Welding Neck Flanges

Why Choose Us

Factory Strength

Shanghai KEK Pipeline Technology Co., Ltd. is a reputable AAA listed pipe fittings manufacturer in China, covering an area of 66666㎡ (80000+㎡ in Phase II), with more than 30 technicians and engineers.

Our Certifications

KEK has obtained ISO9001, ISO14001, ISO18001, CE/PED, API certification and TS pressure pipe component special equipment manufacturing license, as well as Russia's EAC continuous certification.

Advanced Equipment

It has a full set of the largest and most advanced equipment in China, including a 4000-ton hydraulic press and a 3000-ton three-way cold extrusion molding machine.

Product Traceability

Product traceability, all products are numbered and indexed by furnace number, production process number, and RT inspection number to ensure the unique traceability of the product.

What is Welding Neck Flanges

A weld neck flange has a long tapered hub that transitions smoothly to the pipe or fitting it is welded to. It is typically butt-welded to the line, meaning the end is inserted into the flange and then welded around the circumference. This creates a strong and leak-proof joint. The hub also reinforces the flange, making it less susceptible to distortion or damage.Weld neck flanges are commonly used in applications where strength and integrity are paramount. This includes petrochemical, oil and gas, and power generation industries. They are also available in various materials — including carbon, stainless, and alloy steel — to handle different requirements.

Stainless Steel Weld Neck Flange
Product Name: Stainless steel Weld neck flange
Dimension and Wall Thickness
Seamless: 1/2”~24” (DN15~DN600) SCH5~SCH XXS
End connection：PE or BE Marking： according to...
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Alloy Steel Weld Neck Flange
Product Name: Alloy steel Weld neck flange
Dimension and Wall Thickness
Seamless: 1/2”~24” (DN15~DN600) SCH5~SCH XXS
End connection：PE or BE
Marking： according to...
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Long Weld Neck Flange ASME B16.5
Product Name: long weld neck flange ASME B16.5
Dimension and Wall Thickness
Seamless: 1/2”~24” (DN15~DN600) SCH5~SCH XXS
End connection：PE or BE
Marking： according to...
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Raised Neck Flange
Product Name: raised neck flange
Seamless: 1/2”~24” (DN15~DN600) SCH5~SCH XXS
End connection： PE or BE
Marking： according to customer’s requirement or brand+ seamless pipe+...
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Benefits of Welding Neck Flanges

Superior Strength
Weld neck flanges are incredibly strong due to their welded neck design, making them ideal for high-pressure and high-temperature applications. They are often required selections over threaded or slip on styles due to their superior integrity.

Leak Resistance
Their precision welding ensures a tight seal, minimizing the risk of leaks and providing enhanced safety. The smooth transition from the flange to the pipe reduces stress concentration, preventing cracks and failures.

Alignment Accuracy
Weld neck flanges facilitate precise alignment of pipes, resulting in better flow and reduced turbulence.Given their size/shape, these flanges typically have a longer lifespan due to their resistance to wear, corrosion, and erosion.

Reduced Maintenance
With fewer chances of leaks and failures, maintenance costs are lower than other flange types.The smooth bore of weld neck flanges reduces pressure drop and turbulence, enhancing fluid flow.

Easy to Align, Install, and Test
Weld neck flanges can easily align to the pipe network in which it gets installed, resulting in a more robust weld. Also, the flange design makes it very accessible when inspecting the integrity of the weld via radiography testing.

Smooth Flow of the Liquid
Weld neck flanges match the pipe's internal diameter, allowing a smooth, high-pressure liquid flow. Also, the design assures that there is little “turbulence” within the pipe, a common reason for erosion, leading to robust, more durable pressure vessel connections.

Strong and Reliable
Weld neck flanges increase the pipe thickness from the weld all the way to the face of the flange. This design assures that the internally

Types of Welding Neck Flanges

Long weld neck Flange
The Long Welding Neck Flange is an enlarged version of the commonly used welding neck flange. It is frequently used as a nozzle for columns and barrels and comes in two types: the LWN Heavy Barrel and the Equal LWN Barrel. Both versions have a robust wall structure and unique shapes.

Reducing Weld Neck Flange
A “Reducing Weld Neck Flange” is not a distinct kind of flange. The term “reducing” generally indicates a flange that links pipes or fittings of varying sizes and is made to transform from a bigger pipe size to a smaller one. A “reducing flange” with a larger outer diameter (OD) on one side and a smaller OD on the other is used to connect pipes with different diameters.

Standard Weld Neck Flange
A standard weld neck flange is a flange variety with a lengthy, conical neck that joins pipes via butt weld strengthening the joint and spreading the stress onto the pipe.

