KR102626132B1 - System and Method for inspection to prevent demage of tube caused by high temperature - Google Patents

Abstract

An inspection system that can optimally design inspections to prevent high-temperature damage to boiler tubes is disclosed. The inspection system generates current inspection results using a sensor system that senses a tube and generates sensing information, a data collector that collects the sensing information, and the sensing information obtained by being connected to the data collector through a communication network. It is characterized in that it includes a computer that generates maintenance plan information by evaluating the tube condition according to the current inspection result.
Using the operation information of the tube, damage to the tube is evaluated, and the failure history and previous inspection results are used to determine whether to inspect and replace the tube before establishing an inspection (overhaul) plan, and to reflect this when establishing an overhaul plan so that the maintenance manager can make an appropriate decision. Replacement quantities can be secured and inspection plans can be easily established.

Description

Inspection system and method for preventing damage to tubes by high temperature {System and Method for inspection to prevent damage of tube caused by high temperature}

The present invention relates to tube inspection technology, and more specifically to a system and method for optimally designing inspection to prevent high temperature damage to boiler tubes.

Boiler tubes are the equipment that breaks down most frequently among boiler components, and due to the enormous number of thousands of tubes and the long length of 30 to 50 m per tube, many difficulties arise in inspection and diagnosis.

In addition, as boilers become larger in capacity and more efficient, problems such as economic losses due to breakdown damage and unstable power supply and demand are occurring. Various technologies and systems are being applied to prevent these problems, but they are not showing much effectiveness.

To elaborate, a technology was proposed that allows users to intuitively find the tube location and easily input/search inspection information through boiler tube 3D CAD modeling. However, in this case, it is impossible to provide the appropriate inspection time/position and replacement time/position of the tube, and there is a problem that continuous efforts are needed to manage diverse and extensive inspection information.

In addition, a technology was proposed that learns the correlation and normal operation patterns between boiler tubes and related sensors (output, excess air ratio, each tube outlet temperature sensor, steam pressure, etc.) and provides an alarm when abnormal patterns occur. In this case, the severity and fault information (location/type) of the alarm are not provided, making it difficult to establish preventive maintenance measures, and the problem is that continuous management efforts are required due to the need to relearn the model when the operation status changes after inspection (overhaul). there is.

In addition, in order for inspection to be performed during the overhaul period, the replacement part and inspection part/method must be determined at least 6 months before the overhaul, so that the supply and demand of replacement quantity and inspection contract can be concluded. However, all conventional technologies always inspect the same parts despite aging and environmental changes, and the replacement quantity is determined after the inspection, so the person in charge of boiler maintenance has no choice but to prepare insufficient or excessive quantity. It is hindering the stable operation and efficient execution of the maintenance budget.

In general, tube modules exposed to high-temperature damage such as boiler superheaters and reheaters vary depending on capacity, but approximately 1,000 tubes are installed per tube module, and about 15 to 30 tubes are gathered together to form a bank (or bank). It forms a unit called a panel, and about 20 to 80 banks are gathered together to form one superheater and reheater.

Typical high-temperature damage that occurs in superheaters and reheaters exposed to high temperatures include long-term creep, short-term creep, and high-temperature corrosion damage. These damages mainly occur at welds, bends, and thickness changes, but damage can be found in operating boilers. The only way to do this is to conduct non-destructive testing during shutdown.

Meanwhile, the non-destructive testing method for inspecting damage to boiler tubes and its pros and cons are as follows.

High-temperature damage to the tube grows into microcracks after the occurrence of creep pores (long-term/short-term creep damage), and when microcracks (in ㎛ units) are created, it is very likely to be damaged in a short period of time, so the tube is usually replaced when creep pores occur.

In the case of high-temperature corrosion, after the first micro-corrosion pit (in ㎛ units) occurs, it grows into a micro-crack, and when a micro-crack (in ㎛ units) is created, there is a very high possibility that it will be damaged in a short period of time. Usually, the tube is replaced when the corrosion pit grows more than mm or microcracks occur.

Therefore, penetration/ultrasonic/magnetic particle inspection can only be done right before the crack grows sufficiently and the tube is broken, so inspection is generally only possible when a boiler inspection (Overhaul) is performed every two years, so it is very limited in preventing tube rupture.

Among the above inspection methods, metal structure replication and hardness measurement can detect and manage the progress of defects in the tube from the initial stage of defect occurrence. However, since hardness measurement alone is difficult to determine the strength decrease during inspection, it is used in parallel with metal structure replication method. It is mainly used to complement tissue replication results.

The metal structure replication method can detect various defects and cracks, but it is very expensive and takes a long time to detect, so considering the limited overhaul period and budget, the most vulnerable part of the boiler tube must be inspected. The inspection is conducted by setting the accident site or an area that is easy to inspect due to site conditions, which is ineffective in preventing breakdowns.

In addition, in order for inspection to be performed during the overhaul period, the replacement part and inspection part/method must be determined at least 6 months before the overhaul, so that the supply and demand of replacement quantity and inspection contract can be concluded. However, all conventional technologies always inspect the same parts despite aging and environmental changes, and the replacement quantity is determined after the inspection, so the person in charge of boiler maintenance has no choice but to prepare insufficient or excessive quantity. It is hindering the stable operation and efficient execution of the maintenance budget.

