1、BRITISH STANDARD BS 7523:1991 Specification for Preformed cellular polyethylene (PE) materials for the thermal insulation of pipeworkBS7523:1991 This British Standard, having been prepared under the directionof the Plastics andRubber Standards Policy Committee, was published underthe authority of th
2、e Standards Board and comes intoeffect on 31 October 1991 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference PRM/72 Draft for comment 88/43770 DC ISBN 0 580 20123 6 Committees responsible for this British Standard The preparation of this British Standar
3、d was entrusted by the Plastics and Rubber Standards Policy Committee (PRM/-) to Technical Committee PRM/72, upon which the following bodies were represented: Association of Building Component Manufacturers Brick Development Association British Board of Agrement British Plastics Federation British R
4、igid Urethane Foam Manufacturers Association Calcium Silicate Brick Association Limited Cavity Foam Bureau Chief and Assistant Chief Fire Officers Association Department of the Environment (Building Research Establishment) Department of the Environment (Construction Directorate) Engineering Equipmen
5、t and Materials Users Association Flat Roofing Contractors Advisory Board Loss Prevention Council Ministry of Defence National Cavity Insulation Association National Federation of Roofing Contractors National House-building Council Phenolic Foam manufacturers Association Polyethylene Foam Insulation
6、 Association Royal Institute of British Architects The following bodies were also represented in the drafting of the standard, through sub-committees and panels: Institute of Plumbing Thermal Insulation Manufacturers and Suppliers Association (TIMSA) Thermal Insulations Contractors Association Amend
7、ments issued since publication Amd. No. Date CommentsBS7523:1991 BSI 10-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Composition 1 3 Types 1 4 Dimensions and tolerances 1 5 Physical properties 1 6 Condition and appearance 1 7 Sampling 1 8 Pipe sections 1 9 M
8、arking 1 Appendix A Factors affecting the thermal conductivity 3 Appendix B Method for the determination of thermal conductivity 3 Appendix C Burning properties of polyethylene (PE) cellular materials 18 Appendix D Notes for designers 19 Figure 1 Guarded end apparatus 8 Figure 2 Calibrated or calcul
9、ated end apparatus 9 Figure 3 Nukiyama correction 16 Table 1 Dimensional tolerances for pipe insulation 1 Table 2 Physical properties 2 Table 3 Symbols and units 5 Publication(s) referred to Inside back coverBS7523:1991 ii BSI 10-1999 Foreword This British Standard has been prepared under the direct
10、ion of the Plastics and Rubber Standards Policy Committee from a draft provided by the British Plastics Federation. In this standard, two types of cellular polyethylene pipe insulation are specified; the materials differ principally in their thermal conductivity. Useful information on the use of the
11、 products has been included, as well as advice concerning their burning characteristics. 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
12、 itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to 20, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will
13、be indicated in the amendment table on the inside front cover.BS7523:1991 BSI 10-1999 1 1 Scope This British Standard specifies the composition, properties and dimensional tolerances for preformed cellular polyethylene (PE) materials for the thermal insulation of pipework. The nominal operating temp
14、erature range for the materials is 40 C to +80 C (see note1). NOTE 1Manufacturers have experienced no detrimental effects at service temperatures up to100 C. Consideration will be given, therefore, to raising the upper service temperature limit at the next revision of this British Standard. NOTE 2Th
15、e titles of the publications referred to in this standard are listed on the inside back cover. 2 Composition The material shall consist of cellular polyethylene with a closed cell structure. NOTEMinor additives, e.g. colouring and fire retarding additives, may also be included with some materials. 3
16、 Types The material shall be divided into two types, A andB, which differ due to their thermal conductivity, type A having the lower thermal conductivity. 4 Dimensions and tolerances 4.1 The bore of a pipe section shall be specified as the nominal outside diameter of the pipe to be insulated. 4.2 Th
17、e wall thickness of the pipe insulation shall be specified as the thickness of insulation along a line at90 to any point on the inside bore of the tubular pipe insulation. 4.3 The tolerances on the dimensions of the product shall be as given inTable 1. 5 Physical properties The physical properties s
18、hall comply with the requirements given inTable 2, when tested in accordance with the methods indicated therein. NOTEFor some test methods, a composite structure in a flat sheet form is required. This structure may, however, contain stress cracks and possible cell deformation and may also require la
19、mination using proprietary adhesives, all of which can adversely affect the results achieved. 6 Condition and appearance The material shall have a uniform fine cell structure. NOTEThe material is normally supplied free from objectionable odour and with a smooth inner and outer surface. 7 Sampling Te
20、st specimens of the same formulation and density as the product shall be used. NOTEWhere it is not possible to cut test specimens from the product, specimens may be moulded to size or cut from larger mouldings. 8 Pipe sections 8.1 Pipe sections shall be supplied as a tube which shall be partially or
21、 completely slit through the wall of the insulation. 8.2 The longitudinally mating faces, if slit completely, shall be flat and in the same plane so that when the two faces are put together no gaps exist between the mating surfaces. 8.3 The ends shall be flat and normal to the longitudinal axis of t
22、he section. Table 1 Dimensional tolerances for pipeinsulation 9 Marking The product shall be marked or labelled with at least the following information: a) the manufacturers name or trade mark; b) the product type (see clause3); c) the number and data of this British Standard, i.e. BS7523:1991 1) .
