Abstract: A subsea-replaceable fuse assembly has at least one fuse and a wet-mateable fuse connector element. The connector element is arranged to connect the fuse assembly to a subsea electrical load requiring protection of the fuse. The fuse connector element has conductor elements that are electrically connected to the fuse. A corresponding method of protecting a subsea electrical load includes connecting a fuse to the load underwater in a wet-mating operation effected between connector elements that are electrically connected, respectively, to the fuse and to the load.

Abstract: An injection molding apparatus has a mold tool that is positioned around a field joint of a pipeline to define a mold cavity. Two or more pumping chambers communicate with the mold tool. Each chamber is expansible to draw in molten polymer and contractible to drive the polymer into the mold cavity. Expansion of one chamber is synchronized with contraction of another chamber. The operation of supply and injection valves associated with the chambers is also synchronized, both with each other and with expansion and contraction of the chambers. In the embodiment described, two pumping chambers are defined within a common pressurizing cylinder, in which the chambers are separated by a piston. The piston is movable within the cylinder to determine and to synchronize expansion and contraction of the chambers.

Abstract: A method of adjusting buoyancy of an Unmanned Underwater Vehicle (UUV) includes measuring buoyancy drift of the UUV when underwater. After docking the UUV with a subsea station, a quantity of a flowable buoyancy-adjustment material held onboard the UUV is changed by transferring that material from the station to the UUV or from the UUV to the station. A buoyancy adjustment system for a UUV includes: an onboard tank for holding a variable quantity of the buoyancy-adjustment material and upwardly-opening and downwardly-opening passageways communicating with the tank for transferring the buoyancy-adjustment material to or from the UUV. The subsea station includes: a dock for docking a UUV; a holding tank for holding the buoyancy-adjustment material; and at least one upwardly-opening or downwardly-opening passageway aligned with the dock and communicating with the holding tank for transferring the buoyancy-adjustment material to or from the docked UUV.

Abstract: A thermoplastics injection molding process coats a field joint of a pipeline by positioning a mold tool around the field joint to define a mold cavity. Thermoplastics material injected into the mold cavity forms a field joint coating that will set in the mold cavity. As the thermoplastics material shrinks in the mold cavity while the field joint coating sets, compacting pressure is applied radially inwardly within the mold cavity against a radially outer side of the field joint coating. A compacting fluid introduced into the mold cavity between the mold tool and the field joint coating may be used to apply pressure against the field joint coating. This accelerates and controls cooling of the field joint coating while maximizing quality.

Abstract: An inspection, monitoring, maintenance or construction task is performed on a subsea structure by using an underwater vehicle to carry a submersible package to the subsea structure. The package comprises a tool or sensor arranged to perform the required task on the subsea structure, and an on-board power unit and controller arranged to power and control the tool or sensor. The package is transferred from the underwater vehicle to be supported by the subsea structure. The underwater vehicle can then stand off from the package. While the package is supported by the subsea structure, the tool or sensor of the package performs the required task on the subsea structure, powered and controlled by the on-board power unit and controller of the package.

Abstract: A load absorber dampens relative movement between subsea bodies. The load absorber is cooperable with an actuating member such as a male piston element or a female cup on an opposed subsea body. The load absorber comprises a hollow structure defining an internal flow path for water. A flow restrictor acting on the flow path restricts a distal flow of water along the flow path from a proximal opening, caused by convergence between the actuating member and the load absorber. The flow restrictor comprises a shuttle element to restrict the flow path that is mounted to the structure for automatic movement from a first state to a second state in response to an increase in water pressure at the proximal opening. In the first state, the shuttle element effects greater restriction of the flow path than in the second state.

