer wear sleeve. Instead, the piston may be the outermost component of the hammer.

This approach has a number of advantages over existing subsea anchor installation approaches. In particular, since piles anchoring the anchor to the seabed are formed using disposable or sacrificial down-the-hole hammers which are grouted into the hole, no separate hydraulic hammer is required for drilling. These disposable hammers can be made less expensive than typical hammers used to drive piles into the sea floor.

Preferably, the drilling machine provides separate rotational and feed forces to the or each hammer. This allows each hole in the seabed to be drilled simultaneously.

Mooring lines may be connected to the anchor frame to moor an offshore structure, such as a wind turbine, to the seabed.

According to one aspect of the present invention there is provided a system for installing a subsea anchor on a seabed, comprising:

an anchor frame;

a drilling rig and one or more hydraulic down-the-hole hammers connectable to the anchor frame, wherein the drilling rig is configured to provide rotational and feed forces to each of the one or more hammers;

a working fluid supply, wherein the or each hammer is connectable to the working fluid supply to drill a hole of a desired depth in the seabed;

a mortar supply, wherein the or each hammer is connectable to the mortar supply when in its respective bore to allow the hammer and the bore to be at least partially filled with mortar.

Preferably, the drilling machine comprises a separate feed and rotation system for each of the one or more hammers.

The working fluid supply and the mortar supply may be provided at a sea level above the seabed, and the system may further comprise:

an umbilical, wherein the or each hammer is connectable to a working fluid supply and a mortar supply through the umbilical.

The or each hammer may be a hammer according to any of the embodiments described above. The or each hammer working fluid may be water. The or each hammer may be a disposable or sacrificial hammer as described above. The or each hammer piston may be the outermost part of the hammer. The or each hammer's percussion drill bit may have a larger diameter than the piston, such that the diameter of the or each borehole is larger than the diameter of the respective piston, and an annular cavity exists between the or each piston and the wall of the respective borehole.

The anchor frame may comprise connection means for connecting to the one or more hammers. In one embodiment, the connection means may comprise one or more connectors, wherein a connector is provided for connection to the or each hammer. Each connector may include a mounting sleeve or boss.

The system may further comprise at least one drill rod or pipe connected between the drilling machine and the or each hammer. The drill pipe may also be sacrificial and may be grouted into the or each hole with a respective hammer such that each hammer, drill pipe and mortar together form a load bearing element or seafloor pile connected to the anchor frame to anchor it to the seabed.

According to one aspect of the present invention there is provided a subsea anchor comprising:

an anchor frame disposed on the seabed; and

one or more hydraulic down-the-hole hammers connected to the anchor frame, the or each hammer being located in a respective hole in the seabed; and

a curing mortar disposed within the or each hammer and between the hammer and the wall of the respective hole such that the or each hammer is bonded to the material of the seabed by the mortar.

The or each hammer may be a hammer according to any of the embodiments described above. For example, the or each hammer of the subsea anchor may be a disposable, single use or sacrificial hammer in which the working fluid is water. In one embodiment, the or each disposable or sacrificial hammer does not include an outer wear sleeve. Instead, the piston may be the outermost component of the hammer.

The subsea anchor may further comprise at least one drill rod or pipe connected to the or each hammer and arranged in a respective hole in the seabed, wherein the cured mortar is further arranged within the or each drill rod or pipe and between the or each drill rod and the wall of the corresponding hole, such that the drill rod or pipe is also bonded to the material of the seabed by the mortar.

Drawings

FIG. 1 is a schematic illustration of a conventional hydraulic down-the-hole hammer;

FIG. 2 is a schematic diagram of a conventional down-the-hole water hammer;

FIG. 3 is a schematic illustration of a hydraulic down-the-hole hammer according to an embodiment of the present invention;

FIG. 4 is a schematic illustration of a water hammer according to an embodiment of the present invention;

FIG. 5 is a schematic illustration of a disposable water hammer according to an embodiment of the present invention;

FIG. 6a is a perspective view of a coupling element and a bit of a hammer according to the present invention;

FIG. 6b is a cross-sectional view of the coupling element and bit of FIG. 6a, wherein the coupling element is assembled to the piston and shaft of the hammer;

FIG. 6c is a cross-sectional view of the assembly of FIG. 6b, wherein the drill bit is coupled with the coupling element;

FIG. 7a is a cross-sectional view of a disposable water hammer according to an embodiment of the present invention;

FIG. 7b is a detailed view of a portion of the hammer of FIG. 7 a;

figures 8a to 8d depict different phases of the hammer cycle of the hammer of figures 7a and 7 b;

FIG. 9 is a cross-sectional view of an assembly including a disposable water hammer coupled to a drilling rig and drill pipe, suitable for use in a system for installing subsea piles;

