What are the causes of negative pressure and fluctuations in the steam leakage from the turbine?
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1. What are the causes of negative pressure and fluctuations in the steam leakage from the turbine? 2. Is the leakage steam pressure slightly positive or 0 under normal conditions?
The leaking steam consists of several components; it’s not clear which one is being monitored. Is there a diagram? Since there is a leak, the pressure cannot be 0. It is reduced significantly by the labyrinth seal, resulting in a slight positive pressure; this pressure is usually diverted as part of the steam used for the steam seal.
It refers to the pressure of the steam leaking from the high and low pressure shaft ends, before it enters the leak steam condenser.
The main reasons for the leakage are that the wear gap of the shaft seal is out of tolerance, as well as an excessively high pressure of the sealing air for the shaft seal.
May I ask, can high shaft seal pressure cause negative pressure that leads to steam leakage?
The amount of steam used for the seal actually amounts to nothing compared to the exhaust volume of the turbine; it is not sufficient to affect the negative pressure in the entire vacuum system. What needs to be dealt with is the leakage from the seal, which must be removed using a seal steam ejector. It is important to check whether there are any issues with the steam supply for this ejector. Additionally, it is possible that there could be errors in the operation of the pipelines related to the turbine’s leakage system, allowing high-pressure steam to enter the ejector, which in turn can cause fluctuations in the negative pressure of the ejector.
There is no misalignment or improper closing of the valves; the process settings are correct, and the steam seal injectors are operating properly. I wonder if it might be because the sealing steam cannot be supplied properly, which leads to air leaking in on the negative pressure side, causing the steam seal pressure to become negative and fluctuate
If that works, you can reduce the valve opening of the steam ejector used for sealing to prevent air leakage; try this to see if air is getting in. Doing so will result in a slight waste of air, but it is beneficial for maintaining negative pressure. Be careful not to close the valve too tightly, as this could force air into the lubrication bearing system and contaminate the oil there.
There are risks in doing this: 1. The area is filled with steam. 2. As you might say, it could contaminate the fuel system. I want to open the sealed steam bypass to increase the amount of sealed steam. Do you think that’s okay?
That little amount of air leakage won’t be much; it might not even be visible in hot weather, and it certainly won’t contaminate the oil. Is external steam being used for the seal? This is only to be used before starting up normally or when stopping; do you think there isn’t enough steam for the seal? The leak collection pipe is located outside the point where the seal steam is introduced; therefore, closing the valve that connects the collection pipe to the seal steam injector will not affect the seal steam. It’s just a waste as the seal steam will be released unnecessarily. Generally, the pressure of the seal steam is around 0.1 MPa, and negative pressure fluctuations caused by the seal steam are not common. Checking the operation of the surface cooler and its vacuum generator could also be a useful approach.
Thank you, 6054. The surface cooler, jet pump, etc. are all functioning normally; the exhaust pressure has increased slightly. When the unit is operating normally, it requires a certain amount of steam for the external seal; would the phenomenon I described occur if this supply is interrupted? Does this indicate that a small amount of air may have entered the system through the shaft seal on the negative pressure side? Please specify, thank you!