1、BRITISH STANDARD BS 6069-4.2: 1991 Characterization of air quality Part 4: Stationary source emissions Section 4.2 Method for the determination of asbestos plant emissions by fibre count measurementBS6069-4.2:1991 This British Standard, having been prepared under the directionof the Environmental an
2、d Pollution Standards Policy Committee, was published underthe authority of the Standards Board and comes intoeffect on 30 August 1991 BSI 07-1999 The following BSI references relate to the work on this standard: Committee reference EPC/35 Draft for comment 90/57222 DC ISBN 0 580 19809 X Committees
3、responsible for this British Standard The preparation of this British Standard was entrusted by the Environmental and Pollution Standards Policy Committee (EPC/-) to Technical Committee EPC/35, upon which the following bodies were represented: Association of Consulting Scientists British Coal Corpor
4、ation British Gas plc British Steel plc Department of Health Department of the Environment (Her Majestys Inspectorate of Pollution) Department of Trade and Industry (Laboratory of the Government Chemist) Department of Trade and Industry (Warren Spring Laboratory) Electricity Supply Industry in Engla
5、nd and Wales GAMBICA (BEAMA Ltd.) Health and Safety Executive Institute of Occupational Hygiene Institute of Petroleum Institution of Environmental Health Officers Institution of Gas Engineers Lead Development Association National Society for Clean Air Society of Chemical Industry The following bodi
6、es were also represented in the drafting of the standard, through subcommittees and panels: Asbestos Information Centre Ltd. Asbestosis Research Council Filtration Society Institute of Energy Institution of Chemical Engineers Amendments issued since publication Amd. No. Date CommentsBS6069-4.2:1991
7、BSI 07-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Definitions 1 3 Principle 1 4 Apparatus 2 5 Facilities at the sampling site 6 6 Site work prior to sampling 8 7 Sampling procedure 10 8 Analytical procedures 11 9 Method of calculation 11 10 Presentation an
8、d interpretation of results 12 Appendix A Safety precautions 13 Appendix B Care of apparatus 13 Appendix C Incorrect circumstances 14 Appendix D Typical site data sheet 15 Appendix E Typical presentation of results 16 Appendix F Accuracy and precision of method 16 Figure 1 Sampling train 2 Figure 2
9、Typical access port with probe support/port sealer 3 Figure 3 Typical sample nozzle and filter holder designs 4 Figure 4 Typical sampling time graph for 4 mm diameter nozzle 5 Figure 5 Position of sampling points 7 Figure 6 Typical velocity/sampling rate/nozzle size setting chart 9 Table 1 Sampling
10、location distances from obstacles 14 Publication(s) referred to Inside back coverBS6069-4.2:1991 ii BSI 07-1999 Foreword This Section of BS6069 has been prepared under the direction of the Environment and Pollution Standards Policy Committee and is based on ISO/DIS10397 “Stationary source emissions
11、Determination of asbestos plant emissions Method by fibre count measurement”. At the request of Her Majestys Inspectorate of Pollution, it is being published as a British Standard, for use in the UK in advance of publication of the ISO standard. BS6069 is being published in a series of Parts and Sec
12、tions that will generally correspond to particular international standards arising from the UK participation in the work of ISO/TC 146. This Section of BS6069 is one of several, relating to stationary source emissions, that are being published as Sections of BS6069-4. Methods concerning workplace at
13、mospheres are being published as Sections of BS6069-3. Topics relating to other aspects of air quality characterization will be published as further Parts or Sections of BS6069. The following Parts of BS6069 have already been published: Part 1: Units of measurement; Part 2: Glossary. Methods for the
14、 determination of particular constituents of ambient air are being published as Parts of BS1747. This Section of BS6069 is essentially made up of two parts: sampling of the asbestos-containing emissions; and fibre counting. Unfortunately the accuracy of the analysis (fibre counting) is such that it
15、adversely affects the accuracy of the whole method. Therefore it is vitally important that the analytical aspects are carried out by experienced analysts, who have been specially trained, in conjunction with an approved quality control scheme. Although this method has been produced to deal specifica
16、lly with fibre emissions from asbestos works, it can equally be applied to other processes dealing with fibrous materials. Indeed many asbestos works are using substitute fibres and, therefore, may at times produce mixed fibre emissions. Where this is probable, or where there is a need to identify w
