GB2594219A

GB2594219A - Plant maintenance management method and maintenance management system

Info

Publication number: GB2594219A
Application number: GB2110692.7A
Authority: GB
Inventors: Tanabe Masayuki
Original assignee: JGC Corp
Current assignee: JGC Corp
Priority date: 2019-09-11
Filing date: 2019-09-11
Publication date: 2021-10-20
Also published as: JP6821085B1; GB202110692D0; JPWO2021048956A1; WO2021048956A1

Abstract

[Problem] To provide art for formulating an equipment maintenance plan from the standpoint of improving the security of a plant. [Solution] A maintenance management method for a plant 1 for processing a fluid extracts a plurality of accidents that are expected to occur with equipment constituting the plant 1, and acquires both the frequencies of occurrence of accident-causing events that can cause the extracted plurality of accidents, and the probabilities of failure of safety devices for preventing occurrence of the accidents. Then the maintenance management method calculates risks which are values obtained by multiplying the frequencies of occurrence of the accident-causing events associated with each accident by the probability of failure of the safety device for the accident, and compares the calculated risks with a preset threshold value. Thereafter, the maintenance management method lists, as candidates to be subjected to maintenance work, the equipment and the safety device that are associated with each calculated risk that is greater than the threshold value.

Description

Title of Invention: PLANT MAINTENANCE MANAGEMENT METHOD AND MAINTENANCE MANAGEMENT SYSTEM

Technical Field

[0001] The present invention relates to a technology for performing maintenance management of equipment included in a plant.

Background Art

[0002] In a plant for processing fluid, a large number of equipment are installed. When those pieces of equipment fail, not only there is a hazard that the plant may shutdown (i.e., loss of production), but also the failure may cause a greater disaster, such as a fire or an environmental pollution. Thus, maintenance work for inspecting or repairing each piece of equipment installed in the plant is required.

[0003] Regarding the maintenance work, an extremely large number of equipment may be installed in the plant, and hence when every piece of equipment of the plant is inspected or repaired at the same frequency, such work is not efficient because a volume of the work may become enormous.

Thus, hitherto, from the viewpoint of increasing an availability (allowing a continued operation of the plant), the following maintenance plan has been created in general. Specifically, the maintenance work is performed at short intervals for equipment having a large impact on the operation of the plant, and the maintenance work is performed at long intervals for equipment having a small impact on the operation of the plant.

[0004] However, among equipment having redundancy, for example, there may be some equipment that have a relatively small impact from the viewpoint of the availability but are important from the viewpoint of increasing safety, for example, prevention of a fire and an environmental pollution. As described above, with the related-art maintenance work, it has been difficult to quantitatively grasp how much the work contributes to the safety of the plant.

[0005] In Patent Literature:, there is described a maintenance and inspection system configured to use process data and trend data on a plant as a plant signal for monitoring a plant equipment, and identify an inspection item of the plant equipment based on a result of determination of whether a measured value of the plant signal isabnormal. However,inPatentLiterature1,thereisnodescription of a technology for creating a maintenance plan from the viewpoint of increasing the safety of the plant.

Citation List Patent Literature [0006] [PTL 1] JP 2015-106391 A

Summary of Invention

Technical Problem [0007] The present invention has been made under the above-mentioned background, and provides a technology for creating a maintenance plan for equipment from the viewpoint of increasing safety of a plant.

Solution to Problem [0008] According to one embodiment of the present invention, there is provided a maintenance nanagement method for a plant for processing fluid, the maintenance management method including the steps of: extracting accident scenarios assumed to occur in equipment included in the plant; acquiring, for each of the accident scenarios that have been extracted, an occurrence frequency of an accident initiating event, which is likely to cause the each of the accident scenarios, and a probability of failure on demand of a safety device for preventing occurrence of the each of the accident scenarios; calculating, by a computer, a risk to compare the risk with a threshold value set in advance, the risk being a value obtained by multiplying the occurrence frequency of the accident initiating event relating to the each of the accident scenarios and the failure probability of the safety device relating to the each of the accident scenarios; and listing, for the accident scenarios, when the calculated risk is larger than the threshold value, equipment and a safety device that are relevant to the risk as maintenance work order priorities.

[0009] The maintenance management method for a plant may include the following features.

(a) When multiple safety devices are provided in order to prevent occurrence of the accident, the risk is calculated by multiplying the occurrence frequency of the accident initiating event by the failure probabilities of the multiple safety devices in order.

