1、BS 7786:2006Specification for unsintered PTFE tapes for general useICS 83.140.99NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDPublishing and copyright informationThe BSI copyright notice displayed in this document indicates when the document was last issued. B
2、SI 2006ISBN 0 580 48936 1The following BSI references relate to the work on this standard:Committee reference PSE/2Draft for comment 06/30143310 DCPublication historyFirst published as BS 4375, December 1968First published as BS 7786, June 1995Second (present) edition, August 2006Amendments issued s
3、ince publicationAmd. no. Date Text affectedBS 7786:2006 BSI 2006 iBS 7786:2006ContentsForeword ii1 Scope 12 Normative references 13 Information and requirements to be agreed and documented 24 Composition 35 Appearance and finish 46 Tape grades 47 Tape dimensions 48 Sealing 59 Thread wrapping 510 Sam
4、pling 511 Packaging and marking 6AnnexesAnnex A (normative) Determination of residual lubricant content 7Annex B (informative) Explanatory note on tape grades 8Annex C (normative) Determination of mass per unit area 11Annex D (normative) Measurement of tape dimensions 12Annex E (normative) Thread wr
5、apping test 13Bibliography 14List of figuresFigure B.1 Mass per unit area/density/thickness relationships 10Figure E.1 Thread wrapping test 13List of tablesTable 1 Tape grades 4Summary of pagesThis document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 14, an inside back
6、 cover and a back cover.BS 7786:2006ii BSI 2006ForewordPublishing informationThis British Standard was published by BSI and came into effect on 31 August 2006. It was prepared by Technical Committee PSE/2, Jointing materials and compounds. A list of organizations represented on this committee can be
7、 obtained on request to its secretary.SupersessionThis British Standard supersedes BS 7786:1995, which is withdrawn.Relationship with other publicationsThere are two standards covering unsintered PTFE tapes. This British Standard specifies requirements for tapes for general use at a wide range of te
8、mperatures. BS EN 751-3 specifies requirements for tapes for use in very specific circumstances at a more limited range of temperatures.Information about this documentThis is a full revision of the standard. The principal change has been to make all unsintered PTFE tapes manufactured in accordance w
9、ith BS 7786 suitable for use with an oxygen-enriched environment.Hazard warningsPresentational conventionsThe provisions of this standard are presented in roman (i.e. upright) type. Its requirements are expressed in sentences in which the principal auxiliary verb is “shall”.Commentary, explanation a
10、nd general informative material is presented in smaller italic type, and does not constitute a normative element.Contractural and legal considerationsThis publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application.Compliance
11、with a British Standard cannot confer immunity from legal obligations.WARNING. When heated to temperatures above 260 C, PTFE will begin to degrade and the rate of degradation will increase with increasing temperature. The gases produced during degradation will vary according to the temperature and o
12、ther conditions but will invariably contain toxic components. Where accidental or unavoidable exposure of PTFE to heat and/or flame occurs, good ventilation is therefore essential.WARNING. This British Standard calls for the use of substances and/or procedures that can be injurious to health if adeq
13、uate precautions are not taken. It refers only to the technical suitability and does not absolve the user from legal obligations relating to health and safety at any stage. BSI 2006 1BS 7786:20061 ScopeThis British Standard specifies requirements for unsintered polytetrafluoroethylene (PTFE) tapes w
14、ith a mass per unit area within the range 25 g/m2to 300 g/m2and with a thickness in the range 0.05 mm to 0.25 mm.It specifies requirements for three grades of unsintered PTFE tape, for general or special engineering applications at temperatures between 270 C and +260 C. All grades of this tape are s
15、uitable for use with most common liquids and gases and in an oxygen-enriched environment.In addition to the definitive requirements, this standard also requires the items detailed in Clause 3 to be documented. For compliance with this standard, both the definitive requirements and the documented ite
16、ms have to be satisfied.2 Normative referencesThe following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.BS 2
17、1, Specification for pipe threads for tubes and fittings where pressure-tight joints are made on the threads (metric dimensions)BS 572:1985, Specification for interchangeable conical ground glass jointsBS 1752, Specification for laboratory sintered or fritted filters including porosity gradingBS 207
