Flange Standards: ASME B16.5 vs DIN EN 1092 vs JIS B2220 — Complete Comparison Guide

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Quick Answer

ASME B16.5 (American), EN 1092-1 (European, replacing older DIN 2501), and JIS B2220 (Japanese) are the three main flange standards used globally — and they are not interchangeable. ASME uses a Class system (150, 300, 600, 900, 1500, 2500) where the class number does NOT equal pressure in psi; actual pressure rating depends on material and temperature per ASME B16.5 pressure-temperature tables. EN 1092-1 uses a PN (Pressure Nominal) system (PN2.5 through PN420) where PN approximately equals nominal pressure in bar at reference temperatures. While certain pairings serve similar pressure ranges (Class 150 ≈ PN20, Class 300 ≈ PN50, Class 600 ≈ PN110), the flanges are physically incompatible — bolt circle diameters, bolt hole counts, flange thicknesses, and facing dimensions all differ. Mixing standards in the same piping system requires custom transition flanges or complete redesign. For international projects spanning American and European specifications, always specify Standard + Size + Rating + Facing + Material + Bore on every purchase order and drawing.

A petrochemical project in Saudi Arabia received its first shipment of imported flanges from a European supplier. The drawings specified "PN40 flanges, DN150." The site team began bolting flanges to ASME B16.5 Class 300 piping installed by an American EPC contractor. Within an hour, the problem became clear: the bolt holes didn't align. The bolt circles were different diameters. The flange thicknesses didn't match. The gaskets couldn't seat properly. Construction stopped. The project sourced replacement ASME B16.5 Class 300 flanges by emergency air freight at 8× the original cost, and lost three weeks of construction schedule.

This is the flange standards problem that catches projects worldwide. Two flanges marked with similar pressure ratings — one "PN20" and one "Class 150" — appear equivalent. They are not. They are designed under different engineering philosophies, use different dimensional systems, and produce physically incompatible hardware that cannot be bolted together.

For procurement managers, project engineers, EPC contractors, and anyone specifying flanges for international projects — this guide covers the three major flange standards comprehensively. The differences between ASME B16.5 Class ratings and EN 1092-1 PN ratings, the dimensional and facing variations that make the standards incompatible, the materials and pressure-temperature considerations that determine actual performance, JIS standards used in Japanese and Asian markets, and the procurement specifications required to avoid costly mistakes.

For background on flange types, faces, and pressure classes within the ASME system, see Pipe Flanges: Types, Faces & Pressure Classes. For the specific weld neck vs slip-on decision, see Weld Neck vs Slip-On Flange.

The Three Major Flange Standards

ASME B16.5 and B16.47 (American)

The American Society of Mechanical Engineers (ASME) publishes the dominant global flange standards.

ASME B16.5: Pipe Flanges and Flanged Fittings — covers sizes NPS ½" through NPS 24" (DN 15-600) in pressure Classes 150, 300, 400, 600, 900, 1500, and 2500.

ASME B16.47: Large Diameter Steel Flanges — covers NPS 26 through NPS 60 (DN 650-1500), with two series:

• Series A (formerly MSS SP-44) — used in oil and gas, longer history

• Series B (formerly API 605) — slightly different dimensions

Adoption: Standard across North America, Middle East, much of Africa, Latin America. Increasingly the global default for oil & gas, petrochemical, and refinery projects.

EN 1092 (European) — Replaces DIN 2501

The European Standard EN 1092 replaced the older DIN 2501 (which itself derived from earlier German standards). The standard family covers:

• EN 1092-1: Steel flanges (most common)

• EN 1092-2: Cast iron flanges

• EN 1092-3: Copper alloy flanges

• EN 1092-4: Aluminum alloy flanges

EN 1092-1 incorporates many former DIN specifications, with PN ratings: PN2.5, PN6, PN10, PN16, PN25, PN40, PN63, PN100, PN160, PN250, PN320, PN400, PN420.

