EP0295254A1 - Amelioration apportee a la protection des pilots. - Google Patents

Amelioration apportee a la protection des pilots.

Info

Publication number
EP0295254A1
EP0295254A1 EP87901546A EP87901546A EP0295254A1 EP 0295254 A1 EP0295254 A1 EP 0295254A1 EP 87901546 A EP87901546 A EP 87901546A EP 87901546 A EP87901546 A EP 87901546A EP 0295254 A1 EP0295254 A1 EP 0295254A1
Authority
EP
European Patent Office
Prior art keywords
wrapping
pile
sheet
around
inner layer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP87901546A
Other languages
German (de)
English (en)
Other versions
EP0295254B1 (fr
Inventor
Anthony Edward John Strange
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
NICC Ltd
Original Assignee
NICC Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by NICC Ltd filed Critical NICC Ltd
Publication of EP0295254A1 publication Critical patent/EP0295254A1/fr
Application granted granted Critical
Publication of EP0295254B1 publication Critical patent/EP0295254B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Classifications

    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
    • E02D5/22—Piles
    • E02D5/60—Piles with protecting cases

Definitions

  • This invention relates to the protection of piles or risers, such as those of oil rigs, piers or jetties.
  • piles are usually massive steel tubing, or concrete or wooden members. Although they may initially be painted or otherwise coated, they inevitably become subject to corrosion or bacterial attack in the hostile environment of sea water. This is particularly so over the splash zone, where the pile is alternately wetted and dried.
  • a filler material is poured in; for example concrete is suggested in British Patent No. 1352226.
  • Other proposals have been for an inert bonding material as in British Patents Nos. 1546710 and 1557071, or Specification No. 2108566A.
  • Such a jacket has to be tailor-made for the particular size of pile, and it also has to be in two parts at least so that it can be assembled around the pile. There also have to be spacers to keep the jacket uniformly distanced around the pile, adding to the complexity and cost.
  • a pile wrapping comprising a flexible sheet with means along opposed edges when the wrapping is positioned around a pile for fastening such edges together and affording counter-abutments for the application of a tool by which hoop stresses can be imposed on the wrapping before fastening is complete.
  • the sheet will have a certain elasticity, but the hoop stresses applied can be made sufficient to prevent the sheet being sucked clean off the pile by wave action.
  • the sheet preferably comprises an outer skin of water impermeable flexible material and an inner layer of liquid permeable material bonded to the skin and impregnated with a water resistant sealant.
  • the outer skin will be of reinforced plastics material while the inner layer may be of felted or porous plastics material.
  • the outer skin may have a thickness of the order of 3mm, and a suitable material is that used for the skirts of hovercraft.
  • the thickness of the inner layer may be of the order of 6mm, or at least sufficient to accommodate to variations in surface profile of that order of magnitude.
  • the wrapping is intended to go once around the pile, which is normally cylindrical. To help complete the seal at the contiguous edges the inner layer may have an extension beyond one edge to tuck under the opposite one.
  • the sealant impregnated in the inner layer may have other properties beyond just being watertight. It may incorporate corrosion inhibiting and anti-fouling components. Preferably, it will not form a permanent bond to a pile surface, and the fastening means will be releasable, so that the wrapping can be easily removed for inspection, and later re-used.
  • the inner layer and sealant will generally be covered by a removable backing sheet on manufacture, which will be discarded before positioning around the pile.
  • the wrapping sheet may also be adapted to form an element of a cathodic protection system, being a carrier for sacrificial anode material, or forming a jacket with a high dielectric constant, for example. It could also carry anti-fouling material externally.
  • a cathodic protection system being a carrier for sacrificial anode material, or forming a jacket with a high dielectric constant, for example. It could also carry anti-fouling material externally.
  • the sheet may be outwardly provided with handles so that divers can manoeuvre it into position. Also, it will be advantageous to have temporary strap fasteners for holding the wrapping around a pile at least during an initial phase of securing the permanent fastening means. Conveniently, there will also be gauge marks to provide an indication of the hoop stresses imposed.
  • the fastening means preferably comprises substantially rigid apertured flanges, outwardly projecting from the edges, and bolts for securing through the apertures.
  • a method of protecting a pile comprising wrapping a sheet as outlined above around the pile and drawing and securing opposite edges together by the fastening means to create hoop tensions that are resistant to wave suction forces.
  • this tensioning causes the sealant to exude into any surface irregularities.
  • the pile will normally be cleaned first, but it need not be done so with the meticulousness of some previous systems. Any vestigial marine growths or other imperfections will be firmly encapsulated and rendered impotent due to lack of oxygen and/or reaction to corrosion or anti-fouling inhibitors.
  • Figure 1 is a perspective view of a wrapping sheet in preparation for installing around a pile
