Valiol Trading supplies the complete range of certified pipe flanges to QatarEnergy contractors, Ras Laffan Industrial City operators, and offshore projects — from standard ASME B16.5 Class 150 slip-on flanges to API 6A wellhead flanges at 15,000 PSI, with full MTC 3.1 documentation and same-week Doha delivery.
Valiol Trading is a certified pipe flanges supplier headquartered in Doha, Qatar. We supply the complete piping flange range — weld neck, slip-on, blind, socket weld, threaded, lap joint, orifice, spectacle blinds, and large-diameter flanges — across all pressure classes (150# to 2500# and API 6A wellhead ratings) in every material grade from standard carbon steel to super duplex and nickel alloy.
Every ASME B16.5, B16.47, and API 6A flange type required for Qatar's oil & gas, petrochemical, and construction projects — from standard weld neck flanges to spectacle blinds and API 6A wellhead flanges.
The strongest and most reliable flange type. A tapered hub transmits stress from the flange to the pipe, making it the preferred choice for Qatar's high-pressure, high-temperature, and cyclic-loading oil & gas and power generation applications.
The pipe slides through the flange bore and is fillet-welded inside and out. Lower cost and easier to align than weld neck. Suitable for lower-pressure, non-cyclic service in Qatar utility, water, and general process piping.
A solid disc to close and blank off the end of a pipe, nozzle, or pressure vessel. Used for Qatar hydrostatic testing, future expansion points, and permanent terminations. All pressure classes and materials available in Doha stock.
Small-bore flange for NPS ½″ to 3″. The pipe inserts into the socket and is fillet-welded externally. Better than threaded for higher-pressure Qatar instrument and process connections where leak-tightness is critical.
Screws onto NPT-threaded pipe — no welding required. Suitable for low-pressure, low-temperature utility and instrument connections on Qatar project sites. Available ½″ to 4″ NPS in Class 150 to 2500.
Used with a stub end — the flange slides freely over the pipe and backs up the stub end lap. Allows bolt hole alignment without rotating the pipe. Used for dissimilar metal connections and frequent dismantling in Qatar process plants.
A figure-8 combining a blind disc and open ring spacer — rotated 180° to select blind or open position. Used for positive process isolation during Qatar plant turnarounds and maintenance. Mandatory on many QatarEnergy piping specifications.
Matched pair of flanges with precision-bored tappings for differential pressure measurement across an orifice plate. Supplied in pairs with jack screws and tapping plugs. ASME B16.36 and AGA-3. For Qatar flow metering applications.
Forged flanges for Qatar wellhead, Xmas tree, and manifold connections up to 15,000 PSI WP. Ring type joint (6B/6BX groove). ASTM A182 F22, F316, and Inconel alloy grades. For Qatar upstream oil & gas installations.
Standard for Class 150–900. Spiral wound or sheet gasket sits on raised surface.
Class 900+ and API 6A. Solid metal ring seated in machined groove. Metal-to-metal seal.
Used with cast iron flanges. Full-face gasket spans entire flange face. Class 150 & 300.
Boss on one, recess on other. Gasket fully contained — improved sealing integrity.
Precision interlocking. Superior gasket containment. Used in heat exchangers & pressure vessels.
Detailed specification tables for all flange types, pressure classes, bolt patterns, gasket types, and bolting. All products available with EN 10204 3.1 MTC and same-week Qatar delivery. Contact us for pricing and stock confirmation.
Complete reference for all ASME B16.5, B16.47, B16.48, and API 6A flange types supplied from Qatar stock — including size range, pressure class, face type, end connection, and typical Qatar application.
