If the total free float of the rotor without thrust bearing installed is 4. In current practice, turbine startup limitations are set by consideration of thermal stress and low cycle fatigue. Topel et al 29 used simplified fe models to analyse the transient startup of steam turbines in the context of natural convection heat transfer causing differential thermal expansion of the gas. Reducing cycling damage to combined cycle steam turbines. Steam turbine differential expansion cr4 discussion thread. New issues manifesting from increased unit cycling and turndown will also be discussed along with the pitfalls of associ. Steam turbine thermal modeling for improved transient. In its simplest form, a steam turbine consist of a boiler steam generator, turbine, condenser, feed pump and a variety of auxiliary devices. The turbine supervisory instrumentation or tsi includes those measurements which monitor the behavior of the rotor train assembly. Design and analysis of highpressure casing of a steam turbine. This measurement is typically performed on larger steam. For hp differential expansion we are using direct differential expansion probe, and for lp differential expansion we are using. Units with different steam turbines for stag combinedcycle power systems m. Differential expansion monitoring measures the change in axial clearances between the machine rotor and casing caused by thermal changes inherent in most machines.
Plotted on a mollier diagram it provides a useful visual image of these conditions. Title startup of steam turbine and its auxiliaries 2. The first steam turbine used for power generation was invented in 1884. This property is the differential axial expansion and is defined as the difference of thermal expansion between the rotating and stationary. Unesco eolss sample chapters thermal power plants steam turbine components and systems r. When turbine is in service, superheated steam temperature above 540 degree celsius is admitted into the turbine. Prior to supplying steam to the turbine, the steam supply pipelines have to be drained and heated up. Steam turbine technology supports our modern life and important industrial activities in present society. A steam turbine is a device that extracts thermal energy from pressurized steam and uses it to do mechanical work on a rotating output shaft.
In case of turbines with cooling water preheating and lowpressure lp bypass, prior to supplying steam the regeneration and dumping systems have to be. Both of those abnormal conditions are covered in our manuals and the temperature parameters are identified. In order to improve the startup flexibility of steam turbines, it becomes relevant to analyze their dynamic thermal behavior. A consequence of excessive thermal expansion is rotor rubbing. In an extracting type turbine, steam is released from variousin an extracting type turbine, steam is released from various stages of the turbine, and used for industrial process needs or sentstages. Tsi aims at monitor safe and reasonable steam turbine operation. Ger3582e steam turbines for stag combinedcycle power systems. Thermal power plants steam turbine components and systems r. Maintenance and overhaul of steam turbines wgp42 05. The steam turbine thermal transient model st3m tool developed at kth. Differential expansion tcm 1221465 free download as pdf file. We are commissioning this turbine for the first time.
Validating and modeling of steam turbine temperature distribution. Ger3582e steam turbines for stag combinedcycle power. The extremely large casing sizes and extremely high steam temperatures of turbines used in electric power generation service can easily result in up to two inches 50 mm of axial growth. Higher load more cooling and less back pressure lower steam temps means a shorter turbine.
Differential expansion on a turbine is the relative measurement of the rotors axial thermal growth. Instruction manual for single stage 350, 500, and 700 frame. This application note discusses the principles behind the differential expansion measurement itself. This was developed by kraftwerk union and also overcomes the need for a very heavy flange in the high pressure cylinder.
Pdf design and analysis of highpressure casing of a steam. Based on the premise that the probability distribution of random parameters has been known, the differential expansion of steam turbine is analyzed by saddlepoint. Gt load 50mw for cold start up conditions gt load 65 mw for warmhot start up st on turning gear minimum 6 hrs one cep in service one cw pump in service st turning gear operation f. The torsional load on single components like shafts or turbine blades might exceed a specified value and fail. Warning a complete reading of this manual by personnel in contact with the steam turbine is essential to safety. Request pdf differential expansion sensitivity studies during steam turbine startup in order to improve the startup flexibility of steam turbines, it becomes. Approval issue course 234 turbine add auxiliaries module one turbine steam pressure profile at partial loads, steam flow to the turbine is throttled by the governor valves. In its simplest form, a steam turbine consist of a boiler steam generator, turbine, condenser, feed. While there are multiple connotations for the term differential expansion in the context of a steam turbine, it is predominantly a reference to the thermally. Steam turbines have a known thermal expansion, where. What is differential or relative expansion in steam turbine. Steam turbine differential expansion amp maintenance forums. Range perform startup of steam turbine and its auxiliaries in general industrial plants, power plants or other places.
