Fluid seal inventor makes mark with filters

Fluid seal inventor makes mark with filters

By Lisa A. Karter

Editor`s Note: This is the first in a series of articles celebrating the accomplishments of the distinguished members of the CleanRooms Hall of Fame.

He probably didn`t know it then, but in 1947, Adrian R. Allan Jr.`s love for sailing and a fascination of woodworking helped him carve an important role for himself in the cleanrooms in dustry. This was the year he found ed Flanders Filters, Inc. (Washington, NC).

Indeed, Allan was a pioneer, an entrepreneur and an inventor. He created the fluid seal, an interface be tween HEPA and ULPA filters and their supporting grids. He was also re sponsible for the development of separatorless HEPA/ULPA filters. Flanders Filters was the first company to produce its own filtration media, which led to the development of unique processes for the manufacture of separatorless, self-supporting filter elements.

Allan`s interest in the art of sailboat building spurred him into constructing a three-story mill. While completing a woodworking job for Brookhaven National Laboratory, he became interested in wood frame filters required for radioactive containment. The wood-framed HEPA filters were used in nuclear facilities to prevent airborne particles from escaping into the atmosphere. In the early 1960s, Allan decided to make not only the wood frame but also the filter medium — a non-woven matrix of very fine microfibers.

The fluid seal was invented during a time when Flanders was using a large rotating oven, which looked similar to a merry-go-round, to cure the adhesive from HEPA filters. During a visit from a Western Digital engineer in the mid-1960s, the question of bypass leakage around HEPA filters was discussed. It was during their conversation that Allan thought of the round cover on the rotating oven. The cov er was sealed at its rim by a knife edge im mersed in a trough of water, which ran around the sidewalls of the rotating oven. As the oven rotated, the heat was retained. During the meeting with the Western Digital engineer, Allan thought a fluid interface might solve the problem of bypass in vertical downflow cleanrooms. This technology earned two patents and has since been offered by most filter and cleanroom construction companies as the only way to successfully prevent bypass leaks around HEPA filters without constructing massive mating flanges that are often used in nuclear installations.

Allan also built the first (and only) glass papermaking process to produce self-supporting, also called separatorless, HEPA filter media. Allan wanted complete control over the most critical component in his product, the filter medium, and demonstrated his entrepreneurship by constructing a small paper-making machine that produced flat-sheet media. Once Allan perfected the production of media in-house, it occurred to him and his production manager that the material might be formed into something other than a flat sheet when in a wet state. The result was a machine that corrugated the wet glass paper as an integral step in the Fourdrinier paper-making process. The paper was pleated into a self-supporting filter element. Although the process is no longer in service today, it was the progenitor of several techniques and machines that are still in use today.

In recognition of his contributions to the contamination control industry, the late Adrian (Sam) Allan Jr. was inducted into the CleanRooms Hall of Fame in 1994.


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