Note on DIN vs EN: "DIN" is still widely used as terminology, but the actual current standards are EN. A "DIN flange" today is almost always an EN 1092-1 flange. The older DIN 2501 standard is technically superseded but the term persists in industry usage.

Adoption: Standard across Europe (including UK, despite Brexit). Common in Russia, CIS countries, parts of Africa, and projects where European EPC contractors lead engineering.

JIS B2220 (Japanese)

The Japanese Industrial Standard for steel pipe flanges.

JIS B2220: Steel pipe flanges with K-class pressure ratings: 5K, 10K, 16K, 20K, 30K, 40K, 63K.

The "K" approximately represents pressure in kgf/cm². Adopted across Japan and influential in some Asian markets, though many Japanese projects now use ASME for international compatibility.

Other Regional Standards

• GOST 12815 (Russia/CIS) — based on metric system

• BS 4504 (UK older standard, now superseded by EN 1092)

• AS 4087 (Australia) — based on PN system

• NF E29 (France older, now EN)

• UNI (Italy older, now EN)

ASME Class vs EN PN: The Critical Misconception

The single most common error in international procurement is treating Class ratings and PN ratings as equivalent. They are not.

What "Class 150" Means

ASME Class is a designation, not a pressure value. A Class 150 flange's actual pressure rating depends on:

• Material grade (carbon steel A105, stainless 316L, alloy steel, etc.)

• Operating temperature (ratings decline as temperature increases)

For A105 carbon steel Class 150 flange:

• At 100°F (38°C): 285 psi (19.6 bar)

• At 400°F (204°C): 200 psi (13.8 bar)

• At 600°F (316°C): 140 psi (9.6 bar)

• At 750°F (399°C): 75 psi (5.2 bar)

For 316L stainless Class 150 flange:

• At 100°F (38°C): 275 psi (19 bar)

• At 600°F (316°C): 180 psi (12.4 bar)

• At 1000°F (538°C): 120 psi (8.3 bar)

The Class number is a rating tier, not a fixed pressure.

What "PN16" Means

EN PN rating is more direct: PN approximately equals nominal pressure in bar at reference temperatures (usually 20°C or 38°C).

For EN P250GH carbon steel PN16 flange:

• At 20°C: 16 bar (232 psi)

• At 200°C: 13.5 bar (196 psi)

• At 300°C: 11.7 bar (170 psi)

For 1.4404 (316L equivalent) stainless PN16 flange:

• At 20°C: 16 bar (232 psi)

• At 300°C: 12.5 bar (181 psi)

PN values represent more nominal pressure at reference conditions, but actual ratings still vary with material and temperature.

Why They're "Approximately Equivalent" But Not Interchangeable

For some material/temperature combinations, the pressure values look similar:

ISO 7005-1 (international standard) addresses this by listing both Class and PN ratings, attempting to map them.

But the flanges are NOT interchangeable because the dimensions differ. Even if pressure ratings approximately match, you cannot bolt a Class 150 flange to a PN16 flange.

Dimensional Differences: Why Standards Are Incompatible

Specific dimensional differences make ASME and EN flanges physically incompatible:

Bolt Circle Diameter (BCD)

The diameter of the circle on which bolt holes are arranged.

Example: 4-inch / DN100 flange comparison

The bolt circle alone differs by 10.5mm. The bolts cannot align between standards. Even with the same number of bolts, the position differs.

Bolt Hole Count

For some sizes, the number of bolt holes also differs:

Example: 8-inch / DN200 flange

Eight versus twelve bolts is not a minor difference — these flanges cannot be bolted together by any means short of complete redrilling.

Thread Types

• ASME typically uses UNC (Unified National Coarse) threads in inch sizes

• EN/DIN uses ISO metric threads (M-series)

• JIS uses metric threads but with different pitch in some cases

Stud bolts ordered for one standard cannot replace bolts in another standard.

Facing Dimensions

The raised face (RF) or flat face (FF) dimensions differ between standards:

Raised Face Height

Even when both flanges have raised faces, the actual face geometry differs, affecting gasket selection and compression.