  • Figure 2 is a perspective view of the sheet in a first stage of installation
  • Figure 3 is a cross-section of the pile with the sheet secured around it
  • Figure 4 is a diagrammatic elevation of the co-operating edges of the wrapping sheet
  • Figure 5 is a diagram of hydraulic closure apparatus.
  • the sheet is of composite construction having an outer skin 1 of material such as nylon reinforced Neoprene, 3mm thick, similar to hovercraft skirt material. Bonded to the rear side of this is an inner layer 2 of polypropylene felt, 6mm thick and impregnated with a polymeric thixotropic water-displacing gel sealant, formulated to act as a host for corrosion inhibitors and/or anti-foulants. It will be effective over a wide temperature range, say -40oC to 150oC. On manufacture this felt is protected by a peel-off backing sheet 3, which remains during transport and handling and is only removed by the divers as they fit the wrapping around the pile. Handles 4 to assist that fitting operation are bonded or otherwise attached to the outer face of the skin 1, as are straps 5 and fasteners 6 for temporary use as described below. The skin 1 also has permanent datum marks 7 for checking the stability of the wrapping.
  • the skin 1 also has permanent datum marks 7 for checking the stability of the wrapping.
  • Sealing members 8 in the form of substantially rigid flanges extend along the edges of the sheet that are to meet when it has been wrapped around a pile. They will project radially outwardly and each has a series of apertures 9 which register when the wrapping is in place.
  • the inner layer 2 is extended beyond one of the flanges 8 to form a flap 10 which will tuck under the opposite inner edge portion of the layer 2 and form an overlap, thus ensuring a good seal.
  • the flanges 8 may extend the full length of their respective edges, but if several are to be used in series along a pile, the flanges 8 will be short of each end, by 75mm or thereabouts, for reasons explained below.
  • Figures 1 and 2 show a hybrid, with the flanges 8 short at the top end only.
  • the sheet is folded concertina fashion as shown in Figure 1. It may be loosely held thus by ropes or straps. It is then supported by variable buoyancy bags and floated to the pile to be wrapped. Divers release and unfold it, wrapping it around the pile, which will have been locally cleaned as mentioned above. Once roughly in place, it can be loosely secured by the straps 5 and fasteners 6 as shown in Figure 2, and usually one at the top, one at the bottom and one at the middle will suffice. The wrapping can then be adjusted longitudinally of the pile 11
  • hydraulic rams 12 as shown in Figure 5 are used, attached to a diver operated handpump 13 via flexible hoses 14. These have swivel connections 15 at their ends to the rams 12 and to the T-pieces 16 or manifolds at the pump 13. Although only two rams are shown, for wrappings of any length it will be preferred to use three, applied to the top, bottom and middle of the members 8 adjacent the straps 5.
  • the ram rods 17 are inserted through the registering bolt apertures 9 and quick-lock nuts are fitted to their ends. The rams are then briefly actuated to apply a light tension to the wrapping.
  • the datum marks 7 are used to measure and note the extension achieved, and this will be compared against a table, and recorded for future reference and checks.
  • two or more such sheets are applied and butt jointed together, using ones where the members 8 do not extend right to the ends.
  • a band or "cummerbund" which is simply a foreshortened version of the wrapping described with similar flanges by which, it is stretched tight and secured in the manner of the main wrappings. It may not need such a substantial inner layer and its flanges will preferably be offset circumferentially from those of the main wrappings to ensure a good seal.
  • the flanges 8 of the main wrappings will be arranged to be downstream in relation to the most powerful tidal stream or current expected and the offset of any cummerbund will preferably be 10o - 30o.
  • Such a wrapping can be removed by reversing this procedure. Unless its removal is occasioned by damage it will normally be possible to replace it. Minor punctures of the outer skin 1 will self seal as radial hoop stresses in the material will cause the permanently soft sealant impregnated in the inner layer to exude and fill a punctured cavity. However, even major cuts and tears will remain stable, the tension placed on the material during installation being less than that which causes tears to propagate. But, even though it will not be totally immune to damage, such a wrapping will provide additional impact resistance being, in effect, a cushion around the pile. In general, a particular material for the outer skin 1 has not yet been settled and different ones may be suitable for different applications. Polyester reinforced polychloroprene is one further example being considered. Likewise there may be suitable materials for the inner layer 2 other than the polypropylene referred to above, and rather than felt the material may be homogeneous but porous.
  • a further application is to use the system as a carrier for anti-foulant materials, preventing marine growth build up and consequent increase in current drag forces on subsea platform legs, risers and caissons.
  • This could be achieved by providing an additional outer skin, conveniently a foamed polymer matrix for the anti-foulant material, such as copper particles. If used solely for this purpose the inner sealant layer could be dispensed with. It will be understood however, that a single wrapping could combine any of these functions.

