This invention relates to a swivel joint.

In the search for oil below sea, oil producers drill into the sea bed. The sea bed may be at a very substantial distance, for example more than 2 kilometres, below sea level. These substantial distances cause problems in getting drilling equipment to the sea bed. Pre-drilling equipment may include what is known as a pipe line end termination or a pipe line end manifold. The pre-drilling equipment is fed to the sea bed on a steel hose or pipe. The pre- drilling eqϋipmentimay settle at an angle to the sea bed. Often a swivel joint allowing several relevant rotations of the pre-drilling equipment and the hose would be an advantage. However a problem occurs in that the swivel joint needs to last for the duration of the pipe work, which may be up to 30 years. Swivel joints with elastomeric seals cannot be relied upon because the elastomeric seals typically only have a life of 10 - 15 years. Metal seals would have the required life of up to 30 years but metal seals are only used for static sealing arrangements. This is because rotation would cause the metal seals to gall, that is to rub against abutting surfaces, become rough, and soon fail as seals. This is especially so under the high working pressures that are typically employed in oil producing drilling operations below sea level where the pressures may be 5000 PSI. It is an aim of the present invention to reduce the above mentioned problem.

Accordingly, in one non-limiting embodiment of the present invention there is provided a swivel joint comprising a housing, a first pipe portion for a fluid, a second pipe portion for the fluid, first and second bearings which enable 360° relative rotation of the second pipe portion with respect to the first pipe portion, a metal seal for effecting a seal between the housing and the second pipe portion, a first test conduit which is for testing the sealing of the swivel joint and which extends through the housing to a position adjacent a first side of the metal seal, a second test conduit which is for testing the swivel joint and which extends through the housing to a position adjacent a second side of the metal seal, and the swivel joint being such that the metal seal is a pressure energiseable metal seal which is energised by pressure in the swivel joint, the first side of the metal seal faces towards the first pipe portion, and the second side of the metal seal faces towards the second pipe portion.

The swivel joint of the present invention is advantageous in a number of aspects. Firstly, the use of the metal seal in a rotational arrangement afforded by the swivel joint provides the required seal life whilst allowing the required relative rotation of the swivel joint and its hose or hoses during installation below sea. Secondly, the first and second test conduits enable the testing of the swivel joint before use in the sea, and also at the time of installation on the sea bed. The testing on the sea bed can be effected using a remote operating vehicle with hydraulic stab connectors. Thirdly, the use of the first and second bearings enables the swivel joint to be robust in operation and to be such that the very substantial pressures experienced by the swivel joint during use are not such as to stress one part of the swivel joint with respect to another part of the swivel joint such that seals would tend to fail.

In the swivel joint of the present invention, the first pipe portion may be an outlet and the second pipe portion may be an inlet, or vice versa.

Usually, the first test conduit will extend radially through the housing but it may be otherwise directed if desired. Alternatively or additionally, the second test conduit will usually extend radially through the housing but it may be otherwise directed if desired.

The metal seal may be a C-metal seal, a U-metal seal, an oval metal seal, or a tapered metal seal. Other types of metal seal may be employed.

The metal seal is preferably made of stainless steel. A preferred stainless steel is that known as type 316 stainless steel. Other metals may be employed.

The housing may be a nickel alloy housing. Other metal alloys may be employed.

The first and the second bearings are preferably thrust bearings, spherical bearings, or taper roller bearings. Other types of bearings may be employed.

The swivel joint may include environmental seals, and a third test conduit for testing the sealing of the environmental seals. The environmental seals may be elastomeric seals. The environmental seals may be elastomeric/polytetrafluoroethylene slipper seals. Usually, the third test conduit will extend radially through the housing but is may extend otherwise if desired.

Preferably, the third test conduit is positioned at the end of the swivel joint farthest from the first test conduit. The third test conduit may be positioned elsewhere if desired.

The housing may comprise first, second and third parts which are bolted together.

The present invention also extends to the combination of the swivel joint of the invention and at least one length of flexible pipe.

The present invention also extends to the combination of the swivel joint of the invention, at least one length of flexible pipe, and an end member which is replaceable or modifiable to receive a drill for drilling into, sea beds.

The present invention also extends to the combination of the swivel joint of the invention, at least one length of flexible pipe, and a drill for drilling into sea beds.

