1、BRITISH STANDARD BS 779:1989 Incorporating Amendment No. 1 Specification for Cast iron boilers for central heating and indirect hot water supply (ratedoutput44kW and above) UDC 697.3:696.4:621.1:669.13BS779:1989 This British Standard, having been prepared under the directionof the Refrigeration, Hea
2、ting and Air Conditioning Standards Policy Committee, waspublished under the authorityof the Board of BSI andcomes intoeffect on 31October1989 BSI 07-1999 First published February 1938 First revision July 1961 Second revision January 1976 Third revision The following BSI references relate to the wor
3、k on this standard: Committee reference RHE/10 Draft for comment 88/70535 DC ISBN 0 580 17835 8 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Refrigeration, Heating and Air Conditioning Standards Policy Committee (RHE/-) to Technical C
4、ommittee 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 Limited British Coal Corporation British Combustion Equ
5、ipment Manufacturers Association British Foundry Association British Gas plc Building Services Research and Information Association Chartered Institution of Building Services Engineers Department of Energy (Energy Efficiency Office) Department of the Environment (Property Services Agency) Domestic S
6、olid Fuel Appliances Approval Scheme Engineering Equipment and Materials Users Association Health and Safety Executive Institute of Domestic Heating Engineers Institution of Chemical Engineers Society of British Gas Industries Waterheater Manufacturers Association Amendments issued since publication
7、 Amd. No. Date of issue Comments 7704 July 1993 Indicated by a sideline in the marginBS779:1989 BSI 07-1999 i Contents Page Committees responsible Inside front cover Foreword ii Section 1. General 1.1 Scope 1 1.2 Definitions 1 1.3 Performance 1 Section 2. Materials 2.1 Boiler pressure bearing parts
8、2 2.2 Refractory materials 2 2.3 Pulling-up bolts and tie rods 2 Section 3. Construction and workmanship 3.1 Testing 3 3.2 Repairs to castings by welding 3 3.3 Boiler openings 3 3.4 Dampers, doors and observation ports 3 Section 4. Mountings and fittings 4.1 Safety valves 5 4.2 Vent pipes 5 4.3 Empt
9、ying valves or cocks 6 4.4 Pressure gauges 6 4.5 Temperature gauges 6 Section 5. Combustion equipment 5.1 General 7 5.2 Solid fuel firing 7 5.3 Liquid fuel firing 7 5.4 Gas firing 7 Section 6. Automatic controls and electrical installation 6.1 Automatic controls 9 Section 7. Inspection and marking 7
10、.1 Inspection 10 7.2 Marking 10 Appendix A Installation provisions 11 Appendix B Electrical installation 11 Appendix C Information to be supplied by the purchaser 13 Appendix D Information to be supplied by the manufacturer 13 Figure 1Heating system categories 8 Table 1 Tapping sizes for safety valv
11、es 5 Table 2 Sizes for safety valves (open vented systems only) 5 Table 3 Tapping sizes for vent pipes 6 Table 4 Minimum open vent pipe sizes 11 Publications referred to Inside back coverBS779:1989 ii BSI 07-1999 Foreword This British Standard has been prepared under the direction of the Refrigerati
12、on, Heating and Air Conditioning Standards Policy Committee. It supersedes BS779:1976 which is now withdrawn. As well as re-editing and updating the information to comply with current practice the requirements for type, works and site testing have been clarified together with a reappraisal of the pa
13、rameters for test pressures and specification of materials of construction. Appendix A includes information on those items which are essential inclusions on a boiler plant but which may not necessarily form part of the supply by the manufacturer. Appendix B gives recommendations for electrical wirin
14、g of boiler installations; however reference should be made to the 15th Edition of the Institution of Electrical Engineers (IEE) “Regulations for Electrical Installations” for electrical distribution in buildings and to the appropriate British Standards for the equipment, cables, controls and compon
15、ents of an electrical installation. It has been assumed in the drafting of this British Standard that the execution of its provisions is entrusted to appropriately qualified and experienced people. This standard forms one of a series of standards used in boiler construction, the others being: BS 855
16、, Specification. Welded steel boilers for central heating and indirect hot water supply (rated output 44 kW to 3 MW). BS 1113, Specification for design and manufacture of water-tube steam generating plant (including superheaters, reheaters and steel tube economizers). BS 1894, Specification for elec
17、trode boilers of riveted, seamless, welded and cast iron construction for water heating and steam generating. BS 2790, Specification for design and manufacture of shell boilers of welded construction. BS 1971, Specification for corrugated furnaces for shell boilers. This standard is included in the
