This article covers the key marking requirements for four major categories: steel pipes (ASME B36.10 & B36.19), flanges (ASME B16.5), butt-weld fittings (ASME B16.9), and forged fittings (ASME B16.11). All these standards follow the general marking principles defined in MSS SP-25.

About MSS SP-25 – General Marking Regulation

MSS SP-25 is the universal standard marking system for valves, flanges, fittings, and unions used in industrial piping systems. Published by the Manufacturers Standardization Society (MSS), this standard defines consistent rules for marking content, location, method, and durability. It is widely referenced by major ASME standards, including ASME B16.5, B16.9, and B16.11.

The main purpose of MSS SP-25 is to ensure clear product identification, material traceability, pressure rating recognition, and safe installation. It specifies mandatory items such as manufacturer identification, material grade, size, pressure class, standard number, and heat number.

In short, MSS SP-25 serves as the common foundation for marking all ASME B16 series piping products.

ASME B36.10 & B36.19 – Marking for Steel Pipes

ASME B36.10M (for carbon steel pipes) and ASME B36.19M (for stainless steel pipes) are dimensional standards. They only define outer diameter, wall thickness, tolerance, length, and bevel requirements. These two standards do NOT include any marking requirements.

Marking for steel pipes must follow the applicable material specification, such as:

• ASTM A53, ASTM A106, API 5L for carbon steel
• ASTM A312, ASTM A213 for stainless steel

Typical marking:

• Manufacturer’s logo or trademark  (Optional)
• Product Name
• Pipe Type (seamless or welded)
• Size
• Length
• Material grade
• Standard
• Heat number

For example: PIPE SMLS 1/2″ X 6MTR ASTM A106 GR.B SCH STD ASME B36.10 ZZ2570

ASME B16.5 – Flange Marking

ASME B16.5 is the standard for pipe flanges and flanged fittings. It includes clear and detailed marking requirements, based on MSS SP-25.

Typical marking contents:

• Manufacturer’s trademark (Optional)
• Flange Name
• Nominal size
• Pressure class
• Hub Thickness (for weld neck flange)
• Sealing Face
• Material
• Standard
• Heat number (mandatory for cast steel flanges)

Sequence of the marking do not have strict regulation.

For example: SHZC 4″ #2500 SCH40 RTJ WN FLANGE ASTM A350 LF2 ASME B16.5 ZZ0440

ASME B16.9 – Marking for Butt Weld Fittings

ASME B16.9 covers factory-made butt-weld fittings, including elbows, tees, reducers, and caps. Its marking requirements follow MSS SP-25.

Typical marking examples:

• Manufacturer’s identification mark (Optional)
• Fitting Name
• Fitting Type (seamless or welded)
• Material grade
• Nominal size
• Standard
• Heat number

A complete marking shows like: 90DEG LR SMLS 3IN SCH80 ASTM A234 WPB ASME B16.9 ZZ0188

ASME B16.11 – Forged Steel Fittings Marking

ASME B16.11 applies to socket-weld and threaded forged steel fittings. Marking rules are clearly defined and based on MSS SP-25.

Typical marking examples:

• Manufacturer’s mark (Optional)
• Fitting Name
• Fitting Type (SW or THD)
• Material
• Pressure rating
• Nominal size
• Standard
• Heat number

Such as: 90DEG DN20 3000# BSPT ASTM A105 ASME B16.11 ZZ0250

Conclusion

Understanding marking requirements for ASME B16 and B36 series products helps ensure correct material selection, quality control, and site compliance.

• ASME B36.10/B36.19 pipes: No marking requirements — follow material standards.
• ASME B16.5 flanges, B16.9 butt-weld fittings, B16.11 forged fittings: Follow their own standards plus MSS SP-25.

Correct marking improves traceability, reduces installation errors, and supports long-term reliability in industrial piping systems.

In short, we generally follow the formula below:

Manufacturer’s mark+Name+Type+Size+Material+Standard+Heat Number

Some parts of the marking contents can be deleted when the marking space is limited. And sequence of the marking do not have strict regulation. But below 5 parts cannot be omitted anytime.

Mandatory content: Type+Size+Material+Heat Number

Custom markings are also commonly applied as agreed with customers.

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EN 1092-1 Type 04 is a loose plate flange designed for use with a Type 34 weld-neck collar. It is a non-welded, rotatable flange plate that fits around the weld-neck collar and provides easy bolt hole alignment during installation.

