Buying gaskets for dairy, brewery and food processing equipment is difficult. The choice is limited to FDA gaskets or FDA approved gasket material because it’s essential to avoid tainting or contaminating the product. Cleaning and sterilization routines are a way of life, so gasket material must stand up to high temperatures and caustic cleaning agents. And last, clamping forces are low in equipment like kettles, mixers and sanitary pipe fittings, so the material must be soft.
Polytetrafluoroethylene, (PTFE) sometimes referred to as Teflon®, meets all these requirements. That’s why it’s used for gasketing throughout the food industry. PTFE is listed by the FDA under 21 CFR 177.1550, although this approval really only covers virgin PTFE material. PTFE with markings, adhesive backing or filler can be used in food applications, providing the inks, adhesives and fillers also meet FDA standards. If purchasing gaskets like these for a food industry gasket application, have the material supplier confirm they qualify as FDA gaskets.
Some gasket materials will absorb traces of food preservatives, but PTFE is almost completely non-reactive. It doesn’t pick anything up and neither does it pass anything over so there’s no risk of food being contaminated with traces of elastomers or cleaning agents. The Shore D hardness of PTFE is around 50, so it’s soft and easily compressible. That’s important when pipes and vessels are secured with clamps rather than bolted flanges. PTFE also has the advantage of retaining its properties at temperatures as high as 400°F (204°C). That’s why it survives steam cleaning.
PTFE is not perfect though. It has a tendency to creep, which could lead to reduced clamping loads. This is because, unlike elastomeric gasket material, PTFE doesn’t cross-link, so bolted joints with PTFE gaskets may need occasional re-torquing.
In food processing it’s essential to use FDA gaskets. These will typically be PTFE, although some other materials are FDA approved too. If a gasket is going to contact food products it’s always best to discuss the application with the material supplier and make sure the correct material is chosen.