NO20170520A1

NO20170520A1 - Node retrieval system

Info

Publication number: NO20170520A1
Application number: NO20170520A
Authority: NO
Inventors: Guillaume Peigne
Original assignee: Rolls Royce Marine As
Priority date: 2017-03-29
Filing date: 2017-03-29
Publication date: 2018-10-01
Also published as: NO343311B1

Abstract

Node retrieval system on a vessel for removing nodes (15) from a carrier line (13) in marine operations, comprising a detachment unit (210) equipped with at least a grabbing mechanism for receipt and centralizing of a node (15) connected to the carrier line (13), and a release mechanism to open a cable clamp (100) on the node (15), for releasing the node (15) from the carrier line (13).Node retrieval system on a vessel for removing nodes (15) from a carrier line (13) in marine operations, comprising a detachment unit (210) equipped with at least a grabbing mechanism for receiving and centralizing a node (15) connected to the carrier line (13), and a release mechanism to open a cable clamp (100) on the node (15) for releasing the node (15) from the carrier line (13).

Description

Node retrieval system

Field of the invention

The present invention relates to a node retrieval system on a vessel for removing nodes from a carrier line in marine operations. The invention also relates to a method on a vessel for node retrieval.

Background of the invention.

Various technologies for seismic acquisition exist. Examples of existing technologies are surface seismic, where seismic streamer cables are towed (close to surface) behind a vessel, and ocean bottom seismic where the cables with nodes are positioned on the seabed. The present invention was originally conceived for use in ocean bottom seismic operations, but may be applied to other seismic operations as well.

When retrieving the carrier line with the nodes from the sea, the nodes can be detached from the carrier line using an automatic node retrieval system according to the invention. With the node retrieval system, no damping is required for detaching the nodes from the carrier line. Only the clamp is in contact with the stern sheave, which reduces the tension on the node and clamp. The guiding and unlocking device is combined in one unit, which makes the automated retrieval and unlocking process simple and robust. There is no need for sensors for detecting the nodes on the carrier line. The carrier line will be retrieved at constant speed, and the nodes will be automatically detached as they pass through the guiding mechanism. The retrieval system is therefore simple and robust, and can easily be adjusted to higher/lower speed without requiring more space or sensors, or exposing the nodes and clamps to damage.

The invention allows for high speed retrieval of ocean bottom seismic nodes. A node clamp can be used in automatic node deployment and retrieval systems. Active or passive damping may be applied to compensate for the vessel’s motions by using for instance a stern sheave. In the prior art, the speed of attaching the nodes to the cable or removing the nodes from the cable, and deploying/retrieving the cable is in practice limited due to increased strain/wear of the accelerated nodes, and due to space limitations. With the automatic node retrieval system according to the invention, the speed may easily be increased, by simply increasing the diameter of the retrieval wheels. Also, the design of these wheels offers redundancy to the process. Another feature is that only the clamp is in contact with the stern sheave. This solution is therefore gentler to the nodes and the clamps than previous solutions.

There are some prior art documents regarding node clamping, but very few describing automated node handling. Other prior art documents describe manual attachment or removal of the nodes to or from the carrier line. In automated node handling, there are various ways of attaching or removing the node to or from the carrier line. The most common solution is to attach or remove the nodes to or from the carrier line from the side.

A clamping mechanism is designed to be used on-board a marine vessel to attach a plurality of sensors along the carrier line. The nodes are clamped on to the carrier line at the same speed as the carrier line is deployed into the water. I.e. there is no relative speed difference between node and carrier line at the time of attachment/clamping. Because of the unique locking mechanism, the clamping process is gentler to the nodes, and the nodes are therefore less exposed to damage both during attachment, deployment, retrieval and detachment. One of the differences as compared to existing clamping mechanisms is that the cable clamp is not secured to the cable by applying tension from the cable. The clamping mechanism is independent of the cable tension; the nodes can be effectively mounted on the cable or removed from the cable, both with and without cable tension. The strength and durability of the clamping mechanism is enhanced through the compact size, rugged design and use of corrosion resistant materials.

