Corrosion-erosion trend monitoring and diagnostic system

• US 4,935,195 A
• Filed: 08/29/1988
• Issued: 06/19/1990
• Est. Priority Date: 08/29/1988
• Status: Expired due to Fees

• Current Assignee: Westinghouse Electric Sweden AB (Brookfield Asset Management Incorporated)
• Original Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Inventors: Schmertz, John C., Roarty, David H., Palusamy, Sam S.
• Primary Examiner(s): Walsh, Donald P.
• Application Number:
  US07/237,537
• Time in Patent Office: 659 Days
• Field of Search: 376/249, 376/305, 376/215, 73/570, 73/592
• US Class Current: 376/249
• CPC Class Codes: G01N 17/00 Investigating resistance of materials to the weather, to corrosion, or to light
• CPC Class Codes: G07C 3/00 Registering or indicating the condition or the working of machines or other apparatus, other than vehicles
• CPC Class Codes: G21C 17/017 Inspection or maintenance of pipe-lines or tubes in nuclear installations
• CPC Class Codes: Y02E 30/30 Nuclear fission reactors

Abstract

A system for analyzing containment integrity of a containment system includes data storage for inspection data and characteristic data and a data evaluation processor for evaluating the inspection data. A data acquisition system is used for periodically obtaining wall thicknesses of selected components in the containment system. After data validation, the actual wall thicknesses are stored as the inspection data in the data storage. The data evaluation processor analyzes the present pipe wall integrity in light of stress calculated from the characteristic data including operational conditions and material properties. In addition, the data evaluation processor analyzes the trend in change of wall thickness to forecast future wall thicknesses.

Claims

1. A method of assessing wall thinning rate of a containment system containing a substance and subject to erosion and corrosion, comprising the steps of:

(a) storing characteristic data for at least one component of the containment system to be monitored;

(b) storing inspection data for the at least one component; and

(c) automatically evaluating the inspection data based on the characteristic data to produce an assessment of the wall thinning rate of the at least one component.

2. A method as recited in claim 1,

further comprising the steps of:

(d) measuring actual wall thickness of the at least one component to obtain the inspection data; and

(e) repeating steps (b) and (d) periodically,

wherein step (a) comprises the step of (ai) storing nominal wall thickness as part of the characteristic data, and

wherein step (c) comprises the step of (ci) analyzing the inspection data and characteristic data too determine a trend in change of the actual wall thickness.

3. A method as recited in claim 2, wherein the containment system includes a piping system,

wherein step (a) further comprises the step of (aii) storing at least one of a component identification number, a description of component structure, pipe size, material properties and operating conditions as the characteristic data.

4. A method as recited in claim 3, further comprising the step of (f) automatically selecting the at least one component from among all components of the containment system in dependence upon susceptibility to corrosion and erosion and a predicted rate of corrosion-erosion.

5. A method as recited in claim 4,

wherein step (f) includes automatically selecting a plurality of components in the containment system as the at least one component,

wherein step (a) further comprises the step of (aiii) storing an inspection grid and a component location as part of the characteristic data for each of the components selected in step (f), and

wherein said measuring in step (d) is performed on the component selected in step (f) in accordance with the inspection grid stored in step (a) for a corresponding component.

6. A method as recited in claim 5,

further comprising the step of (g) storing an inspection identifier for each of the components measured in step (b) when said measuring of the corresponding component occurs, and

wherein step (b) comprises storing the inspection data at locations determined in dependence upon the inspection identifier stored in step (g) and the component identification number stored in step (a).

7. A method as recited in claim 3, wherein step (c) further comprises the steps of:

(cii) comparing the inspection data with predetermined ranges to determine validity of the inspection data and locations of excessive wall thinning;

(ciii) calculating stress on the at least one component in dependence upon the characteristic data; and

(civ) evaluating the containment integrity of the at least one component in dependence upon the actual wall thickness most recently measured in step (d) and the stress calculated in step (ciii).

8. A method as recited in claim 7, wherein step (ci) comprises extrapolating from the inspection data stored during completed repetitions of step (b) using one of a curve fitting algorithm and a predetermined corrosion-erosion rate.

9. A method as recited in claim 8, further comprising the step of (h) plotting predicted wall thickness of the at least one component.

10. A method as recited in claim 2, further comprising the step of (f) plotting the inspection data to produce a graphical representation of wall thinning within the at least one component.

11. A method as recited in claim 2, further comprising the step of (f) producing a prioritized indication of maintenance required on the at least one component in dependence upon said analyzing in step (ci).

12. A system for assessing wall thinning rate of a containment system containing a substance and subject to erosion and corrosion, comprising:

storage means for storing characteristic data and inspection data for at least one component of the containment system to be monitored;

acquisition means for acquiring the inspection data including actual wall thickness of the at least one component; and

evaluation means for automatically evaluating the inspection data based on the characteristic data to produce an assessment of the wall thinning rate of the at least one component.

13. A system as recited in claim 12, wherein the containment system includes a piping system measured using ultrasonic testing equipment,

wherein the characteristic data includes at least one of a component identification number, a description of component structure, pipe size, nominal wall thickness, material properties, operating conditions, an inspection grid and a component location for the at least one component, and

wherein said acquisition means comprises:

means for periodically acquiring the actual wall thickness of the at least one component from the ultrasonic testing equipment and an inspection identifier corresponding to the actual wall thickness; and

means for storing the actual wall thickness in said storage means at locations determined in dependence upon the inspection identifier and the component identification number.

14. A system as recited in claim 13, wherein said evaluation means includes:

means for evaluating the wall thinning rate of the at least one component in dependence upon the actual wall thickness most recently acquired and stress calculated in dependence upon the characteristic data; and

means for extrapolating from the inspection data acquired over a period of time for the at least one component to predict future wall thickness of the at least one component.

15. A system for assessing containment integrity of piping systems in a pressurized water nuclear reactor powered electricity generation plant, comprising:

storage means for storing characteristic data and inspection data for a plurality of components in the plant;

input means for inputting the characteristic data including component identification members, descriptions of component structure, pipe sizes, nominal wall thicknesses, material properties, locations of the components, operating conditions and inspection grids corresponding to the components;

acquisition means for repeatedly acquiring the inspection data, including actual wall thicknesses measured at a plurality of points on each of the components and for validating the inspection data by comparing the inspection data with predetermined ranges to identify errors and to identify any of the points which indicate excessive wall thinning; and

evaluation means for automatically evaluating the inspection data in dependence upon the actual wall thicknesses most recently acquired and stress calculated in dependence upon the characteristic data and for extrapolating from the inspection data acquired over a period of time for each of the components to predict future wall thicknesses of the components.