residual life assessment (rla) based renovation ... - India Core

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component. Based on above evaluation and material testing, decision regarding rectification / replacement is taken. In all these calculations the reliability and accuracy of the operating data is of vital importance. Any prediction of remaining life may prove to be inaccurate if data is incomplete or inaccurate. Based on these studies, for extending life of steam turbine components , recommendations are given regarding: Remaining life of steam turbine components. Immediate replacement of a component is required or it can be replaced after a prescribed period. Repair of a particular component Change in steam parameters at the inlet, if required. De-rating of steam turbine. Alterations in the mode of future operation of the set. Alterations in the material of certain components Need for more often inspections. Proposals for R & M. 4.0 R & M OF STEAM TURBINES : Reliable and economical power generation is the primary goal of each electrical utility worldwide. Such a goal can be achieved through: Maximizing the efficiency of the turbine-generator. Extending the intervals between inspections and Achieving greater reliability in operation. During the development and design of its steam turbines, BHEL considers all of these factors in order to offer attractive products to its customers. This is achieved by the following: Improving the efficiency of the turbine with use of advanced blading. Maximizing the use of existing hardware whenever practical. Extending the service intervals by use of advanced manufacturing techniques as well as carefully selected materials for the components. This also leads towards greater reliability in plant operation. IMPROVEMENT IN PERFORMANCE & OUTPUT OF STEAM TURBINE CAN BE ACHIEVED BY FOLLOWING: Use of improved blade profile which result into reduction in the aerodynamic flow losses e.g. profile loss, secondary flow loss & tip leakage loss. More uniform flow distribution. Optimization of flowpath. Improvement in shaft sealing system. International Conference & Exhibition India Thermal Power-4 Page 6 of 22
Reduction in pressure drops. Reduced friction losses. Optimization of inlet & exhaust section geometry of valves & casings. Optimization of exhaust loss. 5.0 BHEL’S PROPOSAL FOR R&M OF 200 / 210 MW STEAM TURBINES (LMW DESIGN): BHEL, Haridwar, has manufactured and supplied 57 sets of Type K-210-130 (LMW Design) steam turbines. About 10 sets of similar design, imported directly by Utilities, from Russia, are also under operation. These sets have already completed 13 to 30 years of operation. Thus the useful life of most of the sets is already over. The Steam Turbine of Type K-210-130 (LMW Design) was designed in early 60’s, therefore, there is good scope for renovation & modernization of these sets to extend their operating life, making them efficient and increasing their output. The upgradation of HP and LP Turbines is possible by incorporating features mentioned al S.No. 2.0 above. EXISTING DESIGN: Existing 210 MW Steam Turbine (LMW design ) is fitted with impulse blading. Figure 1 shows its cross section of HP Turbine & Figure 3 shows the cross section of LP Turbine. In this design steam pressure drop takes place mainly in guide blades provided in the diaphragms, while passing through moving blades there is negligible pressure drop. The LP Turbine is double flow and is provided with 2X4 stages. It has impulse blading. The maximum heat drop takes place across the fixed / guide blades. The fixed / guide blades are called DIAPHRAGMS which are in two halves. 1 st & 2 nd stage diaphragms are fitted in liners, which in turn are fitted in the casing. The penultimate stage of this LPT is BAUMEN STAGE which is provided to direct part of the steam flow to the condenser so as to reduce the moisture content as well as the volume of the steam flow in the last stages. The LP Rotor has a shaft and the discs of all the stages are shrink fitted on it. The blades are fitted in the grooves provided in the discs. These blades are provided with damping wire for dampening the vibrations. 5.1 IMPROVEMENT IN HP TURBINE: The HP turbines of 200 / 210 MW having impulse blading can be retrofitted by BHEL with state of art high efficiency reaction blading. In this design steam pressure drop takes place in guide blades as well as moving blades. Outer casing is kept same, if found healthy in RLA study. The internals i.e. Rotor, Liners and diaphragms are to be replaced with Monoblock HP Rotor and Guide Blade Carriers having more efficient reaction blading (Tx profile). International Conference & Exhibition India Thermal Power-4 Page 7 of 22
Page 1 and 2: RESIDUAL LIFE ASSESSMENT (RLA) BASE
Page 3 and 4: The components & zones identified a
Page 5: After thorough cleaning of the roto
Page 9 and 10: HP CASING LINER ROTOR Fig. 1 : Exi
Page 11 and 12: FIG.3-A: DETAILS OF EXISTING DESIGN
Page 13 and 14: Main Steam / HRH Steam Temperature:
Page 15 and 16: 6.0 BHEL’S PROPOSAL FOR R&M OF 20
Page 17 and 18: CYL PIN BREECH NUT OUTER CASING GUI
Page 19 and 20: 6.4 THERMAL INSULATION: Mineral woo
Page 21 and 22: 6.6 RLA BASED REPAIR / REPLACEMENTS

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