Steam extraction check valve electromagnetic valve of steam turbine and jamming prevention method

Abstract

The invention discloses a steam extraction check valve electromagnetic valve of a steam turbine and a jamming prevention method. A single-exhaust-path structure easily causes an airflow turbulence phenomenon, under the working condition of 1.2 MPa high pressure, the pressure loss is increased by more than 35% due to airflow steering resistance, and the flow fluctuation amplitude reaches 12% when the load is low, so that the quick response requirement during variable-load operation of a unit cannot be met. The method comprises the following steps that a dual-channel-large-stroke-optimized flaring integrated fluid power structure is constructed; constructing a metal-metal sealing and high-temperature sealing grease compensation material system; a nitriding treatment process is adopted for the piston rod to form a nitriding layer, a laser centering technology is adopted for adjusting the connecting portion of the cylinder piston rod and the check valve, and coaxiality deviation is controlled. The electromagnetic valve is used for preventing jamming of the steam extraction check valve of the steam turbine.

Description

Technical Field

[0001] This invention relates to a solenoid valve for a steam turbine extraction non-return valve and a method for preventing jamming. Background Technology

[0002] As a crucial energy base in my country, Xinjiang's power industry development plays a vital role in ensuring the stable operation of the regional economy and society and the implementation of the national energy strategy. Huadian Kuqa Power Generation Co., Ltd., a major thermal power plant in southern Xinjiang, has a total installed capacity of 660,000 kilowatts, equipped with two 330MW steam turbine generator units, undertaking the core power supply tasks for industrial production and residential electricity consumption in Kuqa and surrounding areas. The company's No. 4 steam turbine unit, as one of its main power generation devices, operates long-term in Xinjiang's unique climate and operating conditions—summer ambient temperatures can reach over 40℃, and the temperature of the medium in the extraction steam non-return valve area is maintained at 350℃±20℃, with a pressure of 1.2MPa±0.1MPa. Furthermore, influenced by the regional power grid's peak-shaving demands, the unit frequently switches loads between 30% and 100% of its rated power, placing extremely high demands on the equipment's adaptability and operational reliability.

[0003] As a core component of the turbine regulation and safety system, the extraction steam non-return valve's functional integrity directly determines the unit's operational safety. The total closing time of the extraction steam non-return valve directly connected to the turbine cylinder should be less than 1 second. Article 8.1.12 of the National Energy Administration's "Twenty-Five Key Requirements for Preventing Power Production Accidents (2023 Edition)" also emphasizes the need to adhere to regulations in conducting extraction steam non-return valve closing time tests and in-operation activity tests to ensure flexible valve operation without jamming. However, the extraction steam non-return valve solenoid valve originally installed in Unit 4 of Huadian Kuche Power Generation Co., Ltd. was a product of the British company DAVIS. Having been in continuous operation for over 10 years, under long-term high temperature, high pressure, and variable load conditions, it gradually revealed a series of technical defects, becoming a major hidden danger to the unit's safe operation.

[0004] From a fluid dynamics perspective, the original solenoid valve adopted a single exhaust path design with an exhaust channel cross-sectional area of ​​only 28 mm² and a measured exhaust flow rate of only 0.8 m³ / min. This resulted in a total closing time of 1.3 seconds for the extraction non-return valve, significantly exceeding the requirements of the DL / T711-2019 standard. Further on-site investigation revealed that the single exhaust path structure easily induces airflow turbulence. Under 1.2 MPa high-pressure conditions, the airflow turning resistance increases pressure loss by more than 35%, and the flow fluctuation reaches 12% at low loads, failing to meet the rapid response requirements of the unit during variable load operation. In addition, the original solenoid valve's exhaust port expansion angle is 30°, which easily generates eddies when airflow passes through, further prolonging the valve closing time. In emergencies such as heater overfilling leading to steam backflow or a plant-wide power outage, the non-return valve may fail to close in time, directly causing turbine overspeed or even runaway accidents with unimaginable consequences.

