05,Nov 2024
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At some point, you’ve probably wished you could order one long, unbroken piece of pipe to make your plumbing project a breeze. Of course, that’s just plain impossible!
In reality, pipes come in different lengths and shapes, and you will need pipe joints to connect them at various points to create a functional piping network. But with so many types of pipe joints available, how do you know which one to choose?
This article will walk you through the different types to help you find the best fit for your project.
We’ve divided these types of pipe joints into two main categories:
A threaded joint typically features a pipe with external threads (male) that fit into another pipe with internal threads (female). It works very well for low-pressure systems, such as water supply lines and natural gas pipelines (you’ve likely seen one in your own home).
Common materials for threaded joints include brass, stainless steel, and cast iron.
Installing threaded joints is as simple as disassembling, which makes them easy to maintain.
However, you must keep in mind these things during installation:
Brazed joints involve melting a filler metal at above 840°F to join together the ends of two pipes (usually copper pipes). The joint may have a slightly raised bead where the brazing material is visible. You often find them in HVAC systems and refrigeration lines.
While it does provide a clean, finished look on the joint, you’ll need someone skilled enough to ensure a reliable connection. This makes brazed joints less accessible for DIY applications.
Much like a brazed joint, a soldered joint appears as a smooth, rounded connection where the pipes meet. The only difference is that soldering utilizes filler metal that melts below 840°F [1].
That explains why this joint type is preferred for applications involving delicate components, such as electronics or thin-walled tubing, as it helps preserve the original properties of the base materials.
Moreover, soldered joints are not ideal for high-pressure, high-temperature applications as these environments can weaken the solder, and consequently, the pipe joint.
Butt welded joints involve two pipe (beveled) ends aligned and welded together edge-to-edge throughout the pipe circumference, resulting in a smooth surface that allows uninterrupted fluid flow.
This is suited for high-volume, high-speed flow systems like those you find in petrochemical and water treatment settings.
Butt welded joints are commonly used with carbon steel, stainless steel, and alloy pipes due to their strength, corrosion resistance, and heat tolerance.
That said, precise pipe alignment and skillful welding are necessary to get the most out of this joint type’s potential.
Socket welded joints are commonly seen in small-bore piping, typically in systems under 2 inches in diameter. Generally, this joint type is more reliable than threaded ends where the risk of leaking is higher.
Here, the pipe end is inserted into another pipe with a socket end, and the outer edge is then welded to secure it.
The design allows for a strong bond that holds the pipe firmly, and the small internal gap left between the pipe end and the bottom of the socket helps absorb thermal expansion.
A flanged joint has two matching, flat circular rings with bolt holes around the perimeter, known as flanges, which are attached to the pipe ends. These flanges are then bolted together with a gasket between them to ensure a tight, leak-proof seal.
No matter the type of flange, bolted connections can be easily dismantled when necessary, allowing for simple disassembly of the pipe connections. This feature makes regular cleaning, inspection, and repairs much more convenient without disturbing the rest of the pipeline.
As a result, pipe flange joints are commonly used in large piping systems, such as those in oil refineries, chemical plants, and water treatment facilities.
The main drawback, however, is that flanged joints typically require more space for installation.
A grooved joint features a pipe end with a pre-cut groove. A rubber gasket wraps around the joint, and a two-piece metal clamp (also called a coupling) is placed over the gasket, aligning with the grooves on each pipe.
This setup allows one to securely connect pipes much faster compared to welded or flanged joints. You can often find them in fire protection systems, HVAC installations, and large commercial plumbing.
The downside? Grooved joints may not handle as much pressure as welded or flanged connections. Additionally, you should pay attention to the gasket’s quality and alignment. If the gasket wears out or isn’t seated correctly, the joint can leak.
A compression joint is commonly used in residential plumbing and gas applications. It’s favored for connecting copper, plastic, or metal pipes without the need for welding or soldering.
In terms of appearance, compression joints consist of a compression ring or ferrule that fits snugly over the pipe and a brass or plastic nut that tightens to create a seal. This design allows for quick installation and easy disassembly if maintenance is needed.
To ensure a leak-proof connection, it’s vital to avoid over-tightening the nut. Instead, tighten it just enough to create a seal, and check for leaks by applying water pressure and inspecting the joint.
A socket or coupler joint is commonly used to extend the length of a piping run. For instance, when renovating a kitchen or bathroom, you may need to extend the length of piping to accommodate new sinks or appliances that are farther from existing plumbing.
Appearance-wise, a socket joint looks like a short, hollow cylinder that matches the outer diameter of the pipe. The end of the pipe is inserted into the socket, allowing for a snug fit. When installed, it creates a seamless transition between the two pipe sections.
Common materials used for socket joints include:
A disadvantage that comes with this type of pipe joint is the difficulty in disassembling it. Once glued or soldered, you’ll need to cut the pipe to remove the joint, making repairs less convenient.
A nipple joint is essentially a short length of pipe, about a few inches long, with male threads on both ends, allowing it to connect directly to two female-threaded fittings or pipes. The threads can have a tapered design for a tighter seal or a straight one.
This joint type is often used where a short length of pipe is needed to connect two larger sections, such as in water supply lines or HVAC systems.
Brass is often used for water supply systems due to its resistance to corrosion and longevity, while galvanized steel is popular for industrial applications.
While it’s highly versatile, one drawback of nipple joints is that it reduces the flow area of the pipe. The internal diameter of the nipple is often smaller than that of the connected pipes, which can create restrictions in fluid flow and potentially lead to pressure drops.
The spigot and socket joint is used in underground installations where soil shifting or settling can occur, such as drainages and sewers. It’s often made from materials like PVC, cast iron, and concrete.
It features one pipe with a tapered end (the spigot) that fits into the larger, flared end of another pipe (the socket). When assembled, the joint appears as a continuous length of pipe with a smooth transition at the connection point.
While the process is simple – just fully push the spigot into the socket – this step is essential, as an incomplete connection can lead to leaks. For PVC pipes, applying a suitable solvent cement around the joint can further secure the connection and create a watertight seal.
Expansion joints are ideal for systems that experience a lot of temperature shifts. They’re built to handle expansion and contraction in pipes, particularly in steam, gas and hot water applications.
Unlike the joints discussed earlier, expansion joints have a flexible section – usually a set of metal bellows – that can compress or stretch as the pipe expands and contracts. They are typically constructed from stainless steel or carbon steel, which effectively reduces thermal stress on the pipes.
On the downside, expansion joints can wear out over time due to constant stretching and compressing, so they need to be inspected regularly.
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