Thread seal tape
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Thread seal tape can be used in many ways, the most common of which is to seal pipe threads. Also known as plumber's tape, PTFE tape, tape dope, or popularly but incorrectly as Teflon (A Dupont trade name) tape.
In use, the tape is wrapped around the exposed threads of a pipe before it is screwed into place. The tape is commonly used commercially in pressurized water systems, such as central heating systems, as well as in air compression equipment and thread joints with coarse threads. One of the defining characteristics of PTFE is how good it is at defeating friction. The use of PTFE tape in tapered pipe threads performs a lubricating function, which more easily allows the threads to be screwed together, to the point of deformation, which is what creates the seal.
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.
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 is most commonly found in the color white and is used in plumbing applications, but it is also available in various colors. White PTFE is single density, yellow is double density and pink is triple density. 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
Familiarity with the Teflon brand of fluoropolymers has led to the practice of referring to PTFE-based thread seal tape as "Teflon tape". DuPont, owners of the Teflon brand, does not manufacture thread seal tape, and the company has launched a campaign against the practice.
Over-use, or mis-application of thread tape may be a hazard. An excess amount of tape can prevent mating threads from fully engaging, therefore reducing the shear point of the threads. The use of thread-seal tape in addition to a pipe dope compound can also be dangerous, because it can become too much between the flanks of the threads. As the tape material is so soft, excess or overhangs may easily break off and form a foreign body contaminant that could jam a valve seat etc.
- Hedrick, Dale. "Ear Lobe Stretching FAQ". Onetribe. Retrieved 9 November 2010.
- "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
- Real Teflon Brand DuPont
- "Thred Taper, automatic tape application machine".
- Assembly magazine. 1 June 2000.
- "Automated teflon-tape wrapping". Machine Design. April, 2002.