(b) The initial occurrence frequencyof the accident initiating event, which is acquired in the acquiring step, is obtained by a historical failure rate statistics data in plants, and the initial failure probability of the safety device, which is acquired in the acquiring step, is obtained by a historical failure statistic data of occurrence of a failure on demand of the safety device in plants. Then, for the incorporation of the specific plant failure record into the initial occurrence frequency of the accident initiating event or the initial failure probability of the safety device, Bayesian estimation is performed and the updated occurrence frequencies and the updated failure probabilities are obtained.

Advantageous Effects of Invention [0010] According to the present invention, when the risk, which is the value obtained by multiplying the occurrence frequency of the accident initiating event assumed to occur in the plant and the failure probability of the safety device for preventing occurrence of the accident, has become larger than the threshold value set in advance, the equipment and the safety device are listed as candidates to be subj ected to the maintenance work order priorities. As a result, it is possible to create a maintenance plan capable of maintaining the state in which the plant can operate safely by suppressing an increase in the risk of occurrence of the assumed accident.

Brief Description of Drawings

[0011] FIG. 1 is a block diagram for illustrating a maintenance management system for a plant according to an embodiment of the present invention.

FIG. 2 is a graph for showing an example of a probability distribution for occurrence of an accident initiating event before a specific plant failure record is incorporated.

FIG. 3 is a graph for showing an example of a probability distribution for occurrence of the accident initiating event after the specific plant failure record is incorporated.

FIG. 4 is an explanatory diagram for illustrating details of maintenance management to be executed through use of the maintenance management system.

FIG. 5 is an explanatory graph for showing transition of a risk of occurrence of an assumed accident.

FIG. 6 is a configuration diagram for illustrating a part of a processing plant for processing low-level radioactive waste.

FIG. 7 is an example of a calculation table for calculating a risk of occurrence of an accident assumed to occur in each piece of equipment installed in the processing plant.

Description of Embodiments

[0012] First, referring to FIG. 1 to FIG. 5, a description is given of an overview of a maintenance management system 2 for a plant according to an embodiment of the present invention.

FIG. 1 is ablock diagram for illustrating an overview of the maintenance management system 2 of this example and a plant 1. In the plant 1, maintenance management using the maintenance management system 2 is performed.

[0013] There is no particular limitation on the plant 1 as long as the plant 1 has a function of processing fluid. Examples of the plant 1 include: a natural gas plant for, for example, liquefying natural gas and separating and recovering natural gas liquid; a petroleum refinery plant for, for example, distilling and desulfurizing crude oil and various intermediate products; a chemical plant for producing petrochemical products, intermediate chemical products, polymers, and the like; a pharmaceutical plant for producing pharmaceuticals and intermediate products thereof; and a waste processing plant for processing low-level radioactive waste.

In the present application, the "fluid" also includes, in addition to gas and liquid, a granular material having flowability (e.g., powder, grain, and pellet).

[0014] In the plant 1, a large number of equipment are installed, which include various control (instrumentation) devices and electrical devices in addition to a column, a tank, a heat exchanger, and other such static equipment, a pump and other such mechanical equipment, and pipes provided between those static equipment and mechanical equipment. Those equipment include equipment for which maintenance work is to be performed based on a maintenance plan created through use of the maintenance management system 2 of this example.

[0015] The maintenance management system 2 of this example is able to list equipment being candidates to be subjected to the maintenance work order priorities, based on the viewpoint of suppressing an increase in a risk of an accident that may occur in each piece of equipment installed in the plant 1.

The maintenance management system 2 is constructed by a computer, for example. The computer constructing the maintenance management system 2 maybe installed in a main control room, which is located on the premises of the plant 1 to centrally control the plant 1, or may be installed at an office located in a place remote from the premises of the plant I. [0016] The maintenance management system 2 includes an information acquisition unit 21 configured to acquire information on the equipment of the plant 1, a storage unit 22 configured to store various types of information required for performing maintenance management, a risk assessment unit 23 configured to perform risk assessment of the equipment based on those pieces of information, and a notification unit 24 configured to notify a user of results of the risk assessment.

[0017] The information acquisition unit 21 is configured to acquire, out of the information on the equipment of the plant 1, an "occurrence frequency of accident initiating event" and a "probability of failure on demand of safety device" described later as information required for performing the maintenance management of the equipment. Those pieces of information may be individually input by the user, or maybe acquired from a database that is separately provided.