Flange Thickness

EN flanges are typically thinner than ASME equivalents at similar pressure ratings:

This affects bolt length, stud projection, and structural calculations.

Facing Types

Both standards offer multiple facing types, but with different terminology and dimensions.

ASME B16.5 Facing Types

• Raised Face (RF): Standard for most applications; 1.6mm raised on Class 150, 6.4mm on Class 300+

• Flat Face (FF): Full face contact, used with full-face gaskets, common with cast iron equipment

• Ring Type Joint (RTJ): Metal-to-metal seal using oval or octagonal ring gasket, high-pressure service

• Tongue and Groove (TG): Mating tongue and groove faces, prevents gasket blowout

• Male and Female (MF): Similar to tongue and groove, used for high-pressure or volatile services

• Lap Joint Stub End: Used with backing flange, for frequent disassembly or corrosion-resistant applications

EN 1092-1 Facing Types (Forms)

EN uses "form" designations for facing types:

• Form A: Flat face (FF)

• Form B: Raised face (RF) — most common

• Form C: Tongue (mating with Form D)

• Form D: Groove (mating with Form C)

• Form E: Male (mating with Form F)

• Form F: Female (mating with Form E)

• Form G: O-ring face — convex

• Form H: O-ring face — flat

Critical: Cannot Mix Facing Types

A raised face (Form B/RF) flange cannot bolt to a flat face (Form A/FF) flange — the raised portion damages the flat surface, prevents proper gasket compression, and creates leak paths.

For complete coverage of facing types and flange selection, see Pipe Flanges: Types, Faces & Pressure Classes.

Material Specifications

The material designations differ between standards.

ASME Material Standards

For carbon steel flanges per ASME B16.5:

• ASTM A105: Standard forged carbon steel for piping components

• ASTM A350 LF1/LF2: Low-temperature carbon steel

• ASTM A694 F52/F60/F65: High-yield carbon steel for line pipe applications

For alloy steel:

• ASTM A182 F11/F22/F91: Cr-Mo alloys for high temperature

• ASTM A350 LF3: 3.5% nickel for low temperature

For stainless steel:

• ASTM A182 F304/F304L/F316/F316L/F321/F347: Austenitic grades

• ASTM A182 F44 (UNS S31254): Super austenitic

• ASTM A182 F51/F53/F55: Duplex and super duplex

EN Material Standards

For carbon steel flanges per EN 1092-1:

• EN 1092-1 P250GH: Standard carbon steel (similar to A105)

• EN 1092-1 P265GH: Improved carbon steel

• EN 1092-1 P280GH: Higher temperature service

For alloy steel:

• EN 10222-2 materials: 13CrMo4-5, 10CrMo9-10, X10CrMoVNb9-1 (similar to A182 F11/F22/F91)

For stainless steel:

• EN 1.4301: Equivalent to 304

• EN 1.4307: Equivalent to 304L

• EN 1.4401: Equivalent to 316

• EN 1.4404: Equivalent to 316L

For the materials covered in our blog, see Carbon Steel Plate ASTM A516 & A36 and Stainless Steel Plate: Grades 304, 316, 321.

When to Use Which Standard

The standards choice depends on project ownership, location, and integration requirements.

Use ASME B16.5 When:

• Project is owned/specified by American operator or EPC

• Project is located in North America, Middle East, parts of Africa

• Oil & gas, petrochemical, refinery service

• Existing facility uses ASME piping (extension/integration)

• Project specifications mandate ASME

• Equipment from American manufacturers is being installed

• High pressures (Class 1500-2500) required

Use EN 1092 When:

• Project is owned/specified by European operator or EPC

• Project is located in Europe, parts of CIS, Africa with European links

• Water treatment, HVAC, district heating, general industry

• Existing facility uses EN/DIN piping (extension/integration)

• Project specifications mandate EN

• Equipment from European manufacturers is being installed

• Standard chemical process service in European-designed plants

Use JIS When:

