1、BRITISH STANDARD BS845-1:1987 Incorporating Amendment No. 1 Methods for Assessing thermal performance of boilers for steam, hot water and high temperature heat transfer fluids Part 1: Concise procedureBS845-1:1987 This British Standard, having been prepared under the directionof the Refrigeration, H
2、eating and Air Conditioning Standards Committee, was published under the authority ofthe Board of BSI and comes intoeffect on 30June1987 BSI 02-1999 First published, as BS845, April1939 First revision, as BS845, September1961 Second revision, as BS845, July1972 Third revision, as BS845-1, June1987 T
3、he following BSI references relate to the work on this standard: Committee reference RHE/10 Draft for comment 83/73794 DC ISBN 0 580 15856 X Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Refrigeration, Heating and Air Conditioning Stan
4、dards Committee (RHE/-) to Technical Committee RHE/10, upon which the following bodies were represented: Associated Offices Technical Committee Association of British Solid Fuel Appliances Manufacturers Association of Shell Boilermakers Boiler and Radiator Manufacturers Association Ltd. British Coal
5、 British Combustion Equipment Manufacturers Association British Foundry Association British Gas Corporation Building Services Research and Information Association Chartered Institution of Building Services Engineers Department of Energy (Energy Efficiency Office) Department of Energy (Gas Standards)
6、 Department of the Environment (Property Services Agency) Domestic Solid Fuel Appliances Approval Scheme Engineering Equipment and Materials Users Association Health and Safety Executive Hevac Association Institute of Domestic Heating Engineers Society of British Gas Industries The following bodies
7、were also represented in the drafting of the standard, through sub-committees and panels: Association of Consulting Engineers British Paper and Board Industry Federation (PIF) Institution of Chemical Engineers Institution of Mechanical Engineers National Industrial Fuel Efficiency Service Water-tube
8、 Boilermakers Association Amendments issued since publication Amd. No. Date of issue Comments 9191 November 1996 Indicated by a sideline in the marginBS845-1:1987 BSI 02-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Definitions 1 3 General 1 4 Instrumentation
9、 2 5 Procedure 3 6 Calculations 4 7 Report 7 Appendix A Report data 11 Appendix B The accuracy of boiler tests 13 Appendix C Radiation, convection and conduction losses for boilers of conventional design 15 Figure 1 Outline of the procedure for calculating from the test measurements 10 Table 1 Typic
10、al instruments and their accuracies 2 Table 2 Symbols and units 8 Table 3 Typical radiation, convection and conduction losses from water-tube and shell boilers 15 Table 4 Typical radiation, convection and conduction losses from sectional hot water boilers 15 Publications referred to Inside back cove
11、rBS845-1:1987 ii BSI 02-1999 Foreword This Part of BS845has been prepared under the direction of the Refrigeration, Heating and Air Conditioning Standards Committee. Together with BS845-2 it supersedes BS845:1972, which is withdrawn. The revised edition of BS845describes, in two Parts, the procedure
12、s that should be used and the data that should be collected in order to obtain an assessment of the thermal performance of steam, hot water or high temperature heat transfer fluid boilers, generally of output greater than44kW. The results may be based on either the net or the gross calorific value o
13、f the fuel. The procedures described in this British Standard are for thermal performance only but are based on the assumption that boilers are operated during the assessment in such a manner as to comply with relevant safety requirements and the requirements of national environmental legislation. B
14、S845is published in two Parts as follows. Part 1: provides a concise but complete procedure and is convenient for boilers which are thermodynamically simple, i.e.having a single major source of heat input and a simple circuit for water, steam or high temperature heat transfer fluid; Part 2: provides
15、 a comprehensive procedure suitable for all boilers including those with multiple thermal flows to and from the boiler. Part1 applies to boilers which do not condense moisture out of the flue gases. As experience is gained in industry with boilers with this facility, consideration will be given to p
16、ublishing an addendum to give additional requirements in this respect. Part 1provides a straightforward procedure at minimum cost. It is intended to be used in connection with the testing of sectional cast iron, welded steel, shell and simple water-tube boilers for steam, hot water or high temperatu
