GB1602577A - Method of repair of underwater structures - Google Patents

Method of repair of underwater structures Download PDF

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Publication number
GB1602577A
GB1602577A GB2451478A GB2451478A GB1602577A GB 1602577 A GB1602577 A GB 1602577A GB 2451478 A GB2451478 A GB 2451478A GB 2451478 A GB2451478 A GB 2451478A GB 1602577 A GB1602577 A GB 1602577A
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United Kingdom
Prior art keywords
resin
repair
underwater
repairing
cleaning
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GB2451478A
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ENERGY SECRETARY OF STATE FOR
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ENERGY SECRETARY OF STATE FOR
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Priority to GB2451478A priority Critical patent/GB1602577A/en
Publication of GB1602577A publication Critical patent/GB1602577A/en
Expired legal-status Critical Current

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    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D37/00—Repair of damaged foundations or foundation structures

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  • Engineering & Computer Science (AREA)
  • Structural Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Mining & Mineral Resources (AREA)
  • Paleontology (AREA)
  • Civil Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)

Description

(54) METHOD OF REPAIR OF UNDERWATER STRUCTURES (71) I, THE SECRETARY OF STATE FOR ENERGY, London do hereby declare the invention for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to methods of repair of underwater structures using adhesives; more particularly the invention relates to treatment stages in such repairs.
The field of the invention includes any form of underwater structural repair involving the use of a repair component which is defined as a component to be secured by means of adhesive bonding techniques to an existing underwater structural member or alternatively to a new member itself constituting part of the repair operation but already in fixed relationship with the underwater structure.
Although in no way limited in its general application, the method of the invention might be used with advantage in the carrying out of underwater structural repairs similar to those described in copending UK applications Numbers 50596/77, 53626/77 and 24367/78 (Serial Nos 1598433, 1598434 and 1598435).
According to the present invention a method of repairing underwater structures using adhesives and involving a repair component as hereinbefore defined comprising the steps of cleaning of those surfaces of the underwater structure to come into contact with the repair component, the application of a pre-cat of resin adhesive to these surfaces within a period of 24 hours of cleaning, and the mating of the repair component to the underwater structure prior to effecting the adhesive bond.
Preferably the contact surfaces of the underwater structure are cleaned by for example water jetting with abrasive particles after which a chemical pretreatment to inhibit subsequent corrosion and improved bond strength may be employed.
The pre-coat of resin adhesive, which can be less than say 1 mm thick, needs to be applied as soon as possible after cleaning and at least within 24 hours.
In a first arrangement where the repair component is to be attached to the underwater structure by the direct application of resin adhesive, the contact surfaces of the repair component are cleaned and a pre-coat of resin adhesive applied within a short period of cleaning, the adhesive bond being achieved by the application of resin adhesive between the underwater structure and the repair component. The cleaning may be by grit blasting in air and the pre-coat should be applied as soon as possible after cleaning and at least within 24 hours, and in parallel with, or soon after (within 24 hours), the pre-coating of the contact surfaces of the underwater structure. The cleaned contact surfaces of the underwater structure and the repair component may be pre-treated by application of a suitable coupling agent or adhesion promoter prior to the resin adhesive pre-coating.
The resin adhesive is preferably injected into the space provided between the underwater structure and the repair component but irrespective of the method of application the final resin adhesive layer should be in situ as soon as possible but normally within say 15 days of the initial cleaning and pre-coating.
In a second arrangement where resin adhesive impregnated foam techniques are used to bond the repair component to the underwater structure the resin impregnated foam is applied to the cleaned surfaces of the repair component and the repair component/resin impregnated foam assembly positioned and clamped to the underwater structure as soon as possible after the application of the resin impregnated foam to the repair component, and preferably within say 2 hours.