• Project is located in Japan or Asian markets with JIS preference

• Japanese equipment is being installed

• Specific Japanese supplier requirement

Mixed Standards Projects

Some projects involve multiple standards (e.g., American EPC building in Europe, European-designed equipment imported to Middle East). Approaches:

Option 1: Standardize project-wide

• Choose one standard for all flanges in the project

• Use transition pieces or modified equipment where needed

• Most reliable but may require equipment customization

Option 2: Define boundaries

• ASME for one section, EN for another

• Clear demarcation points with transition flanges

• Common in plant expansions

Option 3: Custom transition flanges

• Manufacturer creates flanges with ASME drilling on one side, EN on the other

• Or flange + flange + spool combination

• Higher cost but allows interface without redesign

Common Specification Mistakes

After 15+ years supplying flanges to international projects across Africa, Middle East, Central Asia, and Europe:

Mistake 1: "Class 150 = PN16" Assumption

Buyer specifies "PN16 flange" expecting it to work with Class 150 piping. The flanges arrive but cannot be bolted to existing piping due to dimensional incompatibility.

Prevention: Always specify the full standard + size + rating + facing + material. Never assume Class and PN are interchangeable. Verify bolt circle, bolt count, and facing match the connecting flange.

Mistake 2: Mismatched Size Designations

Buyer orders "4-inch flange" from European supplier. Supplier sends DN100 (not the same as NPS 4 in some dimensional aspects). Installation issues arise.

Prevention: Always use the dimensional designation native to the standard. "NPS 4" for ASME, "DN 100" for EN. These are nominally equivalent but the standard system determines the exact dimensions.

Mistake 3: Wrong Facing Type

Buyer specifies "PN16 raised face flange" intending to mate with a flat face flange on cast iron equipment. Installation crushes the raised face during bolting; sealing fails; equipment damage.

Prevention: Verify facing types match on both sides of the connection. Raised face mates with raised face. Flat face mates with flat face. Tongue mates with groove. Mixing is incompatible.

Mistake 4: Ignoring Material Equivalence

Buyer orders "A105 carbon steel flange" from European supplier. Supplier provides "P250GH" thinking it's equivalent. The materials are similar but not identical — strength, weldability, and code acceptance differ.

Prevention: Confirm exact material specification required. For projects requiring ASME code compliance, specify ASTM materials explicitly. For EN code compliance, specify EN materials explicitly. Don't accept "equivalent" without verification.

Mistake 5: Pressure-Temperature Calculation Errors

Buyer specifies "Class 150 flange for 200°F service" without checking the pressure-temperature rating. The Class 150 flange in A105 material is rated 230 psi at 200°F, but operating pressure is 250 psi. Joint fails.

Prevention: Always reference the pressure-temperature rating table for the actual material and temperature. ASME B16.5 Table 2 contains these ratings. EN 1092-1 has equivalent tables.

Mistake 6: Forgotten Bolting Specifications

Buyer orders flanges per ASME B16.5 but uses metric bolting. The bolt holes are sized for inch UNC threads; metric studs don't seat properly; assembly fails.

Prevention: Specify bolting (stud bolts, nuts, washers) matching the flange standard. ASME flanges typically use ASTM A193 B7 studs with A194 2H nuts in UNC threads. EN flanges typically use ISO metric studs.

Mistake 7: Inadequate Gasket Selection

Buyer orders flanges but doesn't specify gaskets. Field selection assumes "standard" gasket — but the actual gasket type, material, and dimensions are critical for the specific service.

Prevention: Include gasket specifications in the original order: type (spiral wound, ring joint, soft cut, etc.), material (graphite, PTFE, metallic, etc.), and dimensions matching the flange face.

Mistake 8: Mixing Standards in One Project

Project receives drawings showing both Class designations and PN ratings inconsistently. Procurement orders some flanges in ASME, some in EN. Field assembly is chaotic.

Prevention: Establish project-wide flange standardization at the design stage. Specify clearly in project specifications. Have transition flanges only at defined interface points (e.g., where European equipment connects to American piping).

