Sensors and Methods for Blade Damage Operational Assessment in Low-Pressure Steam Turbine Stages

2013 ◽  
Vol 569-570 ◽  
pp. 726-733 ◽  
Author(s):  
Pavel Procházka ◽  
František Vaněk
Keyword(s):  
Steam Turbine ◽  
Nuclear Power ◽  
Residual Life ◽  
Turbine Blades ◽  
Low Pressure ◽  
Mutual Position ◽  
Static Characteristics ◽  
New Approach ◽  
Pressure Steam

The study deals with the opportunities for the assessment of damage to blades in low-pressure steam turbine stages under operation. So far existing methods are based on measurements and evaluation of blade vibrations. Calculations of fatigue cycles are used as a basis for an estimate of the residual life of the blades. A new approach using the analysis of impulse blade signals generated by non-contact stator sensors was applied. Basis for the assessment of blade damage are static characteristics and mutual position of blades. Geometrical and mechanical characteristics of blades change due to creation and progress of a crack. The presence of the crack leads to a change in position between adjacent blades. This method has been applied and verified by long-term measurements at the nuclear power plant Temelin. Other static methods based on blade untwisting and elongation are suggested for monitoring the state of turbine blades.

Advanced Water Droplet Erosion Protection for Modern Low Pressure Steam Turbine Steel Blades

2015 ◽  
Author(s):  
Joerg Schuerhoff ◽  
Andrei Ghicov ◽  
Karsten Sattler
Keyword(s):  
Steam Turbine ◽  
Water Droplet ◽  
Precipitation Hardening ◽  
Turbine Blades ◽  
Low Pressure ◽  
Steam Turbines ◽  
Treatment Facility ◽  
Material Loss ◽  
Pressure Steam ◽  
Steam Turbine Blades

Blades for low pressure steam turbines operate in flows of saturated steam containing water droplets. The water droplets can impact rotating last stage blades mainly on the leading edge suction sides with relative velocities up to several hundred meters per second. Especially on large blades the high impact energy of the droplets can lead to a material loss particularly at the inlet edges close to the blade tips. This effect is well known as “water droplet erosion”. The steam turbine manufacturer use several techniques, like welding or brazing of inlays made of erosion resistant materials to reduce the material loss. Selective, local hardening of the blade leading edges is the preferred solution for new apparatus Siemens steam turbines. A high protection effect combined with high process stability can be ensured with this Siemens hardening technique. Furthermore the heat input and therewith the geometrical change potential is relatively low. The process is flexible and can be adapted to different blade sizes and the required size of the hardened zones. Siemens collected many years of positive operational experience with this protection measure. State of the art turbine blades often have to be developed with precipitation hardening steels and/or a shroud design to fulfill the high operational requirements. A controlled hardening of the inlet edges of such steam turbine blades is difficult if not impossible with conventional methods like flame hardening. The Siemens steam turbine factory in Muelheim, Germany installed a fully automated laser treatment facility equipped with two co-operating robots and two 6 kW high power diode laser to enable the in-house hardening of such blades. Several blade designs from power generation and industrial turbines were successfully laser treated within the first year in operation. This paper describes generally the setup of the laser treatment facility and the application for low pressure steam turbine blades made of precipitation hardening steels and blades with shroud design, including the post laser heat treatments.

An investigation of the failure of low pressure steam turbine blades

1998 ◽  
Vol 5 (3) ◽  
pp. 181-193 ◽  
Author(s):  
N.K. Mukhopadhyay ◽  
S.Ghosh Chowdhury ◽  
G. Das ◽  
I. Chattoraj ◽  
S.K. Das ◽  
...  
Keyword(s):  
Steam Turbine ◽  
Turbine Blades ◽  
Low Pressure ◽  
Pressure Steam ◽  
Steam Turbine Blades

Effect of Steam Injection on Last-Stage Blade Temperature of Low Pressure Steam Turbine at Low Volume Flow Condition

2017 ◽  
Author(s):  
Can Ma ◽  
Jun Wu ◽  
Yuansheng Lin
Keyword(s):  
Steam Turbine ◽  
Nuclear Power ◽  
Reverse Flow ◽  
Three Dimensional ◽  
Steam Injection ◽  
Low Pressure ◽  
Volume Flow ◽  
Pressure Steam ◽  
Last Stage ◽  
Low Volume

In the nuclear power plant, the last stage of the low pressure steam turbine is characterized by long blades. These long blades operate under severe working conditions with wet steam flow and strong mechanical stress. At the start up and shut down operating condition where the volume flow is extremely low, the last stage blades operate in ventilation conditions where there is significant reverse flow in the exhaust and the last stage. In such a condition, the reverse flow would cause significant increase in the blade temperature. In addition, the rotating reverse flow would increase the vibration of the rotor blade. Such temperature increase and enhanced vibration can cause blade damage and force the machine to be shut down. In previous work, the steam injection in the last stage has been proposed as a promising method to decrease the reverse flow at low volume flow conditions, which reduces the stall cell size in the last stage blade. This work investigates the effect of the steam injection process on the blade temperature distribution by conducting three-dimensional flow simulations. Various steam injection configurations are compared in this work and the major consideration to be noted in the design process is discussed.

Blade Vibration Monitoring in a Low-Pressure Steam Turbine

2018 ◽  
Author(s):  
Radosław Przysowa
Keyword(s):  
Embedded System ◽  
Steam Turbine ◽  
Turbine Blades ◽  
Low Pressure ◽  
Vibration Monitoring ◽  
Blade Vibration ◽  
Collaborative Project ◽  
Pressure Steam ◽  
The Embedded System ◽  
Start Ups

A tip-timing system is used in a coal power station to investigate and mitigate excessive blade vibrations in the exit stage of the low-pressure steam turbine. There are presented hardware and software solutions used to monitor blade responses as well as the analyses of amplitude and frequency trends observed during the 5-year collaborative project, including operation at the nominal speed and during the shutdowns and start-ups. The transition from data acquisition to the embedded system with the partial reuse of tip-timing algorithms and LabView code is demonstrated. The proposed system processes the data coming from the turbine blades in real time and operates autonomously or under the supervision of the PC-based client program connected to the network. Acquired data are stored in a cyclic buffer and can be transferred to the host. The stack pattern is used to distinguish blades and calculate rotating reference. Tip deflection is analysed statistically and evaluated against defined reference patterns.

Paper 9: The Removal of Water from Low-Pressure Steam Turbine Blades by Trailing-Edge Suction Slots

1967 ◽  
Vol 182 (8) ◽  
pp. 94-103 ◽  
Author(s):  
D. J. Ryley ◽  
G. J. Parker
Keyword(s):  
Steam Turbine ◽  
Turbine Blades ◽  
Low Pressure ◽  
Operating Conditions ◽  
Trailing Edge ◽  
Full Size ◽  
Hollow Blade ◽  
Pressure Steam ◽  
Steam Turbine Blades ◽  
Suction Slot

This paper reports an experimental research undertaken to explore the performance of a suction slot located in the trailing edge of a representative low-pressure steam turbine fixed blade. Tests have been made on a 1-in wide section of a full-size hollow blade mounted in a single-blade test section. Typical turbine pressures were reproduced down to 3 inHg (abs.), and blade exit Mach numbers varied in the range 0·57–1·10. With round entry lips, the slot operated satisfactorily in any blade orientation, as it completely removed quantities of water that were in excess of the amount expected under operating conditions. Square entry lips gave somewhat poorer performance.

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