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Release time :
Jan 18,2026
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Condenser vacuum is a core parameter in the thermal cycle of steam turbine units. Vacuum leakage represents one of the most common failures in power plant turbines, occurring when external air or non-condensable gases infiltrate the condenser or vacuum system through equipment gaps.
Condenser vacuum is a core parameter in the thermal cycle of steam turbine units. Vacuum leakage represents one of the most common failures in power plant turbines, occurring when external air or non-condensable gases infiltrate the condenser or vacuum system through equipment gaps. This leads to reduced condenser vacuum and increased back pressure. Vacuum leakage not only significantly diminishes unit power generation efficiency but also triggers multiple failures in turbine flow components and condensers. In severe cases, it forces units to reduce load or even shut down.
I. Hazards of Vacuum Leakage
1. Significant reduction in unit power generation efficiency and marked increase in steam consumption;
The turbine's power generation capability relies on the enthalpy drop of steam during expansion within the flow path. Higher condenser vacuum and lower back pressure result in greater steam expansion enthalpy drop, enabling more work per unit of steam.
2. Damage to turbine final-stage blades and reduced flow path efficiency;
Vacuum loss elevates steam pressure within the condenser, raising saturated steam temperature. This substantially increases the humidity of turbine exhaust steam. High-velocity wet steam droplets impact final-stage blades, causing water erosion and wear. Severe cases result in pitting, cracks, or even blade fracture.
3. Reduced condenser heat transfer efficiency, creating a vicious cycle;
Once external air enters the condenser, it forms a vapor film on the surface of the cooling water tubes, hindering heat exchange between steam and cooling water. This drastically reduces the condenser's heat transfer coefficient and increases the condenser end difference. The decreased heat transfer efficiency further exacerbates vacuum loss, which in turn raises exhaust steam temperature. This increases the amount of non-condensable gases released within the condenser, creating a vicious cycle: “vacuum loss → worsened heat transfer → further vacuum loss.”
4. Deformation of the low-pressure cylinder and bearing housing, causing excessive unit vibration;
Declining condenser vacuum causes a sharp rise in turbine exhaust temperature (exhaust temperature can surge from the design range of 30–40°C to over 80°C during severe leakage). High-temperature exhaust causes uneven heating and thermal deformation of the low-pressure cylinder shell and bearing housing, leading to rotor center misalignment and disrupting the force balance of the turbine radial bearings and thrust bearings. Rotor center misalignment triggers excessive unit vibration (bearing housing vibration >0.05mm, shaft vibration >0.12mm) while causing steam seal contact with the rotor. This further exacerbates vacuum leakage and vibration, potentially triggering vibration protection shutdown in severe cases.
II. Practical Leak Detection Methods
1. Water Injection Leak Detection: During shutdown, when conditions permit, inject water into the condenser to locate leaks. Repair identified leak points promptly, then repeat the water injection process to verify repairs. This method requires shutdown and cold-state operation. A limitation is incomplete detection—leaks occurring only under expansion pressure cannot be identified via water injection.
2. Pressure Testing: This method operates on a principle similar to water injection. Atmospheric pressure is introduced into the condenser system, and soapy water is applied to all potential leak points. Disadvantages include being time-consuming and labor-intensive. Detection effectiveness is affected by ambient temperature and humidity. Unit shutdown is required.
3. Helium Mass Spectrometer Leak Detection: Connect the spectrometer's analyzer to the vacuum pump end of the condenser. Operate a helium spray gun over all potential leak points while maintaining communication with personnel at the analyzer end. Detection of helium at the analyzer indicates a leak near the spray gun. Repeat the process to pinpoint the vacuum-induced leak. Disadvantages: Nitrogen gas is volatile, making it difficult to reach inaccessible corners. Similar methods include halogen detection.
4. Ultrasonic Leak Detection: Simple and convenient. It doubles the wavelength of ultrasonic waves generated by leaks, reducing the frequency of the leak signal through multiple doubling cycles until it reaches audible levels for human detection. Disadvantages: The frequency reduction process also attenuates other ambient noise frequencies, failing to resolve noise interference issues. Surrounding noise often masks the leakage ultrasonic signal, leading to misidentification of many leak points. This results in incomplete leak detection with frequent omissions and misjudgments.
5. Weak Signal Intelligent Leak Detector: Widely used in power generation systems, this technology employs AI techniques like noise wave pattern recognition to extract, analyze, compare, and pinpoint leak noises. It effectively filters out ambient noise for precise leak detection. Capable of long-distance leak localization, it can operate during shutdowns or while equipment is online. Comprehensive leak detection capability. Suitable for both wet-cooled and air-cooled power plants. Also effective for detecting internal valve leaks that are difficult to detect with other instruments. Simple operation and portable design.
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