23、NOTEIt is preferred that the marking takes the following form: “BS 7523:1991:A”. Dimension Permissible deviation Minimum Maximum mm mm Length 0 + 15 Bore diameter 0 + 4 Wall thickness 0 + 3 NOTEPipe sections are normally supplied in 1 m or2 m lengths. 1) Marking BS7523:1991on or in relation to a pro
24、duct represents a manufacturers declaration of conformity, i.e. a claim by or on behalf of the manufacturer that the product meets the requirements of the standard. The accuracy of the claim is therefore solely the responsibility of the person making the claim. Such a declaration is not to be confus
25、ed with third party certification of conformity, which may also be desirable.BS7523:1991 2 BSI 10-1999 Table 2 Physical properties Physical property Requirement Method of test Type A Type B Maximum thermal conductivity inW/(mK) at a mean temperature of40 C (see Appendix A) 0.040 0.045 Appendix B (se
26、e note 1) Maximum water vapour permeability (in ng/msPa) (see note 2) 1.4 1.4 Carry out method 8 of BS 4370-2 except that the water vapour pressure gradient shall be created by immersion into an atmosphere of 25 C and 75% r.h. Dimensional stability: maximum shrinkage (in%) 3 3 Carry out method 5B of
27、 BS 4370-1 at80 C for 96 h with a 1 m long section of pipe insulation. Report only the change in length Burning characteristics: maximum extent of burning (in mm) 25 25 BS 4735 (see CAUTION below, and Appendix C) Maximum smoke emission (in%) 10 10 BS 5111-1 (see Appendix C) Minimum closed cell conte
28、nt (in%) 85 85 Method 10 of BS 4370-2 Maximum apparent water absorption (in%) 2 2 Carry out the test described in Appendix D of BS 4840-1:1985 using test specimens 50 50 50 mm CAUTION. The small scale laboratory test described in BS 4735 is solely for assistance in monitoring consistency of producti
29、on and is not for use as a means of assessing the potential fire hazard of a material in use. NOTE 1Appendix B is technically equivalent to ISO/DIS 8497. NOTE 2To convert values in ng/msPa to 4g/Nh multiply the former by 3.6. Also, this maximum water vapour permeability value equates to a permeance
30、which is within the requirements of 10.4 of BS 6700:1987 (see Appendix D).BS7523:1991 BSI 10-1999 3 Appendix A Factors affecting the thermal conductivity The maximum “K” values for types A and B given inTable 2 are stated at40 C. For comparison purposes only, these values correspond to0.042w/mK at10
31、 C for type B and0.037w/mK for type A when derived by using the method in Appendix C of BS 5422:1977 (see Appendix D). That method shows that, by plotting a graph of thermal conductivity against the mean temperature at which the test was carried out, a curve can be produced. This enables the thermal
32、 conductivity at other temperatures to be derived. There are several factors which have a noticeable effect on the thermal conductivity of cellular polyethylene materials. These may also be used as a means of quality control by end users and specifiers. Products with varying densities have been test
33、ed and the optimum thermal conductivity values were found to be within the30kg/m 3to40kg/m 3range. The closed cell content is also an important factor, as the higher the closed cell content the less convection and radiation across the product. The cell size should also be taken into account, as larg
34、e cells increase the convection currents within the cells and very small cells can increase the transmission of heat through the cell walls. So again, there are certain parameters which should be adhered to during production in order to obtain the optimum thermal conductivity value. Appendix B Metho
35、d for the determination of thermal conductivity NOTEThis appendix is technically equivalent to ISO/DIS8497. B.0 Introduction The thermal transmission properties of pipe insulation generally have to be determined using pipe test apparatus rather than flat specimen apparatus such as the guarded hot pl
36、ate or the heat flow meter apparatus, if results are to be representative of end-use performance. Insulation material formed into flat sheets often has different internal geometry from that of the same material formed into cylindrical shapes. Furthermore, properties often depend significantly upon t
