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词条 Thread seal tape
释义

  1. Types

  2. Uses

     Hazards 

  3. Use of names

  4. References

  5. External links

{{Refimprove|date=March 2009}}Thread seal tape (also known as PTFE tape, Teflon tape, or plumber's tape) is a polytetrafluoroethylene (PTFE) film tape commonly used in plumbing for sealing pipe threads. The tape is sold cut to specific widths and wound on a spool, making it easy to wind around pipe threads. Thread seal tape lubricates allowing for a deeper seating of the threads, and it helps prevent the threads from seizing when being unscrewed.[1] 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,[2] and instead making it easier to tighten.[1]

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.

Temperature Range: -450°F to +500°F (-268°C to +260°C). PTFE is completely stable up to +500˚F or +260˚C. Decomposition is slow up to 750°F or 400°C. Decomposition will occur on contact with open flames.

Types

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%.[3] The second standard, A-A-58092,[4] is a commercial grade which maintains the thickness requirement of MIL-T-27730A and adds a minimum density of 1.2 g/cm3.[4] 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. 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 Oxygen.

  • 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, safe for potable water
  • Green: oil-free PTFE used on oxygen lines and some specific medical gasses
  • Gray: contains nickel, anti-seizing, anti-galling and anti-corrosion, used for stainless pipes
  • Copper: contains copper granules and is certified as a thread lubricant but not a sealer

In Europe the BSI standard BS-7786:2006 specifies various grades and quality standards of PTFE thread sealing tape.[5]

Uses

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.

Thread sealing tape is almost always applied by hand, although at least one machine is available for production wrapping of fittings.[6][7][8]

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 a layer of tape around a plug and uses the jewellery, adding another layer every few days, thus gradually stretching the piercing.[9]

Hazards

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.

Use of names

Familiarity with the Teflon brand of fluoropolymers has led to the name becoming a generic trademark, and the practice of PTFE-based thread seal tape to be referred to as "Teflon tape". Chemours, owner of the Teflon trademark, no longer manufacture any thread seal tape,[10] and object [11] to this practice.

Most references to "plumber's tape" nowadays refer to thread seal tape; however, the original use in the plumbing trade describes a strap of material with holes in it used for supporting pipes and fixtures.[12]

References

1. ^1 {{cite book|last=Cauldwell|first=Rex|title=Taunton's Plumbing Complete: Expert Advice from Start to Finish |url=https://books.google.com/books?id=7cIohMo30ssC&pg=PA38|date=Sep 2, 2008|publisher=Taunton Press|page=38}}
2. ^{{cite book|last=Doran|first=David|title=Construction Materials Reference Book |url=https://books.google.com/books?id=4eEpAAAAQBAJ&pg=PA274|date=Jul 24, 2013|publisher=Routledge|isbn=1135139210|page=274}}
3. ^{{cite web |url=http://www.wbdg.org/ccb/FEDMIL/t27730a.pdf |title=MIL-T-27730A, 15 Apr 1964, and Notice 1, 17 Jul 1994, and Notice2, 9 Feb 1998 |year= 1998 |format=PDF |publisher= United States General Services Administration (GSA), via National Institute of Building Sciences |work=Whole Building Design Guide (WBDG)}}
4. ^1 {{cite web |url=http://www.wbdg.org/ccb/FEDMIL/aa58092.pdf |title=A-A-58092, 7 Jan 1997 |year= 1998 |format=PDF |publisher= United States General Services Administration (GSA), via National Institute of Building Sciences |work=Whole Building Design Guide (WBDG)}}
5. ^BS-7786:2006 Specification for unsintered PTFE tapes for general use
6. ^{{cite web |url=http://www.thredtaper.com |title=Thred Taper, automatic tape application machine}}
7. ^{{cite journal |journal=Assembly magazine |date=1 June 2000}}
8. ^{{cite journal |journal=Machine Design |title=Automated teflon-tape wrapping |date=April 2002}}
9. ^{{cite web|last=Hedrick|first=Dale|title=Ear Lobe Stretching FAQ|url=http://onetribe.nu/catalog/stretching.php|archiveurl=https://web.archive.org/web/20090225195604/http://www.onetribe.nu:80/catalog/stretching.php|archivedate=25 February 2009|publisher=Onetribe|accessdate=9 November 2010}}
10. ^{{cite web|url=https://www.chemours.com/Teflon_Industrial/en_US/history_plumber_tape.html|title=History of Plumber's Tape |publisher=Chemours |accessdate=2016-03-21}}
11. ^[https://www.chemours.com/Teflon_Industrial/en_US/real_teflon_brand.html Real Teflon Brand ]
12. ^{{cite web |url=http://www.downwindmarine.com/Plumbers-Tape-Galvanized-p-91000989.html|archiveurl=https://web.archive.org/web/20180426104326/http://www.downwindmarine.com/Plumbers-Tape-Galvanized-p-91000989.html|archivedate=2 April 2018|deadurl=no |title=Pipe Fitting Accessories - Plumbing & Sanitation - Plumber's Tape - Galvanized|website=Downwind Marine|date= |author= |accessdate= 28 December 2018}} Example of the original strapping "plumber's tape".

External links

  • {{Commons category-inline|Thread seal tape}}

2 : Dry lubricants|Plumbing
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