GB2547418A

GB2547418A - Friction grip lay system

Info

Publication number: GB2547418A
Application number: GB1602556.1A
Authority: GB
Inventors: Philp Barry
Original assignee: Individual
Current assignee: Individual
Priority date: 2016-02-12
Filing date: 2016-02-12
Publication date: 2017-08-23
Also published as: GB201602556D0

Abstract

A system suitable for the installation and recovery of flexibles, umbilicals and cables from a seagoing installation vessel 28 comprising a frame 3, 24, 26 orientated in the vertical, inclined or horizontal axis, friction clamps 1, 2 and associated frames 11, 12 mounted within the tower, and cylinders 8, 10 or winches used along with a control wire 32 to raise or lower each clamps through a defined envelope. The friction clamps are preferably manual of hydraulic operated and will grip the product radially wherein each clamp will preferably resist the whole product axial catenary load. The system will preferably have an abandonment and recovery system that incorporates a pivot mechanism to retract the A and R wire from the product trajectory when not in use.

Description

Friction Grip Lay System and Method

This invention relates to a process for the deployment and recovery of flexibles, umbilicals and cables as part of an offshore construction and decommissioning work scope.

From prior art, flexible, umbilical and cable lay systems are known for deploying and recovering flexible, umbilical and cable product to and from the seabed or subsea infrastructure. They are generally denoted by their orientation i.e. horizontal, inclined or vertical lay systems and are used to orientate the product departure angle from an installation vessel to the seabed as well as hold the product catenary weight and pay-in / pay-out product in a controlled manor.

These systems commonly include the following, a storage mechanism on board the installation vessel for the product, generally either a reel or carousel; deck deflector(s) to orientate the product into the lay system; a low tension chute, track or wheel to align the product with the lay system tensioner central axis; a tensioner to control the pay-in / pay-out of product; a high tensioner chute or guide to orientate the product with the required vessel departure angle; a work table for installation of ancillary flexible, umbilical or cable equipment; a hang-off clamp for temporary suspension of product catenary during midline connections, end terminations or product testing; an abandonment and recovery system, typically a winch suitably rated for the dynamic catenary load anticipated, with sufficient wire length to reach the seabed or for cross-haul to a vessel crane; and a tower or framework to support the tensioner, chutes, work platform etc.

In known flexible, umbilical and cable lay systems the tensioner(s) is the critical component for controlling the pay-in / pay-out of product and normally dictates the maximum capacity of the complete system. A Tensioner being a piece of equipment with either two, three or four chain tracks driven by motors and comprising a series of friction pads mounted on the chain face. Tracks are positioned symmetrically and can be pushed in towards the product using hydraulic cylinders. With a controlled cylinder pressure, the tracks and thus friction pads, are forced against the product to create a frictional contact, which can be used to hold the product catenary load, or pay-in / pay-out product in a controlled manor. The friction pads are typically v-shaped generally with an obtuse angle of 140deg or 160deg. This allows either 4, 6 or 8 points of contact between the tensioner and product, depending if it is a 2-track, 3-track or 4-track system, respectively. Using this philosophy, a tensioner with defined squeeze pressure and contact length can resist a specific catenary load, governed by the product integrity. The product integrity being limited by the resultant radial and hoop stress imparted by the 4-point, 6-point or 8-points of contact. The limitation of system capacity is therefore the squeeze capacity of the product and contact length of the tensioner, assuming the friction coefficient as a constant.

In known tensioner lay systems there is little or no redundancy available in the event of product slippage as tensioners are generally employed to their upper load carrying capacity. The only option available is to increase the squeeze pressure of the tensioner pads, which can have a detrimental effect on radial and hoop stresses in the product, increasing stresses beyond their operational envelope.

