ASME B16.5/ B16.47 Buyer’s Guide Content Overview

• What Is ASME B16.5 and ASME B16.47?
• Differences Between ASME B16.5 and ASME B16.47 Flange Standards
• Stainless Steel Flange Types Available
• Flange Face Types and Sealing Surfaces
• Pressure–Temperature Ratings of ASME Stainless Steel Flanges
• Dimensional Requirements for ASME B16.5 and ASME B16.47 Flanges
• Manufacturing Process of Stainless Steel Flanges
• Quality Control and Third-Party Inspection
• Applications of ASME Standard Stainless Steel Flanges
• Frequently Asked Questions (FAQs) about Stainless Steel Flanges 
• Conclusion

S&S Stainless International is a professional manufacturer and exporter of ASME B16.5 and ASME B16.47 stainless steel flanges, supplying reliable solutions for industrial piping systems worldwide. These two flange standards, developed by the American Society of Mechanical Engineers (ASME), define the dimensional and performance requirements for pipe flanges used in high-pressure and high-temperature applications.

ASME B16.5 covers stainless steel flanges from ½ inch to 24 inches, while ASME B16.47 extends to larger sizes from 26 inches to 60 inches, making them essential for both standard and large-diameter pipelines. Both standards include multiple pressure classes, flange types, and face options, ensuring compatibility with global project specifications.

At S&S Stainless, all flanges are precision-machined and manufactured to meet strict quality and performance requirements. Whether you’re sourcing flanges for oil and gas, chemical processing, power generation, water treatment, or marine systems, our ASME-compliant flanges deliver proven performance, corrosion resistance, and long service life.

What Is ASME B16.5 and ASME B16.47?

ASME B16.5 and ASME B16.47 are internationally recognized standards that define the dimensions, tolerances, pressure ratings, and material requirements for stainless steel pipe flanges used in industrial piping systems.

ASME B16.5 applies to flanges sized from ½ inch to 24 inches (DN15–DN600) and includes pressure classes ranging from Class 150 to Class 2500. It covers the most commonly used stainless steel flange types, such as weld neck, slip-on, blind, threaded, socket weld, and lap joint flanges. These flanges are widely used in oil and gas, chemical, and power plant piping systems where strength, pressure containment, and dimensional precision are critical.

ASME B16.47, on the other hand, covers large-diameter flanges from 26 inches to 60 inches (DN650–DN1500).

Both standards ensure flange compatibility with ANSI/ASME piping components and define various flange facing types such as raised face (RF), flat face (FF), and ring-type joint (RTJ).

By selecting ASME B16.5 or ASME B16.47 stainless steel flanges, engineers and project managers can ensure proper sealing, alignment, and durability in demanding process environments. At S&S Stainless International, all flanges are manufactured to comply with these standards, offering peace of mind and long-term reliability for global industrial applications.

Differences Between ASME B16.5 and ASME B16.47 Flange Standards

When selecting stainless steel flanges for your piping system, it’s essential to understand the differences between ASME B16.5 and ASME B16.47, especially if your project involves large-diameter pipelines or high-pressure applications.

The most important distinction lies in the flange size range.

• ASME B16.5 applies to flanges from ½ inch to 24 inches (DN15–DN600)
• ASME B16.47 covers 26 inches to 60 inches (DN650–DN1500)

Because of this size difference, ASME B16.47 flanges are often used in pipeline systems, storage tank connections, and large industrial installations, whereas ASME B16.5 flanges are common in process piping, refineries, and plant-level connections.

Another key difference is in the design series for B16.47:

• Series A (MSS SP-44): Thicker, heavier flanges with higher pressure ratings
• Series B (API 605): Lighter flanges with a larger bolt circle, often used where space and weight reduction are priorities

In contrast, ASME B16.5 offers a broader variety of flange types, including slip-on, weld neck, socket weld, threaded, lap joint, and blind flanges, while B16.47 only includes weld neck and blind flanges.

