BS 5854-1980 Code of practice for flues and flue structures in buildings《建筑物中烟道和烟道结构实用规程》.pdf

1、BSI S*5854 BO I Lh2Yhh 04bb32 2TB = BS 5854 : 1980 UDC 69.027.1 3 Code of practice for Flues and flue structures in buildings Code de bonne pratique relatif aux chemines et structures de chemines dans les btiments Richtlinien fr Abzge und Abgasstrukturen in Gebuden British Standards Institution Gr 9

2、 Contents Foreword Cooperating organizations Code of practice Page 1 Back cover 1. 2. 3. 4. 5. 6. 7. 8. 9. 1 o. Scope References Definitions Symbols Design requirements and procedure Forms and materials of construction Building services design Structural design of linings Steel liners Workmanship Ap

3、pendices A. Derivation of design values B. Calculation of design data: worked example using liquid fuel C. Calculation of design data: worked example using gaseous fuel D. Theory for calculation of stresses in brittle flue lining materials (using design charts) E. Sample calculations for diatomaceou

4、s brick linings Tables 1. 2. 3. 4. 5. 6. 7. 8. 9. Lining operating temperature limitations Material properties Acid resistance of mortars Insulating materials Properties of liquid fuels Average properties of typical industrial solid fuels Typical properties of gaseous fuels Reduction factor /3 for p

5、ermissible axial stresses Striking of formwork (minimum times) 2 2 2 3 4 6 8 11 14 15 20 20 24 25 26 27 28 29 29 29 30 30 31 31 Foreword Several premature failures of flue linings that have occurred during the last few years have emphasized the need for a more rigorous approach to the whole design p

6、rocess of flue linings, using more comprehensive materials data, and a much closer liaison between the structural and building services engineers. Therefore, this code of practice presents the latest informa- BS 5854 : 1980 Page Figures 1. 2. 3. 4. 5. 6. 7. 8. 9. 1 o. 11. 12. 13. 14. 15. 16. 17. 18.

7、 19. 20. 21. 22. 23. 24. 25. 26. 27. Air leakage through brickwork Schematic diagram of design procedure Examples of free-standing linings Examples of integral linings Acid corrosion rate of surfaces in contact with flue gases The effect of temperature on the pressure distribution of gases Conversio

8、n of actual flue gas velocity to velocity pressure Theoretical buoyancy due to flue gas tem peratu re Temperature gradient across the flue structure Surface coefficient of heat transfer Typical layouts at chimney entry Suggested support for brickwork lining at intermediate levels where access cannot

9、 be achieved from below Suggested design of lateral locators for steel liners Typical construction at top of chimney Relation between q/6 and c/6 for d,/r = O Relation between q/6 and c/6 for d,/r = 0.25 Relation between q/e and c/6 for d,/r = 0.5 Relation between q/6 and c/o for d,/r = 0.75 Relatio

10、n between q/6 and c/6 for d,/r = 1 .O Relation between q/ and c/6 for d,/r = 1.25 Relation between q/6 and c/6 for d,/r = 1.5 Typical courses for inner ring of lining (shown in 114 mm brick) Typical courses for inner ring of lining (shown in 152 mm brick) Bonding of circular brickwork linings using

11、114 mm or 152 mm bricks Bonding of circular brickwork linings using 229 mm bricks Static pressure distribution in flue system as used in the example in appendix B Temperature gradient across the lining 32 33 35 36 39 39 40 41 41 42 43 45 46 46 48 48 49 49 50 50 51 52 53 53 54 55 56 tion on available

12、 lining materials: it brings together full design data for the building services engineer; it examines the lining from a structural viewpoint when subjected to self-weight, wind and thermal loading; it demonstrates the areas of design where collaboration between the structural engineer and building

13、services engineer is necessary; and it gives recommendations for construction. This code of practice represents a standard of good practice and therefore takes the form of recommendations. Compliance with it does not confer immunity from the relevant statutory and legal requirements. 1 BSI BSn.5854

14、80 m 1624669 0466934 070 m BS 5854 : 1980 British Standard Code of practice for Flues and flue structures in buildings 1. Scope This code of practice gives recommendations for the design and construction of flue linings and flue structures serving appliances (boilers and air heaters) of 45 kW output

15、 and above, burning solid, liquid or gaseous fuels. The recommendations contained in this code may be used for the design of a flue serving an incinerator, which should be provided with its own individual flue. Prior approval of the height of the chimney by the local authority is required by Section

16、 6 of the Clean Air Act 1968 where the appliance(s) served by the chimney burn(s) (a) pulverized fuel or (b) 45 kg or more of solid fuel per hour or (c) liquid or gaseous fuel at a rate of 366 kW or more if: (1 ) a new chimney is erected to serve a new or existing installation; or (2) an installatio