FIG. 10 is a cross-sectional view of a system for installing a subsea pile during subsea drilling, including the assembly of FIG. 9;

FIG. 11 is a cross-sectional view of the system of FIG. 10 after drilling a hole in the seafloor;

FIG. 12 is a cross-sectional view of a subsea pile, including the hammer and drill pipe of FIG. 9;

FIG. 13 is a perspective view of an assembly for use in a system for installing a subsea anchor on the seabed according to one aspect of the present invention;

FIG. 14 is a perspective view of the assembly of FIG. 13 after the hammer has been deployed;

FIG. 15 is a side view of the assembly of FIG. 14;

FIG. 16 is a perspective view of a seabed-mounted anchor;

FIG. 17 is a side view of the subsea anchor of FIG. 16;

FIG. 18a is a cross-sectional view of a disposable water hammer according to an embodiment of the present invention;

FIG. 18b is a detailed view of a portion of the hammer of FIG. 18 a;

fig. 19a to 19d depict different stages of the hammer cycle of the hammer of fig. 18a and 18 b;

FIG. 20a is a perspective view of a coupling element, chuck and bit of the hammer according to the present invention;

FIG. 20b is a cross-sectional view of the coupling member, chuck and drill of FIG. 20a, wherein the chuck is assembled to the coupling member of the hammer; and

Fig. 20c is a cross-sectional view of the assembly of fig. 20b, with the drill bit attached to the chuck.

Detailed Description

A hydraulic down-the-hole hammer 300 according to an embodiment of the present invention is shown in fig. 3. The hammer includes an elongated shaft 312, the elongated shaft 312 being formed with a central bore 314. The piston 301 also has a central bore 310 therethrough. The shaft is received within the piston bore such that the piston is slidably mounted for reciprocal movement on the shaft 312 and is arranged to strike an annular shoulder 315 at the rear end 316 of the percussion drill bit 309. The piston 301 is accommodated within an outer wear sleeve 317, with the percussion drill bit 309 being arranged at the front end 318 of the wear sleeve.

A front drive chamber 302 and a rear drive chamber 303 for the piston are provided between the piston 301 and the shaft 312. An annular shoulder 313 on the piston formed inside the piston bore 310 separates the front chamber 302 from the rear chamber 303. The inner diameter of the piston 301 at the rear of the shoulder 313 is greater than the inner diameter of the piston at the front of the shoulder so that the rear chamber has a larger drive area than the front chamber. The hammer also includes a control valve 305 disposed within the central bore 314 of the shaft to control the reciprocation of the piston. In other embodiments, the valve 305 may be disposed within the central bore 310 of the piston, between the piston and the shaft.

Hammer 300 is a closed loop hammer in which working fluid is supplied to the hammer via pressure line P and returned via return line T. A flushing fluid channel 308 is provided between the piston 301 and the wear sleeve 317 and through the percussion drill bit 309 such that flushing fluid exits the channel at bit face 319.

Hammer 300 also includes a pressure and return fluid reservoir 306 disposed at piston rear end 307. The accumulator is arranged at a distance d from the rear drive chamber 303 of the piston _accu Is a distance of (3).

A hydraulic down-the-hole hammer 400 according to another embodiment of the present invention is shown in fig. 4. As in the embodiment of fig. 3, the hammer includes an elongated shaft 412 formed with a central bore 414. The piston 401 also has a central bore 410 therethrough. The shaft is received within the piston bore such that the piston is slidably mounted for reciprocal movement on the shaft 412 and is arranged to strike an annular shoulder 415 at the rear end 416 of the percussion drill bit 409. The piston 401 is accommodated within an outer wear sleeve 417, at the front end 418 of which the percussion drill bit 409 is arranged.

A front drive chamber 402 and a rear drive chamber 403 for the piston are provided between the piston 401 and the shaft 412. An annular shoulder 413 on the piston formed inside the piston bore 410 separates the front chamber 402 from the rear chamber 403. The inner diameter of the piston 401 to the rear of the shoulder 413 is greater than the inner diameter of the piston in front of the shoulder so that the rear chamber has a larger drive area than the front chamber. The hammer also includes a control valve 405 disposed within the central bore 414 of the shaft to control the reciprocation of the piston.

The hydraulic hammer 400 shown in fig. 4 is an open-loop hydraulic hammer in which a working fluid (e.g., water) is supplied to the hydraulic hammer through a pressure line P. However, unlike the hydraulic hammer shown in fig. 3, the hydraulic hammer 400 does not have a return line. Instead, the driving fluid is used to flush the flow 408 through the shaft's central bore 414 and the percussion bit 409 to exit at the bit face 419. Unlike prior art hammers, the outer surface of the piston is not a sealing surface, thus providing a seal between the piston and the wear sleeve that allows fluid communication between the front and rear ends of the pistonInstead of providing the fluid communication through a piston bore as in the conventional water hammer shown in fig. 2. This allows the cross-sectional area of the piston to be increased compared to such conventional water hammers, thereby allowing sufficient piston weight to be achieved with a short piston. The arrangement of the valve 405 within the piston allows a distance d _accu The length of the hammer is reduced and further reduced.

