SIST EN 12953-6:2002
(Main)Shell boilers - Part 6: Requirements for equipment for the boiler
Shell boilers - Part 6: Requirements for equipment for the boiler
This standard applies to shell boilers as defined in EN 12953-1. This Part of the European standard specifies rules for safety related equipment of shell boilers.
Großwasserraumkessel - Teil 6: Anforderungen an die Ausrüstung für den Kessel
Diese Norm gilt für Großwasserraumkessel wie in EN 12953-1 festgelegt. Dieser Teil der Europäischen Norm legt Regeln für die sicherheitstechnische Ausrüstung von Großwasserraumkesseln fest.
Chaudieres a tubes de fumée - Partie 6: Exigences pour l'équipement de la chaudiere
Cette partie de la norme européenne spécifie les regles pour l'équipement relatif a la sécurité des chaudieres a tubes de fumée, indépendamment des niveaux de surveillance définis dans le prEN 12953-1.
Mnogovodni kotli - 6. del: Zahteve za opremo kotla
General Information
Relations
Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Mnogovodni kotli - 6. del: Zahteve za opremo kotlaGroßwasserraumkessel - Teil 6: Anforderungen an die Ausrüstung für den KesselChaudieres a tubes de fumée - Partie 6: Exigences pour l'équipement de la chaudiereShell boilers - Part 6: Requirements for equipment for the boiler27.060.30Grelniki vode in prenosniki toploteBoilers and heat exchangersICS:Ta slovenski standard je istoveten z:EN 12953-6:2002SIST EN 12953-6:2002en01-november-2002SIST EN 12953-6:2002SLOVENSKI
STANDARD
SIST EN 12953-6:2002
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 12953-6May 2002ICS 27.060.30; 27.100English versionShell boilers - Part 6: Requirements for equipment for the boilerChaudières à tubes de fumée - Partie 6: Exigences pourl'équipement de la chaudièreGroßwasserraumkessel - Teil 6: Anforderungen an dieAusrüstung für den KesselThis European Standard was approved by CEN on 15 May 2002.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the Management Centre or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the officialversions.CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2002 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 12953-6:2002 ESIST EN 12953-6:2002
EN 12953-6:2002 (E)2ContentspageForeword.31Scope.42Normative references.43Definitions.44General requirements for steam and hot water generators.54.1Safeguards against excessive pressure.54.2Materials for valves, fittings, flanges and bolting.54.3Limiting devices and safety circuits.54.4Temperature measurement of the furnace wall.54.5Boiler heat supply.54.6Flue-gas heated economizers.65Special requirements for steam boilers.65.1Water level indication.65.2Steam pressure and temperature indication.75.3Drain and blowdown devices.85.4Valves for connections.85.5Feed water supply.95.6Feed water control.95.7Limiting devices.95.8Heat supply.95.9Electrically-heated boilers.96Special requirements for hot water generators.106.1Hot water generating systems (for example see annex A).106.2Expansion and feed lines for open vented systems.106.3Water supply.116.4Circulating pumps.116.5Drain devices.116.6Water level indication.126.7Water supply control.126.8Limiting devices.126.9Vent valves.136.10Steam pressure and temperature indication.136.11Pressure controller.136.12Discharge from safety valves.136.13Heat supply.146.14Electrically heated hot water generators.146.15Parallel mode of operation of hot water generators.146.16Safety equipment for hot water generators.147Small shell boilers.177.1Steam boilers.177.2Hot water generators.17Annex A (informative)
Design examples for hot water generating systems.18Annex B (normative)
Dimensioning of Expansion Space.28Annex C (informative)
Operational aspects.31Annex ZA (informative)
Clauses of this European Standard addressing essential requirements or otherprovisions of EU Directives.32SIST EN 12953-6:2002
EN 12953-6:2002 (E)3ForewordThis document (EN 12953-6:2002) has been prepared by Technical Committee CEN/TC 269 "Shell and water-tubeboilers", the secretariat of which is held by DIN.This European Standard has been prepared under a mandate given to CEN by the European Commission and theEuropean Free Trade Association, and supports essential requirements of EU Directive(s).For relationship with EU Directive(s), see informative Annex ZA, which is an integral part of this standard.This European Standard shall be given the status of a national standard, either by publication of an identical text orby endorsement, at the latest by November 2002, and conflicting national standards shall be withdrawn at the latestby November 2002.The European Standard EN 12953 concerning shell boilers consists of the following Parts: Part 1:General. Part 2:Materials for pressure parts of boilers and accessories. Part 3:Design and calculation for pressure parts. Part 4:Workmanship and construction of pressure parts of the boiler. Part 5:Inspection during construction, documentation and