NW Long Weld Neck Flanges
The NW LWN flanges, also known as NW Long Weld Neck Flanges, are a flange type frequently used for vacuum systems. These flanges are defined by their elongated, tapering necks and are typically composed of high-quality materials like stainless steel.Their lengthy neck adds durability and stiffening, making them appropriate for high-vacuum applications. These flanges are designed to be directly welded onto the vacuum chamber or other vacuum system elements to ensure an airtight and secure connection that maintains the vacuum system’s integrity.

Application of Welding Neck Flanges

Oil and gas
In offshore platforms, the flanges connect piping systems that transport oil and gas from the seabed to the surface. They can withstand harsh environmental conditions, including strong currents, corrosive saltwater, and challenging weather. Similarly, they are widely used in refineries and processing plants in onshore oil and gas operations.

Petrochemical and chemical
The petrochemical and chemical sectors frequently encounter high pressures, corrosive substances, and extreme temperatures. The flanges establish connections between pipes and valves used in refining and handling chemicals, petroleum, and gas. Due to their robust construction and ability to prevent leaks, they are well-suited for these challenging industrial applications.

Pharmaceutical and food processing

Stainless steel flanges are preferred in pharmaceutical and food processing applications due to their corrosion resistance and ease of cleaning. They are also compatible with stringent cleaning agents and disinfectants. In addition, their smooth surface finish minimizes the accumulation of residue and bacteria, facilitating sterilization procedures.

Power generation

Thermal, nuclear, and renewable energy facilities heavily rely on flanges to establish secure connections in critical elements. These include steam lines, condensers, turbines, and other components. The flanges are also employed to guarantee leak-free joints and endure the effects of elevated temperatures and high pressures.

Shipbuilding and maritime

Weld neck flanges are employed in the fuel systems of ships and marine vessels. They connect the fuel pipelines, ensuring a secure transfer from storage tanks to engines. This is important given the criticality of fuel supply for propulsion and power generation in marine operations.

Materials and specifications of welding flanges

Material Selection
Welding Neck Flanges are available in various materials, including carbon steel, stainless steel, alloy steel, and more. The choice of material depends on factors such as temperature, pressure, and the nature of the fluid or gas being transported.

Pressure Ratings
Flanges come with different pressure ratings, which indicate their ability to withstand pressure. Common pressure ratings include 150, 300, 600, 900, 1500, and 2500 pounds per square inch (PSI).

Flange Face Type
Different face types, such as flat face (FF), raised face (RF), and ring type junction (RTJ), can be found on weld neck flanges. The application’s sealing needs will determine the face type to use.

Size
To accommodate various pipe sizes and flow rates, weld neck flanges come in a broad variety of sizes, from small diameters to extremely large ones.

How to Choose Welding Neck Flanges

Application Requirements

Recognize the particular needs of your application, including the temperature, pressure, and kind of fluid or gas being conveyed. Your decision on material and pressure rating will be guided by this information.

Material Selection

Select a material that can handle the demands of your application. Corrosion resistance, temperature tolerance, and strength are a few things to think about.

Pressure Rating

Choose a weld neck flange with a pressure rating higher than the system’s maximum operating pressure. A safety buffer is usually preferable.

Flange Face Type

Choose the proper flange face type (e.g., RF for raised face for a tighter seal) based on your system’s sealing needs.

Compliance with Standards

Ensure that the weld neck flanges you select conform to the applicable industry requirements. This makes sure they adhere to standards for quality and safety.

Quality Assurance

Choose trustworthy suppliers like SK Steel Flange, who are renowned for their dedication to quality and rigorous quality control procedures.

Production Process of Welding Neck Flanges

1. Material and Equipment Selection

The welding materials required for weld neck flange welding mainly include welding wires and welding rods. Choosing welding materials that are suitable for the pipeline material and operating conditions is crucial. For instance, when welding high-temperature pipelines, heat-resistant welding materials capable of withstanding high temperatures should be selected. Additionally, welding equipment such as arc welding machines and gas shielded welding machines must comply with operational requirements to ensure the stability and safety of the welding process.

2. Preparation of Welding Surfaces

Thorough preparation and cleaning of the welding surfaces are essential before weld neck flange welding. The welding surfaces must be completely free of grease, dust, and other impurities to prevent the occurrence of porosity or poor welding quality. Moreover, the surface of the welding surfaces should be smooth and flat to ensure the firmness and sealing of the weld joint. Grinding and cleaning can be employed to prepare the welding surfaces, ensuring the smoothness and flatness of the weld joint.

