PTFE, EPDM, FKM, graphite gaskets: what must be clarified
The roles of medium-contact and compensating gaskets and four questions to ask about any seal material.
Short answer
The gasket material is chosen for the medium, temperature and washing modes. There is no universal “best” material; every replacement is a check of all four conditions.
Chemical resistance is always verified by the gasket manufacturer tables and confirmed by tests or operating experience — site tables do not replace this.
Two roles of gaskets
The medium-contact gasket works in the medium and defines chemical compatibility. The compensating gasket relieves the glass from tightening moments and thermal movements and can be made of another material.
Four questions to any material
Before accepting a material, answer:
- resistance to the medium and concentration at the working temperature;
- temperature range, including short-time peaks;
- compatibility with washing and sterilization (CIP/SIP);
- ageing and cycles: shrinkage, compression set, reuse.
Typical materials
PTFE is chemically inert and slippery but requires controlled tightening. EPDM suits aqueous and alkaline media and fears oils. FKM resists oils and many acids but is limited with steam and hot water. Graphite withstands high temperatures but needs care with oxidizers.