To prevent excessive temperature differences within the metal components of the turbine, it is better to have a lower rate of temperature increase during turbine startup. Why is this statement incorrect?
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It is incorrect to say that the lower the temperature rise rate during turbine startup, the better, in order to prevent excessive temperature differences within the turbine’s metal components. Why? :dizzy: Please explain. Is this question wrong just for the sake of ensuring the safe operation of the equipment? What is a suitable temperature rise rate during normal operation? For small units, the temperature rise rate requirement of 1℃ within 2 minutes seems a bit high, doesn’t it? I hope the experts here can help answer this question. Thank you.
If it’s not about design, then one should operate according to the required process conditions. If it’s about design, this requirement should be well-founded. I guess you wouldn’t ask such a question either. If for small units the temperature rise rate is required to be 1℃ within 2 minutes, isn’t that a bit too high of a requirement? ”Then how do you justify it as being “a bit too high”?
I was wrong; what I meant was, is it too long if the temperature rise rate is less than 1 degree Celsius every two minutes? I see that a general temperature rise rate of less than 2-2.5 degrees Celsius per minute is sufficient. Is it necessary to keep the temperature rise rate below 1 degree Celsius every two minutes? Please help answer it, thank you.
Is there anyone who can explain this? ? ?
Less than 2℃ per minute; I’m curious about how this heating rate should be controlled. I’d like to learn more about it
In practice, it’s quite difficult to control this so-called heating rate. The rate is faster at the beginning when heat is supplied using latent heat, but it slows down as the temperature of the unit rises and heating is then carried out using the sensible heat of steam. Therefore, there’s no need to worry too much about this heating rate; it’s merely a reference value. It is recommended to buy a few related books and read more of them.
Learn about hot start: during a hot start, the temperature inside the turbine is high; for a cold start, the temperature rise rate can be controlled at around seven degrees per minute
During hot start, the temperature at the center of the rotor is higher than that on its surface; to reduce the temperature difference between the rotor’s surface and its interior during startup, the rate of temperature increase is set to be somewhat higher
In my opinion, it isn’t the case that the heating rate of the turbine should be as low as possible; it is generally advisable to keep it between 50–100°C per hour (we usually set it at 50–60°C). A too rapid heating rate can lead to uneven thermal expansion of various components, resulting in issues such as friction or sticking during startup. On the other hand, if the heating rate is too slow, the components will expand sufficiently, but the unit will need to be rotated for a long time during the preheating process. Whether this rotation occurs continuously at low speeds or intermittently, it can cause damage to the bearing surfaces of the unit.
The turbines used in Hangzhou Automobile factories require a temperature rise of 50°C per hour. A lower temperature rise means less flow of steam used for warming up the turbines, which in turn increases the water content in the steam. It is also necessary to drain water from the main steam pipes simultaneously; this can lead to an increased temperature difference between the upper and lower casings of the turbine. Therefore, it is very important to carry out operations that ensure a proper temperature rise as required.
Temperature rise is controlled by the steam valve opening during warm-up