From prior art, friction clamps are used widely within the oil and gas industry and are used specifically on flexibles, umbilical's and cables for temporary hang-off points, permanent mid-water arch clamps or subsea tether arrangements. Generally these are of a bolted nature for manual or ROV installation/removal. The clamps apply a near uniform radial load on the product and thus transfer the catenary load of the product through friction into the clamp body. Hydraulic friction clamps are used frequently in the installation of rigid pipelines, a concept commonly known as J-lay. These systems are used for the installation of rigid pipelines, where lengths of steel pipe are welded or screwed together in the vertical or inclined orientation to suit the require vessel departure angle, then deployed from the installation vessel. Either hang-off clamps or friction clamps are used to control the pipeline catenary, with one fixed clamp at the bottom of the J-lay tower to hold the catenary, while new lengths of pipe are added. A second travelling clamp at the top of the tower can then take the pipe catenary load, allowing the lower clamp to open. The travelling clamp can then lower the catenary a defined distance equal to the minimum spacing between clamps. The fixed clamp can then retake the catenary load as the travelling clamp returns to its upper position for the process to be repeated.

Known hydraulic friction clamps either use radial cylinders in layers positioned symmetrically around the product, with friction pads, specific to pipe diameter range, mounted on the piston ends; or tapered wedges, sized to suit the product diameter and with friction pad mounted to the contact face, which can be driven in the direction of the product axis to create radial pressure on the product. The cylinders or tapered wedges are housed within a body, which can resist axial load in the axial direction of the product.

It is noted that, as is known in the art, the friction clamp forms an annular ring around the product trajectory in normal operation but contains at least one hinged opening to allow the clamp to be removed from the product when not in use or as operations dictate.

By definition the use of the terms flexible, umbilical, cable or product refer to flexible pipe used commonly in the oil and gas industry for transportation of liquids or gas, both along the seabed and between subsea and surface structures; cable used to transport consumables, telecommunications or power between subsea and surface structures; and cables used in tension for positioning of equipment or structures.

The present invention aims to provide an improved flexible, umbilical and cable deployment and recovery system, or at least provide an alternative methodology.

The invention further aims to provide full redundancy for load carrying capacity in the event of product slippage, without jeopardising the product integrity.

The invention also aims to provide improved operability and functionality in handling flexible, umbilical and cable ends as well as ancillary equipment commonly attached to the said product.

The present invention provides according to a first aspect thereof a system for installation and recovery of flexibles, umbilicals and cables, which is characterised in that it utilises two or more friction clamps, each with full load rating capacity, to deploy, hold or recover product in a sequenced manor.

The friction clamps are supported within a tower, frame, track or rails orientated in the horizontal, inclined or vertical axis. Cylinders or winches are used to raise and lower the clamps independently. The clamps work in sequence to deploy or recover product by engaging and moving one clamp in the product direction, while a second clamp remains disengaged and is either stationary or allowed to travel in the opposite direction to a predefined starting point. This clamp is then engage with the product and remains stationary or is moved in the product direction, while the first clamp disengages and returns to its start position.

The sequence described can either be performed manually with individual controls per clamp, or more practically through the use of a PLC driven software, which can semi or fully automate the product pay-in pay-out process.

The invention also provides the possibility to deploy the lower friction clamp into the water column below the installation vessel, where it is unsupported by the tower, frame, track or rails, but is suspended from a winch wire or series of winch wires. The lower friction clamp can therefore deploy or recover product of greater lengths than allowed by the constraints of a lay tower or vessel deck.

The lower clamp can further be used as a mechanism for deploying the product second end to seabed, or recovering the product second end from the seabed.

To assist with the installation and recovery of flexible, umbilical and cable ancillary equipment, plus oversize midline or end terminations, each friction clamp can be retracted from the product trajectory position to a parked or storage position, creating an unrestricted envelope for clear passage of equipment along the product centreline.

The possibility to deploy and recover flexible, umbilical and cable product using two or more friction clamps offers the opportunity to incorporate full redundancy into the lay system in the event of product slippage. Using prior art technologies such as a "slippage monitoring wheel" as a warning sensor, both clamps can be activated to engage with the product to increase the frictional resistance, without jeopardising the integrity of the product.

