Turbine seal air issue!
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Turbine seal air issue! We all know that turbines have shaft seal steam as well as seal gas. What is the function of this seal gas?
I’m not sure if the sealed gas you’re referring to is that nitrogen gas; generally, this gas is located outside the oil seal and also uses a serrated seal design. In my understanding, it serves as a secondary seal for the oil seal, aimed at preventing leaks that might occur even if the primary oil seal isn’t perfect. This nitrogen gas is used to provide an additional layer of sealing to stop oil from entering the machine. I’ve seen seals that were removed and covered in oil, which shows that oil seals aren’t completely reliable. Personal understanding
We’re using a single supply of instrument air; it doesn’t matter much in normal situations, as no one adjusts it, and it’s practically the same as having none at all!
So this is meant as a precaution, it’s not absolute; I’ve seen many turbines that don’t have it
We never used it at all; the oil seal is in good condition, so why waste wind?
1. Prevent air from entering the oxidation equipment; 2. Affect the vacuum level; 3. Ensure effective utilization of steam
Come to learn*. . . . . . . . .
The turbine is equipped with shaft seal nitrogen and shaft seal steam; the nitrogen prevents the shaft seal steam from coming into contact with the oil, thereby avoiding damage to the oil quality. The shaft seal steam on the high-pressure side prevents steam from escaping inside the cylinder, while the low-pressure side prevents air from entering and affecting the vacuum level!
Is instrument air generally used as the sealing air for turbines? It mainly prevents lubricating oil from contaminating the labyrinth seal, as well as stops steam from entering the oil system; it also helps to maintain the quality of the oil and ensures the appropriate temperature of the return oil and the bearing surfaces.
It is primarily to prevent steam from entering the bearing system, especially at the high-pressure end. Strictly speaking, nitrogen is the better choice, as at the high-pressure end, not only can steam penetrate into the bearing housing, but lubricating oil or leaks from the control actuators of the engine head may also occur; such substances can come into direct contact with the highly heated components of the casing and then catch fire. Also, it’s not very good for the air to be in direct contact with it. The shaft seal steam requirements depend on the type of unit, but its purpose is to prevent air from entering the unit’s vacuum system. The pressure is generally not very high, and a certain level of leakage is allowed; some of the steam that leaks out is recovered, while in other cases it is simply discharged.
The shaft seal steam is medium-pressure steam; it leaks into the machine at the high-pressure end, reaches the balance section, and then exits to the vent. In the low-vacuum section of the machine, pressurized steam enters the machine through the shaft seal and is discharged outward, thereby serving as a shaft seal. The sealing gas can be instrument air or nitrogen; nitrogen is preferred. Its function is to isolate steam from the oil that supports the bearings. Some of the nitrogen enters the bearing oil system, while another portion is vented along with the sealing steam from the shaft seal. It can be said that nitrogen can enter the oil system, but steam is not allowed to enter it.