Online ice plug isolation implementation method and device for condensed water recirculation pipe

Abstract

The invention belongs to the technical field of nuclear power on-line maintenance, and particularly relates to an on-line ice plug isolation implementation method and device for a condensation water recirculation pipe. The condensate water level of a condenser heat trap is improved by temporarily adjusting operation process parameters, so that a horizontal pipeline, entering a condenser shell, of a condensate water recirculation pipe is filled with water, and the condensate water recirculation pipe online ice plug isolation device is installed on the horizontal pipeline, entering the condenser shell, of the condensate water recirculation pipe. The section of pipeline is a water return main pipe shared by a plurality of condensed water recycling pipes, and the height difference between the highest point of the siphon section of the water return main pipe of the condensed water recycling pipes and the horizontal pipeline entering the condenser shell is larger than 5 meters. The method has the advantages that the water level of the heat trap of the condenser is temporarily increased by a steam turbine operation operator, so that the water level of the condenser submerges the horizontal pipeline of the water return main pipe of the condensed water recirculation pipe, the horizontal pipeline of the water return main pipe of the condensed water recirculation pipe reaches a full water state in the operation period, and a basic condition is created for ice plug operation.

Description

Technical Field

[0001] This invention belongs to the field of nuclear power online maintenance technology, specifically relating to a method and apparatus for implementing online ice blockage isolation of condensate recirculation pipes. Background Technology

[0002] Nuclear power plant pipeline ice plug technology is an important isolation method for online maintenance. It involves continuously injecting refrigerant into the ice plug jacket to freeze the water inside the pipeline, forming an ice plug capable of withstanding a certain pressure differential, thereby achieving equipment isolation. Ice plugs can establish a reliable temporary isolation boundary for pipelines, valves, and other equipment without isolation devices, without shutting down the unit or emptying the system. It is commonly used in maintenance activities where drainage is difficult or prohibitively costly.

[0003] An ice plug jacket typically consists of two symmetrical metal semi-cylinders. Its inner and outer diameters and length can be customized based on the pressure differential the ice plug must withstand and the specifications of the pipe. Liquid nitrogen is the most commonly used refrigerant. The ice plug jacket is tightly fitted to the outer wall of the pipe at the area requiring freezing. After the refrigerant enters the jacket from one end, it absorbs a large amount of heat from the pipe as it changes from a liquid to a gaseous state. This rapidly cools the liquid medium within the pipe enclosed by the ice plug jacket, causing it to solidify. With the continuous input of liquid nitrogen, the liquid medium within the pipe eventually solidifies completely, forming an ice plug that fits tightly against the inner wall of the pipe, thus isolating the pipe, valves, and other equipment. The vaporized liquid nitrogen is discharged through the vent at the other end of the ice plug jacket.

[0004] Due to the unique location of the condensate recirculation pipe, the medium within it exhibits the following characteristics: First, during normal operation, the condensate recirculation valve is closed. Due to the communicating vessel principle and siphon effect, the condensate in the pipe downstream of the recirculation valve flows back to the condenser under pressure differential until the liquid level in the recirculation pipe equals that in the condenser. Therefore, the pipe downstream of the recirculation valve is in a "no water" or "not fully watered" state during normal operation, and the water level in the vertical pipe changes with the liquid level in the condenser. Second, during normal operation, the condenser simultaneously receives exhaust steam from the low-pressure cylinder and condensate from each stage of the regenerative extraction system, while simultaneously transporting condensate from the condenser heat trap to the condensate pump. These two processes coordinate to maintain a dynamic balance, keeping the condenser water level relatively stable. Therefore, the condensate in the recirculation pipe connected to the condenser is continuously in a "flowing" state, undergoing medium replacement and heat exchange, and its temperature remains above 30°C. Due to the aforementioned characteristics, ice plugging of condensate recirculation pipes can only be implemented on pipe sections with water near the condenser. Furthermore, since the condensate in the recirculation pipe is constantly in a "flowing" state, conventional ice plugging methods are unlikely to form an effective ice plug. Therefore, when condensate recirculation valve failures or pipeline defects occur, maintenance can only be carried out after the turbine is shut down. The costs of maintenance isolation and unit startup are very high. Therefore, it is necessary to develop a reliable online ice plug isolation implementation method and supporting equipment to achieve the goal of online maintenance of condensate recirculation valve failures or pipeline defects without shutting down the turbine.

[0005] Typically, ice plug isolation is located on water-filled pipes and uses a single ice plug jacket. For example, in invention patents such as "An Ice Plug Isolation Process for Nuclear Power Plant Explosion Valves" (application number 202110151208.3) and "A Multi-Jacketed Liquid Nitrogen Ice Invention Patent for Nuclear Power Plant Pipeline Maintenance," a single ice plug jacket (or multiple ice plug jackets tightly connected in series to form a large jacket) are used. This type of device has a significant drawback:

[0006] Firstly, before a single ice plug jacket (or multiple ice plug jackets tightly connected in series to form a large jacket) is completely sealed, the increased ice thickness reduces heat conduction, making it sensitive to water temperature changes. In environments with large pipe diameters and relatively high temperatures, sealing the ice plug is difficult, and it is not easy to form a reliable ice plug.

[0007] Secondly, the process system conditions required for ice plug isolation are harsh. Generally, it requires that the water in the pipeline is not flowing, there is no obvious heat exchange, and the water temperature in the pipeline does not exceed 30°C.

