NO345425B1

NO345425B1 - A barrel unit, a charging unit, a device, a system and a method for forcing a fastening element into a structure submerged in water

Info

Publication number: NO345425B1
Application number: NO20190225A
Authority: NO
Inventors: Lars Gunnar Hodnefjell; Eirik Kloster Jakobsen
Original assignee: Blue Logic As
Priority date: 2019-02-19
Filing date: 2019-02-19
Publication date: 2021-01-25
Also published as: NO20190225A1

Description

A BARREL UNIT, A CHARGING UNIT, A DEVICE, A SYSTEM AND A METHOD FOR FOR-CING A FASTENING ELEMENT INTO A STRUCTURE SUBMERGED IN WATER

Introduction

The present invention relates to a barrel unit for forcing a fastening element into a structure submerged in water and a charging unit for charging an inlet of the barrel unit with pressurized gas.

The present invention further relates to a device comprising the barrel unit and the charging unit, and a system comprising the device. The invention is furthermore directed to a method for forcing a fastening element into a structure submerged in water and use of the above-mentioned entities.

Prior art

Devices for forcing fastening elements into a structure, such as nail guns, are commonly used in construction work. The fastening devices are typically driven by compressed air, electromagnetism, flammable gases or small explosive charges.

Correspondingly, fastening devices are used for forcing fastening elements into a structure submerged in water. Example of such use is when fastening rivets into a steel plate, or similar. Generally, these devices configured for submerged use are based on use of small explosive charges in order to obtain enough energy to force the fastening elements into the structure. Patent US 4505018 discloses a cartridge loaded stud gun for explosively attaching a sacrificial anode to a subsea structure.

In connection to offshore hydrocarbon production facilities the logistic of explosive charges is strictly regulated. Avoidance of explosive charges simplifies offshore operations.

The invention has for its object to remedy or to reduce at least one of the drawbacks of the prior art, or at least provide a useful alternative to prior art. This object is achieved through features, which are specified in the description below and in the claims that follow. In particular, an object of the invention is to provide a device for forcing a fastening element into a structure submerged in water without the use of explosive charges.

This object is obtained by means of a device for forcing a fastening element into a structure submerged in water. The device comprises a barrel unit and a charging unit. Th barrel unit comprises a barrel body, and a barrel bore within the barrel body is adapted to house the fastening element and to seal the fastening element from the ambient surrounding, a passage to the barrel bore, and connection means for releasably connecting the barrel unit to the charging unit configured to charge an internal pressure compartment of the barrel bore with pressurized gas. The barrel unit further comprises a rupture device configured to fail or burst at a predetermined pressure difference between the pressure compartment of the barrel bore and a barrel compartment of the barrel bore. The gas pressure in the pressure compartment forces the fastening element out of the barrel bore and into the structure.

By means of a gas passage between the charging unit and the barrel unit the charging unit gradually builds up a gas pressure in the pressure compartment until the predetermined pressure difference between the pressure compartment and the barrel compartment is reached. At the predetermined pressure, the rupture device burst, and the pressurized gas forces the fastening element out of the barrel compartment and into the structure.

The barrel unit provides the advantage of enabling a fastening element to be forced into a structure submerged in water with enough energy without the use of explosive charges. After the fastening element has been forced into the structure, the barrel unit is consumed and may be replaced with a new barrel unit pre-loaded with a fastening element for continued operation.

According to an embodiment of the invention, the energy in which the fastening element is forced into a structure is adjusted for different use by arranging barrel units with different rupture devices configured to fail or burst at different predetermined pressure difference between the pressure compartment and the barrel compartment, thereby resulting in different energy in which the fastening element is forced out of the chamber and into the structure.

For example, a first type barrel units have a first rupture device configured for first type structures, such as metal plates of a first material thickness or a first material. Correspondingly, a second type barrel units have second rupture device configured for second type structures, such as metal plates of a second material thickness or a second material. The first and the second type barrel units have different rupture devices configured to fail at different pressure difference between the pressure compartment and the barrel compartment. The first type barrel units comprise rupture devices configured to fail at a first pressure difference between the pressure compartment and the barrel compartment, and the second type barrel units comprise rupture devices configured to fail at a second pressure difference between the pressure compartment and the barrel compartment.

