Lowering the erosion wear of long blades of the last stages by optimum hanging

Problems of optimum hanging of long rotor blades of the last stages of steam turbines are considered. Causes of nonuniform erosion wear of the inlet edges connected with inaccurate location of holes for the external damper coupling on the chord of the profile are determined. Methods for optimizing the hanging of blades for raising the reliability of the last stages are suggested. Main results of hanging performed with the help of a specially developed “LIBRA” soft hardware are presented. __________ Translated from élektricheskie Stantsii, No. 11, November 2006, pp. 36–41.     

Installation of molten-metal seals in steam-turbine valves

Gaps in valves between the stems and boxes are a source of rather large steam and heat losses in power-generating steam turbines. A unique development of specialists employed by the Vserossiiskii Teplotekhnicheskii Institut — superairtight seals (SAS) with composite materials, which permit reliable sealing of valves with minimal friction within the system—is presented. Investigations conducted have indicated that the proposed type of SAS is capable of sealing gaps in valves with steam parameters of 29.75 MPa (300 kgf/cm²) and 600°C. __________ Translated from élektricheskie Stantsii, No. 1, January, 2007, pp. 35–37.     

Effect of Operating Conditions of a T-250/300-240 Turbine on the Level of Wetness in the Stages of the Low-Pressure Cylinder

The operation of the low-pressure turbine part in variable condensing and extraction regimes is analyzed. The effect of steam parameters at the inlet to the low-pressure part (in the lower extraction chamber) and of operation of the regulating stage of the LPP on the level of wetness in the low-pressure stages is determined. It is shown that the moving blades of the last stages of cogeneration turbines operate under heavier erosion conditions than in condensing turbines. This is one of the main causes of their intense erosion wear. __________ Translated from Elektricheskie Stantsii, No. 6, June 2005, pp. 27 – 32.     

Operation of T-250/300-240 turbines without working blades in the last stages of the low-pressure cylinder

The current operating regimes for turbines of this type and their possible long-term uses affect the choice of a rational option for the modernization of the low-pressure cylinder (using a three stage rotor with reduced lengths of the working blades in the last stage or removal of working blades in the last stages), which should be made taking into account the specific conditions at each given heating and electric power plant. Studies of T-250/300-240 turbines at the heating and electric power plant TéTs-23 of JSC “Mosénergo” operating without working blades in the last stages of the low-pressure cylinder are described. These demonstrate increased efficiency during both summer and winter operation under the conditions at this plant. The condition of the trailing edges of the working blades in stages 30 and 39 is found to be excellent, but erosion of the steam inlet deflector cone in the region of the feedthrough for the low-pressure cylinder along the direction of the twist in the flow is observed. It is proposed that an alignment module be installed at the outlet of the low-pressure cylinder for protection from overload, the compressor effect, and root eddies. For further increases in efficiency it is proposed to examine the feasibility of raising the maximum allowable temperature of the exhaust at the low-pressure cylinder of the modernized turbine. __________ Translated from élektricheskie Stantsii, No. 11, November 2007, pp. 84–90.     

On the water-chemical regime in steam generators at NPP

The effect of the water-chemical regime (WCR) on damage sustained by heating surfaces of steam generators at NPP is analyzed. It is indicated that phosphate treatment with minimal excesses of phosphates in the steamgenerator water is the most optimal method of managing the WCR regime of horizontal steam generators. __________ Translated from élektricheskie Stantsii, No. 5, pp. 15–21, May, 2006. In order of discussion (The editor).     

Connecting the second exhaust-heat boiler to the operating first one under the conditions of flow circuits of combined-cycle plants with two gas-turbine units and one steam turbine

Problems arising with connecting the second exhaust-heat boiler to the first exhaust-heat boiler under load in the case of flow circuits of combined-cycle plants of type PGU-450 are considered. Similar problems exist for two-boiler single-turbine units of type PGU-325 and for two-boiler single-turbine units of traditional steampower plants with an output of 200–300 MW upon connection of the second furnace of a two-furnace boiler to the operating first furnace. Analysis of the temperature-induced stressed state and of the cyclic strength of thick-walled elements of the steam-water conduit of PGU-450 and of two-furnace boilers of two-boiler single-turbine units with an output of 200–300 MW (the check valve, the inlet header of the water economizer) is used for determining the steam temperature differences in the high-pressure conduits to the steam turbine and the order of connection of the second exhaust-heat boiler to the operating fist one. Modes of enabling a two-boiler single-turbine unit of a combined-cycle plant, which are most “rigid” from the standpoint of thermal strength, are determined. __________ Translated from élektricheskie Stantsii, No. 2, February 2006, pp. 11–17.     