Lastly, bolt patterns and dimensions between B16.5 and B16.47 are not interchangeable—even if they share the same nominal pipe size—making it crucial to specify the correct standard for your flange requirements.

Stainless Steel Flange Types Available

At S&S Stainless International, we manufacture and export a complete range of ASME B16.5 and ASME B16.47 stainless steel flanges, available in multiple types to suit different piping requirements. Whether your system demands easy alignment, secure sealing, or high-pressure durability, we provide the right flange type for reliable and leak-free performance.

Our stainless steel flanges are produced using high-quality materials like 304, 304L, 316, and 316L, and are available in pressure classes from 150 to 2500 (B16.5) and 75 to 900 (B16.47). Each flange is precisely machined, tested, and finished to meet international standards and project specifications.

We offer the following stainless steel flange types:

Each flange type is available with multiple face finishes—Raised Face (RF), Flat Face (FF), and Ring-Type Joint (RTJ)—depending on your sealing and pressure requirements.

With our extensive range of stainless steel flange types, S&S Stainless International supports a wide variety of applications in oil & gas, chemical processing, marine, power generation, and water treatment industries.

Flange Face Types and Sealing Surfaces

When selecting an ASME stainless steel flange, it’s essential to choose the correct flange face type, as it directly affects sealing performance, gasket compatibility, and pressure handling. At S&S Stainless International, we supply ASME B16.5 and ASME B16.47 flanges with three standard sealing face options: Raised Face (RF), Flat Face (FF), and Ring-Type Joint (RTJ).

Each face type serves a specific function based on the system’s pressure class, temperature, and media. Here’s how they differ:

Raised Face Flange (RF)

The raised face is the most commonly used sealing surface in ASME B16.5 stainless steel flanges. It features a small, elevated area around the bore where the gasket is seated. This design concentrates pressure on the gasket for a tighter seal.

• Suitable Pressure Classes: Class 150, 300, 600, 900, and 1500
• Applications: General-purpose piping systems, oil & gas, chemical processing
• Gasket Types: Spiral wound, ring gaskets, compressed fiber

Raised face flanges are versatile and compatible with most standard gaskets, making them ideal for a wide range of industrial environments.

Flat Face Flange (FF)

The flat face flange has a smooth, even surface across the entire sealing area. It is typically used in lower-pressure systems or when connecting to cast iron or fiberglass piping, where uneven stress could cause cracking.

• Suitable Pressure Classes: Class 150 and Class 300
• Applications: Water treatment, pump connections, non-critical systems
• Gasket Types: Full-face gaskets

Flat face flanges are designed to ensure full gasket contact and are commonly specified where flange deformation must be minimized.

Ring-Type Joint Flange (RTJ)

The RTJ flange has a precisely machined groove that holds a metal ring gasket, offering a metal-to-metal seal. This design is used in high-pressure, high-temperature environments where leak-tightness is critical.

• Suitable Pressure Classes: Class 600 and above
• Applications: High-pressure oil & gas, offshore drilling, steam lines
• Gasket Types: Oval or octagonal metal ring gaskets (R-series)

RTJ flanges are preferred in demanding applications where gasket performance and sealing integrity must be maintained under extreme conditions.

Pressure–Temperature Ratings of ASME Stainless Steel Flanges

The performance and safety of stainless steel flanges in industrial systems depend heavily on their pressure–temperature ratings. These ratings, defined by ASME B16.5 and ASME B16.47 standards, specify the maximum allowable pressure a flange can handle at a given temperature—based on the flange class and the material grade.

Each pressure class—Class 150, 300, 600, 900, 1500, and 2500—represents a pressure limit at ambient temperature. However, as the temperature rises, the pressure capacity of the flange decreases. For example, a Class 150 flange made from 316L stainless steel can operate at around 290 psi at 100°F, but this drops significantly to 75 psi at 800°F due to material strength reduction at elevated temperatures.