Final clamping should also take place within say 15 days of the cleaning and precoating of the underwater surfaces.
Advantageously the adhesion of the resin impregnated foam to the contact surfaces of the repair component may be improved by working the resin into the surfaces by for example brushing or screeding before pressing the foam in place. The resin adhesive should be applied to the foam and the repair component surfaces within one half hour of its mixing.
Two typical applications of the invention will now be described by way of example only as they relate to the repair of underwater structures.
An initial preparation, common to both applications, is as follows.
After a preliminary clean to remove marine growth the structure to be repaired is examined to establish the extent of the damage, and to determine the accurate dimensions of the members to which the repair component will be attached. In making repairs to the joints in a steel platform it may be necessary to make templates to check the angles between platform joint members and to check departures from drawing dimensions.
Repair components are then manufactured in accordance with the nature of the repair to be effected. See above listed co-pending UK applications for suitable repair designs. Provision is made for rubber seals where injection techniques are to be used as a method of resin adhesive application. These seals and the design of the joint are chosen to minimise stresses due to resin contraction during cure. Solid rubber seals are normally acceptable but for large or variable gaps inflateble rubber seals may be used.
After manufacture the repair components may be temporarily placed in position on the structure underwater to check fit-up, adhesive line thicknesses, and sealing adequacy. Adhesive line thicknesses of 6 mm or less are desirable. At this stage clamping arrangements need to be established and where necessary temporary attachments to the underwater structure can be made with mechanical clamps or resin bonded pads.
In a first arrangement employing a simple resin adhesive bond which is to be applied by injection the following procedure is adopted. After the repair components have been dismantled and returned to the surface for drying, the underwater surfaces of the structure to be bonded are cleaned, to bare metal when the surfaces of the structure are metallic. Such cleaning can be affected by high pressure water jetting or wire brush cleaning methods although the preferred method is by water-jetting with abrasive grit. A chemical pre-treatment may then be employed if required. A pre-coat of resin is then applied by stippling, screeding or spraying after corrosion products formed on the exposed metal surfaces have been removed.This pre-coat is normally of less than 1 mm thickness and is applied as soon as possible after the grit blasing, normally within 4 hours although up to 24 hours may be acceptable. If it is not possible to waterjet the whole bonding area within this period, the initial resin applications can be applied in stages, by coating successive areas which can be cleaned in this time.
Each area should be protected after coating to avoid contamination of the resin by the abrasive.
After drying, the repair components returned to the surface should be gritblasted in air and a pre-coat layer of resin applied in a similar manner as soon as possible, normally within 4 hours although up to 24 hours may be acceptable. This operation should be carried out in parallel with the underwater pre-coating if possible or within as short a time as possible thereafter, ideally within 24 hours.
The repair components are then lowered to the repair location and clamped in position. The rubber seals are checked for leak tightness using injection of air or sea water. Care must be taken not to apply too high a pressure during this operation since this could easily damage the structure. A pressure slightly above that intended for the final resin adhesive injection, ie about 2 bar, should be used.
Provided the seals are satisfactory injection of the resin can proceed. In some circumstances it may be necessary to remove loosely adhering particles and other detritus by the passage of a fast moving, turbulent water stream through the space between the underwater structure and the repair component. This may be achieved for example by injecting air into the water stream. As an alternative the removal of such contaminants may be achieved by chemical methods.
To ensure even distribution of the resin the injection should be made through a series of injection points spaced typically at 100 200 times the resin adhesive thickness apart. Ths distribution of the resin should be checked by monitoring the resin leakage from a series of bleed holes which are closed when a steady stream of resin is emerging.
Injection equipment typically consists of twin pumps feeding metered quantities of the resin constituents to a mixing head. The mixing head is placed close to the injection point to minimise subsequent cleaning and the resin constituents would be held in subsurface containers unless the repair was near the surface, in which case the constituents could be piped from the support vessel.
