Wellhead and manifolds
API 6A flanges
Flanges for wellheads, christmas trees and manifolds to API 6A: type 6B for 2,000 to 5,000 psi with R or RX rings, type 6BX for 10,000 psi and up with BX rings, made to your size, rating and material class.
API 6A flanges join wellhead and christmas tree equipment, valves and manifolds. Type 6B flanges cover 2,000, 3,000 and 5,000 psi and seal with R or RX ring gaskets; type 6BX flanges cover 10,000, 15,000 and 20,000 psi, and large bores at lower ratings, and seal with BX rings. We supply weld neck, threaded, blind, test and adapter flanges to API 6A dimensions in AISI 4130 and other alloy steels, made to the material class, temperature class and PSL on your order.
6B and 6BX
| Type | Rated working pressure | Nominal sizes | Ring gasket | Make-up |
|---|---|---|---|---|
| 6B | 2,000 psi | 2-1/16 to 21-1/4 in | R or RX | Standoff between faces |
| 6B | 3,000 psi | 2-1/16 to 20-3/4 in | R or RX | Standoff between faces |
| 6B | 5,000 psi | 2-1/16 to 11 in | R or RX | Standoff between faces |
| 6BX | 2,000 and 3,000 psi | 26-3/4 and 30 in | BX | Face to face |
| 6BX | 5,000 psi | 13-5/8 to 21-1/4 in | BX | Face to face |
| 6BX | 10,000 psi | 1-13/16 to 21-1/4 in | BX | Face to face |
| 6BX | 15,000 psi | 1-13/16 to 18-3/4 in | BX | Face to face |
| 6BX | 20,000 psi | 1-13/16 to 13-5/8 in | BX | Face to face |
Size ranges as listed in API 6A. The bolt circle, bolt size and ring number for each size and rating come from the API 6A tables.
Flange types
| Type | What it is | Used for |
|---|---|---|
| Weld neck | Tapered hub butt-welded to the pipe, bored to the pipe bore | Manifolds, flowlines and spools |
| Threaded | Line pipe or tubing thread in the hub | Lower-pressure 6B connections where a thread suits the service |
| Blind | Solid flange closing an outlet | Closing spare outlets and dead ends |
| Test | Blind flange with a tapped port | Pressure testing through the port |
| Adapter | Two different end connections on one body | Joining two sizes, ratings or flange types |
Where a joint is opened often, a clamp hub connection makes up faster than a flange, and in manifolds studded blocks save the length of a flanged hub.
Material, classes and PSL
Flanges are forged from AISI 4130 or other alloy steels and quenched and tempered to the API 6A material designation the size and rating need, such as 60K or 75K minimum yield. Each order also states:
| Item | What it sets | Example |
|---|---|---|
| Material class | Service: AA to CC general service, DD to HH sour service | DD, sour service with carbon or low alloy steel |
| Temperature class | The temperature range the part is rated for | P, -20 to 180 °F (-29 to 82 °C) |
| PSL | Testing, examination and traceability, from PSL 1 to PSL 4 | PSL 2 or PSL 3 |
| Ring groove | Ring type and number | BX-152 for 2-1/16 in 10,000 psi |
For sour service, the hardness limits of NACE MR0175 / ISO 15156-2 apply, 22 HRC maximum for 4130.
Grooves are machined to API 6A dimensions and finish, and can be inlaid with corrosion-resistant alloy where your order asks for it. Match the ring material to the groove: the ring should be softer, so it is the ring that deforms. See ring gaskets.
Testing and marking
Flanges are tested and examined to the PSL on your order, and stamped with size, rated working pressure, ring number, material designation, material and temperature class, PSL and heat number. EN 10204 3.1 certificates give chemistry, heat treatment, tensile, impact and hardness results; 3.2 certificates are issued with your inspector.
We make these parts to the API 6A requirements your order calls up: material, dimensions, tests and marking as specified. We do not hold an API license, so the parts do not carry the API Monogram. If your specification requires monogrammed equipment, the quotation says so plainly.
Ordering
Weld neck flange, API 6BX, 3-1/16 in 10,000 psi, BX-154 groove, bored for 3 in XXS pipe, AISI 4130 60K, material class DD, temperature class P, PSL 2, EN 10204 3.1, 6 pcs
Test flange, API 6B, 2-1/16 in 5,000 psi, R-24 groove, 1/2 in NPT port, AISI 4130 60K, material class AA, temperature class U, PSL 1, EN 10204 3.1, 2 pcs
Frequently asked questions
What is the difference between 6B and 6BX flanges?
Type 6B flanges are used at 2,000, 3,000 and 5,000 psi, take R or RX ring gaskets and are made up with a standoff between the flange faces. Type 6BX flanges are used at 10,000 psi and above, and in large bores at 2,000 to 5,000 psi; they take BX rings and are made up face to face.
Can an API 6A flange bolt to an ASME B16.5 flange?
Some 6B flanges share bolt circles and ring grooves with ASME B16.5 Class 900 and 1500 flanges in certain sizes, but the ratings, materials and design rules differ. Join them only where your engineer has checked the specific pair; otherwise use an adapter flange made for the purpose.
What is a test flange?
A blind flange with a tapped port, used to pressure test a wellhead section or a manifold through the port. The port size and thread are made to your order.
Which material designation do I need?
API 6A sets minimum yield strengths for body and flange materials, such as 60K and 75K. The higher ratings and larger sizes need the stronger material. Tell us the size and rating, and we state the designation we will supply, or give us the one your specification calls for.