ASME pressure-temperature charts group materials by chemical and mechanical properties. Stainless steel materials are typically classified under:

• Group 2.1 – ASTM A182 304 stainless steel

• Group 2.2 –ASTM A182 316 stainless steel

• Group 2.3 – ASTM A182 304L and 316L stainless steel

These groups help engineers select appropriate flange ratings by considering:

• Tensile strength and allowable stress at high temperatures
• Gasket compatibility and bolting configuration
• Flange type, size, and sealing surface design

When choosing an ASME-compliant stainless steel flange, it’s critical to refer to the correct pressure–temperature rating table for your selected material group. Doing so ensures compliance with design codes, enhances system safety, and supports long-term performance in corrosive or high-pressure environments.

Dimensional Requirements for ASME B16.5 and ASME B16.47 Flanges

ASME B16.5 and ASME B16.47 define strict dimensional requirements for stainless steel flanges to ensure compatibility, sealing performance, and safe pressure containment in industrial piping systems. These dimensions are standardized to allow for consistent flange fabrication, global interchangeability, and reliable installation.

At S&S Stainless International, all stainless steel flanges are manufactured to meet the exact dimensional tolerances specified by these standards, ensuring precise fit and performance in your piping systems.

Key Flange Dimensions

Below are the main dimensions defined in ASME B16.5 and B16.47—and what each one means:

• Concentricity and Alignment Tolerances: Ensure the bolt circle, bore, and gasket faces are properly aligned, which helps avoid stress and uneven gasket sealing during assembly.
• Outside Diameter (OD): The total diameter of the flange, measured across the outer edge. This determines the flange’s physical footprint and compatibility with bolt patterns.
• Bolt Circle Diameter (BCD): The diameter of the circle on which the center of each bolt hole is located. It’s essential for aligning the flange with mating components.
• Number and Size of Bolt Holes: Specifies how many bolts are used and what diameter each bolt hole must be. This impacts pressure containment and sealing performance.
• Flange Thickness: The distance between the two faces of the flange (excluding raised face height). Thicker flanges are generally rated for higher pressure classes.
• Raised Face Height / RTJ Groove: For RF (Raised Face) flanges, this is the height of the sealing surface above the bolt face. RTJ (Ring Type Joint) flanges, it includes a machined groove for metal ring gaskets, critical in high-pressure systems.
• Bore Diameter: The inner opening of the flange, which must match the pipe’s outer diameter and schedule. This ensures smooth fluid flow and proper weld connection (for weld neck and slip-on flanges).
• Hub Dimensions (Weld Neck Flanges): These include the taper, length, and outer diameter of the hub. The tapered hub distributes stress more evenly when welded to the pipe.
• Facing Finish & Flatness (Runout): Defines the surface texture and flatness of the sealing face. A smooth finish ensures proper gasket compression, which is key to preventing leaks.

Dimensional Accuracy Matters

Choosing flanges with accurate dimensions ensures:

• Seamless pipe-to-flange alignment
• Proper gasket seating and compression
• Reduced risk of leaks, vibration, or flange failure
• Compliance with global engineering standards
• Efficient installation and maintenance

At S&S Stainless International, our ASME B16.5 and B16.47 stainless steel flanges are machined with precision and inspected for dimensional compliance to ensure long-term performance and peace of mind on your project site.

Manufacturing Process of Stainless Steel Flanges

At S&S Stainless International, every stainless steel flange is produced with precision, consistency, and strict adherence to ASME B16.5 and ASME B16.47 standards. Our manufacturing process combines advanced equipment, skilled engineering, and thorough inspection procedures to ensure that each flange meets international quality and dimensional requirements.

Understanding the manufacturing process of stainless steel flanges helps buyers assess product quality, lead time, and technical reliability. Below is a step-by-step overview of how we manufacture forged stainless steel flanges:

1. Raw Material Selection

The process begins with selecting high-quality stainless steel billets or bars in grades such as 304, 304L, 316, and 316L. All raw materials are certified and tested for chemical composition and mechanical properties to meet project specifications and international standards.

2. Forging

Flange blanks are created through hot forging, where stainless steel billets are heated to high temperatures and shaped under pressure using forging dies. This process improves the grain structure, increases strength, and enhances resistance to pressure and corrosion—essential for flanges used in high-stress environments.