Procurement Specification Best Practices

Every flange purchase order should include:

Complete Specification Format

Wrong: "4-inch flange"

Correct (ASME): "Weld neck flange per ASME B16.5, NPS 4, Class 300, raised face, ASTM A105 carbon steel, schedule 40 bore (4.026" ID), standard finish"

Correct (EN): "Weld neck flange per EN 1092-1, DN 100, PN40, Form B (raised face), material P250GH, bore matching DIN 2448 pipe series 1"

Required Order Elements

1. Standard: ASME B16.5 / EN 1092-1 / JIS B2220 / etc.

2. Type: Weld neck, slip-on, blind, lap joint, socket weld, threaded

3. Size: NPS or DN

4. Rating: Class or PN

5. Facing: RF/FF/RTJ/etc. with dimensions where critical

6. Material: Specific grade (A105, F316L, P250GH, etc.)

7. Bore: For weld neck, the inside diameter must match the pipe

8. Bolting: Stud bolts and nuts specifications

9. Gasket: Type and material

10. Documentation: EN 10204 Type 3.1 mill test certificate, etc.

Documentation Requirements

For most flange procurement:

• Mill test certificate (EN 10204 Type 3.1)

• Material chemistry and mechanical properties

• Dimensional verification

• Surface finish certification

• Heat number traceability

• Marking per applicable standard

• Hydrostatic test (for higher classes, often Class 600+)

For critical service (sour gas, hydrogen, high-pressure):

• NACE MR0175 compliance certificate

• Hardness testing

• PMI (Positive Material Identification) on stainless and alloy

• Charpy impact test results

• Third-party inspection (Bureau Veritas, SGS, TÜV, Lloyd's)

Specification Template

PROJECT: [Project Name]
APPLICATION: [Pipe size, service]
LOCATION: [Country, Facility]

FLANGE SPECIFICATION:
- Standard: [ASME B16.5 / EN 1092-1 / JIS B2220 / Other]
- Type: [Weld neck / Slip-on / Blind / Threaded / Lap joint / Socket weld]
- Size: [NPS or DN]
- Rating: [Class or PN]
- Facing: [RF / FF / RTJ / TG / MFM / Form A-H for EN]
- Bore: [For weld neck — must match pipe schedule]

MATERIAL:
- Grade: [Specific designation - A105, F316L, P250GH, etc.]
- Heat treatment: [Per applicable standard]
- Special requirements: [NACE compliance, low temp, sour service]

DIMENSIONS:
- Reference: [ASME B16.5 Table 8 / EN 1092-1 Table reference]
- Verify: bolt circle, bolt count, bolt hole diameter, flange OD, flange thickness, raised face dimensions

OPERATING CONDITIONS:
- Service: [Fluid type]
- Operating pressure: [Per material and temperature P-T rating]
- Operating temperature: [°C and °F]
- Design pressure: [bar / psi]
- Design temperature: [°C / °F]
- Special service: [H₂S content for sour service, chloride content, etc.]

BOLTING:
- Stud bolts: [ASTM A193 B7 / B8M / EN equivalent]
- Nuts: [ASTM A194 2H / 8M / EN equivalent]
- Quantity per flange: [Per standard]
- Thread: [UNC for ASME / Metric for EN]
- Stud length: [Per flange thickness + nuts + washers]

GASKET:
- Type: [Spiral wound / Ring joint / Soft cut / Solid metal]
- Material: [Graphite / PTFE / Metallic / Composite]
- Dimensions: [Per flange facing geometry]

CONNECTING EQUIPMENT:
- Mating flange standard: [Verify same standard]
- Mating flange size and rating: [Must match]
- Mating equipment manufacturer: [For verification]

DOCUMENTATION REQUIRED:
- EN 10204 Type 3.1 mill test certificate
- Chemical and mechanical test results
- Dimensional verification reports
- Surface finish certifications
- Hydrostatic test certificates (for higher classes)
- NACE MR0175 compliance (if applicable)
- PMI testing reports (for stainless/alloy)
- Heat number traceability

DELIVERY:
- Required date: [Date]
- Shipping terms: [FOB / CIF / DDP]
- Marking: [Per standard requirements]
- Packaging: [Wood crate, individual wrapping for stainless, etc.]

