Abstract: A method of launching an elongate subsea structure such as a pipeline bundle unit into water provides buoyant support to the structure by displacing water with a hollow buoyancy unit that applies buoyant upthrust to the structure. By lowering the buoyancy unit in the water to bring a permanently open aperture of the buoyancy unit beneath a surface level of the water, the buoyancy unit is flooded with water through the or each permanently open aperture to reduce the buoyant upthrust applied to the structure. A corresponding elongate subsea structure is also claimed.

Abstract: A bundle section of a subsea pipeline bundle has a rigid carrier pipe having an end closed by a transverse bulkhead and one or more fluid conduits in fluid communication with an opening that penetrates the bulkhead. Fluid coupling formations such as a spigot or a recess on an outer face of the bulkhead surround the opening. Leak-tight coupling between successive fluid conduits is effected when the bulkheads of two such bundle sections are brought together. This forces together opposed complementary fluid coupling formations of the bulkheads. The bulkheads connect the adjoining bundle sections fluidly and mechanically.

Abstract: A liner bridge for a lined pipeline has bores extending through a tubular wall and terminals fitted in the bores, each terminal being exposed to an inward side of the wall for conducting electricity to an electrofusion element. A sealing interface between each terminal and its surrounding bore has one or more projecting formations of the terminal and at least one complementary formation of the bore engaged with the or each of the projecting formations. The interface can also include a sealing mass in the bore.

Abstract: A subsea riser is installed by lowering at least one riser conduit to the seabed when piggybacked to an elongate support that comprises at least one flowline. The elongate support may be a pipeline bundle, which may be attached to one or more towheads in a towable bundle unit. The riser conduit may be in fluid communication with the flowline. At the seabed, a free end portion of the riser conduit is detached from the elongate support by releasing subsea-releasable fastenings. Then, with the elongate support and a root end of the riser remaining at the seabed, the detached free end portion of the riser conduit is lifted away from the elongate support to a riser support, such as a platform, an FPSO (floating production, storage and offloading vessel), or a buoy.

Abstract: A subsea garage for an unmanned underwater vehicle (UUV) has a body having a receptacle for the UUV, an open top providing a transit path for the UUV into and out of the receptacle and a base opposed to the open top, the base being arranged to lie on the seabed. At least one post is movable, subsea, relative to the body into a deployed position extending upwardly from the body above the open top. A lid may also be movable relative to the body between a closed position that closes the open top and an open position that allows the UUV to move along the transit path through the open top. A fixed post may extend upwardly from the body above the open top, in which case the lid may enclose the post when in the closed position and expose the post when in the open position.

Abstract: A subsea assistance system for supporting saturation diver operations includes an unmanned underwater vehicle (UUV) such as an observation remotely operated underwater vehicle (ROV) that can be flown to a subsea worksite, and various items of ancillary electrical equipment that are connected or subsea-connectable to the UUV or to a skid forming part of the UUV. Those items can include any of: a hand-portable subsea display that displays an image to a diver communicated from the UUV, which image can be generated or enhanced underwater and/or by surface support; a subsea camera that captures subsea image data for communication to the UUV and from the UUV to surface support; and a selection of electrical power tools for performing subsea tasks. Fast-acting protective devices protect divers when using high-voltage wet-mateable subsea connectors on the UUV.

Abstract: A pig has a body of resiliently compressible material extending along a central longitudinal axis. At least one strain gauge is embedded in the material of the body. The or each strain gauge extends transversely with respect to the central longitudinal axis and is arranged to deflect and elongate longitudinally with longitudinal deflection of a forward end of the body.

Abstract: A task such as inspection is performed at a subsea location by positioning a functional unit such as an unmanned underwater vehicle to perform the task. When positioned to perform the task, the unit is then in a shadow region where wireless control signals from a subsea control transmitter are obscured by a subsea obstacle. Consequently, control signals are transmitted wirelessly through water from the control transmitter to an autonomous underwater vehicle (AUV) positioned outside the shadow region and are relayed from the AUV to the unit to control the unit to perform the task. The unit can be tethered to the AUV or can communicate with the AUV wirelessly. The AUV can move itself to improve wireless communication with the subsea control transmitter and optionally also with the unit.

