ASME B16.5 Flanges Standard

ANSI B16.5 Dimensions & Ratings

ASME B16.5 Flanges Standard

ASME B16.5 Standard Flanges: Dimensions | Specifications | Material Grade | Standards | About ANSI B16.5 | All Product Types

ASME B16.5 is the globally recognized standard for pipe flanges and flanged fittings covering sizes from ½″ to 24″ nominal bore and pressure classes ranging from 150 to 2500. This specification defines essential parameters such as flange dimensions, facing types, bolt hole configurations, pressure-temperature ratings, tolerance limits, and testing requirements. It is applicable to forged flanges made from carbon steel, stainless steel, alloy steel, and high-performance alloys.

At Nutech, we manufacture and export forged steel flanges that fully comply with ASME B16.5, offering superior precision, strength, and dimensional accuracy. Our flanges are available in various types including Weld Neck (WNRF), Slip-On (SORF), Socket Weld (SWRF), Threaded, Blind (BLRF), Lap Joint, and Ring Type Joint (RTJ) — with face types such as Raised Face (RF), Flat Face (FF), and RTJ, depending on pressure class and sealing requirements.

The B16.5 standard also governs flange thickness, bolt circle diameter, bolt hole size, and gasket compatibility — making it critical for high-pressure systems in refineries, petrochemical plants, offshore installations, and power generation facilities. We ensure strict adherence to machining tolerances, pressure-temperature charts, and dimensional accuracy by conducting comprehensive in-house testing and certification in line with EN 10204 3.1 / 3.2.

Backed by global export experience, our ASME B16.5 flanges are manufactured for projects requiring uncompromising quality and full traceability, with all products supplied with markings as per B16.5 specifications, including material grade, pressure class, heat number, and size.

Technical Overview of ASME B16.5 Flange Dimensions, Pressure Ratings, Face Types & Tolerances.

For complete technical details, including dimensions, pressure rating classes, weight charts, sizes, tolerances, and material specifications of our ANSI B16.5 Standard Flanges, please download the full Catalog PDF below.

ANSI B16.5 Standard Flanges in Sizes ½″ to 24″ and Pressure Classes 150 to 2500 for Industrial Piping Applications.

Technical Specifications of ASME / ANSI B16.5

Specification Details
Design Standard ASME B16.5 / ANSI B16.5
Flange Types Weld Neck (WNRF), Blind (BLRF), Slip-On (SORF), Socket Weld (SWRF), Threaded (TH), Lap Joint, Ring Type Joint (RTJ), and More
Size Range ½″ NB to 24″ NB (DN15 to DN600)
Pressure Ratings Class 150, 300, 600, 900, 1500, 2500 (PN20 to PN420)
Face Types Raised Face (RF), Flat Face (FF), Ring Type Joint (RTJ)
Drilling Template As per ASME B16.5 bolt circle diameter & bolt hole arrangement
Flange Thickness As per class and size, including tolerance as per ASME B16.5
Dimensional Tolerances Within ASME B16.5 tolerance limits for OD, thickness, bolt holes, and facing
Surface Finish Stock finish, serrated finish (spiral or concentric), smooth finish as per RF/RTJ specs
Marking Heat Number, Material Grade, Pressure Class, Size, Standard (B16.5)
Testing Dimensional, Hydrostatic (on request), PMI, Visual, and Surface Inspection
Documentation EN 10204 3.1 / 3.2 certificates, compliance with NACE MR0175, ISO 15156 (as applicable)
Application Industries Oil & Gas, Petrochemical, Power Generation, Water Treatment, Food & Beverage, Fire Protection Systems, Pulp & Paper, Shipbuilding, HVAC, Offshore
Origin Made in India (by Nutech Overseas)
Export Network USA, Europe, and Middle East