17、re heat transfer fluid. More complex boilers should be assessed in accordance with BS845-2but, in this context, no definitive division of boilers is possible. Part 1is concerned with boilers having conventional firing equipment and fired with solid fuels as normally supplied, fuel oil of standard gr
18、ades, liquified petroleum gases or natural gas. It may be used also for assessments to be made where plant includes a special form of firing or involves the combustion of an unconventional fuel, the characteristics of which are not readily obtainable, but in such cases heat output should be measured
19、 in place of heat input as described in the following paragraph. Where a more detailed assessment is required, Part2 of this standard should be used. Part 1uses the indirect (losses) procedure, in which the heat input is measured or, if not possible, the thermal output and the losses are established
20、. Where the heat input cannot be measured conveniently the heat output may be measured as an alternative provided that the necessary accuracy of measurement can be achieved. An assessment in accordance with this Part of BS845may be required on the following occasions: a) after the commissioning of n
21、ew plant or after the recommissioning of modified plant in order to verify compliance with a specification or contractual obligation; b) whenever the user wishes to determine the current performance of the plant either on a routine basis or due to change of load or other operating conditions or when
22、 a change of fuel or a modification to the plant is being considered; c) whenever the user wishes to check combustion conditions.BS845-1:1987 BSI 02-1999 iii Regular assessments in accordance with this Part of BS845will enable boiler plant to be monitored in normal operation for optimum efficiency i
23、n the interests of fuel conservation. 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 immunity from legal obligations. Sum
24、mary of pages This document comprises a front cover, an inside front cover, pages i to iv, pages1to16, 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 theinside front
25、 cover.16 blankBS845-1:1987 BSI 02-1999 1 1 Scope This Part of BS845describes a concise procedure for conducting thermal performance assessments, using the indirect (losses) procedure, to give results within a tolerance of2percentage points 1)for boilers for steam, hot water or high temperature heat
26、 transfer fluids and for presenting the results in tabular form. Test results are based on either the gross or the net calorific value of the fuel. This concise procedure provides a convenient means for assessing boilers which are thermodynamically simple, i.e.having a single major source of heat in
27、put and a simple circuit for water, steam or high temperature heat transfer fluid, and that do not condense moisture out of the flue gases. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Definitions For the purposes of this Part of BS845the fol
28、lowing definitions apply. 2.1 assessed losses any thermal losses established from predetermined data 2.2 gross calorific value the amount of heat liberated by the complete combustion, under specified conditions, of unit volume of a gas or unit mass of a solid or liquid fuel in the determination of w
29、hich the water produced by combustion of the fuel is assumed to be completely condensed and its latent and sensible heat made available (see BS526) 2.3 net calorific value the amount of heat generated by the complete combustion, under specified conditions, of unit volume of a gas or unit mass of a s
30、olid or liquid fuel in the determination of which the water produced by the combustion of the fuel is assumed to remain as a vapour (see BS526) 2.4 heat input the heat content of the fuel used during the test based on the gross or net calorific value plus the sensible heat in the fuel above ambient
31、temperature 2.5 heat output the heat gained by the heat carrier from the boiler during the period of the test 2.6 measured losses any thermal losses calculated from actual measurements made during the test 2.7 indirect procedure the determination of thermal performance by the assessment of the therm
32、al losses and the measured thermal input or output. Major thermal losses are determined directly from measured quantities; minor losses are determined directly or assessed and in the case of radiation and convection losses Appendix B gives values 2.8 radiation, convection and conduction losses the l
33、osses from water, steam, combustion air, orgas-backed surfaces prior to the flue gas temperature measurement point and directly from flame to the floor and surroundings of the unit 2.9 test error the combined error due to sampling, measurements, calculations and assumptions used to obtain test resul
34、ts. The overall effect may be positive or negative 2.10 thermal efficiency the difference between100%and the total percentage losses based on either the gross or net calorific value of the fuel. This is equivalent to the ratio of the useful heat output to the heat input expressed as a percentage 2.1
