Abstract: A communication system for transmitting electrical power and data between a first end of a transmission line and a second end of the transmission line comprises, at the first end: a DC supply means for supplying direct current to the transmission line; first switching means for switching the DC supply means; and a first modulator for operating the first switching means. At the second end, the system comprises an energy storage means for storing and supplying DC power; second switching means for switching power from the energy storage means; and a second modulator for operating the second switching means.

Abstract: A christmas tree assembly for a subsea hydrocarbon extraction facility, the christmas tree assembly includes a fluid pipeline and a sensor assembly comprising a plurality of sensors configured to monitor a plurality of properties relating to hydrocarbon fluid flow through the fluid pipeline. The sensor assembly includes a differential pressure sensor that is disposed at one or more of across a choke, around a bend or restriction in the pipeline or a dedicated flow restrictor integrated within the pipeline, and a bulk density sensor that is disposed in one or more of a blind T, before or after a choke or in an upwards section of the flow pipeline.

Abstract: A method of using an umbilical between a surface location and an underwater location of an underwater fluid extraction well system is provided. The umbilical includes an electrical power conductor configured to transmit electrical power at a first frequency from a source at the surface location to the underwater location. The method comprises detecting that the umbilical has been compromised by the ingress of water. In response thereto, the method comprises converting electrical power from the source to electrical power at a second frequency, wherein the second frequency is lower than the first frequency or DC electrical power; transmitting the electrical power at the second frequency or DC electrical power to the underwater location via the conductor; and converting, at the underwater location, the electrical power at the second frequency or DC electrical power to electrical power at a frequency used by the underwater equipment of the well system.

Abstract: A system for transmitting electrical power and communication signals is provided. The system comprises a transmission line, a source of electrical power for supplying electrical power to the transmission line, a first communication unit configured to supply communication signals to the transmission line, a power extraction unit configured to extract and use electrical power from the transmission line, a second communication unit configured to receive communication signals from the transmission line; and a control unit configured to control operation of the system. The source supplies electrical power to the transmission line for respective periods of time which are different from respective periods of time in which the first communication unit supplies communication signals to the transmission line.

Abstract: A system for transmitting alternating current power and communication signals between a first location and a second location through a communication path which includes at least one inductive load and at least one switch configured to switch power to the at least one inductive load on and off is disclosed herein. The system comprises a control configured to control the at least one switch so that, if the power is switched on during a particular phase of the power, is the power is switched off during the opposite phase of the power, and if the power is switched off during a particular phase of the power, the power is switched on during the opposite phase of the power.

Abstract: A rotor is provided. The rotor comprises external blades for use in causing rotation of the rotor, and internal blades for use in propelling a fluid through the rotor during rotation of the rotor.

Abstract: A method of energizing a coil of a solenoid of a directional control valve, wherein an armature of the solenoid moves between a first position in which the solenoid is operating and a second position in which the solenoid is not operating, the method comprising energizing the coil with a voltage, controlling the voltage, detecting a current in the coil at which the armature of the solenoid moves between the first position and the second position, and using the current at which the armature of the solenoid moves between the first position and the second position increased by a margin as an operating current for energizing the coil of the solenoid.

Abstract: A grease delivery system for delivering grease to a location is provided. The grease delivery system comprises: a first grease reservoir having a first grease output and a first output device configured to output grease from the first grease reservoir; a second grease reservoir having a second grease output and a second output device configured to output grease from the second grease reservoir; and a common grease output for delivering grease to the location, wherein the common grease output is fluidly connected to the first and second grease outputs, wherein the system is configured to simultaneously output grease from the first and second grease reservoirs to the common grease output.

Abstract: A communication arrangement for a subsea well control system, comprising an umbilical between a topside location and a subsea location, an electrical conductor in said umbilical, and a data transmission system configured to transmit and receive data between said locations via said conductor, wherein a return path for said data comprises the sea.

Abstract: A pump for use in pumping hydraulic well control fluid expelled from a control device of a well, comprises means for accumulating such hydraulic well control fluid and means for using the pressure of hydraulic fluid supplied to the well to pump accumulated hydraulic well control fluid into a production flowline of the well.