3. Welding Techniques Mastery

Proficient mastery of welding techniques is crucial to ensure welding quality. Welding techniques involve factors such as welding current, welding speed, and welding temperature. Adjusting welding parameters according to the type and thickness of the pipeline material, as well as specific welding requirements, is essential. For example, when welding thick-walled pipelines, increasing welding current and speed is necessary to ensure welding quality.

4. Quality Inspection and Acceptance

After completing the weld neck flange welding, quality inspection and acceptance must be conducted. Commonly used quality inspection methods include X-ray inspection, ultrasonic testing, magnetic particle inspection, etc. These inspection methods enable the timely detection of welding defects, cracks, porosity, and other issues, ensuring welding quality and safety. Only welding quality that passes acceptance can ensure the safe operation of pipeline systems.

5. Safety Regulations and Procedures

Strict adherence to safety regulations and operational procedures is imperative during weld neck flange welding. Operators must wear appropriate protective equipment such as gloves, face shields, work suits, etc., to protect themselves. Additionally, attention must be paid to fire prevention and ventilation to avoid fires and the generation of harmful gases, ensuring the safety and stability of the welding process.

Operation Precautions For Flat Welding Neck Flanges

1. In order to prevent the corrosion between the eyes due to the heating of the flange cover, the welding current should not be too large, less than about 20% than the carbon steel electrode, the arc should not be too long, the interlayer cooling is fast, and the narrow welding bead is better.

2. The electrode should be kept dry when using it. The titanium calcium type should be kept at 150℃ for 1 hour, and the low a hydrogen type should be kept at 200-250℃ for 1 hour to prevent the electrode coating from sticking to oil and other dirt, so as not to cause the weld. Increase the carbon content and affect the quality of weldments.

3. When flat-welded flange pipe fittings are welded, they are repeatedly heated to precipitate carbides, which reduces the corrosion resistance and mechanical properties of the product.

4. After welding, chrome flat welded flange pipe fittings have large hardenability American standard flanges, which are prone to cracks. If the same type of chromium stainless steel electrode (G202, G207) is used for welding, preheating above 300℃ and slow cooling treatment at about 700℃ after welding must be carried out. If the weldment cannot be subjected to post-weld heat treatment, flat welding flange pipe welding rods (A107, A207) should be used.

5. For flat welding flanges, appropriate amount of stability elements Ti, Nb, Mo, etc. are added to improve corrosion resistance and weldability. The weldability is better than chrome flat welding flanges. When using the same type of chrome flat welding flange electrode (G302, G307), preheating above 200℃ and tempering treatment at about 800℃ after welding should be carried out. If the weldment cannot be heat treated, flat welding flange pipe welding rods (A107, A207) should be used.

Our Factory

Shanghai KAIKE Pipe Technology Co., Ltd. is a reputable AAA listed pipe fittings manufacturer in China,covering an area of 66666㎡ (80000+ ㎡in stage II) and with technician and engineers more than 30 personal. Kaike Group is made up of Shanghai Kaike Piping Technology, Shanghai Kaike Valve manufacture and one export company Shanghai Chainmill Industry, they are all based in Shanghai, which the economic center of China. KAIKE has reached up to an annual output of pipe fittings of 20,000 tons.KAIKE has the ability to produce by various materials like carbon (low temperature) steel, stainless steel, duplex steel, alloy steel, nickel base alloy and special materials as requested according to GB, SH, Hg, JB, SY, ASME/ANSI, MSS, JIS, DIN, BS,GOST etc.Its main products include BW pipe fittings(SMLS or welded), steel flange, forged pipe fittings as well as prefabricated spools and manifolds,and also can produce according to customers' drawings and requirements.

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FAQ

Q: What is the difference between slip on and weld neck flanges?

A: A slip-on flange is a type of pipe flange that is slipped over the end of a pipe and welded in place. A weld neck flange is a type of pipe flange that has a neck that is welded to the pipe. Slip-on flanges are typically used for low-pressure applications, while weld neck flanges are used for high-pressure applications.

Q: What are weld neck flanges used for?

A: There are two types of weld neck flanges, which are standard and long. Standard weld neck flanges are used in butt weld fittings. Long weld neck flanges are used with vessel nozzles and equipment. The flanges are created to match the pipe's inside diameter or fitting.

Q: What is the difference between weld neck and long weld neck flanges?

A: A typical weld neck flange has a weld prep at the tip of the neck to weld up to matching pipe, whereas long weld neck flanges, or “nozzles,” are square cut at the ends for the purpose of utilization with your tank or alternate assembly.

Q: Can two weld neck flanges be welded together?