Supply from Kasko Makine

Kasko Makine supplies flanges per all major international standards for refining, petrochemical, oil & gas, power generation, water treatment, and general industrial applications:

ASME B16.5 Flanges:

• All standard types: weld neck, slip-on, blind, threaded, socket weld, lap joint

• All standard sizes: NPS ½" through NPS 24"

• All standard classes: 150, 300, 400, 600, 900, 1500, 2500

• All facing types: RF, FF, RTJ, TG, MF

ASME B16.47 Large Diameter:

• NPS 26" through NPS 60"

• Series A (MSS SP-44 based) and Series B (API 605 based)

EN 1092-1 Flanges:

• All standard types and forms (Form A through H)

• DN 10 through DN 4000

• All PN ratings: PN2.5 through PN420

• Compatible with former DIN 2501 references

JIS B2220 Flanges:

• All K-class ratings: 5K through 63K

• Standard JIS sizing

Custom and Transition Flanges:

• ASME on one side, EN on the other (for interface points)

• Non-standard dimensions per project requirements

• Specialty alloy combinations

Materials available:

• Carbon steel: A105, A350 LF1/LF2/LF3, A694 F52-F65, P250GH, P265GH

• Alloy steel: A182 F11/F22/F91, 13CrMo4-5, 10CrMo9-10, X10CrMoVNb9-1

• Stainless steel: A182 F304/F304L/F316/F316L/F321/F347, EN 1.4301/1.4307/1.4401/1.4404

• Duplex: A182 F51/F53/F55

• Super duplex: A182 F55

• Specialty: Hastelloy, Inconel, Monel, titanium (custom orders)

Documentation per shipment:

• EN 10204 Type 3.1 mill test certificates

• Chemical composition certificates

• Mechanical test results (yield, tensile, elongation, hardness)

• Dimensional verification reports

• Surface finish certifications

• Hydrostatic test certificates (where required)

• NACE MR0175 compliance certificates (for sour service)

• PMI testing reports (for stainless and alloy)

• Heat number traceability with mill records

• Third-party inspection reports (Bureau Veritas, SGS, TÜV, Lloyd's available on request)

Engineering services:

• Standards selection consulting for international projects

• ASME-to-EN equivalency analysis

• Pressure-temperature verification for specified material and service

• Custom transition flange design

• Documentation review and certification coordination

Need help specifying flanges for international projects? Send us your service conditions, mating equipment specifications, applicable codes (ASME, EN, JIS, project-specific), and delivery location to info@kaskomakine.com or WhatsApp +90 (537) 521 1399. Our team will verify your specifications, identify any standards conflicts in your project, and provide complete pricing with documentation requirements within 48 hours.

Continue Reading: Flanges & Fittings Series

This standards comparison guide complements our flange and fittings content:

• Pipe Flanges: Types, Faces & Pressure Classes — Flange types within ASME standards

• Weld Neck vs Slip-On Flange — Critical type selection

• Pipe Fittings: Complete Guide — Fittings to complement flange specifications

• Weldolet & Branch Connections: MSS SP-97 — Branch connection alternatives

• Carbon Steel Plate: ASTM A516 & A36 — Material context for carbon steel flanges

• Stainless Steel Plate: Grades 304, 316, 321 — Material context for stainless flanges

FAQ SCHEMA

Q: What is the difference between ASME B16.5 and EN 1092-1 flanges?
A: ASME B16.5 (American) and EN 1092-1 (European, replacing older DIN 2501) are the two main flange standards globally — but they are not interchangeable. ASME uses a Class system (150, 300, 600, 900, 1500, 2500) with inch-based sizing (NPS) and UNC threads. EN uses a PN system (PN2.5 through PN420) with metric sizing (DN) and ISO metric threads. The bolt circle diameters, number of bolt holes, flange thicknesses, and facing dimensions differ between standards even at similar pressure ratings. You cannot bolt an ASME flange to an EN flange without custom transition pieces or complete redesign.