This flange does not contact the conveying medium directly, as the sealing and pressure resistance are provided by the matching weld-neck collar. Type 04 is widely used in European piping systems for corrosion-resistant lines, easy assembly, and frequent maintenance scenarios.

Design Features of Type 04 Loose Plate Flange

Type 04 loose plate flange has clear and practical structural characteristics.

• Loose and rotatable design for easy bolt hole alignment
• No welding required on the flange itself
• Works only with Type 34 weld-neck collar
• Flat and simple plate structure
• Reduces installation difficulty and on-site labor time
• Protects expensive alloy or stainless steel pipes
• Standard dimensions ensure interchangeability
• Suitable for medium-pressure piping systems

The rotatable feature is especially useful in large-bore or restricted installation spaces.

How Loose Plate Flange Works with Type 34 Weld-Neck Collar

EN 1092-1 Type 04 loose plate flange must be used together with Type 34 weld-neck collar. The Type 04 flange plate is placed over the pipe first, and then the Type 34 weld-neck collar is welded to the pipe end.

The loose flange can rotate freely to align bolt holes easily during installation. The sealing surface is provided by the face of the Type 34 collar, while the Type 04 flange provides the clamping force. This combination is widely used for stainless steel and alloy pipelines to protect expensive piping materials and simplify assembly.

EN Approved Materials for Flange Type 04

Type 04 loose plate flanges are produced using common EN standard materials to meet industrial requirements.

Carbon steel materials

• S235JR
• P235GH
• P265GH

Stainless steel materials

• 1.4301 (304)
• 1.4401 (316)
• 1.4404 (316L)

Material selection depends on the application environment, including temperature, pressure, and corrosion level. The matching Type 34 collar is usually made of the same material as the pipeline.

Sealing Surface Options

Type 04 loose plate flanges support standard sealing faces in line with EN 1092-1.

• Raised Face (RF) – Most commonly used for general applications
• Flat Face (FF) – Used for low-pressure systems
• Other types available upon specific project requirements

Sealing performance depends on the matching gasket and the end face of the Type 34 weld-neck collar.

Where to Use Type 04 Loose Plate Flange?

EN 1092-1 Type 04 loose plate flanges are widely used in many industrial fields.

• Stainless steel and alloy piping systems
• Chemical and petrochemical processing lines
• Food, beverage, and pharmaceutical industries
• Water treatment and utility pipelines
• Corrosive medium applications
• Systems requiring frequent disassembly and maintenance
• Large-bore pipelines where alignment is difficult

Type 04 flanges are especially preferred where installation convenience and corrosion resistance are both required.

Contact Us

As a professional engineering manufacturer, Zizi Engineering Co Ltd offers full-process services—from cutting, forming, grinding to welding and assembly—help you shorten supply chains, cut costs, and boost project efficiency.

We welcome inquiries from project developers, contractors and enterprise clients to whom we will offer professional technical support and efficient manufacturing services. 

Look forward to being your reliable partner.

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EN1092-1 Slip-On Flanges (Type 01) are standardized steel pipe flanges, designed and manufactured in strict accordance with EN1092-1 European standard for wrought steel flanges and their joints. As a widely applied connection component in industrial piping systems, they are recognized for their cost-effectiveness, simplified installation process, and reliable sealing performance. Thus they are preferred choice for medium and low-pressure industrial applications across global markets.

Design Features of Type 01 Slip-On Flanges

The design specification of EN1092-1 Slip-On Flanges Type 01 is defined by the European Committee for Standardization (CEN), ensuring uniform dimensional tolerances, material requirements, and performance benchmarks.

Unlike weld neck flanges, Type 01 slip-on flanges feature a straightforward structure: the flange is slipped over the outer surface of the connecting pipe, then secured with fillet welds on both the inner and outer circumferences of the flange hub. This design reduces installation complexity, shortens construction time, and lowers welding requirements. Besides, it maintains sufficient structural integrity for standard industrial operating conditions.

Sealing Surface Options for EN1092-1 Flanges

The sealing surface of EN1092-1 Slip-On Flanges Type 01 follows EN1092-1 standard specifications, typically adopting a type A-flat face (FF) or type-B raised face (RF) design.

Type A: The flat face (FF) is suitable for low-pressure (PN≤10) and non-toxic media pipelines, ensuring simple sealing with standard gaskets.

