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1、BS 7786:2006 Specification for unsintered PTFE tapes for general use ICS 83.140.99 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BRITISH STANDARD Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 14:39:02 GMT+00:00 2006, Uncontrolled Copy,
2、 (c) BSI Publishing and copyright information The BSI copyright notice displayed in this document indicates when the document was last issued. BSI 2006 ISBN 0 580 48936 1 The following BSI references relate to the work on this standard: Committee reference PSE/2 Draft for comment 06/30143310 DC Publ
3、ication history First published as BS 4375, December 1968 First published as BS 7786, June 1995 Second (present) edition, August 2006 Amendments issued since publication Amd. no.DateText affected BS 7786:2006 Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 14:39
4、:02 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BSI 2006i BS 7786:2006 Contents Foreword ii 1Scope 1 2Normative references 1 3Information and requirements to be agreed and documented 2 4Composition 3 5Appearance and finish 4 6Tape grades 4 7Tape dimensions 4 8Sealing 5 9Thread wrapping 5 10Sampling 5
5、 11Packaging and marking 6 Annexes Annex A (normative) Determination of residual lubricant content 7 Annex B (informative) Explanatory note on tape grades 8 Annex C (normative) Determination of mass per unit area 11 Annex D (normative) Measurement of tape dimensions 12 Annex E (normative) Thread wra
6、pping test 13 Bibliography 14 List of figures Figure B.1 Mass per unit area/density/thickness relationships 10 Figure E.1 Thread wrapping test 13 List of tables Table 1 Tape grades 4 Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 14, an insi
7、de back cover and a back cover. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 14:39:02 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7786:2006 ii BSI 2006 Foreword Publishing information This British Standard was published by BSI and came into effect on 31 Aug
8、ust 2006. It was prepared by Technical Committee PSE/2, Jointing materials and compounds. A list of organizations represented on this committee can be obtained on request to its secretary. Supersession This British Standard supersedes BS 7786:1995, which is withdrawn. Relationship with other publica
9、tions There are two standards covering unsintered PTFE tapes. This British Standard specifies requirements for tapes for general use at a wide range of temperatures. BS EN 751-3 specifies requirements for tapes for use in very specific circumstances at a more limited range of temperatures. Informati
10、on about this document This is a full revision of the standard. The principal change has been to make all unsintered PTFE tapes manufactured in accordance with BS 7786 suitable for use with an oxygen-enriched environment. Hazard warnings Presentational conventions The provisions of this standard are
11、 presented in roman (i.e. upright) type. Its requirements are expressed in sentences in which the principal auxiliary verb is “shall”. Commentary, explanation and general informative material is presented in smaller italic type, and does not constitute a normative element. Contractural and legal con
12、siderations This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard cannot confer immunity from legal obligations. WARNING. When heated to temperatures above 260 C, PTFE will begin
13、to degrade and the rate of degradation will increase with increasing temperature. The gases produced during degradation will vary according to the temperature and other conditions but will invariably contain toxic components. Where accidental or unavoidable exposure of PTFE to heat and/or flame occu
14、rs, 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 adequate precautions are not taken. It refers only to the technical suitability and does not absolve the user from legal obligations relati
15、ng to health and safety at any stage. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 14:39:02 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BSI 20061 BS 7786:2006 1 Scope This British Standard specifies requirements for unsintered polytetrafluoroethylene (PTFE) ta
16、pes with a mass per unit area within the range 25 g/m2 to 300 g/m2 and 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 ta
17、pe are suitable 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 docum
18、ented items have to be satisfied. 2 Normative references The 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) a
19、pplies. BS 21, 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 joints BS 1752, Specification for laboratory sintered or fritted filters including porosity
20、 grading BS 2071:1989, Specification for Soxhlet extractors BS 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: Specification BS EN ISO 4797:2004, Laboratory glassware Boiling fla
21、sks with conical ground joints BS EN ISO 12086-1:2006, Plastics Fluoropolymer dispersions and moulding and extrusion materials Part 1: Designation system and basis for specifications ASTM D4591, Standard test method for determining temperatures and heats of transitions of fluoropolymers by different
