# US 8,571,911 B1 · Facility life management method

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- Number: US 8,571,911 B1
- Document ID: US8571911B1
- Status: Granted
- Kind: B1
- Application number: 10/298,157
- Filed: 2002-11-15
- Granted: 2013-10-29
- Earliest claimed: 2001-11-16
- Assignees: Westinghouse Electric Corp.
- Applicants: Theodore A. Meyer; Robert K. Perdue; Warren H. Bamford; Edward Terek; G. Gary Elder; Joel Woodcock
- Inventors: Theodore A. Meyer; Robert K. Perdue; Warren H. Bamford; Edward Terek; G. Gary Elder; Joel Woodcock
- Web page: https://patentgrep.com/patent/US8571911B1

## CPC

- G06Q 10/04: Forecasting or optimisation specially adapted for administrative or management purposes, e.g. linear programming or "cutting stock problem" (market predictions or forecasting for commercial activities G06Q30/0202)
- G06Q 10/06: Resources, workflows, human or project management; Enterprise or organisation planning; Enterprise or organisation modelling
- G06Q 10/20: Administration of product repair or maintenance
- G06Q 50/06: Energy or water supply
- Y04S 10/50: Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
- G06Q: INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES; SYSTEMS OR METHODS SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES, NOT OTHERWISE PROVIDED FOR
- Y04S: SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS

## Abstract

An improved method of selecting and planning the performance of various maintenance activities on a facility such as a nuclear power plant includes determining the net present value of a number of future net savings that are expected to result from performance of the maintenance activity at a given time, and selecting and planning the maintenance activities in a fashion that maximizes net present value. The method includes, for each of a number of components and a number of time periods, determining a change in the probability that a component will fail within a time period, with the change resulting from an assumption that a maintenance activity is performed. The change in probability is multiplied with the losses associated with a failure in order to determine a gross savings from which costs are subtracted to determine net savings. The probabilities of failure may be determined from a probability failure model that has been derived from multiple sets of failure data that are characterized by Weibull distributions and are mathematically combined according to Bayes' Theorem. The maintenance activities may also be optimized according to a number of budget figures. An apparatus for performing the method is also disclosed.

## Claims

### Claim 1

A method of employing a computer in optimizing the timing of a number of maintenance activities that relate to a number of elements of a facility, the method comprising:
for each maintenance activity, employing the computer in:
determining a number of failure probabilities of an element based upon an assumption of performance of the maintenance activity at a given time,
employing at least some of the number of failure probabilities in determining a number of changes in probability of failure of the element based upon the assumption of performance of the maintenance activity at the given time, and
employing at least some of the number of changes in probability of failure in calculating a number of expected net savings based upon the assumption of performance of the maintenance activity at the given time;
employing the computer in performing said determining, employing, and calculating for each of a number of assumed given times of performance of the maintenance activity;
for each of at least some of the maintenance activities, employing the computer in determining the given time at which the corresponding expected net savings result in a substantially maximum net present value; and
outputting from the computer a plan for the proactive performance of a number of the maintenance activities that is based at least in part upon said determining the given time.

### Claim 2 (depends on 1)

The method as set forth in claim 1, in which, as to at least some of the maintenance activities, said determining the given time at which the corresponding expected net savings result in a substantially maximum net present value includes employing the computer in determining a monetary expenditure at the given time for the maintenance activity, and further including employing the computer in determining, for each of a number of given times, a sum of the monetary expenditures planned to be made at the given time based upon the maintenance activities identified for the given time.

### Claim 3 (depends on 2)

The method as set forth in claim 2, in which a budget amount is associated with each given time, and in which, as to at least some of the maintenance activities, said determining the given time at which the corresponding expected net savings result in a substantially maximum net present value includes employing the computer in identifying the maintenance activities at the given time in which:
the corresponding expected net savings result in a substantially maximum net present value; and
the sum of the related monetary expenditures corresponding with the given time is no greater than the budget amount associated with the given time.

### Claim 4 (depends on 3)

The method as set forth in claim 3, in which said identifying the maintenance activities includes, as to at least some of the maintenance activities, employing the computer in considering a profitability index associated with the maintenance activity.

### Claim 5 (depends on 1)

The method as set forth in claim 1, in which said determining a number of failure probabilities includes employing the computer in mathematically combining a first set of failure data with a second set of failure data.

### Claim 6 (depends on 5)

The method as set forth in claim 5, in which said mathematically combining the first set of failure data with the second set of failure data includes employing Bayes' Theorem to combine the first and second sets of failure data.

### Claim 7 (depends on 5)

The method as set forth in claim 5, in which the first and second sets of failure data each include at least one of:
data relating to a fleet which includes at least a portion of the facility;
data relating to an industry which includes the facility;
data relating specifically to the facility;
data from an expert;
data from a manufacturer; and
another set of failure data resulting from mathematically combining of a pair of sets of failure data.

### Claim 8 (depends on 1)

The method as set forth in claim 1, in which said determining the given time includes:
selecting one of the elements according to a number of criteria;
identifying a number of failure mechanisms for the selected element; and
identifying a number of the maintenance activities to correspond with the identified failure mechanisms.

