What is a weld neck (RFWN) flange?

RFWN stands for raised face weld neck. The raised face is the gasket seating area, and the weld neck is the long tapered hub that joins the flange to the pipe with a butt weld.

In EN1092-1 this is the type 11 weld neck flange. In ANSI B16.5 it’s the weld neck form.

How does a weld neck flange work?

The long tapered hub is the defining feature. The hub is butt welded to the pipe, so the flange becomes a continuous part of the pipework rather than a ring sitting on the outside of it.

That continuity is the point. The hub shares the stress of the pipe it’s welded to, which is why weld neck flanges can be used in extreme temperature or pressure situations.

What are the strengths and limits of weld neck flanges?

Weld neck flanges are the strongest of the common flange types, so they’re the right choice when the duty is demanding. The tapered hub spreads load into the pipe and gives a smoother path for the flow.

The trade-off is that they’re bulkier and cost more than a slip-on. For milder duties, our RFSO flanges are the economical alternative, and the choice usually comes down to the pressure, temperature and load on the joint.

Which standards do weld neck flanges follow?

We hold ANSI B16.5 weld neck flanges at 150LB and 300LB, and EN1092-1 weld neck flanges across our PN ratings, so check which standard your system follows before you order.

The flange bore needs to suit your pipe’s wall thickness, so tell us your pipe specification if you’re unsure. Our ANSI weld neck names carry a code such as X10S, X40S or X80S, which relates to the pipe schedule the bore is made to suit, so quote it if you have it.

Which butt weld fittings go with weld neck flanges?

Weld neck flanges are welded to the pipe in the same way as the fittings in our butt weld fittings range, so they sit naturally together. That makes it straightforward to build a fully butt welded system.

If you’re deciding between welded joint types, the differences between buttweld and socket weld fittings are worth understanding.

What are the common ordering mistakes?

The most common mistake is overlooking the bore, which has to suit the pipe the flange is welded to. The second is mixing classes or ratings, such as a 150LB flange against a 300LB one.

The third is mixing standards, because ANSI B16.5 and EN1092-1 flanges use different drilling.

What should you tell us when you enquire?

A weld neck flange has to suit the pipe it will be welded to, so the pipe comes first. Please tell us:

1. The pipe size and the pipe specification, because the bore and wall thickness need to suit the pipe.

2. The standard and rating you want, for example ANSI B16.5 150LB or 300LB, or EN1092-1 at the PN rating you require.

3. That you want a raised face, which is the raised ring on the flange that the gasket sits against.

4. The grade, either 304 or 316.

5. How many you need.

If you’re unsure about the pipe specification, tell us what the pipe is and we’ll help you work out the right bore.

Frequently asked questions

What does RFWN stand for?

RFWN stands for raised face weld neck. The raised face is the gasket seating area, and the weld neck is the long tapered hub that is butt welded to the pipe.

Why are weld neck flanges used for demanding duties?

The hub shares the stress of the pipe it’s welded to, which is why weld neck flanges can be used in extreme temperature or pressure situations.

What is the difference between a weld neck and a slip-on flange?

A weld neck flange is butt welded through its tapered hub and suits demanding duties, but it’s bulkier and costs more. A slip-on flange slides over the pipe and is welded inside and outside, which is cheaper and easier to fit but better suited to low-pressure, low-temperature use.

Which standards do your weld neck flanges follow?

We hold ANSI B16.5 weld neck flanges at 150LB and 300LB, and EN1092-1 weld neck flanges, which are type 11 in the standard.

Contact Anglo Stainless for more information

Our weld neck flanges are available in 304 or 316. If you’d like to talk through your application, contact us and a member of our team will be happy to help. You can also request our brochure using the form below.