Type B: The raised face (RF) is designed for medium-pressure (PN10-PN16) systems, providing enhanced sealing performance by increasing the contact pressure between the flange and gasket.

Both designs are compatible with EN-standard gaskets (non-asbestos, PTFE, graphite), effectively preventing media leakage and ensuring compliance with industrial safety requirements.

EN Approved Material for Flanges Type 01

Materials for EN1092-1 Slip-On Flanges comply with European material standards and EN1092-1 specification requirements, with carbon steel as the primary option for general industrial use. The core European material grades include EN 10025 S235JR, S275JR (carbon structural steel), EN 10213 C22.8 (carbon steel for pressure equipment), and EN 10222-2 P235GH, P265GH (pressure vessel carbon steel). For corrosive media environments (such as petrochemical and marine pipelines), stainless steel grades EN 1.4301 (304 equivalent), EN 1.4401 (316 equivalent) are available. Alloy steel grades (e.g., EN 1.7182) are optional for high-temperature, medium-pressure industrial systems, ensuring full compatibility with EN1092-1 standard requirements.

PN16 EN1092-1 Type 01 Slip-On Flanges Dimension

Quality Control for EN1092-1 Flange

Quality control of EN1092-1 Flanges is implemented throughout the manufacturing process, in strict accordance with EN1092-1 and relevant European industrial standards. All flanges undergo strict dimensional verification to ensure consistency with EN1092-1 standard tolerances; material composition analysis is conducted to confirm compliance with specified European steel grades; and pressure testing (hydrostatic testing or pneumatic testing) is performed to verify sealing performance and pressure-bearing capacity.

Additionally, surface treatment (such as hot-dip galvanizing, anti-rust painting, or pickling and passivation) is available to enhance corrosion resistance and extend the service life of the flanges.

Where to Use Type 01 Slip-On Flange?

EN1092-1 Type 01 Slip-On Flanges are widely applied in industrial sectors that adopt European standards, including oil and gas transmission, petrochemical processing, power generation (thermal power, hydropower), water treatment, chemical engineering, and general manufacturing. Their adaptability to medium and low-pressure systems, combined with cost-effectiveness and easy installation, makes them an indispensable component in modern European-standard industrial piping networks.

Summary

EN1092-1 Slip-On Flanges Type 01 adhere to EN1092-1 European standards, featuring standardized design, compliant European material grades, reliable performance, and wide application scope. Whether for standard specifications or custom requirements, these flanges provide a practical and economical piping connection solution, fully meeting the high standards of global industrial customers who adopt European piping systems.

Choose Us

As a professional engineering manufacturer, ZIZI Engineering Co Ltd offers integrated one-stop solutions, covering manufacturing, customization, and sales. Our full-process services—from cutting, forming, grinding to welding and assembly—help you shorten supply chains, cut costs, and boost project efficiency.

We welcome inquiries from project developers, contractors and enterprise clients to whom we will offer professional technical support and efficient manufacturing services. 

Look forward to being your reliable partner.

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What are EN1092-1 Flanges?

EN1092-1 is a European standard for steel flanges. Flanges are flat, circular discs with holes that connect pipes, valves, pumps, and other equipment in a piping system. Think of them as “bridges” that hold pipe parts together tightly and securely.

The “EN” in EN1092-1 stands for “European Norm,” meaning this standard is used across Europe and many other countries worldwide. It sets clear rules for how flanges are designed, made, and sized. This ensures that flanges from different manufacturers work together (called compatibility) and are safe to use.

Key Features

EN1092-1 flanges have a few basic features that make them reliable.

• Size Markings: They use two easy labels: DN (nominal diameter, the size of the pipe opening) and PN (nominal pressure, how much pressure they can handle). DN ranges from 10 to 4000, and PN ranges from 2.5 to 400.
• Materials: Most are made of steel—like carbon steel, stainless steel, or alloy steel. The material choice depends on what the pipe carries (e.g., water, chemicals) and the temperature/pressure of the system.
• Sealing Faces: The part that touches the gasket (to stop leaks) comes in different types. The most common are flat face (FF) and raised face (RF)—simple designs that work for most jobs.
• Markings: Every EN1092-1 flange has clear labels, including the standard name (EN1092-1), DN, PN, material, and manufacturer. This makes it easy to choose the right one.