35、1 turn-down ratio the ratio of maximum and minimum fuel inputs for continuous firing in unit time specified by the manufacturer. This ratio can also be expressed in terms of boiler output provided the appropriate efficiencies are known 3 General NOTEWhere a thermal performance assessment is to be ca
36、rried out after the commissioning of new plant or after the recommissioning of modified plant, it is necessary for the parties concerned to decide at the plant tendering or ordering stage on the test data required and on the test accuracy and hence the instrumentation to be used (see Appendix B). It
37、 is also necessary for the parties concerned to decide whether the test is to be carried out by the contractor or by an independent body and by whom it is to be witnessed. 3.1 Tests shall represent the intended method and system of operation of the plant under the intended conditions of installation
38、 and normal operation. 1) One percentage point is one hundredth of the total amount concerned, in this instance, the heat input.BS845-1:1987 2 BSI 02-1999 NOTEAttention is drawn to the need for compliance with statutory requirements relating to smoke, grit, dust, SO 2and NO Xemission. 3.2 Tests shal
39、l be carried out at predetermined firing rates, e.g. those corresponding to boiler rated output and to any reduced output of which the firing equipment is capable automatically, e.g. low rate of fire on high/low/off equipment and middle and low rates on firing equipment which fully modulates over a
40、range. NOTE 1This may necessitate manually holding the firing rate at a particular setting and will require the availability of sufficient load during the period required to establish steady state (see5.2) and for the duration of the test. NOTE 2These tests will enable the rated output and turn-down
41、 ratios to be verified. 4 Instrumentation 4.1 All measurements shall be made with instruments calibrated in accordance with the manufacturers instructions. Portable or mobile instruments shall be used unless it can be shown that the sensors of installed instruments have been located correctly (see5.
42、8) and the system checked for accuracy. NOTEA range of typical instruments suitable for the tests described in this standard are listed in Table 1 and their use is acceptable within their stated limits of accuracy. Table 1 Typical instruments and their accuracies Measurement Instrument Probableerror
43、 a Remarks Fluid flow Positive displacement 1%reading Range10:1 Orifice, nozzle or venturi 2%reading Range3:1 Pitot tube 2%reading Range3:1local flow only Gap meter 2%reading Range10:1 Common vane-type meter 2%reading Range10:1 Vortex-shedding meter 1%reading Range10:1 Turbine meter 0.25%reading Ran
44、ge10:1 Gas analysis CO colorimetric 10%reading Range to be selected CO 2Orsat 0.1%CO 2 Delicate, requires expert use CO 2compact absorption type 0.3%CO 2 Simple and robust CO 2katharometer 0.2%CO 2 Can be vitiated by other gases O 2Orsat 0.2%O 2 Delicate, requires expert use O 2compact absorption ty
45、pe 0.3%O 2 Simple and robust O 2paramagnetic 0.1%O 2 Robust, air calibrated O 2electrochemical cell b 0.2%O 2 Cell deteriorates in time Mass Weighbridge 0.5%reading Solid and liquid fuels Pressure Bourdon gauge 2%full scale deflection Robust Temperature Mercury-in-glass thermometer 1scale division D
46、elicate Mercury-in-steel thermometer 1scale division Robust, but bulky Thermocouple 1 C Robust and very flexible Resistance thermometer 0.1C NOTEThe above table should be regarded as a guide since new forms of portable instrument are continually becoming available (e.g. infra-red analysers and elect
47、rochemical cells for certain gas analyses) and this should be borne in mind. a After calibrating, where appropriate. Different makes and models of instruments may vary in the manner in which their probable reading errors are expressed. b Where an electro-chemical cell is used convert the result to a
48、 dry basis.BS845-1:1987 BSI 02-1999 3 5 Procedure 5.1 General Tests shall be carried out whilst the boiler is fired continuously under steady state conditions established prior to the test (see5.2). NOTEAn outline of the procedure for calculating from test measurements is shown in Figure 1. 5.2 Stea
49、dy state 5.2.1 Steam pressure and feed water temperature or, for hot water boilers, the flow and return temperatures, together with the relevant flow rates, shall be held as steady as possible and at levels close to normal operating conditions. NOTE 1For special operating conditions applying in the case of solid fuel combustion devices having a cyclic pattern of operation see5.5.2.2. NOTE 2During the operation of a boiler the various factors contributing to heat losses will vary from their intended values as a resul
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