[0008] Given the aforementioned drawbacks, conventional ice plug isolation methods cannot be applied to condensate recirculation pipes where there is medium flow and hot and cold convection. Summary of the Invention

[0009] The purpose of this invention is to provide an online ice plug isolation method and device for condensate recirculation pipes, which solves the technical problems of existing ice plug technology, such as the long freezing time of liquid nitrogen ice plug single jacket and the inability to establish an ice plug with reliable load-bearing capacity on pipelines that are continuously in a "flowing" state and have heat exchange. It provides an effective technical means for online maintenance of condensate recirculation pipeline faults or valve defects without shutting down the system.

[0010] The technical solution of the present invention is as follows: A method for implementing online ice blockage isolation of condensate recirculation pipes involves temporarily adjusting the operating process parameters to increase the condensate level in the condenser heat sink, causing the horizontal pipe of the condensate recirculation pipe entering the condenser shell to be filled with water. The online ice blockage isolation device for the condensate recirculation pipe is installed on the horizontal pipe of the condensate recirculation pipe entering the condenser shell. This section of pipe is a common return water main pipe shared by multiple condensate recirculation pipes. The height difference between the highest point of the siphon section of the condensate recirculation pipe return water main pipe and the horizontal pipe entering the condenser shell is greater than 5 meters.

[0011] By utilizing existing condensate process system equipment and online ice blockage isolation devices to form a reliable isolation boundary, online maintenance of individual condensate recirculation valve failures or downstream pipeline defects can be completed without affecting the normal operation of adjacent condensate pumps.

[0012] Including the following:

[0013] Step 1: Collect technical information related to online ice blockage isolation of condensate recirculation pipes;

[0014] Step 2: Complete all necessary preparations for ice block isolation in advance, including preparation of ice block isolation devices, preparation of ice block jacket installation conditions, preparation of on-site water level measurement conditions, and preparation of monitoring instrument debugging.

[0015] Step 3: Complete all necessary preparations for defect repair in advance, including preparation of repair tools, repair materials, and repair process documents;

[0016] Step 4: Install the primary ice plug jacket and the secondary ice plug jacket into the ice plug working position;

[0017] Step 5: Complete the connection between the liquid nitrogen storage tank, liquid nitrogen delivery pipe and the primary ice plug jacket and the secondary ice plug jacket;

[0018] Step 6: Complete the installation of the temperature sensor probe of the patch temperature monitor and keep the patch temperature monitor in continuous monitoring mode;

[0019] Step 7: Perform the condenser heat trap liquid level raising operation according to the operating procedures, and keep the water level relatively stable. The final water level should completely submerge the horizontal pipe of the condensate recirculation pipe entering the condenser shell and be higher than the top of the horizontal pipe, and should not submerge the bottom titanium tube of the condenser.

[0020] Step 8: Measure the actual water level of the vertical pipe of the condensate recirculation pipe on site using an ultrasonic thickness gauge, and compare it with the indication value of the magnetic level gauge installed on site. The measured value should be consistent with the indication value of the magnetic level gauge, and the actual water level should be more than 200mm higher than the top of the horizontal pipe of the condensate recirculation pipe entering the condenser shell.

[0021] Step 9: Isolate the condensate recirculation pipeline to be inspected;

[0022] Step 10: Open the liquid nitrogen storage tank connected to the secondary ice plug jacket, let the liquid nitrogen enter the ice plug jacket cavity along the liquid nitrogen delivery pipe, and discharge it into the atmosphere from the ice plug jacket exhaust port. Adjust the liquid nitrogen flow rate in real time according to the temperature change trend of the patch-type temperature monitor.

[0023] Step 11: When the patch-type temperature monitor shows that the lowest temperature of the secondary ice plug jacket reaches -20℃, open the liquid nitrogen storage tank connected to the primary ice plug jacket to allow the primary ice plug jacket to play a cooling role.

[0024] Step 12: When the patch-type temperature monitor shows that the lowest temperature of the first-stage ice plug jacket has reached -15℃, reduce the liquid nitrogen flow rate of the first-stage ice plug jacket to maintain the lowest temperature at around -15℃.

[0025] Step 13: Continue to carry out liquid nitrogen ice plugging operation with secondary ice plug jacket. During the operation, use an ultrasonic thickness gauge to measure the actual water level in the vertical pipe of the condensate recirculation pipe every 20 minutes.

[0026] Step 14: When the length of frost on the pipe surface at both ends of the secondary ice plug jacket reaches 50mm, and the patch-type temperature monitor shows that the temperature values ​​at both ends of the secondary ice plug jacket are close and both reach below -50℃, it is preliminarily judged that the ice plug is completely sealed.

[0027] Step 15: Confirm that reliable ice plug isolation has been established by observing the changing trends of condenser vacuum, condenser water level, and ice plug jacket temperature, and that the conditions for carrying out online maintenance of condensate recirculation pipeline faults and valve defects are met.

[0028] Step 16: While maintaining the liquid nitrogen flow rate of the primary and secondary ice plug jackets, complete the online inspection and repair of condensate recirculation pipeline faults and valve defects.

[0029] Step 17: After the online maintenance work on the condensate recirculation pipeline fault and valve defect is completed, adjust the water level of the condenser heat sink to the normal operating value according to the operating procedures, and release the operation isolation;

[0030] Step 18: After confirming that the water level in the condenser heat sink has dropped to the normal operating value, stop the ice plugging operation, remove all parts of the ice plug isolation device, and wait for the annular ice column and ice plug in the condensate recirculation pipeline to melt and thaw naturally.