1. Korean Patent Publication No. 10-2013-0088557

The present invention was proposed to solve the problems caused by the above background technology, and its purpose is to provide an inspection system and method that can optimally design inspections to prevent high temperature damage to boiler tubes.

In addition, the present invention uses the operation information of the tube to evaluate damage to the tube, uses the failure history and previous inspection results to determine whether to inspect and replace the tube before establishing an overhaul plan, and establishes an overhaul plan. By allowing maintenance managers to secure appropriate replacement quantities and easily establish inspection plans, There is another purpose in providing inspection systems and methods.

In addition, the present invention improves the accuracy of tube condition diagnosis, allowing effective tube preventive maintenance and optimal inspection and replacement costs. Another purpose is to provide inspection systems and methods.

In order to achieve the problems presented above, the present invention provides an inspection system that can optimally design inspection to prevent high temperature damage to boiler tubes.

The inspection system is,

A sensor system that generates sensing information by sensing boilers and tubes;

a data collector that collects the sensing information; and

A computer that generates current inspection results using the sensing information obtained by being connected to the data collector through a communication network and generates maintenance plan information by evaluating the tube condition according to the current inspection results.

Additionally, the sensing information may include operation information of the boiler and the tube.

Additionally, the computer may include an acquisition module that acquires the sensing information including the driving information; An analysis module that evaluates the degree of damage to the tube using the operation information; A calculation module that determines whether to inspect and replace the tube before establishing an overhaul plan using the current inspection result, failure history pre-stored in a database, and previous inspection result; and a notification information generation module that generates the maintenance plan information according to the decision as notification information.

In addition, the evaluation is one of the first stage indicating inspection omission, the second stage indicating inspection review, the third stage indicating inspection, the fourth stage indicating inspection and replacement review, and the fifth stage indicating replacement. It is characterized by

In addition, the evaluation of the degree of damage to the tube is made using creep damage, tissue replication inspection, and hardness measurement information, and is evaluated using the creep damage relationship equation obtained from the creep damage test and the operation information on the creep damage. It is characterized by

In addition, the operation information is characterized in that it is operation information from the previous planned preventive maintenance work to the design of the current planned preventive maintenance work.

In addition, the tissue replication test and hardness measurement information uses the results of the previous test, and in the current test, creep voids are detected, the tissue deterioration grade is E or F, and the hardness is reduced by more than 30% of the design strength conversion value. In this case, the tube is determined to be defective.

In addition, the creep damage equation is calculated using the temperature of the tube and the stress of the tube, and the calculation of the temperature of the tube is characterized by using the flow rate of the tube flowing through the tube.

In addition, the flow rate of the tube is calculated by calculating the flow rate distribution of each tube forming a boiler tube model consisting of an inlet header, an outlet header, and a plurality of tube banks, and the tube bank is characterized in that it is composed of a plurality of tubes. .

In addition, the stress of the tube is calculated using the allowable temperature calculation formula that is preset using the outlet design steam temperature of the entire tube module or the median and standard deviation of the outlet operating steam temperature calculated from the operation history of a preset period. It is characterized by allowable stress at temperature.

In addition, the inspection location of the tube is characterized in that it is any one of a bend portion, a weld portion, and a thickness change portion of the tube outlet selected using the creep damage relationship equation and the operation history.

In addition, when the thickness change area or the weld area is located in the middle part of the tube, it is selected as the inspection position.

In addition, parts that were replaced in the previous construction because the cause of the defect was determined to be creep are selected as the above-mentioned inspection location during the first planned preventive maintenance work after replacement, and if the inspection results and creep damage evaluation results are good, they will be excluded from inspection for a certain period of time. It is characterized by

On the other hand, another embodiment of the present invention includes the steps of (a) a sensor system sensing a tube to generate sensing information; (b) collecting the sensing information by a data collector; And (c) generating a current inspection result using the sensing information obtained by a computer connected to the data collector through a communication network, and generating maintenance plan information by evaluating the tube condition according to the current inspection result. Provides an inspection method for preventing high temperature damage to tubes, characterized in that:

On the other hand, another embodiment of the present invention includes the steps of: (a) a computer calculating the flow rate distribution for each tube using a database with real-time tube operation status information; (b) the computer calculating temperature stress for each tube using the flow rate distribution for each tube; (c) the computer calculating an instantaneous damage value for each tube using the temperature stress for each tube; (d) The computer calculates a plurality of instantaneous damages through the stress-temperature-life relationship equation obtained from the instantaneous average operating value of the tube and creep fracture test data for the tube material, and accumulates the plurality of instantaneous damage values for each tube. Calculating a cumulative damage value; and (e) the computer selecting a specific condition evaluation index and a tube to be replaced using the inspection results and maintenance history of the previous maintenance using the cumulative damage value for each tube over a certain period of time. Provides an inspection method to prevent high-temperature damage to the featured tube.

According to the present invention, damage to the tube is evaluated using the operation information of the tube, and the failure history and previous inspection results are used to determine whether to inspect and replace the tube before establishing an inspection (overhaul) plan, and to reflect this when establishing an overhaul plan. By doing so, the maintenance manager can secure an appropriate replacement quantity and easily establish an inspection plan.