[0005] Regarding high-temperature material resistance, the original solenoid valve core sealing assembly was made of nitrile rubber, with a temperature resistance limit of only 250℃, far lower than the actual operating temperature of 350℃±20℃ for the No. 4 unit's steam extraction system. Under prolonged high temperatures, the nitrile rubber sealing rings experienced severe aging and embrittlement. On-site testing data in 2024 showed that the solenoid valve leakage rate was as high as 37%, not only wasting compressed air but also causing insufficient cylinder driving force, further exacerbating the problem of delayed check valve operation. Simultaneously, the original solenoid valve body lacked a dedicated heat dissipation structure. In summer, with an ambient temperature of 35℃, the measured surface temperature of the valve body reached 82℃, far exceeding the material's safe operating temperature range, accelerating the aging and failure of the sealing components. On average, the sealing rings needed to be replaced every three months, increasing maintenance costs and frequently interrupting the unit's stable operation. Statistics show that in 2024, unplanned shutdowns due to solenoid valve seal failure totaled 12 hours, directly impacting power generation by approximately 396,000 kWh.

[0006] Mechanical jamming of the actuator is also a prominent problem. The piston rod surface of the original extraction steam non-return valve lacked effective protective measures, and in the presence of Cl-containing compounds… - Under long-term corrosion from the steam medium, the surface oxide layer thickness exceeds 0.05mm, leading to increased frictional resistance between the piston rod and the seal, and frequent jamming during operation tests. Simultaneously, the coaxiality deviation between the piston rod and the non-return valve connection reaches 0.15mm, further exacerbating motion resistance. Field test data from 2024 shows that the button operation force exceeds 30N, far exceeding ergonomic design requirements. Furthermore, the on-site operation button is installed as high as 4.5m above the ground, requiring operators to use climbing equipment to complete the test, which is not only inconvenient but also poses a safety risk of working at height. In addition, the single-acting cylinder spring is constantly operating at 80% compression, and the spring stiffness has decreased from the design value of 50N / mm to 35N / mm, significantly reducing its elastic recovery capacity. This fails to provide sufficient driving force for closing the non-return valve, creating a vicious cycle of "jamming - insufficient driving force - closing timeout".

[0007] The unique steam quality and climate conditions in Xinjiang further amplified the aforementioned technical deficiencies. The Cl content in the water in this region... - The content is relatively high, although the vapor Cl is reduced after treatment. - The concentration was controlled at around 0.1 ppm, but long-term operation still caused localized corrosion on the original solenoid valve body and piston rod. A disassembly inspection in 2024 revealed pitting corrosion on the surface of the 316L stainless steel valve core, with a maximum depth of 0.02 mm. Continued operation would lead to failure of the valve core sealing surface. Meanwhile, the large diurnal temperature range in Xinjiang causes frequent thermal expansion and contraction of metal components. The original solenoid valve core and sleeve used a clearance fit design, which did not account for thermal expansion differences. Temperature fluctuations resulted in a 0.03 mm change in the clearance, further exacerbating the risk of leakage and jamming.

[0008] Based on the above research and analysis, the existing extraction steam non-return valve solenoid valve and actuator can no longer meet the safe and stable operation requirements of Unit 4. There is an urgent need to overcome four major technical bottlenecks through technological research and development: fluid dynamics optimization, high-temperature material matching, actuator anti-jamming, and heat dissipation structure design. Furthermore, it is necessary to develop a system adapted to the high-temperature, high-Cl-temperature conditions of Xinjiang. - The development of this device, including a non-return valve solenoid valve for variable load conditions and a periodic operation test to prevent jamming, not only addresses the safety hazards of Unit 4 at Huadian Kuche Power Generation Co., Ltd., but also provides a widely applicable technical solution for similar thermal power units in Xinjiang and even nationwide. This has significant practical implications for improving the operational reliability of thermal power generation equipment and ensuring the safety of the regional power grid. Summary of the Invention

[0009] The purpose of this invention is to provide a steam turbine extraction non-return valve solenoid valve and a method for preventing jamming, so as to solve the above-mentioned technical problems.

[0010] The above objectives are achieved through the following technical solutions: A solenoid valve for a steam turbine extraction non-return valve and a method for preventing jamming, the method comprising the following steps: Step 1: Construct a dual-channel, long-stroke, optimized flared integrated fluid dynamic structure; Step 2: Construct a material system for metal-to-metal sealing combined with high-temperature sealing grease compensation; Step 3: The piston rod is subjected to nitriding treatment to form a nitrided layer. Laser alignment technology is used to adjust the connection between the cylinder piston rod and the non-return valve to control the coaxiality deviation.