Fig. 5 illustrates a low cost disposable or single use hydraulic down-the-hole hammer 500 according to an embodiment of the present invention. As in the embodiment of fig. 4, the hammer includes an elongated shaft 512 formed with a central bore 514. The piston 501 also has a central bore 510 therethrough. The shaft is received within the piston bore such that the piston is slidably mounted for reciprocal movement on the shaft 512 and is arranged to strike an annular shoulder 515 at a rear end 516 of the percussion drill bit 509. A front drive chamber 502 and a rear drive chamber 503 for the piston are provided between the piston 501 and the shaft 512. An annular shoulder 513 on the piston formed inside the piston bore 510 separates the front chamber 502 from the rear chamber 503. In this embodiment, the inner diameter of piston 501 behind shoulder 513 is smaller than the inner diameter of the piston in front of the shoulder, such that the front chamber has a larger drive area than the rear chamber. The hammer also includes a control valve 505 disposed within the central bore 514 of the shaft to control the reciprocation of the piston.

As with the hammer of fig. 4, the hammer 500 shown in fig. 5 is an open loop hammer in which a working fluid, such as water, is supplied to the hammer through a pressure line P. However, unlike the hammer of fig. 4, the hammer 500 does not include an outer sleeve, and thus the piston 501 is the outermost part of the hammer. This reduces the cost of the hammer so that it can be used as a disposable or sacrificial hammer for drilling only a single hole.

In this embodiment, the rear chamber 503 is connected to the pressure fluid passage P such that a constant pressure exists in the rear chamber. The control valve 505 is arranged to connect the front chamber 502 to the rear chamber 503 when the piston is moving in the backward direction and to connect the front chamber 502 to the flushing fluid channel 508 through the central bore of the shaft and the percussion drill bit when the piston is moving in the forward direction, whereby an alternating pressure exists in the front chamber 502.

Because the hammer 500 does not include an external wear sleeve or cylinder, the piston itself will be exposed to wear from the cuttings. However, since the hammer is disposable, the piston only needs to last for a time sufficient to drill one hole. In addition, a radial flush port 521 extends from the central bore 514 of the shaft to the outer surface of the shaft, allowing a portion of the displaced fluid to be displaced between the forward end 522 of the piston 501 and the striking face 515 of the drill bit. This keeps the cuttings away from the impact surface of the drill bit and piston and prevents premature failure of the impact surface.

Fig. 6a, 6b and 6c show a coupling device for connecting a percussion drill bit to a hammer according to the present invention. The hammer 600 shown in fig. 6a, 6b and 6c is similar in several respects to the disposable hammer 500 shown in fig. 5, but the coupling device shown is also applicable to the hammers 300, 400 shown in fig. 3 and 4 and to other hammers of the invention.

Shaft 612 of hammer 600 includes a coupling element 622 at a front end 623 thereof. As shown in fig. 6b and 6c, the coupling element has an outer diameter that is larger than the outer diameter of the body 638 of the shaft, so that the front chamber is sealed by the coupling element and the piston. A portion 624 of the coupling element is formed to have a square cross section and a corresponding interior 625 of the drill bit 609 is formed to have a square inner wall such that when the drill bit is assembled to the coupling element of the shaft, the portion 624 of the coupling element is received within the portion 625 of the drill bit to allow rotational drive to be transferred from the shaft to the drill bit. In other embodiments, the portion 624 of the coupling element may be formed to have a hexagonal or octagonal cross-section, and the inner portion of the drill bit may be shaped accordingly. In a further embodiment, axially extending splines may be provided on the exterior of the coupling element, engageable with corresponding splines provided on the interior of the drill bit, for transmitting rotational drive.

The coupling element 622 also includes a bit retention device engageable with a complementary bit retention device on the bit 609 for longitudinally coupling the bit to the hammer. In the embodiment shown in fig. 6a, 6b and 6c, the bit holder comprises a first thread 626 formed on the exterior of the coupling element at the front end 627 of the coupling element 622. The complementary engagement means includes a second thread 628 formed on the interior of the drill bit.

The drill bit is coupled to the hammer by threading the second thread 628 through the first thread 626 such that the first thread is forward of the second thread. This couples the drill bit to the coupling element in the longitudinal direction and retains the drill bit in the hammer while allowing limited longitudinal movement of the drill bit. Next, the drill bit is rotated to align the portion 625 of the drill bit with the square portion 624 of the coupling element such that the portion 624 of the coupling element is received within the portion 625 of the drill bit to engage the rotational coupling. The coupling member 622 is coupled to the body 638 of the shaft by a threaded connection.

