1、Copyright ASME International Provided by IHS under license with ASMENot for ResaleNo reproduction or networking permitted without license from IHS-,-The American Society of Mechanical Engineers AN AMERICAN NATIONAL STANDARD RECOPi1MENDED PRACTIIES FOR THE PREVENTION OF WATER DAMAEE TO STEAM TURBINES
2、 USED FOR ELECTRII: POWER GENERATION ASME TDP-1-1998 (Revision 01 ANSVASME TDP-1-1185) FOSSIL FUELED PLANTS Copyright ASME International Provided by IHS under license with ASMENot for ResaleNo reproduction or networking permitted without license from IHS-,-Date of Issuance: January 29, 1999 This Sta
3、ndard will be revised when the Society approves the issuance of a new edition. There will be no addenda or written interpretations of the requirements of this Standard issued to this edition. ASME is the registered trademark of The American Society of Mechanical Engineers. This code or standard was
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9、d in any form, in an electronic retrieval system or otherwise, without the prior written permission of the publisher. The American Society of Mechanical Engineers Three Park Avenue, New York, NY 10016-5990 Copyright Q 1999 by THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS All Rights Reserved Printed i
10、n U.S.A. Copyright ASME International Provided by IHS under license with ASMENot for ResaleNo reproduction or networking permitted without license from IHS-,-FOREWORD (This Foreword is not a part of ASME TDP-1-1998) A substantial increase in the number of reported occurrences of steam turbine damage
11、 by water induction precipitated design recommendations from the two major domestic turbine manufacturers as an attempt to reduce such incidents. Concurrently, utilities and designers began formulating their own design criteria because of the economic need to keep the generating units in service. Re
12、alizing the common need for a uniform set of design criteria to alleviate this problem, an ASME Standards Committee was formed, consisting of representatives of utilities, equipment manufacturers, and design consultants, to develop recommended practices for use in the electric generating industry. T
13、his Standard, resulting from the work and deliberation of the Turbine Water Damage Prevention Committee, was approved as a standard of The American Society of Mechanical Engineers by the ASME Standardization Committee and the ASME Policy Board, Codes and Standards on July 26, 1972. In 1979, the Comm
14、ittee proposed a revision to this ASME Standard to include information on condenser steam and water dumps, direct contact feedwater heaters, and steam generators. This proposed revision was approved by the ASME Standardization Committee on April 25, 1980. The last revision was approved as an America
15、n National Standard on September 13, 1985. In 1994 the ASME Board on Standardization approved the disbandment of the Committee on Turbine Water Damage Prevention, and the withdrawal of the standard TDP-1. This was due to a perceived lack of interesduse by the industry. Subsequent interest from users
16、 and potential users for TDP-1 convinced ASME to reconstitute the Committee under the Board on Pressure Technology Codes and Standards in June of 1997. The current document was approved as an American National Standard on June 17, 1998. iii Copyright ASME International Provided by IHS under license
17、with ASMENot for ResaleNo reproduction or networking permitted without license from IHS-,-ASME STANDARDS COMMITTEE TWDP Turbine Water Damage Prevention (The following is the roster of the Committee at the time of approval of this Standard.) OFFICERS R. G. Narula, Chair L. A. Kielasa, Vice Chair A. J
18、. Roby. Secretary COMMITTEE PERSONNEL J. C. Boyle, Stone reheat steam systems, piping, and drains; reheat attemperating system; turbine extraction systems, piping, and drains; feedwater heaters, piping, and drains; turbine drain system; turbine steam seal system, piping, and drains; main steam attem
19、perator sprays; start-up systems; condenser steam and water dumps. Any connection to the turbine is a potential source of water either by induction from external equipment or by accumulation of condensed steam. The sources treated specifically are those that have been found to be most frequently inv
20、olved. 2 CRITERIA 2.1 Recommendations Design, control, and operation of all systems that have a potential for allowing water to enter the turbine should prevent any unusual accumulations. However, since malfunctions do occur, the recommendations for preventing turbine damage due to water induction i
21、n- clude one or more of the following where appropriate: (a) detection of the presence of water either in the turbine or, preferably, external to the turbine before the water has caused damage; (b) isolation of the water by manual or, preferably, automatic means after it has been detected; (c) dispo
22、sal of the water by either manual or, prefera- bly, automatic means after it has been detected. 2.2 Failure Where experience has shown a source of water is particularly hazardous, no single failure of equipment should result in water entering the turbine. The failure mode of the various devices used
23、 to prevent water induction should be considered so that a single failure of the signals (loss of air or electrical signal) will not cause water to enter the turbine. 3 DESIGN RECOMMENDATIONS This Section outlines specific recommendations for the design of the systems listed. These recommendations a
24、re intended to represent a conservative design for protection from water induction. There is no intention to supersede any existing codes or governmental regula- tions. 3.1 Steam Generators 3.1.1 It is the responsibility of the plant designers to review and understand the design features of the stea
25、m generator and of the user to adhere to the operating procedures of the steam generator manufacturer as a precaution against water induction. The majority of the incidents of turbine water damage caused by water entering the turbine from the steam system have oc- curred during start-up or shutdown
26、of a unit. The steam generator manufacturers design and operating recommendations should include the required protection to prevent the induction of water into the main steam piping. Such areas as superheater attemperators, boiler start-up systems, high drum levels, and undrained super- heaters are
27、some potential sources of water. 3.1.2 Experience has shown that once-through flow units, because of their start-up system, offer a greater potential for water induction through the main steam system during start-up and shutdown operating modes Copyright ASME International Provided by IHS under lice
