Stability in the cleaning process
Among the most important requirements when designing a seal is not only the stability of the sealing material against the product in which the seal is being used, but also the compatibility with various cleaning agents and steam temperatures of up to 140 °C. The aggressive cleaning media on the basis of acids, alkaline solutions and peroxides are sometimes a greater challenge to the seal materials than the product medium itself. In addition to that, the high cleaning temperatures make the effect of the media on the material even worse.
Extensive series of tests
This is why Freudenberg Process Seals has carried out extensive explosure tests. The database of CIP /SIP cleaning media alone covers more than 200 analyzed recipes and more than 3,500 individual measurements. The usual test conditions are aimed at popular CIP /SIP media and were carried out at the highest recommended application concentration and temperature. The duration of exposure was at least 1 week, in individual cases even up to 4 weeks.
In the following an overview of the test results:
EPDM
EPDM is highly stable against acids, alkaline solutions, oxidizing media as well as against cleaning media and sterilization (even with steam). In fatty media at higher temperatures and concentrations, EPDM swells and can therefore not be used as a universal sealing material. The application temperatures reach from –40 °C to +150 °C in air and in water vapor up to +180 °C (briefly even +210 °C).
HNBR
If a seal is predominantly to be stable against non-polar media, then the use of the material HNBR can be considered. Seals made out of this material can be used in a wide spectrum, however the service life in aggressive CIP /SIP cleaners is lower. HNBR is not suitable for use in concentrated acids. The application temperatures in air and water range up to +150 °C.
VMQ
If the seal does not necessarily have to be subjected to the conditions of hot steam sterilization, then silicone (VMQ) can also be used as an alternative to HNBR. This material has a wide stability spectrum against non-polar and polar media, can however only be used in water vapor up to temperatures of +120 °C. The application limits in air range from –50 °C up to +200 °C.
FKM
If you need a seal that can be used in non-polar media, such as fats and oils, up to +180 °C and which is also stable in CIP /SIP media and water vapor, then fluoroelastomer (FKM) can be used. This elastomer compound is also highly suitable for sealing citrus juice and essential oils. The temperature range in air ranges from –15 °C up to +200 °C.
Fluoroprene® XP
Seals made of Fluoroprene® XP 40 can be used if EPDM can no longer be considered because the fat concentration of the medium to be sealed is too high. Because this sealing material is not only highly stable both in acids, alkaline solutions and steam, but also in fats, and the most common flavorings have no effect on it. This material can be used in temperatures from –10 °C to +200 °C.
Simriz®
If the requirements are so high that none of the aforementioned sealing materials can be used, then seals made of perfluorelastomer (FFKM) are used. Simriz® offers comprehensive media stability in a temperature application range of up to +260 °C.