1、BRITISH STANDARD BS 7873:1996 Incorporating Amendment No. 1 Code of practice for application and testing of hot enamel external and/or internal coating of iron and steel pipes ICS 23.040.10; 25.220.50 BS 7873:1996 This British Standard, having been prepared under the direction of the Engineering Sec
2、tor Board, was published under the authority of the Standards Board and comes into effect on 15 November 1996 BSI 14 October 2002 The following BSI references relate to the work on this standard: Committee reference ISE/16 Draft for comment 95/702658 DC ISBN 0 580 26265 0 Committees responsible for
3、this British Standard The preparation of this British Standard was entrusted to Technical Committee ISE/16, Protective coatings and linings of metal pipes and fittings, upon which the following bodies were represented: Adhesive Tape Manufacturers Association British Coatings Federation Ltd. British
4、Foundry Association British Gas PLC British Iron and Steel Producers Association British Plastics Association Ductile Iron Pipe Committee Ductile Iron Producers Association Galvanizers Association Institute of Corrosion Institute of Materials Large Diameter Steel Tube Association Pipeline Protection
5、 Association Society of British Water Industries Society of Chemical Industry Water Services Association of England and Wales The following bodies were also represented in the drafting of the standard, through subcommittees and panels: London Chamber of Commerce Incorporated Low Temperature Coal Dis
6、tillers Association of Great Britain Ltd. Pipeline Industries Guild Amendments issued since publication Amd. No. Date Comments 13844 14 October 2002 See forewordBS 7873:1996 BSI 14 October 2002 i Contents Page Committees responsible Inside front cover Foreword ii 1S c o p e 1 2 Normative references
7、1 3T e r m s a n d d e f i n i t i o n s 1 4G e n e r a l 1 5 Cleaning of pipes 1 6 Surface preparation 1 7P r i m i n g 2 8 Storage, preparation and testing of enamel and primer 2 9 Application of internal enamel lining 3 10 Application of external enamel coating and wraps 3 11 Solar protection 3 1
8、2 Inspection and testing 3 13 Repairs 4 14 Handling and storage of coated/lined pipes 4 15 Fittings and specials 5BS 7873:1996 ii BSI 14 October 2002 Foreword This British Standard has been prepared by Technical Committee ISE/16, Protective coatings and linings of metal pipes and fittings. It has be
9、en considered appropriate to develop a code of practice for the application of the type of coating materials specified in BS 4147 and BS 4164. As a code of practice, this British Standard takes the form of guidance and recommendations. It should not be quoted as if it were a specification and partic
10、ular care should be taken to ensure that claims of compliance are not misleading. The start and finish of text introduced or altered by amendment is indicated in the text by tags . Tags indicating changes to text carry the number of the amendment. For example, text altered by amendment no. 1 is indi
11、cated by . 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 does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover,
12、 an inside front cover, pages i and ii, pages 1 to 5 and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued.BS 7873:1996 BSI 14 October 2002 1 1 Scope This British Standard gives recommendations for the procedures to be followed for the exte
13、rnal and internal application of hot applied coal tar enamel or bitumen enamel coatings, including reinforcements, which are used to protect buried or submerged iron and steel pipes and fittings against corrosion. 2 Normative references The following referenced documents are indispensable for the ap
14、plication 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 4147:1980, Specification for bitumen-based hot-applied coating materials for protecting iron and steel, inclu
15、ding suitable primers where required. BS 4164:1987, Specification for coal-tar-based hot-applied coating materials for protecting iron and steel, including a suitable primer. BS 7079-0, Preparation of steel substrates before application of paints and related products Introduction. BS EN ISO 8501-1:2
16、001, Preparation of steel substrates before application of paints and related products Visual assessment of surface cleanliness Part 1: Rust grades and preparation grades of uncoated steel substrates and of steel substrates after overall removal of previous coatings. 3 Terms and definitions For the
17、purposes of this British Standard the definitions given in BS 4147, BS 4164 and BS 7079-0:1990 apply together with the following. lining the protective coating of film on the internal pipe surface 4 General At every stage of surface preparation and coating/lining, pipes and fittings should be protec
18、ted from contamination, damage and adverse weather conditions. Before production coating commences, a detailed coating procedure should be prepared by the applicator and approved by the client which should include full details of all activities and should cover as a minimum the following: a) handlin
19、g, storage and inspection at all stages of production (see clauses 11, 14 and 15); b) process and coating materials receipt, documentation, storage, testing and control; c) surface preparation; consumables and equipment (see 15.2 and clause 6); d) coating application equipment and operation (see 15.
