What is the difference between butt joint, flange joint, and weld joint?
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There are many ways to connect valves, such as clamp connection, flange connection, and butt welding connection. The main difference might be that at slightly higher pressures, flange or weld connections are chosen; so at 45 bar and 425 degrees Celsius, using a flange connection should be fine, right? Personally, I don’t think it’s necessary to use butt welding.
Whether it is or not, it can be applied either way – it depends on cost-effectiveness? Regarding butt-welded valves, are there any standards for the face-to-face dimensions?
At 45 bar and 425 degrees Celsius, flange connection is absolutely no problem – feel free to use it! Butt welding connections are primarily used to prevent highly toxic substances from leaking at the sealing points; in most cases, flange connections are sufficient
The original poster’s question is very confusing. Clamped types are commonly used in disc valves. Due to the structural characteristics of disc valves, their length and other dimensions are relatively small; therefore, this type is often employed in applications with low pressures. The valve itself does not have flanges, and it is held in place by two matching flanges placed on either side, with elongated bolts being used for fastening. For some highly toxic and dangerous media, welded valves are often used; these valves are welded directly to the pipes without any flanges. A butt-weld flange is one in which the flange end features a platform or a short neck; welding the pipe to this area provides good strength, making it suitable for media or applications with high requirements.
Search this forum for standards or books on flanges, and you will quickly find the answer.
Flange connections are fine, but care should be taken with the selection due to the high temperatures involved.
Firstly, using flanges for connections is no problem. Secondly, I once read in a book that it is better to use welding when it is possible to do so, as welding not only reduces costs compared to flange connections but also provides better sealing; after all, even the best combination of gaskets used with flanges can still be a potential point of leakage. Therefore, welding should be preferred in installations, except in those cases where regulations require it, or when connecting valves, equipment, instruments, etc., for which flanges are necessary. Although I personally think this statement is too strict, it’s still useful to take it into consideration~
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It depends on the medium you are using.
Have you seen heat transfer oil pipelines designed by foreigners, where the temperature and pressure might be slightly lower than those in your systems, and where all the valves used are butt-welded valves? Of course, flanged valves are generally used domestically.
At 45 bar and 425 degrees Celsius, flange connection is used; the flange surfaces should have RJ sealing surfaces. When welding is employed, it is preferred to use this method. All the heat transfer oil valves in our factory are of the welded type