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The Gate to Chemical Efficiency: How Gate Valve Suppliers Optimize Flow Control

The Gate to Chemical Efficiency: How Gate Valve Suppliers Optimize Flow Control

Feb 18,2024

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long welding neck flange 1

Long Welding Neck Flange

MstnLand's series of long welding neck flange is also known as long diameter flange, belongs to the American standard flange standard system. It is a form of ANSI flange and an extended form of neck butt welding flange. The flange neck is slightly straight cylindrical, and the neck height is 229mm or 305mm. The flange neck does not need to be processed. The groove can be customized according to the requirements of relevant standards hg20615‐2009 or the requirements of customers. Long welding neck flanges are frequently used in class series pipe flanges. When small‐size flanges or pipe flanges below DN50 are matched with the pipe body, the use of Long welding neck flanges can avoid the difficulty of welding caused by the thin wall thickness of the flange neck.


Body material:

Carbon Steel, Alloy Steel, Stainless Steel

Size range:


Pressure rating:

CLASS 150lb~2500lb

Sealing surface


Applicable medium:

Water, Steam≤1.0MPa, Oil&Gas

Applicable industry:

Chemical & Petrochemical,

Oil & Gas,

Mining & Minerals,

Power generation,

Water & Water treatment,

General industrial,


Heating & Ventilation,

Marine & Offshore,

Pulp & Paper.

Design & Manufacture:



Advantages of long-welding-neck-flange

Long weld neck flanges (also known as LWN) have an extended neck that acts as a boring extension and is longer than a standard weld neck flange. Long weld neck flanges have a beveled flange so that it fits with the pipe for added strength. Long weld neck flange connections improve pipe flow. Additionally, piping systems are safer when reinforced with long weld neck flanges. This kind of flange helps to balance pressure and temperature changes in the liquid that is flowing in the pipeline.

Applications of long-welding-neck-flange

The long welding neck flange is mainly applied to the construction of pressure vessel functioning as a nozzle (such as a thermowell nozzle). To attach a common welding neck flange to a pressure vessel, a piece of pipe is required with additional welding. A LWN flange on the other hand attaches directly to the vessel, hence, it can be viewed as an integrally reinforced nozzle. It avoids making a weld seam at pipe to flange and provides self-reinforcement. Industrial long weld neck flanges are used in high pressure industrial applications and in high temperature situations as well. It's often used in the oil, gas, and petrochemical industries, long neck flanges are also known as nozzles and can be used to replace pipes. 

 Difference between long-welding-neck-flange and slip-on flange

The biggest difference between slip-on flange flange and long welding neck flange on structure in that the difference between joint pipe and connection way of flange. Generally, the slip-on flange is that the joint pipe connected with flange angle, while the butt welding neck flange is that the flange connected with joint pipe. Slip-on flange can only be connected with the pipeline, while not directly connected with pieces of welding neck flange; But welding neck flange can be connected with all pieces of welding neck flange directly, of course, as well as pipeline. 

The welding seam form of slip-on flange pipe and flange is fillet weld while the form of long welding neck flange is girth weld. The flat is two fillet welds, but the butt welding is a butt weld. The difference between the slip-on flange and without neck flange in that the slip-on flange has one more part than the slip-on flange without neck in the pipeline welding position. The slip-on flange without neck is flat flange. 

Slip-on flange nominal pressure is: 0.6---4.0MPa and long welding neck flange nominal pressure is: 1--25MPa. Obviously, the level of neck flange of adaptation to the stress is relatively lower.

The slip-on flange's stiffness is larger than the welding neck flanges. The strength of the former is higher and not easy to leak. Slip-on flange and butt welding neck flange can be not replaced casually. As far as the manufacture is concerned, the slip-on flange has larger diameter, which means low weight and cost.

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