In addition, another effect of the present invention is that it improves the accuracy of tube condition diagnosis, effectively performs preventive maintenance of the tube, and executes optimal inspection and replacement costs.

In addition, another effect of the present invention is that remote monitoring/diagnosis business is possible with only on-site sensors and driving data.

1 is a block diagram of the configuration of an inspection system according to an embodiment of the present invention.
FIG. 2 is a detailed block diagram of the computer shown in FIG. 1.
FIG. 3 is a detailed block diagram of the controller shown in FIG. 2.
Figure 4 is a flow chart showing a tube high temperature damage prevention maintenance process according to an embodiment of the present invention.
Figure 5 is a creep damage relationship table according to an embodiment of the present invention.
Figure 6 is an example of a model that calculates the flow rate distribution of each tube bank according to operating conditions according to an embodiment of the present invention.
Figure 7 is a graph showing the results of comparing the errors between experiment and calculation for mass flow rate according to an embodiment of the present invention.
Figure 8 is a graph showing the results of comparing errors between experiments and calculations for static pressure according to an embodiment of the present invention.
Figure 9 is a graph of typical tube operating temperature fluctuation characteristics.
Figure 10 is a conceptual diagram of inspection using a temperature sensor according to an embodiment of the present invention.
Figure 11 is an example of a screen captured by enlarging the cross section of a typical target tube.
Figure 12 is a flow chart showing a tube high temperature damage prevention maintenance process according to another embodiment of the present invention.

The advantages and features of the present invention and methods for achieving them will become clear by referring to the embodiments described in detail below along with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and will be implemented in various different forms. These embodiments only serve to ensure that the disclosure of the present invention is complete, and those skilled in the art It is provided to fully inform the person of the scope of the invention, and the present invention is only defined by the scope of the claims. The sizes and relative sizes of components shown in the drawings may be exaggerated for clarity of explanation.

Like reference numerals refer to like elements throughout the specification, and “and/or” includes each and all combinations of one or more of the referenced items.

The terms used in this specification are for describing embodiments and are not intended to limit the invention. As used herein, singular forms also include plural forms, unless specifically stated otherwise in the context. As used in the specification, “comprises” and/or “consisting of” stated components, steps, operations and/or elements do not exclude the presence or addition of one or more other components, steps, operations and/or elements. .

Although it is used to describe various components such as first and second, it goes without saying that these components are not limited to these terms. These terms are used to distinguish between only one component. Therefore, it goes without saying that the first component mentioned below may also be the second component within the technical spirit of the present invention.

Unless otherwise defined, all terms (including technical and scientific terms) used in this specification may be used with meanings that can be commonly understood by those skilled in the art to which the present invention pertains. Additionally, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless clearly specifically defined.

Hereinafter, an inspection system and method for preventing high temperature damage to a tube according to an embodiment of the present invention will be described in detail with reference to the attached drawings.

Figure 1 is a block diagram of the inspection system 100 according to an embodiment of the present invention. Referring to FIG. 1, the inspection system 100 includes a sensor system 110 that generates sensing information by sensing a boiler and/or tube, a data collector 120 that collects sensing information, a communication network 130, and a communication network 130. It may be configured to include a computer 140 that generates inspection results using sensing information collected through ) and generates maintenance plan information by evaluating the tube condition according to the inspection results.

The sensor system 110 may include a first measuring device 111, a second measuring device 112, a differential pressure gauge 113, a sensor 114, etc. The first meter 111 is an inlet header flow meter, the second meter 112 is a tube flow meter, and the differential pressure gauge 113 can be a header and tube bank differential pressure meter. The sensor 114 is a sensor installed in the boiler and/or tube and may be a temperature sensor or the like.

In general, tube modules exposed to high-temperature damage such as boiler superheaters and reheaters vary depending on capacity, but approximately 1,000 tubes are installed per tube module, and about 15 to 30 tubes are gathered together to form a bank (or bank). It forms a unit called a panel, and about 20 to 80 banks are gathered together to form one superheater and reheater.

Typical high-temperature damage that occurs in superheaters and reheaters exposed to high temperatures include long-term creep, short-term creep, and high-temperature corrosion damage. These damages mainly occur at welds, bends, and thickness changes, but damage can be found in operating boilers. The only way to do this is to conduct non-destructive testing during shutdown.

Therefore, in one embodiment of the present invention, damage to the tube is evaluated using the operation information of the tube, and the failure history and previous inspection results are used to determine whether to inspect and replace the tube before establishing an overhaul plan, and this is reflected when establishing an overhaul plan. By doing so, the boiler maintenance manager can secure an appropriate replacement quantity, easily establish an inspection plan, improve the accuracy of tube condition diagnosis, effectively perform preventive maintenance of tubes, and execute optimal inspection and replacement costs.

Continuing to refer to FIG. 1 , the data collector 120 performs the function of collecting sensing information generated from the sensor system 110 and transmitting it to the computer 140 through the communication network 130. The data collector 120 may be a data acquisition device. The data collector 120 may be configured to include a communication module for connection to the communication network 130. Additionally, the data collector 120 may be connected to the operation controller 101 that controls the boiler (not shown) to obtain operation information of the boiler and/or tube. The operation controller 101 may be configured to include a microprocessor, microcomputer, switching circuit element, etc.