When data is individually input, the information acquisition unit 21 is constructed as an input terminal of the computer, for example. I/Thenthedatais acquired fromthe database, the information acquisition unit 21 is constructed as a terminal configured to read a storage medium or as a communication unit configured to perform data communication to/from the outside.

[0018] Further, as described later, the maintenance management system 2 may have a function of incorporating, into the "occurrence frequency of accident initiating event" and the "failure on demand of safety device (hereinafter sometimes referred to simply as 'safety device failure') ", historical failure statistics data of occurrence of the accident initiating event and the failure. From this viewpoint, the information acquisition unit 21 may acquire information on the past records of occurrence of those events. Further, the information acquisition unit 21 may include a calculation unit constructed by a computer configured to execute calculation for incorporating the specific plant historical failure record.

[0019] The storage unit 22 stores a database in which an accident (assumed accident) assumed to occur in each piece of equipment included in the plant 1, an accident initiating event that may cause each assumed accident and an occurrence frequency of the accident initiating event, a safety device for preventing occurrence of the assumed accident and a probability of failure on demand of the safety device, and a threshold value for assessing a risk calculated from those pieces of information are associated with one another.

[0020] It is preferred that assumed accidents be extracted exhaustively for each piece of equipment for which the maintenance management is to be performed by the maintenance management system 2. From this viewpoint, it is preferred that assumed accidents be extracted together with an engineer who is familiar with the equipment and processes of the plant 1 through use of a systematic method relating to safety assessment of the plant 1, such as a hazard and operability study (HAZOP) or failure mode and effects analysis (FEMA).

[0021] The accident initiating event is an event that may cause each of the extracted accidents. For example, it is assumed that, in a tank for storing fluid, liquid is received and delivered while a liquid level thereof is controlled. At this time, when a failure occurs in a control system for controlling the liquid level, there arises a hazard that the liquid may overflow. In this example, the "overflow of liquid" is the assumed accident, and the "failure in control system" is the accident initiating event.

[0022] The safety device is one type of device installed in the plant 1 in order to prevent occurrence of an accident even when an accident initiating event occurs. In the above-mentioned example, it is assumed that a liquid-level sensor for interlock for stopping reception of liquid is provided separately from a liquid-level instrument installed in the control system for controlling the liquid level. In this example, the "liquid-level sensor for interlock" is the safety device.

[0023] Regarding the accident initiating event described above, the number of times for which a predetermined accident initiating event may occur during a period (one year in this example) set in advance for equipment is the "occurrence frequency". Further, the number of times for which the safety device may fail to normally operate during a period (one year in this example) set in advance for a safety device is the "failure probability".

[0024] Statistic data of occurrence of the above-mentioned "accident initiating event" and "safety device failure" are continuously counted in the entire plant industry, and the "occurrence frequency of accident initiating event of each piece of equipment" and the "failure probability of each safety device", which are calculated based on those statistic data, are sold as a database. Whentheoperationofdieplant 1 is started, for example, such commercially-available data may be obtained to be stored in the storage unit 22 in association with each assumed accident.

Further, when the user owns other plants of the same type, for example, the "occurrence frequency of accident initiating event" and the "failure probability of safety device" of the other plants may be used.

[0025] Further, after the operation of the plant 1 is started, when the accident initiating event or the failure of the safety device has actually occurred in the plant 1, the "occurrence frequency of accident initiating event" or the "failure probability of safety device" may be calculated by incorporating records of occurrence of those events. For example, it is possible to incorporate the records of occurrence through use of Bayesian estimation.

[0026] Regarding a fault occurrence frequency of equipment (including a case in which the equipment is a safety device), a mean value of a time to failure and a variance thereof based on a lognormal uncertainty distribution are represented by Xmean and Var, respectively. At this time, the time to occurrence of a failure in_ the equipment cal-113e expressed through use of a suitable probability distribution. For example, a probability density of a gamma distribution can be represented by Expression (1) given below.

Pur(a) In this expression, a and represent (Xmean)2/Var, and Xmean/Var, respectively, and r represents a gamma (f) function.

[0027] At this time, for example, when Xmean andVar are regarded as a time to failure described in the commercially-available database and a variance of original data for obtaining the time to failure, respectively, Expression (1) given above can be understood as a change with time of the fault occurrence frequency from an initial state.

