Pump seal leakage issue
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There is a multi-stage pump with a power rating of 132 KW, and the fluid it handles is liquefied gas. A strong odor of liquefied gas could be detected at the machine seal, but no frost was visible anywhere. If you want to replace the mechanical seal, you’ll need to replace two sets of them; since it’s only a minor leak, it doesn’t seem worth it. The blacksmith said that it would be enough to blow on it with steam; I’m not sure if this method will work. I’d like to ask the experts here if there are any other alternatives. It’s urgent; thanks to everyone in advance!
Due to the low temperature of the liquefied gas, when the pump starts, the sealing ring inside the mechanical seal (made of PTFE) cannot expand fully to provide a proper seal, which results in leaks. You will find that the pump no longer leaks after it has been running for some time; this is because the sealing ring has now functioned properly. Therefore, the pump can be preheated with steam at the time of startup； Additionally, if the sealing ring inside the mechanical seal is a V-shaped PTFE ring with high hardness, it can be replaced with a Viton rubber one
The original poster posted the same thread on two forums, so I gave the same reply to both: the mechanical seal of liquefied gas pumps is the hardest to deal with! Firstly, when selecting the mechanical seal for liquefied gas pumps, it is important to note that double-end seals should be used as much as possible, with silicon carbide-graphite combinations for the dynamic and static rings, and rapid cooling should be employed for the mechanical seal! This issue actually requires taking into account the management style of your company and what the standards for leaks are! How are maintenance costs and environmental safety taken into account! Because in your post, there are two words I don’t understand: “very strong” and “slightly leaking”! If the leakage is not severe, it is recommended to keep an eye on it; if it increases, maintenance is necessary! In fact, maintenance does not necessarily require replacing the mechanical seal; otherwise, mechanics would just be tasked with part replacement. Minor leaks in machinery can sometimes be caused by damage to the mechanical surfaces, damaged gaskets, or issues related to the compression level! :lol :lol :lol
What is the explosion protection rating of the area where your pump is located? If it cannot be disclosed, I still think the 02+53 flushing scheme is better; as for the specific values of a, b, and c, it depends on your pressure. What do you mean by blowing with steam? Blast the already vaporized medium outside? Should I blow inside instead? I’m not quite sure what you mean. If it is designed for steam quenching and purging, it should be able to meet your on-site conditions as well. I’m a novice; I need someone more experienced to make the judgment. :lol
I think it’s necessary to clean the mechanical seal; if small issues aren’t resolved, they can turn into big problems
This kind of problem is quite difficult to handle; we encounter this issue again when installing machine seals. I agree with the view from the second floor – the method used by the fitter is appropriate. If that still doesn’t suffice, then disassembly and inspection will be necessary.
On the 19th, two sets of CM130A-75 machine seals manufactured in Sichuan were replaced; however, there was little improvement after the replacement – the situation remained more or less the same as before. Our combustible gas concentration must not exceed 20PPM; if it does, the combustible gas alarm will start sounding erratically. The fitter said to use steam for blowing; I think that’s the right approach – blow steam at the seal gland, but not let it enter inside the seal, so as to prevent the components related to the seal from expanding. Components such as the seal gland, gaskets, and O-rings can expand, and I believe this will reduce the gaps between the moving ring and the stationary ring of the seal, as well as between the moving ring and the shaft sleeve, and between the stationary ring and the shaft sleeve. There’s nothing to do about it; the machine seals need to be replaced again next week. I heard that a set of machine seals costs 1,000 dollars. My heart is agitated, but there’s nothing I can do. It still needs to be changed! I took a close look; the air coming out of the seal area had a smell of liquefied gas, though not very strong. One point: It’s definitely the mechanical seal that’s leaking. Point two: There is a problem with the auxiliary seal. For other possible scenarios, I hope everyone can offer more suggestions! Thank you here!
Your method has been tried, but there’s still some leakage! I didn’t even fold it
By the way, when the fitter removed it, I saw that the shaft sleeve of the mechanical seal was worn out; the shaft sleeve became hot and had tightened around the shaft. The bearings are also slightly damaged. I’ve thought about it for a long time – this has nothing to do with the leakage
The bushings are completely seized; that means the pressure ratio of your mechanical seal is too high. The bearing is slightly damaged; the shaft vibrates excessively, which causes some leakage. It is recommended to replace the bearings, shaft sleeves, static and dynamic ring seals, and adjust the specific pressure of the mechanical seal spring to 1/3. OK
I agree with the opinion from the 3rd floor. The material of the mechanical seal is very important. Also, during installation it’s necessary to ensure proper leveling, and the two friction surfaces should experience even pressure when in contact.