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The Most Common Flange Types

Flange O’Clock: Episode 1

What are flanges? Join host John Barnett in Texas Flange’s new educational video series, Flange O’Clock, as he demonstrates and explains everything you need to know about flanges.

Today’s episode goes over the 6 most common flange types; Weld Neck, Threaded, Slip On, Lap Joint, Socket Weld, and Blind per ASME B16.5. Thank you for watching and we hope you learn a lot from our videos! If there’s anything you’d like to learn that we didn’t cover here, leave us a comment and we’ll get your answer ASAP.

In this video, I’m going to go over the six basic types of flanges per ASME B16.5

The Weld Neck, Threaded, Slip-On, Lap Joint, Socket Weld, and Blind Flange.

All six flanges before me are for one-inch nominal pipe size, class 150 per B16.5, and raised face. Or in short, 1” 150# RF, with the exception of the Lap Joint, which will be explained later.

Weld Neck Flanges

The Weld Neck flange is the most commonly requested flange. It features a neck extension with a tapered hub, a 37.5-degree bevel, and a 1/16” landing at the point of the weld. This will butt directly onto another pipe with a similar level, where it will be welded together with a 75-degree weld.

Because it butts directly onto the pipe, it is going to match the OD and the ID of the pipe. You’ll need to tell us the schedule you’re using. You could also give us the ID, or inner diameter, which is another word for the bore, or you can tell us the wall thickness. Once you give us any of those, we will be able to make your flange meet the pipe exactly.

Threaded Flanges

The Threaded flange, or companion flange, features an NPT. In this case, it’s a one-inch flange, so it has a one-inch Female National Pipe Thread center, which is used to mate to male threaded pipe. It’s a tapered thread, so when the pipe is fully threaded down, it will bottom out, like so. Threaded flanges are commonly used in reducing connections as well.

Slip-On Flanges

The Slip-On flange is a simple and cost-effective alternative to the Weld Neck flange. It has a straight-through ID, and as the name implies, slips on to pipe. The pipe is then welded along the OD on the top of the hub. This separates the heat-affected zone from the rest of the flange.

In larger sizes and higher-pressure classes, you’ll see more of a hub. Other applications might call for the pipe to be pulled back 3/16 of an inch, and a 90-degree fillet weld to be performed on the ID of the flange. It is possible to have both welds performed if the application calls for it.

Lap Joint Flanges

The Lap Joint flange is similar to the Slip-On, except it is always flat-face, and has a radius on the ID, or inner diameter, to accommodate a stub end. The normal application calls for the flange to slide up the pipe for your stub to be butt-welded directly onto your pipe, and then your flange will slide over the weld onto the stub end.

You’ll see the stub end’s flair, or flanged portion extends out and creates the raised face section of the bolted flange connection.

Socket Weld Flanges

The Socket Weld flange is similar to a Slip-On, except that it has a counter-bore step. This is convenient in situations where there is a space limitation. Just like a Slip-On, the pipe will go into the flange, but then butt up against that counterbore step, creating a flush surface along the ID of the pipe, and the ID of the flange.

So, just like Weld Necks, Socket Welds will need to be specified with a schedule, or a bore, or ID, or the pipe’s wall thickness. You tell us any of those, and we’ll make sure you get the flange you need.

Blind Flanges

The Blind Flange has no ID or threads. It is only used to cap off a line, bolting onto another flange, flanged fitting, or flanged valve. You’ll also notice it has no hub. Per B16.5, Blinds do not require hubs.

You can also alter a Blind by drilling through to create a reducing Slip-On, from the Blind, or drill and tap to create a reducing Threaded from the Blind. In applications where you require a hub, which you’ll see in another video, we can provide a high hub blind and then alter it per your requirements.

These six flange types are, of course, not the only types of flanges available. If you have the need for anything else, be it plate flanges, metric flanges, high yield, carbon steel, stainless steel, nickel alloys, or anything else that’s round with bolt holes in it, we’d be happy to help.

If you have any questions, give us a call or shoot us an email, that way we can get you the flanges you need, when you need them.

If you still need help deciding which is better for your project, pipeline, or job, feel free to call (281-484-8325) or e-mail the Texas Flange sales office anytime from 8 am to 5 pm Monday through Friday. Or you can drop a quick question or inquiry into our quick contact form. With our decades of expertise, we can help you get the flanges you need.

Check out Episode 2 HERE! We explain pressure class, why it’s important, and the difference between the different classes from 150# to 2500#!

If you’d like to learn more about flange specifications, types uses and more feel free to peruse our informational blog posts, free 3-D and CAD drawings, or flange charts.

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2 months ago

Thanks for the descriptions. Wish there visuals – pics /drawings.