Fig. 7a and 7b illustrate a control valve 705 suitable for use with hammer 700 in accordance with the present invention. The valve is particularly suitable for use with the disposable hammer of the present invention, such as the disposable hammer shown in fig. 5. Valve 705 includes a top or rear inlet 728 and a top or rear outlet 729. The valve also includes a bottom or front inlet 730 and a bottom or front outlet 731. Also shown in fig. 7a are a valve chamber 732, a pilot chamber 733, a pilot port 734, a front control edge 735, a rear control edge 736, and a control valve cover 737.

Hammer cycling examples of disposable hammers including the valve of fig. 7a and 7b are shown in fig. 8 a-8 d. In fig. 8a, the piston 801 is moving in an upward or rearward direction (to the left as shown). The rear chamber 803 is connected to the pressure fluid throughout the hammer cycle. The front chamber 802 is connected to high pressure fluid through the valve chamber 832 and the rear chamber 803, as indicated by the arrows. As the inner diameter of the piston 801 increases, the front chamber has a larger pressure area than the rear chamber, so that the piston moves in the rearward direction. The valve pilot chamber 833 is pressurized by the front control edge 835, which has connected the pilot chamber to the rear chamber 803. The pressure area of the pilot chamber is larger than the valve chamber. The flow connection between the front chamber 802 and the shaft bore 814 is closed, while the flow connection between the front chamber and the valve chamber 832 is open. The valve chamber is continuously connected to the rear chamber 803 via a rear outlet 829.

In fig. 8b, the piston 801 has reached a point where the flow connection from the pilot chamber 833 to the ambient pressure has been opened by the rear control edge 836. The pressure in the pilot chamber will drop and there will be a net hydraulic pressure that causes the valve 805 to switch.

In fig. 8c, valve 805 has been switched. The valve closes the front inlet 830 and opens the front outlet 831 so that the exiting water flows into the shaft bore 814, as indicated by the arrow. The hydraulic force reverses the direction of the piston 801 and drives it toward the drill bit 809. As indicated by the arrows, a substantial portion of the displaced water will flow through the shaft bore and drill bit, exiting at bit face 819 to flush cuttings from the bit face. As indicated by the arrows, a small portion of the discharged water will flow out through radial holes or ports 821 located near the bit impact surface 815 to flush cuttings from the impact surfaces of the bit and piston.

In fig. 8d, the piston 801 is moved towards the drill bit 809 (to the right as shown). Just prior to impact, the piston 801 connects the pilot chamber 833 to the rear chamber 803 via the front control edge 835. This causes the valve to switch just after the piston impacts the drill bit. The cycle starts again as shown in fig. 8 a.

A hydraulic down-the-hole hammer 1800 according to another embodiment of the present invention is shown in fig. 18a and 18 b. The hammer shown is a low cost disposable or single use hammer. However, aspects of the present embodiment can also be applied to a multi-use hammer. As in the embodiments described above, the hammer includes an elongate shaft 1812 formed with a central bore 1814. The piston 1801 also has a central bore 1810 therethrough. The shaft is received within the piston bore such that the piston is slidably mounted for reciprocal movement on the shaft 1812 and is arranged to strike an annular shoulder 1815 at the rear end 1816 of the impact bit 1809. A front drive chamber 1802 and a rear drive chamber 1803 for the piston are disposed between the piston 1801 and the shaft 1812. An annular shoulder 1813 on the piston formed inside the piston bore 1810 separates the front chamber 1802 from the rear chamber 1803. In this embodiment, the inner diameter of the piston 1801 to the rear of the shoulder 1813 is smaller than the inner diameter of the piston forward of the shoulder, such that the front chamber has a larger drive area than the rear chamber. The hammer also includes a control valve 1805 disposed within the central bore 1814 of the shaft to control reciprocation of the piston.

The control valve 1805 is shown in more detail in fig. 18 b. The valve 1805 includes a top or rear inlet port 1828 and a top or rear outlet port 1829. The valve also includes a bottom or front inlet 1830 and a bottom or front outlet 1831. Also shown in fig. 18b are valve undercut 1832, pilot chamber 1833, pilot port 1834, valve shoulder 1839, and valve high pressure chamber 1840.

Hammer cycling examples of disposable hammers including the valve of fig. 18a and 18b are shown in fig. 19 a-19 d. In fig. 19a, the piston 1901 is moving in an upward or rearward direction (to the left as shown). The rear chamber 1903 is connected to the pressure fluid throughout the hammer cycle. The forward chamber 1902 is connected to high pressure fluid through a rear outlet 1929, a pilot chamber 1933, a valve undercut 1932, and a forward inlet 1930, as indicated by arrows. As the inner diameter of the piston 1901 increases, the front chamber has a larger pressure area than the rear chamber, so that the piston moves in the rearward direction. Valve pilot chamber 1933 is pressurized through pilot port 1934 and/or rear outlet port 1929. The pilot chamber 1933 has a larger pressure area than the valve high pressure chamber 1940, which is continuously connected with high pressure fluid. The flow connection between the forward chamber 1902 and the shaft bore 1914 is closed.