Disclosure of the state of art.

WO2016163891 A1 discloses a node handling device for use during deployment or retrieval of a plurality of seismic nodes attached to a cable, the node handling device comprising: a wheel device adapted for damping of the cable with attached seismic nodes during deployment or retrieval. A wheel device and a method for deployment or retrieval are also disclosed. The wheel device is adapted for damping the cable and attached seismic nodes during deployment or retrieval by having a contact surface, wherein the damping material of the contact surface enables a soft and safe reception of the nodes when the nodes arrive at the wheel and are passing over the wheel.

WO2016130019 A1 relates to an attachment device for attaching a seismic node to a cable, the attachment device comprising an in-line fastening device fastening the cable; and at least one locking device securing the cable in the at least one in-line fastening device. The locking device prevents the cable from escaping the fastening device. A seismic node and a method for deployment and retrieval of a number of seismic nodes are also described. The attachment device thus relies on the tension on the cable for securing the node to the cable.

US2015301212 A1 discloses an apparatus and methods for loading and unloading of sensor capsules into or out of seismic node casings forming part of a seismic cable to be deployed or retrieved by a vessel, the apparatus comprises: a trolley with room for at least one sensor capsule, the trolley is moveable back and forth in a direction essentially corresponding to the longitudinal direction of the seismic cable; a support structure for the trolley a latching mechanism for latching the trolley to a node casing, and at least one inserting/withdrawing mechanism for inserting and withdrawing the sensor capsules into or out of the node casing.

US5624207 A discloses a marine seismic cable deployment and retrieval system for utilization in conjunction with a marine vessel. It teaches a large wheel mounted in the front of the vessel for retrieving seismic cable from the water, and a horizontally mounted cable handler comprising an eight wheel cable puller for pulling the cable, the cable puller comprising four pairs of tires in frictional, rotational contact with one another along their outer surfaces, configured to frictionally grab and pull a seismic cable along a linear path.

US2013189036 A1 disclose a direction changing support structure to eliminate the risk of damaging an elongate flexible element and/or an accessory integrated therein, such as a seismic cable having sensor modules distributed rather densely along the cable and forming therewith sections that risk being damaged, on passing from a generally horizontal/vertical orientation to a generally vertical/horizontal one during subsea laying or retrieving of the cable. The support structure comprises at least two rotary sheaves and a rotary support frame for carrying the sheaves, and said at least two sheaves are spaced from each other a distance that is greater than a length of the accessory to permit the element with the integral accessory to extend in a straight line between the two sheaves. Each sheave has a rotational axis that is parallel to a rotational axis of the support frame, and the support frame is rotary at least between a position in which the accessory with associated ends of the element is located in a generally horizontal orientation and is supported by said sheaves and a position in which the accessory with associated ends of the element is located in a generally vertical orientation during continuous support by said sheaves.

Objects of the present invention

It is an object to provide an automatic deployment system for high speed retrieval of (autonomous) seismic nodes, including detachment of (autonomous) seismic nodes from carrier lines (cable/rope/wire) in marine (ocean bottom seismic) operations

Further object of the present invention is prevention of loss of the nodes, increase of the system reliability, prolongation of the system lifetime, saving of costs on repair and interrupted operation.

The invention enables manual, ‘semi’-automated and fully automated node deployment operations. It is flexible; variable node spacing, not dependent on detection of actual node position and/or carrier line speed. No/minimal acceleration/deceleration of the carrier line is required.

Summary of the invention

At least some of the objects are achieved with a node retrieval system and a method according to the present invention, as defined in the independent claims.

Alternative embodiments are given in the dependent claims.

Description of the diagrams

Embodiments of the present invention will now be described, by way of example only, with reference to the following diagrams wherein:

Figure 1 shows a node retrieval system according to the invention.

Figure 2 shows the node retrieval system according to the invention, and deployment unit.

Figure 3 shows in more detail a node retrieval system according to the invention.

Figures 4a-4c shows movement of a node past a grabbing mechanism for and a release mechanism in the node retrieval system according to the invention.