[0011] The aforementioned turbine extraction non-return valve solenoid valve and anti-jamming method, specifically step one, involves: adopting a parallel dual exhaust channel layout, increasing the single channel cross-sectional area from the existing 28mm² to over 56mm², adjusting the exhaust port flare angle from 30° to 45°, and increasing the valve core stroke from 6mm to 10mm, thus constructing an integrated fluid dynamic structure of "dual channel - large stroke - optimized flare"; simulating high temperature conditions of 350℃±20℃ and high pressure conditions of 1.2MPa±0.1MPa, using a PT124B-210 pressure sensor to measure the exhaust flow rate, and using a high-speed camera system to record the valve core action process, analyzing the airflow turbulence state, and verifying the suppression effect of the dual exhaust path on pressure loss; simultaneously, using an EMF-8700 electromagnetic flowmeter to continuously monitor the flow stability across the entire load range, ensuring that the flow rate meets the expected indicators under low, medium, and high loads.

[0012] The aforementioned turbine extraction non-return valve solenoid valve and anti-jamming method, specifically step two involves: selecting 316L austenitic stainless steel to manufacture the valve core and valve sleeve, and matching it with high-temperature cylinder sealing grease to construct a metal-to-metal seal + high-temperature sealing grease compensation material system. Material compatibility tests are conducted on-site, and a leakage rate detector is used to monitor leakage at the sealing interface. The corrosion rate of 316L stainless steel in the steam medium is measured using a weightless balance to ensure that the annual corrosion amount is <0.01mm. Simultaneously, a temperature monitoring instrument is used to track the thermal expansion difference between the stainless steel and the carbon steel cylinder block, verifying the temperature-sensitive compensation effect of the sealing grease, preventing gaps at the sealing interface under high-temperature conditions, and achieving a zero-leakage sealing target.

[0013] The specific process of step three in the aforementioned turbine extraction non-return valve solenoid valve and anti-jamming method is as follows: (1) The piston rod is subjected to nitriding process to form a 0.3mm thick nitrided layer. The surface hardness is verified by hardness tester to be ≥HV600; (2) Use laser alignment technology to adjust the connection between the cylinder piston rod and the non-return valve, use a dial indicator to control the coaxiality deviation ≤0.05mm, configure a filter pressure reducing valve, and combine with a displacement sensor to monitor the spring stroke to maintain the working stroke of the single-acting cylinder spring in the range of 60%-70% to avoid elastic decay caused by long-term compression. (3) On the production site, the actuator’s ability to run without jamming was tested by manually rotating the gate lever 90°. The response time of the dual-mode activity test was recorded by a timer. The flexible sensing button structure was optimized to ensure that the operating force met the expected indicators. Beneficial effects

[0014] 1. This invention features a dual exhaust channel symmetrically arranged along the axis of the solenoid valve body. The cross-sectional area of ​​a single channel is increased from the original 28mm² to ≥56mm², doubling the total exhaust cross-sectional area. The valve core stroke is increased from 6mm to 10mm, extending the effective opening time. The exhaust port expansion angle is adjusted from 30° to 45°, reducing airflow turning resistance. This design, observed on-site by a FASTCAMMiniAX200 high-speed camera system, can effectively suppress airflow turbulence.

[0015] 2. This invention uses a PT124B-210 pressure sensor to measure exhaust flow and an EMF-8700 electromagnetic flowmeter to monitor full-load stability, achieving an exhaust flow rate of ≥1.6 m³ / min for the solenoid valve and a total closing time of ≤1.0 s for the extraction steam check valve, which meets the requirements of Clause 4.8.2 of DL / T711-2019 standard. The flow fluctuation amplitude under low, medium, and high loads is ≤5%, and the turbulence loss is reduced by more than 30%.

[0016] 3. This invention constructs a composite system of 316L stainless steel metal seal + Weili Energy MFZ-3 high-temperature sealing grease to solve the problem of sealing performance and material compatibility under high-temperature conditions.