FIG. 2 shows a change with time of the fault occurrence frequency exhibited when Xmean=1.08x10 3 and Var=2.3x10 6 (u0=5.07x10 ' and 30-4.7x102).

[0026] At this time, it is assumed that the plant 1 includes five pieces of equipment of the sane type, and one fault has occurred as a result of operating those equipment for 20 years. It can be regarded that a fault that occurs once in one hundred years has occurred in the equipment. When posterior parameters (Xmean' and Var') are calculated based on this record of fault occurrence and the initial state (prior parameters Xmean and Var) through use of Bayesian estimation, the respective posterior parameters can be calculated through use of Expression (2) and Expression (3) given below.

Xmean ' = (a0+ (Number of Times of Fault Occurrence) )/ (30+ (Total Operating Time)) ... (2) Var'-(a0+(Number of Times of Fault Occurrence))/(30+(Total Operating Time))2 (3) FIG.3showsachangewithtimeofthefaultoccurrencefrequency exhibited after the past record of the equipment failure is incorporated. The parameters were as follows: Xmean'=2.65x10-3, Var=4.65x10-6, a0'=1.51, and D0'=5.7x102.

[0029] When the above-mentioned method is to be implemented, the information acquisition unit 21 acquires specific plant failure records of occurrence of the accident initiating event and the failure of the safety device (the number of times of occurrence and time to occurrence) relating to each piece of equipment installed in the plant 1. The information acquisition unit 21 may also perform the above-mentioned calculation based on the acquired information to store, in the storage unit 22, the "occurrence frequency of accident initiating event and failure probability of safety device" in which the specific plant failure records of occurrence are Incorporated.

The storage unit 22 further stores, in association with each assumed accident, a threshold value being an upper limit value of a range of allowable values of the risk calculated by the risk assessment unit 23.

[0030] The safety device to be managed by the maintenance management system 2 herein is not limited to a safety Instrument system (SIS), for example, the above-mentioned "liquid-level sensor for Interlock". Also for a safety device other than the safety instrument system, such as a safety relief valve or an alarm, data on a past record of occurrence of the "safety device failure" is incorporated and updated for use in the maintenance management. In addition to those safety devices, data on the past record of occurrence is similarly incorporated and updated also for "equipment that may cause accident initiating event (for example, a 'control valve' for the above-mentioned liquid level control)". The configuration in which data on the past records of occurrence of both of the failure of the safety device and the accident initiating event is incorporated and updated for use in the maintenance management is one of the features of the maintenance management system 2.

[0031] Next, the function of the risk assessment unit 23 is described. For example, in a case where a safety device for preventing occurrence of an assumed accident is installed in equipment, even when an accident initiating event occurs, the assumed accident does not occur as long as the safety device successfully operates. Further, even under a state in which the safety device does not successfully operate, the assumed accident does not occur as long as the accident initiating event does not occur.

That is, the assumed accident occurs when "the accident initiating event occurs" and "the safety device does not normally operate".

[0032] On the basis of the above-mentioned idea, the risk assessment unit 23 calculates a risk of occurrence of the assumed accident through use of Expression (4) given below.

Risk= (Occurrence Frequency of Accident initiating Event)x (Failure Probability of Safety Device) ... (4) In some equipment, multiple safety devices may be provided. In this case, the risk assessment unit 23 calculates the risk based on Expression (4)1 given below, in which failure probabilities of respective safety devices are multiplied in order. In Expression (4) ', an exemplary case in which two safety devices (primary safety device and secondary safety device) are included is given.

Risk= (Occurrence Frequency of Accident initiating Event)x (Failure Probability of Primary Safety Device)x (Failure Probability of Secondary Safety Device) ... (4)' [0033] As shown in FIG. 2 and FIG. 3, when the occurrence frequency and the failure probability are represented as a function of the time to occurrence of a failure, for example, a time point at which the relevant equipment was newly provided, updated, or repaired last is set as a zero point, and values of the occurrence frequency and the failure probability at a current time point are read to calculate the risk.

[0034] Further, the risk assessment unit 23 compares the calculated risk with the threshold value stored in the storage unit 22. When the calculated risk of an assumed accident is larger than the threshold value, it is assessed that the risk of occurrence of the assumed accident exceeds an allowable range. In this case, the risk assessment unit 23 outputs the comparison result to the notification unit 24.

