Dr. Roy J. Plunkett discovered polytetrafluoroethylene in 1938 while working on something completely unrelated at DuPont's Jackson Laboratory. DuPont registered the original PTFE resin under the trademark "Teflon" in 1945 and began selling products containing the resin the following year. PTFE's low coefficient of friction (meaning slickness) and resistance to the effects of chemicals, temperature extremes and age have made it a valuable part of many industries.
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Most fittings in water pipes rely on two things to create a watertight seal--a tapered shape to the male and female parts and a sealing agent applied to the threads. The taper and thread pitch is a standard that has been in use for nearly a hundred years, referred to as NPT, or national pipe thread. The sealing agent is present to reduce friction between the components as they are threaded together as well as to fill any voids that might occur between the threads. PTFE tape has nearly replaced paste sealants in this application. Three to five wraps of PTFE tape on the male threads provide a consistent, leak-free seal between the parts.
Fittings for air compressors use the same NPT standard that is found on water lines. Apply PTFE tape to black iron pipe fittings in the construction of rigid air distribution systems. Use three to five wraps of tape on the male fittings. Use PTFE tape when fixing quick-connect fittings onto flexible air lines. It should also be used where quick-connect fittings are threaded into pneumatic tools.
Propane and Natural Gas
Gas lines also use NPT standard fittings for main lines. Most building codes require a thicker, higher density PTFE tape for gas lines. PTFE tape for gas lines is dyed yellow to confirm to inspectors that the correct specification was used. The yellow colour indicates flammable gas in both industrial and residential applications.
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