Injection would be carried out as soon as possible after the initial cleaning and precoating, and normally within 15 days.
In a second arrangement where impregnated foam techniques are used the treatment to the contacting surfaces of the underwater structure are as described above with the initial cleaning, possible chemical pre-treatment and subsequent pre-coating. The repair components are then dried and the impregnated foam applied to the mating surfaces. Improved adhesion may be obtained by working the resin into the surfaces by brushing or screeding before pressing the foam in place. The repair components are then placed immediately in position and clamped. This operation should be carried out within 15 days of applying the initial pre-coat and within 2 hours (preferably less) of applying the first resin to the dry repair components. The resin should be applied to the toam and metal surfaces within one half hour of mixing, or before the mix has become unusable.In some circumstances, dependent upon the ambient temperature, accelerated cure of the resin or resin impregnated foam to achieve more rapid development of useful joint strength may be desired. This may be achieved by local and controllable heating of the resin in the region of the repair by for example the incorporation of heating elements in the resin.
Test samples bonded underwater should be made from each resin adhesive batch.
The samples should be of the same type ie injection or resin impregnated foam, and should be water-jetted and bonded at the same time as the repair. After cure underwater these should be transferred in a cold tank to a suitable test machine and tested before their temperature has risen significantly above that at the location of the repair.
After the repair has partially cured to achieve adequate joint strength and any tensioning devices have been set at their required load, the bonded areas can be examined for voids or lack of adhesion using a suitable non-destructive testing technique, eg ultra-sonic or forced resonance.
Suitable underwater resin adhesives are described in co-pending UK appliations 2419/77 and 47114/77 (Serial Nos. 1598431 and 1598432) and resin impregnated foam bonding techniques in co-pending UK application 2419/77 (Serial No 1598431).
The invention however is not limited to the use of these preferred resins and bonding techniques.
WHAT I CLAIM IS:- 1. A method of repairing underwater structures using adhesives and involving a repair component as herein-before defined comprising the steps of cleaning of those surfaces of the underwater structure to come into contact with the repair component, the application of a pre-coat of resin adhesive to these surfaces within a period of 24 hours of cleaning, and the mating of the repair component to the underwater structure prior to effecting the adhesive bond.
2. A method of repairing underwater structures as claimed in claim 1 wherein said structures are metallic and in which the contact surfaces of the underwater structure are cleaned to bare metal.
3. A method of repairing underwater structures as claimed in claim 1 or 2 in which the contact surfaces of the underwater structure are chemically pretreated to inhibit corrosion.
4. A method of repairing underwater structures as claimed in claim 1, 2 or 3 in which the cleaning is by means of water jetting with abrasive particles.
5. A method of repairing underwater structures as claimed in claim 1, 2, 3 or 4 in which the pre-coat of resin adhesive is applied as soon as possible after cleaning and at least within 24 hours.
6. A method repairing underwater structures as claimed in claim 5 in which the pre-coat of resin adhesive is applied within 4 hours.
7. A method of repairing underwater structures as claimed in any one of the preceding claims in which the contact surfaces of the repair component are cleaned and a pre-coat of resin adhesive applied within a short period of cleaning, the adhesive bond being achieved by the application of resin adhesive between the underwater structure and the repair component.
8. A method of repairing underwater structures as claimed in claim 7 in which the contact surfaces of the repair component are cleaned by grit blasting in air.
9. A method of repairing underwater structures as claimed in claim 7 or 8 in which the pre-coat is applied as soon as possible after cleaning and at least within 24 hours.
10. A method of repairing underwater structures as claimed in claim 9 in which the pre-coat is applied within 4 hours of cleaning.
11. A method of repairing underwater structures as claimed in claim 7, 8, 9 or 10 in which the pre-coating of the contact surfaces of the repair component is effected in parallel with, or soon after, the precoating of the contact surfaces of the underwater structure.
12. A method. of repairing underwater structures as claimed in any one of the
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (19)

