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Long Wellneck and Heavy Barrel Flanges

Long weld neck flange (LWN flange) is also call integral flange, it means a welding neck flange has a very long neck. Commonly, the welding neck flange has a tapered neck and a bevel end which is going to butt welding with the matching pipe. But the long weld neck flange, has a straight short pipe as the neck of a long weld neck flange. Long weld neck flange (LWN flange), is used for high pressure situations, integral hub weld neck flanges are used and for very high pressure cases Long Welding Neck flanges are preferred. In this case, the weld are far from the ring to avoid bending stresses and weld stress being combined.

The Long Weld Neck Flanges are the best designed butt-welded flange of those currently available becuase of its inherent structural value. It is expensive because of the design. 

Long welding neck flange, lwn flanges are similar to a standard Welding Neck flanges, but the “Neck” is considerably longer than other flanges. LWN flange is often used as a nozzle for a barrel or column. In addition, there are the type LWN Heavy Barrel (HB) and the Equal LWN Barrel (E); they have a different shape and a thicker “Wall”.

The long weld neck flange should be butt welded with the pipes, it means the neck dimensions is same with the matching pipe, same diameter and wall thickness , commonly the long weld has a plain end, not a bevel end for welding . Except the neck, the LWN flange has a same dimensions with the welding neck flange. In addition, there are also the type LWN Heavy Barrel (HB) and the Equal LWN Barrel (E); they have a different shape and a thicker “Wall” which name is Nozzle.

Tube OD sizes: 3/8 to 2 inches

The Long Weld Neck Flange is normally referred to as the high hub flange. It is designed to transfer stresses to the pipe, thereby reducing high stress concentrations at the base of the flange.

The Long Weld Neck Flange is the best designed butt-welded flange of those currently available becuase of its inherent structural value. It is expensive because of the design.

Carbon steel: A105,SS400,SF440 RST37.2,S235JRG2,P250GH,C22.8 
Stainless Steel: F304 F304L F316 F316L 316Ti, Copper etc.

Elastomer seal: >=1 x 10^-8 Torr – High vacuum 
EVAC metal seal: >=1 x 10^-11 Torr – UHV

  • Viton: -20°C to 200°C
  • Silicone: -50°C to 230°C
  • Buna: -30°C to 110°C
  • EVAC metal seal: -270°C to 150°C

LWN flanges are largely used in the petroleum and chemical industries but can also be used in residential and commercial buildings where fluctuating temperatures and high stress are expected, such as a main water or gas source. Long neck steel flanges are used under conditions where line or pipe expansion creates bending or repeated changes in the pipe. Because a long neck flange is used in pressurized applications, the flange may have additional pressure connections and may be referred to as an orifice flange. The flange supports free product flow when bored to match the diameter of the pipe it will receive. Long weld neck flanges are attached using V-shaped welds known as butt welds.

  • Long Weld Neck – Raised Face
    • Flange – Long Weld Neck, ANSI Class 150, B16.5 (in)
    • Flange – Long Weld Neck, ANSI Class 300, B16.5 (in)
    • Flange – Long Weld Neck, ANSI Class 400, B16.5 (in)
    • Flange – Long Weld Neck, ANSI Class 600, B16.5 (in)
    • Flange – Long Weld Neck, ANSI Class 900, B16.5 (in)
    • Flange – Long Weld Neck, ANSI Class 1500, B16.5 (in)
    • Flange – Long Weld Neck, ANSI Class 2500, B16.5 (in)
  • Heavy Barrel – Raised Face
    • Flange – Heavy Barrel, ANSI Class 150, B16.5 (in)

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