| Flange Type | Standard | Size Range (NPS) | Pressure Class | Face Type | Pipe End Connection | Construction | Qatar Application |
|---|---|---|---|---|---|---|---|
| Weld Neck (WN) | ASME B16.5 | ½″ – 24″ | 150# / 300# / 600# / 900# / 1500# / 2500# | RF / RTJ / FF | Butt Weld (BW) | Forged | HP/HT Qatar process, refinery, pipelines |
| WN — Large Diameter | ASME B16.47 Series A & B | 26″ – 60″ | 75# / 150# / 300# / 400# / 600# / 900# | RF / RTJ / FF | Butt Weld (BW) | Forged / Fabricated | Qatar large-diameter pipelines, North Field |
| Slip-On (SO) | ASME B16.5 | ½″ – 24″ | 150# / 300# / 600# | RF / FF / RJ | Fillet Weld (int. & ext.) | Forged | Qatar general service, water, utilities |
| Blind (BL) | ASME B16.5 / B16.47 | ½″ – 60″ | 150# / 300# / 600# / 900# / 1500# / 2500# | RF / RTJ / FF | N/A — bolted end closure | Forged / Fabricated | Qatar line termination, hydro-test, future connections |
| Socket Weld (SW) | ASME B16.5 | ½″ – 3″ | 150# / 300# / 600# / 900# / 1500# / 2500# | RF / FF | Socket Weld (fillet ext.) | Forged | Qatar small-bore HP instrument & process |
| Threaded (TH) | ASME B16.5 | ½″ – 4″ | 150# / 300# / 600# / 900# / 1500# / 2500# | RF / FF | NPT / BSP thread | Forged | Qatar LP utility, instrument gauge connections |
| Lap Joint (LJ) | ASME B16.5 | ½″ – 24″ | 150# / 300# / 600# / 900# / 1500# / 2500# | Flat (mates with stub end) | Slips over stub end | Forged CS | Qatar dissimilar metal, frequent dismantling |
| Orifice Flange (OR) | ASME B16.36 | 1″ – 16″ | 150# / 300# / 600# / 900# / 1500# / 2500# | RF / RTJ | Butt Weld (BW) | Forged — in pairs | Qatar flow measurement, DP metering |
| Spectacle Blind (Figure-8) | ASME B16.48 | ½″ – 36″ | 150# / 300# / 600# / 900# | RF | Between flanges | Plate — CS / SS / Duplex | Qatar process isolation, turnaround maintenance |
| Paddle Spacer & Paddle Blind | ASME B16.48 | ½″ – 36″ | 150# / 300# / 600# / 900# | RF | Between flanges | Plate — CS / SS / Duplex | Individual spacer or blind plate — Qatar isolation |
| Long Weld Neck (LWN) | ASME B16.5 | ½″ – 24″ | 150# / 300# / 600# / 900# / 1500# / 2500# | RF / RTJ | Butt Weld (BW) | Forged | Qatar pressure vessel nozzles, heat exchangers |
| API 6A Wellhead Flange | API 6A / 6B / 6BX | 1″ – 20″ | 2,000 / 3,000 / 5,000 / 10,000 / 15,000 PSI WP | RTJ (6B / 6BX groove) | Butt Weld / Flanged | Forged A182 F22/F316/Inconel | Qatar wellheads, Xmas trees, manifolds |
Standard ASME B16.5 flange bolt hole dimensions and stud bolt sizes for Class 150 and Class 300 flanges. Reference for Qatar project procurement and material take-off preparation.
| NPS (in) | Flange OD (mm) | Cl.150 Bolt Circle (mm) | Cl.150 No. Bolts | Cl.150 Bolt Dia. | Cl.300 Bolt Circle (mm) | Cl.300 No. Bolts | Cl.300 Bolt Dia. |
|---|---|---|---|---|---|---|---|
| ½″ | 88.9 | 60.5 | 4 | ½″ | 66.7 | 4 | ⅝″ |
| ¾″ | 98.6 | 69.9 | 4 | ½″ | 82.6 | 4 | ⅝″ |
| 1″ | 108.0 | 79.4 | 4 | ½″ | 88.9 | 4 | ⅝″ |
| 1½″ | 127.0 | 98.4 | 4 | ½″ | 114.3 | 4 | ¾″ |
| 2″ | 152.4 | 120.7 | 4 | ⅝″ | 127.0 | 8 | ⅝″ |
| 3″ | 190.5 | 152.4 | 4 | ⅝″ | 168.3 | 8 | ¾″ |
| 4″ | 228.6 | 190.5 | 8 | ⅝″ | 200.2 | 8 | ¾″ |
| 6″ | 279.4 | 241.3 | 8 | ¾″ | 269.9 | 12 | ¾″ |
| 8″ | 342.9 | 298.5 | 8 | ¾″ | 330.2 | 12 | ⅞″ |
| 10″ | 406.4 | 362.0 | 12 | ⅞″ | 387.4 | 16 | 1″ |
| 12″ | 482.6 | 431.8 | 12 | ⅞″ | 450.9 | 16 | 1⅛″ |
| 16″ | 596.9 | 539.8 | 16 | 1″ | 571.5 | 16 | 1¼″ |
| 20″ | 762.0 | 685.8 | 20 | 1⅛″ | 723.9 | 20 | 1¼″ |
| 24″ | 914.4 | 812.8 | 20 | 1¼″ | 876.3 | 20 | 1½″ |
Maximum allowable pressure (bar) at various temperatures for ASME B16.5 flanges in ASTM A105 carbon steel — the most commonly specified material for Qatar oil & gas piping. Values reduce with increasing temperature. Consult ASME B16.5 for other materials.