The communication network 130 refers to a connection structure that allows information exchange between nodes such as a plurality of terminals and servers, such as public switched telephone network (PSTN), public switched data network (PSDN), and integrated information and communication network (ISDN). It can be Integrated Services Digital Networks (BISDN: Broadband ISDN), Local Area Network (LAN), Metropolitan Area Network (MAN), Wide LAN (WLAN), etc. However, the present invention is not limited to this, and is applicable to wireless communication networks such as CDMA (Code Division Multiple Access), WCDMA (Wideband Code Division Multiple Access), Wibro (Wireless Broadband), WiFi (Wireless Fidelity), and HSDPA (High Speed Downlink). Packet Access) network, Bluetooth, NFC (Near Field Communication) network, satellite broadcasting network, analog broadcasting network, DMB (Digital Multimedia Broadcasting) network, etc. Alternatively, it may be a combination of these wired communication networks and wireless communication networks.

The computer 140 performs the function of generating inspection results using sensing information and generating maintenance plan information by evaluating the tube condition according to the inspection results. To elaborate, the computer 140 uses the operation information of the tube to evaluate damage to the tube, and uses the failure history and previous inspection results to determine whether to inspect and replace the tube before establishing an inspection (overhaul) plan and inspect it ( Overhaul) By reflecting this when establishing a plan, the boiler maintenance manager can secure an appropriate replacement quantity and easily establish an inspection plan. By improving the accuracy of tube condition diagnosis, effectively performing preventive maintenance of tubes and executing optimal inspection and replacement costs. make it possible

The computer 140 may be a personal computer (PC) or a server. A database 141 may be built in the computer 140. The database 141 may also store sensing information, identification information for boilers, tubes, etc.

FIG. 2 is a detailed block diagram of the computer 140 shown in FIG. 1. Referring to FIG. 2, the computer 140 is connected to the controller 210, which generates inspection results using sensing information and generates maintenance plan information by evaluating the tube condition according to the inspection results, and the communication network 130 to perform sensing. A communication unit 220 that acquires information, a storage unit 230 that stores sensing information obtained through the communication unit 220, a power unit 240 that supplies power to components, and an input unit 250 that inputs user commands. ), and an output unit 260 that outputs maintenance plan information.

The controller 210 performs a function of generating inspection results using sensing information and generating maintenance plan information by evaluating the tube condition according to the inspection results. For this purpose, signals are exchanged with components and control is performed.

The communication unit 220 performs a communication connection with the communication network 130 and performs a function of connecting communication between the data collector 120 and the computer 140. For this purpose, the communication unit 220 may be configured to include a wired or wireless modem, a LAN card, a microprocessor, etc.

The storage unit 230 performs the function of storing the database 141. In addition, the storage unit 230 stores programs, software, data, etc. having an algorithm that generates inspection results using sensing information, evaluates the tube condition according to the inspection results, and generates maintenance plan information.

For this purpose, the storage unit 230 is a flash memory type, a hard disk type, a multimedia card micro type, and a card type memory (for example, SD (Secure Digital) or eXtreme Digital (XD) memory, etc.), Random Access Memory (RAM), Static Random Access Memory (SRAM), Read Only Memory (ROM), Electrically Erasable Programmable Read Only Memory (EEPROM), Programmable Read It may include at least one type of storage medium among (Only Memory), magnetic memory, magnetic disk, and optical disk. Additionally, it may operate in connection with web storage and cloud servers that perform storage functions on the Internet.

The power unit 240 performs the function of supplying power to components. To this end, it may be configured to include a power supply, regulator, AC (Alternating Current)-DC (Direct Current) converter, etc.

The input unit 250 performs the function of inputting a user's command. Therefore, it may be configured to include a mouse, keyboard, microphone, etc.

The output unit 260 performs the function of outputting a settings screen, a processing information screen, etc. For this purpose, the output unit 260 includes a liquid crystal display (LCD), a light emitting diode (LED) display, a plasma display panel (PDP), an organic LED (OLED) display, a touch screen, a cathode ray tube (CRT), and a flexible display. , micro LED, mini LED, etc. In the case of a touch screen, it can be used as an input means. Additionally, the output unit 260 may be configured to include a sound system.

FIG. 3 is a detailed block diagram of the controller 210 shown in FIG. 2. Referring to FIG. 3, the controller 210 includes an acquisition module 310 that acquires sensing information including operation information of the tube, an analysis module 320 that evaluates the degree of damage to the tube using the operation information, and a failure history. and a calculation module (330) that determines whether to inspect and replace the tube before establishing an inspection (overhaul) plan using the previous inspection results, and a notification information generation module (340) that generates maintenance plan information according to the decision as notification information. It can be configured to include.

The analysis module 320 performs a function of evaluating damage to the tube using the tube's operation information.

The calculation module 330 uses the failure history and previous inspection results previously stored in the database to determine whether to inspect and replace the tube before establishing an overhaul plan, and has a function to reflect this when establishing an overhaul plan. Perform.

The notification information generation module 340 performs the function of generating notification information so that the boiler maintenance manager can secure an appropriate replacement quantity and easily establish an inspection plan. Therefore, by improving the accuracy of tube condition diagnosis, it is possible to effectively perform preventive maintenance of tubes and execute optimal inspection and replacement costs.