[0031] The online ice blockage isolation device for condensate recirculation pipelines includes a condenser, several parallel-operating condensate delivery pipelines, and a supporting condensate recirculation pipeline. The condenser is connected to the condensate pumps on each condensate delivery pipeline via a shared pipeline. Each condensate delivery pipeline and its supporting condensate recirculation pipeline includes one condensate pump inlet isolation valve, one condensate pump, one condensate pump outlet isolation valve, one condensate pump outlet pressure gauge root valve, one condensate pump outlet pressure gauge, one condensate pump recirculation valve, and one condensate pump air balancing valve. The condensate pump inlet isolation valve is connected to the condensate pump inlet via the condensate delivery pipeline. The condensate pump outlet is connected to the condensate pump outlet isolation valve via a condensate delivery pipeline. The condensate recirculation valve inlet is connected to the condensate pump outlet tee via a condensate recirculation pipeline. The condensate recirculation valve outlet is connected to the condensate recirculation pipe return main via a recirculation branch pipe. The end of the condensate recirculation pipe return main is connected to the condenser shell. The condensate pump outlet pressure gauge root valve and the condensate pump outlet pressure gauge are installed on the condensate delivery pipeline before the condensate pump outlet isolation valve. The condenser steam side shell is connected to the condensate delivery pipeline at the condensate pump inlet via an air pipeline. An air balancing valve is installed on the connected air pipeline.

[0032] The online ice plug isolation device includes a primary ice plug jacket, a secondary ice plug jacket, a liquid nitrogen storage tank, a liquid nitrogen delivery pipe, a patch-type temperature monitor, and an ultrasonic thickness gauge. The primary and secondary ice plug jackets are installed in series on the horizontal pipe from the condensate recirculation return water main into the condenser shell. The primary ice plug jacket is closer to the condenser shell, and the secondary ice plug jacket is farther away from the condenser shell. Two independent liquid nitrogen storage tanks are tightly connected to the primary and secondary ice plug jackets respectively through the liquid nitrogen delivery pipe.

[0033] The temperature sensing probe of the patch-type temperature monitor is installed on the annular cross-section where the two end faces of the condensate recirculation pipe intersect with the first-stage ice plug jacket and the second-stage ice plug jacket. The temperature sensing probe is evenly arranged along the circumference of the pipe cross-section.

[0034] The length of the secondary ice plug jacket is three times or more the diameter of the pipe.

[0035] The beneficial effects of this invention are as follows: By comprehensively applying technical means such as "temporarily adjusting the condenser heat trap water level," "coordinated operation of the primary and secondary ice plug jackets," and "real-time monitoring of ice plug temperature and pipeline water level changes," this invention achieves effective isolation of the condensate recirculation pipeline without disrupting the condenser vacuum. This solves the technical problem of not being able to perform online maintenance on condensate recirculation pipeline faults and valve defects during normal operation, achieving the following technical effects:

[0036] (1) This invention solves the problem of "no water" during normal operation of the condensate recirculation pipeline. The invention makes full use of the unit's operating experience, and the turbine operators temporarily raise the water level of the condenser heat sink so that the condenser water level submerges the horizontal pipe of the condensate recirculation return water main, so that the horizontal pipe of the condensate recirculation return water main reaches the "full water" state during operation, creating the basic conditions for ice blockage operation.

[0037] (2) This invention solves the problem of continuous "flow" and high temperature of condensate in the condenser, which is not conducive to ice block formation. The invention adopts a working method of coordinated operation of a primary ice block jacket and a secondary ice block jacket. The primary ice block jacket is used to create a partially closed annular ice column. On the one hand, it reduces the temperature of the condensate near the ice block jacket. On the other hand, the annular ice column counteracts the continuous fluctuation of the condensate, which significantly reduces the temperature of the condensate near the secondary ice block jacket, effectively suppresses the flow, and is more conducive to ice block formation.

[0038] (3) This invention solves the problem of not being able to effectively judge the effectiveness of ice plug formation. It utilizes a patch-type temperature monitor to monitor the temperature change trend of the ice plug in real time, providing ice plug operators with data to quickly assess the freezing effect of the ice plug jacket and adjust the liquid nitrogen flow rate accordingly. Simultaneously, ice plug operators cleverly apply the measurement principle of an ultrasonic thickness gauge to pipeline water level measurement, accurately measuring the actual water level in the condensate recirculation pipe using the ultrasonic thickness gauge, thus solving the problem of ice plug operators being unable to visually determine whether the ice plug is effective. Attached Figure Description

[0039] Figure 1 This is a process flow diagram of the online ice plug isolation method and apparatus for condensate recirculation pipes proposed in this embodiment of the invention;

[0040] Figure 2 This is a detailed diagram of the working arrangement of the online ice blockage isolation device for condensate recirculation pipe proposed in an embodiment of the present invention;

[0041] Figure 3 This is a schematic diagram of the annular ice column morphology of the primary ice plug jacket proposed in an embodiment of the present invention;

[0042] Figure 4This is a schematic diagram of the morphology of the secondary ice plug jacket proposed in an embodiment of the present invention.

[0043] In the diagram: 1. Condenser; 2. Inlet isolation valve of condensate pump No. 1; 3. Condensate pump No. 1; 4. Outlet isolation valve of condensate pump No. 1; 5. Pressure gauge root valve of outlet of condensate pump No. 1; 6. Pressure gauge of outlet of condensate pump No. 1; 7. Recirculation valve of condensate pump No. 1; 8. Recirculation valve of condensate pump No. 2; 9. Ice plug isolation device; 91. Primary ice plug jacket; 92. Secondary ice plug jacket; 93. Liquid nitrogen storage tank; 94. Liquid nitrogen delivery pipe; 95. Patch-type temperature monitor; 96. Ultrasonic thickness gauge; 10. Air balance valve of condensate pump No. 1; 11. Air balance valve of condensate pump No. 2; 12. Condensate pump No. 2. Detailed Implementation

[0044] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] This invention creates conditions for ice plug isolation by temporarily adjusting process parameters and uses a dedicated ice plug isolation device to complete online pipeline isolation.