Landscapes

  • 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)
  • Bulkheads Adapted To Foundation Construction (AREA)
  • Piles And Underground Anchors (AREA)

Abstract

Une enveloppe de protection pour pilots a la forme d'une feuille flexible (1, 2) qui, lorsqu'elle entoure un pilot (11), comprend deux bords contigus. Ceux-ci présentent des abouts (8) qui, lors de l'utilisation, sont pressés l'un contre l'autre par un outil mécanique et fixés de façon appropriée par des écrous (19) et des boulons (18). La tension tangentielle induite dans l'enveloppe permet aux pilots de résister aux forces d'aspiration des vagues. L'enveloppe peut comporter une couche intérieure (2) contenant un agent d'étanchéité résistant à l'eau placé en contact étroit avec le pilot lors de l'application de la tension. L'enveloppe peut également présenter des propriétés anti-salissures et des propriétés de protection cathodique.
EP87901546A 1986-02-20 1987-02-20 Amelioration apportee a la protection des pilots Expired - Lifetime EP0295254B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB868604285A GB8604285D0 (en) 1986-02-20 1986-02-20 Protection of piles
GB8604285 1986-02-20

Publications (2)

Publication Number Publication Date
EP0295254A1 true EP0295254A1 (fr) 1988-12-21
EP0295254B1 EP0295254B1 (fr) 1991-11-06

Family

ID=10593424

Family Applications (1)

Application Number Title Priority Date Filing Date
EP87901546A Expired - Lifetime EP0295254B1 (fr) 1986-02-20 1987-02-20 Amelioration apportee a la protection des pilots

Country Status (7)

Country Link
EP (1) EP0295254B1 (fr)
JP (1) JPH01501641A (fr)
AU (1) AU599958B2 (fr)
BR (1) BR8707601A (fr)
GB (1) GB8604285D0 (fr)
OA (1) OA08904A (fr)
WO (1) WO1987005066A1 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5102265A (en) * 1990-08-31 1992-04-07 T C Manufacturing Co., Inc. Adjustable width split sleeve and method of forming ends thereto
US5476576A (en) * 1991-08-15 1995-12-19 Winn And Coales International Limited Impressed current cathodic protection system
GB9207624D0 (en) * 1992-04-08 1992-05-27 Strange Anthony E J Improvements relating to the protection of corrosion-susceptible members

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE411382A (fr) *
AU422555B2 (en) * 1966-09-09 1972-03-22 Divework Limited Improved method of and means for protecting underwater woodwork against attack by marine organisms
US3939665A (en) * 1974-01-08 1976-02-24 Bethlehem Steel Corporation Method for protecting metal H-piling in underwater environments and protected H-piling
FR2337792A1 (fr) * 1976-01-07 1977-08-05 Liddell Orval Enveloppe ou appareil assurant la protection d'un element metallique de structure, contre la corrosion
AU495705B2 (en) * 1976-06-28 1978-01-05 E. Liddell Orval Apparatus for protecting metallic structural elements against corrosion

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO8705066A1 *

Also Published As

Publication number Publication date
GB8604285D0 (en) 1986-03-26
OA08904A (en) 1989-10-31
EP0295254B1 (fr) 1991-11-06
WO1987005066A1 (fr) 1987-08-27
AU599958B2 (en) 1990-08-02
JPH01501641A (ja) 1989-06-08
BR8707601A (pt) 1989-03-14
AU6949887A (en) 1987-09-09

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