18、list of “Standards significant to health and safety at work” 1)published by the UK Health and Safety Executive (HSE) and is also referred to by HSE in giving guidance. In order not to conflict with the work of CEN in the field of oil fired boilers it has been necessary to restrict the scope of this
19、standard. However, pending the publication of a European standard covering oil fired boilers up to 300 kW rated heat output, users of this standard will find the information contained useful when determining the specific requirements for such boilers. A British Standard does not purport to include a
20、ll 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 an
21、d ii, pages1 to 14, 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. 1) Available from the HSE through any of its offices.BS779:1989 BSI 07-199
22、9 1 Section 1. General 1.1 Scope 1.1.1 This British Standard specifies requirements for the design and construction including materials, workmanship, inspection testing and marking of cast iron boilers for central heating and indirect hot water supply. 1.1.2 This standard applies to boilers for hot
23、water with rated heat output of 44 kW or above when used with one or more of the following fuels: a) smokeless solid fuels, e.g.furnace coke, low temperature coke or anthracite; b) bituminous coal fired by means of mechanical stokers; c) gaseous fuels of the 2nd and 3rd families (seeBS4947); and wit
24、h rated heat output of300kW and above when used with liquid fuels of the classes specified in BS2869. 1.1.3 This standard does not apply to steam boilers or boilers pressurized by steam. NOTEThe titles of the publications referred to in this standard are listed on inside back cover. 1.2 Definitions
25、For the purposes of this British Standard the definitions given in BS1179:1967, BS1179-6:1980 and BS1846 apply, together with the following. 1.2.1 design pressure the pressure used for safety valve sizing (in bar) 2) . Itis equivalent to the works test pressure specified in3.1.3.1 divided by 1.8. It
26、 is also the maximum permissible setting pressure of any safety valve (see4.1.2.1) 1.2.2 operating pressure the maximum pressure measured in the boiler under normal operating conditions NOTEThe pressure will be dependent on static head, pressurizing equipment (where fitted) and the effect of the cir
27、culating pump. The static head, and pressurizing equipment in the case of pressurized systems, determine the maximum water temperature permissible at the point of lowest pressure. This temperature is not to exceed a predetermined level below the saturated steam temperature for the lowest pressure (s
28、ee6.1.2). 1.2.3 safety valve a spring-loaded automatic valve fitted to a boiler for relieving the build-up of excess pressure by means of discharge to atmosphere 1.2.4 inspecting authority the body or association which checks the design, materials and construction to ensure that they are in accordan
29、ce with this standard 1.3 Performance The manufacturer shall declare the rated heat output in kW and the efficiency of the boiler for the appropriate fuel or fuels under normal conditions of operation. The declared values shall be based on values determined in accordance with BS7190 or BS 845-1, whe
30、n the boiler is fired with combustion equipment either supplied or recommended by the manufacturer (seeAppendix D). For combustion equipment giving cyclic variations in heat release rate due to periodic refuelling or de-ashing operations, the period for which the rated output is obtainable shall als
31、o be stated. NOTE 1The manufacturer should supply, on request, a copy of the boiler performance test report (seeAppendix D). NOTE 2The purchaser should disclose to the manufacturer, at the time of enquiry, the information listed in Appendix C. 2) 1bar=10 5N/m 2=10 5Pa.BS 779:1989 2 BSI 07-1999 Secti
32、on 2. Materials 2.1 Boiler pressure bearing parts The minimum grade of grey cast iron used for the manufacture of the boiler pressure bearing parts shall be grade 180 of BS1452. NOTE 1As an alternative to grey cast iron a grade of spheroidal graphite or nodular graphite cast iron complying with BS27
33、89 may be used at the discretion of the manufacturer. NOTE 2The chemical composition of the cast iron is to be at the discretion of the manufacturer, but should in general be in accordance with the guidance given in Appendix A of BS1452:1977. The tensile test frequency for grey cast iron castings sh
34、all be as given in BS1452, except in the event of metal being transferred from small melting units and accumulated as batches in large holding furnaces, when at least one test bar representative of that sample shall be cast. The tensile test frequency for spheroidal or nodular graphite cast iron cas