[0046] According to the implementation case disclosed herein, online ice blockage isolation is proposed for the condensate recirculation pipe where the No. 1 condensate pump recirculation valve is located. The ice blockage isolation device is installed on the horizontal pipe where the condensate recirculation pipe return water main enters the condenser shell, with an outer diameter of 159 mm. The ice blockage isolation device includes a primary ice blockage jacket, a secondary ice blockage jacket, a liquid nitrogen delivery pipe, a liquid nitrogen storage tank, and equipment such as a patch-type temperature monitor and an ultrasonic thickness gauge for monitoring the ice blockage process.

[0047] To ensure the horizontal pipe leading to the condensate recirculation pipe in the condenser shell is fully filled with water, before implementing ice blockage isolation, the turbine operators must be contacted to raise the condensate level in the condenser heat sink according to the established operating procedures and maintain a relatively stable level. The final condensate level in the condenser heat sink should completely submerge the horizontal pipe leading to the condensate recirculation pipe in the condenser shell and be at least 200mm above the top of the horizontal pipe, but should not submerge the bottom titanium tubes of the condenser. The turbine operators monitor the final condensate level in the condenser heat sink using the condenser's built-in level gauge.

[0048] Ultrasonic thickness gauges are used to measure the true water level in condensate recirculation pipelines. Before formal use, the paint on the surface of the pipeline in the area to be measured must be removed, cleaned, and polished until the color of the metal body in the measurement area is completely exposed. Before ice plugging operations, the ice plugging isolation personnel first use an ultrasonic thickness gauge to measure the true water level in the vertical section of the condensate recirculation pipeline on-site. The measured true water level should be at least 200mm above the top of the horizontal pipeline and remain stable.

[0049] The primary and secondary ice plug jackets are installed in series on the horizontal pipe from the condensate recirculation pipeline into the condenser shell. The primary ice plug jacket is closer to the condenser shell, while the secondary ice plug jacket is further away. Two independent liquid nitrogen storage tanks are tightly connected to the primary and secondary ice plug jackets respectively via liquid nitrogen delivery pipes, providing a cold source for the ice plugs. In actual operation, the primary ice plug jacket does not form a completely sealed ice plug; its main function is to create a partially sealed annular ice column to absorb heat from the condensate flowing through it, lowering the condensate temperature and creating favorable conditions for the subsequent secondary ice plug jacket to form a reliable ice plug more quickly. The secondary ice plug jacket forms a completely sealed ice plug in actual operation. This requires the ice plug's length to be at least three times the pipe diameter, and the surface temperature of the ice plug to be -50°C or below, ensuring the ice plug can withstand the system's pressure differential and achieve reliable isolation.

[0050] The patch-type temperature monitoring instrument consists of several patch thermometers and a display screen. The sensing probes at one end of the patch thermometers are installed on the annular cross-section where the condensate recirculation pipe intersects with the two end faces of the primary and secondary ice plug jackets. The sensing probes are evenly distributed along the circumference of the pipe. All the leads at the other end of the patch thermometers are connected to the terminals on the display screen, allowing for real-time display of the actual temperature at the measured location, used to assess the freezing effect of the ice plug jacket.

[0051] After the turbine operators adjust the condensate level in the condenser heat sink and the ice-blocking personnel install and debug the ice-blocking isolation device, the ice-blocking operation can begin. The ice-blocking personnel control the cooling rate of the primary and secondary ice-blocking jackets by controlling the liquid nitrogen flow rate in the liquid nitrogen storage tank and monitoring the temperature change trend of the patch-type temperature monitor, always maintaining the cooling rate of the secondary ice-blocking jacket higher than that of the primary jacket. Since the primary function of the primary ice-blocking jacket is to cool the condensate, the liquid nitrogen flow rate should be appropriately reduced during operation to allow the temperature measurement value of the primary ice-blocking jacket to decrease slowly and remain around -15℃, preventing the formation of a sealed ice block. For the secondary ice-blocking jacket, the liquid nitrogen flow rate should be appropriately increased to increase the rate of temperature decrease and ultimately form a sealed ice block.

[0052] Once ice blockage has formed, maintenance personnel can perform online repairs on condensate recirculation valve malfunctions or pipeline defects. Throughout the maintenance process, ice blockage workers should continuously perform ice blockage operations to ensure the effectiveness of ice blockage isolation.

[0053] Throughout the entire process of ice plugging isolation, ice plugging operators should use an ultrasonic thickness gauge to regularly monitor the water level in the condensate recirculation pipeline, and the measurement results should always be basically consistent with the measurement results before the ice plugging operation.

[0054] After repairs are completed for condensate recirculation pipeline malfunctions or valve defects, ice plug operators close the shut-off valve of the liquid nitrogen storage tank, remove the ice plug isolation device, and allow the annular ice column and ice plug to thaw naturally.

