Problems with steam turbine compressors
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New ammonia synthesis plants generally are equipped with steam turbine compressors. On the turbine side, shaft end seals are usually supplied with instrument air that has been reduced to a very low pressure via pressure regulators; in my workshop, this pressure is reduced to 2 KPA. There is one issue: if the pressure regulator fails and the pressure rises to around 30 KPA, what effects might this have on the turbine? Is it harmful? Could it cause oil to be forced out? Please feel free to discuss this or offer your insights
We all use low-pressure steam for sealing. If air is used for sealing, aren’t we worried that air might leak into the vacuum system and disrupt the vacuum?
Yes, the original poster returned a steam turbine; we also use steam after pressure reduction for sealing!
What the original poster said is not accurate; it shouldn’t be called gas used for shaft end sealing. This term generally refers to the seals at both ends of a steam turbine, which are used to prevent steam from leaking out of the turbine and cold air from entering it. These seals are usually labyrinth seals, and the medium used is steam, rather than the mechanical seals mentioned by the person in the second floor comment. What the poster is referring to is likely the sealed air on the side of the bearing box; its purpose is to prevent steam from entering the bearing box and causing the lubricating oil to become contaminated with water. Purified air is usually used for this purpose, and the structure involved is similar to a labyrinth seal with comb-like teeth. Short-term high air pressure doesn’t pose much risk, but the effects over a longer period are unknown.
It should still be repaired as soon as possible; otherwise, steam might enter the bearing box and contaminate the lubricating oil with water
Regarding the turbine in the unit mentioned by the original poster, it depends on what type of turbine it is. If it is a fully condensed turbine, the sealing gas used at the high-pressure end and the low-pressure end is different. Sealing gas can be used at the high-pressure end to prevent steam from entering the bearing housing, whereas the low-pressure end is under vacuum, so sealing gas cannot be used there. The turbine is sealed at both ends with comb teeth, allowing a certain amount of leakage; the sealing gas is used merely to prevent steam from entering the bearing housing. Some people upstairs suggested using steam as the sealing gas, but some were not clear about this; if steam is used as the sealing gas, wouldn’t it make it easy for external steam to enter the bearing box?
What the poster is referring to is likely the oil seal of the compressor’s bearing housing, which prevents air from entering and thus slows down premature aging.
Agreed! The shaft seal of a turbine allows a slight amount of sealing steam to leak out, which is necessary to ensure its effectiveness. However, to prevent this sealing steam from reaching the bearings, a labyrinth seal is installed in front of the bearings, with nitrogen being used as an additional barrier. Although instrument air requires a high level of dryness, it is still not as good as nitrogen; both types of pipelines are present here, but they have not been put into use yet. The pressure of the instrument air must not be too high; generally, the lubricating oil pressure is reduced through throttle plates before it reaches the bearings. After this reduction, in the case of units manufactured by Hangzhou Steam Engine and Shenyang Turbine, the oil pressure is usually between 0.5 and 1 kilogram.
What the original poster is referring to is the isolation gas for the compressor; 30 kp is acceptable as well, and it won’t have a significant impact on the compressor. Our isolation gas pressure is indeed 30 kp. What you’re talking about is the sealing at both ends of the turbine – we use medium-pressure steam for sealing, but there is also some buffer gas, which is nitrogen at a pressure of 2 kp. If the pressure is too high, the oil waxes will definitely be blown out.
We also use low-pressure steam, and we have pressure relief valves – are they broken? I never thought of it! It seems there’s another safety vent at the back. Right, there is a safe way to vent it~~
11# Shadow King: It’s fine to have a bit more pressure; what matters most is the size of the openings in your gas seal. If the opening is large, 30 KPA definitely won’t work; the gas will ruin the seal completely. It is recommended that you not use pressure regulators; a small globe valve with a DN15 diameter will suffice. The air flow can be adjusted on-site, and when it’s time to put the system into use, simply open the main air supply valve – it’s very convenient. I modified my unit in this way, and it has been in use for over a decade; I’ve never had any concerns regarding the isolation gas.