Abstract: A system for transmitting alternating current power and communication signals between a first location and a second location via a communication path which includes at least one inductive load and at least one switching means for switching power to said at least one load on and off, the system including control means adapted for controlling said at least one switching means so that, in response to switching off said power, a direct current is applied to said at least one inductive load and, in response to actuation of said at least one switching means to switch said power on, said power is switched on during a phase of the power which results in a magnetization of said at least one inductive load opposite to that resulting from said direct current.

Abstract: An apparatus for updating the software in a subsea electronics module, the apparatus including a first data transmitting and receiving means, a second data transmitting and receiving means, and a transmission line between the first and the second data transmitting and receiving means, wherein packets of data from the first data transmitting and receiving means are transmitted to the second data transmitting and receiving means and aggregated to form a local master, from which software in SEMs may be updated locally. The packets of data may be transmitted using unutilised capacity of the transmission line not required during normal operations.

Abstract: A method of applying acid-wash to a subsea connection assembly, in particular a stabplate connection, in order to remove unwanted material such as marine growth and calcareous deposits. The method consists of inserting a plug, containing channels, into a central in a stabplate connection and injecting acid-wash through the plug. The plug may be carried by an operating tool arm of a remotely operated underwater vehicle (ROV).

Abstract: A method for calculating a value representative of a downhole temperature in a hydrocarbon well, wherein the well includes production tubing inside an outer tubing, an annulus is provided between the production tubing and the outer tubing, and the annulus receives a hydraulic control line supplying hydraulic fluid for the control of a downhole device, the method including sensing the pressure of hydraulic fluid in the control line at the wellhead, and using a measurement of the pressure to calculate the value representative of the downhole temperature.

Abstract: A system for providing alternating current to at least one inductive load, the system including at least one switching means for switching power to the load on and off, controller adapted for controlling the at least one switching means and a pre-magnetization device, wherein the pre-magnetization device is configured to generate pulses which cause the switching means to pre-magnetize the inductive load.

Abstract: A method of determining the location of a fault in a cable at an underwater fluid extraction facility is provided. The method comprises: providing a time domain reflectometry unit at the facility, the unit being connected to at least one wire within the cable; causing the unit to transmit a current pulse to the wire; detecting a reflected pulse received at the unit; determining the time duration between the pulse transmission and the reflected pulse reception and using the duration to calculate a distance between the fault and the unit; and determining the location of a fault on the wire using the calculated distance.

Abstract: A hydraulic accumulator assembly in which a hydraulic accumulator is associated with at least one responsive unit, which is responsive to the weight of the accumulator to provide an indication dependent on the weight of the accumulator. The accumulator is in an underwater fluid extraction well facility.

Abstract: A high pressure intensifier system is disclosed. The system has a high pressure intensifier configured to receive hydraulic fluid from an input and provide the fluid to an output at a higher pressure than at the input, a monitor configured to monitor the pressure of hydraulic fluid provided at the output, and a control configured to control the supply of hydraulic fluid from the input, and configured to maintain the pressure of hydraulic fluid provided at the output at substantially a predetermined value.

Abstract: A method of testing a transformer prior to installation in a high-pressure environment wherein the transformer comprises a transformer core comprising a stack of a plurality laminations, is provided. The method comprises applying a mechanical compression force to the stack, the force being at least equivalent to the ambient pressure of the high-pressure environment; and testing the electrical efficiency of the transformer.

Abstract: A production control system for an underwater well, comprises: first electrically operated means for supplying first hydraulic fluid, for opening a first control valve of the well; second electrically operated means, for supplying second hydraulic fluid at a higher pressure than said first fluid, for opening a further control valve of the well; electronic circuitry (SEM1) for providing electrical power for operating said first and second means; and means for controlling the sequence of closing said control valves as a result of a loss of electrical power from said electronic circuitry. The controlling means comprises: electrical power storage means; detection means responsive to said loss of power from said electronic circuitry; and means coupled with said detection means for using electrical power from said storage means to keep said further control valve open for a period after closure of said first control valve and close it after said period.