From the course: AutoCAD Civil 3D: Pressure Pipe Design

Understanding pressure systems - AutoCAD Civil 3D Tutorial

From the course: AutoCAD Civil 3D: Pressure Pipe Design

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Understanding pressure systems

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- [Instructor] Before we dive into pressure pipe design, let's talk a little bit about the nature of pressure systems. Now when we're talking about pressure systems, we're typically talking about water lines. But there are other types of design that they can be used for as well like sewer force mains or gas lines or really the transfer of any liquid or gas that's under pressure. So why does it matter that they're under pressure? Well, if you compare that to gravity piped design, when you're designing a storm system or a sewer system that relays on gravity for the contents of the pipes to flow, then you have to worry about slope. So for example, if we were talking about a gravity system, you can see how the pipes in this profile have no slope at all. They're completely flat. This wouldn't work for a gravity system. But because it's pressure, we don't need to worry about the slopes of the pipes. In fact, if we looked at this profile above here, we see pipes sloping uphill in this case. We're actually flowing, if you look at the plan view, we're flowing uphill possibly to this building. And that's totally okay because it's the pressure that's moving the fluid in the pipes and not gravity. So that, in one major way, simplifies pressure pipe design. We don't have to worry about the slopes of the pipes. And that can make life easier. But we're trading that off for some difficulty. And if we look a little more closely at this layout, we see that it's composed of pipes and bends. And you'll notice that the angles are called out, 22 and a half in this case. 22 and a half here. There's a 90 degree, actually a T here that's at a 90 degree bend angle. Here we've got a 90 degree bend angle. So why are we calling out the bend angles? Why is that important? We don't see that with gravity design. We can just connect a bunch of pipes to a manhole. We don't have to worry about the angles. Well, when you're laying out a pressure system, those bend angle fittings come in industry standard sizes. And that has to be considered as we're laying out this pressure network. We can't just bend the pipes at any old angle. We have to do it in specific angular increments. So that makes the design a bit more challenging in that area. And it requires the software to provide special tools to deal with bend angles. And special objects to deal with bend angles. So you'll find in Civil 3D, that the gravity tools are completely separate from the pressure tools. The things that must be considered, the workflow, the way it's done, it's quite a bit different than gravity design. And that's because of the different design requirements. Of gravity, we need to worry about slope, not so much angle. With pressure, it's the opposite. Slope doesn't matter so much but we really need to be careful with bend angles. And there are some other difference as well. But those are the main ones. Okay, so now we've discussed some general information about pressure pipe systems. And we're ready to start talking about how Civil 3D handles their design.

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