Common Types of EN1092-1 Flanges

There are different types of EN1092-1 flanges, each for a specific job. Here are the most common ones:

1. Slip-On Flanges (Type 01): These slip over the pipe and are welded in place. They’re cheap, easy to install, and good for low-pressure systems (like water pipes).
2. Weld Neck Flanges (Type 11): They have a long neck that’s welded to the pipe. Strong and durable, they’re perfect for high-pressure, high-temperature systems (like chemical plants) because they spread pressure evenly.
3. Blind Flanges (Type 05): These are like a cap—they close the end of a pipe. Useful for systems that might need expansion or maintenance later (you can easily remove them).
4. Threaded Flanges (Type 13): They have threads inside, so you can screw them onto a threaded pipe—no welding needed. Great for small pipes or places where welding isn’t allowed (like near flammable materials).

Why EN1092-1 Flanges Are Used Worldwide

EN1092-1 flanges are popular for simple reasons:

• Safe: The standard’s strict rules mean they’re less likely to leak or break, keeping workers and equipment safe.
• Compatible: Flanges from different brands fit together because they follow the same standard. No more guessing if a flange will work with your pipe.
• Versatile: They work in many industries—chemical plants, water treatment, energy, and more. Whether you’re moving water or chemicals, there’s an EN1092-1 flange for the job.

How to Choose the Right EN1092-1 Flange

Choosing the right flange is not difficult if you remember three things below:

• Check the DN: Make sure it matches the diameter of your pipe.
• Check the PN: Pick a flange that can handle the pressure of your system (don’t use a low-PN flange for high-pressure work).
• Consider the use case: For low pressure, slip-on flanges work well. For high pressure or temperature, go with weld neck flanges. If you need to close a pipe end, choose a blind flange.

Conclusion

EN1092-1 flanges are the reliable, standardized connectors that keep European industrial plants, water systems, and heating networks running safely. By understanding the basic types (like Weld Neck or Blind), the pressure rating (PN), the size (DN), and the material, it’s not a problem to make the right selection.

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Introduction: Why Fastener Choice Is Critical

In high-pressure environments like flange connections and pressure vessel fabrication, fastener selection directly impacts system integrity, safety, and operational reliability. Stud bolts and bolts serve fundamentally different engineering purposes in these applications. An incorrect choice can lead to gasket failure, leakage, joint separation, or catastrophic pressure release. This guide provides a targeted comparison and installation protocol specifically for pressurized flange and vessel applications.

The Core Distinction Stud Bolts vs Bolts: Application-Driven Design

Bolts (Hex Bolts/Cap Screws)

Typical Flange/Vessel Applications: Low-pressure or non-critical connections, temporary blinds, manway covers on atmospheric tanks, ancillary attachments.

Design: Integrated hexagonal head for tool engagement.

Installation: Torque applied directly to the bolt head.

Key Limitation in Critical Service: Prone to loosening under vibration/thermal cycling; creates uneven stress concentration; complicates alignment in multi-hole flange patterns.

Stud Bolts

Industry Standard for Critical Service: Permanent pressurized connections (ASME-coded flanges), pump/valve stations, heat exchangers, reactors.

Design: Headless threaded rod, typically with continuous or end threading.

Installation: Utilizes two nuts; torque is applied only to the nuts.

Primary Advantage: Superior fatigue resistance from even load distribution; allows for precise flange alignment; permits maintenance disassembly without disturbing the seated stud.

Selection Criteria for Pressurized Systems

Specify Stud Bolts When (Per ASME B16.5):

• All Process Piping Flanges (Class 150 through Class 2500).
• Pressure Vessel Main Flanges, especially for diameters >12″ or high-pressure service.
• Systems with Thermal Cycling or High Vibration (e.g., heat exchangers, compressor lines).
• Applications Using Compressible Gaskets that may require re-torquing.
• Where Corrosion Resistance is Critical (simpler to specify high-integrity materials like A193 B8/B8M).

Standard Bolts May Be Acceptable For:

• Low-Pressure, Non-Critical Vessels (certain ASME Section VIII, Div. 1 applications).
• Non-Pressurized Attachments (insulation jacketing, platforms).
• Temporary Maintenance Closures.
• Small, Low-Pressure Access Ports (though studs are often still specified for consistency).

