Orifice Flange Manufacturer, Supplier & Exporter
An orifice flange is a weld neck, slip on or threaded flange made to ASME B16.36, with radial pressure tappings drilled through the flange ring for flow measurement. Raaj Fittings manufactures and exports orifice flanges in stainless steel, duplex, nickel alloys, carbon steel and alloy steel, in Class 300 to Class 2500.
Orifice flanges are used in pairs, with an orifice plate clamped between them. As fluid passes through the plate's bore, a pressure difference develops across it; the tappings let a differential pressure transmitter measure this, and the flow rate is calculated from the reading. Jack screws in the flanges push them apart so the plate can be inspected or changed without disturbing the pipe.
All orifice flanges are supplied with EN 10204 3.1 mill test certificates, with 3.2 certification and third-party inspection on request.
We export orifice flanges to EPC contractors, refineries and stockists across the Middle East and GCC, Europe and the Americas, made to the ASME, EN or DIN standard your project specifies, with PED-compliant supply for European projects on request.
Orifice Flange Specifications
1" NPS to 24" NPS
ASME Class 300, 600, 900, 1500 and 2500
ASME B16.36 (dimensions), with flange drilling to ASME B16.5
Weld neck, slip on and threaded orifice flanges
Two tappings per flange, ½" NPT standard; other sizes or socket weld tappings on request
Matched pairs (orifice flange union) with jack screws; bolting and gaskets on request
EN 10204 3.1 mill test certificate as standard; EN 10204 3.2 on request
Materials & Grades
We supply orifice flanges in the following materials and grades. All grades are supplied with EN 10204 3.1 / 3.2 Mill Test Certificates.
Stainless Steel Orifice Flanges
Stainless steel flanges offer excellent corrosion resistance and are essential in chemical, pharmaceutical, food processing, and marine environments.
(ASTM A182 F304 / F304L) General corrosion resistance
(ASTM A182 F316 / F316L) Superior resistance to chlorides, acids; marine & pharmaceutical service
(ASTM A182 F316H) High-temperature elevated creep strength
(ASTM A182 F321) Titanium-stabilized; suitable for sustained elevated temperatures
(ASTM A182 F347) Columbium-stabilized; used in heat exchangers and high-temperature piping
High alloy; exceptional resistance to strong acids
Duplex & Super Duplex Stainless Steel Orifice Flanges
Duplex and super duplex grades offer approximately twice the yield strength of standard austenitic stainless steel, combined with excellent resistance to stress corrosion cracking and pitting — making them ideal for offshore, subsea, and chemical processing.
(UNS S31803 / S32205) Used in offshore platforms and chemical processing plants
(UNS S32750) Ideal for seawater handling and desalination systems
(UNS S32760) Designed for high-chloride offshore service applications
Nickel Alloy Orifice Flanges
For the most aggressive corrosive environments — including concentrated acids, caustic solutions, sour gas service, and extreme temperatures — we offer flanges in a full range of nickel alloys.
(UNS N06600) High-temperature oxidation resistance
(UNS N06625) Outstanding corrosion resistance for offshore and subsea service
(UNS N08825) Excellent resistance to phosphoric and sulfuric acids
(UNS N10276) Broad-spectrum corrosion resistance in acids and chlorides
(UNS N06022) Superior resistance to oxidizing acids
(UNS N04400) Suitable for seawater, hydrofluoric acid, and marine environments
(UNS N08020) Engineered for sulfuric acid service
Exceptional corrosion resistance with low weight
(C70600 / C71500) Preferred for marine and seawater piping systems
Carbon Steel Orifice Flanges
Carbon steel is the standard choice for general-purpose, non-corrosive, and elevated-temperature services. The primary grade for forged carbon steel flanges is ASTM A105, and for low-temperature service, ASTM A350 LF2.
Primary grade for forged carbon steel fittings and flanges — covers ambient and elevated-temperature service in pressurised piping systems.
Low-temperature carbon steel, impact-tested for service down to -46°C (-50°F) — LNG, cold climate, and cryogenic piping applications.
Alloy Steel Orifice Flanges
Alloy steel flanges are specified for high-temperature, high-pressure service in power generation, petrochemical, and refinery applications.