Embodiments of the invention will now be described solely by way of example and with reference to the accompanying drawings in which:

Figure 1 is a cross sectional view, with an amplified portion, of a swivel joint of the present invention;

Figure 2 is a perspective view of the swivel joint shown in Figure 1 ;

Figure 3 is an amplified view of part of the swivel joint as shown in Figure 2;

Figure 4 is a side view of the swivel joint in use;

Figure 5 is a top view of the swivel joint in use; and Figure 6 shows an alternative metal seal for effecting a seal in the swivel joint.

Referring to Figure 1 , there is shown a swivel joint 2 comprising a housing 4, a first pipe portion 6 for a fluid, and a second pipe portion 8 for the fluid. A first bearing 10 and a second bearing 12 are provided in the housing 4. The first and second bearings 10, 12 enable 360° relative rotation of the second pipe portion 8 with respect to the first pipe portion 6. As shown in Figure 1 , the second pipe portion 8 is able to rotate with respect to the first pipe portion 6. The second pipe portion 8 thus forms a rotateable sleeve.

The swivel joint 2 also comprise a metal seal 14 for effecting a seal between the housing 4 and the rotatable second pipe portion 8.

The swivel joint further comprises at first test conduit 16. The first test conduit 16 is for testing sealing of the swivel joint 2. The first test conduit 16 extends through the housing 4 to a position adjacent a first side 18 of the metal seal 14.

As shown in Figure 2, the swivel joint 2 further comprises a second test conduit 20. The second test conduit 20 is for testing sealing of the swivel joint 2. The second test conduit 20 extends through the housing 4 to a position adjacent a second side 22 of the metal seal 14.

The swivel joint 2 is such that the metal seal 14 is a pressure energiseable metal seal 14 which is energised by pressure in the swivel joint 2. The fluid will usually be a hydraulic fluid so that the pressure will be hydraulic pressure. The pressure may however be another type of pressure depending upon the fluid in the swivel joint 2 and the particular use to which the swivel joint 2 is put. The first side 18 of the metal seal 14 faces towards the first pipe portion 6. The second side 22 of the metal seal 14 faces towards the second pipe portion 8.

As shown in Figure 1 , the first test conduit 16 extends radially through the housing 4. The second test conduit 20 also extends radially through the housing 4. The metal seal 20 is made of 316 stainless steel. Other materials may be employed. The housing 4 is a nickel alloy housing but other materials for the housing 4 may be employed. The first and second bearings 10, 12 are thrust bearings, spherical bearings or any other suitable and appropriate type of bearings.

As shown in Figure 3, the swivel joint 2 includes two environmental seals 24, 26, and a third test conduit 28 for testing the) sealing of the environmental seals 24, 26. The environmental seals 24, 26 are made of an elastomerici material. The third test conduit 28 extends radially through the housing 4. The third test conduit 28 is positioned at the end 30 of the swivel joint 2 farthest from the first test conduit 16.

The housing 4 comprises a first part 32, a second part 34 and a third part 36. The first, second, and third parts 32, 34, 36 are bolted together by bolts 38, 40.

Referring to Figures 4 and 5, the swivel joint 2 is shown being deployed from a boat 42 and connected to flexible pipes 44, 46 leading to a sea bed 48 beneath a sea 50. Figure 4 shows how the flexible pipes 44, 46 are subject to axial tension 52, a bending moment 54 and a shear force 56. Figure 5 shows how the flexible pipes 44, 46 are subject also to a bending moment 58. The swivel joint 2 is able to swivel to accommodate for the various forces on the flexible pipes 44, 46. The flexible pipe 44 is able to connect to the second pipe portion 8 of the swivel joint 2, and the flexible pipe ^' 46 is able to connect to the first pipe portion 6 of the swivel joint 2, or vice versa.

As can be seen from the enlarged portion in Figure 1 , the metal seal 14 is a ring on a hard face clad surface. Two environmental seals 60, 62 are provided one on either side of the metal seal 14. The environmental seals 60, 62 are made of the same material as the environmental seals 24, 26. As also shown in Figure 1 , the second pipe portion 8 which forms a rotating sleeve has a weld end 64. This weld end 64 could alternatively be a flanged end or an elbow-style end. '

