Flange Pressure Classes & Standards
Selecting the correct flange is not only about pipe size. Pressure class, dimensional standard, flange facing, material and operating conditions all play an important role in selecting the right flange for an industrial piping system.
Vandan Alloys supplies industrial flanges according to various international standards and pressure ratings for piping, process equipment and engineering applications.
Understanding Flange Pressure Classes
A flange pressure class indicates the pressure-temperature rating defined by the applicable standard. The actual allowable pressure depends on factors such as material grade, operating temperature, flange size and the applicable standard.
Common ASME flange pressure classes include:
Class 150 – Widely used for general industrial and utility piping.
Class 300 – Selected for applications requiring a higher pressure rating than Class 150.
Class 600 – Commonly used for higher-pressure process, oil & gas and industrial piping.
Class 900 – Used for demanding pressure-service applications.
Class 1500 – Selected for high-pressure piping and process systems.
Class 2500 – Used for specialized high-pressure applications where the applicable standard permits.
The pressure class should always be confirmed against the applicable pressure-temperature rating table rather than treating the class number as a direct pressure value.
ASME B16.5 Flanges
ASME B16.5 is one of the most widely referenced standards for pipe flanges and flanged fittings.
It covers dimensional requirements for applicable flange sizes, pressure classes, facing types, bolt-hole arrangements and other important flange details.
Vandan Alloys supplies flanges for requirements based on ASME B16.5 in different materials, sizes, classes and configurations.
ASME B16.47 Flanges
ASME B16.47 covers larger-diameter steel flanges and is commonly referenced for large-bore piping applications.
Large-diameter flange requirements should be checked carefully for the applicable series, nominal size, pressure class and dimensional configuration.
EN 1092-1 Flanges
EN 1092-1 is a European standard covering circular steel flanges and their dimensional requirements.
EN 1092-1 flanges are commonly specified using DN sizes and PN pressure designations.
Different flange types and facing arrangements are available according to the relevant flange type and standard requirements.
DIN Flanges
DIN flange standards are used in various industrial and engineering applications, particularly in systems based on European dimensional practices.
DIN requirements should be identified by the specific standard, nominal size, pressure designation and flange type before supply.
JIS Flanges
JIS flange standards are commonly used in piping systems and projects following Japanese Industrial Standards.
JIS flanges should be selected according to the required nominal size, pressure rating, material and applicable JIS standard.
BS Flanges
BS flange standards may be specified for particular piping, engineering and replacement requirements.
When a BS flange is requested, the exact standard and dimensional requirement should be confirmed before manufacturing or supply.
PN Ratings for Flanges
European flange specifications commonly use PN designations, such as:
PN6, PN10, PN16, PN25, PN40, PN63, PN100 and PN160, depending on the applicable standard and flange size.
PN designation should not be treated as a universal direct conversion to ASME Class. The applicable standard and pressure-temperature rating must be checked for the specific flange.
Flange Facing Standards
Flange facing affects the sealing arrangement between mating flanges.
Common configurations include:
Raised Face (RF) – Frequently used in industrial and process piping.
Flat Face (FF) – Used where a flat mating surface is specified.
Ring Type Joint (RTJ) – Designed for high-integrity sealing applications involving suitable RTJ flange and gasket arrangements.
The facing of the flange should match the mating component and gasket system.
Flange Size & Dimensional Requirements
Flange dimensions are determined by the applicable standard and nominal size.
Important dimensional requirements can include:
Nominal Pipe Size (NPS), Nominal Diameter (DN), Outside Diameter, Bore, Flange Thickness, Bolt Circle Diameter, Number of Bolt Holes, Bolt Hole Diameter and Facing Dimensions.
For special or non-standard requirements, an approved drawing or dimensional specification can be used for production.
NPS and DN Flange Sizes
ASME-based piping systems commonly use NPS (Nominal Pipe Size), while European standards commonly use DN (Nominal Diameter).
NPS and DN should not be assumed to be interchangeable based only on the numerical value. The applicable dimensional standard should always be confirmed.
How to Select the Correct Flange Standard
Before ordering a flange, the following information should be confirmed:
Flange Type – Weld Neck, Blind, Slip-On, Socket Weld, Threaded, Lap Joint, Orifice or another required configuration.
Size – NPS or DN according to the project specification.
Pressure Class / PN Rating – Based on the applicable piping standard.
Material Grade – Selected according to the service environment and mechanical requirements.
Facing – RF, FF, RTJ or another specified configuration.
Standard – ASME, EN, DIN, JIS, BS or another project-specific standard.
Quantity – Required number of pieces.
Inspection & Documentation – MTC, dimensional inspection or third-party inspection when specified.
Flange Materials for Different Standards
Flanges can be supplied in various materials depending on the application and applicable specification.
Common materials include:
Stainless Steel: 304, 304L, 316, 316L, 321, 347, 310, 310S and 904L.
Duplex & Super Duplex: Duplex 2205 and Super Duplex 2507.
Carbon Steel: ASTM A105 and other specified carbon steel grades.
Nickel Alloys: Inconel, Incoloy, Monel, Hastelloy and other special alloys.
The material specification should always be matched with the required standard and service conditions.
Flange Standards for Industrial Applications
Different flange standards are selected according to the design practice and location of the project.
They are used in industries such as:
Oil & Gas, Refineries, Petrochemical Plants, Chemical Processing, Power Generation, Water Treatment, Marine, Pharmaceutical, Food Processing and General Engineering.
The correct combination of standard, class or PN rating, material, size and facing is important for reliable flange installation.
Flange Inspection & Documentation
For industrial and export orders, inspection and documentation can be arranged according to the purchase requirement.
Available documentation may include:
EN 10204 Type 3.1 Material Test Certificate
Heat number traceability
Chemical composition
Mechanical test results
Dimensional inspection
Visual inspection
Third-party inspection, when required
Documentation requirements should be confirmed at the quotation or order stage.
Flange Supplier & Exporter from India
Vandan Alloys supplies flanges for domestic and international industrial requirements based on customer specifications.
We support standard flange requirements as well as project-specific, drawing-based and special material requirements.
For quotation, provide the flange type, size, material grade, pressure class or PN rating, facing, standard, quantity and delivery destination.
Request a Flange Quotation
Share your flange specification, drawing or purchase requirement with Vandan Alloys for review and quotation.
Vandan Alloys
Seamless Steel Pipe | ERW Steel Pipe | Fasteners | Plate | Fittings | Flanges
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Email: info@vandanalloys.com ; Web: www.vandanalloys.com
Please visit Our Flanges Division:www.vandanalloys.net
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Flange Pressure Classes & Standards | ASME B16.5 & EN 1092-1 | Vandan Alloys
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Learn about flange pressure classes and standards including ASME B16.5, ASME B16.47, EN 1092-1, DIN and JIS, with Class 150 to 2500 and PN ratings.
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