The Ultra-Clean Variseal made of a proprietary PTFE-based material completely encloses the spring, thereby avoiding contact with fluids.

Processing and analytical equipment require seals to prevent even the slightest contamination of medical and pharmaceutical products. One seal design useful in processing equipment uses a spring to hold the seal material tight against a shaft. The seal is suitable for static, rotary, and reciprocating applications and has advantages of higher operating pressures and wider temperature ranges than elastomeric versions. The seal is made with our company's proprietary PTFE-based material, Turcon, which is compatible with most chemical media, has good wear resistance and friction characteristics, and withstands extreme operating temperatures.

An improvement is now referred to as ultra clean because the spring is completely enclosed by the seal and cannot trap contaminants. The design functions in much the same way as a standard design that exposes the spring, and works as a piston, rod, or face seal. The lip contact creates a sealing point with mating hardware. The spring provides sealing at low pressures, while the media increases sealing load at higher pressures. And a variety of lip designs let the seal work in demanding sealing requirements.

However, applying the seals to medical device and pharmaceutical tasks poses some challenges. For instance, seal materials must meet FDA requirements such as for fluid compatibility, cleanliness, and sterilization. Until now the main concern has been possible contamination or chemical reactions between fluid and spring. These applications require a change in strategy because fluid pressure helps seal at elevated pressures.

In the past, we recommended the Turcon Variseal Hi-Clean for medical and pharmaceutical applications. Its seal cavity would be filled with silicone to keep fluid and contaminants from contacting the spring. Packing the spring also prevents areas where bacteria may collect and breed. While these seals work well in most applications, it is possible for the bond between the silicone and seal material to break down, thereby letting fluids contact the spring.

The latest design resolves the issue. The energizing spring in this seal is fully enclosed with Turcon. These seal jackets are offered in five MF grades of Turcon developed for hygienic environments. All grades are compliant with FDA 21 CFR177.1550. In addition, other materials comply with 3A, USP Class VI, Cytotoxicity , and NSF. The pure MF materials provide low particle shedding and are more compatible with fluids than elastomers.

Operating temperatures range from -423F to +500F and pressures can exceed 1,450 psi. Seal jackets are also available in Zurcon polyurethane and PEEK. Springs come in slant coil and helical designs and can be made of stainless steel, Elgiloy, or Hastelloy. The seals retrofit nicely into standard AS-568 O-rings, Turcon Variseals, and extended grooves. The Ultra-Clean model can be installed in split, closed, and snap-fit grooves. No lubrication is required and shelf life is unlimited.