Ring Flanges, Ring Joints and Ring Blinds
AWWA C207 Class B, D, E and F waterworks flanges. ASME B16.5 and B16.47 ring type joint faces. Ring spacers, ring blinds and lap joint backing rings. Sizes 1/2 inch through 203 inches.
Start here
"Ring flange" means three different things
More flange orders go wrong over this word than almost any other. Before anything else, work out which family the job needs. All three come off the same shop floor at Texas Flange, but they are not substitutes for each other.
1. The flat ring flange
A plain steel ring, no hub, slipped over the pipe and welded front and back. This is the waterworks flange, defined by AWWA C207 in Class B and Class D. Cheap, simple, and rated for water rather than for hydrocarbons.
2. The ring type joint flange
A flange with a machined groove that takes a solid metal ring gasket. The seal is metal to metal and it works at pressures a compressed sheet gasket cannot approach. This is the refinery, pipeline and wellhead meaning.
3. The loose ring
Rings that are not flanges at all but go between them. Ring spacers, ring blinds, spectacle blinds, paddle blanks and the loose backing ring behind a lap joint stub end.
Waterworks
AWWA C207, the four classes
AWWA C207 is the steel flange standard for waterworks service. It defines four classes, and the first thing to know is that only two of them are ring flanges. Class B and Class D are flat rings. Class E and Class F are hub flanges.
The ratings are water working pressures, and they are modest next to the ASME classes, because a buried water main is not a refinery line. The economy is the point.
| Class | Style | Water working pressure |
|---|---|---|
| B | Ring, flat, no hub | 86 psi |
| D | Ring, flat, no hub | 150 psi, and 175 psi in the smaller sizes |
| E | Hub | 275 psi |
| F | Hub | 300 psi |
Class D is the workhorse. Its drilling follows the ASME B16.1 Class 125 template, which is why a C207 Class D flange so often bolts to a Class 150 pattern. That convenience is also the trap: shared drilling is not shared rating or shared thickness.
High pressure
Ring type joint, where the seal is metal
A ring type joint flange has a precision groove machined into the face. A solid metal ring sits in it, and as the bolts are pulled up, the ring is forced into the groove walls until it yields locally and seals. There is no soft gasket to blow out and nothing to creep, so the joint holds where a sheet gasket would fail.
Type R
The standard ring, supplied oval or octagonal, seating in the conventional groove of an ASME B16.5 or API 6B flange. Octagonal seals better. Oval will fit an older rounded groove.
Type RX
A pressure-energized ring for API 6B flanges. It uses the same groove as an R ring but stands taller, so internal pressure works to tighten the seal rather than to break it.
Type BX
For API 6BX flanges at 5,000 through 20,000 psi. The flange faces make contact, and a vent hole through the ring equalises pressure so the seal energises correctly.
Ring joint facing is not available in Class 150. Under ASME B16.5 it starts above Class 150, because the groove needs flange thickness and bolt load that Class 150 does not have. On ASME B16.47 Series A the facing is defined over part of the class range rather than all of it. Confirm against the current edition before specifying.
The gaskets themselves are covered by ASME B16.20, which defines the ring numbers, dimensions and materials. The ring number, the groove and the flange all have to agree. Getting an R-45 into a groove cut for an R-46 is not a field adjustment.