Abstract: A carriage arranged to walk along an elongate member while carrying a payload includes individually-operable clamps that are spaced axially along a common longitudinal axis. An axially-extensible frame connects the clamps. At least one of the clamps is attached to the frame via a rotationally-displaceable coupling for relative angular movement between that clamp and the frame about the longitudinal axis. The carriage can carry the payload to a subsea worksite by opening and closing the clamps to release and grip the elongate member in a sequence that includes moving the leading clamp forward when the leading clamp is open and moving the trailing clamp forward when the leading clamp is closed. At the worksite, installation force can be applied to the payload in a forward direction by moving the leading clamp forward when the leading clamp is open and the trailing clamp is closed.

Abstract: A system for 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 mould cavity around the field joint to effect thermal expansion of the thermoplastics material. Thermal expansion of the body in the mould 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 mould residence time including in-mould heating and cooling phases.

Abstract: An auxiliary control system, having a method for controlling same, controls subsea equipment such as a tree or manifold, for example, in the event of failure of a control umbilical. A power unit is installed subsea, and then a control tool is coupled to the subsea equipment. Control signals from topside source are transmitted to the power unit, which powers and controls the control tool in response to the control signals to operate a control element of the subsea equipment, such as a valve.

Abstract: A task such as inspection is performed at a subsea location by positioning a functional unit such as an unmanned underwater vehicle to perform the task. When positioned to perform the task, the unit is then in a shadow region where wireless control signals from a subsea control transmitter are obscured by a subsea obstacle. Consequently, control signals arre transmitted wirelessly through water from the control transmitter to an autonomous underwater vehicle (AUV) positioned outside the shadow region and are relayed from the AUV to the unit to control the unit to perform the task. The unit can be tethered to the AUV or can communicate with the AUV wirelessly. The AUV can move itself to improve wireless communication with the subsea control transmitter and optionally also with the unit.

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 method for connecting sections of a multi-bore structure in water comprises connecting the sections to bring corresponding bores of the sections into mutual alignment while those bores are each closed by a plug that excludes the water from the bores. Then, with the sections connected and the corresponding bores sealed together in fluid communication with each other, the plugs are flushed away in a flushing fluid that flows along the communicating bores.

Abstract: A method of performing remote subsea inspection includes processing mission data from a UUV at an offshore location to produce a low-resolution output and a high-resolution output, automatically and in real time. The high-resolution output is stored at the offshore location while the low-resolution output is transmitted wirelessly across a low-bandwidth communication also automatically and in real time, to be reviewed by subject-matter experts at one or more onshore or inshore locations. Selected portions of the high-resolution output can be transmitted across the communication link to the subject-matter experts on demand. Data outputs can be transmitted across the communication link at a resolution adjusted automatically in accordance with the bandwidth measured to be available on that link.

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 minimise flow of oxidising fluid from the bore into the micro-annulus between the liner and the pipe while maximising 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: An insulating insert is positioned around a field joint of a pipeline to insulate the field joint. The insert includes a longitudinal series of annular or part-annular filler segments of insulating material, curved about a longitudinal axis, that are each joined to one or more adjacent segments of the series by at least one link. The links may be webs, rods or articulated links. The links are flexible relative to the segments to facilitate bending of the insert along its length by enabling relative angular displacement between adjacent segments of the series.

Abstract: A wrap tape cassette for a subsea pipeline repair or coating machine includes a drum for carrying a wrap tape wound on the drum. A housing defines an exit opening for the wrap tape to be dispensed from the drum onto a pipeline during a repair or coating operation. The drum may be mounted to the housing for rotational and longitudinal movement relative to the housing to dispense the wrap tape through the exit opening on being unwound from the drum. A leading end of the wrap tape may be attached to an anchor element that is arranged as a closure for the exit opening and, when moved from the exit opening, for attachment to a pipeline being repaired or coated.

Abstract: A carriage arranged to walk along an elongate member while carrying a payload includes individually-operable clamps that are spaced axially along a common longitudinal axis. An axially-extensible frame connects the clamps. At least one of the clamps is attached to the frame via a rotationally-displaceable coupling for relative angular movement between that clamp and the frame about the longitudinal axis. The carriage can carry the payload to a subsea worksite by opening and closing the clamps to release and grip the elongate member in a sequence that includes moving the leading clamp forward when the leading clamp is open and moving the trailing clamp forward when the leading clamp is closed. At the worksite, installation force can be applied to the payload in a forward direction by moving the leading clamp forward when the leading clamp is open and the trailing clamp is closed.

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.