They provide bearing protection, lubricant retention, exclusion of contaminants and minimize or eliminate the leaking of fluids. They are able to perform well for long periods of time with a high rotating speed and in temperatures anywhere from -60°F to 200°F. Rotary seals perform even in poorly lubricated and dry conditions.
Rotary seals provide a seal for oxygen, gases, water, other fluids, hydrocarbons and food materials. They are found in any machinery with a spinning component within the hydroelectric power, hot and cold steel rolling, chemical and petroleum processing, automotive manufacturing, food and pharmaceutical, machine tooling, pulp, paper and textile processing and hydraulic industries.
Gearboxes, marine propulsion systems, process mixers, tunnel boring machines, recreational vehicles and other machines and equipment use rotary seals, which, when used correctly, lengthen the system’s lifespan and increase its durability. Some are made of metal or plastic materials, but the most popular material for rotary seals is Teflon, or PTFE.
This material is inert, meaning it will not react with most chemicals, and it performs well under high pressures and in vacuum environments. Some Teflon rotary seals are made specifically for food and beverage processing or pharmaceutical manufacturing applications and must meet strict FDA requirements. Most Teflon seals contain strengthening additives like graphite, bronze, glass and carbon.
Rotary seals have many different profiles, but they are usually round and shaped much link an o-ring. They are always symmetrical, meaning their cross sections are mirror images of each other. Because this type of seal is usually made out of Teflon, a material that cannot melt, they are all manufactured by the sintering process.
Sintering takes Teflon in powder form, places a dense amount in a rotary seal-shaped mold that is subjected to high heat in an industrial furnace for a certain length of time before being rapidly cooled. This forces the powder to adhere together and condense into a hard, black plastic or rubber-like product that is inert, resistant to most chemicals and substances and can withstand large amounts of pressure and even vacuum environments. While the primary function of seals in rotary applications is to retain the bearing lubricant, they also enhance the life and performance of the bearing by minimizing all dirt, oil and water ingress.