According to an embodiment of the invention, the rupture device comprises one of a rupture bolt and a rupture disc. The rupture bolt is provided with an incipient weakening configured to break when the rupture bolt is subjected to said predetermined pressure difference. The incipient weakening is designed so that the rupture bolt is failing at the predetermined pressure difference between the pressure compartment and the barrel compartment. In the same way the rupture disc is designed to burst at the predetermined pressure difference between the pressure compartment and the barrel compartment.

According to an embodiment of the invention, the predetermined pressure difference between the pressure compartment and the barrel compartment is in the range 1200–1500 bar (120-150 MPa).

According to an embodiment of the invention, the barrel unit comprises a mouth portion for discharge of the fastening element from the barrel bore, and a sealing member at the mouth portion is configured to burst when the fastening element is forced out of the barrel unit and into the structure. The sealing member assures that water is not introduced into the barrel bore through the mouth portion prior to that the fastening element is forced out of the barrel bore.

According to an embodiment of the invention, the barrel unit comprises a further sealing member at an entrance to the pressure compartment, which further sealing member is configured to burst when the charging unit charges the pressure compartment with pressurized gas or when the barrel unit is connected to the charging unit. The further sealing member assures that water is not introduced into the pressure chamber. The sealing member is configured to burst by the gas that is introduced into the pressure chamber or when connecting the barrel unit to the charging unit. According to an embodiment of the invention, the connection between the barrel unit and the charging unit comprises means for piercing the further sealing member.

According to an embodiment of the invention, the barrel unit comprises an elongated barrel bore. The elongated length of the barrel bore enables the fastening element to be accelerated within the barrel bore prior to being forced out of the opening and into the structure.

According to an embodiment of the invention, the fastening element has a size constituting a portion of a length of the barrel bore.

According to an embodiment of the invention, the barrel bore has a length that constitutes more than two times the length of the fastening element, preferably more than five times the length of the fastening element, more preferably more than ten times the length of the fastening element.

According to an embodiment of the invention, the barrel unit further comprises a holder for releasably holding the fastening element oriented within the barrel bore. The holder has the function of maintaining the orientation and the position of the fastening element within the barrel bore during transportation and handling of the barrel unit.

In a first aspect the invention concerns a barrel unit for forcing a fastening element into a structure submerged in water. The barrel unit comprises a barrel body and a barrel bore within the barrel body adapted to house the fastening element, the barrel bore being sealed from the ambient surrounding, a connection means for releasably connecting the barrel unit to a charging unit, an entrance bore through the connecting means to an internal pressure compartment provided with a rupture device, the rupture device configured to fail at a predetermined pressure difference between the pressure compartment and a barrel compartment in front of the fastening element, the charging unit being configured to supply pressurized gas to the pressure compartment through the entrance bore, in which the gas propels the fastening element out of the barrel unit through the barrel compartment and into the structure when the gas pressure in the pressure compartment exceeds the predetermined pressure.

The rupture device may comprise a rupture disc. The rupture device may comprise a rupture bolt provided with a weakened portion forming an incipient weakening. Said predetermined pressure difference may be in the range from 1200 to 1500 bar (120 to 150 MPa).

The barrel unit may comprise a mouth portion and a first sealing member at the mouth portion may be configured to burst when the fastening element is propelled out of the barrel unit and into the structure.

The barrel unit may comprise a second sealing member in a head between the entrance bore and a fastening bore, the second sealing member may be configured to burst when the charging unit charges the barrel unit with pressurized gas or when the barrel unit is connected to the charging unit.

In a second aspect the invention concerns a charging unit for charging a pressure compartment of a barrel unit with pressurized gas propelling a fastening element into a structure submerged in water. The charging unit comprises a hydraulic pipe, an adapter at a coupling end and a hydraulic coupling unit at an opposite inlet end, a piston slidable between the adapter and the hydraulic coupling unit, a compression chamber between the piston and the adapter, the compression chamber configured to be at least partly filled with gas, a charging channel from the compression chamber through the adapter configured to be connected to an entrance bore of the barrel unit, the piston is configured to be displaced by hydraulic force in a direction toward the adapter, thereby charging the barrel unit with pressurized gas.

The charging unit may comprise a gas passage for introducing gas into the compression chamber, which gas passage may be configured to receive gas from a gas source. The hydraulic coupling unit may be adapted for receiving pressurized hydraulic fluid from a hydraulic drive unit.

In a third aspect the invention concerns a device for forcing a fastening element into a structure submerged in water. The device comprises the barrel unit as described previously, and the charging unit as described previously.