In fig. 19b, the piston 1901 has reached a point where the piston disconnects the rear outlet 1929 from the rear chamber 1903. The front chamber 1902 does not receive pressurized fluid from the rear chamber and the piston will continue to move upward due to its inertia. The pressure in the front and pilot chambers 1933 will collapse and there will be a net hydraulic pressure that causes the valve 1905 to switch.

In fig. 19c, valve 1905 has been switched. The valve closes the flow connection between the rear chamber 1903 and the front chamber 1902 and opens the front outlet 1931 such that the exiting water flows into the shaft bore 1914, as indicated by the arrows. The hydraulic force reverses the direction of the piston 1901 and drives it toward the drill bit 1909. As indicated by the arrows, the discharged water will flow through the shaft bore and drill bit, discharging at bit face 1919 to flush cuttings from the bit face. Although not shown, the radial flushing port may also extend from the central bore of the shaft to the outer surface of the shaft, allowing a portion of the displaced fluid to be displaced between the forward end of the piston and the striking face of the drill bit, as described above.

In fig. 19d, the piston 1901 is moved toward the drill bit 1909 (to the right as shown). Just prior to impact, the piston 1901 will connect the pilot chamber 1933 to the rear chamber 1903 through the pilot port 1934. This causes the valve to switch just after the piston impacts the drill bit. The cycle starts again as shown in fig. 19 a.

Fig. 20a, 20b and 20c show a connection device for connecting a percussion drill bit to a hammer according to the invention. The hammer 2000 shown in fig. 20a, 20b and 20c is similar in several respects to the disposable hammer 1800 shown in fig. 18a and 18b, but the illustrated attachment means can also be applied to other hammers of the present invention.

Shaft 2012 of hammer 2000 includes a coupling assembly 2050 at a front end 2023 thereof. The coupling assembly includes a sealing flange 2022 and a coupling element in the form of a chuck 2041. As shown in fig. 20b and 20c, the outer diameter of the sealing flange is larger than the outer diameter of the main body 2038 of the shaft, so the front chamber is sealed by the sealing flange and the piston 2001. The sealing flange 2022 is formed with a connection means including internal threads 2043 at its forward end. A complementary coupling means comprising external threads 2044 is provided on the rear of the chuck. Engagement means in the form of axially extending splines 2045 provided on the exterior of the chuck are engageable with complementary engagement means in the form of corresponding splines 2046 provided on the interior of the drill bit 2009, whereby rotational drive from the shaft is transferred to the drill bit. In other embodiments, the chuck may be formed to have a square, hexagonal, or octagonal cross-section, and the inner portion of the drill bit may be shaped accordingly, as described above.

The hammer 2000 also includes a bit retention device on the chuck that is engageable with a complementary retention device on the bit 2009 for longitudinally coupling the bit to the hammer. In the embodiment shown in fig. 20a, 20b and 20c, the bit retention means comprises a bit retention ring 2042 comprising a plurality of partial annular sector portions, and the complementary bit retention means comprises a shoulder 2049 formed inside the bit at its rear end

The drill bit is coupled to the hammer by threading threads 2044 on the chuck into threads 2043 on the sealing flange 2022. The sealing flange is also threadably connected to the body 2038 of the shaft 2012. Sufficient space is left between the forward end 2047 of the sealing flange and the annular shoulder 2048 on the chuck to allow the sector of the bit retaining ring 2042 to be inserted therebetween. The drill bit is then pushed onto the chuck such that the splines 2045 on the chuck engage with the complementary splines 2046 on the drill bit. The threaded connection between the chuck and the sealing flange is then tightened by rotating the drill 2009. When the connection is tightened, the annular shoulder 2048 on the chuck is pushed toward the forward end 2047 of the sealing flange, forcing the sector of the bit retaining ring 2042 outwardly, as shown in fig. 20 c. The bit is retained in the hammer by engagement between the shoulder 2049 and the bit retaining ring 2042.

Fig. 9 shows an assembly 950 for use in a system for installing a load bearing element (e.g. a subsea pile) in the seabed. The assembly includes a disposable or sacrificial hydraulic down-the-hole hammer 900. Hammer 900 is a water hammer similar to hammer 700 shown in fig. 7a and 7b and includes a piston 901 for percussive drill bits 909. The piston 901 is the outermost part of the hammer, and the diameter D of the percussion drill bit 909 is larger than the diameter of the piston. The assembly also includes a drill rod 951 connected between the drill 958 and the hammer, the drill rod having a central bore 955 therethrough.

