1、BRITISH STANDARD BS 4508-1: 1986 Incorporating Amendment No. 1 Thermally insulated underground pipelines Part 1: Specification for steel cased systems with air gap UDC 66.026 + 697.34:697.334:621.644.2:662.998BS4508-1:1986 This British Standard, having been prepared under the directionof the Refrige
2、ration, Heating and Air Conditioning Standards Committee, was published under the authority ofthe Board of BSI and comes intoeffect on 30 May 1986 BSI 10-1999 First published October 1969 First revision May 1986 The following BSI references relate to the work on this standard: Committee reference RH
3、E/9 Draft for comment 84/78101 DC ISBN 0 580 15025 9 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Refrigeration, Heating and Air Conditioning Standards Committee (RHE/-) to Technical Committee RHE/9, upon which the following bodies we
4、re represented: The following bodies were also represented in the drafting of the standard, through subcommittees and panels: British Ceramic Research Association Eurisol (UK) Association of Manufacturers of British Gas Corporation Mineral Insulation Fibres Chartered Institution of Building Services
5、 Gypsum Products Development Association Engineers Institution of Gas Engineers Combustion Engineering Association Phenolic Foam Manufacturers Association Cranfield Institute of Technology Refrigeration Industry Board Department of Health and Social Security Royal Institute of British Architects Dep
6、artment of the Environment (Building Structural Insulation Association Research Establishment) Thermal Insulation Manufacturers and Department of Trade and Industry (National Suppliers Association (TIMSA) Physical Laboratory) Thermal Insulations Contractors Association Electricity Supply Industry in
7、 England and Water-tube Boilermakers Association Wales Engineering Equipment and Materials Users Association Associated Offices Technical Committee Department of the Environment (Property British Rigid Urethane Foam Manufacturers Services Agency) Association National Coal Board British Steel Industr
8、y Pipeline Industries Guild Combined Heat and Power Association Pre-Insulated Mains Contractors Association (PMCA) Amendments issued since publication Amd. No. Date of issue Comments 7727 July 1993 Indicated by a sideline in the marginBS4508-1:1986 BSI 10-1999 i Contents Page Committees responsible
9、Inside front cover Foreword ii 1 Scope 1 2 Definitions 1 3 Information to be supplied by the purchaser 1 4 Information to be supplied by the manufacturer 2 5 Insulated pipe assembly 2 6 Access chambers 3 7 Design and installation of the pipe system 4 8 Field tests 5 9 Fault monitoring 5 Appendix A T
10、hickness of insulation and temperature limitations 7 Appendix B Continuous monitoring for fault conditions 8 Appendix C Location of the leakage source 8 Appendix D Guarantee and insurance arrangements 9 Appendix E Method of test for the bond strength of the coating 9 Table 1 Specified minimum pipe w
11、all thickness 2 Table 2 Soil thermal conductivity and moisture values 8 Publications referred to 10BS4508-1:1986 ii BSI 10-1999 Foreword This revision of this Part of BS 4508 has been prepared under the direction of the Refrigeration, Heating and Air Conditioning Standards Committee and is one of a
12、series specifying requirements for thermally insulated underground piping systems for conveying or circulating steam, hot or chilled water, heated oil and other fluids. The series does not include systems that employ a high vacuum in the annulus as the sole means of insulation. This Part of BS 4508
13、deals with pipe-in-pipe systems having a welded steel outer casing and air gap between the casing and the insulated service pipe. As such the system is suitable for fluids of all temperatures above5 C, including high temperature hot water and steam, and should withstand the effects of ground, surfac
14、e and flood water, which is often aggressive and usually under some pressure due to hydraulic flow or static head. When first published in 1969, this Part of BS4508 included an appendix which described tests for identifying whether a site could be considered as Class A (wet) or Class B (dry). Howeve
15、r, it is no longer considered practical to classify any site as other than wet and these tests were deleted from the standard by amendment. Experience gained since 1969 has enabled the requirements to be specified in greater detail but the standard of workmanship, particularly for field installation
16、 work, is of paramount importance. The revised layout of this Part of BS4508 should assist in separating the responsibilities of the manufacturer of the pipework and equipment from those of the installation contractor. This Part supersedes BS4508-1:1969, which is withdrawn. Other published Parts of
