Protection of industrial drive turbines during shutdown
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What types of protection are required for industrial traction turbines during shutdown? The more detailed, the better! ! Thank you! ! !
There are three methods: hot air protection； Dry air protection ； Nitrogen protection.
During shutdown periods, it is necessary to ensure that the relative humidity inside the cylinder remains below 50.3%. There are three methods available for preventing corrosion in turbines during shutdown: the dry air protection method, the nitrogen protection method, and the hot air protection method.
1. Dry Air Protection Method: This method involves drying the ambient air using a rotating drying wheel before blowing it into the turbine to reduce the relative humidity of the air inside the cylinder. Since this rotating drying wheel is filled with moisture-absorbing materials, the air exiting the wheel has low humidity and high temperature. Even after absorbing moisture from within the cylinder and being cooled by the turbine components, its temperature remains below the level required to prevent corrosion. Therefore, the dry air protection method can effectively prevent corrosion of turbine components.
2. Nitrogen Protection Method: This method involves filling the cylinder with nitrogen to reduce the relative humidity of the air inside. It has been proven to be an effective method, second only to hot air protection and dry air protection. Two points should be noted when using this method: A) The turbine must be dry and sealed before nitrogen is introduced; B) After the cylinder is filled with nitrogen, an overpressure of 0.5–1 bar should be maintained.
3. Hot Air Protection Method: This is a commonly used protection method. The principle behind hot air protection, as well as its practical application, will be discussed in detail below. Relative humidity is defined as the ratio of the actual amount of water vapor present in moist air to the maximum amount of water vapor that can be contained at the same temperature. The formula for calculating relative humidity is: RH = (p_v / p_sat) × 100%, where RH represents relative humidity, p_v represents the partial pressure of water vapor at a certain temperature, and p_sat represents the maximum partial pressure of water vapor at that temperature, i.e., the partial pressure under saturated air conditions. From this formula, it can be seen that relative humidity ranges between 0% and 100%. The lower the value, the further the moist air is from a saturated state, meaning it has the ability to absorb more water vapor – in other words, the air is drier and its ability to absorb water vapor is greater. Conversely, the higher the value, the weaker the ability to absorb water vapor, meaning the air is wetter. Simply heating or cooling moist air results in no change in the amount of moisture present. During heating, the temperature of the moist air increases while the amount of moisture remains constant, resulting in a decrease in relative humidity. Conversely, relative humidity increases. For example, if the air temperature is 30°C and the relative humidity is 60%, then when the air is heated to 40°C, the relative humidity becomes lower. By referring to the saturation tables for 30°C and 40°C, we find that p_v at 30°C is 42.41 hPa and at 40°C it is 73.75 hPa. Thus, the relative humidity at 40°C is: RH = 60% × 42.41 / 73.75 ≈ 34.5%. This shows that heating is an effective way to reduce the relative humidity of air. To prevent corrosion in shut-down turbines, this principle can be utilized to reduce the relative humidity inside the turbine to 40% or even lower. Therefore, hot air should be blown into the turbine to absorb the moist air inside and to heat the cold components above the ambient temperature. Hot air can also be blown from the lowest point of the turbine and allowed to escape through the shaft seal and drain ports. To ensure that all turbine components remain at a temperature higher than the ambient temperature and that the air inside the cylinder does not drop below the dew point, the heating temperature of the moist air should be 8–10°C higher than the temperature of the air in the machine room. Additionally, a pressure of 21993/4 bar gauge pressure should be maintained. This ensures that the relative humidity inside the turbine remains low during shutdown, keeping the turbine in a state with the lowest possible corrosion rate. As shown in Figure 3, the process of introducing hot air involves using a fan or blower to move the air, followed by heating it using a heater. The hot air is then blown into the cylinder from the lowest point, with continuous adjustment of both the temperature and pressure of the hot air.
1. Dry Air Protection Method: This method involves drying the ambient air using a rotating drying wheel before blowing it into the turbine to reduce the relative humidity of the air inside the cylinder. Since this rotating drying wheel is filled with moisture-absorbing materials, the air exiting the wheel has low humidity and high temperature. Even after absorbing moisture from within the cylinder and being cooled by the turbine components, its temperature remains below the level required to prevent corrosion. Therefore, the dry air protection method can effectively prevent corrosion of turbine components.
2. Nitrogen Protection Method: This method involves filling the cylinder with nitrogen to reduce the relative humidity of the air inside. It has been proven to be an effective method, second only to hot air protection and dry air protection. Two points should be noted when using this method: A) The turbine must be dry and sealed before nitrogen is introduced; B) After the cylinder is filled with nitrogen, an overpressure of 0.5–1 bar should be maintained.
3. Hot Air Protection Method: This is a commonly used protection method. The principle behind hot air protection, as well as its practical application, will be discussed in detail below. Relative humidity is defined as the ratio of the actual amount of water vapor present in moist air to the maximum amount of water vapor that can be contained at the same temperature. The formula for calculating relative humidity is: RH = (p_v / p_sat) × 100%, where RH represents relative humidity, p_v represents the partial pressure of water vapor at a certain temperature, and p_sat represents the maximum partial pressure of water vapor at that temperature, i.e., the partial pressure under saturated air conditions. From this formula, it can be seen that relative humidity ranges between 0% and 100%. The lower the value, the further the moist air is from a saturated state, meaning it has the ability to absorb more water vapor – in other words, the air is drier and its ability to absorb water vapor is greater. Conversely, the higher the value, the weaker the ability to absorb water vapor, meaning the air is wetter. Simply heating or cooling moist air results in no change in the amount of moisture present. During heating, the temperature of the moist air increases while the amount of moisture remains constant, resulting in a decrease in relative humidity. Conversely, relative humidity increases. For example, if the air temperature is 30°C and the relative humidity is 60%, then when the air is heated to 40°C, the relative humidity becomes lower. By referring to the saturation tables for 30°C and 40°C, we find that p_v at 30°C is 42.41 hPa and at 40°C it is 73.75 hPa. Thus, the relative humidity at 40°C is: RH = 60% × 42.41 / 73.75 ≈ 34.5%. This shows that heating is an effective way to reduce the relative humidity of air. To prevent corrosion in shut-down turbines, this principle can be utilized to reduce the relative humidity inside the turbine to 40% or even lower. Therefore, hot air should be blown into the turbine to absorb the moist air inside and to heat the cold components above the ambient temperature. Hot air can also be blown from the lowest point of the turbine and allowed to escape through the shaft seal and drain ports. To ensure that all turbine components remain at a temperature higher than the ambient temperature and that the air inside the cylinder does not drop below the dew point, the heating temperature of the moist air should be 8–10°C higher than the temperature of the air in the machine room. Additionally, a pressure of 21993/4 bar gauge pressure should be maintained. This ensures that the relative humidity inside the turbine remains low during shutdown, keeping the turbine in a state with the lowest possible corrosion rate. As shown in Figure 3, the process of introducing hot air involves using a fan or blower to move the air, followed by heating it using a heater. The hot air is then blown into the cylinder from the lowest point, with continuous adjustment of both the temperature and pressure of the hot air.
It depends on how long you stop