[0017] 4. This invention uses 316L austenitic stainless steel conforming to GB / T1220-2019 standard to make valve core and valve sleeve, and is equipped with Weili Energy MFZ-3 high temperature sealing grease with a temperature resistance of 685℃ and a pressure resistance of 32.5MPa. The temperature-sensitive characteristics of the sealing grease are used to compensate for the thermal expansion difference between carbon steel and stainless steel in the cylinder block, and to avoid the generation of gaps at the sealing interface.

[0018] 5. In this invention, the sealing interface is monitored on-site using an HLT-500 leak rate detector to achieve a leak rate of 0; the corrosion rate of 316L stainless steel in steam medium is measured using a Mettler Toledo XS205 weight loss balance, with an annual corrosion amount of <0.01mm; combined with an Agilent 34972A temperature monitoring instrument to track thermal expansion differences, the leak rate is still ≤0.05% under the extreme temperature condition of 370℃, and the upper limit of the sealing component's temperature resistance is increased to ≥685℃.

[0019] 6. The present invention employs a nitriding process to form a 0.3mm thick nitrided layer on the piston rod. The surface hardness is verified to be ≥HV600 using an HV-1000 Vickers hardness tester, which inhibits the formation of an oxide layer. Laser alignment technology is used to adjust the connection between the piston rod and the check valve, and a Mitutoyo 543-262 dial indicator is used to control the coaxiality deviation to be ≤0.05mm, thereby reducing the frictional resistance during movement.

[0020] 7. This invention is equipped with an SMCIR2000-02 filter pressure reducing valve, combined with a KeyenceGT2-P12K displacement sensor to monitor the spring stroke in real time, maintaining the working stroke of the single-acting cylinder spring in the range of 60%-70%, and avoiding elastic decay caused by long-term excessive compression. Detailed Implementation

[0021] A solenoid valve for a steam turbine extraction non-return valve and a method for preventing jamming, the method comprising the following steps: Step 1: Construct a dual-channel, long-stroke, optimized flared integrated fluid dynamic structure; Step 2: Construct a material system for metal-to-metal sealing combined with high-temperature sealing grease compensation; Step 3: The piston rod is subjected to nitriding treatment to form a nitrided layer. Laser alignment technology is used to adjust the connection between the cylinder piston rod and the non-return valve to control the coaxiality deviation.

[0022] The aforementioned turbine extraction non-return valve solenoid valve and anti-jamming method, specifically step one, involves: adopting a parallel dual exhaust channel layout, increasing the single channel cross-sectional area from the existing 28mm² to over 56mm², adjusting the exhaust port flare angle from 30° to 45°, and increasing the valve core stroke from 6mm to 10mm, thus constructing an integrated fluid dynamic structure of "dual channel - large stroke - optimized flare"; simulating high temperature conditions of 350℃±20℃ and high pressure conditions of 1.2MPa±0.1MPa, using a PT124B-210 pressure sensor to measure the exhaust flow rate, and using a high-speed camera system to record the valve core action process, analyzing the airflow turbulence state, and verifying the suppression effect of the dual exhaust path on pressure loss; simultaneously, using an EMF-8700 electromagnetic flowmeter to continuously monitor the flow stability across the entire load range, ensuring that the flow rate meets the expected indicators under low, medium, and high loads.

[0023] The aforementioned turbine extraction non-return valve solenoid valve and anti-jamming method, specifically step two involves: selecting 316L austenitic stainless steel to manufacture the valve core and valve sleeve, and matching it with high-temperature cylinder sealing grease to construct a metal-to-metal seal + high-temperature sealing grease compensation material system. Material compatibility tests are conducted on-site, and a leakage rate detector is used to monitor leakage at the sealing interface. The corrosion rate of 316L stainless steel in the steam medium is measured using a weightless balance to ensure that the annual corrosion amount is <0.01mm. Simultaneously, a temperature monitoring instrument is used to track the thermal expansion difference between the stainless steel and the carbon steel cylinder block, verifying the temperature-sensitive compensation effect of the sealing grease, preventing gaps at the sealing interface under high-temperature conditions, and achieving a zero-leakage sealing target.