[0035] When the notification unit 24 has acquired from the risk assessment unit 23 information indicating that the calculated risk is larger than the threshold value, the notification unit 24 outputs via a monitor 241, for example, information for identifying the equipment and the safety device that are relevant to the risk of the relevant assumed accident.

[0036] Referring to FIG. 4, a description is given of processing of creating a maintenance plan of the plant 1 to execute the maintenance plan through use of the maintenance management system 2 having the configuration described above.

First, accidents assumed to occur in equipment included in the plant 1 are extracted (Step 91). As described above, it is preferred to exhaustively extract accidents assumed to occur in the equipment to be subj ected to the maintenance management performed by this method. The extracted assumed accidents are stored in the storage unit 22.

[0037] Next, for each of the extracted assumed accidents, an accident initiating event that may cause an accident and a safety device for preventing occurrence of the accident are identified. Then, an occurrence frequency of the accident initiating event and a probability of failure on demand of the safety device are acquired through the information acquisition unit 21 (Step P2) . At this time, when multiple safety devices are provided to prevent the assumed accident, a failure probability of each of the safety devices is acquired. The acquired occurrence frequency and failure probability are stored in the storage unit 22 in association with the assumed accident.

[0038] After that, the risk assessment unit 23 selects an assumed accident, calculates a risk of the assumed accident, and then compares the risk with the threshold value (Step P3). When the calculated risk is larger than the threshold value, the equipment and the safety devices that are relevant to the risk are listed as maintenance target candidates, and the user is notified of the maintenance target candidates via the monitor 241.

The user, who has been notified of the maintenance target candidates, creates a specific maintenance schedule for the equipment and the safety devices, and sequentially inspects or repairs the equipment and the safety devices (Step P5).

[0039] For the repaired equipment or safety device, when the user inputs through, for example, the information acquisition unit 21 information indicating that the equipment has been repaired, the elapsed time of the probability distribution shown in FIG. 2 and FIG. 3 starts from a state in which the elapsed time has returned to the zero point. Then, the user reads, on the basis of the time that has elapsed since the start, the occurrence frequency of the next accident initiating event andthe probability of the next failure of the safety device. Further, when an accident initiating event or a safety device failure has actually occurred in the plant 1, the record of occurrence is incorporated based on the above-mentioned method. Those processing procedures also correspond to the acquisition of the occurrence frequency and the failure probability of Step P2 of FIG. 4.

[0040] Further, the maintenance management systam2 performs, based on a preset schedule, Step P2 to Step P5 for all of the assumed accidents stored in the storage unit 22 once a year, for example. Moreover, when equipment or a safety device is modified, updated, or additionally provided, for example, the extraction of assumed accidents of Step P1 may be newly performed for those equipment, and the cycle of from Step P2 to Step PS may be performed for the extracted assumed accidents together with other assumed accidents.

[0041] Through the execution of the processing described above, it is possible to create and execute a maintenance plan that is organized in association with each assumed accident. This feature is described with reference to FIG. 5. The horizontal axis of FIG. 5 represents an elapsed time, and the vertical axis of FIG. 5 represents a risk calculated for an assumed accident. The outlined circles shown in FIG. 5 represent a change in risk exhibited when the maintenance management of equipment and a safety device was performed through use of the maintenance management system 2, and the black circles shown in FIG. 5 represent a change in risk exhibited when the maintenance management was not performed.

[0042] For example, when no measure is taken, the risk becomes larger than the threshold value at a time point (1) shown in FIG. 5 as indicated by the black circle. Thus, for example, a primary safety device is inspected or repaired, to thereby keep the risk to be equal to or smaller than the threshold value. Then, risk assessment is similarly performed also at time points;2) and (3), and for example, the equipment is Inspected or repaired at the time point (2) and a secondary safety device is inspected or repaired at the time point (3). The maintenance work is performed in this manner so that the risk is kept to be equal to or smaller than the threshold value.

[0043] In the above-mentioned example, the notification unit 24 lists a plurality of candidates to be subjected to the maintenance work (equipment, primary safety device, and secondary safety device) in association with a predetermined assumed event. In this case, it is required to determine a specific equipment or safety device for which the maintenance work is to be performed. Thus, for example, the details of Expression (4)'mav be examined, and equipment whose occurrence frequency or failure probability has a greater effect of reducing the risk from among the occurrence frequencies and the failure probabilities of the individual equipment and safety devices may be selected as equipment to be subjected to the maintenance work. Further, the maintenance work may be performed for equipment that has not been inspected or repaired recently.