| Temperature | Class 150 | Class 300 | Class 600 | Class 900 | Class 1500 | Class 2500 |
|---|---|---|---|---|---|---|
| –29°C to +38°C (Ambient) | 19.6 bar | 51.1 bar | 102.1 bar | 153.2 bar | 255.3 bar | 425.5 bar |
| 100°C (212°F) | 17.7 bar | 46.6 bar | 93.2 bar | 139.8 bar | 233.0 bar | 388.3 bar |
| 150°C (302°F) | 16.6 bar | 45.1 bar | 90.2 bar | 135.3 bar | 225.5 bar | 375.8 bar |
| 200°C (392°F) | 15.8 bar | 43.8 bar | 87.6 bar | 131.4 bar | 219.0 bar | 365.0 bar |
| 250°C (482°F) | 15.3 bar | 40.0 bar | 79.9 bar | 119.9 bar | 199.8 bar | 333.0 bar |
| 300°C (572°F) | 14.7 bar | 38.3 bar | 76.5 bar | 114.9 bar | 191.5 bar | 319.2 bar |
| 400°C (752°F) | 12.9 bar | 33.6 bar | 67.2 bar | 100.7 bar | 167.9 bar | 279.8 bar |
| 450°C (842°F) | 11.0 bar | 28.7 bar | 57.3 bar | 86.0 bar | 143.3 bar | 238.8 bar |
| 538°C (1000°F) | 5.1 bar | 13.4 bar | 26.8 bar | 40.3 bar | 67.1 bar | 111.8 bar |
Select the class based on design pressure, design temperature, and applicable Qatar piping class specification. Each step approximately doubles the pressure rating at ambient temperature.
General utilities, water, low-pressure steam, HVAC, Qatar fire protection
Medium-pressure Qatar process piping, refinery utility headers
Qatar oil & gas process, natural gas, North Field export pipelines
High-pressure Qatar process, HP steam, sour gas, wellhead tie-ins
Very HP Qatar gas, injection lines, supercritical steam, compressor discharge
Extreme HP service, chemical reactors, ultra-HP Qatar process applications
Choosing the correct flange material prevents premature failure and ensures regulatory compliance for Qatar's demanding service environments. This guide covers the most-specified flange grades for Qatar EPC and operator projects.
The default grade for the vast majority of Qatar process, utility, and oil & gas flanges in moderate service (–29°C to +425°C). Normalised for improved toughness. Paired with A193 B7 stud bolts. Low cost, widely available from Doha stock for same-week delivery.
High-yield carbon steel flanges for use with API 5L X65/X70 Qatar gas transmission pipelines. Significantly higher yield strength (448–483 MPa) than A105, allowing lighter-weight flanges in large-diameter North Field high-pressure pipeline applications.
Impact-tested at –46°C — mandatory when Qatar LNG or process temperatures fall below the –29°C lower limit of A105. Used for Qatar North Field LNG trains, propane, and low-temperature process lines. Always pair with A333 Gr.6 pipe and A420 WPL6 fittings.
Chrome-molybdenum alloy steel for Qatar elevated temperature service. F11 (1.25Cr-0.5Mo) to 540°C, F22 (2.25Cr-1Mo) to 580°C, F91 (9Cr-1Mo-V) to 650°C. Mandatory for Qatar power plant steam, HRSG, and Ras Laffan refinery high-temp circuits.