The drill 958 is configured to provide rotational and feed forces to the hammer during drilling. The rig is connected to the drill pipe 951 and the hammer 900 and descends with the hammer to the seabed 954 prior to drilling.

As shown in fig. 10, the system further includes an umbilical 952, wherein the hammer may be connected to a pressurized water supply and a mortar supply through the umbilical via a drill pipe. A supply of water and a supply of mortar are provided at sea level 953. The water pump and mortar pump on the ship 959 provide a supply of water and a supply of mortar, respectively.

In use, the rig is coupled to the hammer via the drill pipe 951 and the assembly is lowered to the seabed 954. The hammer 900 operates by supplying water thereto through an umbilical 952 to drill a hole 956 in the seafloor, as shown in fig. 10 and 11. The rotation and feed forces are provided by the drilling machine. The operation of the hammer is as described above with reference to fig. 8. When the borehole reaches the desired depth, as shown in fig. 11, the rotation and feed forces are stopped and the water supply to the hammer is stopped, for example, by disconnecting the umbilical from the water pump. As shown in fig. 11, the diameter of bore 956 is greater than the diameter of piston 901, so there is an annular cavity 957 between the piston and the bore wall.

Mortar 960 is then supplied to the hammer via the umbilical, for example by connecting the umbilical to a mortar pump. Mortar flows through the central bore 955 of the drill rod and through the hammer 900 and into the bore 956 through the drill bit 909. Mortar is pumped into the hole until the hole is at least partially filled, as shown in fig. 12. The drilling machine is disconnected with the hammer and returns to the ground. When the mortar is cured, the hammer and drill pipe are combined with the seabed material, causing the hammer, drill pipe and mortar to form a subsea pile, as shown in fig. 12.

An assembly 1300 for use in a system for installing a subsea anchor on a seabed is shown in figures 13-15. The assembly includes an anchor frame or form 1301. In the illustrated embodiment, the anchor frame is generally triangular in shape with a plurality of ribs 1308 to enhance its structural integrity. In other embodiments, the anchors may be rectangular, or any other suitable shape. Mooring attachments 1310 are also provided on the anchor frame to allow mooring lines to be attached thereto for mooring an offshore structure, such as a wind turbine.

The assembly further includes a drilling rig 1302 and three sacrificial hydraulic down-the-hole hammers 1303 and corresponding drill rods or pipes 1304, each connected to the anchor frame 1301 by a connector 1307 in the form of a mounting sleeve or boss provided on an outer edge of the frame 1301. Each hammer 1303 is a water hammer similar to hammer 700 shown in fig. 7a and 7 b. The drilling machine 1302 includes three identical feed and rotation systems 1305 such that the drilling machine is configured to provide rotation and feed forces to each of the hammers 1303. In other embodiments, the system may include more or fewer hammers, and the drilling machine may include a corresponding number of feed forces and rotation systems. As shown in fig. 13, the rig 1302 is configured such that each of the hammer and drill pipe pairs is disposed at an acute angle to the seabed 1306.

As shown in fig. 15, each hammer 1303 and corresponding drill stem 1304 may be connected to a working fluid supply for drilling a hole 1311 of a desired depth in the seabed 1306. In the illustrated embodiment, the borehole is angled from vertical to minimize bending or shear forces on the anchor. However, in other embodiments, the holes may be drilled vertically down into the seabed or at an angle between 20 and 90 degrees to the seabed. As shown in fig. 10, the working fluid may be supplied from a rig or vessel on the sea surface. Because the drill 1302 includes three separate feed and rotation systems 1305, the hole 1311 may be drilled simultaneously. Alternatively, the holes may be drilled sequentially. When the hammers 1303 are operated, each hammer 1303 and drill rod 1304 passes through a respective connector 1307. As shown in fig. 14 and 15, after drilling, the upper portion of each drill rod 1304 is retained within a corresponding connector 1307 to connect the anchor to the drill rod. After drilling, each hammer is connected to a mortar supply in its respective hole to allow the hammer and hole to be at least partially filled with mortar. Mortar may be supplied through the umbilical as shown in fig. 10.

Once the hole 1311 is filled with mortar, the drill 1302 is disconnected from the hammer 1303 and returned to the surface, leaving the seafloor anchor on the seafloor, as shown in fig. 16 and 17. Once the mortar has cured, the subsea anchor comprising anchor frame 1301 is secured to the seabed by means of hammers 1303 and corresponding drill pipes 1304 connected to the anchor frame via connectors 1307. Nuts or other fasteners may be attached to the upper end 1309 of each drill rod to secure the anchor frame to the subsea pile formed by the hammer and drill rod pairs. Each of the pairs of hammers and drill pipes are grouted into place in a respective hole in the seabed such that each hammer and drill pipe is bonded to the material of the seabed 1306, thereby securing the anchor in place.