Conversion of the steam-supply system of 800-MW supercritical-pressure units to lower steam temperature upon introduction of a sliding startup process

Results of testing a novel process of startup of 800-MW supercritical-pressure units at sliding pressure in the entire conduit of the once-through boiler with the temperature of extraneous steam in the station-service header supplying the turbine-feeding pump reduced to ∼250°C and intermediate transfer of its feed to its own steam through the available station-service starting-shedding device are given. It is shown that the use of this process makes it possible to fully pass to steam supply of the unit from the colder second extraction of the turbine. A variant of updating the steam feeding circuit is suggested. __________ Translated from élektricheskie Stantsii, No. 11, November 2006, pp. 9–13.     

Development and Integration of Sub-hourly Rainfall–Runoff Modeling Capability Within a Watershed Model

Increasing urbanization changes runoff patterns to be flashy and instantaneous with decreased base flow. A model with the ability to simulate sub-daily rainfall–runoff processes and continuous simulation capability is required to realistically capture the long-term flow and water quality trends in watersheds that are experiencing urbanization. Soil and Water Assessment Tool (SWAT) has been widely used in hydrologic and nonpoint sources modeling. However, its subdaily modeling capability is limited to hourly flow simulation. This paper presents the development and testing of a sub-hourly rainfall–runoff model in SWAT. SWAT algorithms for infiltration, surface runoff, flow routing, impoundments, and lagging of surface runoff have been modified to allow flow simulations with a sub-hourly time interval as small as one minute. Evapotranspiration, soil water contents, base flow, and lateral flow are estimated on a daily basis and distributed equally for each time step. The sub-hourly routines were tested on a 1.9 km² watershed (70% undeveloped) near Lost Creek in Austin Texas USA. Sensitivity analysis shows that channel flow parameters are more sensitive in sub-hourly simulations (Δt = 15 min) while base flow parameters are more important in daily simulations (Δt = 1 day). A case study shows that the sub-hourly SWAT model reasonably reproduces stream flow hydrograph under multiple storm events. Calibrated stream flow for 1 year period with 15 min simulation (R ² = 0.93) shows better performance compared to daily simulation for the same period (R ² = 0.72). A statistical analysis shows that the improvement in the model performance with sub-hourly time interval is mostly due to the improvement in predicting high flows. The sub-hourly version of SWAT is a promising tool for hydrology and non-point source pollution assessment studies, although more development on water quality modeling is still needed.     

Calculating the thermally stressed state of the high and medium pressure rotors of a T-250/300-240 turbine in the labyrinth seal zone

The temperature and thermally stressed state of the high and medium pressure rotors of the T-250/300-240 district heating steam turbine are calculated, taking into account the concentration of stresses in the neighborhood of the thermal grooves in labyrinth seals. “Critical” zones in the turbine rotors, within which thermal stresses limit the rate of startup, are determined. Some practices for reducing the temperature stresses are suggested. __________ Translated from élektricheskie Stantsii, No. 1, pp. 32–37 (2008).     

Use of a magnetization effect for monitoring thermal inhomogeneities in steam superheaters made of 12Kh18N12T steel

Coils of 12Kh18N12T steel become magnetized during operation because the surface layer of the metal at the scale boundary is depleted in chromium and enriched in ferromagnetic nickel. A large-scale study of the relationship between the thickness of the altered layer and the operating temperature and individual service life is underway at Mosénergo’s TéTs-26 heating and electric power plant. Ferritometry and selective replacement have made it possible to reduce the amount of strain-induced and embrittlement damage and to extend the service life of steam superheaters. This could not be done by traditional methods, in particular ultrasonic monitoring of the wall thickness. The data obtained here can serve as a basis for creating a new technique for monitoring thermal inhomogeneity in steam superheaters made of austenitic steels. The advantages of ferritometric monitoring include the following: special preparation (cleaning) of coils is not required, the measurements are convenient, and segments with the highest temperature can be detected. __________ Translated from élektricheskie stantsii, No. 12, December 2007, pp. 22–25.     

Mathematical models for optimization of block diagrams and controller adjustment

The building of easily controlled production subassemblies is one of the urgent problems encountered in the development of heating systems for modern power plants. This paper describes a process by which a control system is built with subassemblies for the feed of basic condensate and steam to a deaerator by combined efforts of engineering and automation experts. __________ Translated from élektricheskie Stantsii, No. 8, August 2007, pp. 18–23.     

Improvements in the technique for assembling flanged connectors in the shaft lines of turbine units

When the standard brackets for flanged connectors are removed during repair or during measurements of the centering of the rotors relative to the sleeves, the connecting bolts and associated apertures in the sleeves are often damaged. In order to increase vibrational reliability, reduce the time spent, and cause less damage in the bore of the sleeves, it is proposed that the flange connectors be assembled with the aid of tapered bushings, pins, and hydraulic extraction of the brackets. Translated from élektricheskie stantsii, No. 5, May 2008, pp. 7–9.     