17、n (e.g. of boilers, incinerators) served by an existing chimney is enlarged, e.g. its combustion capacity is increased, or an additional appliance is added to the system; or (3) an appliance served by an existing chimney is removed and replaced by one having a larger combustion capacity. The officia

18、l publication Chimney heights. Second edition of the 1956 Clean Air Act Memorandum,* subsequently referred to in this code of practice as the Chimney Height Memorandum, gives guidance for the calculation of heights likely to be suitable in most instances for solid or liquid fuel appliances. Useful i

19、nformation to facilitate calculation of possible chimney heights for gaseous fuel is contained in the CIBS Guide, Volume B, Section B13 (1970)t. This code applies to: (a) linings that are built within a space enclosed by a building; (b) linings that are built as an integral part of the bu i Idi ng.

20、This code does not, in general, apply to linings within a freestanding or independent chimney, but many of the conditions and criteria are applicable. The design of flue linings and flue structures in buildings is subject to increasing knowledge and experience, and should be undertaken only by those

21、 competent to evaluate the many aspects of satisfactory construction and performance. This code provides the building services engineer and the structural engineer with design criteria, suggested procedures and methods of design, recommendations for construction, and basic guidance data for the sele

22、ction of lining materials. The code also seeks to augment the skills of experienced designers who will need to interpret the information and examples with appropriate professional expertise, giving due consideration to all the relevant issues involved. The examples and calculations in this code are

23、given as one form of use of the data provided. They do not preclude other methods of computing satisfactory designs. Where appropriate, detailed information has been put in appendices. 2. References The titles of the standards publications referred to in this code are listed on the inside back cover

24、. 3. Definitions For the purposes of this British Standard, the following definitions apply. 3.1 access. Provision for entry to flues to facilitate inspection and repair. 3.2 access door. A door, normally at the base of the flue, to provide access and/or to permit the removal of flue dust and allow

25、cleaning of the flue. 3.3 acid dew-point. The temperature at which acid present in the flue gases condenses. 3.4 basic material property. The material property that is obtained from data from tests performed on new materials at normal temperatures in a dry condition. 3.5 chimney. The part of a struc

26、ture that contains one or more flues. 3.6 corbel. A unit cantilevering from a wall surface to form a bearing. 3.7 cowl. A conical or dished cap fitted to the top of the chimney to prevent or minimize the ingress of rainwater, 3.8 dead leg. A section of flue in which the main flue gas flow does not t

27、ake place; commonly, the extension of a vertical flue below the flue gas entry. 3.9 design material property. The material property to be used in design. It is the basic material property modified due to the effects of moisture content and operating temperature. 3.10 downwash. The tendency for flue

28、gases to travel a short distance down the outside of the chimney in the negative pressure area created on its leeward side by wind. It tends to reduce the effective height of the chimney. 3.1 1 drain points. Locations provided for the removal of water from the duct or flue. * Published by Her Majest

29、ys Stationery Office (HMSO). t Published by the Chartered Institution of Building Services. BSI BSm5854 BO W 3624669 O466935 TO7 BS 5854 : 1980 3.12 draught stabilizer. A device designed to reduce the amount of natural draught available by diluting flue gases with cold air. 3.13 efflux velocity. The

30、 velocity of hot flue gases passing from the flue to the atmosphere. 3.14 expansion joint. A joint that allows relative move- ment between parts of the lining or between the lining and the surrounding structure. 3.15 explosion door. A device that allows the release of excess pressure in the flue sys

31、tem. 3.16 fan-diluted flues. A fan-operated system used to dilute flue gases with air, reducing the carbon dioxide content to about 1 % before final discharge, usually at low level. 3.17 flue. The shaped passageway through which flow the products of combustion. NOTE. It is desirable to restrict the

32、term flue to its aerodynamic context, .e. the term flue should not be used if the meaning lining is intended, although the term flue lining is acceptable. 3.18 flue gas. Gaseous products of combustion. 3.19 freestanding lining. A lining or part of a lining that is not bonded throughout its height to

33、 the main structure. 3.20 integral lining. A lining or part of a lining that is bonded throughout its height to the adjacent structure. 3.21 inversion. The entry of cold air into the individual section of a lining discharge point. 3.22 liner. A metal or reinforced plastics tube serving as a lining.