The standard SS flange grade for Qatar corrosive service — offshore piping, chemical lines, seawater, desalination, and pharmaceutical applications. The "L" low-carbon grade prevents sensitisation during welding. Available in full B16.5 size range from Doha stock.
Duplex F51 (2205) and super duplex F53 (2507) for Qatar offshore, high-chloride, and sour service. F51 gives PREN >35 with twice the strength of 316L. F53 PREN >40 for Qatar deepwater and subsea. NACE MR0175 compliant for North Field sour gas environments.
All flanges and gaskets supplied by Valiol Trading comply with the international standards required by QatarEnergy, Ras Laffan operators, and Qatar EPC engineering specifications.
Pipe Flanges ½″–24″, Class 150–2500. The primary Qatar flange standard. All types and materials in Doha stock.
Large-Diameter Flanges 26″–60″ NPS, Series A & B. For Qatar North Field and large-bore pipeline projects.
Spectacle Blinds, Spacers & Paddle Blinds ½″–36″ NPS. Qatar process isolation and turnaround maintenance.
Metallic Gaskets — Spiral Wound, Ring Type Joint (RTJ). The primary Qatar gasket standard for all classes.
Non-Metallic Flat Gaskets for flanged joints. CAF, PTFE, graphite sheet for Class 150–300 Qatar service.
Orifice Flanges for differential pressure flow measurement in Qatar process and metering applications.
Wellhead & Xmas Tree Flanges to 15,000 PSI WP. Qatar upstream oil & gas wellhead connections.
Ring Joint Flanges — 6B oval/octagonal groove, 6BX compact groove for Qatar wellhead pressure ratings.
Materials for H₂S sour service — North Field, offshore, and acid gas Qatar applications. Hardness controlled.
3.1 MTC standard on all Qatar orders. 3.2 witnessed by SGS/BV/Intertek for QatarEnergy EPC packages.
Steel Pipeline Flanges (also ASME B16.47 Series A). Large-bore Qatar pipeline flanges.
European PN-class flanges (PN 6–PN 400) for European-engineered equipment in Qatar projects.
Valiol Trading supplies certified flanges, gaskets, and bolting to every major sector of Qatar's energy and industrial economy — with full MTC 3.1 documentation and same-week Doha delivery.
API 6A weld neck flanges for Qatar wellhead and Xmas tree connections. A105/F22 flanges for production manifolds, separator vessels, and wellhead piping in QatarEnergy fields.
Class 150–2500 ASME B16.5 weld neck flanges in CS, alloy (F11/F22), and SS for crude distillation, vacuum distillation, hydrotreaters, reformers, and all Ras Laffan process piping.
A694 F65/F70 weld neck flanges for Qatar mainline gas and oil transmission. Spectacle blinds and paddle blinds for isolation during commissioning and maintenance on North Field pipeline block valves.
ASTM A182 F91 Class 900–2500 flanges for Qatar supercritical steam systems, main steam lines, hot reheat, and boiler feed piping in Qatar power and combined-cycle desalination plants.
AWWA C207 / ASME B16.5 Class 150 flanges and full-face gaskets for Qatar large-diameter seawater intake, reverse osmosis (RO), and water injection systems. Duplex flanges for seawater service.
Super duplex F53 and Inconel 625 flanges for Qatar FPSO topsides, subsea manifold pipework, riser systems, and offshore wellheads in NACE MR0175 sour service conditions.
PTFE-lined and SS 316L flanges, Kammprofile gaskets, and B8M bolting for aggressive chemical service — acid, chlorine, and corrosive media in Qatar Mesaieed petrochemical and chemical plants.
A350 LF2 cryogenic flanges with A320 L7 stud bolts for Qatar North Field LNG liquefaction train cold process piping at temperatures down to –196°C.
ASME B16.5 Class 150 slip-on and weld neck flanges with CAF or PTFE gaskets for HVAC, fire protection, gas distribution, and building services in Qatar infrastructure projects.
Key questions from Qatar procurement engineers and project managers sourcing flanges and gaskets for QatarEnergy and Ras Laffan projects.
Ask Our Engineers →ASME B16.5 covers pipe flanges in sizes NPS ½″ through 24″ and pressure classes 150 through 2500. This is the most common Qatar flange standard covering the vast majority of oil & gas and process piping applications at Ras Laffan, Mesaieed, and Doha project sites.
