GB2536198A

GB2536198A - Cofferdam

Info

Publication number: GB2536198A
Application number: GB1503491.1A
Authority: GB
Inventors: Paterson Stuart
Original assignee: Global Energy Group Access and Coatings Ltd
Current assignee: Global Energy Group Access and Coatings Ltd
Priority date: 2015-03-02
Filing date: 2015-03-02
Publication date: 2016-09-14
Anticipated expiration: 2035-03-02
Also published as: GB2536198B; WO2016139474A1; GB201503491D0

Abstract

A cofferdam for securing to an elongate member 50 such as the leg of an offshore platform. The cofferdam comprises a first shell portion 2 having a proximal end 202a and distal end 202b. The distal end has a perimeter greater than a corresponding perimeter of the proximal end such that the first portion is tapered to form a cone section 301. The proximal end has a moveable seal 9. The cofferdam further comprises a first extended portion 302 attachable to the distal end of the first portion. The moveable seal may be inflatable and a neoprene seal 303 may be placed between the first portion and the first extended portions. Supporting arms may be used to connect the distal end of the first portions to the elongate member. A walkway may be secured to a distal end of the portions or to the inside of the cofferdam.

Description

COFFERDAM

The present invention relates to a cofferdam for securing to an elongate member.

As offshore platforms become older, integrity and maintenance management becomes increasingly important. Maintenance of the superstructure is typically carried out by a rope access team or a dive team. The splash zone between high and low tides and swell suffers from unique types of degradation. It is also difficult to access with either divers or rope access teams. Thus, maintenance is often neglected or extremely costly.

In accordance with a first aspect of the present invention there is provided a cofferdam for securing to an elongate member, the cofferdam comprising: a first portion having proximal and distal ends; the distal end having a perimeter greater than a corresponding perimeter of the proximal end; and the proximal end having a moveable seal extending around its perimeter.

The moveable seal is typically contactable with an outer surface of the elongate member. The moveable seal is typically moveable perpendicular to the longitudinal axis of the first portion.

The moveable seal may be inflatable. The moveable seal may be pneumatically or hydraulically inflatable. The pneumatically inflatable seal may use air to move the seal. The moveable seal may be referred to as a pneumatic gasket or o-ring. The hydraulically inflatable seal may use oil to move the seal.

The moveable seal may have an input. The input may be suppliable with air, water, oil or other fluid to move the seal in at least one direction. The seal may be moveable in the opposed and/or other direction by relaxation of the seal and/or reduction in the fluid pressure, that may be air, water or oil pressure, in the seal.

The proximal end of the first portion may have two moveable seals extending around its perimeter. Two moveable seals may better ensure that in use a fluid-tight seal can be reliably provided against the elongate member. In particular, the provision of two seals allows each seal to be optimised for the particular local environment in which it will be placed.

In use, the two seals are typically vertically spaced on an inner surface of the proximal end of the first portion.

The first portion normally has a length of greater than or equal to 1 meter. The distance between the seal and distal end of the first portion may be equal to or greater than 1.5 metres, normally greater than or equal to 1.8 meters. Thus, in use, the distance between the outer surface of the elongate member and the inner surface of the distal end of the first portion may be equal to or greater than 1 metre, normally greater than or equal to 1.5 meters. When the length of the first portion is about 1 meter, the distance between the seal and distal end of the first portion is about 1.8 meters and the distance between the outer surface of the elongate member and the inner surface of the distal end of the first portion is about 1.5 meters.

The cofferdam may have a tapered portion between the proximal and distal ends of the first portion.

The cofferdam may further comprise a second portion. The second portion is typically the same as the first portion. The second portion normally has proximal and distal ends; the distal end having a perimeter greater than a corresponding perimeter of the proximal end; and the proximal end having a moveable seal extending around its perimeter.

The seal or two seals of the first portion may be contactable with the seal or two seals of the second portion so that, in use, the proximal end of the first portion provides a fluid-tight seal against the proximal end of the second portion.

The cofferdam may further comprise a first extended portion attachable to the distal end of the first portion. The cofferdam may further comprise a second extended portion attachable to the distal end of the second portion. Thus, the first extended portion and/or the second extended portion may allow a greater length of the elongate member to be covered by the cofferdam. In some embodiments, the first extended portion and/or the second extended portion are able to be mass-produced at a single size, and suitable for use around a variety of different sized elongate members, whereas the first portion and/or the second portion are specially formed to be securable to a particular size, especially diameter, of elongate member. In this way, the cofferdam may be a modular cofferdam.

The elongate member may be one or more of a riser, conductor, caisson, pipe, jacket, support frame, column and leg. The elongate member may have a diameter of from 0.5 to 8 metres.

