Tesco Steel & Engineering manufactures API flanges — high-pressure flanges built to American Petroleum Institute standards for wellhead, drilling, and oil & gas service. We supply API 6A Type 6B (ring-joint flanges to 2000/3000/5000 PSI) and API 6A Type 6BX (to 10,000 / 15,000 / 20,000 PSI), plus API 605 large-diameter flanges (Class 75 to 900). All use ring-joint (RTJ) faces with R, RX, or BX ring gaskets for metal-to-metal sealing at extreme pressure. A105, SS 304/316, Duplex, Monel, Inconel — NACE MR0175 capable. ISO 9001:2015 certified. Made in India.
API Flanges (6A / 6B / 6BX / 605)
Tesco Steel & Engineering manufactures the full API flange range — weld-neck and blind, in every API 6A 6B/6BX PSI rating and API 605 class — in carbon, stainless, duplex, and nickel alloys, NACE MR0175 compliant for sour service. Browse the complete range below, or see the flange dimensions charts.
API 6A Type 6B Weld Neck Flange
| API Type | Pressure Ratings | Ring Gasket | Typical Use |
|---|---|---|---|
| API 6A Type 6B | 2,000 / 3,000 / 5,000 PSI | R & RX (octagonal / pressure-energised) | Wellheads & pressure control up to 5,000 PSI |
| API 6A Type 6BX | 2,000* / 3,000 / 5,000 / 10,000 / 15,000 / 20,000 PSI | BX (pressure-energised) | High-pressure wellheads & trees (10k–20k PSI) |
| API 605 | Class 75 / 150 / 300 / 400 / 600 / 900 | Ring-joint | Large-diameter pipeline & equipment flanges |
*Type 6BX is used for larger bores at lower ratings where 6B sizes are not listed. 6B uses R/RX rings; 6BX uses BX rings — the two are not interchangeable.
| Criterion | API 6A Type 6B | API 6A Type 6BX |
|---|---|---|
| Pressure range | 2,000–5,000 PSI | 2,000–20,000 PSI (high pressure) |
| Ring gasket | R (octagonal) & RX (pressure-energised) | BX (pressure-energised, raised faces contact) |
| Face contact | Standoff between flange faces | Raised faces make metal-to-metal contact |
| Construction | Weld-neck & blind | Weld-neck & blind |
| Use | Standard wellhead pressure ratings | High & ultra-high-pressure service |
Select a specific API flange below for its detailed dimensions — weld-neck and blind flanges in every API 605 class and API 6A 6B/6BX PSI rating:
| API Flanges are available in the following specifications: | |
|---|---|
| Size | 1/2"NB to 56"NB |
| Class | 150#, 300#, 3000#, 6000#, 9000# |
| Sch (Schedule) | XS, XXS, STD & Schedule 20, 40, 80, 160 |
| Pressure Ratings | PN 1 - PN 400 |
| Stainless Steel API Flanges | ASTM A 182 F - 304 / 304H / 304L / 316 / 316H / 316L / 316Ti, 309, 310, 317L, 321, 347, 904L |
| Duplex Steel API Flanges | ASTM A 182 - F 51, F 53, F 55 |
| Alloy Steel API Flanges | ASTM A 182 - F5, F9, F11, F21, F22 & F91 |
| Carbon Steel API Flanges | ASTM A 105 |
| Low Temp. Carbon Steel API Flanges (LTCS API Flanges Flanges) | A 350 LF2 |
| Copper Nickel (Cu-Ni) API Flanges | C70600, 90/10, C71500, 70/30, C71640 |
| Nickel API Flanges | UNS N02200, UNS N02201 |
| Monel API Flanges | UNS N04400, UNS N05500, Alloy 20 |
| Inconel API Flanges | UNS N06600, UNS N06601, UNS N06625, UNS N08800, UNS N08810, UNS N08825 |
| Hastelloy API Flanges | UNS N10276, UNS N06022, UNS N10665, UNS N06455 |
| Titanium API Flanges | Gr. 1, Gr. 2, Gr. 3, DTH 3.7035, DTH 3.7055 |
| Other Services | Hot Dip Galvanized (GI) API Flanges Sand Blasting on API Flanges Shot Peening on API Flanges Epoxy Coating on API Flanges FBE Coating on API Flanges |
Full API 6A range — Type 6B to 5,000 PSI and Type 6BX to 20,000 PSI — for wellhead and pressure-control service.
Ring-joint faces with R, RX, or BX ring gaskets give a reliable metal-to-metal seal at extreme pressure.
