Dec 11, 2015 a steam turbine has a fixed end and moving end. Unlike with reciprocating engines, for instance, compression, heating and expansion are continuous and. 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. The following addresses best practices for optimal steam system turbine maintenance and operation.
Noles references module 23414 turbine operational problems. Theoretical and numerical analysis of the mechanical erosion. Concerning the steam turbine st component, one key aspect of its flexibility is the capability for fast starts. Differential expansion of steam turbine generators turbine. Either admitting cold steam to a hot turbine or hot steam to a cold turbine. A turboexpander, also referred to as a turboexpander or an expansion turbine, is a centrifugal or axialflow turbine, through which a highpressure gas is expanded to produce work that is often used to drive a compressor or generator. Range perform startup of steam turbine and its auxiliaries in general industrial plants, power plants or other places. Numerical code, mesh blade, erosion blade, steam turbine, drop distribution.
Although the application of differential expansion and rotor expansion have much in common, it is important to understand the difference between the two measurements. Design and analysis of highpressure casing of a steam turbine. Differential expansion tsi free download as pdf file. Investigation into the thermal limitations of steam. Thermal power plants steam turbine components and systems r. 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. Steam turbine types steam turbine types based on blade geometry and energy conversion process are. Proceedings of the asme turbo expo, montreal, canada. Title startup of steam turbine and its auxiliaries 2. Describe each of those operating parameters monitored by turbine supervisory instruments, instrument function, and interpretation. Pmi revision 00 steam turbine a steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into useful mechanical work.
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. With the expansion of the steam in the turbine the rotor of the turbine and generator which are mechanically coupled start rotating, generating electricity which is then transmitted to sub stations. Figure 3 supersaturated expansion of steam into wet region 3. Differential expansion on a turbine is the relative. A turboexpander, also referred to as a turboexpander or an expansion turbine, is a centrifugal or axialflow turbine, through which a highpressure gas is expanded to produce work that is often used to drive a compressor or generator because work is extracted from the expanding highpressure gas, the expansion is approximated by an isentropic process i. The reliability analysis for differential expansion of steam turbine is discussed extensively. Excessive differential expansion can produce one of the most catastrophic failures of rotary machinery resulting in very expensive repairs and possibly machine replacement. 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.
Best practices for steam turbine maintenance and operation. Willard gibbs suggested using a surface with entropy, pressure, and total heat as coordinates. Impulse steam turbineimpulse steam turbine on impulse turbine a thermal expansion take place only in theon impulse turbine a thermal expansion take place only in the nozzles and static energy is converted to the kinetic energynozzles and static energy is converted to the kinetic energy there is no pressure different at inlet and outlet of. High temperature and pressure is used to rotating the turbine at high speed.
Turbine supervisory instrumentation system tsi on large steam turbine generator applications. The temperatureentropy diagram is much inferior to the mollier diagram for the quantitative solution of problems in steamturbine design. 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. Steam does not condense at the saturation temperature. In noncondensing turbines or backpressure turbines, steam exhausts at a pressure greater than. 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. Axial differential expansion between the rotor and the casing is a major. Differential expansion sensitivity studies during steam. During short trip outs, the supply of stream of turbine has to be totally cut off from the boiler. What is differential expansion in steam turbine answers. The first steam turbine rail locomotive was built in 1908 for the officine meccaniche miani silvestri grodona comi, milan, italy. During this phase, the machine can potentially be subjected to excessive thermal stresses and axial rubbing due to differential thermal expansion.
Both the ends are supported on independent pedestals. Mccloskey is a fellow member of the asme, past chairman of the asme steam turbine committee, and member of the advisory committee for the international pump users symposium and a. Differential expansion sensitivity studies during steam turbine. Pdf design and analysis of highpressure casing of a steam. Request pdf differential expansion sensitivity studies during steam turbine startup in order to improve the startup flexibility of steam turbines, it becomes. Steam quality steam must be of the highest quality. In general, reaction turbine is not stand alone, but works at behind impulse turbine. Reliability analysis for differential expansion of steam. About 30 months ago acceptance testing was performed on a steam turbine unit that failed to meet the guarantee. Troubleshooting bearing and lube oil system problems thomas h. Higher load more cooling and less back pressure lower steam temps means a shorter turbine. What we need to consider is that one surface of turbine casing is exposed to atmospheric.
Steamturbine principles and practice by croft, terrell, 1880publication date 1923 topics steam turbines. Sensitivity studies during steam turbine start up, gt201542214. 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. Describe normal steam turbine startup and shutdown procedures. Simplified physical understanding of gas turbine matching in a gas turbine engine, the operating point is defined by the match between the compressor and the turbine. The temperatureentropy diagram is much inferior to the mollier diagram for the quantitative solution of problems in steam turbine design. Theoretical and numerical analysis of the mechanical. Sep 19, 2017 concerning the steam turbine st component, one key aspect of its flexibility is the capability for fast starts.
Based on the premise that the probability distribution of random parameters has been known, the differential expansion of steam turbine is analyzed by saddlepoint. Single flow high pressure turbine another unique casing design is shown in figure 3. When turbine is in service, superheated steam temperature above 540 degree celsius is admitted into the turbine. Steam turbine startup is a phase of particular interest since is considered to be the most intricate of transient operations.