Prior to installation of the swivel joint 2, the swivel joint 2 is able to be tested on dry land to high pressure to prove the integrity of the swivel joint 2 and in particular the metal seal 14 and the environmental seals 24, 26, 60, 62. During installation, there is no internal pressure in the swivel joint 2. Thus the metal seal 14 is not active and it is able to rotate freely without rubbing and causing abrasion on the metal seal 14. When the pipe 46 has settled on the sea bed 48 and is appropriately positioned, the first, second and third test conduits ϊi§, 20, 28 which were previously used to check the integrity of the seals, for example on dry land or on the boat 42, can now be accessed by a remote operating vehicle (not shown). The remote operating vehicle will have hydraulic stab connectors for connecting to the first, second and third test conduits 16, 20, 28. With a hydraulic fluid flow to the first test conduit 16, the metal seal 14 is pressure energised and locks into place. Any leakage is now able to be detected at the second test conduit 20 which is also connected by the hydraulic stab connectors to the remote operating vehicle. With the metal seal 14 activated, the swivel joint 2 is fixed in position as it is intended to be, and it forms a fixed hose or pipe connection between the flexible pipes 44, 46 and is able to take all of the associated loads. The remote operating vehicle is then able to be disconnected from the first and second test conduits 16, 20 at the hydraulic stab connectors. The first and second test conduits 16, 20 are then able to be plugged with high pressure plugs. At the completion of the test on the environmental seals 24, 26 using the third test conduit 28, the remote ,l operating vehicle is also able to be disconnected at the hydraulic stab ! connector and the third test conduit 28 similarly plugged with a high pressure plug. ^■

The swivel joint 2 is able to be robustly manufactured, with the first and second bearings 10, 12 acting to balance the forces on the swivel joint 2.

Referring now to Figure 6, there is shown an alternative metal seal 66 to the metal seal 14 shown in Figure 1. The metal seal 66 has a wedge- shaped portion 68 which moves along a conical section 70 of the sleeve 8. A seal 72 which is shown as an O-ring seal of circular cross section, is positioned as shown between two members 74 which slide.

In operation, the metal seal 66 is activated by application of pressure to the first test conduit 16. This application of pressure moves the seal 72 and also the metal seal 66 to the right as shown in Figure 6. As the metal seal 66 moves to the right, its conical portion 68 moves up the conical section 70 of the pipe portion 8. The metal seal 66 is forced against the surface of the first part 32 of the housing 4 to make the required operational seal. The metal seal 66 is held in place by frication.

The metal seal 66 is de-activated by applying pressure to the third test conduit 28. This application of pressure causes the metal seal 66 to move to the left as shown in Figure 6. The deactivating pressure may occur between, for example, 1000 - 3000 psi, and it may be up to, for example, a maximum of 7500 psi. In operation, the deactivation occurs with a click, and fluid from the third test conduit 28 appears at the second test conduit 20. The test conduit 20 enables the metal seal 66 to be tested independently of the seal 72. ' >

Ih Figure -6, similar parts as in Figure 1 have been given ¹ the same reference numerals for ease of comparison and understanding. In Figure 6, for clarity, the first, second and third test conduits 16, 20, 28 have been shown diagrammatically and aligned in a single plane. In reality, the first, second and third test conduits 16, 20, 28 are spaced at 30° around the main swivel axis of the swivel joint.

In a further modification of the invention (not shown) an additional O- ring seal like the seal 72 may be employed on the right side of the metal seal 66 as shown in Figure 6. This additional O-ring seal may be positioned between two sliding members 74 in the same manner as for the seal 72. It is also possible to achieve the same result using two smaller diameter O-rings (not shown) located in grooves machined in the metal seal 60, one O-ring sliding against the outer sealing surface and the other O-ring sliding against the inner sliding surface in the location position of the seal 72. The sliding members 74 for the seal 72 and also for the seal (not shown) on the right of the metal seal 66 are preferably made of polytetrafluoroethylene but they may be made of other materials if desired.

It is to be appreciated that the embodiments of the invention described above with reference to the accompanying drawings have been given by way of example only and that modifications may be effected. Thus, for example a facility may be provided to lock the bearing rotation. Alternatively, a simple external bolt arrangement may be employed. The metal seal 14 may be of a C-shape, a U-shape', or an oval shape. The environmental seals 24, 26, 60, 62 may be O-ring elastomeric seals with polymer slipper seals. The bearings' '10, 12 may be secured with a locking nut (not shown) to put a small pre-load onto the bearings 10, 12 during assembly. If the bearings 10, 12 are taper roller bearings, then the pre-load applied by the nut takes out any float or slack, and better enables the taper roller bearings to carry axial and bending loads, which may be considerable. For high pressure applications, the environmental seals 24, 26, 60, 62 may alternatively be a composition of a polymer seal such for example as polytetrafluoroethylene with a metal back-up ring to support the polymer. Hardened sealing surfaces are more durable. A typical example would be alloy 625 welded to carbon steel, the alloy then being machined back to size to suit the metal seal 14. Individual components shown in the drawings are not limited to use in their drawings and they may be used in other drawings and in all aspects of the invention.