“Acquisition module,” “analysis module,” “calculation module,” notification information generation module, etc. shown in FIG. 3 refer to a unit that processes at least one function or operation, which may be implemented in software and/or hardware. In hardware implementation, an application specific integrated circuit (ASIC), digital signal processing (DSP), programmable logic device (PLD), field programmable gate array (FPGA), processor, and microcontroller designed to perform the above-mentioned functions. It may be implemented as a processor, other electronic units, or a combination thereof.In software implementation, software configuration components (elements), object-oriented software configuration components, class configuration components, and task configuration components, processes, functions, properties, procedures, and sub-components. It can include routines, segments of program code, drivers, firmware, microcode, data, databases, data structures, tables, arrays, and variables.Software, data, etc. can be stored in memory and executed by a processor. The memory or processor may employ various means well known to those skilled in the art.

Figure 4 is a flow chart showing a tube high temperature damage prevention maintenance process according to an embodiment of the present invention. Referring to FIG. 4, the process progresses cyclically from the tube condition evaluation and replacement quantity prediction stage (S410) to the operation state analysis stage (S481), making it different from the linear and one-time conventional system.

In the tube condition evaluation and replacement quantity prediction stage (S410), defect cause analysis information according to past tube defect cause analysis (S460), inspection results and maintenance history information according to inspection results and maintenance history (S471), and planned preventive maintenance work. Afterwards, the operation status analysis information according to the operation status analysis (S481) using the operation history up to the present is synthesized to evaluate the condition of the tube in stages 1 to 5 (i.e. stages), of which stage 5 is the most serious. Replacement of the tube is recommended, and replacement of the 4th stage is recommended if it reaches stage 5 before the next planned preventive maintenance period (after 4 years) arrives. The 5 stages are as follows.

stage One 2 3 4 5 Even matters Skip inspection Inspection review test inspection and
Consider replacement substitute

In the table above, Stage 1 inspection can be omitted during the current planned preventive maintenance construction, and Stage 2 inspection can be performed or postponed to the next inspection depending on the construction period and budget size. Stages 3 and 4 must be inspected during this planned preventive maintenance project. In the case of stage 4, replacement may be necessary depending on the inspection results, so prepare replacement quantities or perform simple maintenance between planned preventive maintenance projects every two years. If construction is scheduled, replacement can be delayed by one year. In the case of stage 5, replacement quantity must be secured, and inspection can be performed if data collection is necessary. Tube condition evaluation uses the information generated by steps S460, S461, S470, S471, S480, and S481. Accurate results can only be obtained by integration, but if steps S461 and S471 have not been performed in the past, the information generated by step S481 must be secured to perform the evaluation. Usually, when a new boiler tube high-temperature damage preventive maintenance technique is applied or a system is installed, information according to steps S461 and S471 cannot be obtained. However, since information according to step S481 is obtained by sensors installed in most boilers, tube condition evaluation is not possible. Cases are difficult to find.

Tube condition evaluation is determined by the following evaluation procedure. The degree of creep damage can be evaluated using the creep damage relationship equation obtained from the creep failure test of materials such as Larson-Miller Parameter and operation information from the previous planned preventive maintenance work to the design of the current planned preventive maintenance work. Tissue replication tests and hardness measurements generally use the previous test results (S400), and if a creep void is detected in the current test, the tissue deterioration grade is E or F, and the hardness decreases by more than 30% of the design strength conversion value, it is judged to be a defect. Therefore (SS460), replacement is recommended.

Steps S461, S471, and S481 provide the information necessary to perform step S410. Step S461 reflects past defect locations when selecting an inspection location, and step S471 provides inspection results and tube maintenance history for evaluating the condition of the tube. It provides information necessary for calculating tube temperature, such as usage time and past oxidation scale thickness, and step S481 provides key operation information for evaluating creep damage of the tube, including data from the temperature sensor installed in the unheated part of the boiler tube outlet, steam flow rate, It may include operating information such as pressure.

In addition, step S420 is a step that reflects the results of step S410 on the site, providing information such as inspection location, location, method, and scaffolding/scaffolding installation location for inspection in the planned preventive maintenance work design, and inspecting tubes with a very high possibility of damage. This is the stage to select, calculate the replacement quantity, and place an order before construction to ensure that there are no disruptions in construction performance.

Meanwhile, the procedures from steps S410 to S471 are generally carried out step by step independently, but all or part of the steps can be processed by a computer system, and additional work is required to automatically link the steps. In particular, the data processed in step S471 is time series data, which is a value that is continuously recorded over time, so a special database is required to manage it, and if a general relational database is used, utilization may be difficult.

The real-time database is a special database for time series data management, and there are commercialized products that support various interfaces to support complex calculations at the S410 level. However, in the case of open source real-time databases, interface support is very limited, making it difficult for users to develop them, so they are rarely used.

Figure 5 is a creep damage relationship table according to an embodiment of the present invention. Referring to Figure 5, the creep damage degree is calculated by steps S410 and S481, the tissue replication test is calculated by steps S461 and S471, and the hardness measurement information is calculated by steps S461 and S471. * shown in Figure 5 indicates that an additional test is performed or an excerpt is taken as a special test result and a creep destruction test is performed, and ** indicates that an additional test is performed or an excerpt is performed and a creep destruction test is performed because short-term overheating is suspected.