Both of those abnormal conditions are covered in our manuals and the temperature parameters are identified. Steam conditions the turbine expansion line or condition curve represents steam conditions prevailing in sequential stages of the steam turbine. Every time during warm startup steam temp allowable is 370 deg and pressure 5. In current practice, turbine startup limitations are set by consideration of thermal stress and low cycle fatigue. 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. Differential expansion of steam turbine generators. Turbine is a rotary engine that converts the energy of a moving stream of water, steam, or gas into mechanical energy. Turbine generator rotor vibranon the spinning turbine generator rotods the major source ofpulsating forces which causevibration not only ofthe rotoritself, butalso ofthe otherparts ofthe machine eg. Chaplin encyclopedia of life support systems eolss figure 2. What is differential or relative expansion in steam. For m this we can observe that, to get more power output the steam. Differential expansion of the steam turbine cr4 discussion. The first steam turbine used for power generation was invented in 1884. 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.
Although the application of differential expansion and rotor expansion have much in. We are commissioning this turbine for the first time. The basic element in a turbine is a wheel or rotor with addles, propellers, blades, or buckets arranged on its circumference in. The expansion of steam is expected here through a turbine.
In order to improve the startup flexibility of steam turbines, it becomes relevant to analyze their dynamic thermal behavior. This manual does not for designing steam turbine and the related parts. Numerical code, mesh blade, erosion blade, steam turbine, drop. In case of turbines with cooling water preheating and lowpressure lp bypass, prior to supplying steam the regeneration and dumping systems have to be.
Due to heating up of parts of turbine, thermal expansion will take place. The air that leaves the moving blades enters the next set of nozzles where the enthalpy decreases further, and the velocity is. Sensitivity studies during steam turbine startup, gt201542214. Purpose this manual can be used for preliminary selection, steam and cooling water planning for steam turbines in basic and detail engineering stages. The steam turbine is a form of heat engine that derives much of its improvement in thermodynamic efficiency through the use of multiple stages in the expansion of the steam, which results in a closer approach to the ideal reversible process. Differentialrotor expansion sti vibration monitoring inc. Steam turbines, operation, supersaturation, moisture, back pressure. Differential expansion of steam turbine generators scribd. Improvements of up to 30% were accounted to this measure. Differential expansion of steam turbine generators free download as pdf file. Generally in a steam turbine the rear support of the steam turbine or the rear side of the casing is fixed. The differential expansion measurement should not be confused with other axial position measurements such as. In 1924 krupp built the steam turbine locomotive t18 001, operational in 1929, for deutsche reichsbahn. Simulation of the heat exchangers dynamics in matlab.
Steam turbine casing front side is generally free and slide on the front side bearing pedestal. Due to expansion of steam, pressure drop occurs continuously over both fixed and moving blades. A turbine stage normally consists of a row of stationary blading and a row of rotating blading. This pressure difference exerts a thrust on the blades. Steam consumption of steam turbine is depending to required output power and efficiency of the turbine.
In a steam turbine, highpressure steam from the boiler expands in a set of stationary blades or vanes or nozzles. Steam turbine differential expansion amp maintenance forums. Steam turbines the simplest singledisc steam turbine consists of the following parts shaft. We have trouble with differential expansion mostly during restart. In this turbine, the work is broken down into various stages. In its simplest form, a steam turbine consist of a boiler steam generator, turbine, condenser, feed pump and a variety of auxiliary devices. Plotted on a mollier diagram it provides a useful visual image of these conditions.
The international association for the properties of water and steam london, united kingdom september 20 technical guidance document. This was developed by kraftwerk union and also overcomes the need for a very heavy flange in the high pressure cylinder. Investigation into the thermal limitations of steam turbines. Nonlinear mathematical model of the condensing steam turbine 875 where. Determination of flow coefficient of a hp bypass value. What is differential casing expansion in steam turbine.
Disc with moving blades fixed blades on its periphery. Unesco eolss sample chapters thermal power plants steam turbine components and systems r. The ultimate state equation of differential expansion of steam turbine is proposed according to stressstrength interference theory. Moving blades work due to differential pressure of steam between front and at behind of moving blades. 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. Maintenance and overhaul of steam turbines wgp42 05. Impulse turbines are simple devices where the steam expands in or through the nozzle, and the heat released through the pressure drop associated with the nozzle or comparable device imparts velocity to the steam. Reaction turbine reaction force due to expansion of high pressure steam when it passes through a set of moving and fixed blades is used to rotate the turbine shaft. Steam purity for turbine operation 20 international association for the properties of water and steam publication in whole or in part is allowed in all countries provided that attribution is given to the. Another impulse turbine is the pressure compound or ratteau turbine. The shaft along with the disc mounted upon it comprises the most important part of the turbine and is known as the rotor, which is housed in the turbine casing.
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. Differential expansion tsi turbine electric generator. There are two classical types of turbine stage designs. Steam turbine simulation matlab free pdf file sharing. Steam turbines startups 1 principles of steam turbines startups. Condensate entrapment in the steam supply increases turbine steam rates, reduces the steam turbine efficiency, and causes erosion of steam turbine components governor valves, blading, and nozzles. In this article we discussed about the type of emergency in steam turbine occurred during the operation time of steam turbine. Prior to supplying steam to the turbine, the steam supply pipelines have to be drained and heated up. Each stage consists of a nozzle and blade row where the kinetic energy of the jet is absorbed into the turbine rotor as useful work.