(5% Cr, ½% Mo) Designed for elevated temperature refinery service
(9% Cr, 1% Mo) Suitable for high-temperature steam and hydrogen service
(1¼% Cr, ½% Mo) Widely used in thermal power plant piping systems
(2¼% Cr, 1% Mo) Used in high-temperature pressure vessels and reactors
(9% Cr, 1% Mo, V, Nb) Engineered for ultra-high-temperature power plant steam lines
How an Orifice Flange Assembly Works
A pair of orifice flanges, an orifice plate, two gaskets, the stud bolts and the jack screws together make up an orifice flange union. The plate is held between the two flange faces with its bore centred in the pipe. Pressure tappings drilled radially through each flange ring sit just upstream and downstream of the plate; these "flange tappings" are positioned so the measured differential pressure can be converted to flow using recognised flow-measurement standards.
- Pressure tappings — drilled through the flange ring to the bore, normally threaded ½" NPT for the impulse lines.
- Jack screws — spread the flanges apart to remove or replace the orifice plate.
- Thicker ring — orifice flanges are thicker than standard flanges to leave room for the tappings.
- Bore matched to pipe — the weld neck type is bored to the pipe schedule for a smooth flow profile, which matters for measurement accuracy.
Choosing the Flange Type
Weld neck orifice flanges are the most common, because the matched bore and butt weld give the undisturbed flow needed for accurate metering, and they suit high pressures. Slip on and threaded orifice flanges are used on smaller and lower-pressure lines. For details of the standard weld neck design, see our weld neck flanges.
Ordering Information
Please give the size, pressure class, facing, flange type, pipe schedule, material grade, number and size of tappings, and whether bolting, jack screws and gaskets are to be supplied with the pair.
Applications & Industries
- Flow metering of oil, gas and steam in refineries and process plants
- Custody transfer and allocation metering skids
- Fuel gas and steam flow measurement in power plants
- Chemical and petrochemical process control loops
- Water and cooling-water flow measurement
- Offshore metering systems in duplex and super duplex
See all flange types, and our tube fittings for the instrument impulse lines.
Testing, Inspection, Marking & Packing
Orifice flanges are produced under our quality assurance process:
- Incoming material verification with PMI testing
- Chemical and mechanical testing to the applicable ASTM material specification
- Dimensional inspection of tapping position, tapping size, bore, thickness and facing
- Thread gauging of NPT tappings and jack-screw holes
- Marking with grade, size, class and heat number, with the pair identified together
Supplied with EN 10204 3.1 mill test certificates; EN 10204 3.2 certificates and third-party inspection are available on request.
Flanges are packed for export with gasket faces protected by covers, rust-preventive coating on carbon and alloy steel, and seaworthy wooden cases; marking, tagging and packing to your specification are available on request.
Why Choose Raaj Fittings for Orifice Flanges?
Raaj Sagar Steels has supplied piping components since 2003 and today manufactures flanges at two plants in India for buyers in the Middle East, Europe and the Americas.
- Manufactured in-house — Orifice flanges are made in our own plants, so material, dimensions and delivery stay under our control.
- Ready stock, short lead times — common sizes and grades are held in stock for prompt dispatch; other sizes, grades and specials are manufactured to order.
- Certified quality — ISO 9001:2015, ISO 14001:2015 and ISO 45001:2018 certified; PED 2014/68/EU and IBR supply available, and NACE MR0175 / ISO 15156 material on request.
- 100% material verification — PMI testing on incoming material and EN 10204 3.1 mill test certificates with every order; 3.2 certificates on request.
- Third-party inspection ready — we regularly work with SGS, Bureau Veritas, TÜV and DNV.
- Export documentation — MTCs, certificates of origin, packing lists and inspection reports to suit projects in the GCC, Europe and the Americas.
- Export packing — seaworthy packing with end and face protection, and packing to your specification on request.
- Fast response — our team replies to enquiries within one business day.
Orifice Flanges — FAQs
An orifice flange is a flange made to ASME B16.36 with pressure tappings drilled through its ring. Used in pairs with an orifice plate between them, it allows the pressure drop across the plate to be measured to calculate flow.
ASME B16.36 covers orifice flanges in Class 300 to 2500, including the thickness, tapping location and jack-screw arrangement. Flange drilling follows ASME B16.5.
The orifice plate is clamped between two flanges, each with its own pressure tappings — one upstream and one downstream of the plate. The two flanges are made and marked as a matched pair.
Jack screws are threaded through one flange and push against the other, spreading the joint so the orifice plate can be removed or replaced without moving the pipework.
ASME B16.36 starts at Class 300. For Class 150 systems, Class 300 orifice flanges are normally used, as their extra thickness is needed for the tappings.
Yes. We supply orifice flanges for projects under the European Pressure Equipment Directive (PED 2014/68/EU), and with IBR certification for Indian boiler applications. NACE MR0175 / ISO 15156 compliant material is also available on request for sour service in the Middle East and the Americas.