18、1:1989, Specification for Soxhlet extractorsBS 6920-1, Suitability of non-metallic products for use in contact with water intended for human consumption with regard to their effect on the quality of the water Part 1: SpecificationBS EN ISO 4797:2004, Laboratory glassware Boiling flasks with conical
19、ground jointsBS EN ISO 12086-1:2006, Plastics Fluoropolymer dispersions and moulding and extrusion materials Part 1: Designation system and basis for specificationsASTM D4591, Standard test method for determining temperatures and heats of transitions of fluoropolymers by differential scanning calori
20、metryBS 7786:20062 BSI 20063 Information and requirements to be agreed and documented3.1 Information to be supplied by the purchaserThe information to be supplied by the purchaser shall be fully documented. Both the definitive requirements specified throughout the standard and the following document
21、ed items shall be satisfied before a claim of compliance with the standard can be made and verified:a) the grade and thickness of tape chosen;b) the intended application for the PTFE tape, including any relevant British, European or international application standards;NOTE 1 Some specific applicatio
22、ns are covered in BS EN 751-3.c) the maximum intended working pressure;NOTE 2 The maximum working pressure will depend upon the grade and thickness of the tape, the method of application, the number of wraps, the size and quality of the fittings (threads) and the specific operating environment (flow
23、 product and temperature). In specialist applications, PTFE tapes have been satisfactorily used for sealing against pressures exceeding 300 bar 1)and also for high vacuum applications.d) the width and length of tape chosen;e) whether the tape is to be used in contact with, or likely to be used in co
24、ntact with, potable water.3.2 Items for agreementThe following items to be agreed between the contracting parties, which are specified in the clauses referred to, shall be fully documented. Both the definitive requirements specified throughout the standard and the following documented items shall be
25、 satisfied before a claim of compliance can be made:a) where no specific application standard exists, the grade, thickness and density required to form a leak-free joint for the intended application (see Clause 6, 7.1 and Clause 8);NOTE 1 For the purposes of product performance comparisons it might
26、be desirable to select one of the preferred thickness values specified in 7.1.b) if the width differs from that normally supplied, the width supplied in this case (see 7.2);c) if the length differs from that normally supplied, the length supplied in this case (see 7.3);1)1 bar = 105N/m2= 100 kPa. BS
27、I 2006 3BS 7786:2006d) if the application requires test pressures that differ from those normally applied, the test pressure that will apply in this case (see Clause 8);NOTE 2 At the request of the user the manufacturer should provide sufficient information on the application and use of the tape tog
28、ether with any special measures or techniques that might be needed when the tape is being used under extremes of pressure, temperature or size.e) where no specific application standard exists, the representative thread form used in a thread wrapping test (see Clause 9).4 Composition4.1 The tape shal
29、l be manufactured from a suitable grade of coagulated dispersion PTFE powder which conforms to the designation PTFE-E, PDMIN, 7.1.E.H.4.1.2 as specified in BS EN ISO 12086-1:2006. Filler, plasticizer, colour, reprocessed material, or additives other than processing lubricant shall not be added.4.2 W
30、hen determined in accordance with Annex A, the residual lubricant content shall not exceed 0.1% by mass.NOTE 1 This ensures that the tape is suitable for use in an oxygen-enriched environment.NOTE 2 For applications involving either high concentrations or pressures (or both) of liquid or gaseous oxy
31、gen, either detonation or self-ignition tests (or both) might also be required. If in doubt it is essential that the user consult the oxygen supplier for guidance on these potential hazards.4.3 The conditions during manufacture shall be such that the tape remains in the unsintered state, as evidence
32、d by the absence of a shift or change in peak height of the initial melting peak obtained by differential scanning calorimetry (DSC) when compared with the starting material. The melting endotherm temperature shall be between 340 C and 350 C when tested in accordance with ASTM D4591.4.4 When used un
33、der the conditions for which they are designated, PTFE tapes in contact with, or likely to come into contact with, potable water shall conform to the requirements specified in BS 6920-1.NOTE Non-metallic products for installation and use in the United Kingdom which are verified and listed under the