Development,construction, and use of pneumometric tubes for measurement of steam flow in the steam lines of PVG-1000 at NPP

A system for the direct measurement of steam flow in steam lines after a steam generator, which utilizes a special design of pneumometric tubes and a computing unit that accounts for variation in steam pressure, has been developed to improve the quality of water-level regulation in the steam generators of VVéR-1000 power-generating units in the stationary and transitional modes. The advantage of the pneumometric tubes consists in their structural simplicity, high erosion resistance, and absence of irrevocable losses during measurement of steam flow. A similar measurement system is used at foreign NPP. The measurement system in question has been placed in experimental service at the No. 3 unit of the Balakovo NPP, and has demonstrated its worthiness. This measurement system can also be used to determine steam flow in the steam lines of NPP units with VVéR-1000 and VVéR-440 reactors, and PBMK-1000 power-generating units. __________ Translated from élektricheskie Stantsii, No. 3, March 2007, pp. 23–26.     

A study of the high-temperature strength and crack resistance of the metal of the body of stop valve from high-chromium steel 15Kh11MFBL after long-term operation

The applicability of the rapid method for determining the ultimate long-term strength, endurance, and crack resistance of cylindrical specimens with three sharp notches, which has been developed by V. I. Gladshtein for pearlitic steels, to chromium steel 15Kh11MFBL is considered. It is shown that the results of evaluation of high-temperature strength by the standard method and with the use of notched specimens supplement each other. Prediction of the time before failure of smooth specimens from notched specimens makes it possible to perform the evaluation for 100,000–300,000 h, which is impossible by direct testing at operating temperatures. __________ Translated from élektricheskie Stantsii, No. 10, October 2005, pp. 78–80.     

Experience in the operation of the T-150-7.7 LMZ steam turbine under the conditions of the PGU-450 flow diagram

Results of five years of operation of a double-pressure cogeneration steam turbine T-150-7.7 under the conditions of the PGU-450T flow diagram at the North-West Cogeneration Plant in the condensing mode from the beginning of service of the power unit in December 2000 are analyzed. __________ Translated from élektricheskie Stantsii, No. 10, October 2005, pp. 56–61.     

Results of heat tests of the TGE-435 main boiler in the PGU-190/220 combined-cycle plant of the Tyumen’ TÉTs-2 cogeneration plant

Special features of operation of a boiler operating as a combined-cycle plant and having its own furnace and burner unit are descried. The flow of flue gases on the boiler is increased due to feeding of exhaust gases of the GTU into the furnace, which intensifies the convective heat exchange. In addition, it is not necessary to preheat air in the convective heating surfaces (the boiler has no air preheater). The convective heating surfaces of the boiler are used for heating the feed water, thus replacing the regeneration extractions of the steam turbine (HPP are absent in the circuit) and partially replacing the preheating of condensate (the LPP in the circuit of the unit are combined with preheaters of delivery water). Regeneration of the steam turbine is primarily used for the district cogeneration heating purposes. The furnace and burner unit of the exhaust-heat boiler (which is a new engineering solution for the given project) ensures utilization of not only the heat of the exhaust gases of the GTU but also of their excess volume, because the latter contains up to 15% oxygen that oxidizes the combustion process in the boiler. Thus, the gas temperature at the inlet to the boiler amounts to 580°C at an excess air factor α = 3.50; at the outlet these parameters are utilized to T _out = 139°C and α_out = 1.17. The proportions of the GTU/boiler loads that can actually be organized at the generating unit (and have been checked by testing) are presented and the proportions of loads recommended for the most efficient operation of the boiler are determined. The performance characteristics of the boiler are presented for various proportions of GTU/boiler loads. The operating conditions of the superheater and of the convective trailing heating surfaces are presented as well as the ecological parameters of the generating unit. __________ Translated from élektricheskie Stantsii, No. 12, December 2006, pp. 26–32.     

Experimental investigations of the effect of new passive safety systems on the temperature state of fuel elements

Results of experiments conducted on a large-scale integral PSB-VVéR bench and directed toward investigation of the performance of new passive safety systems for nuclear plants with a water-cooled power reactor, an additional system for passive flooding of the active zone, and a system for the passive removal of heat from steam generators are presented. __________ Translated from élektricheskie Stantsii, No. 9, September 2007, pp. 7–10.     

Transport of Contaminants with Boiler Water Steam

A method for determining coefficients of distribution of contaminants between boiler water and steam generated in boilers and steam generators of nuclear power plants, which is based on standard thermodynamic dissociation constants, is presented. Appropriate analytical dependences are given for hydroxides of metals used in the power industry for pressures of 40, 87.5, and 155 kgf/cm² (3.9, 8.6, and 15.2 MPa). __________ Translated from Elektricheskie Stantsii, No. 7, July 2005, pp. 38 – 39.     

Assessing the remaining life of bends of live steam conduits from steel 15Kh1M1F

It is shown that the remaining life of bends of steam conduits from steel 15Kh1M1F should be evaluated on the basis of results of estimation of microdamage of the metal performed on a representative sample with allowance for the operating factors. __________ Translated from élektricheskie Stantsii, No. 3, March 2006, pp. 29–32.