AWWA Class B to API 6BX 20K
Piping Flanges Across the
Full Pressure Spectrum
A reference for the full pressure range. Class 125LW lightweight for waterworks, ASME B16.5 through Class 2500 for industrial process, and API 6A and 6BX up to 20,000 psi for wellhead service. Carbon, stainless, alloy, and exotic material families covered in one place.
The Spectrum
Every Class, One Reference
Lightweight
86 - 300 PSI
Class 125LW, AWWA C207 B/D/E/F. Waterworks, cooling loops, large diameter up to 144".
Standard
150 - 600 Class
ASME B16.5 and B16.47. The industrial workhorse range. Process piping, refining, utilities.
High Pressure
900 - 2500 Class
Heavy-wall ASME for steam, high-temp hydrocarbon, and critical service.
API Service
2K - 20K PSI
API 6A and 6BX for wellhead, BOP, and drilling. RTJ facings with proper ring gaskets.
7
Pressure Classes Covered
AWWA + ASME + API
Standards Referenced
What's Covered
Flanges, Fittings and Non-Standard Work
The flange types, fittings and custom work that show up on a piping spec.
Flanges
Weld neck, blind, slip-on, threaded, socket weld, lap joint, reducing, orifice, spectacle blind, plate, long weld neck. 1/2" to 144" NPS. Class 125LW through 2500.
- ✓ASME B16.5 & B16.47
- ✓AWWA C207 & C228
- ✓API 6A & 6BX
- ✓DIN & EN 1092-1
Pipe Fittings
Elbows, tees, reducers, caps, couplings, unions, and specialty fittings. Butt-weld, socket-weld, and threaded for every service condition.
- ✓ASME B16.9 & B16.11
- ✓Schedule 10 through XXH
- ✓Seamless & welded
- ✓Hot induction bends
Custom Machining
Non-standard bores, overbore flanges, special facings, and tight-tolerance work. Quoted from a drawing or a spec.
- ✓Ring-type joint grooves
- ✓Specialty facings and bore work
What Are Alloy Piping Flanges?
"Alloy" is a blanket term for material grades that don't fall neatly into the carbon or stainless steel categories. Most nickel alloys land here: think Hastelloy, Inconel, Incoloy, and Monel, along with other commercially available materials like aluminum, titanium, copper, and bronze. Alloy flanges and fittings are made to industry standard specifications. For high nickel alloys specifically, ASTM B564 is the primary spec to know. These materials shine in applications where corrosion resistance or temperature extremes are a concern: corrosive processing environments, refineries, pressure vessel work, and similar demanding service conditions. For a closer look at commonly specified alloys, see the Texas Flange alloy flanges page.
What About High Yield Carbon Piping Flanges?
High yield carbon steel is essentially a heat-treated version of standard carbon steel, processed to significantly raise its yield strength, which is the point at which the metal starts to permanently deform under stress. The governing specifications are A694 and MSS SP-44, which cover grades F42 through F70. These piping flanges mate and weld to high yield pipe grades X42 through X70. You'll typically see these flanges specified in higher-pressure, higher-temperature applications, usually Class 600 and above, situations where mild carbon steel just isn't rated for the job requirements. More on high yield flanges is on the Texas Flange high yield flanges page.
Standards & Compliance
Built to Code. Documented.
Each standard sets its own dimensions, pressure ratings, materials and marking rules.
ASME B16.5
Pipe Flanges 1/2" - 24"
ASME B16.47
Large Diameter 26" - 60"
AWWA C207
Steel Pipe Flanges 4" - 144"
API 6A / 6BX
Wellhead & Drilling Equipment
ANSI B16.1
Cast Iron Class 125, 250
DIN / EN 1092
European PN 6 - PN 400
MSS SP-44
High Yield F42 - F70
NACE MR0175
Sour Service Materials
Reference Coverage
What This Resource Covers
Full Pressure Range
Most flange references cover one slice of the curve. This one covers AWWA Class B at 86 psi through API 6BX 20K, so a project that crosses pressure ranges does not have to cross multiple reference sites.
Material Traceability
Mill test reports tie a flange to its heat number. EN 10204 3.1 and 3.2 are the usual certification levels for industrial piping.
Pressure-Temperature Context
Class is not pressure. The standards reference pages cross-reference class to derated pressure at service temperature using the ASME B16.5 rating tables for each material group, so spec selection lines up with duty.
Domestic and Import Background
Domestic-content rules such as BAA, BABA and AIS are explained alongside imported material options in the resources section.
Specialty Metallurgy
Duplex, super duplex, Inconel, Monel, Hastelloy, chrome-moly, and high yield carbon are all covered in the materials section, with notes on where each one earns its premium.
Custom and Non-Standard
Overbore, special facings, RTJ grooves, and weld overlay sit outside the standard catalog and are quoted from a drawing.
Industries
From Wellhead to Water Main
Different industries, different specs.
Technical Resources
Engineering Reference
Spec sheets are fine. Understanding why the spec matters is better. These guides explain the why behind the spec.
Flange Types Guide
Weld neck vs. slip-on vs. blind. Application criteria, pros and cons.
Access Resource →
Pressure-Temperature Ratings
ASME B16.5 P-T tables for common materials. How class translates to PSI at temperature.
Access Resource →
Bolt Torque Reference
Stud bolt sizes and torque references by pressure class.
Access Resource →
Material Grade Guide
A105 vs. F304 vs. F316 vs. F11. Which grade for which service.
Access Resource →
Corrosion Prevention
Coatings, galvanizing, and material selection for corrosive environments.
Access Resource →
Flange Dimension Tables
ASME B16.5 dimensional data. OD, bolt circle, bolt holes, thickness by class.
Access Resource →
Common Questions
Frequently Asked
What pressure range do piping flange standards actually cover end to end?+
AWWA C207 Class B (86 psi) through Class F (300 psi) and lightweight Class 125LW cover the waterworks side. ASME B16.5 covers Class 150 through Class 2500 for industrial process. API 6A and 6BX cover 2K through 20K psi for wellhead service. The full span is documented across the standards reference pages.
Are lightweight waterworks and high-pressure oilfield flanges from the same family?+
No. AWWA C207 lightweight and API 6A high-pressure are entirely separate standards with different dimensional, material, and pressure-rating rules. They often share a vendor ecosystem, but the engineering for each is independent.
What size range do these standards cover?+
ASME B16.5 covers 1/2 inch through 24 inch NPS. ASME B16.47 picks up at 26 inch and runs through 60 inch in Series A and Series B. AWWA C207 covers 4 inch through 144 inch for steel water-service flanges. Larger custom diameters exist but are project-specific and quoted case by case.
What are Buy American flange requirements?+
Federally funded projects can carry domestic-content rules such as the Buy American Act (BAA), Build America, Buy America (BABA) and American Iron and Steel (AIS). For iron and steel products like flanges, these generally require every manufacturing step, from the initial melting through coating, to happen in the United States, with documentation that traces the material origin. PSL-3 and PSL-4 API material adds further NDE and impact testing requirements.
What is a mill test report (MTR) on a flange order?+
A mill test report ties each flange back to its original heat number with chemistry and mechanical properties. EN 10204 3.1 and 3.2 are the typical certification levels for industrial piping. Standard practice is for MTRs to ship with the material rather than be chased afterward.
How are lead times set on piping flange orders?+
Lead time depends on size, class, material, and any custom machining. Standard B16.5 carbon and stainless typically move faster than large-diameter A694 or API 6BX, which often involve mill production schedules. Project-specific timelines are confirmed at the quote stage.
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