An additional benefit of the system is the near uniform radial load applied to the product through friction clamps, and the resultant significantly reduced stress distribution when compared against conventional Tensioner grip mechanisms.

With the friction clamp(s) retracted to a parked position, the operability of the product deployment or recovery sequence is increased offering the possibility to incorporate a larger variation of flexible, umbilical and cable ancillary equipment, mid-line connections and end termination design.

The invention also presents the industry with an alternative methodology for the deployment and recovery of product, not reliant on the use of Tensioners, which are costly items to manufacture or maintain, and are generally in short supply during peak operating periods.

When the invention is employed with a friction clamp suitable for subsea deployment, the system offers the unique advantages of incorporating an abandonment and recovery system within the product handling mechanism, rather than utilising an additional single purpose winch fed through the lay system.

The invention will now be disclosed in more detail referring to preferred embodiments shown in the drawings.

In the drawings:

Fig. 1 shows in side view an example of two friction clamps, according to the invention, mounted within a frame in the vertical orientation;

Fig. 2 shows the system of figure 1 in front view;

Fig. 3 shows the system of figure 1 in plan view;

Fig. 4 shows in side view an example of two friction clamps, according to the invention, mounted within a frame in the inclined orientation;

Fig. 5 shows in side view an example of two friction clamps, according to the invention, mounted within a frame in the horizontal orientation;

Fig. 6a, b show the friction clamp assembly mounted in the operational position when the system of Figure 1 is in use. The friction clamp is shown in side view and front view, respectively;

Fig. 7a, b show the friction clamp mounted in the parked or storage position when the system of Figure 1 is in use. The friction clamp is shown in side view and front view, respectively;

Fig. 8a, b, c, d, e illustrate the operational sequence of one fixed and one travelling clamp when the system of Figure 1 is in use;

Fig. 9 a, b, c, d, e illustrate the operational sequence of two or more travelling clamps when the system of Figure 1 is in use;

Fig. 10 a, b, c, d illustrate the operational sequence of product ancillary equipment handling when the system of Figure 1 is in use;

Fig. 11 illustrates the operational sequence of product midline connection assembly when the system of Figure 1 is in use;

Fig. 12 a, b illustrate the operational sequence of product second-end termination when the system of Figure 1 is in use.

In figures 1-3 the invention is mounted within a vertical frame (3), similar to a traditional vertical lay system. The frame is mounted over the side of a subsea construction vessel (28) but can as easily be mounted over the stern or through the vessel moonpool.

Product (21) is routed through the deck radius controller (6) and over the top radius controller (4). The product then travels vertical downwards through the centre axis of the upper friction clamp (1) and lower friction clamp (2) before exiting the installation / recovery vessel (28). The handling and control of product with the friction clamps is described in more detail below.

As is common in product lay systems, the frame (3) incorporates an A&R system for abandonment and retrieval of product (21). The A&R system comprises a traction winch (29), A&R wire (30) and a series of sheaves including a retractable sheave assembly (5). The retractable sheave, allows the A&R wire end to align with the product trajectory (31) during A&R operations, but to be moved to a storage location when not in use.

In figure 4 the invention is mounted within an inclined frame (25), with high tension chute (13) to control the product (21) bend radius and exit angle from the vessel (28). A work platform (14) complete with hang-off clamp (27) is used to install ancillary equipment (22) or make-up both midline connections (23) and end terminations (24) as with known prior art.

In figure 5 the invention is mounted within a horizontal frame (26), with high tension chute or wheel (16) to control the product (21) bend radius and exit angle from the vessel (28).

As is illustrated in Figure 6a, b the friction clamp (1, 2) is mounted within a travelling frame (11, 12). The friction clamp is shown positioned on the centre line of the product trajectory (31).

