Pipe butt joint issues (imperial pipes and metric pipes)
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I have taken on a project; the equipment manufacturer has completed the design of the equipment, with all the pipe flanges being designed in accordance with the HG/T20615 standard. However, the client requires that the pipes for this project be designed using metric standards, and now we are facing issues related to the connections between these pipes. Could you please advise on how to connect DN500 pipes (with outer diameters of 508mm and 530mm)? Also, can DN1000 pipes (with outer diameters of 1016mm and 1020mm) be directly welded together? By how much should the outer diameters differ for grooving and butt welding to be possible on-site?
This post was last edited by zbfyh on 2016-11-22 at 14:06. It’s not a comparison of inches, but rather different size series. The outer diameter difference is too large; the welding gap between the flange and the steel pipe is too big
The pressure shouldn’t be high, right? 1. Change the execution standard for the equipment’s connection flanges to what the client requires; isn’t the equipment not yet finished manufacturing? 2. Alternatively, a flanged butt weld joint with a neck can be used; when joining the flanges to the pipe, a portion of the flange neck is removed to ensure that the outer diameter of the neck is close to that of the pipe, after which welding is performed.
The equipment has already been manufactured; can a transition fitting be added in between to enable compatibility between the two series of sizes?
I think a transitional paragraph can be added in the middle to connect the two parts; it’s probably because this owner doesn’t understand either that this situation has arisen
Do you mean by the transition section special pipe fittings similar to tees?
Normally, such pairing is not allowed – they are completely different series of pipes and fittings. But everything can be an exception. For the kind of problem mentioned by the original poster, the simplest and most direct solution is to create two flanges, either butt-weld flanges or socket-weld flanges as specified in HG/T20592 (the choice depends on the requirements for the welds; if radiographic testing of the welds is required by the project, then butt-weld flanges should be used, otherwise socket-weld flanges will do). One flange should be made for Series A and the other for Series B; the flanges are welded to both ends of the pipes, and after installing the bolts and gaskets, it’s done. Another option is to use a reducer that matches the wall thickness and outer diameter of both ends – for example, Φ530*508 – and these can be welded directly together. The second method is cheaper. I often recommend these two approaches to clients and handle their fabrication. I hope this helps the original poster
Looking at the best options, it’s indeed best to do it this way
Any pipe fitting factory can do it; just provide them with the dimensions and have a size change weld done