marking of pressure parts of the boiler. Part 6:Requirements for equipment for the boiler. Part 7:Requirements for firing systems for liquid and gaseous fuels for the boiler. Part 8:Requirements for safeguards against excessive pressure. Part 9:Requirements for limiting devices of the boiler and accessories. Part 10:Requirements for boiler feedwater and boiler water quality. Part 11:Acceptance tests. Part 12:Requirements for firing systems for solid fuels for the boiler. Part 13:Operating instructions.CR 12953-14:Guidelines for the involvement of an inspection body independent of the manufacturer.Although these Parts can be obtained separately, it should be recognized that the Parts are inter-dependent. Assuch, the design and manufacture of shell boilers requires the application of more than one Part in order for therequirements of the standard to be satisfactorily fulfilled.Annex A is normative and Annexes B and C are informative.According to the CEN/CENELEC Internal Regulations, the national standards organizations of the followingcountries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland,France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain,Sweden, Switzerland and the United Kingdom.SIST EN 12953-6:2002
EN 12953-6:2002 (E)41 ScopeThis Part of this European Standard specifies requirements for safety related equipment for shell boilers as definedin EN 12953-1, irrespective of the degree of supervisions.2 Normative referencesThis European Standard incorporates by dated or undated reference, provisions from other publications. Thesenormative references are cited at the appropriate places in the text, and the publications are listed hereafter. Fordated references, subsequent amendments to or revisions of any of these publications apply to this EuropeanStandard only when incorporated in it by amendment or revision. For undated references the latest edition of thepublication referred to applies (including amendments).EN 12953-1, Shell boilers - Part 1: General.EN 12953-2, Shell boilers - Part 2: Materials for pressure parts of boilers and accessories.EN 12953-3:2002, Shell boilers - Part 3: Design and calculation for pressure parts.EN 12953-8:2001, Shell boilers - Part 8: Requirements for safeguards against excessive pressure.prEN 12953-9, Shell boilers - Part 9: Requirements for limiting devices and safety circuits of the boiler andaccessories.prEN 50156-1, Electrical equipment for furnaces and ancillary equipment - Part 1: Requirements for applicationdesign and installation.3 Terms and definitionsFor the purposes of this Part of this European Standard, the terms and definitions given in EN 12953-1 apply inaddition to the following.3.1controlsdevices used for maintaining the variable to be controlled (e.g. water level, pressure, temperature) at a specificvalue (set point)3.2limitersdevice that, on reaching a fixed value (e.g. pressure, temperature, flow, water level) is used to interrupt and lock-out the energy supply and lock-out requires manual unlocking before restart3.3independentability to function as required without dependence upon other equipment3.4lock-outisolation of energy supply which requires a manual intervention to reinstate3.5functional checktesting of the safety device to ensure it performs its intended function3.6electrically heated boilersboilers in which water is heated by an electric current flowing between electrodes or by immersion heatersSIST EN 12953-6:2002
EN 12953-6:2002 (E)53.7expansion vessels and tankscontainers to compensate for temperature dependent volume changes of the water expansion vessels are pressurised expansion tanks are not pressurised3.8allowable heat output of a hot water generatormaximum heat output (water mass flow times the difference between outlet and inlet enthalpy) that can be gener-ated during continuous operation and at which hot water generators can be operated3.9allowable flow temperaturehighest temperature, measured at the outlet branch at which the hot water generator can be operated (see 6.8.2.3)3.10maximum continuous rating (MCR)maximum continuous steam output that can be generated during continuous operation taking the specified steamcondition into consideration4 General requirements for steam boilers and hot water generators4.1 Safeguards against excessive pressureEach steam boiler and hot water generator, except open vented hot water generators, shall be equipped withsafeguards against excessive pressure in accordance with EN 12953-8.4.2 Materials for valves, fittings, flanges and boltingThe conditions and requirements to select the material shall be in accordance with