The device may further comprise a control unit configured to control a displacement of the piston such that the piston is displaced in a direction toward the adapter. The device may further comprise a control unit configured to control receipt of gas in the compression chamber from the gas source.

In a fourth aspect the invention concerns a system for forcing a fastening element into a structure submerged in water, wherein the system comprises the device as described previously, and the means for displacing the piston in the direction toward the adapter, thereby charging the pressure compartment of the barrel unit with pressurized gas.

The system may further comprise the gas source for introducing gas into the compression chamber of the charging unit.

In a fifth aspect the invention concerns a method of forcing a fastening element into a structure submerged in water by means of a device. The device comprises a barrel unit housing the fastening element, and a charging unit adapted to provide pressurized gas to the barrel unit, wherein the method comprises:

- connecting the barrel unit to the charging unit; and

- activating the charging unit for providing pressurized gas to a pressure compartment of the barrel unit, until a predetermined gas pressure difference between pressure in the pressure compartment and pressure in a barrel compartment in front of the pressure compartment is obtained, in which a rupture device fails and pressurized gas propels the fastening element out of the barrel unit and into the structure.

The charging unit may comprise a gas passage for introduction of gas to a compression chamber, the method further comprises:

- deactivating the charging unit;

- replacing a used barrel unit with a replacement barrel unit;

- introducing gas into the compression chamber; and

- displace a piston towards a hydraulic coupling unit to re-activate the charging unit.

The object of the invention is further obtained by means of use of a barrel unit, a charging unit, a device and a system according to any of above embodiments.

Brief description of drawings

In the following is described examples of preferred embodiments illustrated in the accompanying drawings, wherein:

Fig. 1 shows a system for forcing a fastening element into a structure submerged in water according to the invention, the system comprises a device;

Fig. 2A shows in a side view the device in figure 1, the device comprises a barrel unit and a charging unit;

Fig. 2B-D show in the same scale as figure 2A a sectional drawing along section A-A on the device in figure 1 according to a first embodiment of the invention, the device comprises a barrel unit and a charging unit;

Fig. 3 shows in a larger scale the barrel unit shown in figure 2B;

Fig. 4 shows in the same scale as figure 3, the charging unit in figure 2B;

Fig. 5 shows in perspective and in a larger scale the barrel unit; and

Fig. 6 shows in a larger scale a sectional drawing of the barrel unit according to a second embodiment of the invention.

Detailed description of the invention

In the drawings, the reference numeral 1 indicates a system for forcing a fastening element 9 into a structure 90 submerged in water 99. The system 1 comprises a device 10 comprising a barrel unit 2 and a charging unit 3. The system 1 furthermore comprises a control unit 11 and means for displacing a piston 4 of the charging unit 3, such as a hydraulic drive unit 13, see figure 1. The system 1 further comprises a gas source 15, such as a gas container, connected to the device 10 and arranged at a separate location from the device 10. The gas is for example air, nitrogen, carbon dioxide or an inert gas, such as helium, argon, or a mixture thereof.

The hydraulic drive unit 13 may preferably be at a separated location from the device 10, such as at a Remotely Operated Vehicle 17, also denoted ROV. Thereby, enabling a compact design of the device 10 which facilitates manoeuvring and handling of the device 10. The Remotely Operated Vehicle 17, the control unit 11, the hydraulic drive unit 13 and the gas source 15 are schematic illustrated as boxes in figure 1.

In the disclosed embodiment, the control unit 11 is located at the Remotely Operated Vehicle 17. However, it shall be understood that the control unit 11 alternatively may be arranged in at or in direct connection to the charging unit 3.

The barrel unit 2 is a replaceable part enclosing the fastening element 9. The barrel unit 2 is configured to be connected to the charging unit 3 that charge the barrel unit 2 with pressurized gas.

The barrel unit 2 comprises a barrel body 20. A barrel bore 21 forms a through hole in the barrel body 20. A mouth portion 22 of the barrel bore 21 is closed by a first sealing member 23 which is fixed to the barrel body 20 by a fastener 24. The first sealing member 23 prevents water 99 from entering the barrel bore 21 when the barrel unit 2 is submerged in water 99.