35、tings shall be as given in BS2789. 2.2 Refractory materials Refractory materials used in the construction and assembly of the boiler or boiler components shall be suitable for the temperatures to which they will be subjected when the boiler is fired and operated as intended by the manufacturer. 2.3
36、Pulling-up bolts and tie rods Pulling-up bolts and tie rods shall be of steel having a minimum tensile strength of 430N/mm 2and in which neither sulphur nor phosphorus content exceeds0.05%. They shall be threaded in accordance with BS3643-1 and BS3643-2 or alternatively in accordance with BS1580.BS7
37、79:1989 BSI 07-1999 3 Section 3. Construction and workmanship 3.1 Testing NOTEIt is important that erection and site testing is in accordance with A.1; see also BS6880-3 for low temperature hot water heating systems. 3.1.1 General Type tests, carried out before production, on boilers or boiler secti
38、ons shall be in accordance with 3.1.2 and production tests on these items shall comply with3.1.3. 3.1.2 Type tests 3.1.2.1 At least one of each type of section of the same design, series and material, shall be subjected to a type test and shall withstand for a period of30min hydraulic pressure of14b
39、ar or four times the maximum operating pressure declared by the manufacturer, whichever is the greater. This test shall be repeated at least annually. Sections used in this test shall be discarded. 3.1.2.2 At least one assembled boiler of each design, made up to the maximum number of sections offere
40、d by the manufacturer, shall be subjected to a type test and shall withstand for a period of30min a hydraulic pressure of10.5bar or twice the maximum operating pressure declared bythe manufacturer plus3.5bar, whichever is the greater. Sections used in this test shall be discarded. 3.1.3 Production t
41、ests 3.1.3.1 Each boiler casting or boiler section shall withstand a hydraulic pressure test of7bar or twice the maximum operating pressure, declared by the manufacturer, whichever is the greater. The duration of the pressure test shall be1min plus the time taken to complete a visual inspection. The
42、re shall be no signs of leakage or weakness. 3.1.3.2 Where the boiler sections have been tested in accordance with3.1.3.1, the boiler, if finally assembled at the manufacturers works, shall be tested at a pressure of1.5times the maximum operating pressure declared by the manufacturer, for sufficient
43、 time to enable a full visual inspection to be made, and in any case for not less than5min. The boiler, during this test, shall show no signs of leakage or weakness. 3.2 Repairs to castings by welding The welding of defects in castings in positions subjected to pressure, or of lugs securing sections
44、, shall not be permitted. 3.3 Boiler openings 3.3.1 All boilers shall have suitable openings for flow and return connections and for mountings and fittings as specified in section4. 3.3.2 Openings for screwed connections or fittings shall have threads inaccordance with BS21. Theminimum length of int
45、ernal thread into which connections or fittings are screwed shall be in accordance with5.1 ofBS 21:1985. NOTEMountings with male ends not exceeding R3 size (inwhich the screwed portion is an integral part ofthemounting) and screwed pipe connections not exceeding R3 size may be screwed into tapped bo
46、sses on the boiler. 3.3.3 Adequate access shall be provided to permit the cleaning of combustion surfaces and flue ways. 3.4 Dampers, doors and observation ports 3.4.1 Solid fuel boilers 3.4.1.1 Air control damper. In order to control the combustion of the fuel in the boiler at varying rates of burn
47、ing, boilers which are hand-fired shall be provided with an adjustable air inlet below the grate. 3.4.1.2 Secondary air. Provision shall be made for the admission of secondary air above the fuel bed for hand fired boilers. 3.4.1.3 Doors at front and above grate level. The clearance between any door
48、and the surface against which it closes shall not exceed1mm except in the case of firing doors for hand fired boilers for which the clearance shall not exceed2mm. 3.4.1.4 Flue or chimney damper. Hand-fired boilers shall be fitted with a sliding or butterfly damper at the outlet. Sliding dampers shal
49、l be clearly graduated to facilitate accurate setting. Butterfly dampers shall have a handle, indicating clearly the position of the blade, which is to be capable of being held in position to prevent movement. Dampers of either type shall be so shaped that when in the fully closed position the free area to permit the passage of flue gases is not less than 12% of the area of the flue in the plane of the damper. In the case of boilers supplied for automatic stoking, where a damper is fitted, provision shall be made for it to be locked in the correct position.BS779:1989 4