Turbine troubleshooting and repair methods tom reid, manager of engineering, tg advisers this presentation will introduce effective steam turbine troubleshooting strategies and highlight cost effective repair strategies. Steam turbine rotor vibration that results in premature failure of blades and other components is one of the most serious problems in power plant operations. Steam conditions the turbine expansion line or condition curve represents steam conditions prevailing in sequential stages of the steam turbine. The studies performed serve as a base towards further understanding the differential expansion during start and establishing future clearance control strategies during turbine transient operation. Steam turbine thermal modeling for improved transient operation. Differential expansion of the steam turbine cr4 discussion. Differentialrotor expansion sti vibration monitoring inc. Its modern manifestation was invented by charles parsons in 1884 the steam turbine is a form of heat engine that. Likewise, it undergoes contraction as its case cools during steam reduction. Cycling combined cycle power plants places additional stresses on all equipment including the gas turbine, heat recovery steam generator, and steam turbines. Concerning the steam turbine st component, one key aspect of its flexibility is the capability for fast starts. Improvements of up to 30% were accounted to this measure.
Differential expansion differential expansion monitoring measures. These include the speed, vibrations, axial position and differential expansion of the turbo set. Common techniques for measuring large differential expansion ranges include extended range. Differential expansion sensitivity studies during steam turbine startup article in journal of engineering for gas turbines and power 86 september 2015 with 352 reads how we measure reads. A steam turbine locomotive engine is a steam locomotive driven by a steam turbine. The first steam turbine rail locomotive was built in 1908 for the officine meccaniche miani silvestri grodona comi, milan, italy. Proceedings of the asme turbo expo, montreal, canada. The system can be damaged, which has harmful effects on the entire power plant. Differential measurement for large steam turbines with long shaft systems, an additional axial position. Turbine supervisory instrument tsi instrumentation and. What is differential expansion in steam turbine answers. The steam turbines principle is that the steam energy is converted into mechanical energy by expansion through the turbine.
Investigation into the thermal limitations of steam. With todays steam turbine arrangements exceeding the 900mw barrier this measurement is as relevant as ever and a continuing challenge. We are using bently nevada 3300 xl 25 mm transducer. An increase in differential expansion may be caused by too fast a change in inlet steam temperature or due to too rapid change in steam flow to the turbine. Both the ends are supported on independent pedestals. In addition, other relevant thermal processes within a steam turbine are those of gland steam sealing and losses due to friction and fanning. The methods of calculating turbine axial differential expansion online and controlling axial differential expansion by c changing steam temperature increment were investigated. Steam turbines are widely used for combined heat and power chp applications in the united states and europe. The steam turbine plays an important role in the thermal power plant.
Based on saddlepoint approximation method and sensitivity analysis method, reliability sensitivity analysis for differential expansion of steam turbine with random parameters are studied. The temperature of various turbine compo nents can change considerably as the turbine is started and loaded causing radial differential expansion. Article from skf turbine supervisory instrumentation differential expansion rotor expansion the effect of casing and rotor expansion. Steam turbines startups 1 principles of steam turbines startups. Differential expansion sensitivity studies during steam turbine. Each time it starts, the turbine after rolling about 2 or 3 hours differential expansion reach to its limit 1mm, and turbine trips, we have scyncronizing and reaching to 20mw during this 3 houres. What is steam turbine description and characteristics. The ultimate state equation of differential expansion of steam turbine is proposed according to stressstrength interference theory.