34、UK Water Regulations Advisory Scheme (WRAS) are deemed to satisfy the requirements of this subclause. Details of the scheme are obtainable from the WRc-NSF Evaluation and Testing Centre, Fern Close, Pen-Y-Fan Industrial Estate, Oakdale, Gwent, NP11 3EH, telephone 01495 248454, fax 01495 249234.In ad
35、dition, products introduced in accordance with Regulation 25 of the Water Supply (Water Quality) Regulations 1989 1 are considered free from adverse health effects for the purposes of conformity to this subclause. A list of substances and products approved under Regulation 25 can be obtained from th
36、e WRc-NSF Evaluation and Testing Centre.BS 7786:20064 BSI 20065 Appearance and finish5.1 When viewed in reflected light the tape shall be white in colour.5.2 The tape shall be free from any edge or surface defects, inclusions, thin patches, tears and holes, when inspected visually.6 Tape gradesNOTE
37、See Annex B for an explanatory note on tape grades.6.1 Tape shall be supplied in one of the grades which are designated in terms of the mass per unit area and identified by the indicated grade letter as given in Table 1.6.2 When determined in accordance with Annex C, the mass per unit area shall not
38、 fall outside the range given for the grade.NOTE The mass per unit area in each category can be achieved by any combination of thickness and density commensurate with the appropriate range of values in each category.7 Tape dimensions7.1 ThicknessWhen determined to an accuracy of 0.002 mm in accordan
39、ce with Annex D at an applied pressure of 10 kPa to 20 kPa, the mean thickness of the tape, based on a minimum of five readings taken at equal distances apart, shall not differ from the declared value by more than 10%. Unless otherwise agreed in accordance with 3.2a), or required by the manufacturer
40、 to ensure specified performance levels, tape shall be supplied in the following thicknesses: 0.075 mm; 0.1 mm; 0.2 mm (see Clause 6).NOTE It might not be possible within the constraints of the grading system to supply all three preferred thicknesses at each grade. Some of the preferred thicknesses
41、might be mutually exclusive to one or other of the grades.Table 1 Tape gradesGrade Mass per unit areag/m2Indicative applicationsA)H 300 to 150 1 wrap up to R22 wraps R2 R4B)3 wraps R4 R6B)M 150 to 75 1 wrap up to R3/4 or antiseize only up to R42 wraps R3/4 to R1 1/23 wraps R1 1/2 to R2L 75 to 25 1 w
42、rap up to R1/4 or antiseize only up to R22 wraps R1/4 to R1/23 wraps R1/2 to R1A)The indicative applications are not requirements but serve as a guide to the applications most suited to the tape. See also Clause 3 for application limits.B)For thread sizes larger than R4 the manufacturer should be co
43、nsulted. For thread sizes larger than R2, if permitted, a non-penetrant lubricant applied to the surface of the wrapped tape is highly beneficial for reduction in tightening torque. BSI 2006 5BS 7786:20067.2 WidthWhen determined to an accuracy of 0.1 mm in accordance with Annex D, the mean width of
44、the tape, based on a minimum of five measurements taken at equal distances apart along the length of the tape, shall not differ from that marked on the spool by more than 0.5 mm. Unless otherwise agreed in accordance with 3.2b), tape shall be supplied in widths of 12 mm, 19 mm or 25 mm.7.3 LengthWhe
45、n determined in a tension free condition to an accuracy of 0.1% in accordance with Annex D, the actual length of tape on the spool shall be not less than that marked on the spool. Unless otherwise agreed in accordance with 3.2c), tape shall be supplied in lengths of 5 m, 10 m, 12 m or 25 m.8SealingA
46、ny sample of tape shall form a leak-free seal when tested in accordance with the relevant British, European or international application standard. In the absence of such a standard, the manufacturer shall supply tape in accordance with 3.2a), that provides a leak-free seal which provides the agreed
47、performance for the intended application when applied to a joint or joints of representative size and thread form. Unless otherwise agreed in accordance with 3.2d), the joint(s) shall be tested at a pressure or vacuum as follows:a) for pressure, 1.5 times the maximum required working pressure; andb)
48、 for vacuum, 1.0 times vacuum, over the expected working temperature range.NOTE The chosen pressure medium may be the actual flow product, or the joint may be exposed to the flow product, or agreed simulant, prior to pressure testing with compressed air or nitrogen gas.9 Thread wrappingWhen tested i
49、n accordance with Annex E, the tape shall not break, or tear or split at the crests of the thread form, and the finishing end of the tape shall remain in position with no tendency to unwind.10 SamplingAll samples of tape used for the tests specified in Clause 4, Clause 5, Clause 8 and Clause 9 shall be taken from a wound spool omitting the first layer or wrapping.BS 7786:20066 BSI 200611 Packaging and marking11.1 Tape shall be wound onto spools that have a close fitting sleeve capable of excluding dust and grit. Sp
