BS DD IEC TS 61370-2002 Steam turbines - Steam purity《蒸汽轮机 蒸汽纯度》.pdf

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1、DRAFT FOR DEVELOPMENT DD IEC TS 61370:2002 Steam turbines Steam purity ICS 27.040 DD IEC TS 61370:2002 This Draft for Development, having been prepared under the direction of the Engineering Sector Policy and Strategy Committee, was published under the authority of the Standards Policy and Strategy

2、Committee on 26 July 2002 BSI 26 July 2002 ISBN 0 580 40111 1 National foreword This Draft for Development is the English language version of IEC TS 61370:2002. This publication is not to be regarded as a British Standard. It is being issued in the Draft for Development series of publications and is

3、 of a provisional nature because it was not possible to obtain the necessary support for the production of an International Standard at this time but it was considered important that the information included should be made available for general use as quickly as possible. It should be applied on thi

4、s provisional basis, so that information and experience of its practical application may be obtained. Comments arising from the use of this Draft for Development are requested so that UK experience can be reported to the international organization responsible for the Technical Specification. A revie

5、w of this publication will be initiated not later than 3 years after its publication by the international organization so that a decision can be taken on its status at the end of its 3-year life. Notification of the start of the review period will be made in an announcement in the appropriate issue

6、of Updated Standard. According to the replies received by the end of the review period, the responsible BSI Committee will decide whether to support the conversion into an international standard, to extend the life of the Technical Specification for another 3 years or to withdraw it. Comments should

7、 be sent in writing to the Secretary of BSI Technical Committee MCE/13, Steam turbines, at 389 Chiswick High Road, London W4 4AL, giving the document reference and clause number and proposing, where possible, an appropriate revision of the text. A list of organizations represented on this committee

8、can be obtained on request to its secretary. From 1 January 1997, all IEC publications have the number 60000 added to the old number. For instance, IEC 27-1 has been renumbered as IEC 60027-1. For a period of time during the change over from one numbering system to the other, publications may contai

9、n identifiers from both systems Cross-references The British Standards which implement international publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Ele

10、ctronic Catalogue or of British Standards Online. Summary of pages This document comprises a front cover, an inside front cover, the IEC TS title page, pages 2 to 17 and a back cover. The BSI copyright date displayed in this document indicates when the document was last issued. Amendments issued sin

11、ce publication Amd. No. Date CommentsSPCIFICATION TECHNIQUE CEI IEC TECHNICAL SPECIFICATION TS 61370 Premire dition First edition 2002-06 Turbines vapeur Puret de la vapeur Steam turbines Steam purity Numro de rfrence Reference number CEI/IEC/TS 61370:2002 DDIECTS61370:2002CONTENTS FOREWORD.3 1 Scop

12、e.5 2 Abbreviated terms.6 3 Need for steam purity control 6 3.1 Corrosion and loss of efficiency or output.6 3.2 Categories of plant 6 3.2.1 Reheat and non-reheat plants 6 3.2.2 Primary source of energy .6 3.3 Operating regimes .7 3.3.1 Start-up .7 3.3.2 Volatile chemical-based treatments7 3.3.3 Sol

13、id chemical-based treatments8 4 Sampling and analysis 8 4.1 Sampling locations 8 4.2 Measured parameters9 4.2.1 Cation conductivity.9 4.2.2 Sodium 9 4.2.3 Silica .9 4.3 Significance of parameters 11 4.3.1 Cation conductivity.11 4.3.2 Sodium 11 4.3.3 Silica .11 4.3.4 Chloride.11 4.3.5 Sulphate 12 4.3

14、.6 Iron and copper .12 4.3.7 Alternative additives.12 Annex A (informative) Guideline values 13 Bibliography17 Figure 1 Silica contents in saturated steam and boiler water .10 Table A.1 Steam purity limits for steam turbines Key parameters .14 Table A.2 Steam purity limits for steam turbines Diagnos

15、tic parameters.15 Table A.3 Actions on deviations from guidelines .16 DDIECTS61370:20022INTERNATIONAL ELECTROTECHNICAL COMMISSION _ STEAM TURBINES STEAM PURITY FOREWORD 1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising all national elec

