Creep Damage and Life Assessment of Fossil Power Plant.

As a number of aged fossil power plants recently increased, the precise life assessment of critical equipments gets to be important more than ever. Despite of infrequent likelihood of failure, the equipments in high pressure and temperature operation condition have traditionally been considered as critical because of huge consequence of the equipments and hence life assessment of fossil power plant has been focused on all of the severe operated equipments for past decades. Nowadays, with Risk-Based Inspection technology being developed rapidly, most of the power plant utilities get a chance to reduce the scope of the inspection and test and to extend the interval for the life assessment. This paper provides methodology based on Risk-Based Inspection technology to optimize the life assessment work scope and interval and also demonstrates the enhanced life assessment procedure including risk assessment of equipments.

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THE LIFE ASSESSMENT OF STEAM TURBINE ROTORS FOR FOSSIL POWER PLANTS

International Journal of Modern Physics B ◽

10.1142/s0217979206041379 ◽

2006 ◽

Vol 20 (25n27) ◽

pp. 4371-4376

Author(s):

SUNGHO CHANG ◽

GEEWOOK SONG ◽

BUMSHIN KIM ◽

JUNGSEB HYUN ◽

JEONGSOO HA

Keyword(s):

Power Plant ◽

Steam Turbine ◽

Rotational Speed ◽

Power Plants ◽

Thermal Power ◽

Creep Damage ◽

Life Assessment ◽

Life Extension ◽

Start Up ◽

Operational Life

The operational mode of thermal power plants has been changed from base load to duty cycle. From the changeover, fossil power plants cannot avoid frequent thermal transient states, for example, start up and stop, which results in thermal fatigue damage at the heavy section components. The rotor is the highest capital cost component in a steam turbine and requires long outage for replacing with a new one. For an optimized power plant operational life, inspection management of the rotor is necessary. It is known in general that the start-up and shutdown operations greatly affect the steam turbine life. The start-up operational condition is especially severe because of the rapid temperature and rotational speed increase, which causes damage and reduction of life of the main components life of the steam turbine. The start-up stress of a rotor which is directly related to life is composed of thermal and rotational stresses. The thermal stress is due to the variation of steam flow temperature and rotational stress is due to the rotational speed of the turbine. In this paper, the analysis method for the start-up stress of a rotor is proposed, which considers simultaneously temperature and rotational speed transition, and includes a case study regarding a 500MW fossil power plant steam turbine rotor. Also, the method of quantitative damage estimation for fatigue-creep damage to operational conditions, is described. The method can be applied to find weak points for fatigue-creep damage. Using the method, total life consumption can be obtained, and can be also be used for determining future operational modes and life extension of old fossil power units.

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Progress in life assessment and design methodology for fossil power plant components

International Journal of Pressure Vessels and Piping ◽

10.1016/0308-0161(94)90093-0 ◽

1994 ◽

Vol 57 (1) ◽

pp. 7-20 ◽

Cited By ~ 13

Author(s):

T. Endo

Keyword(s):

Power Plant ◽

Design Methodology ◽

Life Assessment ◽

Fossil Power Plant ◽

Plant Components

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Progress in life assessment and design methodology for fossil power plant components Endo, T. Int. J. Pressure Vessels Piping (1994) 57 (1), 7–20

International Journal of Fatigue ◽

10.1016/0142-1123(95)98945-y ◽

1995 ◽

Vol 17 (3) ◽

pp. 229

Keyword(s):

Power Plant ◽

Design Methodology ◽

Pressure Vessels ◽

Life Assessment ◽

Fossil Power Plant ◽

Plant Components

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Power Plant Life/Risk Assessment Techniques

2002 International Joint Power Generation Conference ◽

10.1115/ijpgc2002-26101 ◽

2002 ◽

Cited By ~ 2

Author(s):

M. A. Clark ◽

R. Browne ◽

M. Flaman ◽

E. M. LeHockey ◽

I. Thompson

Keyword(s):

Power Plant ◽

Asset Management ◽

Power Plants ◽

Orientation Imaging Microscopy ◽

Creep Damage ◽

High Energy ◽

Life Assessment ◽

Original Design ◽

Type Iv ◽

Plant Operations

Many fossil power plants in N. America are now required to operate in excess of 20 years beyond their original design life. To ensure safe reliable operation, life assessment of key high-risk components is required. Life assessment of older power plant requires the application of many diverse techniques and the integration of several engineering disciplines with plant operations experience. Traditional approaches to life assessment of high temperature components will be described and illustrated with examples taken from experience on large coal fired plants from the old Ontario Hydro system. These results will include a number of high energy piping welds with approximately 160,000 hours of service that contain intercritical region heat affected zone (HAZ) creep damage (Type IV). These welds have been monitored through in-situ metallography techniques for over 20,000 hours since damage was first detected. New techniques are also being developed or employed: miniature sample testing for evaluating creep and fracture properties along with miniature EDM sample removal techniques. The use of innovative mechanical scratch gauges for the purpose on-line strain monitoring of mechanical or civil structures. The use of orientation imaging microscopy (OIM) for simultaneous comprehensive characterization of the interaction between residual plastic strains, texture, grains size distribution and other crystallographic features as applied to root cause failure analysis. Finally risk based asset management software RBMS for the purpose of detailed component assessments. Examples/results of these techniques will also be presented in the paper.

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