### Claim 9 (depends on 8)

The method as set forth in claim 8, in which the criteria include at least one of importance to production, importance to safety, maintenance concerns, regulatory compliance, risk significance, component failure cost significance, and impact on a performance indicator.

### Claim 10 (depends on 8)

The method as set forth in claim 8, in which a weighting factor is applied to at least one of the criteria.

### Claim 11 (depends on 8)

The method as set forth in claim 8, further comprising, as to at least some of the elements, selecting as the one of the elements a sub-component of an element.

### Claim 12 (depends on 1)

The method as set forth in claim 1, in which said calculating a number of expected net savings based upon the assumption of performance of the maintenance activity at the given time includes, for at least some of the maintenance activities, employing the computer in determining at least one of a number of net revenue gains and a number of expenses avoided that correspond with performance of the maintenance activity at the given time.

### Claim 13 (depends on 12)

The method as set forth in claim 12, in which said determining at least one of a number of net revenue gains and a number of expenses avoided includes, for at least some of the maintenance activities, basing at least in part the at least one of a number of net revenue gains and a number of expenses avoided upon the failure probabilities of the element.

### Claim 14 (depends on 12)

The method as set forth in claim 12, in which said determining a number of net revenue gains includes employing the computer in determining for each of at least some of the number of net revenue gains the product of an average loss of revenue per failure event multiplied with one of the changes in probability of failure.

### Claim 15 (depends on 12)

The method as set forth in claim 12, in which said determining a number of expenses avoided includes employing the computer in determining for each of at least some of the number of expenses avoided the product of an average expense per failure event multiplied with one of the changes in probability of failure.

### Claim 16 (depends on 1)

The method as set forth in claim 1, in which said determining the given time includes, as to at least some of the maintenance activities, determining a maintenance interval for the maintenance activity.

### Claim 17 (depends on 16)

The method as set forth in claim 16, in which the facility has an expected lifetime, and in which said determining a maintenance interval for the maintenance activity includes employing the computer in calculating a net present value of the expected net savings resulting from an assumption that the maintenance activity is performed at each of the maintenance intervals throughout the expected lifetime of the facility.

### Claim 18 (depends on 1)

The method as set forth in claim 1, in which, as to at least some of the maintenance activities, said determining the given time includes employing the computer in identifying a time range within which the performance of the maintenance activity will achieve a substantially maximum net present value from the resulting expected net savings.

### Claim 19 (depends on 1)

The method as set forth in claim 1, in which said determining the given time includes employing the computer in:
determining whether or not the substantial maximum of the net present values is a negative amount; and
refraining from planning to perform of the maintenance activity if the substantial maximum of the net present values is a negative amount.

### Claim 20 (depends on 1)

The method as set forth in claim 1, in which said determining the given time includes employing the computer in planning the performance of the maintenance activity at the time of substantially maximum net present value.

### Claim 21 (depends on 20)

The method as set forth in claim 20 wherein said outputting comprises displaying on a chart the planned maintenance activities and the times for performance thereof.

### Claim 22 (depends on 21)

The method as set forth in claim 21, in which said displaying on a chart includes listing on the chart the element, the nature of the maintenance activity to be performed with respect to the element, and the time for performance of the maintenance activity.

### Claim 23 (depends on 22)

The method as set forth in claim 22, in which said displaying on a chart includes displaying the information in a graphical form.

### Claim 24

A method of employing a computer in determining whether or not to plan the performance a maintenance activity that relates to an element of a facility, the method comprising:
employing the computer in:
determining a number of failure probabilities of the element based upon an assumption of performance of the maintenance activity at a given time,
employing at least some of the number of failure probabilities in determining a number of changes in probability of failure of the element based upon the assumption of performance of the maintenance activity at the given time, and
employing at least some of the number of changes in probability of failure in calculating a number of expected net savings based upon the assumption of performance of the maintenance activity at the given time;
employing the computer in performing said determining, employing, and calculating for each of a number of assumed given times of performance of the maintenance activity;
for each given time, employing the computer in calculating a net present value of the expected net savings;
employing the computer in identifying the maximum amount among the net present values;
employing the computer in determining whether the maximum amount is a positive amount or a negative amount; and
outputting from the computer a plan for the proactive performance of the maintenance activity that is based at least in part upon said determining whether the maximum amount is a positive amount of a negative amount.

### Claim 25 (depends on 24)

The method as set forth in claim 24, further comprising employing the computer in planning the performance of the maintenance activity based substantially upon whether the maximum amount is a positive amount or a negative amount.

### Claim 26 (depends on 25)

The method as set forth in claim 25, in which said planning the performance of the maintenance activity includes planning the performance of the maintenance activity only if the maximum amount is a positive amount.

### Claim 27 (depends on 26)

The method as set forth in claim 26, in which said planning the performance of the maintenance activity includes employing the computer in planning the performance of the maintenance activity at the given time corresponding with the maximum amount.

### Claim 28 (depends on 24)

The method as set forth in claim 24, in which said determining a number of failure probabilities includes employing the computer in mathematically combining a first set of failure data with a second set of failure data to form a posterior set of failure data.