The length of the first and/or second extended portion is typically greater than or equal to 2 metres.

The cofferdam may further comprise a seal contactable with the distal end of the first portion and the first extended portion. The cofferdam may further comprise a seal contactable with the distal end of the second portion and the second extended portion.

The cofferdam may further comprise an arm connectable to the elongate member and the distal end of the first portion and/or first extended portion. Thus, the cofferdam may be securable to the elongate member at both the distal end and the proximal end of the first portion. In use, the arm typically reduces the horizontal and/or vertical movement of the first portion and/or extended portion relative to the elongate member. The arm may be connectable to a bracket. The bracket is typically connectable to the elongate member.

The first and/or second portion may further comprise an outlet. An end of a pipe may be connectable to the outlet. A pump may be connectable to another end of the pipe.

In use the pump may be used to remove water or other fluid from the cofferdam.

The cofferdam may further comprise a walkway securable to the distal end of the first and/or second portion. The cofferdam may further comprise an internal walkway, securable to an inner perimeter of the first and/or second portion.

An embodiment of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which: Figure 1 is a cross section of a cofferdam according to an embodiment of the present invention and modular cofferdam; Figure 2 is a perspective view of the cofferdam; Figure 3 is a perspective view of the cofferdam during assembly; Figure 4 is a plan view of the cofferdam shown in Figure 2 during assembly; Figure 5 is cross-section of the cofferdam deployed on an elongate member; Figure 6 is a perspective view of an extended height cofferdam according to an embodiment of the present invention; and Figure 7 is an exploded view of an arm and bracket.

Figure 1 shows a cofferdam 1 attached an elongate member 50. The cofferdam 10 has a first portion 2 having proximal 202a and distal 202b ends. The distal end 202b has a perimeter greater than a corresponding perimeter of the proximal end 202a (as also shown in Figure 4). The proximal end 202a has a moveable seal 9 extending around its perimeter. The moveable seal 9 is shown contacting an outer surface of the elongate member 50.

The length 312 of the first portion is 1 meter, the distance 314 between the seal 9 and distal end 202b of the first portion 2 is 1.8 meters and the distance 316 between the outer surface of the elongate member 50 and the inner surface of the distal end 202b of the first portion 2 is 1.5 meters.

Figure 1 is also an illustration of a modular cofferdam 300 according to an aspect of the present invention. The modular cofferdam 300 comprises a cone section 301 and a top section 302. The cone section 301 comprises the first and second portions 2&3. The top section 302 is configured to fit against the cone section 301. A perimetrical seal 303 is provided between the top section 302 and the cone section 301 to provide a sealed connection between the two parts of the modular cofferdam 300. The perimetrical seal 303 is formed from a material containing neoprene. The cone section 301 is specifically constructed for fitting around the elongated member 50. The top section 302 is configured to fit a range of different cone sections. The top section 302 may be referred to as first and/or second extended portions.

Figure 2 is an illustration of a cofferdam 1 attached to a leg 50 of an offshore platform. The cofferdam 1 is formed from a narrowed shell portion 2, connected to a tapered shell portion 3. The tapered shell portion 3 tapers outwardly from the narrowed shell portion 2 to a widened shell portion 4. The shell portions 2, 3 & 4 may be referred to as the first portion. Securing ropes 30 are attached to the cofferdam 1 at a free end of the widened shell portion 4, also referred to as the distal end of the first portion. The securing ropes 30 are used to raise or lower the cofferdam 1 into position on the leg 50. A walkway 40 is also provided adjacent to the free end of the widened shell portion 4. The narrowed shell portion 2 is provided adjacent to an external surface of the leg 50. The narrowed shell portion 2 and the widened shell portion 4 both have a substantially annular cross-section. The leg 50 has a diameter of 1.5 metres and the narrowed shell portion 2 has an outer diameter of 1.75 metres. The narrowed shell portion 2, the tapered shell portion 3 and the widened shell portion 4 each have a shell thickness of 10 centimetres. The widened shell portion 4 has an outer diameter of 5 metres. The tapered shell portion 3 tapers outwardly with an angle of approximately degrees to the widened shell portion 4. The narrowed shell portion 2 has a height of 1 metre. The widened shall portion 4 has a height of 5 metres.

