Methods for shutting down a steam turbine
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When shutting down a turbine, should the load be reduced gradually or removed abruptly? And how is it possible to pass through the critical speed range when reducing the load gradually?
If conditions permit, the load and speed should be gradually reduced until they reach the lowest controlled speed. In the event of an emergency that requires an immediate stop, the only option is to press the emergency stop button. As for the critical speed, it is only possible to stop the machine and let it rotate idly to pass through the critical region. It’s just my personal opinion; I’d appreciate some guidance.
Agree with the view from the second floor; try to avoid shutting down the machine abruptly in situations where it’s not an emergency. Pressing the shutdown button after reducing the load to the minimum continuous speed is the correct way to shut down. The first-order critical speed range that Lz is concerned about lies below the lowest continuous operating speed, so there is no need to worry about the load being reduced to below the critical speed.
The shutdown process of a turbine also has requirements regarding speed; generally, whether accelerating or decelerating, the speed at passing through the critical speed should be higher (all of this is specified during program design). The critical speed can easily cause resonance in the unit; by passing through it quickly, the duration of resonance can be minimized, thereby reducing damage to the unit.
I mean, is it possible to reduce the speed below the critical speed before stopping? Judging from your reply, you should stop the car above the critical level
I mean, is it possible to reduce the speed below the critical speed before stopping? Judging from your reply, you should stop the car above the critical level
“I mean, is it possible to reduce the speed below the critical speed before stopping? Based on your reply, it seems you should stop the machine above the critical speed. For the safety of the machinery, its design doesn’t seem to allow for such a situation – the critical speed cannot fall within your operational range
The shutdown process of a turbine is one in which the temperature and pressure are reduced. Therefore, whether it is an industrial turbine or a turbine used in power plants, under normal conditions it is not advisable to bring it to a stop immediately (via emergency shutdown). This is because turbines generally operate under high temperature and pressure conditions; stopping them abruptly would result in excessive braking torque on the turbine unit, as well as overheating of the turbine’s cylinders, rotor, and other components involved in the flow of fluid. It could also lead to excessive temperature differences between the upper and lower cylinders, as well as issues related to thermal expansion (especially in the case of condensing turbines)；
The main steps for shutting down a turbine, from a macro perspective, are: 1) Reduce load； 2) Wet-dry conversion ； 3) When the load is less than 5%, the turbine shuts down ； 4) Destroy the vacuum ； 5) Start the barring gear. Starting and stopping a steam turbine is not complicated; you can think of it in terms of the steam trains from the past to make a comparison.
When shutting down a turbine, the connected machinery usually needs to be stopped as well; this can be divided into normal shutdowns and emergency shutdowns. In an emergency shutdown, the process is stopped immediately, with the quick-shut valves activating. Normal shutdown can be achieved via the PLC; the PLC also controls the speed to decrease gradually, with the critical speed being passed through automatically and rapidly.
These days, model 505 is generally used for stopping automatically, it’s fully automatic; of course you can also do it manually, but it’s more complicated