Complete Material Grade Chart - Class 150 ANSI B16.5

Material Category B16.5 Flange Grades
Stainless Steel B16.5 Flange ASTM A182 F304 / F304L / F304H, F316 / F316L / F316Ti, F310, F309S, F317 / F317L, F321 / F321H, F347 / F347H, F904L, ASTM A351 CF3 / CF3M / CF8 / CF8M / CF8C, DIN 1.4301, 1.4306, 1.4307, 1.4311, 1.4401, 1.4404, 1.4408, 1.4409, 1.4541, 1.4571, 1.4550, 1.4435, 1.4539
Duplex Steel B16.5 Flange ASTM A182 F51 / F52 / F53 / F54 / F55 / F57 / F59 / F60 / F61, UNS S31803 / S32205
Super Duplex Steel B16.5 Flange ASTM A182 F53 / F55 / F57 / F59 / F60 / F61, UNS S32750 / S32760
Carbon Steel B16.5 Flange ASTM A105 / A105N, ASTM A350 LF2, ASTM A694 F52 / F56 / F60 / F65 / F70 / F80, ASTM A216 WCB, DIN 1.0460 / 1.0402 / 1.0619, Die Steel, Mild Steel
Alloy Steel B16.5 Flange ASTM A182 F5 / F9 / F11 / F12 / F22 / F91, AISI 4130 / 4140
Nickel Alloy B16.5 Flange Nickel 200 / 201, ASTM B564
Monel B16.5 Flange Monel 400 (UNS N04400), Monel K500 (UNS N05500), ASTM B564
Inconel B16.5 Flange Inconel 600 / 601 / 625 / 690 / 718 / 783 / X750, ASTM B564
Incoloy B16.5 Flange Incoloy 800 / 800H / 800HT (UNS N08800), Incoloy 825 (UNS N08825), Incoloy 925, ASTM B564
Hastelloy B16.5 Flange Hastelloy C276 (UNS N10276), C22 (UNS N06022), C4, C2000, B2, B3, X, ASTM B564
Alloy 20 B16.5 Flange Alloy 20 / 20Cb-3, Carpenter® 20, ASTM B462
254 SMO B16.5 Flange SMO 254 / 6Mo, UNS S31254, DIN 1.4547, ASTM A182
Copper Nickel B16.5 Flange Copper Nickel 90/10 (C70600), 70/30 (C71500), UNS C71640, ASTM B61 / B62 / B151 / B152
Copper B16.5 Flange TP1, TP2, T1, T2, C10100–C12300, C14200–C17200, C21000–C71520, including C10930, C11000, C11400, C12000, C12200, C26000, C28000, C33000, C44300, C70600, etc.
Brass B16.5 Flange Grades 3602, 2604, H59, H62, etc.
Aluminium B16.5 Flange Aluminium Grades 5052, 6061, 6063, 2017, 7075, etc.
Titanium B16.5 Flange ASTM B381 Gr.1 / Gr.2 / Gr.4 / Gr.5 / Gr.7, UNS R50250 / R50400 / R50550 / R50700 / R52400 / R53400 / R56320 / R56400
Other Special Grades Al6XN, Tin Bronze, Aluminium Bronze, Lead Bronze, Nimonic 75 / 80A / 90

International Flange Standards We Manufacture & Supply

What is ASME B16.5 and why is it important in flange selection?

ASME B16.5 is a globally recognized standard that defines the dimensions, tolerances, pressure-temperature ratings, face types, and materials for pipe flanges and flanged fittings ranging from ½″ to 24″ nominal size (DN15–DN600). It is critical in flange selection because:

  • Ensures dimensional compatibility between pipes, valves, and fittings
  • Defines pressure class ratings from 150 to 2500 for different applications
  • Establishes tolerance limits and surface finishes for leak-free sealing
  • Specifies flange face types like RF, FF, and RTJ based on sealing needs
  • Recognized across industries: oil & gas, petrochemicals, power, and water treatment

Using flanges that meet ASME B16.5 guarantees system integrity, global compliance, and safety in pressurized piping environments.

What pressure classes are covered under ASME B16.5 flanges?

ASME B16.5 flanges are available in the following standard pressure classes:

  1. Class 150
  2. Class 300
  3. Class 400
  4. Class 600
  5. Class 900
  6. Class 1500
  7. Class 2500

These classes define the maximum allowable pressure the flange can withstand at various temperatures. Selection depends on design pressure, temperature, and material. For example, a Class 600 flange made of carbon steel may have a different pressure-temperature rating compared to one made from stainless steel. Always refer to ASME B16.5 pressure-temperature charts for accurate selection.

Why are dimensional tolerances critical in ASME B16.5 flanges?

Tolerances specified in ASME B16.5—even for outer diameter, flange thickness, bolt-hole spacing, and face flatness—aren’t just arbitrary limits; they ensure interchangeability, proper alignment, and seal integrity across piping components.

Why Tolerances Matter:

  • Diameter & Bolt Circle Tolerance

    Ensures exact bolt-hole alignment during assembly, preventing stresses or flange distortion during bolt-up. For flanges under 24″ OD, tolerances may be ±1/16″ (≈1.6 mm), ensuring smooth fitting

  • Thickness & Hub Dimensions

    Prevents under-thickness or excessive machining—critical for pressure containment. Thicker flanges risk extra material cost; thinner ones risk strength loss .