Figure 3 shows cofferdam 1 in two parts, comprising a first shell 5 and a second shell 6. The first shell 5 may be referred to as a first portion. The second shell 6 may be referred to as a second portion. The first shell 5 and the second shell 6 each comprise a part of the narrowed shell portion 2, a part of the tapered shell portion 3 and a part of the widened shell portion 4. The first shell 5 and the second shell 6 of the cofferdam 1 are craned into position using the securing ropes 30. In this initial position, both the first shell 5 and the second shell 6 are spaced away from the leg 50. The securing ropes 30 of the first shell 5 and the second shell 6 are then transferred to static rigging and secured by rope access teams. The assembly of the cofferdam 1 typically occurs out of the water and above the splash zone working area. A bracket 7 is also attached to the leg 50.

Figure 4 is an exploded view of the cofferdam 1 and seals 8&9. The first shell 5 is provided adjacent a first side of the leg 50 and the second shell 6 is provided adjacent a second side of the leg 50. A first seal 8 is shown between the first shell 5 and the leg 50; a second seal 9 is shown between the second shell 6 and the leg 50. The first 8 and second 9 seals are inflatable. Pneumatic supply lines 12 are provided within the first shell 5 and the second shell 6 to allow the first 8 and second 9 seals to be inflated.

The first shell 5 and the second shell 6 are each provided with a surface 10 and a seal 11 is provided on each facing surface 10. The seal 11 prevents water entering the cofferdam 1 between the first shell 5 and the second shell 6 when the cofferdam 1 is assembled.

Figure 5 shows the cofferdam 1 lowered into water 60, such that the cofferdam 1 covers a corroded region 51 of the leg 50, preventing the water 60 from reaching the corroded region 51 while a treatment process is being carried out. An external water level 61 is above the tapered portion 3 of the cofferdam 1, and within the widened portion 4 of the cofferdam 1. The seals 8&9 are inflated to provide a pneumatic seal between the leg 50 and the narrowed portion 2 of the cofferdam 1. A pipe 15 has a first open end 16 located inside the cofferdam 1, just above the narrowed portion 2, and a second open end 17 located outside the cofferdam 1. A pump 18 is provided between the first open end 16 and the second open end 17 and is used to pump water out of the cofferdam 1. The inside of the cofferdam 1 also comprises a ladder 19 and an internal walkway 20. The vertical position of the internal walkway 20 within the cofferdam 1 may be adjusted as required.

The bracket 7 is positioned around the leg 50. Four arms 21 connect the bracket 7 to the widened shell portion 4 of the cofferdam 1. The walkway 40 provides access to the mounting points of the securing ropes 30 and the arms 21, in addition to the pump 18. The bracket 7 restricts any vertical and horizontal movement caused by swell or tides when the cofferdam 1 is partially submerged in the water 60. The bracket 7 also acts as a secondary holdback for operations. Thus, the bracket 7 will safely hold the cofferdam in place even if the securing ropes 30 fail.

Figure 6 shows an extended height cofferdam 100 comprising a lower shell section 101 and an upper shell section 102 which extends from an upper surface of the lower shell section 101. The lower shell section 101 is substantially similar to the cofferdam 1 as described herein before. A top surface of the widened shell portion 4 is the top surface of the lower shell section 101 which is connected to a lower surface of the upper shell section 102. An upper surface of the upper shell section 102 is connected to the walkway 40. The upper shell section 102 has a height of 5 metres. The lower shell section 101 has a height of 5 metres. The upper shell section 102 may be referred to as first and second extended portions.

Figure 7 shows the bracket 7 secured to a leg 50. The bracket 7 is connected to the cofferdam 1 by four arms 21 (only one shown here). The arm 21 is pivotally connected to the restricting bracket 7. At an outermost edge of the arm 21, a slot 22 is provided. Four vertical brackets 23 (only one shown) are attached to an inner surface of the first shell 5 and the second shell 6, adjacent to an upper surface of the first shell 5 and the second shell 6. The arm 21 extends down from the bracket 7 to meet the vertical bracket 23. Two slots 24 are defined in the vertical bracket 23 to correspond to the slot 22 in the arm 21. Two securing pins 25 are inserted through the two slots 24. Two securing pins 25 are then passed through the slot 22. The combination of the bracket 7 and the arms 21 ensure that the cofferdam 1 is held securely in place on the leg 50, even when swell in the water varies the forces acting the cofferdam 1.

Modifications and improvements can be incorporated herein without departing from the scope of the invention.

