Offshore Jetty Fender Tubes Double-Walled Corrosion Protection
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Solution Overview
Problem
Offshore jetties, particularly those serving wind turbines, face rapid damage and corrosion due to seawater exposure, leading to short service lives and the need for frequent repairs or replacements, despite protective coatings and welding challenges with seawater-resistant materials.
Innovation Solution
The use of a double-walled structure for fender and support tubes, with an inner steel tube and an outer seawater-resistant metal alloy tube, providing enhanced corrosion protection and mechanical strength, along with seamless drawn tubes and copper-based alloys for improved durability and anti-fouling properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If protective coatings (paint or plastic film) are applied to steel fender tubes, then corrosion protection is improved, but the coating ages due to UV exposure and is easily damaged by mechanical means
Solution Approach 1:
The patent applies this principle by using a sacrificial zinc coating (galvanization) on the steel fender tubes. The zinc layer acts as a disposable protective barrier that corrodes preferentially, protecting the underlying steel structure. This sacrificial protection extends the service life of the steel tubes without requiring the steel itself to be seawater-resistant, thereby resolving the contradiction between initial corrosion protection and long-term durability.
Solution Approach 2:
The patent employs composite material construction by combining steel (for structural strength) with a zinc coating (for corrosion protection). This composite approach allows the steel to provide mechanical strength while the zinc layer provides enduring corrosion resistance, overcoming the limitations of paint or plastic coatings that degrade under UV and mechanical stress.
2Duration of action of stationary object
If seawater-resistant metal alloys are used for fender tubes, then service life is improved, but cost increases significantly
Solution Approach 1:
The patent applies local quality by providing corrosion protection only where needed - the outer surface of the fender tubes exposed to seawater. The steel interior and non-exposed areas remain unprotected, optimizing material usage. This selective protection approach extends service life without the expense of using expensive seawater-resistant alloys throughout the entire structure.
Solution Approach 2:
The sacrificial zinc coating serves as a cost-effective protective layer that corrodes in place of the expensive steel structure. This disposable protective layer prevents the need for expensive seawater-resistant alloys while maintaining acceptable service life, thereby resolving the cost-durability contradiction.
3Strength
If rigid steel fender tubes are used, then mechanical strength is improved, but friction and mechanical damage from boat contact increase
Solution Approach 1:
The patent applies this principle by coating the rigid steel fender tubes with a flexible zinc layer that can deform under boat contact. This flexible sacrificial coating absorbs mechanical impacts and friction from boat fenders, protecting the rigid steel structure underneath from direct mechanical damage while maintaining the structural strength needed for support.
Data Source
AI summary
The invention relates to a landing stage for a boat for the piles of offshore installations, said stage comprising fender bars (2, 3) extending substantially perpendicularly to sea level and a ladder (4), said ladder (4) being positioned closer to the pile than the fender bars (2, 3). The fender bars (2, 3) have an inner pipe consisting of steel that is not resistant to sea water and an outer pipe consisting of a sea-water resistant metal alloy.