The barrel unit 2 is at an inlet 25 opposite the mouth portion 22 provided with an insert 26. The insert 26 is threadly fastened to the inlet 25. The insert 26 forms a head 27 which abuts the barrel body 20 when the insert 26 is screwed fully into the inlet 25. A pin 28 protrudes from the head 27. According to the embodiment shown in figures 2B-D and 3, the insert 26 is provided with a fastening bore 261 from the head 27 to an end portion 29 opposite of the head 27 (see figure 3). The insert 26 is provided with an entrance bore 263 through the head 27 and pin 28. The diameter of the fastening bore 261 is larger than the diameter of the entrance bore 263. The longitudinal axis of the barrel body 20, the barrel bore 21, the fastening bore 261 and the entrance bore 263 coincide with an axis 98. The insert 26 is provided with an external first gasket 291 shown as an external O-ring at the end portion 29. The insert 26 is provided with an external second gasket 281 shown as an external O-ring at the pin 28. A second sealing element 232 is positioned in the head 27 between the entrance bore 263 and the fastening bore 261.

The first sealing member 23 and the second sealing member 232 together enable a replacement barrel unit 2 to be attached to the charging unit 3 without water entering the barrel bore 21. The second sealing member 232 is configured to burst when the charging unit 3 charge the barrel unit 2 with pressurized gas through the entrance bore 263, which will be described below. Alternatively (not shown), the second sealing member 232 may be positioned at an entrance of the entrance bore 263 and is pierced when the barrel unit 2 is connected to the charging unit 3. The charging unit 3 may be provided with a piercing means for piercing the second sealing member 232.

The insert 26 is shown with a first gas channel 265 forming a channel from the head 27 to the end portion 29. The first gas channel 265 is coaxial and separate to the fastening bore 261. A radial passage 267 connects the first gas channel 265 to the fastening bore 261 close to the second sealing member 232 as shown in the enlarged portion of figure 3.

The head 27 forms externally a connection means 270 for releasably connecting the barrel unit 2 to the charging unit 3. The connection means 270 may be a bayonet fitting, as shown in the drawings, a snap fitting such as a quick release coupling for pressurized gas or hydraulic oil (not shown) possibly adapted to the present work pressure, or a threaded fitting (not shown), and etcetera.

The barrel unit 2 comprises an internal trigger device 5 positioned in the barrel bore 21. The trigger device 5 comprises in the embodiment shown in figures 2B-D and figure 3, a rupture device 50 and a holder 53.

The rupture device 50 shown as a rupture bolt 51, forms a threaded fastening portion 510 and an opposite threaded holding portion 511. A weakened portion 515 forming an incipient weakening is positioned between the fastening portion 510 and the holding portion 511. The weakened portion 515 is shown as a portion with a smaller diameter than the other portions of the rupture bolt 51. The holder 53 comprises a threaded indentation 531 and an opposite recess 539. The fastening portion 510 is threadly connected to the fastening bore 261. The holding portion 511 is threadly connected to the indentation 531. The fastening element 9 is positioned into the recess 539. The fastening element 9 is kept in place in the recess by friction between the surface of the fastening element 9 and the surface of the recess 539. The holder 53 comprises an external sliding gasket 55. The sliding gasket 55 is shown as an O-ring. The sliding gasket 55 seals in a gas tight manner between the inner wall of the barrel body 20 and the outer surface of the holder 53.

The holder 53 divides the barrel bore 21 in a barrel compartment 57 between the first sealing member 23 and the sliding gasket 55, and a pressure compartment 59 between the sliding gasket 55 and the second sealing element 232.

The rupture device 50 is configured to fail at a predetermined pressure difference between the barrel compartment 57 and the pressure compartment 59.

In one embodiment the fastening element 9 and the holder 53 may be made of one piece of material (not shown). In this embodiment, the fastening element 9 comprises the external sliding gasket 55. The fastening element 9 further comprises a threaded indentation 531 for connecting the holding portion 511 of the rupture bolt 51.

The charging unit 3 comprises a hydraulic pipe 30. The charging unit 3 forms a coupling end 31 and an opposite inlet end 39. An adapter 32 which forms a coupling unit for the barrel unit 2, is fastened internally in the coupling end 31. A hydraulic coupling unit 34 is inserted in the inlet end 39. The hydraulic coupling unit 34 is locked to the hydraulic pipe 30 by an external nut 36. The piston 4 is positioned within the hydraulic pipe 30. The piston 4 is adapted to slide between the adapter 32 and the hydraulic coupling unit 34. The piston 4 divides the hydraulic pipe 30 in a compression chamber 42 between the adapter 32 and the piston 4, and a hydraulic chamber 44 between the piston 4 and the hydraulic coupling unit 34, as shown in figures 2B-D, and figure 4.