Claims

CLAIMS1. A cofferdam for securing to an elongate member, the cofferdam comprising: a first portion having proximal and distal ends; the distal end having a perimeter greater than a corresponding perimeter of the proximal end; and the proximal end having a moveable seal extending around its perimeter.
2. A cofferdam according to claim 1, wherein the moveable seal is contactable with an outer surface of the elongate member.
3. A cofferdam according to claim 1 or claim 2, wherein the moveable seal is inflatable.
4. A cofferdam according to any preceding claim, wherein the proximal end of the first portion has two moveable seals extending around its perimeter.
5. A cofferdam according to claim 4, wherein in use the two seals are vertically spaced on an inner surface of the proximal end of the first portion.
6. A cofferdam according to any preceding claim, wherein the first portion has a length of greater than or equal to 1 meter.
7. A cofferdam according to any preceding claim, wherein the distance between the moveable seal and distal end of the first portion may be equal to or greater than 1.8 metres.
8. A cofferdam according to any preceding claim, wherein in use the distance between an outer surface of the elongate member and inner surface of the distal end of the first portion is equal to or greater than 1.5 meters.
9. A cofferdam according to any preceding claim, the cofferdam further comprising a second portion, the second portion having proximal and distal ends; the distal end having a perimeter greater than a corresponding perimeter of the proximal end; and the proximal end having a moveable seal extending around its perimeter.
10. A cofferdam according to claim 9, wherein the seal of the first portion is contactable with the seal of the second portion so that, in use, the proximal end of the first portion provides a fluid-tight seal against the proximal end of the second portion.
11. A cofferdam according to claim 9 or claim 10, wherein the proximal end of the second portion has two moveable seals extending around its perimeter.
12. A cofferdam according to any preceding claim, the cofferdam further comprising a first extended portion attachable to the distal end of the first portion.
13. A cofferdam according to claim 12, the cofferdam further comprises a second extended portion attachable to the distal end of the second portion.
14. A cofferdam according to any preceding claim, wherein the elongate member has a diameter of from 0.5 to 8 metres.
15. A cofferdam according to any preceding claim, the cofferdam further comprising an arm connectable to the elongate member and the distal end of the first portion.
16. A cofferdam according to any of claims 12 to 15, the cofferdam further comprising an arm connectable to the elongate member and the distal end of the first portion and first extended portion.
17. A cofferdam according to any preceding claim, the cofferdam further comprising a walkway securable to the distal end of the first portion.
18. A cofferdam according to any preceding claim, the cofferdam further comprising an internal walkway, securable to an inner perimeter of the first portion.Amendment to the claims have been filed as followsCLAIMS1. A cofferdam for securing to an elongate member, the cofferdam comprising: a first portion having proximal and distal ends; the distal end having a perimeter greater than a corresponding perimeter of the proximal end; and the proximal end having a moveable seal extending around its perimeter; the cofferdam further comprising a first extended portion attachable to the distal end of the first portion.2. A cofferdam according to claim 1, the cofferdam further comprising a second portion, the second portion having proximal and distal ends; the distal end having a perimeter greater than a corresponding perimeter of the proximal end; and the proximal end having a moveable seal extending around its perimeter.3. A cofferdam according to claim 2, wherein the seal of the first portion is contactable with the seal of the second portion so that, in use, the proximal end of the CO first portion provides a fluid-tight seal against the proximal end of the second portion.OC\I 20 4. A cofferdam according to claim 2 or claim 3, the cofferdam further comprising a second extended portion attachable to the distal end of the second portion.5. A cofferdam according to any of claims 2 to 4, wherein the moveable seals of the first and second portions are contactable with an outer surface of the elongate 25 member.6. A cofferdam according to any of claims 2 to 5, wherein the moveable seals of the first and second portions are inflatable.7. A cofferdam according to any of claims 2 to 6, wherein the proximal ends of the first and second portions have two moveable seals extending around their perimeter.8. A cofferdam according to claim 7, wherein in use the two seals are vertically spaced on an inner surface of the proximal end of the first and second portions.9. A cofferdam according to any of claims 2 to 8, wherein the first and second portions have a length of greater than or equal to 1 meter.10. A cofferdam according to any of claims 2 to 9, wherein the distance between the moveable seal and distal end of the first and second portions may be equal to or greater than 1.8 metres.11. A cofferdam according to any of claims 2 to 10, wherein in use the distance between an outer surface of the elongate member and inner surface of the distal end of the first and second portions is equal to or greater than 1.5 meters.12. A cofferdam according to any preceding claim, wherein the elongate member has a diameter of from 0.5 to 8 metres.13. A cofferdam according to any preceding claim, the cofferdam further comprising (r) an arm connectable to the elongate member and the distal end of the first portion.CO 14. A cofferdam according to any preceding claim, the cofferdam further comprising an arm connectable to the elongate member and the distal end of the first portion and C\I 20 first extended portion.O15. A cofferdam according to any of claims 2 to 14, the cofferdam further comprising a walkway securable to the distal end of the first and second portions.16. A cofferdam according to any of claims 2 to 15, the cofferdam further comprising an internal walkway, securable to an inner perimeter of the first and second portions.