Ropes having improved cyclic bend over sheave performance
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Solution Overview
Problem
High tenacity synthetic ropes used in marine applications experience premature wear when repeatedly bent over sheaves, particularly in wet conditions, and there is a need to enhance their fatigue life for cyclic bend-over sheave (CBOS) resistance and heavy lifting applications.
Innovation Solution
A rope comprising high tenacity fibers coated with a composition of amino functional silicone resin and neutralized low molecular weight polyethylene, or a blend of such fibers, which significantly improves CBOS fatigue resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high tenacity polyolefin fibers are used to make synthetic ropes, then the ropes have excellent strength and durability properties, but they experience premature wear when subjected to repeated bending over sheaves
Solution Approach 1:
A coating composition comprising amino functional silicone resin and neutralized low molecular weight polyethylene is applied to the high tenacity polyolefin fibers. This coating acts as an intermediary layer that protects the fibers during cyclic bend-over-sheave operations, preventing direct contact between the fiber surface and the sheave, thereby reducing wear and improving fatigue resistance while maintaining the underlying fiber strength
Solution Approach 2:
The surface properties of the polyolefin fibers are modified through the application of the coating composition. The coating changes the surface chemistry and physical characteristics of the fiber, creating a more durable interface that resists wear during repeated bending cycles. This parameter change at the surface level does not compromise the bulk strength properties of the high tenacity fibers
2Ease of operation
If synthetic ropes are used to replace steel wire in marine applications, then the ropes offer improved corrosion resistance and ease of operation, but they suffer from reduced fatigue life in cyclic bend-over-sheave applications
Solution Approach 1:
The coating composition serves as a protective intermediary that extends the service life of synthetic ropes in demanding marine applications. By protecting the fiber surface during cyclic bending operations, the coating enables synthetic ropes to maintain their operational advantages while achieving the fatigue life necessary for heavy lifting and marine industrial applications
3Reliability
If high tenacity fibers are coated with amino functional silicone resin and neutralized low molecular weight polyethylene, then the cyclic bend-over-sheave resistance is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The solution combines two different materials - amino functional silicone resin and neutralized low molecular weight polyethylene - into a single coating composition. This composite coating approach achieves superior CBOS fatigue resistance by leveraging the complementary properties of both materials, while the combination is applied as an integrated coating process rather than separate sequential coatings
Data Source
AI summary
An improved rope is formed from high tenacity fibers, preferably a blend of high tenacity polyethylene fibers with aramid fibers and/or liquid crystal copolyester fibers. The fibers and/or the rope are coated with a composition comprising an amino functional silicone resin and a neutralized low molecular weight polyethylene. The ropes are useful in marine applications, such as in deep sea lifting, and have improved cyclic bend over sheave fatigue resistance.