As used herein with reference to the present invention, the words "comprise/include" and the word "having/with" are used to specify the presence of stated features, integers, steps or components, but do not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.

Claims (41)

1. A hydraulic down-the-hole hammer comprising:

an elongated shaft;

a piston having a central bore therethrough, the piston being slidably mounted for reciprocal movement on the shaft and arranged to strike a percussion drill bit, wherein a front drive chamber and a rear drive chamber for the piston are provided between the piston and the shaft, and wherein the front chamber is separated from the rear chamber by an annular shoulder formed inside the piston bore; and

a control valve for controlling the reciprocating movement of the piston, wherein the control valve is arranged within the central bore of the piston.

2. The hydraulic down-the-hole hammer of claim 1, wherein the shaft comprises a central bore and the control valve is disposed inside the shaft.

3. A hydraulic down-the-hole hammer as set forth in claim 1 or claim 2, wherein the piston has a unitary structure.

4. A hydraulic down-the-hole hammer as claimed in any one of the preceding claims, wherein the piston is arranged to strike an annular shoulder at the rear end of the percussion bit.

5. A hydraulic down-the-hole hammer as set forth in any one of the preceding claims, further comprising at least one accumulator disposed at the rear end of the piston.

6. A hydraulic down-the-hole hammer as set forth in any one of the preceding claims, wherein:

the working fluid of the hammer is water;

the rear chamber is connected to a pressure fluid passage; and is also provided with

The control valve is arranged to connect the front chamber to the rear chamber when the piston is moved in a rearward direction and to connect the front chamber to the flushing fluid channel through the central bore of the shaft and the percussion drill bit when the piston is moved in a forward direction.

7. A hydraulic down-the-hole hammer as set forth in any one of the preceding claims, further comprising an outer wear sleeve, wherein the piston is housed within the outer wear sleeve and the impact bit is disposed at a forward end of the outer wear sleeve.

8. The hydraulic down-the-hole hammer of claim 7, wherein the hammer is a closed loop hammer and a flushing fluid passage is provided between the piston and the outer wear sleeve and through the percussion drill bit.

9. The hydraulic down-the-hole hammer of claim 7, wherein the working fluid of the down-the-hole hammer is water, and wherein a flow ring is provided between the piston and the outer wear sleeve, and a flushing fluid passage is provided through the shaft and the percussion drill bit.

10. A hydraulic down-the-hole hammer as set forth in any one of claims 1-6, wherein the piston is an outermost component of the hammer.

11. The hydraulic down-the-hole hammer of claim 10, further comprising:

a flushing port in the shaft extending from the central bore of the shaft to an outer surface of the shaft at a forward end of the piston.

12. A hydraulic down-the-hole hammer according to any one of the preceding claims, wherein the shaft comprises a coupling element at its front end, wherein the coupling element couples the percussion drill bit to the hammer and transmits rotational drive thereto.

13. A hydraulic down-the-hole hammer as set forth in claim 12, further comprising engagement means formed on the coupling element, the engagement means engageable with complementary engagement means formed inside the drill bit, whereby rotational drive from the shaft is transferred to the drill bit.

14. A hydraulic down-the-hole hammer as set forth in claim 12 or 13, further comprising a bit retaining device on the coupling element adapted to engage with a complementary retaining device on the bit to secure the bit in the hammer.

15. A hydraulic down-the-hole hammer as set forth in claim 14, wherein the bit retaining means comprises a first thread formed on the exterior of the coupling element at the forward end thereof, and the complementary engagement means comprises a second thread formed on the interior of the bit.

16. A method for installing a load bearing element in a seabed, comprising:

drilling a hole of a desired depth in the seabed using a hydraulic down-the-hole hammer, wherein the hammer is operated by supplying working fluid to the hammer;

stopping the supply of working fluid to the hammer when the hammer is located in the bore;

supplying mortar to the hammer to at least partially fill the hammer and the hole in which the hammer is located with mortar; and

the mortar is allowed to cure so that the hammer and mortar form a load bearing element in the seabed.

17. The method of claim 16, further comprising:

connecting a drilling rig to the hammer and lowering the hammer and drilling rig to the seabed prior to drilling; and

The drill is operated to provide rotational and feed forces to the hammer during drilling.

18. The method of claim 17, further comprising:

after the borehole is at least partially filled with mortar, the drill is disconnected from the hammer.

19. A system for installing a load bearing element in a seabed, comprising:

a hydraulic down-the-hole hammer;

a working fluid supply, wherein the hammer is connectable to the working fluid supply to drill a hole of a desired depth in the seabed;

a mortar supply, wherein the hammer is connectable to the mortar supply when located in the hole to allow the hammer and the hole to be at least partially filled with mortar.