EN 12953-2.4.3 Limiting devices and safety circuits4.3.1All limiters and their installation shall be designed in accordance with prEN 12953-9. The electrical safetycircuits shall be in accordance with prEN 50156-1:1999, Table 1 and Annex B.4.3.2Functional checking of all limiters shall be possible at any time during operation e.g. by simulation whereappropriate.4.3.3If a limiter responds, a signal shall be given to indicate the reasons for boiler/generator malfunction.4.3.4After lock out, it shall only be possible to manually restart the boiler/generator from the boiler house.4.4 Temperature measurement of the furnace wallIf in accordance with EN 12953-3:2002, 5.4 it is established that temperature measurement of the furnace wall isnecessary, the temperature signal shall be transmitted to a temperature limiter. The limiting temperature shall bedetermined by the manufacturer.4.5 Heat supply4.5.1The heat supply shall be automatically controlled in relation to heat demand and the combustion processshall be completed within the furnace. In the event of shutdown, residual heat shall not cause unacceptable metaltemperatures (e.g. by evaporation of the water).SIST EN 12953-6:2002
EN 12953-6:2002 (E)64.5.2The design of the heat supply system and the boiler/generator shall ensure that no excessive evaporationof the water inside the boiler/generator occurs due to the heat accumulation in the combustion chamber and in theboiler/generator passes upon "cut off" of the heat supply.NOTEThis requirement is deemed to have been met for oil and gas firing systems: if it is proved that, after switching off the heat supply system from full load steady state condition, the flue gas temperatureat the highest point of the heated surface (HHS) falls to a value below 400 C before the water level has sunk from thelowest water level (LWL) to 50 mm above the highest point of the heated surface (HHS), or if adequate feed water is ensured (see 5.5).4.5.3Automatic start-up of the boiler/generator and the system shall be permitted provided that equipment isinstalled to ensure that start-up is conducted safely. Automatic restarting after normal shut-down shall not be con-sidered as a start-up.4.6 Flue-gas heated economizersEconomizers shall be fitted with a temperature indicating device on the water outlet, and each economizer that canbe isolated, shall be provided with a pressure gauge in addition to the safety pressure relief device (seeEN 12953-8:2001, 4.1.4).5 Special requirements for steam boilers5.1 Water level indication5.1.1Each steam boiler, except for low pressure boilers, shall have at least two independent means of indicatingthe water level, one of which shall be a gauge of transparent material directly connected to the boiler shell. Theother device may be a remote water level indicator or alternate device.For low pressure boilers only one direct water level indicator shall be required.5.1.2The gauge(s) of transparent material shall be mounted so that the water level is visible in the gauge glassat the lowest alarm level, i.e. at the lowest permissible water level (LWL) which shall be marked on the gaugeglass, and also at the maximum water level which shall be specified by the boiler manufacturer. The water levelindicating device shall be so arranged that the value "50 mm below LWL" is visible unless otherwise dictated by therequirements in 4.5.2.5.1.3The (LWL) of the boiler (see Figure 5.1-1), which shall be permanently and legibly marked on the boiler,visible at all times, and identified by the letters "LWL", shall be the greater of:a) 100 mm above the highest point of the heated surface "HHS"; orb) if the flue gas temperature exceeds 400 C, and the steam boiler has slow acting combustion equipment, aheight above "HHS" shall be fixed to allow for a sinking time of not less than 7 min.The sinking time t is the time during which the water level will sink from the lowest permissible water level to thehighest point of the heated surface in the case of complete loss of feedwater supply and at maximum continuousrating, i.e.t = V/(Qst v)(5.1-1)whereQstis the maximum continuous rating, in kg/min;Vis the water volume of the boiler between LWL and HHS, in m3;vis the specific volume of water, in m3/kg.SIST EN 12953-6:2002
EN 12953-6:2002 (E)7Key1
Controlled water level2
LWL3
HHSFigure 5.1-1 — Water level indication5.1.4Tubes and fittings connecting a water level gauge to a boiler shall be as short as possible and constructedso that no undrained pocket is formed between the boiler and the gauge. There shall be no outlet therefrom exceptfor regulators, steam pressure gauges and drains or other similar apparatus which does not permit the escape of asignificant amount of steam.Tubes connecting a water level gauge to the boiler shall be not less than 25 mm bore, but it may be reduced to20 mm at the connection with the gauges. Where the water gauge is fitted to the chamber of a safety control oralarm device, the connecting tubes to the boiler shall have a bore of not less than 40 mm.5.1.5Cylindrical water level gauge glasses shall be fitted with protectors.5.1.6Water level gauges shall be capable of isolation from the boiler and blowdown equipment. Where thevalves used