Welding neck flanges

The Welding neck flanges 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 welding 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.

Standards, Dimensions & Weight

• ASME/ANSI B16.5 Class 150 WN
• ASME/ANSI B16.5 Class 300 WN
• ASME/ANSI B16.5 Class 600 WN
• ASME/ANSI B16.5 Class 900 WN
• ASME/ANSI B16.5 Class 1500 WN
• ASME/ANSI B16.5 Class 2500 WN
• ASME B16.47 Series A/MSS SP-44 Class 150 WN
• ASME B16.47 Series A/MSS SP-44 Class 300 WN
• ASME B16.47 Series A/MSS SP-44 Class 600 WN
• ASME B16.47 Series A/MSS SP-44 Class 900 WN
• ASME B16.47 Series B/API 605 Class 75 WN
• ASME B16.47 Series B/API 605 Class 150 WN
• ASME B16.47 Series B/API 605 Class 300 WN
• ASME B16.47 Series B/API 605 Class 600 WN
• ASME B16.47 Series B/API 605 Class 900 WN
• BS 3293 Class 150 WN
• BS 3293 Class 300 WN
• BS 3293 Class 600 WN
• DIN 2631 PN 6
• DIN 2632 PN 10
• DIN 2633 PN 16
• DIN 2634 PN 25
• DIN 2635 PN40

Specifications:

Size: 1/2” to 60”, DN 12mm to DN 1500mm
Pressure class: Class 150 to Class 2,500, PN 2.5 to PN 250
Facing: RF / RTJ

Material:

• Cabon steel: A105, A350 LF2, C22.8, S355JR
• Stainless steel: A182 F304/F304L/F316/F316L/F321
• Alloy steel: F11, F12

Packing: plywood case and plywood pallet

Therefore, this kind of flange is more suitable for most of the extreme service conditions, whether this results from elevated temperature or high pressure, and whether loading situations are significantly constant or change between broad limits; welding flanges are specifically suggested for managing explosives, costly and flammable liquids, where local failure or loss of firmness can be resulted after a disastrous consequence or event.

Following are the dimensions of weld neck flanges:
As far as the sizes for these flanges are concerned, all these flanges are available in the market in carried size, ranging from ¼’’ to any size. If we talk about the wall thickness of these flanges, they are from schedule 5s to schedule XXS and are usually heavier.

Now let’s see the pressure ratings and dimensions of these flanges. The dimension is ANSI, MSS-SP-44, BS 3294, API 605 150lb to 2500 lb.
The facing of these flanges is also of numerous styles, including raised faced, large tongue and groove, ring type joint, small tongue and groove, etc. It is to be noted that all these specifications are not just standards, but can be altered and specially made in the case of any project where customization is required.

Following are the material grades, in which these flanges are available:
If the material is stainless steel, then grade includes A182 F304/L, F310, F316/L, F321/H, F347/H, F410, F440 and 904L. If the material is carbon steel, the grade is A105 and C22.8. If the material is low-temperature steel, the grade includes A350 LF2, LF3 and LF6. If the material is alloy steel, the grade includes A182 F1, F5, F9, F11, F12, F22 and F91. If the material is High Yield alloy steel, the grade includes A694 F42, F52, F60, F65 and F70. If the material is Nickel Alloys, the grade includes 200, 400, K500, 600, 625, 800 and 825. Other materials include aluminum, copper, bronze, brass and titanium.

The application of neck weld flanges are vast and widespread across a number of industries, especially in those where heavy pressure and stress are involved in the services, such as construction, public services, cleaning, chemicals, petroleum and so on. The most general usage of a weld neck flange is seen at the end of valves, pipes, different objects and other types of things which can give different impacts on the assembly and disassembly of the piping system.

Uses
These are most commonly used to fix the pipes or different objects in various industries. This is why they the manufactured in a way so they would sustain even the highest of pressures without getting deformed or damaged. This is why they are capable of bearing very high stress and pressure in industries such as chemical industries where products are made at very high temperature. They are very successful in the chemical industry because the chemicals demand transmission with a lot of strength and pressure.

Probably the greatest advantage of the weld neck flanges is that the welded connection is not able to interrupt the liquid flow through the system. Moreover, it is much easier to align the pipe because the weld joint is placed at the end of the connection. Since they are manufactured with a long tapered hub, they have a high strength and resistance for dishing and similar purposes. 

Dimensions
The most typical size is B16.5, and there are different classes there such as 150, 300, 400, 600 and 900, etc. They vary from each other in diameters and shapes which can be customized as per requirements of the business. Then there are stud bolts that are available in some lengths and widths. Most commonly, they are available in the market with the thickness ranging from 3.2 mm to 4.8 mm but custom sized ones can also be manufactured.

ANSI B16.5 Class 150 are most of the times furnished with a 1/6” raised face, but it is no general rule and can also be customized according to the requirements. Standard bore is present that are easily available in the market and are used for a lot of purposes. Flat face option is not rare either, but it can be skipped or modified to change the dimensions.