While there are several options when it comes to approved polymeric or elastomeric seals for food processing applications, PTFE is one of the more popular choices–and that includes rotary shaft seals, as well.
Rotary shaft seals for food processing equipment have to do more than an ordinary seal: they also need to withstand aggressive cleaning and sanitation regimens that may involve corrosive chemicals, be approved for contact with food, and offer effective, reliable performance.
Where Shaft Seals are Used in Food Processing
Food processing machines that make use of shaft seals include mixers, food portioning equipment, dry product filling systems, ice cream dispensers, milk dispensers, high pressure homogenizers, water purification equipment, and distilled water pumps. They may be used with adhesives, flavorings, water, powders, preservatives, sauces, condiments, steam, and various fluids.
Rotary shaft seals for use in the food processing industry must be able handle the standard operating conditions involved such as speed, temperature, and pressure. However, their operating environment can involve more than that: consideration has to be given to the type of media they will be exposed to (e.g., powders, extremely viscous fluids).
PTFE is one of the polymers that has a proven track record with rotary shaft seals that have to function over a wide range of temperatures, pressures, and speeds, with various grades available that can offer more customized performance.
Rotary shaft seals must withstand the sterilization or cleaning procedures involved. CIP (Clean in Place), SIP (Sterilize in Place) and COP (Clean Out of Place) methods often require aggressive cleaning agents and/or superheated steam, powerful disinfectants, and potentially corrosive acids.
PTFE is highly resistant to a wide range of aggressive chemicals, can handle repeated exposure to hot water and superheated steam, and will not react chemically to the powerful disinfectants and sanitizers that food processing equipment is exposed to.
Safe for Contact with Food
Any part of a rotary shaft seal that comes into contact with food must conform to the appropriate regulations, such as FDA 21 CFR 177.1680, (EC) No. 1935/2004, and/or USP Class VI. Such approval is not easy to achieve: it takes into account whether the material releases any chemicals, tends to absorb moisture, goes through physical changes when exposed to high temperatures, reacts chemically to ingredients that are acidic, exhibits off gassing, and more.
PTFE comes in grades that are fully compliant with regulations regarding contact with food and FDA approved, making it a safe choice for rotary shaft seals for food processing equipment. In addition, it is the most chemically unreactive polymer on the market today.
Finally, PTFE rotary shaft seals have proven themselves to be highly reliable, which is why you will see them used in dangerous, mission critical applications where safety and ruggedness is vital, such as those found in the oil and gas or aerospace industries. If you are looking for a FDA-approved rotary shaft seal for use in food processing applications, PTFE seals should be at the top of your list.