GB2547193A

GB2547193A - An electrically-powered, subsea tool assembly

Info

Publication number: GB2547193A
Application number: GB1602268.3A
Authority: GB
Inventors: Stuart Elliot Keith; James Bolton Adam
Original assignee: Allspeeds Holdings Ltd
Current assignee: Allspeeds Holdings Ltd
Priority date: 2016-02-09
Filing date: 2016-02-09
Publication date: 2017-08-16
Also published as: GB201602268D0

Abstract

An electrically powered subsea tool assembly 1 comprising a tool 2 and a hydraulic actuator 3 for the tool. A pump 10 supplies hydraulic fluid to the actuator and is located within a sealed chamber 20 to which the tool is externally attached. A battery operated motor 19 is provided for the pump along with a pressure compensator 15 that comprises a source of hydraulic fluid for the pump. The pressure compensator equalizes the pressure at a hydraulic input 17 of the pump with the external subsea pressure. The tool may reset automatically after actuation by a spring. The actuator may include a hydraulic piston, which the pressure compensator is connected to either side of. A valve 16 on the driven side may be closed during actuation of the tool and opened when the tool is resetting.

Description

AN ELECTRICALLY POWERED, SUBSEA TOOL ASSEMBLY

The present invention relates to an electrically powered, subsea tool assembly, such as a cutting tool assembly.

Subsea powered tools are designed for gripping, lifting and cutting lines such as submarine wire ropes, armoured telecommunication and power cables, and hoses. Conventionally, such tools are attached to an arm of the remotely operated vehicle (ROV) and are hydraulically powered. This means that a hydraulic hose must be connected between the tool and the vehicle. However, some ROVs, such as light-weight inspection ROVs, cannot carry much weight and conventional, hydraulically powered tools are too heavy for use by such vehicles. In addition, ROVs of this type are unable to supply the power required to generate the hydraulic pressures required for the operation of such tools.

An object of the present invention is to provide a subsea tool assembly that overcomes or substantially mitigates the aforementioned disadvantages

According to the present invention there is provided an electrically powered, subsea tool assembly comprising a tool, an hydraulic actuator for the tool; a pump that is adapted to supply hydraulic fluid to the actuator and that is located within a sealed chamber to which the tool is externally attached; a battery operated motor for the pump; and a pressure compensator that comprises a source of hydraulic fluid for the pump and that is adapted to detect the pressure of an external subsea environment and to equalize the hydraulic pressure at an hydraulic input of the pump with the pressure of said external subsea environment.

Preferably, the tool is adapted to reset automatically after actuation.

Preferably also, the hydraulic actuator comprises a hydraulic cylinder containing a piston and a piston rod attached to a movable element of the tool. Advantageously, the pressure compensator is preferably also connected to a return side of the piston and equalizes the hydraulic pressure at the hydraulic input of the pump and the return side of the piston with the pressure of said external subsea environment.

Preferably also, the sealed chamber contains the pump and the motor and is filled with a non-electrically conducting fluid, which is preferably a low viscosity silicone oil.

Preferably also, the tool is a cutting tool.

Other preferred but non-essential features of the present invention are described in the dependent claims appended hereto.

The present invention will now be described by way of example with reference to the accompanying drawings in which;-

Fig. l is a schematic longitudinal cross-sectional of an electrically powered, subsea tool assembly in accordance with the present invention, the tool of the assembly being a cutter;

Fig. 2 is a view to an enlarged scale of the cutter forming part of the tool assembly shown in Fig. 1, the cutter having a guillotine blade that is shown in a retracted position;

Fig. 3 is a view similar to that of Fig. 2 but with the guillotine blade shown in a cutting position.

The embodiment of electrically operated, subsea tool assembly shown in the drawings comprises a cutter that is typically employed for cutting through steel or fibrous anchoring cables, ropes and the like. Such cables may be between 15 mm and 25 mm in diameter and in order for these to be severed, an electrically-powered guillotine cutter typically requires in excess of 1500 watts. A light-weight ROV is not capable of supplying this quantity of electrical power. Hence, to overcome this problem in accordance with the present invention the tool assembly comprises a hydraulic actuator that is supplied with hydraulic fluid by a pump driven by a battery operated motor. Such an arrangement is capable of generating the required power for the cutter and will now be described in detail. However, it will be appreciated that other forms of tool with a movable element such as a gripping or lifting tool may be substituted for the cutter as appropriate in other circumstances. In all cases, it will be appreciated that in practice the various components of the assembly are interconnected to form an integrated assembly capable of being externally attached to an ROV whereas the drawings illustrate the components of the tool assembly schematically without any interconnecting framework or connecting structures being shown.