3. Heat Treatment (Optional)

Depending on the grade and application, forged flanges may undergo heat treatment such as solution annealing to relieve internal stresses, improve toughness, and restore corrosion resistance after forging.

4. Rough Machining

The forged blank is then rough-machined to bring the flange close to its final dimensions. This includes shaping the hub, facing the body, and preparing the bolt circle and bore.

5. Drilling and Finishing

The flange undergoes precision machining, which includes:

• Drilling bolt holes with tight tolerances
• Facing the sealing surface (RF, FF, or RTJ) to required flatness and surface finish
• Boring the center hole to match the required pipe size and schedule
• Beveling the weld end (for weld neck and socket weld flanges)

6. Surface Treatment

Flanges are cleaned and finished using processes such as pickling, shot blasting, or machining, depending on customer requirements. This improves corrosion resistance and prepares the surface for shipment or coating.

7. Inspection and Testing

All flanges are subject to dimensional inspection and visual examination according to ASME standards. Optional tests such as:

• Hydrostatic testing
• Ultrasonic or magnetic particle testing
• Third-party inspections (SGS, BV, etc.)

are available upon request.

8. Marking and Packaging

Finished flanges are permanently marked with:

• Material grade
• Size and pressure class
• Heat number and standard (e.g., ASME B16.5)

They are then securely packed in wooden cases or pallets, with protective wrapping to prevent surface damage during transit.

Quality Control and Third-Party Inspection

At S&S Stainless International, product quality is at the core of everything we do. As an ISO 9001 certified stainless steel flange manufacturer, we follow a strict quality management system to ensure that every flange leaving our facility meets the dimensional, mechanical, and material requirements defined by the ASME B16.5 and ASME B16.47 standards.

To meet project-specific or regulatory requirements, we also offer third-party inspection services through globally recognized agencies such as SGS, Bureau Veritas (BV), and TÜV. These inspections can include dimensional verification, ultrasonic testing, magnetic particle testing, and hydrostatic testing, ensuring full compliance with client specifications and international quality standards.

By choosing S&S Stainless International, you’re working with a manufacturer that prioritizes product integrity, compliance with ASME standards, and global export readiness—a combination trusted by clients across industrial sectors worldwide.

Applications of ASME Standard Stainless Steel Flanges

ASME B16.5 and ASME B16.47 stainless steel flanges are widely used in critical piping systems where reliability, pressure containment, and corrosion resistance are essential. At S&S Stainless International, our flanges are engineered to meet the performance requirements of a wide range of industries and environments—delivering consistent sealing and structural integrity in both standard and high-demand systems.

Whether your application involves corrosive media, extreme temperatures, or high-pressure flow, ASME-compliant stainless steel flanges provide a secure and maintenance-friendly connection that is trusted by engineers worldwide.

1. Oil and Gas

Flanges are used in upstream, midstream, and downstream operations to connect pipelines, valves, pumps, and process equipment. Weld neck and blind flanges are especially common in high-pressure drilling and refining systems.

2. Petrochemical and Chemical Processing

Stainless steel flanges are ideal for handling corrosive fluids, acids, and solvents. ASME flanges ensure leak-proof performance and easy inspection in systems requiring frequent shutdowns or maintenance.

3. Water Treatment and Desalination

Slip-on and lap joint flanges are frequently used in water distribution, wastewater treatment, and desalination plants where corrosion resistance and cost efficiency are important.

4. Power Generation

In thermal, nuclear, and renewable energy facilities, flanges are used in high-temperature steam lines, heat exchangers, and condensate systems. RTJ and weld neck flanges are preferred for their ability to withstand extreme conditions.

5. Marine and Offshore

Stainless steel flanges are a critical component in shipbuilding, offshore platforms, and seawater cooling systems due to their resistance to chloride-induced corrosion and harsh environmental exposure.