Figure 5 shows in cross section a grabbing mechanism for and a release mechanism in the node retrieval system according to the invention.

Figure 6 shows a node with a cable clamp to be used in the node retrieval system according to the invention.

Figure 7 show in more detail the cable clamp of figure 6.

Description of preferred embodiments of the invention

As seen in figure 1 and 2, a carrier line 13 with nodes 15 is by a winch (not shown) pulled from the ocean and past a stern sheave 11, to a detachment unit 210 in where the nodes 15 are removed from the carrier line13 and then past a wire sheave 16 to a drum (not shown). Nodes 15 that are detached from the carrier line 13 are transported to a storage by a conveyer 214.

The detachment unit 210 is equipped with at least a grabbing mechanism for receipt and centralizing of a node 15 connected to the carrier line 13, and a release mechanism to open a cable clamp 100 on the node 15, for releasing the node 15 from the carrier line 13.

In one embodiment comprises the grabbing mechanism for receipt and centralizing of the nodes 15 connected to the carrier line 13 two counter rotating grabbing wheels 222 equipped with resilient contact surfaces, wherein the node 15 is received between the resilient contact surfaces of the two counter rotating wheels 222. The resilient contact surfaces of the rotating wheels 222 can be made of a plurality of radially extending spring-loaded fingers 223. The release mechanism to open the cable clamp 100 on the node 15 can comprise two counter rotating release wheels 221 adapted to apply an opening force on the cable clamp 100 on the node 15.

Preferably are the two counter rotating release wheels 221 placed above the two counter rotating grabbing wheels 222.

As shown in figures 4a-4c, the node 15 (still attached to the carrier line 13) is received on the conveyer 214 and then grabbed between the radially extending spring-loaded fingers 223 on the counter rotating grabbing wheels 222 of the grabbing mechanism. Due to the resilient nature of the spring-loaded fingers 223 the node 15 will be centralized and pushed along the conveyer 214 until it encounters the two counter rotating realise wheels 221 of the release mechanism, and the node 15 is detached.

In another embodiment (not shown) is the grabbing mechanism for receipt and centralizing of the node 15 connected to the carrier line 13 a dual belt drive/conveyer for grabbing and pushing the node 15 past the release mechanism to open the cable clamp 100 on the node 15. The release mechanism can be a static mechanical unit which applies a compression force on a compression tab 116 in the cable clamp 100 to free the carrier line 13 from a clamped state in the cable clamp 100. The static mechanical unit can for instance be of a wedge shaped geometry, which the cable clamp 100 on the node 15 is forced past by the grabbing mechanism.

As shown in figure 7 the cable clamp 100 on the node 15 can comprise a clamp body 110 with a spring-loaded clamp arm 111, wherein the carrier line 13 is received in a slot in the clamp body 110, and clamped by the spring-loaded clamp arm 111. The cable clamp also can comprise a compression tab 116 for releasing a spring 115 holding the spring-loaded clamp arm 111 in the clamped state.

The cable clamp may further comprise a wire guard 114 which is activated by the spring-loaded clamp arm 111, to further secure the carrier line 13 in the open slot in the clamp body 110.

The cable clamp can also comprise a release lever 112 for releasing the springloaded clamp arm 111 to a clamping state during deployment and attachment of the nodes 15 to the carrier line 13, when for instance used in the deployment unit shown in figure 2.

The release mechanism, either it is one of the two counter rotating release wheels 221 or the static mechanical unit, is adapted to apply a compression force on the compression tab 116 for releasing the cable clamp 100 from the carrier line 13.

The detachment unit 210 is preferably mounted on or above the conveyer 214.

The stern sheave 11 can be mounted upstream of the detachment unit 210 for providing active or passive damping on the carrier line 13 to compensate for vessel motion.

The method on a vessel for node retrieval and detachment of nodes 15 from a carrier line 13 in marine operations thus comprises guiding of the carrier line 13 with the nodes 15 inboard to a conveyer 214, receipt and centralizing of a node 15 connected to the carrier line 13 on the conveyer 214, applying a release mechanism to open a cable clamp 100 on the node 15, for releasing the node 15 from the carrier line 13, and conveying the nodes 15 to a storage.

