8 Kinds of Pipe Connection

Posted on: April 22, 2021 by Madison Pipe Industry, 5 min read

According to the situation and material characteristics of the pipe, different connection methods are often needed. The connection of PPR pipe adopts the hot melt method, which is characterized by simple and quick operation and simple tools. Because the binding of molecular level can be achieved, it is easy to obtain a very reliable connection as long as it is operated as required. So what are the common ways to connect? What are the characteristics of different connection modes?

1. Flange Connection

Flange connection is a detachable joint that holds two pipes, fittings or equipment on one flange plate, then adds flange gasket between two flange plates. And finally uses bolts to tighten the two flange plates to make them tightly combined.

Flange Connection

The main characteristics of flange connection are convenient disassembly, high strength and good sealing performance. When installing flange, two flanges shall be parallel and sealing surface of flange shall not be damaged and cleaned. Flange gasket shall be selected according to the design regulations. The larger diameter pipes are often use flange connection to connect. Flange connection is generally used in the main road connection valves, check valves, water meters, water pumps, etc., And the pipe sections that need to be disassembled and repaired frequently.

2. Welding

Metal pipes are often connected by welding. Welding is a manufacturing process and technology for joining metal by heating, high temperature or high pressure. There are usually several ways:

  • Fusion Welding - Heating the work piece to be joined to make the local melting into a molten pool. If necessary, the filler can be added to assist, and the pool will be joined after cooling and solidification.
  • Pressure Welding - The welding process must apply pressure to the weldment.
  • Brazing - The solder is made of metal material with lower melting point than the base metal. The base metal is wetted with liquid solder. The joint gap is filled. And the joint is diffused with the parent metal to realize the link weldment.


Welding is suitable for metal pipes. It's mostly for concealed pipes and larger diameter pipes. When the pipe diameter is less than 22mm, socket or sleeve welding shall be adopted, and the socket shall be installed in the direction of medium flow. When the pipe diameter is greater than or equal to 22mm, butt welding shall be adopted. The biggest problem of welding is the risk of corrosion, the welding joints are easy to rust in the long-term use. The welding quality depends on welding technology. So the quality of pipe connection is difficult to be controlled stably.

3. Compression Connection

The compression type connection is common used in the thin-walled pipe connection. The pipe fittings are clamped on the pipe by radial contraction external force (hydraulic clamp), and sealed by O-ring to achieve the connection effect. Similar principles also have ring pressure connection.

Compression Connection

The clamp type connection is easy to install. And it is suitable for the open pipe of cold water system and direct drinking water system. Because it is difficult to replace the sealing ring when the seal ring in the pipe is aging. The hot water system should be avoided as far as possible, because the thermal expansion and contraction properties of sealing ring and metal material are different, and the sealing ring is more likely to aging after cold and hot cycle. Therefore the pipe with this connection mode is not recommended for concealed pipeline and hot water system.

4. Threaded Connection

The thread connection adopts the way of tightening two connecting parts with the internal and external interfaces of the conical pipe thread. The connection effect is achieved through the pressure seal of the thread of the connection port. It is widely used in traditional galvanized steel pipes.

Threaded Connection

Threaded connection is suitable for galvanized steel pipe with diameter less than or equal to 100mm. It is mostly used for open-ended pipe. Because thread often damages the surface of galvanized layer, it is easy to cause corrosion of pipeline.

5. Socket Connection

Socket connection is mainly used for cast iron pipe, concrete pipe, ceramic pipe, plastic pipe with socket joint. It has two types: flexible connection and rigid connection.

Socket Connection

Rigid socket connection is to insert the pipe socket into the pipe socket. And then use the caulking material to seal the joint after alignment, later seal with sealing material. The rigid connection is sealed with asbestos cement or expansive filler. Lead seal can be used in important occasions to make it a solid closed whole.

Flexible socket joint is put into elastic rubber ring on the stop seal of pipe socket. And then the pipe plug end is inserted by force to form a closed pipe which can adapt to displacement and vibration within a certain range.

6. Groove Connection

Groove type connection is also called clamp connection. It can be used for the connection of galvanized steel pipes with the diameter of 100mm or more in fire water, air conditioning, hot water, water supply and rainwater systems. It has the characteristics of simple operation, no impact on the original characteristics of the pipeline, construction safety, good system stability, convenient maintenance, labor saving and time saving.

Groove Connection

7. Hot Melt Bonding

Hot melt bonding is the pipe connection method adopted by PPR pipe. It uses heating method to make the PPR joint reach the melting point and melt. In the use of socket method, the pipe and pipe fittings are fused together.

Hot Melt Bonding

Hot melt connection is a kind of permanent connection with strong reliability. Once the hot melt is completed, there will be no leakage accident. PPR pipeline is precisely because of this reliable connection, this connect way has been widely used.

8. Electric Fusion Connection

Electric Fusion connection is generally a kind of connection method used in fusion PE pipe. By heating the copper wire embedded in the inner wall of the pipe, the plastic resin in the fusion zone will change phase. And the polymer chain segments penetrate each other under certain pressure and cross strong. The melting parts will be combined into a whole by recrystallization of cooling materials.

Electric Fusion Connection

Compared with the electric welding, the quality of hot melt welding can be directly expressed by flanging and peeling. The welding strength and stability of hot melt welding are relatively high, and the quality of the welding pipeline can be basically guaranteed by checking the welding joint. The electric fusion welding is connected with the internal melting of the electric melting sleeve to connect the two pipe ports. Because of the wrapping of the electric melting sleeve, the quality of the welding interface cannot be directly seen from the appearance. Whether the welding process is completed or not, it's only indirectly to judge by the length of the observation hole indicating column. And the quality inspection of the welding interface is only adjust by pressure test.

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