[0055] like Figure 1 As shown in the diagram, an embodiment of the present invention provides a process flow diagram of an online ice blockage isolation method and apparatus for condensate recirculation pipes, including a condenser 1, condensate delivery pipeline No. 1, condensate delivery pipeline No. 2, condensate pump recirculation pipeline No. 1, condensate pump recirculation pipeline No. 2, and ice blockage isolation device 9. Condensate delivery pipeline No. 1 and condensate delivery pipeline No. 2 are two parallel pipelines, each connected to the heat sink of condenser 1 via a pipe. Condensate pump recirculation pipeline No. 1 and condensate pump recirculation pipeline No. 2 are connected to the condenser 1 shell via condensate recirculation pipelines. The ice blockage isolation device 9 is installed on a horizontal pipe connecting the common return water main of the two condensate recirculation pipelines to the condenser 1 shell. The elevation of the highest point of the siphon section of the condensate recirculation pipe return water main is +5.00 meters, and the elevation of the horizontal pipe into the condenser 1 shell is -2.00 meters.

[0056] The No. 1 condensate delivery pipeline includes condenser 1, No. 1 condensate pump inlet isolation valve 2, No. 1 condensate pump 3, No. 1 condensate pump outlet isolation valve 4, No. 1 condensate pump outlet pressure gauge root valve 5, No. 1 condensate pump outlet pressure gauge 6, and No. 1 condensate pump air balancing valve 10. Condenser 1 is connected to No. 1 condensate pump 3 via a condensate pipeline. The No. 1 condensate pump inlet isolation valve 2 is installed on the condensate pipeline connecting condenser 1 and No. 1 condensate pump 3. The outlet of No. 1 condensate pump 3 is connected to the No. 1 condensate pump outlet isolation valve 4 via a condensate pipeline. The outlet of No. 1 condensate pump 3 is connected to the No. 1 condensate pump outlet pressure gauge root valve 5 and No. 1 condensate pump outlet pressure gauge 6 via a condensate pipeline. The steam-side shell of condenser 1 is connected to the No. 1 condensate pump 3 inlet condensate pipeline via an air pipeline. The No. 1 condensate pump air balancing valve 10 is installed on the connected pipeline. Due to the need for maintenance of the No. 1 condensate pump recirculation valve 7 malfunction... Figure 1 Condensate pump No. 1 is shut down. Condensate pump inlet isolation valve 2, condensate pump outlet isolation valve 4, and condensate pump outlet pressure gauge root valve 5 are in the "closed" state.

[0057] The No. 1 condensate pump recirculation pipeline includes condenser 1, No. 1 condensate pump 3, and No. 1 condensate pump recirculation valve 7. Condenser 1 is connected to the outlet of No. 1 condensate pump 3 via a condensate recirculation pipeline, and No. 1 condensate pump recirculation valve 7 is installed on the condensate recirculation pipeline connecting condenser 1 and No. 1 condensate pump 3. The arrangement of the No. 2 condensate delivery pipeline is similar to that of the No. 1 condensate delivery pipeline. Figure 1 The No. 2 condensate pump is operating normally, and the inlet isolation valve, outlet isolation valve, and outlet pressure gauge root valve of the No. 2 condensate pump are all in the "open" state.

[0058] The layout of the No. 2 condensate pump recirculation pipeline is similar to that of the No. 1 condensate pump recirculation pipeline. Figure 1 Condensate pump 12 is operating normally, and recirculation valve 8 of condensate pump 2 is in the "closed" state.

[0059] like Figure 2 The diagram shows the detailed working arrangement of the ice plug isolation device 9. The ice plug isolation device 9 includes: a primary ice plug jacket 91, a secondary ice plug jacket 92, a liquid nitrogen storage tank 93, a liquid nitrogen delivery pipe 94, a patch-type temperature monitor 95, and an ultrasonic thickness gauge 96. The primary ice plug jacket 91 and the secondary ice plug jacket 92 are installed in series on the horizontal pipe from the condensate recirculation pipe into the condenser 1 shell, with the primary ice plug jacket 91 closer to the condenser shell and the secondary ice plug jacket 92 further away. Two independent liquid nitrogen storage tanks 93 are tightly connected to the primary ice plug jacket 91 and the secondary ice plug jacket 92 respectively via the liquid nitrogen delivery pipe 94. The temperature sensing probe of the patch-type temperature monitor 95 is installed on the annular cross-section where the two end faces of the condensate recirculation pipe intersect with those of the primary and secondary ice plug jackets 91 and 92, with the probe evenly distributed circumferentially along the pipe cross-section. The ultrasonic thickness gauge 96 is an independent measuring tool used during ice plugging operations to measure the actual water level in the vertical section of the condensate recirculation pipeline. The condenser pressure P1 is the pressure (i.e., condenser vacuum value) on the side of the secondary ice plug jacket 92 near the condenser shell, and the recirculation pipe pressure P2 is the pressure (P2 is equal to P1 before the ice plug is sealed; after the ice plug is fully formed, P2 is equal to the ambient atmospheric pressure)

[0060] like Figure 3 The diagram shows the annular icicle shape of the primary ice plug jacket 91. In actual operation, the primary ice plug jacket 91 does not form a completely closed ice plug. Its main function is to establish a partially closed annular icicle. On one hand, it absorbs the heat of the condensate flowing through the primary ice plug jacket, lowering the temperature of the condensate near the secondary ice plug jacket 92. On the other hand, the annular icicle counteracts fluctuations in the condensate, effectively suppressing the flow of condensate near the secondary ice plug jacket 92, thus promoting rapid ice plug formation.

[0061] like Figure 4 The diagram shows the ice plug shape of the secondary ice plug jacket 92. In actual operation, the secondary ice plug jacket 92 forms a completely sealed ice plug. The length of this ice plug jacket is selected according to the actual size of the pipe, generally requiring the length to be at least three times the pipe diameter to ensure that the final ice plug length is not less than three times the pipe diameter, thus achieving reliable isolation.