16、trotechnical committees (IEC National Committees). The object of the IEC is to promote international co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and in addition to other activities, the IEC publishes International Standards. Their pre

17、paration is entrusted to technical committees; any IEC National Committee interested in the subject dealt with may participate in this preparatory work. International, governmental and non-governmental organizations liaising with the IEC also participate in this preparation. The IEC collaborates clo

18、sely with the International Organization for Standardization (ISO) in accordance with conditions determined by agreement between the two organizations. 2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an international consensus of opinion on the r

19、elevant subjects since each technical committee has representation from all interested National Committees. 3) The documents produced have the form of recommendations for international use and are published in the form of standards, technical specifications, technical reports or guides and they are

20、accepted by the National Committees in that sense. 4) In order to promote international unification, IEC National Committees undertake to apply IEC International Standards transparently to the maximum extent possible in their national and regional standards. Any divergence between the IEC Standard a

21、nd the corresponding national or regional standard shall be clearly indicated in the latter. 5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any equipment declared to be in conformity with one of its standards. 6) Attention is drawn to the pos

22、sibility that some of the elements of this technical specification may be the subject of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights. The main task of IEC technical committees is to prepare International Standards. In exceptional circumstances,

23、a technical committee may propose the publication of a technical specification when the required support cannot be obtained for the publication of an International Standard, despite repeated efforts, or the subject is still under technical development or where, for any other reason, there is the fut

24、ure but no immediate possibility of an agreement on an International Standard. Technical specifications are subject to review within three years of publication to decide whether they can be transformed into International Standards. IEC 61370, which is a technical specification, has been prepared by

25、IEC technical committee 5: Steam turbines. The text of this technical specification is based on the following documents: Enquiry draft Report on voting 5/133/DTS 5/138/RVC Full information on the voting for the approval of this technical specification can be found in the report on voting indicated i

26、n the above table. This publication has been drafted in accordance with the ISO/IEC Directives, Part 3. Annex A is for information only. DDIECTS61370:20023The committee has decided that the contents of this publication will remain unchanged until 2005. At this date, the publication will be reconfirm

27、ed; withdrawn; replaced by a revised edition, or amended. DDIECTS61370:20024STEAM TURBINES STEAM PURITY 1 Scope This technical specification describes the importance of the chemical characteristics of steam supplied to steam turbines and the need to prevent corrosion and deposition in steam space, i

28、n order to minimize the risk of turbine corrosion failures or loss of efficiency or output. The significance of relevant chemical parameters, mostly related to impurity levels, is discussed in terms of types of plant and chemistry operating regimes. This specification is applicable to turbines of al

29、l electrical output rating and any exhaust condition, i.e. condensing or back pressure. However, the range of application in terms of output rating or steam pressure is dictated by economic factors such as the relative cost of monitoring equipment and turbine plant. It is designed for new plant, but

30、 may be adapted for use on existing plant. The limits described in this specification are specifically designed to protect the steam turbine. The user should also be aware of steam purity requirements imposed by other considerations such as components of the boiler or steam generator. This specifica

31、tion is applicable to steam turbines driven from any source, except geothermal plants in which the turbine is fed direct from the geothermal sources. After the initial start of the turbine it may take some months for best achievable chemistry to be reached. This tends to be achieved sooner for some

32、parameters (sodium, cation conductivity) than for others (silica, iron, copper). It is therefore recognized that during commissioning, it may be difficult to meet normal targets, but a steady improvement should be observed as the steam cleans up. Annex A provides recommended guidelines for this spec

33、ification and verification of the chemical purity of steam entering a steam turbine, in order to maintain the integrity and efficiency of the turbine. The limits stated are not intended to be mandatory, but to be used as the basis for local instructions for individual plant. Verification is addresse

34、d as the selection of appropriate sampling locations and continuously or intermittently measured parameters. DDIECTS61370:200252 Abbreviated terms For the purposes of this technical specification, the following abbreviated terms are used: AVT all volatile treatment BWR boiling water reactor c.con ca