Abstract: A method protects a field joint of a pipeline, where chamfered edges of thermally-insulating parent coatings on conjoined pipe lengths are in mutual opposition about a longitudinally-extending gap. The method includes manufacturing an hourglass-shaped inner layer around the pipe lengths, which layer may be moulded. The inner layer extends longitudinally along the gap between the chamfered edges and at least partially overlies the chamfered edges. A thermally-insulating solid insert is assembled from two or more parts to lie in the gap surrounding the inner layer, and pressure is applied radially inwardly from the insert to the inner layer. An outer layer of molten material is manufactured around the insert to form a watertight barrier and to form one or more melted interfaces with the inner layer. Corresponding field joint arrangements are also disclosed.

Abstract: A turntable assembly for performing welding or other operations in a pivotably-mounted J-lay tower is disclosed. The assembly includes an annular turntable supported by a base frame to turn about a pipe string in use and a tilt-compensating mechanism acting on the base frame to level the turntable as the tower pivots in use. The tilt-compensating mechanism includes at least one support that is driveable up and down with respect to the tower. In the embodiment disclosed, the support is a carriage movable along an upright track that pivots with the tower.

Abstract: A method of coating a field joint of a pipeline places at least one body having a thermoplastics material around the field joint. The body is heated in a mold cavity around the field joint to effect thermal expansion of the thermoplastics material. Thermal expansion of the body in the mold cavity is constrained to apply elevated pressure between the body and pipe sections joined at the field joint. The elevated pressure improves bonding and fusing between the body, which forms a field joint coating, and the parent coatings and the exposed pipe sections of the pipe joints. The body need not be fully molten, which reduces the mold residence time including in-mold heating and cooling phases.

Abstract: A towable pipeline bundle for installation underwater at a subsea oil or gas production site has two or more bundled elongate elements, at least one of which is a flowline for carrying production fluid along the bundle. A rigid buoyancy pipe of polymer-composite material extends along and supports the bundled elongate elements. The buoyancy pipe has an internal buoyancy chamber and at least one port for introducing fluid into the buoyancy chamber. The buoyancy pipe is arranged to have positive buoyancy in seawater when its buoyancy chamber contains a fluid less dense than seawater. In this way, the buoyancy pipe confers substantially neutral buoyancy on a towable unit comprising the bundle. The unit can then be towed in mid-water to the production site and lowered there onto the seabed.

Abstract: A submersible mixing and sampling apparatus with submersible supply systems (12, 14) for first and second liquid components such as a thermoset resin and a curing agent is disclosed. Each supply system has a respective submersible tank (24) for holding a respective one of the liquid components. Submersible mixers (46, 48, 50) downstream of the supply systems mix the liquid components underwater to form a curable mixture for injection into a subsea chamber such as a tee (102). Submersible sampling devices downstream of the mixers take samples (94) of the mixture underwater before, during and after injection, and optionally also at the surface. The samples may be cured and tested underwater or may be lifted to the surface for testing. The apparatus may be mounted on a subsea skid (100) or basket.

Abstract: A hydraulically-powered subsea tool system has a tool (26) and a tool power unit (12). The tool (26) communicates with a first connector element (30) on a hydraulic drive circuit (82). The tool power unit (12) has a hydraulic supply circuit (88) communicating with a second connector element (20). The connector elements are wet-mated with each other to connect the circuits for powering the tool. The circuits are pressure-compensated by respective compensators (136,90). When the circuits are connected, a valve (140) is operable to transfer pressure compensation of one of the circuits from the compensator (136) of that circuit to the compensator (90) of the other circuit. The valve (140) suitably transfers pressure compensation of the drive circuit from a drive circuit compensator to a supply circuit compensator.

Abstract: A subsea drying system (10) for drying a chamber (12) underwater has an upstream piping (24, 26, 28) for conveying a pressurized drying fluid from a source (18) to the chamber (12); and downstream piping (36, 38, 40) for expelling liquid displaced from the chamber (12) by the drying fluid in an open-loop dewatering mode. In a closed-loop dehumidifying mode, a recirculation path (54) between the downstream piping (36, 38, 40) and the upstream piping (24, 26, 28) conveys drying fluid exiting the chamber (12) back into the chamber (12) after passing through a dehumidifier (58). A valve system selectively closes and opens the re-circulation path to expel displaced liquid when that path is closed and to recirculate drying fluid from the chamber (12) through the dehumidifier (58) to the upstream piping (24, 26, 28) when that path is open.

