What aspects should be given special attention to prevent rotor bending during hot start-up?
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In addition to taking measures to prevent rotor bending before starting up in a hot state, the following tasks must also be carried out: (1) Before initiating a hot start, the team responsible for the operation should be aware of the conditions during the previous shutdown, any abnormalities that occurred, and the issues that need attention; these details should be explained to each operator so that everyone is well-informed. (2) Before starting the machine in hot condition, the rotor must be rotated continuously for more than 4 hours, with the rotor’s vibration measured to be no more than 0.02 mm of the original value. (3) The shaft seal steam must be supplied first before evacuating the vacuum. (4) All pipes and manifolds should be more thoroughly heated. (5) Strict requirements are placed on the startup parameters and the opening degree of the bypass (the bypass should be opened only when the condenser has a certain level of vacuum). The main steam temperature must be 80–100°C higher than the temperature of the high-pressure inner cylinder, with a superheat of over 50°C. During startup and under load, monitoring of the main and reheat steam temperatures should also be intensified; the steam temperatures must not fluctuate up and down. (6) Strengthen the monitoring of vibrations. During hot start-up, vibrations can occur easily due to temperature differences among various components, and stricter monitoring is required at this time. If the vibration exceeds the specified value, the machine should be stopped immediately by shutting off the power. (7) During startup, hydrophobicity of various components should be enhanced. (8) Extreme hot-start conditions should be avoided as much as possible. (9) Before hot startup, the control system should be degassed, as air remaining in the control system may cause the control valves to move significantly during start-up, leading to unstable boiler parameters and steam containing water. (10) An overspeed test cannot be conducted during extreme hot start. (11) During hot start-up, the load should be increased as quickly as possible to the level corresponding to the cylinder temperature.
First, check whether the temperature of the control stage is above 150 degrees Celsius; then supply the shaft seal steam first, and subsequently activate the vacuum system! The exact opposite of the cold state!
Installing the vacuum system first can easily draw in cold air, causing cooling-induced deformation on one side of the bearing!
Thank you :) I see that when starting the turbine here, after the warm-up phase is complete, extraction air and shaft seal air are supplied right away. Is that okay?
In addition to taking measures to prevent rotor bending before starting up in a hot state, the following steps should also be taken: (1) Before initiating a hot start, the team responsible for the operation should be aware of the conditions during the previous shutdown, any abnormalities that occurred, and the issues that need attention. These details should be explained to each operator so that everyone is well-informed. (2) Vacuum must be created after supplying the shaft seal steam first; the spare steam source should be used for the shaft seal steam, and no cooling water shall be introduced. Before supplying the shaft seal steam, close the exhaust valves for stages 4, 5, and 6 of the steam seal. (3) All pipes and manifolds should be heated more thoroughly. (4) Strict requirements are placed on the startup parameters and the opening degree of the bypass (the bypass should be opened only when the condenser has a certain level of vacuum); the main steam temperature must be at least 50°C higher than the temperature of the high-pressure inner cylinder, with a superheat of 80–100°C. During startup and under load, monitoring of the main and reheat steam temperatures should also be intensified; the steam temperatures must not fluctuate up and down. (5) Strengthen the monitoring of vibrations. During hot start-up, vibrations can occur easily due to temperature differences among various components, and stricter monitoring is required at this time. If the vibration exceeds the specified value, the machine should be stopped immediately; the rotor’s fluctuation should be no more than 0.02 mm of the original value. (6) During startup, hydrophobicity of all components should be enhanced. (7) Extreme hot-start conditions (cylinder temperature above 400°C) should be avoided as much as possible. (8) Before hot start, the control system should be depressurized of air, as air remaining in the control system may cause the control valves to move significantly during startup, leading to unstable boiler parameters and steam containing water. (9) It is best not to conduct an overspeed test during extremely hot start conditions. (10) During hot start, as long as the operations can keep up, the load should be increased as quickly as possible to the level corresponding to the cylinder temperature.
In cold state, evacuate first, then supply shaft seal steam