**WARNING** start of CLMS field may overlap end of DESC **. Injection would be carried out as soon as possible after the initial cleaning and precoating, and normally within 15 days. In a second arrangement where impregnated foam techniques are used the treatment to the contacting surfaces of the underwater structure are as described above with the initial cleaning, possible chemical pre-treatment and subsequent pre-coating. The repair components are then dried and the impregnated foam applied to the mating surfaces. Improved adhesion may be obtained by working the resin into the surfaces by brushing or screeding before pressing the foam in place. The repair components are then placed immediately in position and clamped. This operation should be carried out within 15 days of applying the initial pre-coat and within 2 hours (preferably less) of applying the first resin to the dry repair components. The resin should be applied to the toam and metal surfaces within one half hour of mixing, or before the mix has become unusable.In some circumstances, dependent upon the ambient temperature, accelerated cure of the resin or resin impregnated foam to achieve more rapid development of useful joint strength may be desired. This may be achieved by local and controllable heating of the resin in the region of the repair by for example the incorporation of heating elements in the resin. Test samples bonded underwater should be made from each resin adhesive batch. The samples should be of the same type ie injection or resin impregnated foam, and should be water-jetted and bonded at the same time as the repair. After cure underwater these should be transferred in a cold tank to a suitable test machine and tested before their temperature has risen significantly above that at the location of the repair. After the repair has partially cured to achieve adequate joint strength and any tensioning devices have been set at their required load, the bonded areas can be examined for voids or lack of adhesion using a suitable non-destructive testing technique, eg ultra-sonic or forced resonance. Suitable underwater resin adhesives are described in co-pending UK appliations 2419/77 and 47114/77 (Serial Nos. 1598431 and 1598432) and resin impregnated foam bonding techniques in co-pending UK application 2419/77 (Serial No 1598431). The invention however is not limited to the use of these preferred resins and bonding techniques. WHAT I CLAIM IS:-
1. A method of repairing underwater structures using adhesives and involving a repair component as herein-before defined comprising the steps of cleaning of those surfaces of the underwater structure to come into contact with the repair component, the application of a pre-coat of resin adhesive to these surfaces within a period of 24 hours of cleaning, and the mating of the repair component to the underwater structure prior to effecting the adhesive bond.
2. A method of repairing underwater structures as claimed in claim 1 wherein said structures are metallic and in which the contact surfaces of the underwater structure are cleaned to bare metal.
3. A method of repairing underwater structures as claimed in claim 1 or 2 in which the contact surfaces of the underwater structure are chemically pretreated to inhibit corrosion.
4. A method of repairing underwater structures as claimed in claim 1, 2 or 3 in which the cleaning is by means of water jetting with abrasive particles.
5. A method of repairing underwater structures as claimed in claim 1, 2, 3 or 4 in which the pre-coat of resin adhesive is applied as soon as possible after cleaning and at least within 24 hours.
6. A method repairing underwater structures as claimed in claim 5 in which the pre-coat of resin adhesive is applied within 4 hours.
7. A method of repairing underwater structures as claimed in any one of the preceding claims in which the contact surfaces of the repair component are cleaned and a pre-coat of resin adhesive applied within a short period of cleaning, the adhesive bond being achieved by the application of resin adhesive between the underwater structure and the repair component.
8. A method of repairing underwater structures as claimed in claim 7 in which the contact surfaces of the repair component are cleaned by grit blasting in air.
9. A method of repairing underwater structures as claimed in claim 7 or 8 in which the pre-coat is applied as soon as possible after cleaning and at least within 24 hours.
10. A method of repairing underwater structures as claimed in claim 9 in which the pre-coat is applied within 4 hours of cleaning.
11. A method of repairing underwater structures as claimed in claim 7, 8, 9 or 10 in which the pre-coating of the contact surfaces of the repair component is effected in parallel with, or soon after, the precoating of the contact surfaces of the underwater structure.
12. A method. of repairing underwater structures as claimed in any one of the
preceding claims in which the application of resin adhesive between the contact surfaces of the repair component and the underwater structure to effect the adhesive bond occurs within 15 days of the initial cleaning and pre-coating.
13. A method of repairing underwater structures as claimed in claim 12 in which the resin adhesive is injected into the space provided between the underwater structure and the repair component.
14. A method of repairing underwater structures as claimed in any one of claims 1 to 6 in which the contact surfaces of the repair component are cleaned and in which resin impregnated foam is then applied to the cleaned surfaces of the repair component and the repair component/resin impregnated foam assembly positioned and clamped to the underwater structure as soon as possible after the application of the resin impregnated foam to the repair component.
15. The method of repairing underwater structures as claimed in claim 14 in which the repair component/resin impregnated foam assembly is positioned and clamped to the underwater structure within 2 hours of the application of the resin impregnated foam to the repair component.
16. A method of repairing underwater structures as claimed in claim 14 or 15 in which the adhesion of the resin impregnated foam to the contact surfaces of the repair component is improved by working the resin into the surfaces by, for example, brushing or screeding before pressing the foam in place.
17. A method of repairing underwater structures as claimed in claim 14, 15 or 16 in which the final clamping takes place within 15 days of the cleaning and pre-coating of the contact surfaces of the underwater structure.
18. The method of repairing underwater structures using resin adhesive bonds substantially as herein before described.
19. The methods of repairing underwater structures using resin impregnated foam substantially as herein before described.
GB2451478A 1978-05-30 1978-05-30 Method of repair of underwater structures Expired GB1602577A (en)

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Application Number Priority Date Filing Date Title
GB2451478A GB1602577A (en) 1978-05-30 1978-05-30 Method of repair of underwater structures

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GB2451478A GB1602577A (en) 1978-05-30 1978-05-30 Method of repair of underwater structures

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GB1602577A true GB1602577A (en) 1981-11-11

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU670142B2 (en) * 1993-01-19 1996-07-04 Sumitomo Corporation Method of and apparatus for treating wood material and porous inorganic material

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU670142B2 (en) * 1993-01-19 1996-07-04 Sumitomo Corporation Method of and apparatus for treating wood material and porous inorganic material

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