Q: Is Class 150 the same as PN16?
A: No. Class 150 and PN16 are NOT the same and the flanges are physically incompatible. While they serve similar pressure ranges at room temperature (Class 150 carbon steel rates 285 psi / 19.6 bar at 38°C, and PN16 rates 16 bar at 20°C), the dimensional standards differ: ASME Class 150 has 190.5mm bolt circle for 4-inch flange; EN PN16 has 180mm for DN100. Bolt counts may differ. Flange thicknesses differ. Facing geometries differ. Treating Class 150 as equivalent to PN16 in procurement causes project assembly failures. For approximate matching: Class 150 ≈ PN20 (not PN16), but the flanges are still incompatible dimensionally.

Q: What is the difference between DIN and EN flange standards?
A: DIN (Deutsches Institut für Normung) was the older German standard, with DIN 2501 being the most common pipe flange standard. EN (European Norm) standards replaced DIN at the European level: EN 1092 superseded DIN 2501 for steel flanges. In current practice, "DIN flange" almost always refers to an EN 1092-1 flange in the European market — the EN standard incorporated most DIN dimensions. However, EN 1092 has a wider scope and some refined specifications. When specifying flanges for European projects, reference EN 1092-1 (the current standard) rather than the superseded DIN 2501.

Q: What does PN mean in flange standards?
A: PN stands for "Pressure Nominal" (Pression Nominale in French) and approximately represents nominal pressure in bar at reference temperatures (usually 20°C or 38°C). PN6 means approximately 6 bar nominal pressure; PN100 means approximately 100 bar nominal pressure. However, actual pressure rating depends on the material grade and operating temperature — a PN16 carbon steel flange rates 16 bar at 20°C but drops to 13.5 bar at 200°C. Common PN ratings include PN6, PN10, PN16, PN25, PN40, PN63, PN100, with higher ratings (PN160 through PN420) used for special high-pressure applications.

Q: Which flange standard should I use for international projects?
A: Use ASME B16.5 for projects owned/specified by American operators or EPC contractors, located in North America, the Middle East, parts of Africa, and Latin America, especially in oil & gas, petrochemical, and refinery service. Use EN 1092-1 for projects owned/specified by European operators or EPC contractors, located in Europe, parts of CIS, and Africa with European links, especially in water treatment, HVAC, and general industry. For projects involving equipment from multiple regions, standardize project-wide on one standard and use transition flanges only at defined interface points. For oil & gas globally, ASME B16.5 is increasingly the default specification.

Q: How do I convert between Class and PN ratings?
A: There is no exact conversion because ASME Class and PN are different systems with different temperature derating curves and material standards. Approximate equivalences exist:

• Class 150 ≈ PN20 (sometimes PN16 in practice)

• Class 300 ≈ PN50

• Class 600 ≈ PN110 or PN100

• Class 900 ≈ PN150

• Class 1500 ≈ PN260

• Class 2500 ≈ PN420

However, the flanges are physically incompatible due to dimensional differences, and the temperature-pressure ratings will differ for the same material between standards. Use these as approximate guides for selecting equivalent pressure ranges, but never substitute one for the other in procurement without confirming dimensional and material compatibility.

Q: What materials are used in ASME vs EN flanges?
A: ASME flanges use ASTM material specifications: ASTM A105 (carbon steel), A350 LF1/LF2/LF3 (low temperature carbon), A182 F11/F22/F91 (alloy steel), A182 F304L/F316L/F321 (stainless), A182 F51/F55 (duplex). EN flanges use EN material specifications: P250GH/P265GH (carbon steel), 13CrMo4-5/10CrMo9-10 (alloy), 1.4301/1.4307/1.4401/1.4404 (stainless), 1.4462/1.4501 (duplex). The materials are nominally equivalent but specific chemistry, mechanical properties, and heat treatment requirements differ. When specifying flanges, always reference the appropriate material standard (ASTM or EN) for your project, not just generic descriptions like "carbon steel" or "316L stainless."