[0062] Combination Figure 1 , Figure 2 , Figure 3 , Figure 4The implementation steps of the present invention will be described in detail below:

[0063] The implementation method for online ice blockage isolation of condensate recirculation pipes includes the following:

[0064] Step 1: Collect technical information related to online ice blockage isolation of condensate recirculation pipe, including condensate level setpoints and related interlock controls, alarm information, condenser vacuum value, condensate temperature, technical data and maintenance isolation conditions of equipment to be maintained, safety risks and operational risks of online ice blockage and equipment maintenance, etc.

[0065] Step 2: Ice-blocking personnel complete all necessary preparations for ice block isolation in advance, including:

[0066] a. Preparation of ice plug isolation device: Prepare 1 primary ice plug jacket 91, 1 secondary ice plug jacket 92, a sufficient number of liquid nitrogen storage tanks 93 (to meet the needs of 4 hours of ice plug operation), 2 sets of liquid nitrogen delivery pipes 94, 1 set of patch-type temperature monitoring instrument 95, and 1 set of ultrasonic thickness gauge 96, and place them at the work site in advance.

[0067] b. Preparation for ice plug jacket installation: Remove the paint from the pipe surface at the installation locations of the primary ice plug jacket 91 and the secondary ice plug jacket 92 in advance. The area to be cleaned should be slightly larger than the length of the ice plug jacket. Clean and polish the pipe surface until the color of the metal body of the ice plug area is completely exposed.

[0068] c. Preparation of actual water level measurement conditions for condensate recirculation pipeline: Select an easy-to-operate location on the vertical pipe connected to the horizontal condensate recirculation pipeline as the water level measurement area, and remove the paint from the surface of the pipe in the area to be measured in advance, clean it and polish it until the color of the metal body of the measurement area is completely exposed.

[0069] d. Preparation for monitoring instrument debugging: Check in advance that the patch-type temperature monitor 95 and ultrasonic thickness gauge 96 have sufficient power, power on and test, and verify that the instruments are usable.

[0070] Step 3: Maintenance personnel complete all necessary preparations for defect repair in advance, including: preparation of repair tools and equipment, preparation of repair materials and preparation of repair process documents;

[0071] Step 4: The ice plugging operator applies ice plugging coupling agent evenly to the inner surfaces of the primary ice plugging jacket 91 and the secondary ice plugging jacket 92, and then installs the ice plugging jackets into the ice plugging operation position.

[0072] Step 5: Ice plugging workers follow... Figure 2 Complete the connection between the liquid nitrogen storage tank 93, the liquid nitrogen delivery pipe 94 and the first-stage ice plug jacket 91 and the second-stage ice plug jacket 92;

[0073] Step 6: The ice plugging operator installs the temperature sensing probe of the patch-type temperature monitor 95 on the annular cross-section where the two end faces of the condensate recirculation pipe intersect with the first-stage ice plug jacket 91 and the second-stage ice plug jacket 92. The probe is evenly distributed along the circumference of the pipe cross-section. After installation, the patch-type temperature monitor 95 is kept in continuous monitoring mode.

[0074] Step 7: The turbine operators temporarily release the interlock related to the high liquid level in the condenser 1 heat sink to create conditions for the water level raising operation;

[0075] Step 8: The turbine operator confirms that the No. 1 condensate pump air balance valve 10 is in the open position to balance the pressure on both sides of the secondary ice plug jacket 92;

[0076] Step 9: The turbine operator shall perform the condenser 1 heat trap liquid level raising operation according to the operating procedures and maintain a relatively stable water level. The final water level should completely submerge the horizontal pipe into the condensate recirculation pipe and be higher than the top of the horizontal pipe, but should not submerge the bottom titanium tubes of the condenser;

[0077] Step 10: The ice plug operator uses an ultrasonic thickness gauge 96 to measure the actual water level in the vertical pipe of the condensate recirculation pipe on site, and compares it with the indication value of the magnetic float level gauge installed on site. The measured value is required to be basically consistent with the indication value of the magnetic float level gauge, and the actual water level is more than 200mm higher than the top of the horizontal pipe of the condensate recirculation pipe entering the condenser shell.

[0078] Step 11: The turbine operators isolate the recirculation pipeline to be inspected: shut down No. 1 condensate pump 3, close the No. 1 condensate pump inlet isolation 2, close the No. 1 condensate pump outlet isolation valve 4, close the No. 1 condensate pump outlet pressure gauge root valve 5, close the No. 1 condensate pump air balance valve 10, etc.

[0079] Step 12: The ice-plugging operator slowly opens the liquid nitrogen storage tank 93 connected to the secondary ice-plugging jacket 92, allowing liquid nitrogen to enter the ice-plugging jacket cavity along the liquid nitrogen delivery pipe 94 and be discharged into the atmosphere from the ice-plugging jacket vent. The liquid nitrogen flow rate is adjusted in real time according to the temperature change trend of the patch-type temperature monitor 95, so that the ice-plugging freezing rate always shows a continuous decreasing trend;

[0080] Step 13: When the patch-type temperature monitor 95 shows that the minimum temperature of the secondary ice plug jacket 92 reaches -20℃, the ice plug operator slowly opens the liquid nitrogen storage tank 93 connected to the primary ice plug jacket 91 so that the primary ice plug jacket 91 can play a cooling role.

