Stainless Steel Flange Types Explained: Selection Guide for Slip-On, Weld Neck & Lap Joint

Introduction: Flanges — The Core of Dismountable Pipe Connections
Flanges are the most widely used dismountable connection method in piping systems — two flange faces clamped together by bolts with a gasket compressed between them. Wherever pipe sections must be opened for inspection, cleaning, or component replacement, flanged connections are essential. Wenqiang Stainless Steel supplies slip-on, weld neck, lap joint, socket-weld, and blind flanges in complete ranges.

Flange Type Selection Matrix
Slip-On (SO) Flange: Fillet welded to pipe. Suitable for ≤2.5 MPa, ≤300°C. Most economical for general process piping.
Weld Neck (WN) Flange: Butt-welded to pipe with integral tapered hub. Suitable for ≤25 MPa, ≤600°C. Best choice for high-temperature, high-pressure, and cyclic service.
Lap Joint (LJ) Flange: Loose ring over stub end. Suitable for ≤4 MPa, ≤400°C. Enables easy bolt-hole alignment and frequent disassembly.

Socket-Weld (SW) Flange: For small-bore high-pressure piping ≤DN50.
Blind (BL) Flange: Solid plate for pipe-end closure at any pressure/temperature.
Wenqiang's Standard Coverage
Wenqiang flanges comply with GB/T 9119, HG/T 20592, ASME B16.5, EN 1092-1, and JIS B2220. Pressure classes: Class 150 through Class 2500 (PN6-PN420). Materials: 304/304L/316/316L/321/317L/2205. Sealing face types: Raised Face (RF), Flat Face (FF), Ring Type Joint (RTJ), and Tongue & Groove (TG).

Frequently Asked Questions
Q1: How do you select the flange face type?
A: RF (Raised Face) is most common for medium/low pressure. RTJ (Ring Type Joint) is used for high-temperature, high-pressure (Class 600+). FF (Flat Face) matches cast iron equipment. TG (Tongue & Groove) is used for toxic media and vacuum service.
Q2: Can stainless steel flanges use carbon steel bolts?
A: Not recommended. Use matching stainless steel bolts (A2-70 or A4-70) to prevent galvanic corrosion and galling. If carbon steel bolts must be used, install insulating gaskets and sleeves.
Q3: Can Wenqiang provide third-party inspection certificates?
A: Yes. Wenqiang flanges can be supplied with EN 10204 3.1 MTCs, SGS/TÜV/BV third-party test reports, and PED 2014/68/EU pressure equipment compliance documentation.

Contact Us
Wenqiang Stainless Steel flanges — complete range, reliable quality. Class 150 to Class 2500, one-stop supply. Inquiries: +86 577 8922 2595.