17、BS4508 are as follows: Part 3: General requirements for cased systems without air gap; Part 4: Specific testing and inspection requirements for cased systems without air gap. This Part and BS4508-3 and BS4508-4 should be used in conjunction with CP3009, which gives guidance on the method of selectin
18、g the most suitable system for particular applications. The installation of pipelines is covered in CP2010 and other relevant information may be found in CP413 and BS5970. The system described in this Part of BS4508 utilizes established techniques that are the culmination of several decades of devel
19、opment through field trials and extensive operational experience by major authorities and other users. However, if a fault condition arises, it should be notified to the Installer/Guarantor and rectified at the earliest opportunity in order to prevent deterioration of the system, including the exter
20、nal protective coating. Partial failure due to damp insulation can result in continuous and expensive fuel wastage and other severe penalties and it should be noted that an air gap provides built-in facilities for routine testing. If required, the air gap may be sealed and a positive or negative dry
21、 air pressure, or nitrogen pressure, applied to indicate ingress of ground water. Particular attention is drawn to the need for cathodic protection of piping systems, unless otherwise indicated (see7.4). It is expected that the British Standard Registered Firms Scheme will be extended to include fir
22、ms engaged in underground pipeline schemes.BS4508-1:1986 BSI 10-1999 iii A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer i
23、mmunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi to iv, pages1to10, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the
24、amendment table on the inside front cover.iv blankBS4508-1:1986 BSI 10-1999 1 1 Scope This Part of BS4508 specifies requirements for the design, materials, construction, installation, testing and fault monitoring of thermally insulated underground piping systems using a steel casing enclosing an ins
25、ulated service pipe and incorporating an air gap, suitable for conveying fluids at temperatures exceeding5 C. In addition to the definitive requirements given, it also requires the items detailed in clause3 to be documented. NOTEThe titles of the publications referred to in this Part of BS4508 are l
26、isted on page 10. 2 Definitions For the purposes of this Part of BS 4508 the following definitions apply. 2.1 pipe-in-pipe a pipe assembly consisting of an insulated service pipe or pipes encased in a pressure-tight casing of suitable material. The assembly may or may not incorporate an air gap betw
27、een the insulation and the outer casing 2.2 air gap an annular space between the service pipe insulation and the casing of a pipe-in-pipe assembly 2.3 duct an enclosure provided for the distribution of services 2.4 holiday a hole or flaw in the continuity of a protective coating 2.5 fault monitoring
28、 a regime of inspection or examination to detect the presence of liquid in the outer casing or the access chambers of an installed system 2.6 fault monitoring system a means of carrying out monitoring on a continuous automatic basis using sensing devices which may be interconnected in groups or conn
29、ected to a single central source NOTEFault monitoring systems may be provided with alarm arrangements to signal automatically the presence of a fault condition. 2.7 access chamber an enclosure to house isolating valves and other items of equipment associated with thermally insulated underground pipi
30、ng systems, and to provide adequate and safe access for operation and maintenance of the equipment housed 2.8 ground water water occurring naturally in the ground 2.9 surface water water from the ground surface, paved areas and roofs 3 Information to be supplied by the purchaser 3.1 General The purc
31、haser shall state the following in his enquiry and order: a) the type of fluid to be carried in the service pipe and the design temperature and pressure (see7.1); b) the thickness of the thermal insulation required or the maximum casing temperature (see5.4.3 andAppendix A); c) whether the insertion
32、of control cables in the casing is required (see5.7); d) whether leak detection and location equipment is required (see5.8); e) whether continuous fault monitoring is required (see clause9 andAppendix B); f) the particular requirements of the authority with respect to access chambers (see note1 in c
33、lause6); g) particular requirements for surface temperatures in access chambers where these are to be lower than those recommended in BS4086 (see7.12); h) the requirements for weld testing at the works and in the field, e.g. radiographic, other types of non-destructive testing or visual inspection (
34、see5.1.3 and8.1.1); i) whether or not a guarantee is required (seeAppendix D). 3.2 Options Certain options, that the purchaser may also specify, are permitted by this specification. Where no such options are specified, the following shall be at the discretion of the manufacturer: a) the British Stan