The travelling frame (11, 12) is moved within the frame (3, 25, 26) by either a cylinder (8, 10) attached to a wire (32) routed through a series of sheaves (7, 9). Alternatively a winch could be used to replace the cylinders depending on required stroke of travel and speed.

As is illustrated in Figure 7a, b the friction clamp (1, 2) can be retracted from the product trajectory (31) to a storage or parked position within the aperture of the travelling frame (11, 12). This allows passage of large ancillary equipment (22), mid-line connections (23) and end terminations (24) along the product trajectory.

Retraction of the friction clamp (1, 2) is done with a pivot frame (17, 33) and cylinders (15, 34); although it will be clear to the man skilled in the art that alternate methodologies can be used for this purpose.

The functionality of the frictions clamps (1, 2) will now be explained in more detail referring to figures 8 and 9.

Each friction clamp (1, 2) has the facility to remain stationary or to travel within the frame (3, 25, 26).

Figures 8a, b, c, d, e demonstrate the sequence of clamp movements to deploy product (21) from the construction vessel (28), with the lower friction clamp (2) kept stationary.

Figure 8a shows the lower clamp (2) gripping the product (21) and holding the product catenary load while the upper clamp (1) is moved to the top of its travel envelope.

Figure 8b shows the upper clamp (1) engage with the product and load is transferred to the upper clamp from the lower clamp (2). The lower clamp disengages with the product (21).

Figure 8c shows the upper clamp (1) lowered along with the product (21).

Figure 8d shows the lower clamp (2) engaged with the product (21) and the product catenary load transferred to this clamp. The upper clamp (1) is disengaged from the product.

Figure 8e shows the cycle complete. Steps shown in figures 8a, b, c, d can be repeated for product (21) deployment or reversed for product recovery.

Figures 9a, b, c, d, e demonstrates the sequence of clamp movements to deploy product (21) from the construction vessel (28), with both clamps (1, 2) travelling in sequence.

Figure 9a shows the lower clamp (2) gripping the product (21) and holding the product catenary load while the upper clamp (1) is moved to the top of its travel envelope.

Figure 9b shows the upper clamp (1) engage with the product and load is transferred to the upper clamp from the lower clamp (2). The lower clamp disengages with the product (21).

Figure 9c shows the upper clamp (1) lowered along with the product (21) and lower clamp (2) moved to the top of its travel envelope.

Figure 9d shows the lower clamp (2) engaged with the product (21) and the product catenary load transferred to this clamp. The upper clamp (1) is disengaged from the product.

Figure 9e shows the upper clamp (1) retracted to the top of its travel envelope and lower clamp (2) lowered to the bottom of its travel envelope along with the product (21).

The lower clamp has the additional option to continue travel subsea along with the product (21) to increase the efficiency of the pay-out process. This is limited by the allowable back tension capacity of either the frame (3, 24, 26), the top radius controller (4), bottom radius controller (6), or product storage mechanism, namely a carousel or reel drive system.

The above sequence is repeated for product (21) pay-out or reversed for product pay-in.

In the event of product slippage in either friction clamp (1, 2) a slippage monitor of know prior art can be implemented to instigate an emergency shutdown condition. Both clamps would be engaged with the product and pay-in / pay-out stopped. The reason for the slippage can then be investigated and resolved with-out jeopardising the product integrity.

The methodology for retracting friction clamps (1, 2) demonstrated in Figures 6 a, b and 7 a, b, is shown in an operation sense in figures 10-12.

Figures 10a, b, c, d show the process of product (21) handling by two friction clamps (1, 2) for installation of ancillary equipment onto the product.

Figure 10a shows the upper clamp (1) moved to the top of its travel envelope and engaged with the product (21). The lower clamp (2) is opened and retracted to its park position.

Figure 10b shows the ancillary equipment (22) installed on the product (21) and the upper clamp (1) lower to suit.