20、2 and clause 10); e) inspection and testing; frequency and acceptance criteria (see 15.2 and clauses 6, 8, 9, 12 and 13); f) coating repair procedures, materials and coating stripping (see clause 13); g) quality control procedures, including methods of record keeping and batch identification; h) exp
21、erience and qualifications of supervisory, production and quality control personnel, and their permanent deployment for all aspects of the work. 5 Cleaning of pipes All traces of oil, grease and other contaminants should be removed prior to further processing. 6 Surface preparation The surfaces to b
22、e coated should be completely dry during the blasting process and should be maintained in an environment such that the steel temperature is a minimum of 3 C above the dew point with a maximum relative humidity of 80 % r.h. The total external surface of the pipes should be blast cleaned to grade Sa2
23、of BS EN ISO 8501-1:2001 using approved equipment and consumables (see clause 4). The abrasive should be dry and free from contaminants. The type and size of abrasive employed should be selected to give a surface profile of 75 microns 25 microns .BS 7873:1996 2 BSI 14 October 2002 All blast cleaned
24、surfaces should be visually inspected for surface irregularities such as weld spatter, slivers, laminations or hackles which would impair the application or performance of the finished coating. Coatings should not be applied to pipes exhibiting such imperfections and remedial action for pipes showin
25、g these imperfections should be agreed between client and applicator (see clause 4). Any grinding of pipe should not reduce the wall thickness below that specified by the client. Individual ground areas should be reblasted unless otherwise agreed with the client (see clause 4). 7 Priming Cleaned sur
26、faces should be kept dry and free from grease, oil or any other contamination. After blast cleaning no further use of solvents or washes should be permitted without specific approval by the client. Dust or foreign matter should be removed from the cleaned surface by an industrial vacuum cleaner or a
27、 clean dry jet of air. Blast cleaned surfaces should be primed immediately. Under no circumstances should the pipes be primed more than 4 h after blast cleaning nor if any visible rusting occurs. Any pipes that have deteriorated and do not conform to grade Sa2 of BS EN ISO 8501-1:2001 should be rebl
28、asted. The surfaces to be primed should be completely dry and maintained in an environment such that the steel temperature is a minimum of 3 C above the dew point with a maximum relative humidity of 80 % r.h. The primer should be thoroughly mixed to a smooth and uniform consistency before use. Store
29、d primer that has deteriorated beyond the limits specified in BS 4164 or BS 4147 should not be used. The primer should be applied as a thin uniform coating covering the external surface of the pipe without runs, sags or discontinuities. The thickness or coverage of the primer coat and drying times s
30、hould be in accordance with the primer manufacturers recommendations. All primed pipes which do not meet the requirements of this Code of Practice (see 12.4) should be stripped, reblasted and then reprimed. NOTE Small areas may be cleaned and/or reprimed by a method recommended by the primer manufac
31、turer. 8 Storage, preparation and testing of enamel and primer 8.1 General The enamel should be heated in kettles fitted with mechanical stirrers providing continuous agitation of the enamel, and accurate, easily readable recording thermometers, which extend to within 100 mm of the bottom of the ket
32、tle. The thermometers should be calibrated and maintained in good working order. NOTE Bulk deliveries of molten enamel may be transferred directly to the kettles. Solid enamel should be broken up into small pieces, not exceeding 10 kg, in a suitable place free from contamination. Initially the heat
33、should be applied on a low setting until there is a quantity of molten enamel in the kettle bottom. Thereafter the setting may be increased. Whilst the enamel is molten it should be stirred and the lid of the kettle kept firmly closed, unless to withdraw molten enamel or to add fresh material. The q
34、uantity of enamel remaining in the kettle which may be reheated should never exceed 10 % of the fresh loading. The enamel should be heated to the manufacturers recommended application temperature and should not be held for a longer period than that recommended by the manufacturer. Enamel that has be
