Classification by Structural Form
Double-Socket Couplings: Includes equal-diameter and reducing double-socket couplings (with the latter further categorized into concentric and eccentric types); used for connecting two pipe ends of the same or different diameters.
Directional Fittings: Includes 45° and 90° double-socket elbows; used to change the direction of the pipeline, featuring socket connections at both ends.
Branching Fittings: Includes equal-diameter and reducing double-socket tees as well as double-socket crosses; used to create branch lines from a main pipeline, featuring socket connections at two or more ends.
Transition/Adapter Fittings: Such as adapters for connecting new and old pipes; supports double-socket connections between pipes of different specifications, commonly used in ductile iron pipe renovation projects.
Classification by Sealing Method
Socket-Weld Type: The pipe is inserted directly into the double-socket opening and sealed by welding; offers high pressure resistance and is commonly used in high-pressure industrial applications such as petrochemicals and power generation.
Rubber Ring Seal Type: Uses a sliding rubber ring to achieve a flexible seal; offers convenient installation and accommodates slight pipeline settlement, commonly used in municipal water supply and drainage projects.
Flexible-Elastic Double-Fusion Type: Designed for thermoplastic materials like PPR; achieves a sealed double-socket connection via a heat-fusion process, suitable for low-pressure residential piping systems.