As another example, priorities may be assigned to safety devices and equipment from the viewpoint of importance by, for example, creating prioritized management items, which are important in terms of security, and a maintenance plan into which the prioritized management items are incorporated may be created to execute the maintenance work.

[0044] In the above, a description has been given of a method of performing the maintenance management of the equipment and the safety device of the general plan:. 1 through use of the maintenance management system 2. Next, referring to FIG. 6 and FIG. 7, a description is given of specific examples of the assumed accident, the accident initiating event, and the safety device by giving a case of a processing plant for processing low-level radioactive waste as an example.

[0045] FIG. 6 is an illustration of a part of the processing plant, which is configured to receive solid-liquid mixture fluid containing radioactive materials to process the fluid. A powder resin storage tank 31 is configured to receive a powder resin-containing waste liquid 311. After the powder resin-containing waste liquid 311 is left at rest, solid and liquid portions thereof are separated. Supernatant obtained as a result of the solid-liquid separation is discharged by a decanting pump 312 as decant liquid 313. Abead resin storage tank 32 is configured to receive a bead resin-containing waste liquid 321. After the bead resin-containing waste liquid 321 is left at rest, solid and liquid portions thereof are separated. Supernatant obtained as a result of the solid-liquid separation is discharged by a decanting pump 322 as decant liquid 323, or sent to a bead resin separate liquid tank 34. A filter crud storage tank 33 is configured to receive a filter crud-containing waste liquid 331. After the filter crud-containing waste liquid 331 is left at rest, solid and liquid portions thereof are separated. Supernatant obtained as a result of the solid-liquid separation is discharged by a decanting pump 332 as decant liquid 333. The bead resin separate liquid tank 34 is configured to receive supernatant liquid from the bead resin storage tank 32. After the supernatant liquid is left at rest, solid and liquid portions thereof are separated. Supernatant obtained as a result of the solid-liquid separation is sent, by a combination of a separate liquid pump 341 and open/close operations of open-close valves V1 to V3, to any one of the powder resin storage tank 31, the bead resin storage tank 32, and the filter crud storage tank 33.

[0046] FIG. 7 shows an example of a calculation table in which, for a part of accidents assumed to occur in the processing plant, an accident initiating event and an occurrence frequency thereof and a safety device and a failure probability thereof are listed to calculate a risk of occurrence of each assumed accident.

[0047] For example, an "overflow of powder resin storage tank 31" has a failure of a control system for controlling a resin level as the accident initiating event. To prevent this event, a resin level sensor for interlock is mounted as the safety device.

Then, a risk of occurrence of the assumed accident is calculated through use of Expression (4) based on an occurrence frequency of the accident initiating event and a failure probability of the safety device.

[0048] Further, for "damage to powder resin storage tank 31 due to hydrogen explosion" caused by radiolysis of water, a human error of erroneously stopping a tank vent processing system and a failure of a control system for controlling the tank vent processing system are given as the accident initiating events. When there are a plurality of accident initiating events, the occurrence frequency of each accident initiating event is summed up.

[0049] Meanwhile, multiple safety devices are mounted, and the safety devices include an air purge system being the primary safety device and an operation of restarting the tank vent processing system being the secondary safety device. A risk of occurrence of the assumed accident in this case is calculated based on Expression (4) ' by multiplying the total value of the occurrence frequency of the accident initiating event by the failure probabilities of the primary and secondary safety devices in order.

Calculation of the risk corresponding to each assumed accident shown in FIG. 7 is executed by the maintenance management system 2.

[0050] According to the maintenance management sysem 2 of this embodiment, when the risk, which is a value obtained by multiplying the occurrence frequency of the accident initiating event of an accident assumed to occur in the plant 1 and the failure probability of the safety device for preventing occurrence of the accident, has become larger than the threshold value set in advance, the equipment and the safety device are listed as the candidates to be subjected to the maintenance work order priorities. Asa result, it is possible to create a maintenance plan capable of maintaining a state in which the plant 1 can operate safely by suppressing an increase in the risk of occurrence of the assumed accident.