17、hich fibres are asbestos and which are not, it will be necessary to employ more sophisticated techniques for fibre identification; such techniques are not covered in this Part of BS6069. It should be noted that, at present, there are differences in the way asbestos fibres and non-asbestos fibres are
18、 assessed, especially in the workplace. These differences, however, should not affect the way this method is used to assess the effectiveness of arrestment plant. This Part of BS6069 is intended to be used not only to give a quantitative concentration of fibres in emissions from asbestos works, but
19、also as a means of showing the effectiveness or otherwise of the operation of dust and fibre collection equipment. Because of the relatively short duration of sampling, the method is fairly sensitive to process fluctuations and, therefore, a full record of test parameters is required. The analytical
20、 technique used in this method follows that described in the Health and Safety Executive document MDHS 39/3. The information presented in appendices A to F is for background information only and does not form an integral part of the standard.BS6069-4.2:1991 BSI 07-1999 iii WARNING. Breathing asbesto
21、s dust is dangerous to health and precautions have to be taken during the sampling and measurement. Particular note has to be taken of the Control of Asbestos at Work Regulations 1987 (S.I. 2115, 1987). Safety precautions are described in Appendix A. A British Standard does not purport to include al
22、l 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 immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i to
23、iv, pages1to 18, 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 amendment table on the inside front cover.iv blankBS6069-4.2:1991 BSI 07-1999 1 1 Scope This Section of BS6069 describes
24、 a method, using a fibre count technique, for the assessment of fibre concentrations in flowing gas streams in ducts, chimneys or flues from asbestos-using industrial processes. This method is intended to be used to determine fibre concentrations from a wide range of processes where it is known that
25、 regulated fibres are present in emissions. No attempt is made to identify asbestos fibre types separately from other fibres. NOTE 1If fibre identification is required, then reference should be made to the use of electron microscopy and the Health and Safety Executive. NOTE 2This method may be used
26、to check that dust collection equipment used to trap asbestos fibres, or prevent their escaping into the atmosphere, is working properly and effectively. NOTE 3This method is suitable for measuring fibre concentrations as described in European Community Council Directive No. 87/217/EEC on the preven
27、tion and reduction of environmental pollution by asbestos. The range of application of the method for concentrations of fibres in ducts is about0.05 fibres/mL to10fibres/mL, although this range may vary slightly according to the sampled volume which, in turn, will depend on duct velocities and the s
28、ampling apparatus used. Appendix A gives safety precautions to be considered when carrying out the method described in this British Standard. Information on the accuracy and precision of the method is given in Appendix F. Appendix C gives information on sampling and measurement when the criteria giv
29、en in this method cannot be met. NOTE 4The titles of the publications referred to in this standard are listed on the inside back cover. 2 Definitions For the purposes of this British Standard, the following definitions apply. 2.1 aspect ratio ratio of the length of a fibre to its width 2.2 access po
30、rt a hole in the duct, provided with a flanged or threaded socket, through which a sampling probe is inserted along the sampling line 2.3 cumulative sampling the collection of a single composite sample obtained by sampling for the required period at each sampling point in turn 2.4 duct a chimney, st
31、ack or ducting at the outlet of dust-collecting equipment carrying asbestos fibre laden gases 2.5 fibre concentration the number of regulated fibres per millilitre of gas 2.6 fibre count technique a method for counting the number of regulated fibres present on a membrane filter and the calculation o
32、f fibre concentrations 2.7 hydraulic diameter for a rectangular duct, the hydraulic diameter, D h , is given by the following formula: 2.8 isokinetic sampling sampling at a rate such that the velocity and direction of the gas entering the sampling nozzle is the same as that of the gas in the duct ju
33、st prior to the sampling point 2.9 pump a fan, vacuum pump or other apparatus used for extracting a sample of gas from ducts or chimneys 2.10 regulated fibres fibres that meet the following criteria : lengthU 5m; diameter k 3 m; minimum aspectratio 3 : 1 2.11 sampling line the imaginary line on whic