Figure 6 is an example of a model that calculates the flow rate distribution of each tube bank according to operating conditions according to an embodiment of the present invention. In general, among the condition evaluation factors of boiler tubes, creep damage evaluation results are determined by the accuracy of input data and the appropriateness of evaluation techniques, but the input data and evaluation techniques presented in the past do not match the operating characteristics of the actual boiler or are arbitrarily selected. There are difficulties in trusting, and the improvement methods to solve this are as follows.

The tube condition evaluation method follows the traditional creep damage evaluation technique, but the steps for calculating the tube temperature and the tube stress are significantly different from the conventional method. The conventional method of calculating the temperature of a tube is to calculate the temperature of the tube by assuming that the flow rate flowing through each tube is the same and that the value is an average value. The flow rate of each tube is determined depending on the connection type of the header. In general, the process of calculating the tube flow rate is very important because there is a difference of 10 to 20% between the maximum and minimum flow rates of the tube.

The theoretical method for calculating the flow rate of a complex piping network such as boiler tubes can be a flow network analysis method or similar commercial software. The process for calculating the flow rate of these tubes is as follows.

①. Using the pressure loss coefficient equation or diagram for the components of one tube flow path, calculate the pressure loss coefficient formula or diagram for the entire flow path for operating conditions such as possible temperature, pressure, and flow rate range. The general form of the pressure loss coefficient within the pipe is as follows:

Here, f: friction coefficient, L: pipe length, D: pipe diameter. The friction coefficient is as follows.

That is, Filonenko's equation for turbulent flow.

Here, Re: Reynolds number of pipe flow. Re is as follows:

Here, μ: viscosity coefficient of the fluid, ρ: density of the fluid, v: velocity of the fluid, D: pipe diameter.

②. Using commercial software that performs flow network analysis or similar functions, the pressure loss coefficient equation or diagram for each flow path calculated in procedure ① for a tube bank (or panel, bundle) composed of multiple tubes and possible operating conditions are analyzed. Calculate the pressure loss coefficient equation or diagram and the flow rate distribution of each tube passage.

③. Using commercial software that performs flow network analysis or similar functions, the pressure loss coefficient equation or diagram of the tube bank obtained in procedure ② for the boiler tube model consisting of the inlet and outlet headers and multiple tube banks and the possible operating conditions are calculated. Calculate the flow distribution of each tube bank.

④. Calculate the flow rate distribution of each tube that makes up the boiler tube model using the flow rate distribution for each tube bank in step 3 and the flow rate distribution of each tube in the bank in procedure ②.

Figure 6 presents an example of the above procedures ① to ③. In procedures ① and ②, the pressure loss coefficient of a single tube passage and a tube bank was calculated using Flowmaster, a commercial flow path design software, and in procedure ③, the flow network analysis method was used. It was calculated using . It consists of a tube flow path pressure loss calculation step (S610), a tube bank pressure loss calculation step (S620), and a tube module flow distribution calculation step (S630).

Figure 7 is a graph showing the results of comparing the errors between experiment and calculation for mass flow rate according to an embodiment of the present invention. Referring to FIG. 7, the mass flow rate 710 at the divide header outlet and the mass flow rate 720 at the combine header outlet are crowded at the boundary between experiment and calculation. In other words, it shows good flow rate results as a result of comparing the errors of experiment and calculation.

Figure 8 is a graph showing the results of comparing errors between experiments and calculations for static pressure according to an embodiment of the present invention. Referring to Figure 8, the static pressure 810 at the distribution header outlet and the static pressure 820 at the combined header outlet are crowded at the boundary between experiment and calculation. In other words, it shows good static pressure results as a result of comparing the errors of experiment and calculation.

Figure 9 is a graph of the operating temperature fluctuation characteristics of a general tube. Referring to FIG. 9, the conventional method of calculating the stress acting on the tube to evaluate creep damage of the tube is generally a method of calculating the hoop stress using the pressure of steam flowing inside the tube and an allowable stress using the operating temperature. A method for calculating is presented. The former method is presented in industry standard codes such as ASME (American Society of Mechanical Engineers) and KEPIC (Korea Electric Power Industry Code, KEPIC), but it has the disadvantage of losing the ability to differentiate between tubes because the calculated damage value is too small. As shown in FIG. 9, the method has the disadvantage that it is difficult to apply in practice because the variation in the operating temperature of the tube (outlet tube metal temp) is too large. In addition, even if you compare these two values and select a larger value, there is a difficulty in not matching the actual driving phenomenon because the stress for evaluating damage is not consistent.

To solve the above problems, the stress of the tube is calculated through the following procedure based on the allowable temperature calculation method presented by TRD 300, the international pressure vessel code, and IBR (Indian Boiler Regulation).

①. Calculate the median and standard deviation of the outlet operating steam temperature from the outlet design steam temperature of the entire tube module or more than one year of operation history (taking into account the boiler's operation characteristics according to seasonal changes).

②. When the outlet design steam temperature is obtained, calculate the allowable temperature of the tube using the allowable temperature calculation formula of TRD300, or when the median and standard deviation of the outlet operating steam temperature are calculated, use a calculation formula that changes the allowable temperature calculation formula of IBR, and use the calculation formula that changes the allowable temperature calculation formula of IBR. To ensure discrimination and stability of maintenance decisions, the lower of the two allowable temperatures is determined as the allowable temperature.

