Flexaseal’s first foray into cryogenic sealing solutions was through our Brazil location over 20 years ago. Helio Guida, a managing partner of Flexaseal Engineered Seals and Systems, LLC in Brazil, spent extensive time working with a large cryogenic mechanical seals end-user to identify their sealing challenges and options for a solution.
Formed Bellows Can Create an Unsafe Work Environment
Challenge
The facility used Grofe® cryogenic pumps, which were equipped with formed bellows assemblies. Formed bellows typically have a thicker convolution structure with a high spring rate (the amount of force needed to compress the unit a specified distance.) The higher the spring rate, the higher the unit load and the more heat generated around the seal. While these formed assemblies were suitable for cryogenic operating temperatures as low as -425°F (-253°C), the face load generated unacceptable levels of heat at the sealing faces, affecting the stability of the liquid gases. This was especially concerning when the boiling point for these gases was still well below 0°F (-17.7°C.) The danger when a flammable cryogenic liquid such as liquid hydrogen evaporates, just one liter of liquid can produce approximately 630 to 850 liters of gas. A volume of gas this large can very quickly lead to a flammable atmosphere, threatening personnel and environmental safety.
Replace Formed Bellows with Edge Welded Metal Bellows Component Seals for Cryogenic Pumps
Solution
Flexaseal engineers adapted our successful edge welded bellows design to this challenge. 347 SS, a stabilized stainless steel, was an optimal bellows material due to its strength and durability in extremely cold temperatures. Selecting the right seal face combination was even more critical, and the decision was made to utilize a cryogenic grade of carbon. The self-lubricating carbon material worked in tandem with the tight-toleranced bellows spring rate to alleviate a substantial percentage of the heat generated around the faces during operation.
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Edge Welded Metal Bellows Seals Guide
Edge Welded Metal Bellows Seal Improves Safety and Productivity
Results
Conversion to the Flexaseal cryogenic mechanical seals design increased MTBF to 6-8 months, which doubled the 3-4 months previously obtained with formed bellows. Because the seals were used in cryogenic gas transportation, the additional months of operation were essential in the continued safe handling of the liquid gases. The facility’s management was so impressed with Flexaseal’s commitment to finding a reliable solution that they worked with the Flexaseal do Brazil personnel to set up a repair/maintenance department within the facility to support ongoing success.
Our Commitment to Cryogenic Mechanical Seal Excellence
Today, Flexaseal Engineered Seals and Systems supplies cryogenic edge welded metal bellows assemblies all over the world. We continue to explore and evaluate the latest cryogenic sealing developments such as non-contacting cryogenic gas seals and labyrinth seal faces in our ongoing commitment to providing the best sealing solutions for your cryogenic challenges.
