Orifice Flanges – Types, Uses, Tappings, Classes & Flow Measurement Guide

Orifice Flanges are specially designed flange assemblies used with an orifice plate for measuring the flow of liquids, gases and steam in process piping systems.

Unlike standard piping flanges, an Orifice Flange may include provisions for pressure measurement connections located near the orifice plate. These connections allow differential pressure to be measured and used for flow calculation.

Vandan Alloys manufactures and supplies Orifice Flanges in carbon steel, stainless steel, alloy steel, duplex, super duplex and nickel alloy materials according to customer drawings, applicable standards and project specifications.

What is an Orifice Flange?

An Orifice Flange is a specially configured flange used to install an orifice plate in a piping system.

The orifice plate creates a controlled restriction in the pipe. As fluid passes through the restriction, a pressure difference develops across the plate.

Pressure connections associated with the flange assembly can be connected to suitable instrumentation for differential-pressure measurement.

The measured differential pressure can then be used by the applicable flow-measurement system to determine flow rate.

What is an Orifice Plate?

An Orifice Plate is a thin plate with a precisely machined opening installed between flanges.

The opening restricts the fluid flow and produces a measurable pressure differential.

The orifice plate, flange configuration, pressure tappings and instrumentation must be designed as a compatible measurement system.

The exact orifice dimensions should be established according to the applicable flow-measurement standard and project engineering requirements.

Orifice Flange Assembly

A typical orifice flange arrangement may include:

Orifice Flange + Orifice Plate + Gasket + Bolting + Pressure Tappings + Differential Pressure Instrumentation

The flange provides the mechanical connection and supports the installation arrangement for the orifice plate.

The pressure tappings provide access to pressure measurement points as specified by the design.

Orifice Flange Pressure Tappings

One of the main features that differentiates Orifice Flanges from conventional flanges is the provision for pressure measurement connections.

Common tapping arrangements can include:

• Corner taps

• Flange taps

• Other tapping configurations according to the applicable measurement standard

The exact tapping location and dimensions should be confirmed against the applicable standard and project specification.

Flange Taps

Flange taps are pressure connections positioned at specified distances from the orifice plate.

They are commonly associated with orifice flow-measurement arrangements.

The exact dimensions and location of the pressure taps should not be assumed and must follow the applicable standard or approved engineering drawing.

Orifice Flange Facing

Orifice Flanges may be supplied with different facing configurations depending on the required design.

Raised Face – RF

RF Orifice Flanges are commonly used for industrial process piping and differential-pressure measurement assemblies.

Ring Type Joint – RTJ

RTJ Orifice Flanges can be supplied where a ring-type joint connection is required and permitted by the applicable standard.

The RTJ groove and ring dimensions must correspond to the mating components.

Flat Face – FF

Flat-face configurations may be considered where specifically required by the project design and applicable standard.

Orifice Flange Pressure Classes

Common ASME pressure classes include:

• Class 150

• Class 300

• Class 400

• Class 600

• Class 900

• Class 1500

• Class 2500

The applicable class depends on the flange size, material, temperature, pressure and governing standard.

For EN requirements, customers may specify PN-rated configurations such as:

• PN10

• PN16

• PN25

• PN40

• PN63

• PN100

• PN160

Availability depends on the applicable standard and configuration.

Orifice Flange Size Range

Orifice Flanges can be supplied for various nominal pipe sizes according to the applicable flange standard.

Requirements may include:

• Small diameter process lines

• Medium diameter piping

• Large process piping

• Metering systems

• Custom dimensions

The flange size and orifice plate dimensions must be considered together to ensure compatibility.

Orifice Flange Materials

Vandan Alloys supplies Orifice Flanges in a wide range of materials.

Carbon Steel

• ASTM A105

• ASTM A105N

Stainless Steel

• ASTM A182 F304

• ASTM A182 F304L

• ASTM A182 F316

• ASTM A182 F316L

• F321

• F347

• F310

• F904L

Duplex Stainless Steel

• Duplex 2205

• UNS S31803

• UNS S32205

Super Duplex Stainless Steel

• Super Duplex 2507

• UNS S32750

• UNS S32760

Nickel & Special Alloys

Depending on the service requirements:

• Monel

• Inconel

• Incoloy

• Hastelloy

• Titanium

• Other special alloys

Material selection should consider the process medium, temperature, pressure and corrosion environment.