Product range
What we make
Ring and plate flanges
- AWWA C207 Class B and Class D ring flanges
- AWWA C207 Class E and Class F hub flanges
- Plate flanges cut from 1/4 inch through 8 inch plate
- Flat face ring flanges in carbon, stainless and alloy
- Special ring flanges and custom drilling patterns
- Large diameter rings through 203 inches
Ring type joint
- ASME B16.5 RTJ faced flanges, above Class 150 through Class 2500
- ASME B16.47 Series A RTJ flanges in the defined classes
- API 6A, 6B and 6BX ring groove flanges, 2K through 20K
- Groove machining and re-machining on existing flanges
- Ring gaskets to ASME B16.20 in R, RX and BX
Spacers, blinds and backing rings
- Spectacle blinds, also called figure eight blinds
- Paddle blinds and paddle spacers
- Ring spacers and line blinds
- Lap joint flanges and loose backing rings
- Orifice flanges and orifice plate rings
- Spacers to set a specific face to face gap
Materials
- Carbon steel, A105, A350 LF2 and LF3, A694, SA-516-70, A36
- Chrome alloys, A182 F1, F5, F9, F11, F22 and F91
- Stainless, A182 F304, F316, dual grades, H and L variants
- Duplex, F51 and F53
- Nickel alloys, Hastelloy, Inconel, Incoloy and Monel
- Aluminum, copper alloys and titanium
Quoting
What to put on the RFQ
Because the word ring carries three meanings, the first line of a ring flange enquiry has to disambiguate. After that it is straightforward.
- Which family, flat ring flange, ring type joint face, or loose ring, spacer or blind.
- Nominal size and the governing standard, AWWA C207 Class D, ASME B16.5 Class 600, API 6BX 10K, and so on.
- Facing, flat face, raised face, or the ring groove and its ring number.
- Drilling template, if it has to mate to something that is not the standard pattern for that class.
- Material grade and specification.
- Thickness, on plate and ring work, and the bore.
- Design pressure, temperature and fluid.
- Certification, MTRs, spec revision, third party witness, and any domestic origin requirement.
If you are matching an existing flange and are not sure what it is, measure the outside diameter, the bolt circle, the hole count, the hole size and the thickness, and send those. That is usually enough for us to identify the pattern.
Common questions
What is a ring flange?
It depends who is asking. In waterworks, a ring flange is a flat steel ring with no hub, slipped over the pipe and welded, as defined by AWWA C207 Class B and Class D. In refinery and pipeline work, a ring flange usually means a ring type joint flange, one with a machined groove that takes a metal ring gasket. A third use covers loose rings: ring spacers, ring blinds and lap joint backing rings. We supply all three families.
Does an AWWA C207 Class D ring flange bolt to an ASME Class 150 flange?
In many sizes the bolt template matches, because C207 Class D drilling follows the ASME B16.1 Class 125 pattern, which shares the Class 150 template. Matching the drilling is not the same as matching the rating or the thickness. Confirm both against the standards before you mate them, and check the gasket surface, since a flat ring face against a raised face needs attention.
Is ring type joint facing available in Class 150?
No. Under ASME B16.5, ring type joint facing starts above Class 150. The groove needs flange thickness and bolt load that Class 150 does not provide. If a Class 150 line needs a metal seal, the usual answers are a spiral wound gasket on a raised face or a step up in class.
What is the difference between an R, RX and BX ring gasket?
R is the standard ring, supplied oval or octagonal, and it seats in the conventional ring groove of an ASME or API 6B flange. RX is a pressure-energized design for API 6B flanges, the same groove but a taller ring that uses line pressure to tighten the seal. BX is for API 6BX flanges at the highest pressures, 5,000 through 20,000 psi, and it seals face to face with a vent hole through the ring. They are not interchangeable.
What is a spectacle blind?
Two discs on a common web, one solid and one open, shaped like a pair of spectacles. Spread the flanges, swing the plate, and the line is either positively blanked or fully open, with the position visible from the ground. It is heavier and more expensive than a paddle blind and it cannot be mislaid, which is the point.
How large can you make a ring flange?
We cut flat rings from plate 1/4 inch through 8 inch thick and machine rings through 203 inches. Past the published standard tables the job becomes a drawing, and we work to it.
Ring flanges, quoted fast
Texas Flange has supplied industrial pipe flanges out of Houston since 1986, including the plate and ring work that most flange houses treat as an afterthought.
Send the print, or send the size, class and grade. Texas Flange quotes quickly.
Request a QuoteOr call 281-484-8325 and ask for the ring flanges desk.