Because partially expanded steam is exhausted to the low pressure turbine where the expansion is completed. 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. Using steam turbine warming blankets to reduce startup. The first steam turbine used for power generation was invented in 1884. Three basic phases can be distinguished in the process of steam turbine unit start. Turbine supervisory instrument tsi instrumentation and. 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. Part 1 operation manual of steam turbine valve turbine scribd. In order to improve the startup flexibility of steam turbines, it becomes relevant to analyze their dynamic thermal behavior. Steam turbines have to be warmed slowly to avoid differential expansion of components, which can cause rotor stress and reduce service life. In this context the above mentioned intermittent smaller.
This parameter measures how the turbine rotor expands in relation to the turbine shell or. Us5388960a forcedair cooling apparatus of steam turbine. When turbine is in service, superheated steam temperature above 540 degree celsius is admitted into the turbine. Siemens steam turbine sst5000 series for combined cycle and subcritical steam applications in our siemens steam turbine sst portfolio, we offer the sst5000 series. A turbine stage normally consists of a row of stationary blading and a row of rotating. A turbine stage normally consists of a row of stationary blading and a. Maintenance and overhaul of steam turbines wgp42 05. This is due to the time lag in the condensation of the steam during the expansion. Both the ends are supported on independent pedestals.
The steam turbine is a form of heat engine that derives much of its improvement in thermodynamic efficiency through the use of multiple. Steam turbines have a known thermal expansion, where. The differential expansion measurement should not be confused with other axial position measurements such as. In its simplest form, a steam turbine consist of a boiler steam generator, turbine, condenser, feed pump and a variety of auxiliary devices. This is very important parameter receiving much attention during turbine startup and warming. Differential expansion of steam turbine generators 34wm0q69kyl7. What is positive differential expansion of steam turbine. The measurement is commonly referred to as differential expansion and applies to various stages of. We are using bently nevada 3300 xl 25 mm transducer. Key phasor is used to find the phase angle of unbalanced mass for dynamic balancing.
Steam turbine start up free download as powerpoint presentation. The differential expansion measurement is to measure this difference and ensure that the rotor does not touch the stationary parts. Generally in a steam turbine the rear support of the steam turbine or the rear side of the casing is fixed. Tsi aims at monitor safe and reasonable steam turbine operation. Differential measurement for large steam turbines with long shaft systems, an additional axial position. 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. 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. Sensonics technical note ds1220 differential expansion. Keywords steam turbines, transients, startup, finite element model, heat transfer. 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. The primary purpose of a differential expansion monitor is to guard against axial rub between rotating and stationary parts.
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. A consequence of excessive thermal expansion is rotor rubbing. A forcedair cooling apparatus is provided for a steam turbine which comprises an outer casing composed of upper and lower casing halves, an inner casing composed of upper and lower casing halves and disposed inside the outer casing and a rotor coaxially disposed inside the inner casing for forming a steam flow passage between the inner casing and the rotor and in which steam introduced into. Title startup of steam turbine and its auxiliaries 2. What is differential expansion in steam turbine answers. Steam turbine drives are equipped with throttling valves or nozzle governors to modulate steam flow and achieve variable speed operation. Modern large steam turbines are exceedingly complex machines.
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 mx2534 is designed specifically to measure thermal expansion of steam turbine cases relative to their foundation. 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. Unit iii unit iii steam nozzles and turbines flow of steam through nozzles, shapes of nozzles, effect of friction, critical pressure. Range perform startup of steam turbine and its auxiliaries in general industrial plants, power plants or other places. Differential expansion of steam turbine generators. What is differential casing expansion in steam turbine.
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. Based on saddlepoint approximation method and sensitivity analysis method, reliability sensitivity analysis for differential expansion of steam turbine with random parameters are studied. Steam turbines power generation siemens siemens global. 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. 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 on a turbine is the relative. Thermal behaviour of steam turbines vgbr 105 m e first edition 1977 second, revised edition 1993 published by. Keywords asymmetric dilatation, thermal expansion, misalignment, turbomachinery i. Rotor expansion on a turbine is the absolute measurement of the rotors axial thermal growth with respect to the turbine s foundation.
Our steam turbines work as generator drives or as mechanical drives for. The system can be damaged, which has harmful effects on the entire power plant. 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. 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. Differential expansion on a turbine is the relative measurement of the rotors axial thermal growth with respect to the case. Although the application of differential expansion and rotor expansion have much in common, it is important to understand the difference between the two measurements. Steam turbine casing front side is generally free and slide on the front side bearing pedestal.
Excessive differential expansion can produce one of the most catastrophic failures of rotary machinery resulting in very expensive repairs and possibly machine replacement. Turbine supervisory instrumentation system tsi on large steam turbine generator applications. 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. In this work, the relative expansion between rotor and casing was studied during coldstart conditions. Differential expansion sensitivity studies during steam. 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.
Neglect initial velocity of steam and assume isentropic expansion in the nozzle. Steam turbines startups 1 principles of steam turbines startups. Unlike with reciprocating engines, for instance, compression, heating and expansion are continuous and. We are commissioning this turbine for the first time. It is the difference between change in shaft lent and change in casing length. Although the application of differential expansion and rotor expansion have. The steam turbine drive is capable of serving the same function as a variable speed drive electric motor driver. Differential expansion occurs due to high differential temperature of turbine shaft and casing. 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. The case expansion measurement is typically required as part of a suite of supervisory measurements on steam turbines in power generation service. The torsional load on single components like shafts or turbine blades might exceed a specified value and fail.
Capacity expansion the steam turbine lowpressure last stage, the output burden of which is large, is one of the. Differential expansion sensitivity studies during steam turbine startup article in journal of engineering for gas turbines and power 86 september 2015 with 370 reads how we measure reads. Latest technologies and future prospects for a new steam. Differential expansion monitoring measures the change in axial clearances between the machine rotor and casing caused by thermal changes inherent in most machines. Turbine loading leads to positive expansion, while unloading results in negative differential. Steam turbines can usually operate across a broad speed range and do not fail when overloaded.
211 792 91 121 1219 1083 1068 1058 568 307 1484 193 935 525 11 213 1568 199 739 569 1025 1661 540 42 469 1017 1105 1260 159 1693 235 1298 664 1466 1012 589 1210 1377 975 718 1080