A105N Orifice Flanges

ASTM A105N Orifice Flanges are normalized carbon steel flanges supplied according to the applicable A105N material requirements.

Where a normalized condition is specified, the purchase specification should clearly state ASTM A105N.

A typical enquiry can specify:

ASTM A105N + Orifice Flange + NPS + Class + Facing + Tapping Requirement + Quantity

If an orifice plate is also required, its material, bore, thickness and applicable flow-measurement standard should be specified separately.

Stainless Steel Orifice Flanges

Stainless Steel Orifice Flanges are commonly selected for process applications where corrosion resistance and material compatibility are important.

Typical grades include:

• 304

• 304L

• 316

• 316L

• 321

• 347

• 310 / 310S

• 904L

The selected material should be compatible with the process fluid and operating conditions.

Duplex & Super Duplex Orifice Flanges

Duplex and Super Duplex Orifice Flanges may be considered for demanding process environments requiring specific corrosion resistance and mechanical performance.

Common grades include:

Duplex 2205 – UNS S31803 / S32205

Super Duplex 2507 – UNS S32750 / S32760

The exact grade should be specified according to the project requirement.

Orifice Flange Standards

Orifice Flanges can be manufactured or supplied according to applicable flange and flow-measurement standards, including:

• ASME B16.5

• ASME B16.47, where applicable

• EN 1092-1

• DIN

• JIS

• BS

• Customer drawings

• Project-specific specifications

For the measurement arrangement, the applicable flow-measurement standard should also be clearly identified.

Orifice Flange Applications

Orifice Flanges are commonly used in:

• Oil & Gas

• Refineries

• Petrochemical Plants

• Chemical Processing

• Power Generation

• Steam Systems

• Natural Gas Systems

• Water Treatment

• Process Plants

• Industrial Flow Measurement

• Metering Systems

They are particularly relevant where differential-pressure-based flow measurement is required.

How Orifice Flow Measurement Works

The basic principle is straightforward:

1. Fluid enters the pipe.

2. The orifice plate restricts the flow.

3. A pressure difference develops across the plate.

4. Pressure is measured through the specified tapping arrangement.

5. The differential pressure is used by the flow-measurement system to calculate flow.

The actual calculation depends on the fluid properties, orifice geometry, pressure and temperature conditions, installation arrangement and applicable measurement standard.

Why Orifice Flanges are Different from Standard Flanges

A standard flange primarily provides a mechanical connection between piping components.

An Orifice Flange may additionally incorporate provisions for pressure measurement around an orifice plate.

Therefore, Orifice Flanges require attention not only to flange dimensions but also to:

• Tapping arrangement

• Tapping location

• Orifice plate compatibility

• Gasket arrangement

• Bore configuration

• Instrument connection

• Measurement requirements

Orifice Flange Selection

When selecting an Orifice Flange, consider:

• Nominal pipe size

• Pressure class

• Material

• Facing

• Orifice plate design

• Tapping arrangement

• Process fluid

• Operating pressure

• Operating temperature

• Pipe schedule

• Instrument connection

• Applicable standards

Complete project information helps ensure the flange and measurement assembly are compatible.

Orifice Flange vs Weld Neck Flange

Orifice Flange:
Specially configured for installation of an orifice plate and pressure measurement connections.

Weld Neck Flange:
Primarily designed as a welded pipe-to-flange connection and does not inherently provide an orifice measurement arrangement.

An Orifice Flange can therefore be considered a specialized flange configuration rather than simply another standard flange type.

Orifice Flange vs Slip-On Flange

Orifice Flange incorporates features required for an orifice measurement arrangement.

Slip-On Flange is a general flange design installed over the pipe and welded.

The selection depends on the function required by the piping system.

Orifice Plate Compatibility

The Orifice Flange and orifice plate should be treated as a coordinated assembly.

