# Weld neck flange

> Forged weld neck flanges to ASME B16.5 and B16.47 in A105, A350 LF2 and A182 grades, and what a flange request needs to state to be quoted properly.

URL: https://jjprojectsok.com/products/steel-structural/flange-weld-neck  
Español: https://jjprojectsok.com/es/products/steel-structural/flange-weld-neck  
Updated: 2026-10-16

Forged flange with a tapered hub butt welded to the pipe, used in high-pressure and cyclic service.

**In short:** Forged flange with a tapered hub butt welded to the pipe, used in high-pressure and cyclic service. JJ Projects sources it to the specification the buyer names. Typical reference, standards: ASME B16.5 (to NPS 24), ASME B16.47 (larger sizes).

## Specification references

- Standards: ASME B16.5 (to NPS 24), ASME B16.47 (larger sizes)
- Materials: ASTM A105, A350 LF2, A182 (alloy and stainless)
- Class and face: Class 150 to 2500; raised face or ring-type joint
- Bore: Matched to the pipe schedule

> Typical references only. The governing specification is the one on your purchase order or datasheet.

## Typical uses

- Piping in high-pressure, high-temperature and cyclic service
- Nozzle connections on vessels, exchangers and pumps
- Hydrocarbon and other hazardous lines where butt welds are examined by radiography
- Joints that must be dismantled for maintenance

## What to include in a request

A request with these details can be quoted without a round of questions. Send what you have and we will ask for the rest.

1. NPS and pressure class, from Class 150 to 2500
2. Standard: ASME B16.5 up to NPS 24, or ASME B16.47 Series A or Series B for larger sizes
3. Facing: raised face, flat face or ring-type joint, and the surface finish if specified
4. Bore or pipe schedule, so the hub matches the pipe it is welded to
5. Material and grade, for example ASTM A105, A350 LF2 or A182 F316L, with any low-temperature or sour service requirement
6. Quantity
7. Documents: material test report, for example EN 10204 type 3.1, and any marking or testing requirement

[Request this item](https://jjprojectsok.com/request-a-quote?item=flange-weld-neck)

## Questions

### Why must I state the pipe schedule for a weld neck flange?

The bore of a weld neck flange is machined to match the inside diameter of the pipe it joins, so the schedule or wall thickness fixes the bore. A wrong bore leaves a step at the weld that disturbs flow and welding.

### When is a weld neck flange chosen over a slip-on?

The tapered hub carries stress smoothly into the pipe, so weld neck flanges are the usual choice for high pressure, high temperature, cyclic loading and hazardous fluids. Slip-on flanges are easier to align but are limited by many piping specifications.

### What is the difference between B16.47 Series A and Series B?

Both cover large-diameter flanges above NPS 24. Series A flanges are heavier and Series B are lighter, with different bolt circles, so a Series A flange does not mate with a Series B flange of the same size and class.

## Related items

- [Slip-on flange](https://jjprojectsok.com/products/steel-structural/flange-slip-on): Forged slip-on flanges to ASME B16.5 in A105 and A182 grades, raised or flat face, and what to state when you request slip-on flanges for a quote.
- [Blind flange](https://jjprojectsok.com/products/steel-structural/flange-blind): Forged blind flanges to ASME B16.5 and B16.47 in A105 and A182 grades, Class 150 to 2500, and what to include in a blind flange request for a quote.
- [Stud bolt with nuts](https://jjprojectsok.com/products/steel-structural/stud-bolt): Stud bolts with heavy hex nuts: ASTM A193 B7, B8M and L7 studs with A194 2H nuts for flanged joints, and what to state in the request so it can be quoted.
- [Spiral-wound gasket](https://jjprojectsok.com/products/steel-structural/spiral-wound-gasket): Spiral-wound gaskets to ASME B16.20 with 304 or 316L winding and graphite or PTFE filler, for raised-face flanges, with request details needed to quote.

## Guides

- [Flange pressure classes: ASME B16.5 and B16.47](https://jjprojectsok.com/knowledge/flange-pressure-classes): How ASME flange classes 150 to 2500 work: B16.5 vs B16.47, pressure-temperature ratings, facings RF, FF and RTJ, flange types and common materials.
- [Stud bolts and gaskets: ASTM A193 and A320](https://jjprojectsok.com/knowledge/stud-bolts-and-gaskets): How to specify flange bolting and gaskets: ASTM A193 B7, B7M, B8, A194 2H and 2HM nuts, A320 L7, coatings and spiral-wound gaskets to ASME B16.20.
- [Pipe schedules: NPS, OD and wall thickness](https://jjprojectsok.com/knowledge/pipe-schedules-explained): NPS is a label, not a measurement. Learn how pipe schedule sets wall thickness under ASME B36.10M and B36.19M, with OD and wall tables for NPS 2, 4, 6 and 8.

[All steel and structural](https://jjprojectsok.com/products/steel-structural)