What is a screwed (SCRD) flange?

A screwed flange has an internal thread, so it fits onto a threaded pipe without welding. That makes it useful where welding isn’t practical.

It’s also called a threaded flange. Some of our ANSI versions are listed as RF bossed, which is part of the product name you’ll see in the listings.

How is a screwed flange fitted?

A screwed flange has a thread inside its bore. It screws straight onto a pipe that has a matching thread on the outside. There’s no welding, so you can fit it without hot work. That is the main reason people choose it.

Because the thread does the joining, the thread type has to match the pipe exactly. That’s why the thread is the first thing to check when you order.

What are the strengths and limits of threaded flanges?

Screwed flanges are quick to fit. You don’t need a welder, and ordinary tools are enough to screw one on. That makes them handy for small pipe runs, repairs and sites where welding isn’t allowed.

The thread is also the limit. A threaded joint can work loose or leak if the pipe gets hot, vibrates or goes through big changes in temperature. Screwed flanges also suit smaller pipe sizes. Like slip-on flanges, they’re best suited to low-pressure, low-temperature applications.

For demanding duties or larger pipe, a welded flange is the better choice. Our RFSO flanges or RFWN flanges are the usual alternatives.

Should you choose BSPT or NPT?

Our screwed flanges come with either BSPT or NPT threads. BSPT (British Standard Pipe Taper) is the British standard taper thread. NPT (National Pipe Taper) is the American standard. Both narrow slightly along their length, but they aren’t the same, so one won’t fit the other.

The right choice is the one that matches your pipe or fitting. BSPT is the usual choice on UK and European pipework, while NPT is common on American-made equipment.

If you’re unsure which thread you have, start by telling BSPT, NPT and BSPP threads apart. BSPP (British Standard Pipe Parallel) has a straight thread, so it behaves differently from the two taper threads. Once you know the type, you can measure the BSP pipe fitting to confirm the size.

How do EN1092-1 and ANSI B16.5 screwed flanges differ?

In our EN1092-1 range, a screwed flange appears as a name like DN100 EN1092-1 PN16/13B RF SCRD, where 13 is the hubbed threaded flange type and B is the raised face.

Our ANSI B16.5 screwed flanges are held at 150LB. They sit within our wider EN1092-1 and ANSI B16.5 ranges.

Which threaded fittings match a screwed flange?

Screwed flanges pair with threaded fittings such as:

BSP screwed fittings, which suit BSP threaded pipework

High pressure NPT fittings, for NPT threads

A screwed flange often acts as the bridge between a threaded pipe run and flanged equipment such as a valve, pump or vessel, so matching the thread on both sides is what makes the joint work. For welded joints instead, look at our RFSO flanges or RFWN flanges.

What are the common ordering mistakes?

The most common mistake is a thread mismatch. BSPT and NPT are both taper threads but they aren’t the same, so don’t assume one will fit the other. The second is ordering a screwed flange for a duty that needs a welded one.

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

What should you tell us when you enquire?

The detail that most often needs checking is the thread. Please tell us:

1. Whether your pipe or fitting has a BSPT or an NPT thread.

2. The pipe size.

3. The standard and rating you want, such as EN1092-1 PN16 or ANSI B16.5 150LB.

4. The grade you need.

5. How many you need.

If you’re unsure which thread you have, a photo of the pipe end or fitting is usually enough for us to identify it. We’d much rather confirm it with you than have the wrong flange arrive.

Frequently asked questions

What does SCRD mean on a flange?

SCRD is the abbreviation for screwed. An SCRD flange has an internal thread, so it can be fitted to threaded pipe without welding.

Do screwed flanges need welding?

No. A screwed flange fits onto a pipe with a matching external thread, so the joint can be made without welding, which is useful where welding isn’t practical.

Should I choose BSPT or NPT screwed flanges?

Choose the thread that matches your pipe or fitting. BSPT is the British standard taper thread and NPT is the American standard taper thread, and they aren’t the same, so don’t assume one will fit the other.

Which standards and ratings do your screwed flanges follow?

We hold EN1092-1 PN16 screwed flanges, which are type 13 in the standard, and ANSI B16.5 150LB screwed flanges, including some listed as RF bossed.

Contact Anglo Stainless for more information

Our screwed flanges are available in 316. If you’d like us to confirm the grade and thread for your size, contact us and a member of our team will be glad to help. You can also request our brochure using the form below.