A: Any butt-weld fitting or weld-neck flange can be directly welded to any other butt-weld fitting or weld neck flange without the need for any extra piece of pipe (Pup piece) between them.Flange schedule usually appears in weld neck flange and socket welding flange. Whether the same class flange could have a different schedule? Of course,if same class flange is used with different schedule pipe, the flange schedule will also be changed according.

Q: What is the difference between socket weld flange and weld neck flange?

A: Usually, the socket weld flange is not welded in the flange of the pipe and the shoulder. Weld neck flange has a long conical hub, often used in high pressure applications. The sealing surface of the welding neck flange is RF (raised face), FF(flat face) and ring joint (RTJ).

Q: What is the difference between lap joint and weld neck flange?

A: A Lap Joint Flange is a two piece device that is much like a weld-neck flange but also like a loose slip-on flange. One piece is a sleeve called a 'Stub-end" and is shaped like a short piece of pipe with a weld bevel on one end and a narrow shoulder on the other end called the hub.

Q: Why are welded neck flanges considered to be the strongest of all?

A: Superior Strength: Weld neck flanges are incredibly strong due to their welded neck design, making them ideal for high-pressure and high-temperature applications. They are often required selections over threaded or slip on styles due to their superior integrity.

Q: What is the hub of the welding neck flange?

A: A weld neck flange has a long tapered hub that transitions smoothly to the pipe or fitting it is welded to. It is typically butt-welded to the line, meaning the end is inserted into the flange and then welded around the circumference. This creates a strong and leak-proof joint.

Q: How much gap between two welds?

A: Here are some guidelines from a few commonly used codes and standards: American Welding Society (AWS) D1. 1: The minimum distance between welds should be at least four times the thickness of the thinner part joined, but not less than 1 inch (25 mm).

Q: Why use long weld neck flange?

A: Long weld neck flanges are often found as anchors in the water mains. The reason is that they can withstand higher pressures; you can connect larger networks of pipes, like those in a factory. You can also use long weld neck flanges in the expansion bends or to reduce or extend pipe sizes.

Q: Where is socket weld flange used?

A: Socket-weld pipe flanges are typically useful on smaller sizes of high-pressure pipes. These pipe flanges are attached by inserting the pipe into the socket end and applying a fillet weld around the top. It allows for a smooth bore and better flow of the gas or fluid inside the pipe.

Q: What are the disadvantages of lap joint flanges?

A: One of the drawbacks of lap joint flanges is that they can not handle high-pressure or critical applications. They need gaskets to create seals, which may need replacement regularly. Additionally, the face of the flanges is susceptible to corrosion, which may compromise the integrity of the piping system over time.

Q: Is there a difference between ANSI and ASME flanges?

A: ANSI flanges are crafted with versatility, allowing for a wide range of sizes, pressure ratings, and materials to suit diverse applications. ASME flanges undergo meticulous design and manufacturing processes, ensuring adherence to uncompromising specifications and quality standards.

Q: What is the difference between ASTM and ASME flange?

A: Basically ASTM creates the material specifications and standard test methods to determine compliance. ASME selects those ASTM materials which will perform adequately in boiler or pressure vessel service and accepts them with stated limitations.

Q: What is the difference between weld neck and long weld neck?

Q: When to use weld neck flange?

A: Weld neck flanges are used in applications where the conditions are severe and critical. Some of these conditions include high pressure, wide fluctuations in temperature and pressure, high temperature, fluids that are volatile and hazardous, and temperatures in the sub-zero range.

Q: What material is a weld neck flange made of?

A: The welding neck flange can be designed from diverse materials such as stainless steel, carbon alloy, nickel alloy, and many others. In addition, the UNS S31803 Duplex Steel material is also in use. As for the Nickel Alloy materials, Inconel 600 and 625, Hastelloy C22, and C276 are available.

Q: What is the difference between slip on and socket weld flanges?

A: Socket welded flange shape is similar to slip on flange, differently it has a shoulder at the inner bore. Slip On Flange - No shoulder at inner bore. Socket weld flange static strength is equal to slip on flange, but it's fatigue strength is 50% higher than the double welded slip on flange.

Q: Why a lap flange and stub end would be used instead of a weld neck flange?

A: The lap-joint flange and stub-end assembly are used mainly in piping systems that necessitate frequent dismantling for inspection or routine maintenance. It is also used in the erection of large diameter or hard-to-adjust piping configurations because of its quick bolt hole alignment.

Q: What does xh bore mean?

A: Extra Heavy
Bore refers to the thickness of the pipe wall. Weldneck flanges are typically found in standard (STD), Schedule-10 (S10) and Extra Heavy (XH). To specify a weldneck flange you must match the size and bore to the nominal pipe size and schedule.

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