[0081] Step 14: When the patch-type temperature monitor 95 shows that the minimum temperature of the first-stage ice plug jacket 91 has reached -15℃, the ice plug operator should appropriately reduce the liquid nitrogen flow rate of the first-stage ice plug jacket 91 to maintain the minimum temperature at around -15℃.

[0082] Step 15: The ice-plugging personnel continue the liquid nitrogen ice-plugging operation using the secondary ice-plugging jacket 92. During the operation, the actual water level in the vertical pipe of the condensate recirculation pipe is measured every 20 minutes using an ultrasonic thickness gauge 96. Throughout the ice-plugging operation, the actual water level in the vertical pipe of the condensate recirculation pipe should remain essentially constant. After the ice plug is completely sealed, the actual water level in the vertical pipe should rise slightly due to the volume change caused by water freezing.

[0083] Step 16: When the length of frost on the pipe surface at both ends of the secondary ice plug jacket 92 reaches 50mm, and the surface mount temperature monitor 95 shows that the temperature values ​​of each probe at both ends of the secondary ice plug jacket 92 are approximately the same. near When all temperatures reach below -50°C, it can be preliminarily determined that the ice plug is completely sealed.

[0084] Step 17: While maintaining the liquid nitrogen flow rate of the primary ice plug jacket 91 and the secondary ice plug jacket 92, perform the following operations to verify the reliability of the ice plug isolation:

[0085] a. The maintenance personnel remove the No. 1 condensate pump outlet pressure gauge 6, and the turbine operation personnel slowly open the No. 1 condensate pump outlet pressure gauge root valve 5 to allow air to enter the condenser recirculation pipe, breaking the vacuum in the condensate recirculation pipe, until the pressure P2 of the condenser recirculation pipe is equal to the ambient atmospheric pressure, and the No. 1 condensate pump outlet pressure gauge root valve 5 no longer draws in air.

[0086] b. During the process of the turbine operator slowly opening the root valve 5 of the outlet pressure gauge of the No. 1 condensate pump, the ice plug operator uses an ultrasonic thickness gauge 96 to continuously monitor the actual water level in the vertical pipe of the condensate recirculation pipe. The turbine operator continuously monitors the condenser vacuum change. Once the water level or condenser vacuum drops, the root valve 5 of the outlet pressure gauge of the No. 1 condensate pump should be closed immediately.

[0087] c. After the vacuum in the condensate recirculation pipe is broken, continue to observe for half an hour. If it is confirmed that the condenser vacuum is stable, the actual water level in the vertical pipe of the condensate recirculation pipe has not changed, and the temperature of the secondary ice plug jacket 92 is maintained below -50℃ and has no upward trend, then it can be confirmed that a reliable ice plug isolation has been established, and the conditions for carrying out online inspection and maintenance of condensate recirculation pipe faults and valve defects are met.

[0088] Step 18: While maintaining the liquid nitrogen flow rate of the primary ice plug jacket 91 and the secondary ice plug jacket 92, the maintenance personnel complete the online inspection and repair of condensate recirculation pipeline faults and valve defects.

[0089] Step 19: After the online maintenance work on the condensate recirculation pipeline fault and valve defect is completed, the turbine operation personnel shall adjust the heat sink water level of condenser 1 to the normal operating value in accordance with the operating procedures and release the operation isolation.

[0090] Step 20: After confirming that the water level in the heat trap of condenser 1 has dropped to the normal operating value, the ice plug operator closes the shut-off valve of liquid nitrogen storage tank 93, removes all parts of ice plug isolation device 9, and waits for the annular ice column and ice plug to melt and thaw naturally.

Claims

1. A method for implementing online ice blockage isolation in condensate recirculation pipes, characterized in that: By temporarily adjusting the operating process parameters to increase the condensate level in the condenser heat sink, the horizontal pipe of the condensate recirculation pipe entering the condenser shell is filled with water. The online ice blockage isolation device of the condensate recirculation pipe is installed on the horizontal pipe of the condensate recirculation pipe entering the condenser shell. This section of the pipe is a return water main pipe shared by multiple condensate recirculation pipes. The height difference between the highest point of the siphon section of the condensate recirculation pipe return water main pipe and the horizontal pipe entering the condenser shell is greater than 5 meters.

2. The method for implementing online ice blockage isolation in condensate recirculation pipes as described in claim 1, characterized in that: By utilizing existing condensate process system equipment and online ice blockage isolation devices to form a reliable isolation boundary, online maintenance of individual condensate recirculation valve failures or downstream pipeline defects can be completed without affecting the normal operation of adjacent condensate pumps.

