There are so many ways to connect pipes; do you know which ones?

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Pipelines often require different connection methods depending on the application and material properties. PPR pipes are connected using heat fusion, which is characterized by its simplicity and speed of operation, as well as the use of minimal tools. Furthermore, since binding at the molecular level can be achieved, very reliable connections can be easily obtained as long as the required procedures are followed. So what are some other common connection methods? What are the characteristics of various connection methods? 1. Flange connection: A flange connection is a detachable type of joint in which two pipes, fittings, or components are first fixed to separate flanges, a flange gasket is placed between the two flanges, and then bolts are used to tighten the flanges together so as to bond them firmly. The main advantages of flange connections are easy disassembly, high strength, and good sealing performance. When installing the flanges, it is required that the two flanges remain parallel, their sealing surfaces must not be damaged, and they need to be cleaned thoroughly. Flange gaskets should be selected in accordance with the design specifications. Flange connections are often used for pipes with larger diameters. They are typically applied at the connections of valves, check valves, water meters, water pumps, etc., on main pipelines, as well as in sections of pipes that need to be frequently disassembled and maintained. 2. Welded metal pipes are often connected using welding. Welding is a manufacturing process and technology for joining metals by means of heating, high temperature, or high pressure. The common methods include: fusion welding – where the workpieces to be joined are heated to cause local melting and the formation of a molten pool; fillers may be added if necessary, and the joints are formed once the molten pool cools and solidifies. Pressure welding – the welding process requires applying pressure to the welded parts. Soldering – involves using a metal material with a melting point lower than that of the base material as the solder. The liquid solder wets the base material, fills the gaps in the joint, and diffuses into the base material to join the components together. Welding is suitable for metal pipes and is commonly used for concealed pipes and pipes with larger diameters. When the pipe diameter is less than 22 mm, socket welding or sleeve welding is recommended; the socket should be installed in the direction of the flow of the medium. When the pipe diameter is 22 mm or more, end-to-end welding is preferred. The biggest problem with welding is the risk of corrosion; the weld joint tends to rust over time. Welding quality is highly dependent on welding techniques, and it is difficult to maintain stable control over the quality of pipe connections. 3. Compression connection: Compression connections are commonly used for joining thin-walled pipes. It uses a radial compressive force (hydraulic clamps) to clamp the fitting onto the pipe, and an O-ring is used to prevent water leakage, thereby achieving a secure connection. A similar principle is also found in ring compression connections. Clamped connections are easy to install, but they are more suitable for exposed pipes in cold water systems and direct drinking water systems. Because it is rather troublesome to replace the sealing ring inside the tube when it wears out. The use of hot water systems should be avoided as much as possible, since the thermal expansion and contraction properties of sealing rings and metal materials differ, and sealing rings age more easily due to exposure to heat and cold cycles. Therefore, this type of pipe connection is generally not recommended for concealed piping and hot water systems. 4. Threaded connection: This type of connection is achieved by tightening two fittings that have male and female tapered pipe threads together; the connection is secured through pressure sealing at the threads of these fittings. It is widely used in traditional galvanized steel pipes. Threaded connections are suitable for galvanized steel pipes with a diameter of 100 mm or less, and are commonly used for exposed piping. Since the threads of threaded connections often damage the surface of the galvanized layer, it easily leads to corrosion of the pipes. 5. Socket connection: This type of connection is mainly used for cast iron pipes, concrete pipes, ceramic pipes, plastic pipes, etc., that have socket joints. It comes in two forms: flexible connections and rigid connections. A rigid socket connection is achieved by inserting the socket of one pipe into the socket of another pipe; after alignment, the gap is filled with sealing material and then sealed with an additional sealing agent. For rigid connections, asbestos cement or expandable fillers are used for sealing, while lead can be employed in critical applications to create a secure, airtight unit. In flexible socket connections, an elastic rubber ring is placed over the sealing surface of the pipe socket, and then force is applied to insert the end of the pipe, thereby creating a sealed tube that can accommodate displacement and vibration within a certain range. 6. Groove connection: Also known as clamp connection, this type of connection can be used to join galvanized steel pipes with a diameter of 100 mm or more in systems such as fire protection water, air conditioning hot and cold water, potable water, and rainwater systems. It features simple operation, no impact on the original properties of the pipelines, safe construction, good system stability, easy maintenance, and cost savings in terms of labor and time. 7. Hot melt bonding: This is the method used for connecting PPR pipes during hot melt joining. It involves using heat to raise the melting point of the PPR joints, thereby causing them to melt, and then the pipes and fittings are combined together using a socket-and-spigot technique. Hot-melt bonding is a reliable permanent connection; once the hot-melting process is completed, leaks are almost never occurring. It is precisely because of this reliable connection that PPR pipes have found wide application. 8. Electrofusion joining: Electrofusion joining is generally a method used for welding PE pipes. By applying electric current to the copper wire embedded in the inner wall of the fitting to generate heat, a phase change occurs in the plastic resin in the fusion zone; under certain pressure, the polymer chain segments interpenetrate each other and strengthen their bonds. Upon cooling, the material recrystallizes and arranges itself, thereby bonding the fused areas together into a single unit. Compared to electrofusion welding, the quality of thermofusion welding can be directly reflected by the amount of flanging and skinning. The welding strength and stability are relatively high, and the quality of the welded pipelines can be essentially ensured by inspecting the welds. Capacitive welding involves joining two pipe ends by melting the material inside an electric melting sleeve. Due to the covering provided by this sleeve, it is not possible to determine the quality of the weld from the outside; instead, it is only possible to assess whether the welding process is complete by observing the length of the protrusion from the indicator post. The quality of the weld can be verified on the pipes only through pressure testing.