Offshore structure comprising a coated slip joint and method for forming the same

Abstract

Offshore structure comprising a pile of a foundation and at least one offshore element, mounted on the pile, forming a slip joint, wherein between an inner surface of the offshore element and an outer surface of the pile:a coating, especially an anti-fouling coating is provided, increasing friction between the said two surfaces and/or preventing corrosion of one or both of said surfaces and/orat least two spaced apart areas are provided with a substance, forming a seal between the said outer surface and the said inner surface, near an upper end of the pile and the off shore element and between a lower end of the off shore element and the pile.

1 . An offshore structure, comprising a lower end of at least one offshore element fitted over a top end at an offshore foundation pile that extends along a longitudinal axis in a vertical direction, forming a slip joint in the vertical direction of said longitudinal axis, wherein a surface area of the top end of the offshore foundation pile and/or a surface area of an inner surface of the at least one offshore element has been provided with a visco-elastic substance, wherein the visco-elastic substance is provided on an outer surface area of the offshore foundation pile that is spaced apart from an upper end of the offshore foundation pile and on an inner surface area of the at least one offshore element spaced apart from a lower end of said at least one offshore element. 
     
     
         2 . The offshore structure according to  claim 1 , wherein the visco-elastic substance has been provided on each of said inner and outer surface areas as a ring. 
     
     
         3 . The offshore structure according to  claim 1 , wherein the visco-elastic substance is applied such that overlapping surfaces of the top end of the offshore foundation pile and the at least one offshore element are separated from each other by said visco-elastic substance, such that a weight of the offshore element is transferred to the offshore foundation pile by the visco-elastic substance. 
     
     
         4 . The offshore structure according to  claim 1 , wherein the at least one offshore element comprises a tower, and wherein:
 the visco-elastic substance is applied to the outer surface of the offshore foundation pile, such that, part of the visco-elastic substance extends below a lower edge of the tower; and   the visco-elastic substance is applied to the inner surface of the tower, such that, part of the visco-elastic substance extends above an upper edge of the offshore foundation pile.   
     
     
         5 . The offshore structure according to  claim 1 , wherein a first slip joint is formed by directly mounting a platform on the offshore foundation pile and a second slip joint is formed by directly mounting a tower on the offshore foundation pile, both the first slip joint and the second slip joint being provided with said visco-elastic substance, wherein the second slip joint is provided above the first slip joint. 
     
     
         6 . The offshore structure according to  claim 1 , wherein said inner and outer surface areas provided with said visco-elastic substances are spaced longitudinally apart from each other. 
     
     
         7 . An offshore structure, comprising a lower end of at least one offshore element fitted over an upper end of an offshore foundation pile, forming a slip joint, wherein a surface area of the upper end of the offshore foundation pile and a surface area of an inner surface of the at least one offshore element is provided with a visco-elastic substance,
 wherein the visco-elastic substance is provided on an outer surface area of the offshore foundation pile spaced apart from the upper end of the offshore foundation pile and on said inner surface area of the at least one offshore element spaced apart from the lower end of said at least one offshore element, such that said surface areas provided with said visco-elastic substances are longitudinally spaced apart from each other.   
     
     
         8 . An offshore structure according to  claim 7 ,
 wherein the visco-elastic substances in said surface areas are compressed and partly deformed, forming two spaced apart seals between a tower and the offshore foundation pile, forming the slip joint, and wherein the visco-elastic substances are deformed such that part of the visco-elastic substance on the surface area of the top end of the offshore foundation pile has been pushed partly outside a lower end of the tower, effectively forming a water tight and gas tight first, lower seal and the visco-elastic substance in the surface area of the inner surface of the offshore element has been partly pushed upward out onto an upper end of the offshore foundation pile, effectively forming a water and gas tight second, upper seal.   
     
     
         9 . The offshore structure according to  claim 7 , wherein the surface area of the upper end of the offshore foundation pile is a first continuous, substantially truncated conical surface, wherein the surface area of the lower end of the at least one offshore element is a second substantially continuous, truncated conical surface, and wherein the visco-elastic substance forms two longitudinally spaced apart, ring shaped seals between said first and second substantially truncated conical surfaces. 
     
     
         10 . Offshore structure comprising a pile of a foundation and at least one offshore element, mounted on the pile, forming a slip joint, wherein between an inner surface of the at least one offshore element and an outer surface of the pile there is:
 a coating, increasing friction between the inner and outer surfaces and/or preventing corrosion of one or both of the inner and outer surfaces, or   at least two spaced apart areas with a substance, forming a seal between the said outer surface and the said inner surface, near an upper end of the pile and the offshore element and between a lower end of the at least one offshore element and the pile,   or both.   
     
     
         11 . The offshore structure according to  claim 10 , wherein the at least two spaced apart are provided with the substance, the substance forming the seal between the said outer surface and the said inner surface, near the upper end of the pile and the offshore element and between the lower end of the at least one offshore element and the pile, and wherein the substance forming a seal is a substantially visco-elastic material of compound of materials. 
     
     
         12 . The offshore structure according to  claim 11 , wherein the substance is formed by a mouldable, self-adhesive material, which material is watertight and gastight. 
     
     
         13 . The offshore structure according to  claim 11 , wherein said material extends at least partly over the lower end of the at least one offshore element and/or the upper end of the pile. 
     
     
         14 . The offshore structure according to  claim 11 , wherein the substance forms an upper seal and a lower seal between the at least one offshore element and the pile, wherein between said seals a space is enclosed between the at least one offshore element and the pile. 
     
     
         15 . The offshore structure according to  claim 11 , wherein the substance is provided between opposing sloping surfaces of the at least one offshore element and the pile. 
     
     
         16 . The offshore structure according to  claim 10 , wherein the coating and/or the substance is one of the following: free of organotin compounds, a foil, an adhesive foil, and a self-adhesive coating. 
     
     
         17 . The offshore structure according to  claim 10 , wherein the coating comprises a layer comprising fibers on a carrier foil, wherein the fibers are embedded in a resin, wherein the resin is a cured acrylic. 
     
     
         18 . The offshore structure according to  claim 10 , wherein the coating and/or substance is applied on the outer surface of the pile, on a truncated conical part of the pile and/or wherein the coating and/or substance is applied to the inner surface of the at least one offshore element. 
     
     
         19 . The offshore structure according to  claim 10 , wherein the coating is an anti-fouling coating and/or has a surface roughness higher than a surface roughness of the inner surface of the at least one offshore element and/or of the outer surface of the pile. 
     
     
         20 . The offshore structure according to  claim 10 , wherein the at least one offshore element comprises a tower or a platform. 
     
     
         21 . The offshore structure according to  claim 10 , comprising two offshore elements mounted on the pile, the two offshore elements forming a first slip joint and a second slip joint, and wherein a platform is mounted on the pile by a first slip joint and a tower is mounted on the pile by a second slip joint. 
     
     
         22 . The offshore structure according to  claim 10 , wherein a filler is provided between at least part of a surface of the coating and an adjacent surface.