Ball Valves with no graphite to contaminate process

Challenge: eliminating all potential sources of graphite in pharmaceutical final product

When a valve is specified as anti-static and fire-safe, it reduces the scope an engineer has. The most common solution is to use a ball valve. However, in order to achieve the fire-safe ratings, the manufacturers need to use Graphite as the fire barrier. Normally this does not pose a problem as the graphite is:

  1. Encapsulated in a recess and as it is a static seal it remains there
  2. In the stem packing area which is live-loaded by Belville washers

A problem can arise, however:

  • when the end-user needs to strip down the valves for cleaning between batches. Graphite by its nature is brittle and prone to flake and hence if the cleaning is not thorough it can result in graphite in the process
  • in high-cycle applications, or vacuum applications, where graphite in the stem might be able to enter the process stream

The solution:

Graphite has to be removed from the process stream or replaced. The drawing below shows exactly how this has been achieved:

 

  1. The graphite body seal (detail B) has been replaced by a Teflon seal and the fire barrier moved out to the flanges
  2. The stem packing (detail A) has been upgraded to the Hermetix (Carbon-filled PTFE) and not only has this removed the graphite, it has proven to be a much more robust sealing arrangement which can outlast traditional Graphite by a factor of 15, giving a valve with a high cycle capability – up to 500,000 cycles

These engineering improvements have been incorporated in the Habonim Hermetix “G” range of valves. A valve so reliable it comes with a 4 year warranty and exceeds the ISO 15848-1 standard

Should you wish to eliminate the potential for Graphite in your system please contact Brian Foley on +353 21 4510900 or +44 1633 877505 or send us a product enquiry

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