37、he direction of heat flow in relation to inherent characteristics such as fibre planes or elongated cells: thus flat specimen one-dimensional heat flow measurements will generally not be representative of the two-dimensional radial heat flow encountered in pipe insulation. Another consideration is t
38、hat commercial insulations for pipes are often made with the inside diameter slightly larger than the outside diameter of the pipe, thus creating an air gap of variable thickness. In those cases where end-use performance data rather than material properties are to be determined, the insulation is mo
39、unted on the test pipe in the same loose manner so that the effect of the air gap will be included in the measurements. This would not be the case if properties were determined in a flat plate apparatus where good plate contact is required. Still another consideration is that natural convection curr
40、ents around insulation installed on a pipe will cause non-uniform surface temperatures. Such conditions will not be duplicated in a flat plate apparatus with uniform plate temperatures. NOTEComparison tests on apparently similar material using both pipe apparatus and flat plate apparatus have shown
41、varying degrees of agreement of measured thermal transmission properties. It appears that better agreement is often obtained for heavier density products which tend to be more uniform, homogeneous, and sometimes more isotropic. For those materials which have repeatedly shown acceptable agreement in
42、such comparisons, the use of data from flat plate apparatus to characterize pipe insulation may be justified. As a general rule, when such agreement has not been shown, the pipe test apparatus should be used to obtain thermal transmission data for pipe insulations. B.1 Field of application This appe
43、ndix lays down conditions for the measurement of steady-state thermal transmission properties of thermal insulations for circular pipes generally operating at temperatures above ambient. It standardizes the measurement method, including procedures and apparatus performance, but it does not standardi
44、ze apparatus design. The type of specimen, temperatures and test conditions to which this appendix applies are detailed inB.5 andB.6. B.2 Reference ISO 7345,Thermal insulation Physical quantities and definitions. B.3 Definitions B.3.1 General The geometry of pipe insulation requires special terms no
45、t applicable to flat specimens. The word “lineal” is used to denote properties based upon a unit length (in the pipe axis direction) of a specified insulation size, e.g. the “lineal thermal transference”. These lineal properties, identified by the symbol subscript “l”, are convenient since the total
46、 heat loss can then be calculated knowing the pipe length and the applicable temperature. NOTEThe word “lineal” does not denote heat flow in the axial direction. In this appendix, the direction of heat flow is predominantly radial.BS7523:1991 4 BSI 10-1999 The more common “areal” properties, based u
47、pon unit area, are often confusing when applied to pipe insulation since the area is chosen arbitrarily and may range from that of the pipe surface to that of the insulation outer surface. If these areal properties are computed it is essential that the area and its location used in the computation b
48、e reported. Except for the transference (seeB.3.2) the following definitions and symbols are based upon those in ISO7345. B.3.2 lineal thermal transference, K l Lineal density of heat flow rate divided by the temperature difference between the pipe surface and the ambient air in the steady-state con
49、dition. It relates to a specific insulation size. B.3.3 lineal thermal resistance, R l Temperature difference between the pipe surface and the insulation outer surface divided by the lineal density of heat flow rate in the steady-state condition. It relates to a specific insulation size and is the reciprocal of the pipe lineal thermal conductance, l . B.3.4 lineal thermal conductance, l Reciprocal of the lineal thermal resistance, R l , from the pipe surface to the insulation outer surface. It relates to a specific