are cocks, the flow direction shall be indicated.Blowdown equipment for water level gauges, regulators and limiters shall be so installed as to prevent accidents.5.2 Steam pressure and temperature indication5.2.1Each boiler shall have a steam pressure gauge, with a minimum dial diameter of 100 mm, connected to thesteam space either directly or through the water level gauge column or its steam connection.5.2.2The steam pressure gauge shall be connected to a siphon or similar device of sufficient capacity to keepthe gauge tube filled with water. The pipe shall be of sufficient size and should have provision for blowing through,if possible.5.2.3Steam pressure gauge connections shall be made suitable for the design working pressure of the boiler.5.2.4Pressure gauges shall be graduated to indicate the pressure in bars. The maximum allowable pressureshall be indicated by a fixed and readily visible red mark on the pressure gauge.SIST EN 12953-6:2002
EN 12953-6:2002 (E)8NOTEIn addition, the operating pressure and the safety valve set pressure can also be indicated.5.2.5Each boiler shall be provided with a valve connection for the special purpose of connecting a test gaugewhen the boiler is in service so that the accuracy of the boiler steam gauge can be ascertained.5.2.6Temperature measuring instruments shall be installed at the outlet of each superheater stage.5.3 Drain and blowdown devices5.3.1Each boiler shall be fitted with drain valves placed at, or as near as practicable to, the lowest point of theapparatus.NOTEOn some boilers, drain valves can be used for blowdown purposes.5.3.2Where drain valves from two or more boilers are connected to a common discharge, two valves shall befitted to each drain line, one being of a non-return type to prevent the contents of one boiler passing to another.5.3.3The drain pipe between the apparatus and the drain valve shall, if exposed to furnace heat, be protected bybrickwork or other heat-resisting material so arranged that the pipe may be inspected and is not constrainedagainst expansion.5.3.4Taper-plug valves where fitted, shall be of the bolted cover type with separately packed glands and shallnot be used with design pressures over 13 bar.5.3.5Where drain valves are not self closing or capable of being locked in the closed position, a further shut-offdevice shall be installed in the line.5.4 Valves for connections5.4.1 Steam outletsThe stop valve connecting the boiler to the steam pipe shall be attached directly to the boiler. In the case of a boilerwith a superheater, the stop valve shall be located at the outlet from the superheater header. The valve shouldpreferably be of a type which positively indicates whether it is open or closed.Where more than one boiler is connected to a common header or steam manifold, the steam connections for eachboiler shall be provided with two stop valves, one of which shall be of the non-return type, with a free blowing drainbetween them.NOTEIt is preferable that the valve nearest the boiler be a non-return type.5.4.2 Feed connectionsEach feed pipe to any boiler shall be provided with a non-return valve and a separate stop valve near the boiler.Where there is an integral economiser, the foregoing valves shall be placed at the inlet to the economiser.If the stop valve and non-return valve are not installed in direct connection to each other, it shall be possible torelieve the pressure in the interconnecting piping.The feed line and internal pipe connection to the boiler shall be so arranged that in the case of leakage of the non-return valve, the boiler cannot empty itself to a level less than 50 mm above the highest point of the heating surfacecontaining gases at a temperature of more than 400 °C.In the event of backflow through a feed pump, where the suction pipework is of a lower pressure rating than thedischarge line, then pressure gauges shall be installed to clearly indicate the pressure head. Also, a warning noticeshall be provided indicating the possible dangers of closing an isolating valve (if fitted) in the suction line.SIST EN 12953-6:2002
EN 12953-6:2002 (E)95.5 Feed water supplyThe boiler shall be provided with an adequate supply of feed water. Where feed water supply shall be ensured asrequired in 4.5.2, two feed water supplies shall be provided.5.6 Feed water control5.6.1 The water level shall be controlled automatically.5.6.2One automatic device shall be provided to prevent the maximum water level from being exceeded. Thisdevice does not have to be an additional device. Where the feedwater supply is interrupted, the heat supply shallbe cut off simultaneously if the economisers are endangered due to the interrupted feed.5.6.3It shall be ensured that no harmful matter (oil, grease, seawater etc.) can enter the feed water or boilersystem.5.7 Limiting devices5.7.1 Low water protectionTwo independent (both mechanically and electrically) water level limiters