22、ial scanning calorimetry Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 14:39:02 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7786:2006 2 BSI 2006 3 Information and requirements to be agreed and documented 3.1Information to be supplied by the purchaser The inf
23、ormation to be supplied by the purchaser shall be fully documented. Both the definitive requirements specified throughout the standard and the following documented items shall be satisfied before a claim of compliance with the standard can be made and verified: a)the grade and thickness of tape chos
24、en; b)the intended application for the PTFE tape, including any relevant British, European or international application standards; NOTE 1 Some specific applications 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
25、 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 product and temperature). In specialist applications, PTFE tapes have been satisfactorily used for sealing against pressures exceeding 3
26、00 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 contact with, potable water. 3.2Items for agreement The following items to be agreed between the contracting parties, which are specified
27、in the clauses referred to, shall be fully documented. Both the definitive requirements specified throughout the standard and the following documented items shall be satisfied before a claim of compliance can be made: a)where no specific application standard exists, the grade, thickness and density
28、required to form a leak-free joint for the intended application (see Clause 6, 7.1 and Clause 8); NOTE 1For the purposes of product performance comparisons it might be desirable to select one of the preferred thickness values specified in 7.1. b)if the width differs from that normally supplied, the
29、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 = 105 N/m2 = 100 kPa. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 14:39:02 GMT+00:00 2006, Uncontrolled Copy, (c)
30、 BSI BSI 20063 BS 7786:2006 d)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 2At the request of the user the manufacturer should provide sufficient information on the application and use of the t
31、ape together 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 Composition 4.1 The
32、tape shall 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 ad
33、ded. 4.2 When determined in accordance with Annex A, the residual lubricant content shall not exceed 0.1% by mass. NOTE 1This ensures that the tape is suitable for use in an oxygen- enriched environment. NOTE 2For applications involving either high concentrations or pressures (or both) of liquid or
34、gaseous oxygen, 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,
35、 as evidenced 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
36、 When used under 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. NOTENon-metallic products for installation and use in the United Kingdom which are verified and list
37、ed under the 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
38、 249234. In addition, 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 ob
39、tained from the WRc-NSF Evaluation and Testing Centre. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 14:39:02 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7786:2006 4 BSI 2006 5 Appearance and finish 5.1 When viewed in reflected light the tape shall be white
40、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 grades NOTESee 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
41、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 fall outside the range given for the grade. NOTEThe mass per unit area in each category can be achieved by any combination of thickness and
42、 density commensurate with the appropriate range of values in each category. 7 Tape dimensions 7.1Thickness When determined to an accuracy of 0.002 mm in accordance 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 e
43、qual 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 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). NOT
44、EIt 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 might be mutually exclusive to one or other of the grades. Table 1Tape grades GradeMass per unit area g/m2 Indicative applicationsA) H300
45、to 1501 wrap up to R2 2 wraps R2 R4B) 3 wraps R4 R6B) M150 to 751 wrap up to R3/4 or antiseize only up to R4 2 wraps R3/4 to R1 1/2 3 wraps R1 1/2 to R2 L75 to 251 wrap up to R1/4 or antiseize only up to R2 2 wraps R1/4 to R1/2 3 wraps R1/2 to R1 A) The indicative applications are not requirements b
46、ut 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 consulted. For thread sizes larger than R2, if permitted, a non-penetrant lubricant applied to the surface of the wrapped tape is h
47、ighly beneficial for reduction in tightening torque. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 14:39:02 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BSI 20065 BS 7786:2006 7.2Width When determined to an accuracy of 0.1 mm in accordance with Annex D, the mean
48、 width of 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.
49、3Length When 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. 8 Sealing Any 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 ta
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