Can the warm-up time specified in the turbine speed-up curve be set arbitrarily by oneself?

Generally, the speed increase is carried out according to the acceleration curve provided by the manufacturer; if vibrations become excessive when passing through the critical point, the warming time can be extended. As for the post cited by forum member “dxh52389” regarding the issue of excessive low-speed warm-up time, this is because: 1. The turbine has no load, so the amount of steam flowing into it is very small; as a result, the heat generated in the exhaust cylinder cannot be fully carried away by the steam, preventing the exhaust chamber from being adequately cooled, and thus causing the exhaust temperature to rise. 2. Due to the small opening degree of the low-speed control valve, the fresh steam is severely throttled. According to the principles of throttling and the properties of steam, the enthalpy of the steam remains unchanged after throttling while its pressure decreases; as a result, the expansion line corresponding to the decrease in steam enthalpy shifts to the right on the enthalpy-entropy diagram ； With a constant exhaust pressure, the end temperature increases, possibly reaching the superheated region; as a result, the exhaust temperature rises. 3. During startup, the vacuum level is generally low while the exhaust pressure is high; as a result, the exhaust temperature also increases. 4. The size increases only near the final blades, resulting in blower friction losses that heat the steam and raise the exhaust temperature. . a3 J- Q Q+ f’ x Hazard: Excessively high exhaust temperature can cause the cylinders to heat up and expand unevenly, leading to a shift in the unit’s center and resulting in vibrations. It can also cause cracks to appear in the flanges of the condenser copper tubes, allowing cooling water to leak out.

In the case of a condensing turbine, the warm-up time at low speeds is long, and the temperature of the rear cylinders is high.

I guess that’s not possible, right? The thermal properties of each machine are different, after all.

Follow the instructions; otherwise, disputes are likely to arise if problems occur. Remember, always trust the guidelines rather than experience

The actual acceleration curve during the unit’s startup refers to the operational guidelines for the period from when the unit begins to accelerate until its speed reaches the lower limit set by the governor. This process is generally divided into cold start and hot start, and the steam turbine manufacturer will certainly provide an accurate acceleration curve. In practical operation, cold start and hot start can generally be determined based on the operating conditions of the unit after it stops, without having to follow strict rules. However, there are a few points to note: first, the speed beyond the critical speed must not be too low ； Secondly, the low-speed warm-up period should not be too short nor too long; this varies depending on the machine ； Third, attention should be paid to changes in axial displacement during startup, as this is easily overlooked

It is true that sufficient warm-up time is necessary, but this does not mean that the longer the warm-up time, the better. When starting from a cold state, a somewhat longer warm-up time generally has little impact on the unit. However, by controlling the warm-up time properly, steam can be saved; an excessively long warm-up time will inevitably lead to unnecessary waste. Moreover, if the steam is not discharged in time, some of it will condense inside the turbine, damaging its blades； During hot start, an excessively long warm-up time can be harmful to the unit; specifically, the cylinder and the moving and stationary parts of the turbine do not heat up evenly, but instead experience cooling-induced contraction. It may also cause hazards such as an increase in exhaust temperature. Therefore, the warm-up time must be determined based on the actual conditions on site; in situations where acceleration is possible, it is generally not advisable to extend the warm-up time. The above is shared by a forum user. I hope you’ll do more searching; there’s a lot of great material available.