20. The system of claim 19, wherein the working fluid supply and the mortar supply are provided at a sea level above a sea floor, the system further comprising:

an umbilical, wherein the hammer is connectable to a working fluid supply and a mortar supply through the umbilical.

21. The system of claim 19 or claim 20, wherein the working fluid is water.

22. The system of any one of claims 19 to 21, comprising:

a working fluid pump configured to provide a supply of working fluid to the hammer; and

A mortar pump configured to provide a supply of mortar to the hammer.

23. The system of any of claims 19 to 22, further comprising:

a drilling rig configured to provide rotational and feed forces to the hammer during drilling, wherein the drilling rig is connected to the hammer and descends with the hammer to the seabed prior to drilling.

24. The system of any one of claims 19 to 23, wherein the hammer is a hammer according to any one of claims 1 to 15.

25. The system of claim 24, wherein the hammer is a hammer according to any one of claims 10 to 15, and wherein the percussion drill bit has a larger diameter than the piston, such that the diameter of the borehole is larger than the diameter of the piston, and an annular cavity is present between the piston and the wall of the borehole.

26. A seafloor pile comprising:

a hydraulic down-the-hole hammer located in a hole in the seafloor; and

a curing mortar disposed within the hammer and between the hammer and the wall of the hole such that the hammer is bonded to the material of the seabed through the mortar.

27. A method for installing a subsea anchor on a seabed, comprising:

Connecting a drilling rig and one or more hydraulic down-the-hole hammers to an anchor frame, wherein the drilling rig is configured to provide rotational and feed forces to each of the one or more hammers;

lowering the anchor frame to the seabed;

supplying working fluid to the or each hammer such that the or each hammer drills a hole of a desired depth in the seabed;

stopping supply of working fluid to the or each hammer when the or each hammer is located in its respective bore and supplying mortar to the or each hammer to at least partially fill the hammer and the bore in which the hammer is located with mortar;

allowing the mortar to cure such that the or each hammer is bonded to the material of the seabed by the mortar; and

disconnecting the drilling machine from the anchor frame.

28. A method according to claim 27, wherein the drilling machine provides separate rotation and feed forces to the or each hammer.

29. A method according to claim 27 or 28, comprising a plurality of hammers, and wherein each hammer drills its respective hole in the seabed simultaneously.

30. The method of any one of claims 27 to 29, further comprising coupling a mooring line to the anchor frame.

31. A system for installing a subsea anchor on a seabed, comprising:

An anchor frame;

a drilling rig and one or more hydraulic down-the-hole hammers connectable to the anchor frame, wherein the drilling rig is configured to provide rotational and feed forces to each of the one or more hammers;

a working fluid supply, wherein the or each hammer is connectable to the working fluid supply to drill a hole of a desired depth in the seabed;

a mortar supply, wherein the or each hammer is connectable to the mortar supply when in its respective bore to allow the hammer and the bore to be at least partially filled with mortar.

32. The system of claim 31, wherein the drilling rig includes a separate feed and rotation system for each of the one or more hammers.

33. The system of claim 31 or 32, wherein the working fluid supply and the mortar supply are provided at a sea level above the sea floor, the system further comprising:

an umbilical, wherein the or each hammer is connectable to a working fluid supply and a mortar supply through the umbilical.

34. A system according to any one of claims 30 to 32, wherein the or each hammer is a hammer according to any one of claims 1 to 15.

35. A system according to claim 34, wherein the or each hammer is a hammer according to any one of claims 10 to 15, and wherein the or each hammer's percussion bit has a larger diameter than the piston, such that the diameter of the or each borehole is larger than the diameter of the respective piston, and an annular cavity is present between the or each piston and the wall of the respective borehole.

36. A subsea anchor comprising:

an anchor frame disposed on the seabed; and

one or more hydraulic down-the-hole hammers connected to the anchor frame, the or each hammer being located in a respective hole in the seabed; and

a curing mortar disposed within the or each hammer and between the hammer and the wall of the respective hole such that the or each hammer is bonded to the material of the seabed by the mortar.

37. A hydraulic down-the-hole hammer substantially as hereinbefore described with reference to any one of figures 1 to 8 and/or as shown in any one of figures 1 to 8.

38. A system for installing a load bearing element in the seabed substantially as hereinbefore described with reference to any one of figures 9 to 12 and/or as shown in any one of figures 9 to 12.

39. A seafloor pile substantially as hereinbefore described with reference to figure 12 and/or as shown in figure 12.

40. A system for installing a subsea anchor on the seabed, the system being substantially as hereinbefore described with reference to any of figures 13 to 17 and/or as shown in any of figures 13 to 17.

41. A subsea anchor substantially as hereinbefore described with reference to figures 16 or 17 and/or as shown in figures 16 or 17.