[0051] In this case, the related-art availability-based maintenance management may be used to supplement the maintenance management that uses the maintenance management system 2. For example, there may be given an exemplary case in which the related-art availability-based maintenance management is performed for equipment that is not included in the maintenance management that uses the maintenance management system 2 because the equipment is not relevant to the assumed accident, for example.

Further, for a single plant 1, the maintenance management system 2 and the related-art availability-based maintenance management may be operated independently, results of maintenance work based on one of the maintenance methods may be incorporated into the other maintenance method.

[0052] Further, Step P1 to Step P4 illustrated in FIG. 4 are not necessarily required to be executed through use of the maintenance management system 2. As long as the calculation of the risk and the comparison of the risk with the threshold value are performed through use of the computer at least in Step P3, the present invention does not exclude a case in which the other processing procedures of Step Pl, Step P2, and Step P4 are performed manually through use of a business form, for exanple.

Reference Signs List [0053] 1 plant 2 maintenance management system 21 information acquisition unit 22 storage unit 23 risk assessment unit 24 notification unit

Claims

Claims [Claim 1] A maintenance management method for a plant for processing fluid, the maintenance management method comprising the steps of: extracting accident scenarios assumed to occur in equipment included in the plant; acquiring, for each accident scenario that have been extracted, an occurrence frequency of an accident initiating event, which is likely to cause the each of the plurality of accidents, and a probability of failure on demand of a safety device for preventing occurrence of the each accident scenario; calculating, by a computer, a risk to compare the risk with a threshold value set in advance, the risk being a value obtained bymultiplyingthe occurrence frequency of the accident initiating event relating to the each accident scenario and the failure probability of the safety device relating to the each of the accident scenarios; and listing, for the accident scenarios, when the calculated risk is larger than the threshold value, equipment and a safety device that are relevant to the risk as maintenance work order priorities.[Claim 2] The maintenance management method for a plant according to claim 1, wherein, when multiple safety devices are provided in order to prevent occurrence of the accident, the risk is calculated by multiplying the occurrence frequency of the accident initiating event by the failure probabilities of the multiple safety devices in order.[Claim 3] The maintenance management method for a plant according to claim 1, wherein the occurrence frequency of the accident initiating event, which is acquired in the acquiring step, is obtained by incorporating a specific plant failure record of occurrence of the accident initiating event in the plant, and the failure probability of the safety device, which is acquired in the acquiring step, is obtained by incorporating a specific plant failure record of occurrence of a failure on demand of the safety device in the plant.[Claim 4] The maintenance management method for a plant according to claim 3, wherein the incorporation of the specific failure record of occurrence into the occurrence frequency of the accident initiating event or the failure probability of the safety device is performed based on Bayesian estimation.[Claim. 5] A maintenance management system for a plant for processing fluid, the maintenance management system comprising: an information acquisition unit configured to acquire, for each accident scenario assumed to occur in equipment included in the plant, risk-calculation information including an occurrence frequency of an accident initiating event, which is likely to cause the each accident scenario, and a probability of failure on demand of a safety device for preventing occurrence of the each accident scenario; a risk assessment unit configured to calculate, based on the risk-calculation information acquired by the information acquisition unit, a risk to compare the risk with a threshold value set in advance, the risk being a value obtained by multiplying the occurrence frequency of the accident initiating event relating to the each of the plurality of accidents and the failure probability of the safety device relating to the each of the accident scenarios; and a notification unit configured to list, for the accident scenarios, when the calculated risk is larger than the threshold value, the equipment and the safety device that are relevant to the risk as maintenance work order priorities.[Claim 6] The maintenance management system for a plant according to claim 5, wherein, when multiple safety devices are provided in order to prevent occurrence of the accident, the risk assessment unit calculates the risk by multiplying the occurrence frequency of the accident initiating event by the failure probabilities of the multiple safety devices in order.[Claim 7] The maintenance management system for a plant according to claim 5, wherein the information acquisition unit has a function of obtaining the occurrence frequency of the accident initiating event by incorporating a past record of occurrence of the accident initiating event in the plant, and obtaining the failure probability of the safety device by incorporating a specific failure record of occurrence of a failure on demand of the safety device in the plant.[Claim 8] The maintenance management system for a plant according to claim 7, wherein the information acquisition unit is configured to incorporate, based on Bayesian estimation, the past record of occurrence into the occurrence frequency of the accident initiating event or the failure probability of the safety device.