34、h the sampling points are located. 3 Principle A sampling probe is inserted into a moving gas stream and a known volume is withdrawn isokinetically. The sampled gas is passed through a filter medium which removes particulate matter (including fibres) from the gas stream. The filter is treated so as
35、to make it transparent when viewed under a microscope, and then the number of fibres are counted in a precise number of fields as viewed using a phase contrast optical microscope. D h 4 area of the sampling plane perimeter of the sampling plane - =BS6069-4.2:1991 2 BSI 07-1999 Knowing the volume of
36、gas sampled, the cross-sectional area of the filter, the number of regulated fibres counted, and the cross-sectional area of each field, the concentration of fibres in the moving gas stream can then be calculated. 4 Apparatus 4.1 General. Use a sampling train for sampling regulated fibres as shown i
37、n Figure 1. The apparatus to be used shall be as described in 4.2 to4.15. The apparatus shall be constructed of materials, e.g. stainless steel, capable of withstanding the conditions under which they will be used, shall be portable or transportable, and shall be capable of sampling isokinetically (
38、see9.3) at a steady rate. NOTE 1Access ports will be needed on the duct to enable sampling to take place. NOTE 2Useful information on the care of the apparatus is given in Appendix B. 4.2 Sampling probe (including nozzle and fibre collector), complying with the following requirements. The probe tube
39、 shall be rigid and tubular and shall be attached to the sample nozzle and filter holder and of sufficient length to enable these to be inserted into the duct through an access port, to reach all sample points. It shall be provided with a mechanism for sealing the access port in such a way that ingr
40、ess of ambient air or escape of duct gases are kept to a minimum. NOTE 1This sealing mechanism can also act as a support and means for securing the probe in the correct sampling positions. A typical design is shown in Figure 2. In practice, the sample nozzle shall be sharp edged, but short enough to
41、 minimize the possibility of fibre deposition (seeFigure 3). Also it shall be robust, to prevent damage by general use, and shall give even distribution of fibres over the filter. NOTE 2The examples shown in Figure 3 have been evaluated to ensure even distribution of fibres over the membrane filter.
42、 The diameter of the nozzle at the entrance shall be not less than 4mm. No reduction shall be made in the internal diameter over a distance of one diameter of the entry section. Any subsequent changes in bore diameter shall be tapered rather than stepped, and joints shall be smooth to prevent fibre
43、deposition. Any bends in this section shall have a minimum radius of1.5times the nozzle bore diameter. The internal surfaces of the nozzle and any tubing prior to the filter shall be to a smoothness of k 0.2m to prevent deposition of fibres. A range of different sized nozzles shall be available so t
44、hat samples can be withdrawn isokinetically from gas streams in ducts over a range of velocities (see6.5.1 and Figure 4). The fibre collector shall be situated as close as is convenient behind the sample nozzle to minimize deposition. (SeeFigure 3.) 4.3 Fibre collector, which shall be a membrane fil
45、ter (comprising mixed esters), with an efficiency of capture of greater than 98 % for3m size particles, and of diameter 25mm or 37mm. NOTENumbers correspond to subclause numbers in clause4. Figure 1 Sampling trainBS 6069-4.2:1991 BSI 07-1999 3 Figure 2 Typical access port with probe support/port sea
46、lerBS6069-4.2:1991 4 BSI 07-1999 Figure 3 Typical sample nozzle and filter holder designsBS6069-4.2:1991 BSI 07-1999 5 4.4 Flow meter for sampling purposes, such as an orifice plate, variable flow orifice, or equivalent, with a volumetric flow rate accurate to within 2 %. NOTEIn most circumstances,
47、variable flow orifices have been found satisfactory for flow control, but orifice plates, etc. have also been used. Although variable flow orifices are used to control the sample flow rate of isokinetic sampling, it is necessary to have an accurate measure of the volume of gas sampled. 4.5 Regulator
48、 for sampling, e.g. a control valve, capable of maintaining isokinetic sampling (see9.3). NOTERegulation of the sampling rate is usually carried out by the use of apparatus such as a control valve, although voltage control of the suction unit is permissible if sensitive enough. 4.6 Pump, e.g. a vacu
49、um pump or fan, capable of maintaining isokinetic sampling in all situations (see9.3). It shall be capable of overcoming the pressure drop created by the sampling apparatus and that within the duct, and shall provide a continuous smooth flow. NOTEThis graph assumes the use of a 25mm membrane filter with an exposed area of 368mm 2and with a loading of 300 fibres/mm 2 . Figure 4 Typical sampling time graph for 4 mm diameter nozzleBS6069-4.2:1991 6
