What is a fishbone gasket?

Author:Zhao, Justin
Position::Tech Notes: Product Development
 
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An interesting name? You bet it is, and it merits some explanation. Fishbone[TM] Gasket is a recent innovation in the traditionally boring gasket market, and hopefully the ultimate solution for high-temperature and high-pressure sealing problems.

Gaskets are an important factor in plant safety. This is especially true for the industries moving lots of fluid, such as the oil and gas sector, chemical plants, paper mills and power plants. Similarly, pipelines flow volatile chemicals and hot pressurized steam with fluids passes at millions of connecting points, including flanges, valves seats, heat exchangers and reactor covers. Companies need reliable ways to seal--companies need gaskets.

Ideally, a good gasket should be both strong and elastic; yet in practice, it's difficult to balance one quality with the other. In over 90% of high-temperature and high-pressure applications, plant engineers face two primary options: the spiral-wound gasket and the camprofile gasket. What's wrong with those options? Why do we need a new design? The short answer is that though great inventions in their time, both are old designs that have difficulty maintaining strength and flexibility at the same time.

Invented in 1912, the spiral-wound gasket was comprised of metal strips spiraled with sealing elements in between. A spiral-wound gasket has obvious advanges compared to a single material gasket as it combines the strength of metal with the sealing capacity with the nonmetallic material. Yet, maintenance personnel soon found it was not 100% reliable.

Welded at the inner ends, the spirals sometimes unwound. The result? Metal strips were sucked into the pipeline system and leakage occurred at the flange, both posing a threat to plant safety and reliability. There can be several causes of "unwinding" including over-torquing, pressure surges or even a change in temperature. Not surprisingly, plants need a better design, something more reliable under extreme conditions--something stronger.

[FIGURE 1 OMITTED]

A major improvement came 60 years later Invented in 1976, the camprofile gasket consists of a metal skeleton, with each side grooved and covered with non-metallic sealing materials. By converting the spiral strips to a unitary metal structure, a camprofile gasket gains strength and will not unwind. Unfortunately, it loses elasticity and is rigid, resulting in poor recovery.

[FIGURE 2 OMITTED]

There have been several specialty designs --all together they account for less than...

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