The adapter 32 forms at a free end a connection portion 320 which is complementary to the connection means 270. The connection portion 320 comprises an indentation 321 which is complementary to the pin 28. A charging channel 323 connects the indentation 321 with the compression chamber 42. The adapter 32 is provided with an external third gasket 325 shown as an external O-ring. The third gasket 325 seals in a gas tight manner between the inner wall of the hydraulic pipe 30 and the outer surface of the adapter 32.

The hydraulic coupling unit 34 comprises at a free end a hydraulic coupling means 340 for a hydraulic hose 130 (see figure 1). A hydraulic channel 343 connects the coupling means 340 with the hydraulic chamber 44. The hydraulic coupling unit 34 is provided with an external fourth gasket 345 shown as an external O-ring. The fourth gasket 345 seals in a fluid tight manner between the inner wall of the hydraulic pipe 30 and the outer surface of the hydraulic coupling unit 34.

The charging unit 3 is provided with an external mounting bracket 6. The mounting bracket 6 is provided with through holes 61 (see figure 1 and 2A) for mounting the charging unit 3 to a suitable support such as a ROV 17. The mounting bracket 6 is provided with a second gas channel 63. The second gas channel 63 is in one end in fluid connection with the compression chamber 42 via a gas passage 38 through the wall of the hydraulic pipe 30. In the opposite end the second gas channel 63 is provided with a gas coupling means 64 for a gas hose 150 (see figure 1) which is connected the gas source 15. A fifth gasket 65 shown as an O-ring, seals in a gas tight manner a connection between the second gas channel 63 and the gas passage 38. A gas check valve (not shown) blocks gas from flowing through the gas passage 38 and gas channel 63 in a direction towards the gas source 15.

The barrel unit 2 is shown in a second embodiment in figure 6. The trigger device 5 comprises the holder 53 and the external sliding gasket 55 as described previously. The insert 26 is threadly fastened to the inlet 25. The insert 26 forms a head 27 which abuts the barrel body 20 when the insert is screwed fully into the inlet 25. A pin 28 protrudes from the head 27. The insert 26 is provided with an entrance bore 263 through the head 27 and pin 28 as described previously. The insert 26 is in this embodiment elongated and forms an elongated pressure housing 590. At the end portion 29 of the insert 26, the insert 26 is provided with a rupture device 50 shown as a rupture disc 52. The rupture disc 52 seals the internal of the pressure housing 590 from the barrel bore 21. The pressure housing 590 and the rupture disc 52 form the pressure compartment 59.

In the first embodiment the trigger device 5 is assembled by fastening the fastening portion 510 of the rupture bolt 51 in the fastening bore 261 of the insert 26. The holding portion 511 of the rupture bolt 51 is fastened in the indentation 531. Thereby the insert 26, the rupture bolt 51 and the holder 53 form a rigid assembly. The fastening element 9 is positioned in the holder 53. The fastening element 9, the trigger device 5 and the insert 26 is inserted in the barrel bore 21 at the inlet 25. The mouth portion 22 of the barrel bore 21 is closed by positioning the first sealing member 23 in the fastener 24 and by fixing the fastener 24 to the barrel body 20. The barrel unit 2 is then preloaded.

In the second embodiment the trigger device 5 is assembled by fastening the rupture disc 52 to the end portion of the insert 26. The fastening element 9 is positioned in the holder 53. The holder 53 and the fastening element 9 is inserted in the barrel bore 21 at the inlet 25. The insert 26 is then inserted in the barrel bore 21 at the inlet 25 and the insert 26 pushes the holder 53 further into the barrel bore 21. The mouth portion 22 of the barrel bore 21 is closed by positioning the first sealing member 23 in the fastener 24 and by fixing the fastener 24 to the barrel body 20. The barrel unit 2 is then preloaded. The first sealing member 23 and the fastener 24 are not shown in figures 5 and 6.