As indicated above, the electrically operated subsea tool assembly 1 shown in the drawings comprises a cutter 2 that is driven by a hydraulic actuator 3, which is connected directly to it. The actuator 3 comprises a hydraulic cylinder housing a piston 4 and is attached to directly to the body of the cutter 2, preferably by screwing. The piston 4 is connected to a piston rod 5 that projects from an end of the actuator 3 and that is connected directly to a guillotine blade 6 of the cutter 2. As the piston rod 5 is reciprocated into and out of the actuator 3, the blade 6 is either retracted or driven down guide channels 7 in the body of the cutter 2, through a cutting aperture 8 to impact on an anvil 9. The blade 6 thereby severs any item such as a cable or rope located in the cutting aperture 8. In embodiments of assemblies in accordance with the invention that do not comprise guillotine cutters, the piston rod 5 would be connected to a movable element of the tool, for example a jaw, reciprocating saw or scissor blade.

The actuator 3 is supplied with hydraulic fluid by a pump 10 via a pipe 11 connected to a first hydraulic fluid inlet/outlet port 12 on a driven side of the piston 4. A second hydraulic fluid inlet/outlet port 13 is provided on a return side of the piston 4 and is connected to pipework 14 that links it to a reservoir of hydraulic fluid in the form of an hydraulic compensator 15, which is adapted to detect the pressure of an external subsea environment. The pipework 14 is also linked to the pipe 11 via a valve 16 and to an hydraulic input 17 of the pump 10 to supply the latter with hydraulic fluid. The hydraulic pressure at the input 17 of the pump 10 and the return side of the piston 4 is thereby equalized. The actuator 3 is arranged so that when the piston 4 is supplied with fluid by the pump 10 it drives the piston rod 5 out of the actuator 3 to move the blade 6 in a cutting stroke. However, the blade 6 is retracted and the piston 4 is automatically reset by means of a spring 18 that acts on the piston rod 5. This may be a tension spring 18 located within the piston rod 5, as shown in Fig. 1, but could be a coil spring located around the piston rod 5 in other embodiments. On reset, the flow of hydraulic fluid out of the actuator 3 via the port 12 is controlled by the valve 16, which is normally closed but opened at the completion of each cutting stroke to permit hydraulic fluid to return to the pipework 14 and the compensator 15 as it is forced out of the port 12 of the actuator 3 by the resetting piston 4.

The pump 10 is powered by a motor 19, which together with the pump 10, is located within a sealed chamber 20 to which the cutter 2 is externally attached. The sealed chamber 20 is preferably filled with a non-electrically conducting fluid, advantageously a low viscosity silicone oil. In addition, it is provided with a compensator hose 21, that is sealed at its free end but is in communication with the interior of the chamber 20 whereby the pressure within the chamber 20 is equalized with that of the external subsea environment by compression of the hose 21 by the external subsea environment when the tool assembly 1 is in use, as is described in more detail below.

In turn, the motor 19 is powered by a battery 22 via a speed controller 23, both of which are housed in a separate hermetically sealed casing 24 to ensure no ingress of seawater or other contaminants during use. The speed controller 23 is linked by a sealed electric cable 25 to the motor 19. The casing 24 may itself be connected directly to the housing 20 or to a framework (not shown) to which the other components of the assembly 1 are attached. Operation of the motor 19 is switched on or off via the speed controller 23 under the ultimate control of the operator of the ROV to which the assembly 1 is attached.

In use, the assembly 1 is mounted on an ROV for use in a subsea environment. When the assembly is in a stand-by condition prior to operation of the cutter 1 the blade 6 is retracted as shown in Figs. 1 and 2 and the valve 16 is closed. As the assembly 1 descends in the sea, the pressure compensator 15 detects the pressure of the subsea environment and automatically equalizes the hydraulic pressure at the hydraulic input 17 of the pump 10 with the ambient pressure via the pipework 14. This means that when the pump 10 is actuated, it only has to generate sufficient hydraulic pressure to operate the cutter 1 and does not have to overcome any counteracting pressure in the cutter 1 caused by the ambient pressure of the external environment. Advantageously, the hydraulic pressure on the return side of the piston 4 is also equalized with that at the pump input 17 and the external subsea environment. Similarly, the compressible compensator hose 21 also ensures that the pressure within the housing 20 is similar to that of the external environment too.

