Cycle monitoring method and apparatus
First Claim
1. A fatigue cycle monitoring method using a sensor for monitoring a mechanical component, said method comprising the steps of:
- (a) sampling a sensor signal from the sensor and detecting a transient;
(b) producing a compressed transient from the sensor signal after the transient is detected in the sensor signal; and
(c) computing fatigue on the component from the compressed transient.
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Abstract
The present invention is a cycle monitoring system and method that acquires, logs and analyzes analog and/or digital signals from component sensors in a process control plant such as a nuclear power plant. The system continuously monitors the sensors and records steady-state and transient phenomena. Compression of the data is performed to reduce storage load. The compression ratio for transient data is driven by a threshold indicating a measurement signficant to stress determination. Transient data is retained at a higher sampling rate, so that the parameters of transient such as the maximum value can be determined for stress analysis. The stress analysis determines pressure and thermal stresses which are used to calculate a usage factor which indicates the stress age and thus the remaining life of a component. The system provides estimates of fatigue accumulation associated with selected locations of critical power plant components. Measurements of plant process and response parameters are used to provide data for calculation of fatigue accumulation. The system includes a computer containing a database that includes thresholds and response characteristics of the plant components to varying types of stress. The process required to calculate fatigue for monitored components and locations uses Duhamels integral to calculate transient stress, combines the transient stress with other stresses to produce a usage factor from stress ranges designating when a stress cycle has occurred. The system can be used to plan routine maintenance, repair and replacement decision, and to justify alternative plant operation modes and life extension.
101 Citations
13 Claims
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1. A fatigue cycle monitoring method using a sensor for monitoring a mechanical component, said method comprising the steps of:
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(a) sampling a sensor signal from the sensor and detecting a transient; (b) producing a compressed transient from the sensor signal after the transient is detected in the sensor signal; and (c) computing fatigue on the component from the compressed transient. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A fatigue cycle monitoring method for sensor monitoring a mechanical component in a nuclear power plant, said method comprising the steps of:
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(a) sampling a sensor signal from the sensor at a sampling rate; (b) checking integrity of the sensor signal; (c) comparing the sensor signal to first threshold range limit values; (d) storing sensor samples in a storage at a first storage rate if the sensor signal is within the first threshold range limit values; (e) storing sensor signal samples in the storage at a second storage rate higher than said first storage rate if the sensor signal is equal to or outside the first threshold range limit values; (f) continuing to store at the second storage rate until the sensor signal has been within the first threshold range limit values for a predetermined period; (g) comparing the stored sensor samples stored at the second rate to second threshold range limit values and storing a transient sensor sample in the storage when successive sensor signal samples are outside the second threshold range limit values; (h) comparing the stored sensor signal samples stored at the second storage rate and storing the maximum and minimum sensor signal samples in the storage when a maximum or minimum are detected, respectively; (i) computing component pressure stress from pressure transient sensor samples; (j) computing general thermal component stress; (k) computing transient thermal component stress by performing Duhamels integral on temperature transient sensor samples; (l) obtaining predetermined load stresses from the storage; (m) adding the component pressure stress, the general thermal component stress, the transient thermal component stress and the predetermined load stresses; (n) determining a stress intensity range from the added stresses; and (o) producing a component usage factor from the stress intensity range indicating the fatigue on the component with the component usage factor.
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11. A cycle monitoring apparatus for a sensor monitoring a component, said apparatus comprising:
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sampling means for sampling a sensor signal producing sensor signal samples and detecting a transient in the sensor signal samples; compression means for compressing the sensor signal samples into a compressed transient after the transient is detected; and fatigue determination means for determining component fatigue from the compressed transient. - View Dependent Claims (12, 13)
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Specification