The preloaded barrel unit 2 is fastened to the charging unit 3 as shown in figures 1, 2A-D. When it is desirable to fire off the fastening element 9 to force it into a dived structure 90, the gas source 15 is activated. Gas flows through the gas hose 150, gas channel 63, gas passage 38 and into the compression chamber 42. The pressure within the compression chamber 42 equals the pressure in the gas source 15. The pressure within the compression chamber 42 may be less than the pressure in the gas source 15 if the system 1 is provided with a gas pressure reduction valve (not shown). The system is provided with the gas check valve that blocks gas from flowing in the opposite direction towards the gas source 15.

The gas pressure in the compression chamber 42 may burst the second sealing element 232. Thereby gas flows from the compression chamber 42 through the charging channel 323 and entrance bore 263 and into the pressure compartment 59. The gas pressure is a first gas pressure which is less than the gas pressure needed to burst the rupture device 50.

The hydraulic drive unit 13 is activated. The hydraulic pressure in the hydraulic chamber 44 increases until it equalizes the gas pressure in the compression chamber 42. Thereafter with increased hydraulic pressure the piston 4 is forced to slide towards the adapter 32. The volume of the compression chamber 42 diminishes. The volumes in the charging channel 323, the entrance bore 263 and the pressure compartment 59 are constant. The total gas volume diminish with the reduction of volume in the compression chamber 42. The gas pressure increases gradually as the piston 4 is displaced towards the adapter 32. The gas pressure will reach a maximum pressure before the piston 4 abuts the adapter 32 as shown in figure 2C. The maximum gas pressure is larger than the pressure needed to burst the rupture device 50. This is shown in figure 2D where the rupture bolt 51 has broken in the weakened portion 515. The holder 53 is then free to move and will be displaced with high speed and great force towards the mouth portion 22. The fastening element 9 breaks the first sealing member 23. The fastening element 9 and the holder 53 may together continue through the water 99. The fastening element 9 penetrates into the structure 90 with great force. It may be an advantage that the holder 53 stay together with the fastening element 9. The weight of the holder 53 will contribute to the momentum of the impact. The holder 53 may in an alternative embodiment be stopped by an internal shoulder (not shown) at the mouth portion 22. The fastening element 9 will then release from the holder 53, continue through the water 99 and into the structure 90.

The method for firing off the fastening element 9 is similar with the barrel unit 3 according to the second embodiment. When the gas pressure reaches the critical level, the rupture disc 52 bursts and high-pressure gas fills the volume formed by the barrel bore 21, the holder 53 and the insert 26. The sliding gasket 55 blocks for the gas such that the gas cannot pass the holder 53. The holder 53 and the fastening element 9 is displaced forward in the barrel compartment 57 with high speed and with great force as explained above.

After the fastening element 9 has been fired off, the barrel unit 2 has been consumed and a pre-loaded replacement barrel unit 2 is to be attached to the charging unit 3 for continued operation.

After firing off the fastening element 9, the piston 4 is displaced to its initial position at the hydraulic coupling unit 34. This may in one embodiment be done by reversing a hydraulic pump (not shown) such that hydraulic fluid is drained from the hydraulic chamber 44 and to the hydraulic drive unit 13. Gas enters the compression chamber 42 from the gas source 15 to avoid influx of water to the expanding volume of the compression chamber 42. In an alternative embodiment gas enters the compression chamber 42 and a valve (not shown) blocks the charging channel 323. A valve (not shown) in a hydraulic supply line opens. The gas pressure is larger than the hydraulic pressure such that the piston 4 is displaced towards the hydraulic coupling unit 34. Evacuated hydraulic fluid flows back to the hydraulic drive unit 13. As an alternative, evacuated hydraulic fluid flows into a dump receptacle.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

C l a i m s

1. A barrel unit (2) for forcing a fastening element (9) into a structure (90) submerged in water (99),

c h a r a c t e r i s e d i n that the barrel unit (2) comprises a barrel body (20) and a barrel bore (21) within the barrel body (20) adapted to house the fastening element (9), the barrel bore (20) being sealed from the ambient surrounding, a connection means (270) for releasably connecting the barrel unit (2) to a charging unit (3), an entrance bore (263) through the connecting means (270) to an internal pressure compartment (59) provided with a rupture device (50), the rupture device (50) configured to fail at a predetermined pressure difference between the pressure compartment (59) and a barrel compartment (57) in front of the fastening element (9),

the charging unit (3) being configured to supply pressurized gas to the pressure compartment (59) through the entrance bore (263), in which the gas propels the fastening element (9) out of the barrel unit (2) through the barrel compartment (57) and into the structure (90) when the gas pressure in the pressure compartment (57) exceeds the predetermined pressure.

