Composite water jacket enables seawater to be used to cool tensioning brakes
26 January 2011
A new design of composite water jacket that enables seawater to be used to cool tensioning brakes has enabled Wichita Clutch to improve the operation of marine-duty water cooled clutches and brakes used for tensioning on offshore oil and gas platforms and in other heavy-duty applications. The new composite design enables Wichita’s AquaMaKKs clutches and brakes to be cooled either with salt water, or water with high acidic PH levels.
Prior to its development, the industry standard was to use cast iron water jackets, alternating with copper wear plates, to dissipate the high heat generated in heavy-duty tensioning applications. In marine environments, however, salt corrosion created maintenance issues that necessitated too-frequent repair or replacement of the cast iron water jackets.
The composite material used in the new water jackets was developed by Wichita engineers working in conjunction with a partner firm. Several polymer combinations were tested before selection of the high-tech blend that satisfied the essential design requirement: which was to be as strong as the original iron parts' and match their typical design stresses.
In the event, structural testing couldn't cause a failure in the AquaMaKK’s 36-inch diameter composite water jacket, even when the part was stressed to more than four- times its maximum design load. Further testing, to determine the longevity of the composite jackets has been ongoing for two years at Wichita's engineering test lab. This has proven that the composite water jackets are at least as long-lived as the cast iron jackets, while also providing superior corrosion resistance in off-shore applications.
In addition to material selection, the most difficult technical challenge in redesigning the AquaMaKKs was to design the water porting in and out of the composite water jacket. Initially, because composite materials can be moulded into threads, it was thought the water porting could be built into the base material; however, this configuration failed to offer the robustness required in the industry. Finally, Wichita engineers achieved the necessary robustness by designing metal threads (male and female), which are moulded into the composite material.
Since the composite material is a thermal insulator, the cooling water moving through the composite water jacket picks up more of the frictional heat compared with an iron water jacket. Thus, the surrounding parts in a unit remain at cooler temperature, which contributes to longer life.
As well as their anti-corrosion benefits, the Composite water jackets offer an additional benefit of weight reduction, with some units weighing at least 50+% less than the iron jackets. For example, the 36-inch AquaMaKKs cast iron water jacket weighs 375 lbs. While the composite water jacket weighs only 90-96 lbs. This is significant in the multi-plate (friction disc) design in which each of the copper friction discs requires two water jackets – one on each side of the disc. Depending on the braking/holding requirement of the application, some units may have up to four discs and eight water jackets.
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