34、3.23 lining. The membrane or structure incorporating the boundary of the shaped passageway for the flue gases and providing containment for those gases. 3.24 lining height. The dimension of a lining to be used for calculating the slenderness ratio. 3.25 mid-feather. A partition between adjacent flue

35、s. 3.26 negative pressure. When referred to a flue, the pressure inside the flue is less than the pressure outside the flue. 3.27 positive pressure. When referred to a flue, the pressure inside the flue is greater than the pressure outside the flue. 3.28 smuts. general term describing agglomerated s

36、oot or ash particles discharged to the atmosphere in waste gases. Their size range is typically 1 mm to 10 mm diameter. They originate from the deposits on lining surfaces and may where those surfaces operate below the acid dew-point temperature of the flue gases. 3.29 turn down ratio. The relations

37、hip between the maximum fuel input and the minimum fuel input. . include acid and corrosion materials, e.g. iron sulphates, 4. Symbols A Cross-sectional area of flue m2 AS Inner surface area of the flue lining m2 Symbol Definition Units through which thermal transmittance takes place B Appliance rat

38、ing (output) MW C, Specific heat of flue gas or air at constant pressure J/(kg KI Symbol C“ C d dt E f ft h hf h r mr n P Q Q Definition Gross calorific value of fuel Maximum longitudinal compressive stress at inside of lining at the location considered Internal diameter of circular flue Thickness o

39、f lining material Youngs modulus of elasticity Coefficient of friction (from CIBS Guide, Volume B, Section B13 (1 970) Modulus of rupture of lining material Volume flow rate of flue gas Acceleration due to gravity Chimney height Draught required at boiler outlet Theoretical draught available due to

40、chimney effect Total pressure loss due to friction of fluid flowing through section under consideration Static pressure change Change in velocity pressure across the section under consideration Vertical length of the column of the flue gases Surface coefficient of heat transfer Surface coefficient o

41、f heat transfer to the inner surface of the flue lining Surface coefficient of heat transfer from the outer surface of the complete flue structure to the adjacent space Surface roughness Thermal conductivities of lining components Velocity pressure factors (from CIBS Guide, Section B 13 (1 970) and

42、Section C4 (1 977) in which these factors are denoted by ( Thickness of component parts of composite I in i ng Lining length between lateral supports Mass flow rate of flue gas Number of air changes per second Perimeter of flue Rate of heat transfer Stress due to self weight and flexure (modified by

43、 slenderness in the absence of cracking) Lining air cavity resistance Reynolds number Internal radius of flue Radius of gyration of flue Sulphur content of fuel Units MJ/kg or MJ/m3 MPa mm mm M Pa - M Pa m3 /s m/s2 m Pa Pa Pa Pa Pa m W/(m2 K) mm W/(m K) m m kgis s - m W M Pa m2 KAN - mm m % massimas

44、s 3 BSI BSX5854 BO Lb24669 0466936 9Y3 W BS 5854 : 1980 Symbol Definition Units may produce positive pressure in the flue so that any Ta Tf tl, t2, etc. rai tao tf tfi tfo tr At U Vr V VP wrn W xt Y Z z QI P Y 6 17 f 0 I-( P U U Ambient temperature (absolute) Flue gas temperature (absolute) Componen

45、t interface temperatures Air temperature at base of flue Air temperature at top of flue Flue gas temperature (Celsius) Flue gas temperature at flue entry Flue gas temperature at flue exit Air temperature under consideration Temperature drop across flue lining Thermal transmittance Room volume. Adjac

46、ent air space volume Velocity of flue gas at a point under consideration Velocity pressure Rate of fuel consumption Percentage load factor for stress design calculation Fuel constant Depth from inside face of lining to the root of a crack Length of flue Length of flue under consideration Coefficient

47、 of linear expansion Reduction factor for permissible axial stresses Stress factor derived from w = d,/r (see appendix D) Appliance efficiency based on C, = y/r (see appendix D) QIAt (see appendix D) 1 -u Absolute viscosity of fluid Density of fluid Poissons ratio = 1 - s (see appendix D) K K OC “C

48、OC “C “C “C “C OC W/(mZ K) m3 m Is Pa kgls % - mm m m K -l - - - % - - kglm 4 kg/m3 - - 5. Design requirements and procedure 5.1 Function of chimney. The principal function of a chimney is to convey products of combustion from the appliance(s) to the atmosphere and to discharge them at such a height

49、 as toensure dispersal over a large area, thereby reducing the ground level concentrations to an acceptable level. 5.2 Operating conditions in flue. Compliance with the Clean Air Act 1968 (see clause I) produces certain condi- tions in the flue that may differ from those normally found in the older, large diameter, natural draught flues; see the following examples. (a) High flue gas velocities may cause the frictional pressure drop to be greater than the pressure head available due to the buoyancy of the flue gases. This waste gas leakage would be outwards