35、tion conductivity CT caustic treatment EPT equilibrium phosphate treatment FAC flow accelerated corrosion IWC International Water Conference OT oxygenated treatment PT phosphate treatment PWR pressurized water reactor 3 Need for steam purity control 3.1 Corrosion and loss of efficiency or output Hig

36、h purity steam is required to ensure steam turbine operation with a high degree of efficiency, output, and availability. Impurities can form deposits, which can lead to loss of efficiency or output or to corrosion. Corrosion can potentially lead to total failure of rotating components. Conditions in

37、 expanding steam are such that even a low concentration of an impurity can coexist with a small quantity at high concentration in moisture over a narrow range of temperature and pressure conditions, which may coincide with the surface of a turbine component. It is therefore desirable to minimize the

38、 content of impurities. The levels recommended in this specification are established as achievable, measurable and consistent with a high level of efficiency, output and availability. 3.2 Categories of plant 3.2.1 Reheat and non-reheat plants The live steam limits are applicable to machines both wit

39、h and without reheat. However, the different implications for impurities in these two types of plant should be appreciated. In non-reheat fossil-fuel-fired machines, the temperature of the first condensation within the low-pressure (LP) stages tends to be at a higher temperature than in units with r

40、eheat. Thus, the associated risk of corrosion tends to be higher. In units with reheat, there is a tendency for some species to deposit in the reheater and for a slightly better standard of purity to be expected in hot reheat steam than in live steam. 3.2.2 Primary source of energy Tables A.1 to A.3

41、 do not distinguish between primary sources of energy, i.e. whether fossil- fuel-fired or nuclear. However, PWR and BWR plants differ in that steam enters the turbine in saturated condition. Also, some BWR systems operate under an enforced oxygenated neutral condition similar to the OT option for fe

42、edwater treatment. DDIECTS61370:200263.3 Operating regimes 3.3.1 Start-up The values defined in tables A.1 and A.2 apply under normal steady load. More relaxed limits may be applied for a limited time at start-up. This allows a reasonable loading of impurities on the steam turbine without excessive

43、start-up times. When a plant undergoes two-shifting, the time occupied by start-ups is higher. It may therefore be appropriate to impose a limit on annual accumulated time occupied by the relaxed start-up limits. The decision whether to impose such a limit would be decided locally by the user. Some

44、guidance is available in the bibliography. 3.3.2 Volatile chemical-based treatments 3.3.2.1 General Under these regimes, only volatile treatment chemicals are used. They are typically injected into condensate or feedwater. Ammonia or volatile amines are used for pH control. Hydrazine, organic-based

45、oxygen scavengers or oxidants are used for control of redox potential. Volatile chemical-based treatments do not provide pH buffer against acidic contaminants either in boilers or in turbines. For this reason, the control limits for cation conductivity, chlorides and sulphates in boiler water are at

46、 least of an order of magnitude below those of solid alkali-based treatments to ensure the same cycle corrosion protection. Volatile chemical-based treatments are used in units where the steam generation process may result in local dry-outs, and hence uncontrolled local concentration of solids, in b

47、oilers. 3.3.2.2 All volatile treatment (AVT) AVT is characterized by reducing conditions in the condensate/feedwater systems. Oxygen is first removed mechanically by vacuum and steam in condensers and de-aerators respectively. In addition, volatile reducing chemicals or organic-based oxygen scavenge

48、rs are added to remove traces of oxygen. 3.3.2.3 Oxygenated treatment (OT) OT is characterized by oxidizing conditions in the condensate/feedwater systems. Oxidizing conditions are achieved with a control of oxygen concentration within a range of approximately 50 g/kg to 200 g/kg. Oxygen is injected

49、 either in the form of pure oxygen, as a component of air or in hydrogen peroxide. OT is most commonly used with once-through boiler systems. A volatile feedwater pH control additive is usually added, but at a lower concentration than in AVT. OT also has the advantage of inhibiting FAC. 3.3.2.4 Boiling water reactor (BWR) In BWR plants, the steam is neutral and contains a high concentration of oxygen due to radiolysis. In some BWR plants, hydrogen is