2. The barrel unit (2) according to claim 1, wherein the rupture device (50) comprises a rupture disc (52).

3. The barrel unit (2) according to claim 1, wherein the rupture device (50) comprises a rupture bolt (51) provided with a weakened portion (515) forming an incipient weakening.

4. The barrel unit (2) according to any of the previous claims, wherein the barrel unit (2) comprises a mouth portion (22) and a first sealing member (23) at the mouth portion (22) configured to burst when the fastening element (9) is propelled out of the barrel unit (2) and into the structure (90).

5. The barrel unit (2) according to any of the previous claims, wherein the barrel unit (2) comprises a second sealing member (232) in a head (27) between the entrance bore and a fastening bore (261), the second sealing member (232) is configured to burst when the charging unit (3) charges the barrel unit (2) with pressurized gas or when the barrel unit (2) is connected to the charging unit (3).

6. A charging unit (3) for charging a pressure compartment (59) of a barrel unit (2) with pressurized gas propelling a fastening element (9) into a structure (90) submerged in water (99), c h a r a c t e r i s e d i n that the charging unit (3) comprises a hydraulic pipe (30), an adapter (32) at a coupling end (31) and a hydraulic coupling unit (34) at an opposite inlet end (39), a piston (4) slidable between the adapter (32) and the hydraulic coupling unit (34), a compression chamber (42) between the piston (4) and the adapter (32), the compression chamber (42) configured to be at least partly filled with gas, a charging channel (323) from the compression chamber (42) through the adapter (32) configured to be connected to an entrance bore (263) of the barrel unit (2), the piston (4) is configured to be displaced by hydraulic force in a direction toward the adapter (32), thereby charging the barrel unit (2) with pressurized gas.

7. The charging unit (3) according to claim 6, wherein the charging unit (3) comprises a gas passage (38) for introducing gas into the compression chamber (42), which gas passage (38) is configured to receive gas from a gas source (15).

8. The charging unit (3) according to any of claim 6 and 7, wherein the hydraulic coupling unit (34) is adapted for receiving pressurized hydraulic fluid from a hydraulic drive unit (13).

9. A device (10) for forcing a fastening element (9) into a structure (90) submerged in water (99), wherein the device (10) comprises a barrel unit (2) according to any of claims 1-6 and the charging unit (3) according to any of claims 7-9.

10. The device (10) according to claim 9, wherein the device (10) comprises a control unit (11) configured to control a displacement of the piston (4) such that the piston (4) is displaced in a direction toward the adapter (32).

11. The device (10) according to any of claims 9 and 10, wherein the device (10) comprises a control unit (11) configured to control receipt of gas in the compression chamber (42) from the gas source (15).

12. A system (1) for forcing a fastening element (9) into a structure (90) submerged in water (99), wherein the system (1) comprises the device (10) according to any of claims 9 to 11 and the means for displacing the piston (4) in the direction toward the adapter (32), thereby charging the pressure compartment (59) of the barrel unit (2) with pressurized gas.

13. The system (1) according to claim 12, wherein the system (1) further comprises the gas source (15) for introducing gas into the compression chamber (42) of the charging unit (3).

14. A method of forcing a fastening element (9) into a structure (90) submerged in water (99) by means of a device (10), wherein the device (10) comprises a barrel unit (2) housing the fastening element (9), and a charging unit (3) adapted to provide pressurized gas to the barrel unit (2), wherein the method comprises:

- connecting the barrel unit (2) to the charging unit (3); and

- activating the charging unit (3) for providing pressurized gas to a pressure compartment (59) of the barrel unit (2), until a predetermined gas pressure difference between pressure in the pressure compartment (59) and a barrel compartment (57) in front of the pressure compartment (59) is obtained, in which a rupture device (50) fails and pressurized gas propels the fastening element (9) out of the barrel unit (2) and into the structure (90).

15. The method according to claim 14, wherein the charging unit (3) comprises a gas passage (38) for introduction of gas to a compression chamber (42), the method further comprises:

- deactivating the charging unit (3);

- replacing a used barrel unit (2) with a replacement barrel unit (2);

- introducing gas into the compression chamber (42); and

- displace a piston (4) towards a hydraulic coupling unit (34) to re-activate the charging unit (3).