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. Using steam turbine warming blankets to reduce startup. In this context the above mentioned intermittent smaller. Steam turbines have a known thermal expansion, where. The principles of correct conducting startups have been developed over the longterm operation of steam turbines and contain experience of turbine designers, constructors and operators. Neglect initial velocity of steam and assume isentropic expansion in the nozzle. 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. Differential expansion occurs due to high differential temperature of turbine shaft and casing. 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. A turbine stage normally consists of a row of stationary blading and a row of rotating. 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.
Turbine supervisory instrument tsi instrumentation and. Us5388960a forcedair cooling apparatus of steam turbine. Keywords steam turbines, transients, startup, finite element model, heat transfer. 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. Excessive differential expansion can produce one of the most catastrophic failures of rotary machinery resulting in very expensive repairs and possibly machine replacement. Differential expansion of steam turbine generators 34wm0q69kyl7. This is very important parameter receiving much attention during turbine startup and warming. Capacity expansion the steam turbine lowpressure last stage, the output burden of which is large, is one of the. Steam turbines power generation siemens siemens global. Three basic phases can be distinguished in the process of steam turbine unit start. Sensonics technical note ds1220 differential expansion. Title startup of steam turbine and its auxiliaries 2.
Steam turbines have to be warmed slowly to avoid differential expansion of components, which can cause rotor stress and reduce service life. When turbine is in service, superheated steam temperature above 540 degree celsius is admitted into the turbine. In order to improve the startup flexibility of steam turbines, it becomes relevant to analyze their dynamic thermal behavior. Steam turbine drives are equipped with throttling valves or nozzle governors to modulate steam flow and achieve variable speed operation. Differential expansion of steam turbine generators. Schofield ge company schenectady, ny introduction the need to provide stateoftheart products for a diverse and everchanging market is the chal lenge facing steam turbinegenerator manufactur ers in the 90s. Differential measurement for large steam turbines with long shaft systems, an additional axial position. Although the application of differential expansion and rotor expansion have.
Its modern manifestation was invented by charles parsons in 1884 the steam turbine is a form of heat engine that derives much of its improvement in thermodynamic efficiency from the use of multiple stages in the expansion of the steam, which results. The differential expansion measurement should not be confused with other axial position measurements such as. The primary purpose of a differential expansion monitor is to guard against axial rub between rotating and stationary parts. Since the production of japans first land steam turbine 500 kw in 1908, mhpss steam turbines have accumulated 341,767 mw of output to date. Differential expansion on a turbine is the relative. Our steam turbines work as generator drives or as mechanical drives for. Differential expansion on a turbine is the relative measurement of the rotors axial thermal growth with respect to the case. The case expansion measurement is typically required as part of a suite of supervisory measurements on steam turbines in power generation service. Steam turbine casing front side is generally free and slide on the front side bearing pedestal. Range perform startup of steam turbine and its auxiliaries in general industrial plants, power plants or other places. The measurement is commonly referred to as differential expansion and applies to various stages of.
Rotor expansion on a turbine is the absolute measurement of the rotors axial thermal growth with respect to the turbine s foundation. The differential expansion measurement is to measure this difference and ensure that the rotor does not touch the stationary parts. Both the ends are supported on independent pedestals. Maintenance and overhaul of steam turbines wgp42 05. Differential expansion measurements on large steam turbines one of the challenges facing instrumentation engineers in the power generation sector is the accurate measurement of shaft growth relative to casing on large steam turbines. What is differential expansion in steam turbine answers. It is the difference between change in shaft lent and change in casing length. We are commissioning this turbine for the first time. Siemens steam turbine sst3000 series for combined cycle applications in our siemens steam turbine sst portfolio, we offer with the sst3000 series steam turbine a compact arrangement, that features a twocylinder design with an axial exhaust for application in combined cycle power plants with the latest gas turbine technology. The torsional load on single components like shafts or turbine blades might exceed a specified value and fail. This is due to the time lag in the condensation of the steam during the expansion. The steam turbine drive is capable of serving the same function as a variable speed drive electric motor driver. 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. Unit iii unit iii steam nozzles and turbines flow of steam through nozzles, shapes of nozzles, effect of friction, critical pressure.
The measurement is commonly referred to as differential expansion and. For hp differential expansion we are using direct differential expansion probe, and for lp differential expansion we are using. Because partially expanded steam is exhausted to the low pressure turbine where the expansion is completed. Generally in a steam turbine the rear support of the steam turbine or the rear side of the casing is fixed. Steam turbines can usually operate across a broad speed range and do not fail when overloaded. A turbine stage normally consists of a row of stationary blading and a. Turbine loading leads to positive expansion, while unloading results in negative differential. In this work, the relative expansion between rotor and casing was studied during coldstart conditions.
Steam turbine start up free download as powerpoint presentation. A consequence of excessive thermal expansion is rotor rubbing. Part 1 operation manual of steam turbine valve turbine scribd. What is positive differential expansion of steam turbine. Differential expansion monitoring measures the change in axial clearances between the machine rotor and casing caused by thermal changes inherent in most machines. Key phasor is used to find the phase angle of unbalanced mass for dynamic balancing. Turbine supervisory instrumentation system tsi on large steam turbine generator applications. 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. Latest technologies and future prospects for a new steam. Steam turbines startups 1 principles of steam turbines startups. Differential expansion sensitivity studies during steam. 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.
Keywords asymmetric dilatation, thermal expansion, misalignment, turbomachinery i. The mx2534 is designed specifically to measure thermal expansion of steam turbine cases relative to their foundation. This parameter measures how the turbine rotor expands in relation to the turbine shell or. The system can be damaged, which has harmful effects on the entire power plant. Tsi aims at monitor safe and reasonable steam turbine operation. Although the application of differential expansion and rotor expansion have much in common, it is important to understand the difference between the two measurements.
The steam turbine is a form of heat engine that derives much of its improvement in thermodynamic efficiency through the use of multiple. Because the turbine generates rotary motion, it is particularly suited to be used to drive an electrical generator about 90% of all electricity generation in the united states, is by use of steam turbines. Modern large steam turbines are exceedingly complex machines. Unlike with reciprocating engines, for instance, compression, heating and expansion are continuous and. Siemens steam turbine sst5000 series for combined cycle and subcritical steam applications in our siemens steam turbine sst portfolio, we offer the sst5000 series.
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