6. Food, Beverage, and Pharmaceutical

Hygienic-grade stainless steel flanges are used in process piping for clean water, steam, and food-grade fluids. Flanges allow for easy cleaning, sterilization, and system reconfiguration.

Frequently Asked Questions (FAQs) about Stainless Steel Flanges 

1. What is the difference between ASME B16.5 and ASME B16.47 flanges?

ASME B16.5 covers stainless steel flanges from ½” to 24”, while ASME B16.47 applies to large-diameter flanges from 26” to 60”. B16.47 is further divided into Series A (heavier) and Series B (lighter), commonly used in pipelines and high-capacity systems.

2. Are ASME B16.5 and ASME B16.47 flanges interchangeable?

No, ASME B16.5 and ASME B16.47 flanges are not interchangeable. The two standards cover different flange sizes, and even if they had an overlapping size, their bolt patterns, bolt hole sizes, and dimensions would not match. Mating flanges from different standards can lead to leaks and are unsafe. Always ensure both flanges in a connection conform to the same standard.

2. What types of flanges are included in ASME B16.5?

ASME B16.5 includes several flange types such as weld neck, slip-on, blind, socket weld, threaded, and lap joint flanges, all designed for use in various pressure classes and industrial applications.

3. Which stainless steel grades are used for ASME flanges?

The most common grades are 304, 304L, 316, and 316L, offering excellent corrosion resistance and strength. Other materials like 317L, 321, and duplex stainless steel are also available for specific environments.

4. What is the function of the flange face type (RF, FF, RTJ)?

The flange face type determines the sealing method.
• Raised Face (RF): most common, suitable for standard pressure applications
• Flat Face (FF): used in low-pressure or cast-iron connections
• Ring-Type Joint (RTJ): for high-pressure, high-temperature environments with metal-to-metal sealing

5. What do PN ratings mean?

PN stands for “Pressure Nominale” and is a pressure rating system predominantly used in Europe. It’s a metric designation based on the ISO 7005 and DIN standards. The number after “PN” indicates the maximum allowable pressure in bars that a flange can withstand at a reference temperature of 20°C (68°F). For example, a PN16 flange is rated for 16 bars of pressure. This is a different system from the ASME Class ratings (e.g., Class 150, 300), which are based on a nominal pressure in pounds.

5. How do I select the right pressure class for my flange?

The pressure class (e.g., 150, 300, 600, etc.) depends on your system’s operating pressure, temperature, and pipe schedule. Higher classes are rated for more demanding conditions. Consult ASME pressure-temperature charts or contact our team for technical support.

6. Can I request custom flange sizes or third-party inspection?

Yes. At S&S Stainless International, we offer custom sizes, non-standard dimensions, and third-party inspection services (SGS, BV, etc.) based on your project specifications.

7. Do ASME B16.5 and B16.47 flanges include tolerance requirements?

Yes. Both standards specify dimensional tolerances for flange thickness, bolt hole alignment, face flatness, and more—ensuring compatibility, sealing integrity, and international compliance.

Conclusion 

S&S Stainless International is a trusted manufacturer and exporter of ASME B16.5 and ASME B16.47 stainless steel flanges, providing precision-engineered components to clients in the oil and gas, chemical, marine, water treatment, and power generation industries. Our flanges are manufactured to strict international standards, ensuring material traceability, dimensional accuracy, and compliance with pressure and sealing requirements.

We offer a complete range of weld neck, slip-on, blind, threaded, socket weld, and lap joint flanges, available in multiple pressure classes and sealing face types to suit diverse piping systems. From standard sizes to custom-engineered solutions, our production capabilities and rigorous quality control ensure reliable, long-term performance for critical industrial applications.

For technical support, product selection assistance, or a formal quotation, our knowledgeable sales and engineering team is ready to help. We also provide detailed product catalogues, dimensional drawings, and third-party inspection reports upon request.

To explore our full range of ASME-compliant stainless steel flanges or to request a quote, contact S&S Stainless International today and ensure your piping systems meet the highest standards of quality and reliability.

S&S Stainless Steel Flanges