When to use PTFE Teflon Yellow or White tapes or Pipe Dope

                         When to use White PTFE Teflon Tape  or Yellow tapes or Pipe Dope

The purpose of thread seal tape (a.k.a. “Teflon tape”) or pipe dope is threefold:

• First, the lubricant qualities allow male threaded pipe to be turned deeper into female threaded fittings to prevent leaks;
• Second, it acts as a filler to smooth out micro abrasions or surface irregularities on threads;
• Third, it keeps the male and female threads from rusting together (a.k.a. seizing);

PIPE THREAD TYPES

AN thread is a type of fitting used to connect flexible hoses and rigid metal tubing that carry fluid (it stems from a joint standard by the U.S. Army and U.S. Navy, hence “AN”).

AN thread provides a positive seal that should seal correctly with specified torque torque range with no leaks. The AN should not require a thread sealant.

National Pipe Thread (NPT) taper is a U.S. standard for tapered threads used on threaded pipes and fittings.

In contrast to straight threads that are found on a bolt, a tapered thread will pull pipes and fittings tight together, providing effective seal for pipes transporting liquids, gases, steam and other fluids.

Although SAE and ASTM (organizations that set U.S. industry standards) set very precise thread class specifications, many threaded products carried by large box retailers have varying degrees of deviations from set specifications (i.e. micro surface imperfections like chatter or spalling), thus requiring a use of thread sealants.

PTFE  SEAL THREAD TAPE

When a Teflon seal tape was first introduced, it only came in a single density type (“white Teflon tape(1)“) that was commonly found in large home improvement stores. Later they began making a double density version, which was twice as thick in the same color (unfortunately with the same “white” color).

(1)Teflon tape is used ubiquitously when referring to a thread sealant tape. However, the word “Teflon” is a trademark name owned by Dupont Chemical Corp. Although Dupont no longer manufacturers Teflon tapes, it still enforces its trademark rights. That is why you see other manufacturers like Oatey refers to it as PTFE (PolyTetraFluoroEthylene) thread sealant tapes.

One very important thing to remember is that PTFE thread sealant tapes and pipe joint compounds are only to be used on NPT male threads. Neither should be used on SAE mechanical threads or as a gasket sealer (i.e. sink basket gasket).

Teflon THREAD SEAL TAPE COLORS

Since many state and local codes adopted the use of double density tapes when making connections for natural gas, the use of same color for two different thickness presented a challenge when time came to inspect a job. Thus, a “yellow TEFLON tape” was later introduced for such application.

Since then, ASTM has broadened the specifications for PTFE tape colors:

• White, single or double density, should only be used on NPT threads up to 3/8 inch in diameter
• Yellow,double density, often labeled as “gas tape”
• Pink, triple density, required on all joints 1/2″ or larger
• Green,Oil Free PTFE tape, required for use on all lines carrying oxygen (i.e. – medical oxygen or welding oxygen lines)

The above information is from PTFE tape manufacture and we hope the above information can help you understand types of Teflon thread seal tapes.