A plate flange (PL flange or flat flange) is a flat, circular forged component featuring a central bore and a ring of bolt holes. It can be simply slipped over the pipe and welded on both sides to achieve a secure seal—no raised face or neck is required; only a single flat flange is needed, making installation straightforward and cost-effective. Note: Plate flanges are perforated and used for connecting pipelines; blind flanges (BL) are solid and serve to shut off fluid flow. Use a PL flange when connection is required, and a BL flange when isolation is needed.

Socket-weld flanges (SW flanges) provide a smooth, high-strength connection without the need for threaded joints or full-penetration welds. The pipe is inserted into the socket until it abuts the shoulder, then backed out by 1/16 inch to allow for thermal expansion and contraction, after which a fillet weld is applied on the outside. The static strength of SW flanges is comparable to that of other types, while their fatigue life is improved by approximately 50%, making them particularly suitable for piping systems subject to frequent pressure or temperature fluctuations.

Weld-neck flanges are a widely used connection method in the industrial sector, particularly in piping, valves, equipment, and machinery.

A blind flange (BL flange, blank flange) is simply a solid circular disc with bolt holes. It has no bore and no raised face—just a forged flat plate that is bolted between two flanges to shut off fluid flow, isolate a pipeline, or provide an access port for pressure testing. Because it is initially manufactured as a forged blind flange blank, with grain flow extending through the entire thickness, its pressure rating is fully compatible with the corresponding weld-neck or slip-on flange—except that, in this case, fluid flow has been completely stopped.

Socket-weld flanges (SW flanges) provide a smooth, high-strength connection without the need for threaded joints or full-penetration welds. The pipe is inserted into the socket until it abuts the shoulder, then backed out by 1/16 inch to allow for thermal expansion and contraction, after which a fillet weld is applied on the outside. The static strength of SW flanges is comparable to that of other types, while their fatigue life is improved by approximately 50%, making them particularly suitable for piping systems subject to frequent pressure or temperature fluctuations.

The figure-eight blind flange lives up to its name: a solid disc and an annular ring are joined by a short stub flange. When bolted between two flanges and then rotated 180°, the pipeline is either fully open or completely sealed. There’s no need for a valve seat that could leak, nor for monthly gasket replacements—just a single forged component that can remain in the piping system for a lifetime.

A loose flange is a type of flange that is slip-on and movable at the pipe end (a loose-type flange). It achieves rotational flexibility and easy alignment through flanging or the use of a steel ring, and is commonly used in piping applications involving corrosive media, low pressure (typically ≤1.6 MPa), and frequent disassembly.

A plate flange (PL flange or flat flange) is a flat, circular forged component featuring a central bore and a ring of bolt holes. It can be simply slipped over the pipe and welded on both sides to achieve a secure seal—no raised face or neck is required; only a single flat flange is needed, making installation straightforward and cost-effective. Note: Plate flanges are perforated and used for connecting pipelines; blind flanges (BL) are solid and serve to shut off fluid flow. Use a PL flange when connection is required, and a BL flange when isolation is needed.

Threaded flanges (threaded flanges, Th flanges) feature female NPT threads in their bore. Simply screw the pipe into the flange, install a gasket, and tighten with bolts to achieve a leak-tight seal—no welding or hot work is required, making them particularly suitable for small-diameter piping or hazardous plant areas. As this connection method is mechanical, threaded flanges are the preferred choice for explosive atmospheres, cryogenic discharge lines, and any application where sparks could lead to severe consequences.

When pipe sizes exceed the load capacity of the workbench, you need large-diameter flanges. These flanges are forged from solid billets, with grain flow and pressure ratings identical to those of smaller flanges—except that the bolt-hole circle diameter is specified in meters rather than millimeters. Whether referred to as large-bore flanges, A-series necked weld-end flanges, or B-series blind flanges, their function remains consistent: to connect NPS 26 to 60 pipes without reducing the pressure rating.

The tube sheet flange is a critical pressure-bearing component used in pressure vessels such as heat exchangers, boilers, and condensers to secure the tube bundle and to isolate the shell-side and tube-side fluids. It typically consists of a precisely machined circular plate with numerous tube holes. The outer periphery of the flange is equipped with a standard flange sealing surface and bolt holes for connection to the vessel shell or other pipeline flanges.

In the industrial sector, the long-neck flange is a critical connection device widely used for joining pipelines, valves, pumps, and other equipment. Its distinctive advantages—such as high load-carrying capacity and excellent sealing performance—make it an indispensable component across numerous industrial applications. This article provides a detailed overview of the long-neck flange.