Several Common Connection Methods for PE Water Supply Pipes

There are numerous methods for connecting polyethylene (PE) pipes to other PE pipes, fittings, or metal pipes; each method has its own advantages and limitations. Users can select the appropriate connection method based on factors such as pipe diameter, operating pressure, and the specific application environment. The most common connection methods for municipal PE water supply pipelines include heat fusion, electrofusion, flexible socket-and-spigot connections, flange connections, and steel-to-PE transition fittings.

1. Heat Fusion Connection

Heat fusion involves using specialized heating tools to heat the mating surfaces of PE pipes or fittings under pressure until they melt. The heating tool is then removed, and the two molten surfaces are pressed together and held under steady pressure until the joint cools and solidifies. Heat fusion methods include butt fusion, socket fusion, and saddle fusion.

2. Electrofusion Connection

Electrofusion involves using specialized fittings with embedded resistance wires. These fittings are placed in tight contact with the PE pipe or fitting to be joined, and an electric current is applied. The embedded wires heat the interface, melting the materials together into a single unit until the joint cools. Electrofusion is suitable for connecting PE pipes or spigot fittings of different types and melt flow rates. Electrofusion methods include socket electrofusion and saddle electrofusion.

3. Flexible Socket-and-Spigot Connection

The flexible socket-and-spigot connection for PE pipelines is a method developed based on the principles used for cast iron and PVC-U pipes. It involves welding a reinforced PE socket onto one end of the PE pipe. During installation, the spigot end of the pipe is inserted directly into the specially designed socket. A locking ring within the socket provides pull-out resistance, while a rubber sealing ring ensures a watertight seal, thereby securely connecting the PE pipe and fitting.

4. Flange Connection

Flange connections are primarily used to connect PE pipelines to metal pipes or auxiliary equipment such as valves, flow meters, and pressure gauges. Flange connections primarily consist of polyethylene flange adapters, steel or aluminum backing rings (loose flanges), steel or aluminum flange plates, gaskets or sealing rings, bolts, and nuts. The connection is achieved by tightening the bolts and nuts to bring the flange adapter and flange plate into firm contact.

5. Steel-to-PE transition fitting connection

This method involves using a pre-fabricated steel-to-PE transition fitting—manufactured via cold pressing or other techniques—to join polyethylene piping with metal piping. These fittings contain pull-out resistant locking rings and sealing rings; they are required to provide excellent sealing performance, with pull-out resistance and pressure ratings exceeding those of the polyethylene piping within the system.

The above outlines the connection methods for PE pipes. It is important to note that cutting pipe threads directly onto polyethylene pipes or fittings to create a threaded connection is strictly prohibited, as is using an open flame to heat polyethylene pipes or fittings for direct joining.

Polyethylene joining technology has matured into a highly reliable process. Statistics indicate that the leakage rate for polyethylene pipes is less than 0.002%—far lower than the 2–3% rate observed with ductile iron pipes. This significantly enhances both pipeline safety and economic efficiency, which is a key reason why polyethylene pipes are widely used in gas distribution networks.