Abstract: A method provides power to a subsea equipment electrical system underwater, without a wet-mated electrical connection. The method includes temporarily coupling a rotary coupling element of a power source to the subsea equipment and turning that element to generate electric power on board the equipment. Subsea equipment that implements the method comprises: an on-board electric power generator connected to an electrical load such as a rechargeable battery to charge the battery when the generator is driven; and a rotary coupling element that is turned by an external drive to drive the generator. Alternative subsea equipment to implement the method comprises: a stator, but not a rotor, of an on-board electric power generator, which supplies current to the load when an externally-driven rotor is positioned adjacent to the stator and turned relative to the stator. A power source having a generator rotor is docked with the equipment for this purpose.

Abstract: A method of hosting an autonomous underwater vehicle (“AUV”) at a subsea location lowers at least one AUV basket to a subsea location adjacent at least one preinstalled subsea structure. The subsea structure has provision for electrical power to be provided to it. At the subsea location, the, or each, basket is connected to the, or each, subsea structure to receive electrical power from the subsea structure. Electrical power routed via the subsea structure may be used to charge batteries of an AUV docked with the basket. Provision may also be made to effect data communications with the AUV with data being communicated between the subsea structure and the basket.

Abstract: A mudmat for a subsea pipeline accessory has a body with an accessory support structure arranged to lie underneath and support an accessory. At least one foundation element attached to the body is movable from a stowed position at least partially under the accessory support structure into a deployed position extending laterally from the accessory support structure after overboarding the accessory from a vessel and before landing the accessory on the seabed. Two or more foundation elements may be deployed simultaneously in laterally-opposed directions transverse to the longitudinal axis of a pipe that supports the accessory.

Abstract: A connector for lined pipelines includes a tube having opposed male interface elements extending inwardly from respective ends of the tube. One or more circumferential permeable chokes project radially from each male interface element. The chokes minimize flow of oxidizing fluid from the bore into the micro-annulus between the liner and the pipe while maximizing flow of fluid from the micro-annulus into the bore in the event of catastrophic pressure drop in the bore. To maintain gaps between the tube ends and the pipe liners for fluid flow, shoulder formations extend circumferentially around the tube. The connector may be used in a joint arrangement where each liner includes a body, an end of lesser thickness and greater bore than the body that terminates short of an end of the pipe, an inner step between the body and the end, and an outer step between the end and the pipe.

Abstract: A method of handling a discrete elongate subsea element of determinate length, such as a spool of rigid pipe is disclosed. The method includes shortening a tensile chord system acting on longitudinally-spaced locations on the element to apply longitudinally-compressive forces to the element. The compressive forces bend the element along its length against elastic recovery force to shorten the span of the element. One end of the element is anchored at a first anchorage before or after the element is bent. The other end of the element is anchored at a second anchorage, after the element is bent and while the element remains bent. The method is apt to be used during installation of the element, where the anchorages are both underwater, and during transportation of the element, where the anchorages are hang-off platforms of a surface vessel.

Abstract: A reelable connection between facing ends of opposed pipe-in-pipe sections in which an end wall connects inner and outer pipes of each section to seal an end of an annular space defined between those pipes is disclosed. In each section, the inner pipe protrudes beyond the end wall and the outer pipe and is joined to an inner pipe of the opposed section, leaving opposed ends of the outer pipes of those sections spaced from each other. An insert positioned between the opposed ends of the outer pipes maintains the outer pipe diameter from one section to the other section across the connection.

Abstract: A method of clamping elongate elements in a parallel piggybacked arrangement during subsea laying of the elements is disclosed. The method includes opposed reciprocating jaws which force together clamp segments around the elongate elements to assemble a piggybacking clamp. The piggybacking clamp applies clamping forces to the elongate elements.