Thread seal tape
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The low friction of PTFE allows the tape to be used as a lubricant in tapered pipe threads, which more easily allows them to be screwed together to the point of deformation, thus creating the seal.
Typically the tape is wrapped around a pipe's thread three times before it is screwed into place. It is commonly used commercially in such applications as 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
- 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 errently referring to PTFE-based thread seal tape as "Teflon tape". DuPont, owners of the Teflon trademark, does not manufacture thread seal tape, and the company has launched a campaign against the practice.
- "MIL-T-27730A, 15 Apr 1964, and Notice 1, 17 Jul 1994, and Notice2, 9 Feb 1998" (PDF). United States Government Services Administration (GSA), via National Institute of Building Sciences, Whole Building Design Guide (WBDG), . 1998.
- "A-A-58092, 7 Jan 1997" (PDF). United States Government Services Administration (GSA), via National Institute of Building Sciences, Whole Building Design Guide (WBDG), . 1998.
- BS-7786:2006 Specification for unsintered PTFE tapes for general use
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- Hedrick, Dale. "Ear Lobe Stretching FAQ". Onetribe. Retrieved 9 November 2010.
- Real Teflon Brand DuPont