28、nse with ASMENot for ResaleNo reproduction or networking permitted without license from IHS-,-ASME TDP-1-1998 PREVENTION OF WATER DAMAGE TO STEAM TURBINES USED FOR ELECTRIC POWER GENERATION than do drum type steam generators. It is recommended that the start-up system on once-through units be de- si
29、gned so that no single failure of equipment can result in water entering the main steam line. Therefore, two of the following independent means of automatically preventing water from entering the main steam lines from the start-up system should be provided: (U) the automatic opening of the drain sys
30、tem to the condenser from the start-up system flash tank or separator on detection of high level; (b) automatic closing of the shutoff valve in the line from the start-up system to the main steam system on detection of high-hi level in the flash tank or separator; (c) automatic shutoff of all source
31、s of water entering the start-up system by either tripping all feed pumps or closing a shutoff valve on detection of high-hi level in the flash tank or separator. Typical systems are shown in Figs. I and 2. 3.1.2.1 Figure 1 showsa primary drain line from the flash tank or separator with its associat
32、ed level sensor and an independent automatically operated shutoff valve between the flash tank and the main steam system. The shutoff valve will be actuated by a high-hi level from an independent level signal. The drain line valve and the shutoff valve should have indicators in the control room for
33、the open and closed positions. 3.1.2.2 Figure 2 shows a primary drain line from the flash tank or separator with its associated level sensor and an independent trip signal to the feedwater supply source. The trip signal will be actuated by a high-hi level from an independent level signal. The drain
34、line valve and feedwater shutoff valve (if used) should have indicators in the control room for the open and closed positions. 3.1.3 It is recommended that start-up systems on other than once-through units (such as drum type) be designed so that no single failure of equipment can result in water ent
35、ering the main steam line. The method of accomplishing this should be as determined by the designer. 3.2 Superheat Attemperator 3.2.1 Spray water injected in the steam generator ahead of the finai superheat section is a means to control steam temperature at the outlet of the superheater. These spray
36、s are generally not effective in controlling final superheat steam temperature at low loads or during turbine rolling. The opportunity exists for water to accumulate in the pendant elements of the superheater during low load operation from either condensation or overspraying. Units which have to ope
37、rate for extended periods of time with the spray header system charged to full pump discharge pressure (e.g., during start-up and shut-down conditions) are subject to possible leakage of the spray valves. Such leakage can result in water accumulating in the pendant superheater sections and may even
38、flow over into the main steam system. When steam flow is increased, this accumulation of water can be injected into the turbine. 3.2.2 A power-operated block valve should be installed in series with the attemperator spray control valve. This valve provides tight shutoff to prevent water leakage past
39、 the spray control valve and provides a backup in the event that the spray control valve fails to close when required (see Fig. 3). The spray control and block valves constitute a double line of defense against the inadvertent introduction of spray water into the main steam system. 3.2.3 The control
40、 system should automatically close and override all manual and automatic setting of the superheat spray control and block valves when the master fuel trip actuates or the turbine trips. 3.2.4 The block valve should be automatically closed when the unit is operated below a predetermined load and, sim
41、ultaneously, the control valve is closed. Superheat spray should not be released for automatic control at loads where it can be determined that it is relatively ineffective in reducing final superheater temperature. The loads used should be in accordance with the boiler manufacturers recommendations
42、. Man- ual control of spray below the predetermined load should only be used with close operator supervision. Manual control must not prevent the automatic protec- tion features specified in para. 3.2.3 from operating in the event the master fuel trip actuates or the turbine trips. 3.2.5 The control
43、 system. for opening the spray control valve should be designed to prevent the sudden injection of large quantities of water. 3.2.6 A bypass valve around the spray control valves should be power-operated and actuated to close when the block valve is closed. If a manual bypass is used, a second power
44、-operated block valve should be provided to give a second line of defense. 2 Copyright ASME International Provided by IHS under license with ASMENot for ResaleNo reproduction or networking permitted without license from IHS-,-PREVENTION OF WATER DAMAGE TO STEAM TURBINES USED FOR ELECTRIC POWER GENER
45、ATION ASME TDP-1-1998 FIG. 1 TYPICAL FLASH TANK/SEPARATORS ARRANGEMENT 3.2.7 A bypass of a block valve should not be should not be considered as devices which will prevent water induction into the turbine from the main steam line. provided under any circumstances. 3.3 Main Steam Piping The procedure
46、 recommended in this Section is to prevent the accumulation of water in the main steam piping. 3.3.1 Because of the lack of detection instrumenta- tion that will close the turbine stop valves in time to prevent damage when the turbine is in operation, there are no recommendations included pertaining
47、 to the prevention of damage by water passing through the main steam piping and into the turbine. If such devices are developed and marketed, consideration should be given to include this instrumentation. Turbine valves 3.3.2 A drain should be installed at each low point in the main steam piping fro
48、m the boiler outlet to the connection on the turbine stop valve. When reviewing the location of low points, consideration should be given to the position of the piping in both the cold and hot position. Where there is no specific low point (where there are long runs of horizontal piping), install a
49、low point drain at the turbine end of this Section. If the main steam line is split into more than one branch going into the turbine, each of these branches as well as the main header should be reviewed for low points. In addition, a connection should be located 3 Copyright ASME International Provided by IHS under license with ASMENot for ResaleNo reproduction or networking permitted without license from IHS-,-ASME TDP-1-1998 PREVENTION OF WATER DAMAGE TO ST
