Whether they are used for transportation of liquids or gases, as heat exchangers, or for structural purposes, pipes and tubes are essential to many industries, and, often, they must custom-bent to fulfill necessary structural or design requirements. If you have a project that requires custom pipe bending services, it pays to familiarize yourself with common terms used in the industry so that you can effectively communicate your design requirements and know what to expect.
Here are a few of the terms you should know:
1.5D bends are sharp 90-degree bends in a pipe that make a nearly-perpendicular corner. The bend radius is only 1.5 times the diameter of the pipe itself, and the bends are far less gradual than either of the common 3D or 5D bends.
A 3D bend is a 90-degree bend in a pipe that is relatively gentle. The bend radius is equal to 3 times the diameter of the pipe, which makes it a longer and more gradual bend than a 2D or 1.5D bend, but not quite as gradual as a 5D bend. 3D bends are one of the most common industry-standard bends.
A 5D bend is another common type of bend that is more gradual than either the 1.5 or 3D bends, but sharper than higher-numbered bends, including 6D and above. With a bend radius of 5 times the diameter of the pipe, the smooth bend offers less resistance to the flow of liquids or gas.
Rolled pipe is pipe that has been bent into a long, smooth arc or even a full circle, with both ends still in the same plane. In plumbing applications or building applications, rolled pipe can be used to go around circular objects. It can also be used structurally to create arcs with large load-bearing capabilities, such as for arches over windows or doorways, or for trusses that create the roof structure of a building.
Pipe bent into helical coils, similar to the spiral shape of common springs, is often used in plumbing, refrigeration, distillation and other applications as a heat exchanger. By winding the pipe into a tight helical coil, or a set of coils with one inside the other, the surface area of the pipe can be maximized in a small amount of space. During distillation, for example, water or a mixed fluid is heated to the boiling point of water, and the resulting water vapor is routed through a helical coil located in a cool liquid. As the water vapor passes through the coil, it condenses into pure water, which can then be drained away. Helical coils can be made with bends at a consistent radius, making a uniform cylinder-like coil, or a variable radius, making a tapered coil.
Serpentine coils are often found in refrigeration and HVAC equipment as heat exchangers. They are S-shaped coils of pipe or tube that are often repeated vertically, and in a three-dimensional configuration from front to back. The individual pipes or tubes are often covered with a series of aluminum fins to increase the surface area available for heat exchange further. By increasing the surface area, the refrigeration or HVAC equipment can more efficiently move heat out of the building or refrigerated area.
A davit is lifting arm similar to a crane that is often used on ships to lift cargo over the side, or over cargo holds to lift things in and out. They are also common on pickup trucks to lift heavy parts in and out of the bed and anywhere where a heavy load needs to be moved easily. While many davit arms are constructed of a three-piece system that includes an upright arm, a horizontal arm, and an angled brace between the two, a more-compact davit arm can also be made from a single pipe, bent to a 90-degree angle. It provides the structural integrity of a standard davit arm, without the diagonal brace, which can interfere with the movement of the load.
In press bending, a die is pressed into a section of pipe between two fixed supports, bending the pipe around the die. This is a manual process, and it will deform the pipe into an oval cross-section at the bend.
Rotary Draw Bending
In rotary draw bending, the end of a pipe is clamped to a rotating bend die, which pulls the pipe forward as it turns. The pipe is pushed into the bend die by a pressure die, and an optional wiper die can be used to minimize deformation of the pipe. Many rotary draw benders are computer-controlled CNC machines.
In roll bending, three rollers are used in a triangular shape to gently bend a length of pipe. Typically, either the single top roll is pushed down or the two bottom rolls are pushed up to create pressure on the pipe. This method produces minimum deformation of the pipe, and it can be sued to create either coils of pipe, or long, gentle curves.
Three-Roll Push Bending
In three-roll push bending a set of pressure rollers holds a pipe against a bend die. As the pipe is pushed through the rollers, a third roller moves the pipe closer to or further away from the bend die, controlling the radius of the bend. These are typically computer-controlled machines.
Tube bundles are typically a series of U-shaped pipe sections that are gathered into a single bundle, with all the open ends facing in the same direction, or a set of straight pipes bundled together. They are often used as heat exchangers, and are placed inside large containers of fluid.
Hot bending is a method of bending pipes that uses heat to soften the metal before bending it. This can reduce the amount of force necessary to create the bend and prevent damage to the pipe during the process, depending on they type of material used. Heat is applied using electric induction coils, and the process is often used for larger diameter pipes, such as those used for pipelines or refineries.
Cold bending is any process that bends the pipe without applying heat. Heat can damage or weaken some materials, such as steel, so mechanical bending process are often preferred.
There are many other terms used in the pipe bending industry, but these are some of the ones you will encounter most frequently, as well as a few that are specific to certain applications. By familiarizing yourself with these terms you can get your project off to a good start.