The difficulty of sealing within vacuum mixing and homogenisingplants used in pharmaceutical and cosmetics industry processing ledBusak+Shamban engineers to research an FEP encapsulated O-Ringsolution. The primary problem with the use of ordinary elastomerO-Rings in this field of application is the seal’s inability toretain integrity when harsh chemicals are used in CIP (cleaning inprocess) and SIP (sterilisation in place) processes. Essentially,the O-Ring must achieve a small axial direction but, followingcleaning processes, elastomer O-Rings are inclined to stick withinthe groove housing.
The FEP O-Ring consists of an elastomer inner ring and aseamless FEP encapsulation sheath around this. The desiredelasticity is provided by the elastomer ring and the chemicalresistance by the seamless FEP sheath. The seal is usually used asa secondary sealing element in conjunction with mechanicalseals.
For this specific area of pharmaceutical and cosmeticprocessing, the task was to provide effective sealing to cope withharsh cleaning procedures, to operate at pressures from vacuum to 3bar and tolerate temperatures up to 155 ºC. The surface roughnessof the housing was Ra 0.1 to Ra 0.4 and the O-Ring inner diameterswere from 25 to 135 mm. No change in groove design waspermitted.
The FEP encapsulated O-Rings solution provided by Busak+Shambanfor this demanding application, comprised of an inner ring in FKMmaterial (to cope with a temperature range –20 ºC to 200 ºC) andVMQ material (to cope with a temperature range –60 ºC to 200 ºC),with the outer sheath material in thermoplastically mouldableTetraflourethylenhexaflouropropylene FEP.
Inherent qualities of FEP encapsulation provided a reducedfriction force, excellent resistance to most liquids and gases,resistance to abrasion and conformity to FDA regulations.