A flat‑weld flange is commonly referred to as a “flat plate” or a “lap‑weld flange.” To connect a flat‑weld flange to a pipe, first insert the pipe into the flange’s bore until it reaches the proper position, and then perform a lap weld.

Plate Flange

Seal face type: Full-face (FF), Raised-face (RF)

Carbon Steel: ASTM A105, 20#, Q235, 16Mn, ASTM A350 LF1, LF2, CL1/CL2, LF3 CL1/CL2, ASTM A694 F42, F46, F48, F50, F52, F56, F60, F65, F70;

Stainless Steel: ASTM A182 F304, 304L, F316, 316L, 1Cr18Ni9Ti,

0Cr18Ni9Ti, 321, 18-8;

Alloy Steel: ASTM A182 F1, F5a, F9, F11, F12, F22, F91; A182F12; A182F11; 16MnR; Cr5Mo; 12Cr1MoV; 15CrMo; 12Cr2Mo1; A335P22; St45.8/Ⅲ;

Manufacturing standards: HG20593-2009, HG20615-2009, GB/T9119-2000, GB/T2555-81, JB/T81-94, JB/T74-94, JB/T75-94, GB2506-89, CBM1012-81

Connection method: single-sided welding, double-sided nut connection

Manufacturing processes: These include solid‑material forging and semi‑solid forging (less common), which are suitable for slip‑on and weld‑neck flanges; plate‑steel fabrication, which is used for slip‑on flanges; as well as centrifugal casting and cast‑iron flanges.

Manufacturing process: High-precision CNC lathe turning, CNC radial drilling.

Application scope: The advantage of slip‑on flanges is that they are easier to align during welding and assembly, and they are relatively inexpensive, which has led to their widespread use. However, due to their lower rigidity, they should not be used in chemical process piping systems subject to severe vibrations, or in applications involving flammable, explosive, or highly vacuum‑required conditions, nor in situations where the medium poses a high or extreme hazard.

Seal face types: Flat Face (FF), Raised Face (RF), Male-Female (MFM), Tongue-and-Groove (TG), and Ring Joint (RJ).

Carbon Steel: ASTM A105, 10#, 20#, Q235, Q345B, 16Mn, ASTM A350 LF1, LF2 CL1/CL2, LF3 CL1/CL2, ASTM A694 F42, F46, F48, F50, F52, F56, F60, F65, F70

Stainless Steel: ASTM A182 F304, 304L, F316, 316L, 1Cr18Ni9Ti,

0Cr18Ni9Ti, 321, 18-8;

Alloy Steel: ASTM A182 F1, F5a, F9, F11, F12, F22, F91; A182F12; A182F11; 16MnR; Cr5Mo; 12Cr1MoV; 15CrMo; 12Cr2Mo1; A335P22; St45.8/Ⅲ;

Manufacturing standards: GB/T 9118-2000, HG 20599-97, HG 20600-97, HG 20621-97, GB/T 9120-2000, GB/T 9121-2000, JB/T 83-94, JB/T 84-94, GB 10747-89, CB/T 49-1999, CB/T 50-1999.

Connection method: single-sided welding, double-sided bolt-and-nut connection; the flange is rotatable and facilitates precise alignment of bolt holes.

Manufacturing process: integral forging or finished‑product forging and machining.

Manufacturing process: High-precision CNC lathe turning, CNC radial drilling.

Application scope: A loose‑flange is a flange equipped with a loose sleeve, typically used in piping systems. By loosening the bolts, the two pipe sections can be rotated relative to each other and then re‑tightened, allowing for convenient disassembly and assembly of the pipeline. In a loose‑flange connection, the flange is slipped over the pipe end using a collar or steel ring, enabling it to slide along the pipe. The steel ring or collar serves as the sealing surface, while the flange’s function is to compress and secure these components. Consequently, because the steel ring or collar acts as a barrier, the loose‑flange does not come into direct contact with the process medium.