The outlet design steam temperature and outlet operating steam temperature conditions are as follows.

The original formula for IBR was and and T _mx is the expected maximum steam temperature.

In the above equation, T _d is the outlet design steam temperature, T _m is the median outlet operation steam temperature, T _sd is the outlet operation steam temperature standard deviation, and n is a value determined depending on the boiler type and the position of the tube module, among 1, 1.5, and 2. Select one value. The default value is 1.5, and for radiant superheaters, a larger value is applied the closer it is to the boiler furnace outlet, and for convection superheaters, a larger value is applied the farther away it is.

In general, the boiler's outlet design steam temperature is given only to the final superheater and final reheater, but not to the primary and secondary superheaters and reheaters, so the outlet operation steam temperature condition must be applied.

③. Determine the allowable stress as the stress acting on the tube at the allowable temperature of the tube calculated in procedure ②. This determination method is conceptually consistent with the method by which boiler manufacturers determine the lifespan of tubes, and even if the outlet design steam temperature cannot be secured, it can be reasonably evaluated through international codes related to pressure vessels, operation history, and statistical methods to determine the lifespan of tubes. Damage assessment is possible.

Meanwhile, the conventional tube inspection location selection method was uniformly determined based on past accident cases and boiler tube maintenance guidelines, so that only the same location was inspected without considering the boiler's operation history and characteristics. However, there are many cases where the actual accident location of the boiler tube does not coincide with the uniformly determined location, so although the problems with the conventional method are recognized, no improved method has been proposed.

One embodiment of the present invention presents an improved tube inspection position selection concept. The new tube inspection location selection method is selected according to the following procedure, considering the improved tube creep damage technique and the weak points presented in the boiler tube maintenance guidelines.

①. Using the improved tube creep damage technique and operation history, the degree of damage to the tube on which the sensor is installed is evaluated, and if the tube condition is evaluated to be 3 stages or higher, it is selected as an inspection target.

*②. Among tubes without sensors installed, if the condition of a nearby tube is evaluated as 3 stages or higher, a tube with a sensor installed in the same bank is evaluated as 3 stages or higher, or a tube with a sensor installed in the same row of a neighboring bank If it is one of the two cases evaluated as stage 3 or higher, both are included in the inspection target.

③. In procedure ②, if there are tubes without sensors installed in the same bank as tubes with 3 or more condition evaluation stages, the tube with the lowest flow rate among the target tubes is sensitive to changes in combustion gas temperature, and is thus most likely to be exposed to high temperatures. is selected as the inspection target.

④. The bend area, weld area, and thickness change area of the tube outlet selected in procedures ① ~ procedure ③ are selected as inspection targets. The bend area includes the outer surface (extrados), and the weld area includes the nearby heat-affected zone and base metal area. Select the inspection location. If there is only a straight pipe area at the tube outlet, the area with the highest temperature is selected as the inspection area and the high temperature area is determined. The method for determining the high temperature area is as follows.

Figure 10 is a conceptual diagram of inspection using a temperature sensor according to an embodiment of the present invention. Referring to FIG. 10, the upper enclosure (1031) is spaced at intervals of 10 cm centered on the 3/4 run area of the longest tube outlet on the steam inlet header (1011) and steam outlet header (1012) where the temperature sensors (1021, 1022) are installed. ) and the lower enclosure (1032), the oxidation scale is measured at more than 10 locations according to the combustion gas flow (1001), and the area with the thickest oxidation scale thickness is selected as the location for inspection (tissue replication and hardness measurement), and the temperature sensor Select the same location as the inspection location for the target tube that is not installed.

⑤. If there is a thickness change area or welding area in the middle of the tube selected in procedures ① to procedure ③, select it as the inspection location.

⑥. Parts that were replaced because the cause of the defect was determined to be creep in the previous construction are selected as inspection locations during the first planned preventive maintenance work after replacement, and if the inspection results and creep damage evaluation results are good, they are excluded from inspection for up to 4 years.

Meanwhile, the inspection is performed according to the steps from Procedure 1 to Procedure 4, and if a defect is found as a result of the inspection, an additional inspection location is selected in the same manner as Procedure 3, focusing on the defective part.

Figure 11 is an example of a screen captured by enlarging the cross section of a typical target tube. Referring to Figure 11, the condition evaluation index of the tube can detect not only damage due to creep but also damage due to high-temperature corrosion, so preventive maintenance is possible using the same method. High-temperature corrosion of tubes has different activation temperatures for each steel type, but in common, the extent of corrosion damage and the probability of defects increase in proportion to the temperature of the tube. However, in order to check corrosion damage, the target tube must be extracted and the cross-section enlarged to be observed. In Figure 11, a cross section 1110 of the sound part and a cross section 1120 of the damaged part are shown. The cross-section 1110 of the healthy part has a smooth pre-treatment surface, and the cross-section 1120 of the damaged part has a hole (pit) on the pre-treatment surface.

In order to evaluate high-temperature corrosion, creep damage indicators and observation information of the sampled tube cross-section are required, while tube surface tissue replication and hardness measurements are unnecessary. However, high-temperature corrosion and creep have a strong tendency to occur at the same time, and they interact to reduce the time to failure. Therefore, if the tube condition evaluation index corresponds to stage 4, some tubes are extracted, a surface inspection is performed, and holes ( If defects such as pits or grooves are discovered, replacement of the tube may be recommended during the session's planned preventive maintenance work or at least the next preventive maintenance work.