The node retrieval system according to the invention can be combined with a node deployment system, as briefly shown in figure 2. In the node deployment system nodes 15 are transported from a storage to the deployment unit 10 equipped with at least one rotary transfer unit. Rotation speed of the rotary transfer unit is synchronized to rotation speed of a rotary carrier line unit, for transfer of a node 15 to the rotary carrier line unit, followed by operation of an activating mechanism for clamping of the node to the carrier line 13. The carrier line 13 with the attached nodes 15 are thereafter guided overboard from the vessel.

Claims

1. Node retrieval system on a vessel for removing nodes (15) from a carrier line (13) in marine operations, comprising:

a detachment unit (210) equipped with at least a grabbing mechanism for receipt and centralizing of a node (15) connected to the carrier line (13), and a release mechanism to open a cable clamp (100) on the node (15), for releasing the node (15) from the carrier line (13).

2. Node retrieval system according to claim 1, further comprising a conveyer (214) for transporting the released nodes (15) to a storage.

3. Node retrieval system according to claim 1, wherein the grabbing mechanism for receipt and centralizing of the nodes (15) connected to the carrier line (13) comprises two counter rotating grabbing wheels (222) equipped with resilient contact surfaces, wherein the node (15) is received between the resilient contact surfaces of the two counter rotating wheels (222).

4. Node retrieval system according to claim 3, wherein the resilient contact surfaces of the rotating wheels (222) are made of a plurality of radially extending spring-loaded fingers (223).

5. Node retrieval system according to claim 1, wherein the release mechanism to open the cable clamp (100) on the node (15) comprises two counter rotating release wheels (221) adapted to apply an opening force on the cable clamp (100) on the node (15).

6. Node retrieval system according to claim 3 and 5, wherein the two counter rotating release wheels (221) are placed above the two counter rotating grabbing wheels (222).

7. Node retrieval system according to claim 2, wherein the detachment unit (210) is mounted on or above the conveyer (214).

8. Node retrieval system according to claim 1, wherein the cable clamp (100) comprises:

a clamp body (110) with a spring-loaded clamp arm (111), wherein the carrier line (13) is received in a slot in the clamp body (110), and clamped by the springloaded clamp arm (111), and

a compression tab (116) for releasing a spring (115) holding the spring-loaded clamp arm (111) in the clamped state.

9. Node retrieval system according to claim 5 and 8, wherein at least one of the two counter rotating release wheels (221) is adapted to apply a compression force on the compression tab (116) for releasing the cable clamp (100) from the carrier line (13).

10. Node retrieval system according to claim 1, wherein the grabbing mechanism for receipt and centralizing of the node (15) connected to the carrier line (13 is a dual belt drive/conveyer for grabbing and pushing the node (15) past the release mechanism to open the cable clamp (100) on the node (15).

11. Node retrieval system according to claim 1 and 8, wherein the release mechanism is a static mechanical unit which applies a compression force on the compression tab (116) in the cable clamp (100) to free the carrier line (13) from the clamped state.

12. Node retrieval system according to claim 11, wherein the static mechanical unit has a wedge shaped geometry, which the cable clamp (100) on the node (15) is forced past by the grabbing mechanism.

13. Node retrieval system according to claim 1, comprising a stern sheave (11) mounted upstream of the detachment unit (210) for providing active or passive damping on the carrier line (13) to compensate for vessel motion.

14. Method on a vessel for node retrieval and detachment of nodes (15) from a carrier line (13) in marine operations, comprising:

- guiding of the carrier line (13) with the nodes (15) inboard to a conveyer (214),

- receipt and centralizing of a node (15) connected to the carrier line (13) on the conveyer (214),

- applying a release mechanism (221) to open a cable clamp (100) on the node (15), for releasing the node (15) from the carrier line (13), and

- conveying the nodes (15) to a storage.