Skill: Applying PTFE tape to tapered pipe threads

Written by Jeff Hopkins | 10/17/12 8:32 PM

See how to do it right. Includes video, step by step instructions, and tools list.

Tapered pipe threads are one of the most common end connections found in industry. They are relatively simple to make up, however they always need a sealant since there are designed-in gaps between the male and female threads. This 3-minute clip shows how to apply PTFE tape, a thread sealant used on male tapered pipe threads:

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Filling gaps between roots and crests

There are many different sealants available. One of the most popular is PTFE tape. The letters stand for polytetrafluoroethylene. It's a thin film that fills in the gaps between the roots and crests of tapered pipe threads. PTFE tape lubricates the threads, which allows them to be more easily screwed together, to the point of deformation, which is what creates the seal.

Swagelok PTFE tape provides reliable sealing on metal pipe threads in applications up to 450 degrees Fahrenheit, or 230 degrees Celsius. It conforms to Commercial Item Description A-A-58092.

Assembling tools

To properly apply PTFE tape, you'll need a couple of tools in addition to the roll of tape:

An open-end wrench
A dry, soft-bristled brush
A vise or back-up wrench for the female pipe fitting.

Make sure that PTFE is right for the job. It should be used only on male tapered pipe threads. Do not use it on straight threads such as those used on flared, coned or tube fitting ends.

First, use the soft-bristled brush to thoroughly clean the male and female threads to remove all previously applied anti-seize compound or tape. Use 1/4 inch wide tape on 1/8 inch, 1/4 inch, and 3/8 inch male tapered pipe threads. Use 1/2 inch wide tape on 1/2 inch and larger male tapered pipe threads.
Wrap the tape in the direction of the thread spiral of the male pipe thread beginning with the first thread. Tape should never extend beyond or overhang the first thread. If it overhangs, the tape could shred and get into the fluid system.
While keeping the edge of the tape parallel to the face of the fitting, wrap two to three revolutions of tape. The number of revolutions depends on the thickness of the PTFE tape you are using. Swagelok PTFE tape is thicker than the average hardware store PTFE tape, so two to three revolutions is enough. If you are using thinner tape, you will need to apply more tape. Draw the free end around the threads tautly so that it conforms to the threads.
When you have wrapped enough tape, cut or tear off the excess tape. If the tape does not lie flat, firmly press the tape into the threads. Now tighten the male end connection into the mating female end connection until finger-tight. Then tighten the male end connection until wrench-tight.

Once the connection is tight, do not loosen it. Doing so could mean leakage at the pipe thread. That's all there is to it.

Stop leaks

Leaks are common, and small ones are often hard to find. Use our engineers to track down argon, helium, nitrogen, and CDA leaks as small as 1 x10-3 cm3/s. Then get a hand quantifying each leak and choosing cost-effective ways to tighten up.

Swagelok training

In our Swagelok Tube Fitting Safety Seminar, our Swagelok certified trainers will show you how to properly apply PTFE thread sealant and other sealants and lubricants, and then ask you to do it yourself under their watchful eye.

You will also learn about pipe fittings, tubing handling, how to correctly install a Swagelok tube fitting, and more.

Tool rental

Here are just three examples of tool and equipment rentals we offer:

Hydraulic & Pneumatic Tools—When buying doesn't cost-justify, rent swaging tools. They help insure correct assembly of our tube fittings and hoses.
Orbital Welding System Rental—Rent a system for welding 1/8"-4" tube OD. Available by the day, week or month. Also see our welding seminars.
Plastic Tube Flaring Tool Rental—Using PFA tubing systems with fine thread flare fittings? Rent the hot flaring tool for fast assembly and the best performance.