[0024] 4. The turbine extraction non-return valve solenoid valve and anti-jamming method according to claim 3, characterized in that: the specific process of step three is as follows: (1) The piston rod is subjected to nitriding process to form a 0.3mm thick nitrided layer. The surface hardness is verified by hardness tester to be ≥HV600; (2) Use laser alignment technology to adjust the connection between the cylinder piston rod and the non-return valve, use a dial indicator to control the coaxiality deviation ≤0.05mm, configure a filter pressure reducing valve, and combine with a displacement sensor to monitor the spring stroke to maintain the working stroke of the single-acting cylinder spring in the range of 60%-70% to avoid elastic decay caused by long-term compression. (3) On the production site, the actuator’s ability to run without jamming was tested by manually rotating the gate lever 90°. The response time of the dual-mode activity test was recorded by a timer. The flexible sensing button structure was optimized to ensure that the operating force met the expected indicators.

Claims

1. A solenoid valve for a steam turbine extraction non-return valve and a method for preventing jamming, characterized in that: The method includes the following steps: Step 1: Construct a dual-channel, long-stroke, optimized flared integrated fluid dynamic structure; Step 2: Construct a material system for metal-to-metal sealing combined with high-temperature sealing grease compensation; Step 3: The piston rod is subjected to nitriding treatment to form a nitrided layer. Laser alignment technology is used to adjust the connection between the cylinder piston rod and the non-return valve to control the coaxiality deviation.

2. The solenoid valve for steam turbine extraction non-return valve and the method for preventing jamming as described in claim 1, characterized in that: The specific process of step one is as follows: adopting a parallel dual exhaust channel layout, increasing the cross-sectional area of ​​a single channel from the existing 28mm² to over 56mm², adjusting the exhaust port flare angle from 30° to 45°, and increasing the valve core stroke from 6mm to 10mm, constructing an integrated fluid dynamic structure of "dual channel - large stroke - optimized flare"; simulating high temperature conditions of 350℃±20℃ and high pressure conditions of 1.2MPa±0.1MPa, using a PT124B-210 pressure sensor to measure the exhaust flow rate, and using a high-speed camera system to record the valve core action process, analyzing the airflow turbulence state, verifying the suppression effect of the dual exhaust path on pressure loss, and simultaneously using an EMF-8700 electromagnetic flowmeter to continuously monitor the flow stability across the entire load range, ensuring that the flow rate can reach the expected indicators under low, medium, and high loads.

3. The solenoid valve for steam turbine extraction non-return valve and the method for preventing jamming as described in claim 2, characterized in that: The specific process of step two is as follows: 316L austenitic stainless steel is selected to make the valve core and valve sleeve, and high-temperature cylinder sealing grease is used to construct a material system of metal-to-metal sealing + high-temperature sealing grease compensation. Material compatibility tests are conducted on the production site, and a leakage rate detector is used to monitor leakage at the sealing interface. The corrosion rate of 316L stainless steel in the steam medium is measured using a weightless balance to ensure that the annual corrosion amount is <0.01mm. Simultaneously, a temperature monitoring instrument is used to track the thermal expansion difference between the stainless steel and the carbon steel of the cylinder block, verifying the temperature-sensitive compensation effect of the sealing grease, avoiding gaps at the sealing interface under high-temperature conditions, and achieving the goal of zero-leakage sealing.

4. The solenoid valve for steam turbine extraction non-return valve and the method for preventing jamming as described in claim 3, characterized in that: The specific process of step three is as follows: (1) The piston rod is subjected to nitriding process to form a 0.3mm thick nitrided layer. The surface hardness is verified by hardness tester to be ≥HV600; (2) Use laser alignment technology to adjust the connection between the cylinder piston rod and the non-return valve, use a dial indicator to control the coaxiality deviation ≤0.05mm, configure a filter pressure reducing valve, and combine with a displacement sensor to monitor the spring stroke to maintain the working stroke of the single-acting cylinder spring in the range of 60%-70% to avoid elastic decay caused by long-term compression. (3) On the production site, the actuator’s ability to run without jamming was tested by manually rotating the gate lever 90°. The response time of the dual-mode activity test was recorded by a timer. The flexible sensing button structure was optimized to ensure that the operating force met the expected indicators.