Flanges
Every Flange Type. Every Pressure Class.
Class 125LW for 86 psi waterworks. ASME B16.5 process flanges from 150 through 2500. ASME B16.47 Series A and B for large diameter. API 6A and API 6BX wellhead service all the way to 20,000 psi. The standards reference covers the full pressure range; Texas Flange supplies into projects across it.
Catalog
Every Flange Type
The twelve flange types below cover roughly 95 percent of what shows up on a piping isometric. The other 5 percent is custom, covered on the custom machining page.
Weld Neck
The workhorse for high pressure, high temperature, and cyclic service. Long tapered hub transfers stress from the flange ring into the pipe wall. Specified for most process and pipeline work.
Slip-On
Slides over the pipe and fillet welds on both sides. Lower cost than weld neck, easier alignment, but lower fatigue rating. Common on utility and lower-pressure process lines.
Blind
Solid flange used to close the end of a pipe, valve, or vessel nozzle. Frequently drilled and machined later for instrumentation. Stocked in all standard classes and materials.
Threaded
NPT threaded bore for piping that cannot be welded. Common on small bore utility lines, instrument connections, and certain hazardous-area piping where welding is restricted.
Socket Weld
Pipe drops into a counterbore and is fillet welded on the outside. Used on small bore high-pressure lines typically 2 inch and below. Sized to ASME B16.5.
Lap Joint
Used with a stub end so the flange can rotate for bolt-hole alignment. Common in stainless and exotic alloy systems where the flange itself can be carbon to save cost.
Reducing
Single flange that reduces from one size to another without an additional reducer fitting. Useful when space is tight or schedule is critical.
Orifice
Paired flanges with tapped pressure connections for orifice plate flow measurement. Stocked in weld neck and slip-on configurations across standard classes.
Spectacle Blind
Figure-8 plate with a blind on one end and a spacer ring on the other. Pivots between positions for positive isolation during maintenance and turnarounds.
Long Weld Neck
Extended neck used as a nozzle on pressure vessels and column trays. Bored to match vessel wall thickness rather than standard pipe schedule.
Plate
Flat plate flange machined from rolled plate. Cost-effective for large-diameter, lower-pressure service such as water and HVAC distribution.
Ring-Type Joint
RTJ facing with metal ring gasket for high-pressure and high-temperature sealing. Standard on API 6A wellhead components and many B16.5 Class 900 and above applications.
Lightweight Families
Two Separate Lightweight Standards
Lightweight steel flanges live in two distinct standard families that are frequently confused. ASME B16.1 Class 125LW is a lightweight steel flange built to the B16.1 cast-iron dimensional pattern for bolt-up to legacy cast-iron systems. AWWA C207 is a separate waterworks specification with its own pressure classes (B, D, E, F) and its own dimensional rules. They are not the same standard and they are not interchangeable on every fit.
ASME B16.1 Class 125LW
The lightweight (LW) variant of the B16.1 cast-iron flange family, produced in steel instead of cast iron. Same outside diameter, bolt circle, and bolt hole pattern as B16.1 Class 125 cast iron, which is the point: it bolts directly to legacy cast-iron valves, pumps, and existing flanges without an adapter. Common on retrofit waterworks and HVAC distribution where the mating component is cast iron.
AWWA C207 Steel Pipe Flanges
The dedicated waterworks specification for steel ring and hub flanges from 4 inch up through 144 inch. AWWA organizes pressure into lettered classes rather than the ASME pound-class system. Drilling on Class B, D, and E up through 24 inch matches B16.1 Class 125, which is why C207 ties into 125LW retrofit work, but the underlying standard is independent.
AWWA C207 Pressure Ratings
Above 24 inch and for Class F, drilling should be confirmed before ordering since the B16.1 alignment no longer holds. The full AWWA C207 reference, including stainless counterpart C228, is on the AWWA flanges page.
Process
ASME B16.5 and B16.47
The two standards that cover the bulk of refinery, petrochemical, midstream, and general process piping. B16.5 handles 1/2 inch through 24 inch. B16.47 picks up at 26 inch and runs through 60 inch in Series A and Series B, each with its own dimensional family.
ASME B16.5 - 1/2 in through 24 in
Pressure classes 150, 300, 400, 600, 900, 1500, and 2500. Standard facings include raised face, flat face, ring-type joint, and tongue-and-groove. Materials from A105 carbon up through stainless, low-temp, and chrome-moly alloy steels.
B16.5 reference ->ASME B16.47 - 26 in through 60 in
Series A (formerly MSS SP-44) and Series B (formerly API 605) cover large diameter. Different outside diameters and bolt patterns between the two, so always confirm which series the line was originally designed to.
B16.47 reference ->Pressure-temperature ratings drop as temperature rises. As a typical example from ASME B16.5 Table 2, a Group 1.1 Class 300 carbon steel flange rated at 740 psi at ambient derates toward the mid-500 psi range by 700F. The B16.5 tables are the source of truth; class alone never equals working pressure once temperature is in the equation. Texas Flange can provide the rating curves on request.
High Pressure
API 6A and API 6BX
Wellhead service, BOP stacks, choke and kill manifolds, and surface production equipment. The 6A specification covers everything from 2,000 psi working pressure through 20,000 psi, with the 6BX dimensional family taking over at the higher pressure tiers where the standard 6B geometry runs out of safety margin.
Working Pressure
Documentation
Product Specification Levels PSL-1 through PSL-4, with PSL-3 and PSL-4 carrying additional NDE and impact testing requirements. NACE MR0175 / ISO 15156 compliance for sour service.
RTJ facings only. Ring gaskets are typically BX style on 6BX and R style on 6B. Mixing them up is a bad day for everyone involved.
API 605 is the older large-diameter specification still referenced on some legacy projects. It is now folded into ASME B16.47 Series B for new construction, though we still see 605 callouts on replacement parts for older facilities.
Materials
Specifications and Materials
Material selection drives more headaches than dimensional selection. The list below covers the bulk of what appears on industrial line lists. Less common grades are covered on the individual material reference pages.
Carbon and Low Temp
A105 - standard carbon for ambient and moderate temperature.
A350 LF2 - low-temperature carbon, impact tested to -50 F.
A694 F52 through F70 - high-yield pipeline grades for transmission service.
Carbon steel detail ->Stainless
F304 / F304L - general-purpose austenitic stainless.
F316 / F316L - molybdenum-bearing for improved chloride resistance.
F321, F347 - stabilized grades for elevated temperature.
Stainless detail ->Alloy
F11 (1-1/4 Cr) - moderate elevated temperature service.
F22 (2-1/4 Cr) - hydrogen and high-temp service.
F91 (9 Cr) - high-pressure steam and power generation.
Alloy steel detail ->Exotic
Duplex 2205, Super Duplex 2507 - offshore and sour service.
Inconel 625, 825 - high-temperature corrosion resistance.
Hastelloy C276, Monel 400, Titanium Gr 2 - specialty service.
Exotic alloys detail ->Technical Resources
Read Before You Specify
Reference content from the Texas Flange technical library. Useful when reviewing a line list or when the standard in question is not the one you specify every day.
- The Complete Guide to Flanges - types, facings, ratings, and selection logic.
- AWWA C207 Reference - lightweight pressure classes and drilling.
- ASME B16.5 / B16.47 Reference - dimensions, facings, and material groups.
- Pressure-Temperature Calculator - find the derated pressure at your service temp.
Send the Line List
Email a BOM, an isometric, or a take-off to Texas Flange for pricing against current stock and confirmed lead times on mill-ship items.