Thread seal tape
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Thread seal tape (also known as PTFE tape or plumber's tape) is a polytetrafluoroethylene (PTFE) film for use in sealing pipe threads. The tape is sold cut to specific widths and wound on a spool, making it easy to wind around pipe threads. It is also popularly but incorrectly called Teflon tape despite DuPont, the holder of that trademark, no longer manufacturing it. Thread seal tape lubricates allowing for a deeper seating of the threads, and it helps prevent the threads from seizing when being unscrewed. The tape also works as a deformable filler and thread lubricant, helping to seal the joint without hardening or making it more difficult to tighten, and instead making it easier to tighten.
Typically the tape is wrapped around a pipe's thread three times before it is screwed into place. It is commonly used commercially in applications including pressurized water systems, central heating systems, and air compression equipment.
There are two US standards for determining the quality of any PTFE tape. MIL-T-27730A (an obsolete military specification still commonly used in industry in the US) requires a minimum thickness of 3.5 mils and a minimum PTFE purity of 99%. The second standard, A-A-58092, is a commercial grade which maintains the thickness requirement of MIL-T-27730A and adds a minimum density of 1.2 g/cm3. Relevant standards may vary between industries; tape for gas fittings (to UK gas regulations) is required to be thicker than that for water. Although PTFE itself is suitable for use with high-pressure oxygen, the grade of tape must also be known to be free from grease.
Thread seal tape used in plumbing applications is most commonly white, but it is also available in various colors. White PTFE is single density, yellow is double and pink is triple . It is often used to correspond to color coded pipelines (US, Canada, Australia and New Zealand: yellow for natural gas, green for oxygen, etc.). These color-codes for thread sealing tape were introduced by Bill Bentley of Unasco Pty Ltd in the 1970s. In the UK, tape is used from coloured reels, e.g. yellow reels for gas, green for potable water.
- White – used on NPT threads up to 3/8 inch
- Yellow – used on NPT threads 1/2 inch to 2 inch, often labeled "gas tape"
- Pink – used on NPT threads 1/2 inch to 2 inch
- Green – oil-free PTFE used on oxygen lines and some specific medical gasses
- Gray – contains nickel, anti-seizing, anti-gailling and anti-corrosion, used for stainless pipes
- Copper – contains copper granules and is certified as a thread lubricant but not a sealer
Thread tape is appropriate for use on tapered threads, where the sealing force is a wedge action. Parallel threads may not seal effectively with or without tape, as they are intended to be sealed by a gasket.
PTFE tape is also commonly used in the stretching of body piercings, through a process known as taping, because it is inert and safe for this use. The wearer wraps layers of the tape around a plug, slowly increasing the size and thus slowly increasing the size (gauge) of the piercing.
Overuse or misapplication of thread tape may be a hazard. Excess application of PTFE tape can prevent mating threads from fully engaging, reducing the shear point of the threads. Combining thread-seal tape with a pipe dope compound can also overload threads. Also, internal overhangs of loose material may constrict a joint or slough off and form a foreign body that could jam a valve seat. Therefore, use of PTFE tape as a thread sealant is generally not considered appropriate in fluid power (hydraulic) systems.
Familiarity with the Teflon brand of fluoropolymers has led to the practice of erroneously referring to PTFE-based thread seal tape as "Teflon tape". DuPont, owners of the Teflon trademark, no longer manufactures any thread seal tape, and the company has launched a campaign against the practice.
The term "plumber's tape" has been applied to thread seal tape in recent years. In the plumbing trade, plumber's tape is the name given to a strap of material with holes in it used for supporting pipes and fixtures.
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