  • Surface Finish & Face Flatness

    Proper finish (e.g., spiral-serrated or concentric-smooth) and flatness prevent uneven gasket compression, avoiding leakage or blowout—especially in high-pressure applications

  • Why Not Tighter Than Specified?

    ASME intentionally defines tolerances based on the least accurate yet practical manufacturing methods. Tighter dims don’t yield better seal—in fact, they increase cost and complexity without adding safety

How to select the correct ASME B16.5 flange for a piping system?

Selecting the correct ASME B16.5 flange involves evaluating several key factors to ensure compatibility, safety, and efficiency in your piping system:

Key Selection Criteria:

  1. Nominal Pipe Size (NPS): Choose the correct size as per the connected piping
  2. Pressure Class: Match the pressure rating (e.g., Class 150, 300, 600, etc.) to system pressure and temperature requirements
  3. Flange Type: Pick based on connection method — e.g., Weld Neck for high pressure, Slip-On for low pressure, Blind for isolation
  4. Face Type: Ensure proper sealing by selecting RF, FF, or RTJ based on gasket and media
  5. Material Grade: Choose a flange material compatible with pipe material and fluid (e.g., ASTM A105, A182 F304, etc.)
  6. Standard Compliance: Ensure full compliance with ASME B16.5 dimensions and tolerances

Always refer to engineering design data and project specifications to make an informed flange selection that ensures long-term performance and compliance.

What is the difference between ASME B16.5 and ASME B16.47 flange standards?

While both ASME B16.5 and ASME B16.47 cover flanged components, they differ mainly in terms of size range, application scope, and dimensional standards:

Feature ASME B16.5 ASME B16.47
Size Range ½″ to 24″ (DN15 to DN600) 26″ to 60″ (DN650 to DN1500)
Application Standard industrial and process piping Large-diameter pipelines (e.g., storage tanks, water lines)
Flange Series Not applicable Series A (from MSS SP-44), Series B (from API 605)
Bolt Circle Diameter Standard bolt pattern Series A: heavier, wider BCD; Series B: lighter flange design
Pressure Ratings Class 150 to 2500 Class 75 to 900 (varies by series)
Common Flange Types Weld Neck, Slip-On, Blind, Socket Weld, Threaded Weld Neck and Blind flanges
Industry Use Oil & Gas, Petrochemical, Chemical, Power, Water Heavy industrial, large-scale piping systems

ASME B16.5 is used for standard-sized piping, while ASME B16.47 is specialized for large diameter flanges often used in heavy industrial installations.

What is the significance of pressure-temperature ratings in ASME B16.5 flanges?

The pressure-temperature (P–T) ratings in ASME B16.5 are critical because they define how much pressure a flange can safely withstand at a given temperature. These ratings vary based on:

Key Factors:

  • Material of Construction: Different materials (e.g., ASTM A105, A182 F304, F316) have different strength properties at high temperatures.
  • Flange Class: Higher class ratings (like Class 1500 or 2500) can handle greater pressures.
  • Temperature: As temperature increases, the allowable pressure decreases for any given flange material.
  • Gasket Type & Bolting: The combination of gaskets and bolts affects how the flange handles internal pressure under heat.

For example:

  • A Class 300 flange in ASTM A105 carbon steel has a pressure rating of 740 psi at 100°F, but only 260 psi at 800°F.
  • These values are published in pressure-temperature rating charts within the ASME B16.5 standard.

Always refer to the ASME P–T chart during design to ensure the selected flange meets both operational and safety requirements.

Which countries does Nutech export ASME B16.5 flanges to?

Nutech Overseas is a trusted manufacturer and global exporter of ASME B16.5 flanges, serving industries across multiple continents. We supply flanges to EPC contractors, oil & gas firms, and industrial users in:

  • United Arab Emirates (UAE) – Dubai, Abu Dhabi, Sharjah
  • Saudi Arabia – Dammam, Riyadh, Jeddah
  • Qatar – Doha
  • Oman – Muscat, Sohar
  • Kuwait – Kuwait City
  • Bahrain
  • Europe – Germany, Italy, Netherlands, Spain
  • USA & Canada
  • South East Asia – Philippines, Malaysia, Singapore
  • Africa – Egypt, Nigeria, South Africa

We provide custom markings, export-grade packaging, and complete documentation in compliance with international shipping and inspection standards.

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