Therefore, even when preventing damage due to high-temperature corrosion, there is no need to change the original indicator, and additional tube sampling tests can be performed to determine whether or not to maintain. According to the results of the tube sampling test, if there is corrosion damage, immediate replacement should be recommended. However, since the sampling test period takes several days or more, if the replacement period is not secured, replacement should be recommended during the next simple maintenance or the next scheduled preventive maintenance work. .

In order to reduce inspection costs, in the case of thermal power plants in the Middle East or Southeast Asia where tissue replication testing is not smooth due to the low level of domestic IPP (Industry Professional Practice) or inspection technology, only hardness is measured or neither tissue replication testing nor hardness is performed. Instead, PT (Liquid Penetration) is used. Test)/MT(Magnetic Particle Testing)/UT(Ultrasonic Testing) are sometimes performed. In this case, since the condition evaluation of the tube is determined by the degree of creep damage, there is a difference in the inspection range and inspection location in that it depends only on the degree of creep damage. However, the overall preventive maintenance method follows existing methods and procedures and is different from the existing method. As follows.

Figure 12 is a flow chart showing a tube high temperature damage prevention maintenance process according to another embodiment of the present invention. Referring to FIG. 12, steps S1210 and S1220 are steps for calculating the flow distribution for each tube using the method described above, and S1230 calculates tube stress by a new stress calculation method based on the concepts of TRD 300 and IBR code and uses an energy settlement method. Calculate the temperature using .

In step S1240, damage is calculated through the stress-temperature-life relationship equation obtained from the instantaneous (1 hour to 2 hours) average operating value and creep fracture test data for the tube material. In step S1250, the instantaneous damage values of the tubes are stored by operation time, and the instantaneous damage values of each tube are added to obtain a cumulative damage value, which is also stored by operation time.

In step S1260, the accumulated damage (creep damage) for each tube is checked 6 months before maintenance, and then the latest condition evaluation index and replacement target tube are selected using the inspection results and maintenance history information from the previous maintenance. In step S1270, the tube inspection location is selected using past defect location and cause analysis information and the tube condition evaluation index in step S1260. The results of steps S1260 and S1270 are combined to establish a non-destructive inspection and maintenance plan for step S1280.

Meanwhile, it is possible to develop a system that can monitor tube damage in real time in steps from S1220 to S1250. In addition, it shows the linkage and detailed function performance procedures for each step when building a system at the S1201, S1202, S1210, and S1280 steps. When managed using a DB with real-time operation information at the S1220 step, it can be managed using Java, C, C#, VB, etc. The developed program and data can be linked.

Additionally, the steps of the method or algorithm described in relation to the embodiments disclosed herein are implemented in the form of program instructions that can be executed through various computer means such as a microprocessor, processor, CPU (Central Processing Unit), etc., and are computer readable. Can be recorded on any available medium. The computer-readable medium may include program (instruction) codes, data files, data structures, etc., singly or in combination.

The program (instruction) code recorded on the medium may be specially designed and constructed for the present invention, or may be known and usable by those skilled in the art of computer software. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tapes, optical media such as CD-ROM, DVD, and Blu-ray, and ROM and RAM. Semiconductor memory elements specially configured to store and execute program (instruction) code, such as RAM, flash memory, etc., may be included.

Here, examples of program (instruction) code include not only machine language code such as that created by a compiler, but also high-level language code that can be executed by a computer using an interpreter or the like. The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the present invention, and vice versa.

*100: Inspection system
110: sensor system 120: data collector
130: communication network 140: computer
310: Acquisition module 320: Analysis module
330: calculation module 340: information notification generation module
1011: Steam inlet header 1012: Steam outlet header
1021,1022: Temperature sensor
1031: Top enclosure
1032: Bottom enclosure

Claims (1)

(a) the sensor system 110 sensing the boiler and tube to generate sensing information;
(b) collecting the sensing information by the data collector 120; and
(c) The computer 140 connected to the data collector 120 through the communication network 130 generates the current inspection result using the acquired sensing information and evaluates the tube condition according to the current inspection result to plan maintenance. It includes: generating information;
The sensing information includes operation information of the boiler and the tube,
In step (c),
Acquiring the sensing information by the acquisition module 310;
The analysis module 320 evaluating the degree of damage to the tube using the operation information; and
A step where the calculation module 330 determines before establishing an overhaul plan whether to inspect or replace the tube using the current inspection result, the failure history previously stored in the database 141, and the previous inspection result. do,
Evaluation of the degree of damage to the tube is performed using tissue replication tests and hardness measurement information,
The tissue replication test and hardness measurement information uses the previous test results, and if creep voids are detected in the current test or the tissue deterioration grade is E or F and the hardness decreases by more than 30% of the design strength conversion value. The tube is judged to be defective,
The evaluation of the degree of damage to the tube is any of the following: a first stage indicating inspection omission, a second stage indicating inspection review, a third stage indicating inspection, a fourth stage indicating inspection and replacement review, and a fifth stage indicating replacement. An inspection method for preventing high temperature damage to tubes, characterized by evaluating them as one.