When the motor 4 is switched on via the speed controller 23, it drives the pump 10, which in turn pumps hydraulic fluid from the compensator 15 into the actuator 3 down the pipe 11. The piston 4 thereby acts to drive the piston rod 5 out of the actuator 3 and move the blade 6 in a cutting stroke towards the anvil 9. Any item located within the cutting aperture 8 is thereby severed. During the cutting stroke, the hydraulic fluid on the return side of the piston 4 is forced out of the actuator 3 via the port 13 into the pipework 14- Once the cutting stroke of the blade 6 has been completed, the motor 4 is switched off and the valve 16 is opened. This enables the spring 18 to retract the piston rod 5 back into the actuator 3, the hydraulic fluid on the drive side of the piston 4 being forced out of the actuator 3 via the port 12 and the open valve back into the pipework 14. Once the return stroke is completed the valve 16 is closed. The movement and pressure of the hydraulic fluid during the cutting and return strokes of the cutter 2 is thereby regulated by the compensator 15.

In some embodiments, the hydraulic fluid supplied by the compensator 15 may be the same as the non-electrically conducting, low viscosity silicone oil used to fill the housing 20. This has the advantage of reducing the weight of the assembly 1.

Hence, the electrically powered subsea tool assembly 1 of the invention is one that is capable of being carried and operated by a lightweight ROV. It has the advantage of being depth independent, as it automatically compensates for the external subsea pressure and as it generates the power required to operate the tool itself, does not require power from the ROV to operate other than an on/off signal.

Claims

1. An electrically-powered, subsea tool assembly comprising a tool, an hydraulic actuator for the tool; a pump that is adapted to supply hydraulic fluid to the actuator and that is located within a sealed chamber to which the tool is externally attached; a battery operated motor for the pump; and a pressure compensator that comprises a source of hydraulic fluid for the pump and that is adapted to detect the pressure of an external subsea environment and to equalize the hydraulic pressure at an hydraulic input of the pump with the pressure of said external subsea environment.

2. An assembly as claimed in Claim 1, wherein the tool is adapted to reset automatically after actuation.

3. An assembly as claimed in Claim 1 or Claim 2, wherein the hydraulic actuator comprises a hydraulic cylinder containing a piston and a piston rod attached to a movable element of the tool.

4. An assembly as claimed in Claim 3 when dependent on Claim 2, wherein the tool is reset by means of a spring that acts on the piston rod.

5. An assembly as claimed in Claim 3 or Claim 4, wherein the pressure compensator is also connected to the hydraulic cylinder on a return side of the piston and equalizes the hydraulic pressure at the hydraulic input of the pump and the return side of the piston with said external subsea environment.

6. An assembly as claimed in Claim 5, wherein the hydraulic cylinder on a driven side of the piston is connected to the pressure compensator via a valve that is closed during actuation of the tool and opened after actuation of the tool to permit hydraulic fluid within the hydraulic cylinder to return to the pressure compensator as the tool resets.

7. An assembly as claimed in any of Claims 1 to 6, wherein the sealed chamber contains the pump and the motor and is filled with a non-electrically conducting fluid.

8. An assembly as claimed in Claim 7, wherein the non-electrically conducting fluid is a low viscosity silicone oil.

9. An assembly as claimed in any of Claims 1 to 8, wherein the sealed chamber is provided with a compressible compensator hose whereby the pressure within the sealed chamber is equalized with that of the external subsea environment by compression of the hose.

10. An assembly as claimed in any of Claims 1 to 9, wherein the battery is located in an hermetically sealed container.

11. An assembly as claimed in Claim 10, wherein the battery is connected to the motor via a speed controller that is also located within the hermetically sealed container.

12. An assembly as claimed in any of Claims 1 to 11, wherein the tool is a cutting tool.

13. An assembly as claimed in Claim 12 when dependent on Claim 3, wherein the tool comprises a cutter with a guillotine blade that is connected to the piston rod.

14- An electrically-powered, subsea tool assembly substantially as described herein with reference to the accompanying drawings.