35、dard with which the material of the service pipe shall comply (see5.1.1):BS4508-1:1986 2 BSI 10-1999 b) general details of the cover above the pipe with particular reference to road crossings (see5.2.1); c) the grade required for the type2 material in accordance with BS4147 or BS4164 for external co
36、atings for casings and access chambers (see5.2.3 and6.2); d) the working space in the access chamber where more than one person is needed for operation and maintenance functions, i.e. the number of persons and the location/nature of the necessary functions (see6.1); e) the location of any casing dra
37、inage points in addition to those provided in access chambers (see7.3); f) location and type of provision for temperature measurement (see7.13); g) location and type of provision for the measurement of volume flow rate, e.g. venturi units, orifice plates, pressure-tapped valves, etc. (see7.14). 4 In
38、formation to be supplied by the manufacturer The manufacturer shall state the following in his tender and quotation: a) the protective treatment offered for the internal surface of the casing (see5.2.2); b) detailed instructions for the handling, stacking and storage of prefabricated pipe sections (
39、to be provided at the time of delivery of the product) (see5.6); c) a statement of the need for cathodic protection where the manufacturer has been instructed to conduct a soil survey (see7.4); d) the allowable drop in pressure throughout the system when tested by the method given in8.2.2. 5 Insulat
40、ed pipe assembly 5.1 Service pipe 5.1.1 Material. Steel pipes shall comply with BS1387, BS3601 or BS3602, as appropriate see3.2 a). Copper pipes shall comply with BS2871-1. 5.1.2 Finish. The internal surface of service pipe sections shall be clean and free from foreign matter. The external surface s
41、hall be suitably prepared,e.g. by power wire brushing, before the application of any coating or insulation. 5.1.3 Welded joints. All welded joints in the service pipe that would be rendered inaccessible by subsequent assembly shall be examined visually, or by non-destructive testing, in accordance w
42、ith BS2640 or BS2971 as appropriate, prior to the assembly of the service pipe with the casing. 5.2 Casing 5.2.1 Material. The casing shall be seamless or welded steel pipe complying with grade410 of BS3601 with a specified minimum wall thickness as given inTable 1. Table 1 Specified minimum pipe wa
43、ll thickness NOTEThese wall thicknesses assume that there will be not less than500mm cover above the pipe generally, and not less than600mm cover under roads see3.2 b). Where the outer casing is used for prestressing or for the transfer of stresses to the ground, calculations shall be made to substa
44、ntiate that the wall thickness of the outer casing is adequate. No account shall be taken in the calculations for bracing provided by non-structural pipe supports. 5.2.2 Internal finish. A suitable protective treatment shall be applied to the internal surface of the casing to inhibit rusting before
45、assembly. NOTESee DD24 for recommended methods of protection against corrosion. See also clause4 a). 5.2.3 External coating. The external surface of the casing shall be protected by hot applied coating material in accordance with BS4147 or BS4164, using the appropriate grade of type2 material see3.2
46、 c). The coating shall include the primer and a flood coat of the coating material applied in accordance with CP2010, BS5493 and the manufacturers instructions. Before the flood coat is applied the primer shall be dry. Inner and outer wrapping of non-woven glass fibre tissue shall be applied simulta
47、neously to the flood coat of coating material. The inner wrap shall have a minimum mass of42g/m 2 , a minimum thickness of0.25mm and a longitudinal tensile strength of306N for a sheet width of150mm. The outer wrap shall be saturated with the coating material and have a minimum mass of460g/m 2 , a mi
48、nimum thickness of0.60mm and a longitudinal tensile strength of not less than535N for a sheet width of150mm. Nominal size Specified minimum wall thickness mm mm 150 to 450 500 to 650 700 and above 3.2 5.0 5.9BS4508-1:1986 BSI 10-1999 3 Both wraps shall be spirally wound with a minimum overlap of25mm
49、. The finished external coating shall have an average thickness of not less than4mm with an absolute minimum thickness at any point of2.4mm and an absolute maximum thickness of7mm. The completed external coating shall be well bonded to the casing material, uniform, smooth and free from holidays and shall be trimmed off150mm from the ends of each casing section and bevelled throughout its thickness over a minimum length of25mm. NOTE 1When a measurement of the average coating thickness is required, it should be determined by non-destructive means with a mi
