PL flange products are a kind of disc-shaped parts, which are more common in pipeline engineering. Flanges are used in pairs. In pipeline engineering, flat welding flanges are mainly used for pipeline connection. In the pipelines that need to be connected, a flange plate is installed in various ways. The low-pressure pipeline can use the wire connection flange, and the welding flange is used for the pressure above 4 kg. A sealing point is added between the two flanges, and then tightened with bolts. Flanges with different pressures have different thicknesses and use different bolts. When water pumps and valves are connected to pipelines, parts of these equipments are also made into corresponding flange shapes, also known as flange connections. All connecting parts that are connected by bolts on the periphery of two planes and are closed at the same time are generally called "flanges", such as the connection of ventilation pipes. This kind of parts can be called "flange parts". But this kind of connection is only a part of the equipment, such as the connection between the flange and the water pump, it is not good to call the water pump "flange parts". Smaller ones, such as valves, can be called "flange parts".

PL flange products are easy to obtain materials, simple to manufacture, low cost, and widely used; but their rigidity is poor, so they must not be used in chemical process piping systems and highly hazardous occasions that require supply and demand, inflammable, explosive, and high vacuum requirements. . The sealing surface types are flat and raised.

PL flange products are suitable for piping systems where the pressure level is relatively low, and the pressure fluctuations, vibrations and shocks are not serious. The advantages of flat welding flanges are that they are easier to align during welding and assembly, and the price is relatively cheap, so they are widely used.

PL flange products connection is an important connection method for pipeline construction. Flange connection is to fix two pipes, pipe fittings or equipment on a flange plate respectively, add flange pads between the two flange plates, and fasten them together with bolts to complete the connection. Some pipe fittings and equipment have their own flanges, which are also flange connections.