ASME B16.47 covers large-diameter flanges from NPS 26″ through 60″ in Series A (formerly MSS SP-44) and Series B (formerly API 605). Series A and B have different bolt circles and dimensions — they are not interchangeable. Always confirm Series A or B when specifying large-bore Qatar pipeline flanges.
A raised face (RF) flange has a flat circular face raised 1.6mm (Class 150/300) or 6.4mm (Class 600+) above the pipe flange face. A spiral wound or sheet gasket sits between the two raised faces and is compressed when bolts are tightened. RF is suitable for Class 150–900 in most standard Qatar service.
A ring type joint (RTJ) flange has a precision-machined groove in the flange face. A solid metal ring gasket (oval or octagonal) seats into this groove and creates a metal-to-metal seal. RTJ is used for Class 900 and above and all API 6A wellhead flanges — mandatory for high-pressure Qatar offshore, North Field, and sour gas service where absolute sealing integrity is required.
A spectacle blind (figure-8 blind) combines a solid blind disc and an open ring spacer on a single component — like a figure 8. Installed between two flanges, it is rotated 180° to select blind position (blocking flow — positive isolation) or open position (allowing flow).
Spectacle blinds are specified to ASME B16.48 and are mandatory on many QatarEnergy piping specifications for positive process isolation during turnarounds, maintenance, and equipment isolation at Ras Laffan and offshore Qatar facilities — providing visible, auditable, lockable isolation safer than relying on a valve alone.
Spiral wound gaskets are used with raised-face (RF) flanges in Class 150 through 2500. They are the most common gasket type in Qatar refinery and process piping — good sealing performance, reasonable cost, and reusable if undamaged. They require correct bolt load to achieve proper compression.
RTJ gaskets are used only with RTJ-faced flanges and are preferred for Class 900 and above, high-temperature steam, sour gas service, and wherever a highly reliable metal-to-metal seal is required. RTJ gaskets are not reusable — a new ring must be used each time the joint is opened. For critical Qatar oil & gas connections, specify RTJ at Class 600 and above — the cost difference is small compared to the risk of a process leak.
Yes. Valiol Trading supplies flanges pre-qualified and documented for QatarEnergy, its Ras Laffan subsidiaries, and Tier-1 EPC contractors operating in Qatar. We maintain relationships with flange manufacturers who carry QatarEnergy approvals and can provide full compliance documentation. For QatarEnergy EPC projects, we also support Approved Vendor List (AVL) registration and pre-qualification submissions. Contact our Qatar engineering team with your project's material specification number for specific compliance confirmation.
Yes. We supply ASME B16.36 orifice flanges in all pressure classes and materials as matched pairs — including jack screws, ½″ NPT tapping plugs, and orifice plate holders. We can also supply the companion orifice plate (to AGA-3 / ISO 5167), differential pressure (DP) transmitters, impulse tubing, and manifold valve sets as a complete Qatar flow measurement package. Contact us with your pipe size, pressure class, and material specification for a complete package quotation including MTC 3.1 documentation.
For duplex (F51) and super duplex (F53) flanges in standard Qatar service, use ASTM A193 B8M Class 2 / A194 8M (SS 316 stud bolts and nuts) — this ensures galvanic compatibility and avoids accelerated corrosion at the bolt/flange interface. For Qatar sour gas service (H₂S environments per NACE MR0175), use ASTM A193 B7M / A194 2HM (NACE-compliant CS bolts with HRC ≤22 hardness control) or ASTM A193 B8M Class 2 stainless steel bolts — both comply with NACE MR0175 requirements for Qatar sour service applications on North Field and offshore Qatar projects. Our Qatar engineering team can confirm the correct bolting specification for your piping class.
API 5L, ASTM A106, A312 — seamless & ERW. Qatar gas & oil pipeline stock. MTC 3.1.
View Pipes
ASME B16.9 BW, B16.11 forged, socket weld & MSS SP-97 olets. Doha stock. MTC 3.1.
View Fittings
Gate, ball, globe, check, butterfly. API 6D / API 600. Class 150–2500. Same-week Doha delivery.
View Valves
I-beams, hollow sections, angles & plates. S275/S355, A36. Qatar stock & cut-to-length.
View Structural Steel