3. The method for implementing online ice blockage isolation in condensate recirculation pipes as described in claim 1 or 2, characterized in that: Including the following: Step 1: Collect technical information related to online ice blockage isolation of condensate recirculation pipes; Step 2: Complete all necessary preparations for ice block isolation in advance, including preparation of ice block isolation devices, preparation of ice block jacket installation conditions, preparation of on-site water level measurement conditions, and preparation of monitoring instrument debugging. Step 3: Complete all necessary preparations for defect repair in advance, including preparation of repair tools, repair materials, and repair process documents; Step 4: Install the primary ice plug jacket and the secondary ice plug jacket into the ice plug operation position; Step 5: Complete the connection between the liquid nitrogen storage tank, liquid nitrogen delivery pipe and the primary ice plug jacket and the secondary ice plug jacket; Step 6: Complete the installation of the temperature sensor probe of the patch temperature monitor and keep the patch temperature monitor in continuous monitoring mode; Step 7: Perform the condenser heat trap liquid level raising operation according to the operating procedures, and keep the water level relatively stable. The final water level should completely submerge the horizontal pipe of the condensate recirculation pipe entering the condenser shell and be higher than the top of the horizontal pipe, and should not submerge the bottom titanium tube of the condenser. Step 8: Measure the actual water level of the vertical pipe of the condensate recirculation pipe on site using an ultrasonic thickness gauge, and compare it with the indication value of the magnetic level gauge installed on site. The measured value should be consistent with the indication value of the magnetic level gauge, and the actual water level should be more than 200mm higher than the top of the horizontal pipe of the condensate recirculation pipe entering the condenser shell. Step 9: Isolate the condensate recirculation pipeline to be inspected; Step 10: Open the liquid nitrogen storage tank connected to the secondary ice plug jacket, let the liquid nitrogen enter the ice plug jacket cavity along the liquid nitrogen delivery pipe, and discharge it into the atmosphere from the ice plug jacket exhaust port. Adjust the liquid nitrogen flow rate in real time according to the temperature change trend of the patch-type temperature monitor. Step 11: When the patch-type temperature monitor shows that the lowest temperature of the secondary ice plug jacket reaches -20℃, open the liquid nitrogen storage tank connected to the primary ice plug jacket to allow the primary ice plug jacket to play a cooling role. Step 12: When the patch-type temperature monitor shows that the lowest temperature of the first-stage ice plug jacket has reached -15℃, reduce the liquid nitrogen flow rate of the first-stage ice plug jacket to maintain the lowest temperature at around -15℃. Step 13: Continue to carry out liquid nitrogen ice plugging operation with secondary ice plug jacket. During the operation, use an ultrasonic thickness gauge to measure the actual water level in the vertical pipe of the condensate recirculation pipe every 20 minutes. Step 14: When the length of frost on the pipe surface at both ends of the secondary ice plug jacket reaches 50mm, and the patch-type temperature monitor shows that the temperature values ​​at both ends of the secondary ice plug jacket are close and both reach below -50℃, it is preliminarily judged that the ice plug is completely sealed. Step 15: Confirm that reliable ice plug isolation has been established by observing the changing trends of condenser vacuum, condenser water level, and ice plug jacket temperature, and that the conditions for carrying out online maintenance of condensate recirculation pipeline faults and valve defects are met. Step 16: While maintaining the liquid nitrogen flow rate of the primary and secondary ice plug jackets, complete the online inspection and repair of condensate recirculation pipeline faults and valve defects. Step 17: After the online maintenance work on the condensate recirculation pipeline fault and valve defect is completed, adjust the water level of the condenser heat sink to the normal operating value according to the operating procedures, and release the operation isolation; Step 18: After confirming that the water level in the condenser heat sink has dropped to the normal operating value, stop the ice plugging operation, remove all parts of the ice plug isolation device, and wait for the annular ice column and ice plug in the condensate recirculation pipeline to melt and thaw naturally.

4. An online ice blockage isolation device for condensate recirculation pipes, characterized in that: The system includes a condenser, several parallel-operating condensate delivery pipelines, and associated condensate recirculation pipelines. The condenser is connected to the condensate pumps on each condensate delivery pipeline via a shared pipeline. Each condensate delivery pipeline and associated condensate recirculation pipeline includes one condensate pump inlet isolation valve, one condensate pump, one condensate pump outlet isolation valve, one condensate pump outlet pressure gauge root valve, one condensate pump outlet pressure gauge, one condensate pump recirculation valve, and one condensate pump air balancing valve. The condensate pump inlet isolation valve is connected to the condensate pump inlet via the condensate delivery pipeline, and the condensate pump outlet is connected to the condensate pump outlet via the condensate recirculation pipeline. The condensate delivery pipeline is connected to the condensate pump outlet isolation valve. The inlet of the condensate recirculation valve is connected to the condensate pump outlet tee via the condensate recirculation pipeline. The outlet of the condensate recirculation valve is connected to the condensate recirculation return water main via the recirculation branch pipe. The end of the condensate recirculation return water main is connected to the condenser shell. The condensate pump outlet pressure gauge root valve and the condensate pump outlet pressure gauge are installed on the condensate delivery pipeline before the condensate pump outlet isolation valve. The steam side shell of the condenser is connected to the condensate delivery pipeline at the condensate pump inlet via an air pipeline. An air balancing valve is installed on the connected air pipeline.

5. The online ice blockage isolation device for condensate recirculation pipes as described in claim 4, characterized in that: The online ice plug isolation device includes a primary ice plug jacket, a secondary ice plug jacket, a liquid nitrogen storage tank, a liquid nitrogen delivery pipe, a patch-type temperature monitor, and an ultrasonic thickness gauge. The primary and secondary ice plug jackets are installed in series on the horizontal pipe from the condensate recirculation return water main into the condenser shell. The primary ice plug jacket is closer to the condenser shell, and the secondary ice plug jacket is farther away from the condenser shell. Two independent liquid nitrogen storage tanks are tightly connected to the primary and secondary ice plug jackets respectively through the liquid nitrogen delivery pipe.

6. The online ice blockage isolation device for condensate recirculation pipes as described in claim 4, characterized in that: The temperature sensing probe of the patch-type temperature monitor is installed on the annular cross-section where the two end faces of the condensate recirculation pipe intersect with the first-stage ice plug jacket and the second-stage ice plug jacket. The temperature sensing probe is evenly arranged along the circumference of the pipe cross-section.

7. The online ice blockage isolation device for condensate recirculation pipes as described in claim 4, characterized in that: The length of the secondary ice plug jacket is three times or more the diameter of the pipe.

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