Understanding Large Diameter Slip-On Flanges

Large diameter slip-on flanges are industrial fittings used to connect pipes through welding, and are widely used in industries such as chemical, construction, water supply and heating, petroleum, and power. The following is a summary of key points regarding large diameter slip-on flanges:

Features

Structure: Slip-on flanges are connected to pipes using fillet welds, and are divided into plate slip-on flanges (PL) and slip-on flanges with a neck (SO). Compared to weld neck flanges, slip-on flanges have a simpler structure and use less material, but their rigidity and sealing performance are slightly inferior.

Rigidity: The rigidity is poor, suitable for pipeline systems with pressure ratings ≤ 4.0 MPa and where pressure fluctuations or vibrations are not severe.

Sealing Surface: Common sealing surface types include:

Flat Face (FF): Suitable for low-pressure, non-toxic media applications.

Raised Face (RF): Suitable for slightly higher pressure applications.

Male and Female (MFM): Suitable for flammable, explosive, or higher pressure applications.

Material: Includes carbon steel (such as 20#, Q235, A105), stainless steel (such as 304, 316), alloy steel (such as 15CrMo, 16Mn), etc., which are corrosion-resistant and have high compressive strength.

Specifications: Diameter range from DN10 to DN6000, pressure ratings covering PN0.25 to PN25.

Manufacturing Process

Forging: Suitable for flanges of conventional sizes, ensuring material density.

Rolling: Used for ultra-large size flanges, formed through multiple rolling processes.

Production standards include national standards (GB/T9119), chemical industry standards (HG20593-2009, HG20615-2009), and mechanical department standards (JB/T81-94), etc.

Advantages

Easy Installation: Easy to center during welding, simple assembly.

Low Cost: Simple to manufacture, cheaper than weld neck flanges.

Wide Application: Suitable for medium and low pressure pipeline systems, such as metallurgy, machinery, chemical, shipbuilding, etc.

Disadvantages

Insufficient Rigidity: Not suitable for high pressure or high temperature environments.

Weaker Sealing: Compared to weld neck flanges, the sealing performance is slightly worse.

Application Scenarios

Large diameter slip-on flanges are widely used in pipeline systems with lower pressure, non-toxic media, or where vibrations are not severe, such as water supply, drainage, petroleum, light and heavy industry, fire protection, and shipbuilding.

Differences from Weld Neck Flanges

Structure: Slip-on flanges have no neck or a short neck, and the welding is a fillet weld; weld neck flanges have a high neck and use butt welding, with a bevel angle usually of 45°.

Scope of Application: Slip-on flanges are suitable for medium and low pressure environments; weld neck flanges are suitable for high pressure, high temperature, or highly fluctuating pipelines.