Weld Neck Flanges

Weld neck flanges are used in piping systems that require a butt-welded flange connection. Their tapered hub provides a smooth transition from the flange to the pipe, which is why they are commonly specified for process piping, utility service, and other applications where connection integrity and dimensional consistency matter.

PipingNow offers weld neck flanges in 150#, 300#, and 600# classes, with 304L stainless steel, 316L stainless steel, and 150# aluminum options available in this collection. Sizes range from 1/2 in through 24 in, with 10s, 40s, and 80s schedule options available across the product mix.

Materials, Classes, and Schedules

The 150# range includes both stainless steel and aluminum options, while the 300# and 600# ranges are available in stainless steel. 304L is commonly used for general stainless applications, while 316L is often selected where additional corrosion resistance is required. Schedule also plays an important role, since the flange bore needs to correspond with the pipe being installed.

Classes: 150#, 300#, and 600#
Materials: 304L stainless steel, 316L stainless steel, and aluminum
Schedules: 10s, 40s, and 80s
Sizes: 1/2 in through 24 in

Typical Applications

These are commonly used on process lines, plant piping, utility systems, skids, and fabricated assemblies where a butt-welded flange is called for by design. In stainless systems, they are often selected where the material, pressure class, and bore need to align closely with the rest of the piping specification.

process piping
plant and utility systems
fabricated skids and assemblies
stainless piping installations
applications requiring schedule-specific bores
systems designed around butt-welded flange connections

What to Check Before Ordering

Pressure class, nominal size, material, and schedule should all be confirmed before ordering. The flange bore needs to match the pipe correctly, and the facing and mating flange details should also be verified. If one of those specifications is off, the part may appear close but still be wrong for the application.

pressure class
nominal size
material grade
pipe schedule / flange bore
facing and mating flange compatibility
service conditions
project specification

FAQs

What is a weld neck flange?
A flange with a tapered hub designed for a butt-welded connection to the pipe.

What pressure classes are available?
150#, 300#, and 600#.

What materials are offered?
304L stainless steel, 316L stainless steel, and aluminum.

What schedule ratings are available?
10s, 40s, and 80s.

What size range is available?
1/2 in through 24 in.

What should I match before ordering?
Pressure class, nominal size, material, pipe schedule, and mating flange details.

How does a weld neck flange differ from a slip on flange?
A weld neck flange is designed for a butt-welded connection with a tapered hub, while a slip on flange fits over the pipe before welding.