Axial differential expansion between the rotor and the casing is a major. A typical large steam turbine power generation unit will have a thick case, on the order of 12 to 18. Sensitivity studies during steam turbine start up, gt201542214. A steam turbine undergoes thermal expansion as its case heats during steam admission. Differential expansion sensitivity studies during steam. Either admitting cold steam to a hot turbine or hot steam to a cold turbine. Although the application of differential expansion and rotor expansion have much in. Figure 3 supersaturated expansion of steam into wet region 3. In an extracting type turbine, steam is released from variousin an extracting type turbine, steam is released from various stages of the turbine, and used for industrial process needs or sentstages of the turbine, and used for industrial process needs or sent to boiler feed water heater to.
Single flow high pressure turbine another unique casing design is shown in figure 3. The differential expansion measurement is to measure this difference and ensure. Reliability analysis for differential expansion of steam. Ge they require controlled thermal transients as the massive casing heats up slowly and. Rotor expansion on a turbine is the absolute measurement of the rotors axial thermal growth with respect to the turbines foundation. Turbine casing expansion, rotor expansion and differential expansion differential expansion is very important when you start a turbin. Hence, it is necessary to maintain the highpressure turbine hpt, intermediatepressure turbine ipt, and lowpressure turbine lpt differential expansions within the predetermined limits. Aug 04, 2018 heloo friends welcome to power plant guruji. Reliability sensitivity analysis for differential expansion. Tsi shows and records the starting and status processes of various parts in the turbine generator with real time during operation and also transfers signals to computers and data loggers. We have trouble with differential expansion mostly during restart. Keywords asymmetric dilatation, thermal expansion, misalignment, turbomachinery i. The reliability analysis for differential expansion of steam turbine is discussed extensively.
Steam turbines are made in a variety of sizes ranging fromsteam turbines are made in a variety of sizes ranging from small steam turbine hp differential expansion automation. Sensitivity studies during steam turbine startup, gt201542214. Chaplin encyclopedia of life support systems eolss figure 2. Based on the premise that the probability distribution of random parameters has been known, the differential expansion of steam turbine is analyzed by saddlepoint approximation method. Introdution during our work throughout europe we have been often confronted with steam turbines and turbomachinery suffering from asymmetric dilatation not to be confused with differential dilatation. Generally in a steam turbine the rear support of the steam turbine or the rear side of the casing is fixed. What is differential casing expansion in steam turbine. Sensonics technical note ds1220 differential expansion. A turbine stage normally consists of a row of stationary blading and a row of rotating blading. One of the most important measurements is that of differential expansion. Steam turbines are one of the most versatile and oldest prime mover technologies still in general production used to drive a generator or mechanical machinery. Chaplin encyclopedia of life support systems eolss both of these have double casings with the exhaust steam circulating in the annular space between the casings as in the case of the high pressure turbine. The primary purpose of a differential expansion monitor is to guard against axial rub between rotating and stationary parts. How is it possible with the safety of the turbine in case o excessive differential expansion.
On the premise of the probability distribution of random parameters, using saddlepoint approximation method, probability density function of limit state function of differential expansion of steam turbine is. Steam turbine casing front side is generally free and slide on the front side bearing pedestal. Differential expansion on a turbine is the relative. Instruction manual for single stage 350, 500, and 700.
This parameter measures how the turbine rotor expands in relation to the turbine shell or. In this context the above mentioned intermittent smaller. Every time during warm startup steam temp allowable is 370 deg and pressure 5. Turbine supervisory instrumentation system tsi on large steam turbine generator applications. This chapter covers important information on the design of steam turbine systems. In general, a steam turbine is a rotary heat engine that converts thermal energy contained in the steam to mechanical energy or to electrical energy. Expansion occurs through a series of fixed blades nozzles and also moving blades. Two or more steam turbine choices are available for each stag system. What is differential or relative expansion in steam. In 1924 krupp built the steam turbine locomotive t18 001, operational in 1929, for deutsche reichsbahn.
Turbine loading leads to positive expansion, while unloading results in negative differential. Although the application of differential expansion and rotor expansion have much in common, it is important to understand the difference between the two measurements. This is very important parameter receiving much attention during turbine startup and warming. Alstoms ultrasupercritical steam turbine at the boxberg power plant in germany can produce 600 mw.
1115 321 1433 40 756 1045 1286 230 321 70 1512 1165 880 768 200 1556 1261 304 1526 1390 382 151 1073 104 766 825 671 946 733 546