The DN750 triple-eccentric butterfly valve can withstand temperatures up to 600 degrees Celsius, but it often experiences internal leakage as well as external leakage at the flanges.
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This post was last edited by haichuan1 Number on 2018-6-20 at 22:30. The valves are entirely imported; I need to check the specific materials and manufacturers and will provide that information later. How does everyone usually handle this situation/? I checked, but couldn’t find information on the material. This is quite troublesome; I hope experts can discuss it and share their experience. I took a look at the guy downstairs; it was obvious he was an expert. There were no cracks, and it was indeed a deformation of the seal. The parameters for this valve were provided by the design institute. If it really is a mistake in selection, that would be problematic, as each valve costs over 1 million, and there are 8 valves in total. Regarding external leaks, I consulted an expert, who suggested using flanges with MFM surfaces. Due to the alternation between hot and cold conditions, care must be taken when selecting the material for the fasteners, and thermal tightening should be performed each time there is a change in temperature.
The cause of internal leakage is that, at high temperatures, the sealing surfaces of the valve seat and valve disc deform, and the metal crystal structure changes, resulting in internal leakage. Cracks are likely to appear in this area later on. Leakage at the flange connection is related to the wall thickness of the valve body and the structural length of the valve body. Overall, it’s likely there was an issue with the valve selection.
This parameter was provided by the design institute during the selection process; now, with all the relevant documents and information no longer available, it’s a real challenge. There are a total of 8 valves. And it’s very important: the temperature drops to room temperature during regeneration, while it can reach 600 degrees Celsius during normal use. It regenerates once every month. The temperature will rise and fall once
If you go to argue with the valve factory, they probably won’t pay any attention to you; all you can do is have your quality guarantee deposit withheld. Let’s think about how to remedy this from a process perspective, in order to prevent explosions caused by the mixing of reaction gas and regeneration gas during regeneration. If the leak is regenerative gas, it can be tolerated if the concentration of flammable gases is low; but if the concentration of flammable gases in the leak is high, then the valve has to be replaced
Personally, I find it hard to come across reliable valves with intermittent regeneration; even those from abroad might not be reliable. To be on the safe side, it is necessary for the valve manufacturer to carry out operational condition simulation tests to check the leakage rate
Personally, I think the requirements set for the design institute are problematic; this leads to deformation of the filler when it is exposed to alternating hot and cold temperatures, and leakage occurs when the temperature changes again
Send me the data sheet from the design institute (with the name of the institute removed) and the drawings from the valve manufacturer (with the manufacturer’s name removed) by email. I’ll help you find out the reason. The email address is 1572022474@qq.com; or 18017856099@163.com; Shen Gong
It would be best to have on-site photos of the valves (from different angles), which would make it more comprehensive. It’s possible to identify where the problem lies and then develop a solution.
There is a problem with the material; the material of the valve components and the sealing filler is inadequate
For valves of 750, factors such as large volume, material strength and structure need to be considered, and thermal tightening is required due to temperature changes. The structure of the valve seal is very important. If there are no cracks in the leakage, it is thermal tightening; thermal tightening bolts require a specific sequence, and they must be checked using a torque wrench.
The maintenance costs for special valves are also high, especially those imported from abroad; experts’ guidance is appreciated