How are non-metallic pipes connected to metal valves?
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I would like to ask the experts here: our current rainwater pipes are steel-reinforced polyethylene spiral-wound pipes with a diameter of DN1000. We now need to connect a DN700 metal valve to them, and I’m not sure how to do that
It’s better to use flange connections; as long as the strength is sufficient, that should work
Metal valves can be connected using non-metallic flanges. However, it should be noted that the sealing surface of the connection flange must be a full plane; otherwise, the insufficient strength of the non-metallic flange may cause deformation of the flange, leading to leaks. Therefore, the sealing surface of the metal valve chosen by the poster should also be a full flat surface. If the mating flanges of a metal valve are convex, then a metal gasket must be placed between the two flanges to prevent leakage. I have a question for the original poster: since it’s a rainwater pipeline and the diameter of the pipes is so large, the pressure within the pipeline system should be low. Then why are metal valves chosen for connection?
The poster should be aware that one is DN1000 and the other is DN700; they are connected using flanges, but it is advisable to use an adapter pipe for transition
Reply to 3# haichuan_enbo: Thank you for your suggestion. Since there is little pressure in the rainwater drainage pipes, what kind of valve should be chosen then? I don’t quite understand; I’m just starting out with this.
Valves of this size are very expensive; even cast-iron valves. Why choose a valve when direct flange connection would suffice? The valve selection is as follows: atmospheric pressure valve, cast iron material, butterfly valve, full-plane sealing, hard-sealed surface
Reply to 6# wcj7140: Your drainage pipe should be called a \"steel belt reinforced polyethylene spiral corrugated pipe\". This type of pipe is used for pressure-free drainage, and it cannot be connected using flanges, as flanges cannot be welded to drainage pipes. Drain pipes generally use wells to achieve functions such as turning, without the need for valves. The drain pipe can easily get clogged with dirt and other debris, preventing the valve from closing. Please consider carefully.
Reply to 7# — Lantian — This is a rainwater switching valve; it was designed in this way by the design institute. It is a valve designed for the discharge from our factory area to the overall discharge outlet of the park.
Reply to 8# tqg317: I checked the material list – it shows HDPE plastic-steel spiral-wound drainage pipes, and the valves are electric two-way hard-sealed rotary ball valves. We have four discharge points into the park, with a valve chamber at each discharge point; that’s how the design agency specified it. Now I’m not sure how to make the connections. Do you mean to replace one of the chambers with a steel pipe before connecting the valves?
Generally, the connection of the valve is converted through an anti-corrosion inspection well. I have worked on many drainage pipes, and it’s usually that way; design institutes also design them in that manner.