Important factors include:

• Plate outside diameter

• Bore diameter

• Plate thickness

• Plate material

• Gasket location

• Tapping arrangement

• Flange bore

• Pipe size

• Measurement standard

A flange should not be selected independently from the orifice plate design when the assembly is intended for accurate flow measurement.

Gasket Selection for Orifice Flanges

Gasket selection should consider:

• Flange facing

• Orifice plate arrangement

• Process fluid

• Pressure

• Temperature

• Chemical compatibility

• Applicable standard

Incorrect gasket positioning can interfere with the intended measurement arrangement, so installation should follow the approved design.

Orifice Flange Inspection

Inspection may include:

• Visual inspection

• Dimensional inspection

• Flange thickness

• Outside diameter

• Bore inspection

• PCD inspection

• Bolt-hole inspection

• Facing inspection

• Tapping location

• Tapping thread inspection

• Material identification

• Chemical analysis

• Mechanical testing

• Heat treatment verification where applicable

• Marking and traceability

• Third-party inspection

For measurement-critical applications, dimensional control is especially important.

MTC & Documentation

For applicable orders, EN 10204 Type 3.1 Material Test Certificate can be supplied.

Documentation may include:

• Material grade

• Heat number

• Chemical composition

• Mechanical properties

• Heat treatment information where applicable

• Dimensional inspection

• Tapping details

• Traceability records

Additional inspection documentation can be arranged according to the project specification.

Custom Orifice Flanges

Vandan Alloys can evaluate custom Orifice Flanges based on customer drawings and engineering specifications.

Custom requirements may include:

• Special tapping locations

• Special tapping connections

• Special bore

• Customized PCD

• Special flange thickness

• Special facing

• Special materials

• Special pressure classes

• Custom orifice plate arrangements

Customers can provide PDF drawings, CAD drawings, dimensional sketches or complete metering specifications for review.

How to Order Orifice Flanges

For quotation, provide:

Pipe Size / NPS:
Pressure Class / PN:
Material Grade:
Flange Type: Orifice Flange
Facing: RF / FF / RTJ
Tapping Type:
Tapping Size:
Orifice Plate Requirement: Yes / No
Pipe Schedule:
Standard:
Quantity:
Inspection Requirement:
Delivery Location:

If an orifice plate is required, provide its material, bore, thickness and applicable standard.

Vandan Alloys – Orifice Flange Manufacturer & Exporter

Vandan Alloys manufactures and supplies Orifice Flanges for process piping, flow-measurement systems, oil & gas, petrochemical, chemical, power and industrial applications.

Our supply range includes:

• Carbon Steel Orifice Flanges

• A105 Orifice Flanges

• A105N Orifice Flanges

• Stainless Steel Orifice Flanges

• Duplex Orifice Flanges

• Super Duplex Orifice Flanges

• Alloy Steel Orifice Flanges

• Nickel Alloy Orifice Flanges

• Custom Orifice Flanges

• Orifice Flange Assemblies according to project requirements

We support requirements involving different sizes, pressure classes, materials, facings, tapping arrangements and custom dimensions, subject to the applicable specification.

If you are looking for an Orifice Flange Manufacturer in India, A105N Orifice Flange Supplier, Stainless Steel Orifice Flange Manufacturer, ASME Orifice Flange Supplier or Custom Orifice Flange Exporter, send your complete requirement to Vandan Alloys.

Send your Orifice Flange drawing, tapping details or project specification for quotation.

Vandan Alloys 

Manufacturer of All Types of Flanges

3/5, Sakar Bhavan, Ground Floor, 6th  Khetwadi lane, SVP Road ,Mumbai – 400 004. India

TEL+91 022 6610 9925Mobile no: 09892882255  GSTIN:  27AUMPS2067F1ZB

Email: info@vandanalloys.com ; Web: www.vandanalloys.com

Please visit Our Flanges Division:www.vandanalloys.net

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Orifice Flange Manufacturer in India | A105N & Stainless Steel

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Vandan Alloys manufactures and exports Orifice Flanges with pressure tappings in A105, A105N, stainless steel, duplex and nickel alloys. Custom sizes and classes.

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