Figure 10c shows the lower clamp (2) moved from its parked position to the product trajectory (31), engaged with the product (21) and the catenary load transferred. The upper clamp (1) is then disengaged from the product and moved to the top of its travel envelope.

Figure lOd shows the cycle complete. Steps shown in figures 10a, b, c, d can be repeated for further installation of ancillary equipment (22), or the sequence reversed for removal of ancillary equipment.

Figure 11 illustrates the optional clamp (1, 2) and work platform (18,19, 20) positions for make-up of product mid-line connections (23). As the work platforms do not carry catenary load, they are light construction and can therefore be positioned at various levels.

Either the upper or lower friction clamps (1, 2) can be positioned at a range of heights to best suit the mid-line connection (23) geometry. Use of the A&R system (5, 29, 30) can also be used to lower the midline connection to its lowest level.

Figures 12a, b show the flexibility of the friction clamp system when used for second end deployment of product. In traditional vertical lay systems the length of second end terminations, such as the bend stiffeners (24), are limited due to the restriction of distance between A&R hook and top of Tensioner. With two or more travelling friction clamps the A&R wire (30) can be routed through the tower (3) rather than over the top, creating a more compact system. The flexibility to move the upper and lower clamp (1, 2) maximises the handling length of the bend stiffener.

Figure 12a illustrates the clamp (1, 2) positions for standard deployment or recovery of second end terminations (24).

Figure 12b illustrates the option to further lower the second end termination (24) for extended periods of testing where operable conditions may be more favourable.

Claims

1. A system suitable for the installation and recovery of flexibles, umbilicals and cables in a marine environment from a seagoing installation vessel (28), wherein the system comprises: • a vertical frame (3), inclined frame (25), or horizontal frame (26), with entry and/or exit chutes or wheels (4, 6,13, 16) to guide product from a storage reel or carousel into the sea, • two or more friction clamps (1, 2) mounted within said tower, with clamp centreline aligned with product trajectory (31), and with suitable guide rails (11,12) and frame to travel along the product trajectory within the tower envelope, • each friction clamp has either manual or hydraulic means to grip the product radially with friction pads and resist the whole product axial catenary load, • the friction clamp frame (11,12), supported by the tower, has the facility to displace the friction clamp from the active position aligned with the product trajectory (31), to a park or storage position out with the product trajectory envelope.

2. System according to claim 1, wherein the friction clamp frames (11,12) travel within the tower envelope and parallel with the product trajectory (31), which is done by cylinders (8,10) and/or winch wires (32) routed through a series of sheaves (7, 9).

3. System according to claim 1, wherein the friction clamp (1, 2) has an opening mechanism to allow removal from the product trajectory while product is routed through the system.

4. System according to one or more of the preceding claims, wherein the friction clamp (1, 2) is attached to the friction clamp frame (11, 12) via a tilting or hinged support (17,33), which allows the clamp to pivot about the horizontal axis using cylinders (15,34) between an active product trajectory (31) and storage position with respect to the tower (3) and product (21).

5. System according to claim 1, wherein the lower friction clamp (2) and frame (11) can be deployed out with the envelope of the tower to a subsea position for enhanced efficiency and operability.

6. System according to claim 5, wherein the subsea deployed friction clamp (2) can be used as an alternate abandonment and recovery system for the product (21).

7. System according to one or more of the preceding claims, wherein an A&R sheave (5) is positioned above the upper travel limits of the upper friction clamp (1), and wherein an associated A&R winch (29) and A&R wire (30) are provided, said A&R sheave being arranged such that said A&R wire can be positioned along the product trajectory.

8. System according to claim 7, said A&R sheave (5) incorporates a pivot mechanism to retract the A&R wire from the product trajectory when not in use.

9. System according to one or more of the preceding claims, wherein the tower can be positioned at various locations of the installation vessel (28) i.e. through the moonpool, on the side or on the aft of the vessel.