Carbon, stainless, duplex, and nickel alloys, NACE MR0175 / ISO 15156 compliant for H₂S (sour) service.
Weld-neck and blind flanges across every API 6A 6B/6BX PSI rating and API 605 class.
Made to API 6A / API 605 with full traceability and EN 10204 3.1 MTC; API monogram capable on request.
Precision-machined ring grooves and faces for safe, leak-tight high-pressure service.
| Material | Properties | Typical Use |
|---|---|---|
| Carbon / Low-Alloy Steel | High strength (e.g. AISI 4130/4140, A105) | Standard wellhead & pressure-control bodies |
| SS 304 / 316 / 316L | Good corrosion resistance | Corrosive well fluids & surface equipment |
| Duplex 2205 / Super Duplex 2507 | High strength & chloride resistance | Offshore & sour-service wellheads |
| Monel 400 / Inconel 625/718 | Excellent in sour, marine & high-temp | HP/HT & highly corrosive wells (clad or solid) |
| Application | Use | Why API Flange |
|---|---|---|
| Wellheads & Christmas Trees | Surface pressure-control equipment | API 6A 6B/6BX to 20,000 PSI |
| Drilling Equipment | BOP stacks, adapters & spools | High-pressure RTJ connections |
| Offshore & Subsea | Topside & subsea pressure systems | Duplex / Inconel; NACE sour |
| High-Pressure Pipelines | Trunk & flow lines | API 605 large-diameter flanges |
| Refinery & Gas Plants | HP process & gas service | Ring-joint high-pressure sealing |
| Frac & Well Service | High-pressure pumping & manifolds | 6BX 15k–20k PSI ratings |
| LNG & Gas Processing | HP gas equipment | Robust metal-to-metal seal |
| Petrochemical | HP reactors & lines | Sour-service alloys |
Q1. What are API flanges?
API flanges are flanges made to American Petroleum Institute standards for high-pressure oil & gas service — mainly wellheads, Christmas trees, drilling equipment, and high-pressure pipelines. They are rated for much higher pressures than ASME B16.5 flanges and use ring-joint (RTJ) faces with metal ring gaskets. The main families are API 6A (Type 6B and 6BX) and API 605.
Q2. What is the difference between API 6A Type 6B and Type 6BX?
Type 6B flanges are rated up to 5,000 PSI (2000/3000/5000) and use R or RX ring gaskets, with a standoff between the flange faces. Type 6BX flanges are for higher pressure — up to 20,000 PSI — use BX ring gaskets, and have raised faces that make metal-to-metal contact. The two types and their ring gaskets are not interchangeable.
Q3. What pressure ratings are available?
API 6A Type 6B: 2,000, 3,000, and 5,000 PSI. API 6A Type 6BX: 2,000, 3,000, 5,000, 10,000, 15,000, and 20,000 PSI. API 605: Class 75, 150, 300, 400, 600, and 900. Each rating has its own dimensions — select the specific flange in the range list above.
Q4. What is API 605?
API 605 (now largely superseded by ASME B16.47 / MSS SP-44 but still specified) covers large-diameter steel flanges in Class 75, 150, 300, 400, 600, and 900. It is used for big-bore pipeline and equipment flanges where the ASME B16.5 range stops. We supply API 605 weld-neck and blind flanges in all classes.
Q5. What ring gaskets do API flanges use?
API 6B flanges use R (oval or octagonal) and RX (pressure-energised) ring-joint gaskets; API 6BX flanges use BX (pressure-energised) rings. The ring type matches the flange type and ring groove, and a new ring gasket should be used at every make-up for a reliable metal-to-metal seal.
Q6. Are API flanges available for sour (H₂S) service?
Yes. API flanges are supplied in NACE MR0175 / ISO 15156 compliant carbon, low-alloy, stainless, duplex, and nickel-alloy materials with controlled hardness for sour (H₂S) wellhead and pipeline service. Specify the H₂S, CO₂, chloride, and temperature conditions so the correct material and grade are selected.
Q7. How do API flanges differ from ASME B16.5 flanges?
ASME B16.5 covers general piping flanges to Class 2500. API flanges are purpose-built for the much higher pressures of wellhead and drilling service (to 20,000 PSI), almost always with ring-joint faces, and are dimensioned and rated to API 6A / 605 rather than ASME B16.5. They are not interchangeable with B16.5 flanges.
Q8. Can API flanges be supplied with API monogram and certification?
Yes. We manufacture to API 6A / API 605 with full material traceability and EN 10204 3.1 material test certificates, and can supply API-monogrammed product on request. Send your type (6B/6BX/605), PSI rating, size, material, and service for a quote.