### Claim 29 (depends on 28)

The method as set forth in claim 28, in which said mathematically combining the first set of failure data with the second set of failure data includes employing Bayes' Theorem to combine the first and second sets of failure data to form the posterior set of failure data.

### Claim 30 (depends on 29)

The method as set forth in claim 29, in which the first set of failure data is characterized by a first Weibull distribution, in which the second set of failure data is characterized by a second Weibull distribution, and in which the posterior set of failure data is characterized by a posterior Weibull distribution.

### Claim 31 (depends on 28)

The method as set forth in claim 28, in which the first and second sets of failure data each include at least one of:
data relating to a fleet which includes at least a portion of the facility;
data relating to an industry which includes the facility;
data relating specifically to the facility;
data from an expert;
data from a manufacturer; and
another set of failure data resulting from mathematically combining of a pair of sets of failure data.

### Claim 32 (depends on 24)

The method as set forth in claim 24, in which said calculating a number of expected net savings based upon the assumption of performance of the maintenance activity at the given time includes employing the computer in determining at least one of a number of net revenue gains and a number of expenses avoided that correspond with performance of the maintenance activity at the given time.

### Claim 33 (depends on 32)

The method as set forth in claim 32, in which said determining at least one of a number of net revenue gains and a number of expenses avoided includes basing the at least one of a number of net revenue gains and a number of expenses avoided at least in part upon the failure probabilities of the element.

### Claim 34 (depends on 32)

The method as set forth in claim 32, in which said determining a number of net revenue gains includes employing the computer in determining for each of at least some of the number of net revenue gains the product of an average loss of revenue per failure event multiplied with one of the changes in probability of failure.

### Claim 35 (depends on 32)

The method as set forth in claim 32, in which said determining a number of expenses avoided includes employing the computer in determining for each of at least some of the number of expenses avoided the product of an average expense per failure event multiplied with one of the changes in probability of failure.

### Claim 36

A method of employing a computer in maintaining a facility, the facility including a number of elements, the method comprising:
selecting a number of the elements according to a number of criteria;
identifying a number of failure mechanisms for the selected elements;
developing a number of the maintenance activities to correspond with the failure mechanisms;
for each maintenance activity, employing the computer in:
determining a number of failure probabilities of an element based upon an assumption of performance of the maintenance activity at a given time,
employing at least some of the number of failure probabilities in determining a number of changes in probability of failure of the element based upon the assumption of performance of the maintenance activity at the given time, and
employing at least some of the number of changes in probability of failure in calculating a number of expected net savings based upon the assumption of performance of the maintenance activity at the given time;
employing the computer in performing said determining, employing, and calculating for each of each of a number of assumed given times of performance of the maintenance activity;
for each of at least some of the maintenance activities, employing the computer in determining the given time in which the corresponding expected net savings result in a substantially maximum net present value; and
outputting from the computer a plan for the proactive performance of a number of the maintenance activities that is based at least in part upon said determining the given time.

### Claim 37 (depends on 36)

The method as set forth in claim 36, in which, as to at least some of the maintenance activities, said determining the given time includes employing the computer in determining a monetary expenditure at the given time for the maintenance activity, and further including employing the computer in determining, for each of a number of given times, a sum of the monetary expenditures planned to be made at the given time based upon the maintenance activities planned to be performed at the given time.

### Claim 38 (depends on 37)

The method as set forth in claim 37, in which a budget amount is associated with each given time, and in which, as to at least some of the maintenance activities, said determining the given time includes employing the computer in identifying the maintenance activities at the given time in which:
the corresponding expected net savings result in a substantially maximum net present value; and
the sum of the related monetary expenditures planned to be made at the given time is no greater than the budget amount associated with the given time.

### Claim 39 (depends on 38)

The method as set forth in claim 38, in which said identifying the maintenance activities includes, as to at least some of the maintenance activities, employing the computer in considering a profitability index associated with the maintenance activity.

### Claim 40 (depends on 36)

The method as set forth in claim 36, in which said determining the given time includes employing the computer in planning the performance of the maintenance activity at the time of substantially maximum net present value.

### Claim 41 (depends on 40)

The method as set forth in claim 40, further comprising performing the maintenance activities substantially as planned.

### Claim 42

An apparatus for optimizing the timing of a number of maintenance activities that relate to a number of elements of a facility, the apparatus comprising a computer having stored thereon software which, when executed on the computer, causes the computer to perform operations comprising:
determining a number of failure probabilities of an element based upon an assumption of performance of a maintenance activity at a given time,
employing at least some of the number of failure probabilities in determining a number of changes in probability of failure of the element based upon the assumption of performance of the maintenance activity at the given time, and
employing at least some of the number of changes in probability of failure in calculating a number of expected net savings based upon the assumption of performance of the maintenance activity at the given time;
performing said determining, employing, and calculating for each of a number of assumed given times of performance of the maintenance activity;
determining the given time at which the corresponding expected net savings result in a substantially maximum net present value; and
outputting a plan for the proactive performance of the maintenance activity that is based at least in part upon said determining the given time.