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  • Writer's pictureHill and Griffith

Prestressed Concrete Cylinder Water Pipe Comparison to Bar Wrapped Water Pipe

This video was produced to show how to select a large diameter water transmission main product, by Steve Smith (Pipe Industry Icon)

Hello, my name is Steve Smith and I'm with Forterra Pressure Pipe. What I want to talk to you about today is two pipe products. Prestressed concrete cylinder pipe, which is we're looking at right here. Prestressed concrete cylinder pipe, what you see here is you can see the prestressing wire. This is six gauge wire, class three. It's got a tensile range of 252,000 to 282,000. You'll notice that the spacing between the wires, that term today is called the pitch, the pitch of the wire, means the space in between rod wrap to rod wrap. For instance, this looks like it could be a one inch pitch. You'll notice the mortar coating. The mortar coating is one inch over top of the cylinder. Okay. What we're gonna transition to now, I want to show you the difference between the prestressed pipe and what known as the bar wrap pipe.

This is bar wrap pipe. To the naked eye, one might say they look exactly the same. But you're gonna notice this is rod. It's not prestressing wire, it's rod. Wrapped at about 500 psi, and which it's got a heavy steel cylinder, which differs from the prestressed concrete cylinder pipe, which only has a 16 gauge cylinder.

Bar wrap pipe is rated typically zero all the way up to 250 psi.

The key difference is bar wrap pipe is a semi-rigid design. Semi-flexible if you will, versus prestress, which is a rigid design. So bar wrap pipe does rely on soil side support, much more important than say prestress. What this demonstrates here is the ability to be able to chip out the mortar coating.

Take the rod wraps and basically cut them and bend them out of your way, and this shows the application where we can actually weld a flange in the field.

What makes bar wrap unique, unlike prestress, is prestress, because of the wire wraps, you basically can't cut this pipe and make any modifications, because the wire is under tension. Where versus this pipe, because the rod is not under tension, this is a steel pipe design, it gives you the ability to cut section, this type of bar wrap pipe. If we go to the other side, I'll show you some other examples.

What you're looking at here is bar wrap pipe. Notice the rod. What this demonstrates is the ability to take say a 20 foot section of bar wrap pipe, you can literally cut the pipe in half. What you see here, we take the rod wraps and just peel a couple rods back, and what this shows the ability to weld a flange in the field, with the butt strap. That's something, quite frankly, that you could not do with the prestress concrete sonar pipe.

So when it comes to adaptability and repair ability in the field, bar wrap has become a favorite choice here in these. This just demonstrates a harness clamp joint. This is a harness style joint that's been around for many, many years. This is one form of restraint joint. If we go back over here to the left, obviously this demonstrates our snap ring joint. This is snap ring joint. It's a joint, it was a Price Brothers design joint back in the early '70s, 1973. And it's joint ring we still use today.

We jump to the other side, you can see this is the insert. It basically allows the contractor to push the spigot into the bell. You simply tighten down, loosen a nut and tighten down this bolt. And the term we use, now the snap ring is engaged, means it's locked down. That you can see in this cut out section, because it's smaller diameter, how it locks in the spigot ring and keep it from backing out under thrust conditions.

(Thanks to Steve for the great video. Another thing to remember is that any concrete form release used for potable water needs to be NSF approved, like Grifcote LV-50 Plus.)


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