shall be provided to cut off and lock outthe heat supply when the water level falls to the "LWL" position.NOTEIt is not necessary for both limiters to act simultaneously.5.7.2 Pressure and temperature limitationFor all boilers, a pressure limiter shall be provided to cut off and lock out the heat supply to ensure that theallowable pressure is not exceeded.Where a control in accordance with 5.8.2 is required, a temperature limiter shall be provided to cut-off and lock outthe heat supply to ensure that the allowable metal temperature is not exceeded.5.8 Heat supply5.8.1The pressure of each boiler shall be controlled automatically by regulating the heat input.5.8.2The superheated steam temperature shall be controlled automatically unless the design metal temperatureis higher than the maximum attainable metal temperature.5.9 Electrically-heated boilers5.9.1 Steam boilers heated by electric current flowing between electrodesAll the requirements of clause 5 shall apply except
5.4.2 paragraph 3, 5.5, 5.7.1 and 5.8.2.Contrary to 5.1.1, only one means of indicating the water level is sufficient.5.9.2 Steam boilers heated by immersion heaters5.9.2.1All the requirements of clause 5 shall apply except for 5.4.2 paragraph 3 and 5.1.3, where the waterlevel shall not be allowed to fall below the uppermost surface of the immersion heaters.Contrary to 5.1.1, only one means of indicating the water level is sufficient.SIST EN 12953-6:2002
EN 12953-6:2002 (E)105.9.2.2The lowest water level (LWL) as defined in 5.1.3 shall be 30 mm above the uppermost surface of theimmersion heaters.Contrary to 5.7.1, only one safety device is sufficient.6 Special requirements for hot water generators6.1 Hot water generating systems (for example see Annex A)6.1.1Open vented systems shall be
directly connected to the atmosphere (see Figures A.3-1 and A.3-2)6.1.2Closed systems shall not be connected to the atmosphere. They are subdivided into:a) internally pressurised systems where the pressure is generated by the saturation pressure corresponding tothe flow temperature (see Figures A.3-3 and A.3-4);andb) externally pressurised systems where the pressure is generated by such systems as gas cushions, pressurepumps, or external steam cushions (see Figures A.4-1 to A.4-5).6.1.3The heated water is normally used in a closed cycle, but if steam discharge is intended, clause 5 shall ad-ditionally apply.In the case of steam discharge, the pressure shall also be held under all operating conditions.6.1.4If required, provision shall be made that the temperature of the water returned to the hot water generatordoes not fall below a value to be determined by the manufacturer, except for start up and shut down.6.1.5Each hot water generator system shall be provided with an expansion space which shall be dimensioned inaccordance with Annex B, and shall be capable of compensating temperature-dependent volume changes in hotwater generating plant and the heat dissipation system to stay within the design limits. A separate expansion vesselor tank shall be used unless the steam space in the hot water generator is used as the expansion vessel. The plantand particularly these expansion vessels or tanks, including their lines, shall be protected against freezing.6.1.6The system shall be equipped with a protective device against back flow (non-return valves) and a shut-offdevice. The same shall apply to the make-up water line.Where a shut-off device is installed between the hot water generator and the expansion vessel, it shall be capableof being locked in the open position.6.2 Expansion and feed lines for open vented systemsTo ensure safe operation of the generator the internal diameter of the feed and expansion lines shall be determinedby the following (see also Figure 6.2-1):Dimensions shall be deemed adequate if the internal diameter, di of the feed and expansion lines is determined bythe following:expansion line:hi397,115Qd(6.2-1)feed line:hi9273,015Qd(6.2-2)whereQh is the heat output from the boiler, in kWIn the case of a combined feed/expansion line the following formula shall be used:SIST EN 12953-6:2002
EN 12953-6:2002 (E)11combined: )397,115(25,1hiQd(6.2-3)In no case shall the internal diameter di be less than 25 mm.Vent lines shall be protected against blockage and freezing.Key1
Expansion line2
Make-up water-line3
Combined feed and expansion line4
Flow-line5
Return-line6
feed lineFigure 6.2-1 — Open vented system6.3 Water supply6.3.1The generator system shall be provided with an adequate supply of water.6.3.2If the possibility exists that harmful matter (oil, grease, seawater, etc) may enter the water circulating sys-tems, thus endangering the hot water generator, the quality of the water returning to the hot water generator shallbe monitored.6.4 Circulating pumps6.4.1Circulating pump(s) shall be provided to maintain circulation.6.4.2For
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