35、en heated in excess of the manufacturers maximum recommended temperature or held at application temperature for over 6 h should be tested for softening point and penetration which should conform to BS 4164 or BS 4147. Further tests should be conducted at regular intervals, agreed between the applica
36、tor and client, to confirm that the material continues to conform to BS 4164 or BS 4147, otherwise it should be rejected and discarded (see clause 4). All application kettles should be equipped with screens to exclude particles of foreign matter or other materials that may cause coating flaws. Kettl
37、es should be emptied when changing grades of enamel and cleaned when changing types of enamel (e.g. coal tar to asphalt) or when build up of residual material on the screens indicates loss of efficiency. The residual material removed from the kettles during cleaning should not be blended with other
38、enamel but should be discarded.BS 7873:1996 BSI 14 October 2002 3 8.2 Enamel and primer testing The applicator should acquire documentation from the supplier to show that all batches of the supplied materials conform to the required specification. The applicator should have the required test equipme
39、nt and trained staff to measure the viscosity of the primer and softening point and penetration of the enamel. These tests should be conducted at agreed intervals with the client (see clause 4). 9 Application of internal enamel lining The application of the enamel to the inside surface of all pipe o
40、ther than specials should be by centrifugal casting using suitable purpose built plant. During application of enamel the pipe should be rotated so as to produce a smooth, glossy lining of uniform thickness. The enamel lining should be free from wrinkles, sags, blisters or blowholes. The thickness of
41、 lining and tolerance should be agreed between the applicator and the client before application (see clause 4). The enamel lining should be allowed to harden sufficiently before further processing. 10 Application of external enamel coating and wraps Coat and wrap application should follow priming wi
42、thin the time limit recommended by the manufacturer, and the primer should be dry and free from surface contamination prior to enamel application. Typically the enamel should be applied by flood coating with equipment for spirally wrapping the inner wrap(s) and outer wrap under controlled tension us
43、ing trained operators. Such equipment should be approved prior to commencement between applicator and client (see clause 4). The flood coat of enamel should have the inner wrap(s) pulled in and the outer wrap pulled on immediately following flood coating. The inner wrap(s) should not touch the surfa
44、ce of the pipe and should be embedded in the middle third of the enamel thickness. If two inner wraps are required they should be separated at spacings to be specified by the client. The outer wrap should be pulled onto the enamel well bonded with some bleed through of enamel occurring. Wraps should
45、 be wrinkle-free with minimum overlap of 12 mm in all cases. The enamel should be applied at a temperature in accordance with the manufacturers recommendations. The enamel should flow evenly onto the pipe and be free from any solid particles which may cause irregularities in flow. The coating should
46、 be cut back where necessary to meet the specification. The method of removal of cut-back should be approved between applicator and client prior to commencement. 11 Solar protection When specified, solar protection should be applied to the coated pipe prior to stockpiling (see clause 4). It should b
47、e light in colour, water resistant and should cover the coating sufficiently to form an effective barrier to solar radiation. Surplus solar reflective coating should be removed from the uncoated ends of the pipe. 12 Inspection and testing 12.1 General Only trained personnel should be deployed to per
48、form the inspection and testing referred to in clause 4. Unprocessed pipe should be visually inspected for conformance to clause 5. 12.2 Plant conditions The following information should be recorded at intervals agreed with the client so that it can be related to each batch of pipes processed (see c
49、lause 4): surface temperature of steel; ambient temperature; relative humidity; dew point.BS 7873:1996 4 BSI 14 October 2002 12.3 Abrasive inspection Examination of the abrasive should be performed, at intervals agreed between the applicator and client, to ensure that only uncontaminated materials with acceptable size distribution are used in compliance with clause 6 (see also clause 4). 12.4 Surface inspection The first pipe in each production run and
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