Governing Standards & Material Specifications

Dimensional Standards

ASME B16.5: Defines stud bolt length based on Flange Pressure Class x Nominal Diameter.

ASME B18.31 / DIN 2510 / ISO 3506: Govern stud dimensions, thread lengths, and tolerances.

Critical Material Standards (ASTM)

Critical Note: For sour service (H₂S present), NACE MR0175/ISO 15156 compliance is mandatory. This often requires specific heat treatment (e.g., A193 B7M).

Installation for Joint Integrity

Pre-Installation Protocol

• Material Verification: Confirm all components (studs, nuts, washers) match the specification sheets and P&ID requirements.
• Thread Inspection & Lubrication: Clean threads thoroughly. Apply a uniform layer of approved anti-seize lubricant (e.g., nickel or molybdenum-based) to all threads. This ensures accurate clamp load and prevents galling, especially with stainless steel.

Step-by-Step Stud Bolt Installation for Flanges

Warning for Standard Bolts in Flange Applications

If engineering design permits standard bolts:

1. The bolt head should face the direction of easiest future access.
2. Use hardened washers under both head and nut.
3. A cross-pattern torque sequence is non-negotiable to prevent flange distortion.
4. Maintenance & Troubleshooting
5. Flange Leakage: Do not simply over-torque. Investigate for misalignment, gasket failure, improper bolt stress, or corrosion.
6. Nut Loosening: Indicates vibration, insufficient preload, or gasket relaxation. Consider all-metal lock nuts (A194 Grade 2H/8) for critical service.
7. Stud Fracture: Typically caused by over-torquing, thread galling, hydrogen embrittlement, or fatigue. Always replace with the correct ASTM-grade material and investigate the root cause.

Conclusion

For flanged connections in pressure piping and vessels, stud bolts are the unequivocal engineering standard. Their design is inherently superior for managing the challenges of sealing pressure, thermal expansion, cyclic loading, and maintenance. Standard bolts are reserved for general construction and non-pressure boundary attachments.

Final Authority: Always defer to the ASME Boiler and Pressure Vessel Code, P&IDs, and engineered specifications for final requirements. Proper selection, adherence to standards, and meticulous installation are the foundational pillars of leak-free, safe, and reliable pressurized system operation

Contact Us

Zizi Engineering Co Ltd is committed to providing one-stop solutions from drawing design, manufacturing to finished product delivery.

We welcome inquiries by call or drawing from project developers, contractors and enterprise clients. We will offer professional technical support and efficient manufacturing services. 

Look forward to being your reliable partner.

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ASME B18.2.1 Bolt & Material Standard Pairing Principle

To ensure structural integrity and compliance, bolts under ASME B18.2.1 standard must be paired with material standards. And ASTM standards represent mechanical strength, corrosion resistance, and temperature performance. The most common standards include ASTM A193 (high-temperature) and ASTM A320 (low-temperature). Generally, matching nuts for the bolts follow ASTM A194.

Notably, all listed materials fully comply with ASME B18.2.1 dimensional tolerances (Class 2A/3A threads for bolts) and are widely recognized in global industrial procurement.

Carbon Steel Bolt Grades (≈75% Industrial Usage)

Carbon steel is the dominant material for ASME B18.2.1 bolts materials, ideal for high-pressure, high-temperature, and low-temperature industrial applications. It balances strength and cost-effectiveness, with B7, B7M, B16, and L7M as the core mainstream grades.

Stainless Steel Bolt Grades (≈25% Industrial Usage)

Stainless steel is the standard choice for ASME B18.2.1 bolts in corrosive environments, with B8 (304 stainless steel) and B8M (316 stainless steel) as mainstream grades, offering excellent rust and corrosion resistance.

Key Compliance for ASME B18.2.1 Bolt Materials

• Dimensional Compliance: All bolts must meet ASME B18.2.1 thread (Class 2A/3A), shank diameter, and length tolerances—material grade compliance does not replace dimensional checks.
• Material Certification: EN 10204 3.1/3.2 test reports are mandatory for export and industrial use, verifying chemical composition and mechanical properties.
• Corrosion Compliance: B7M, L7M, and B8M must comply with NACE MR0175 for sulfide stress cracking resistance; stainless steel grades require ASTM B117 salt spray testing.
• Grade Matching: Strictly pair bolts with specified nuts (e.g., B16 with 7H nuts) to avoid load failure and non-compliance.

Common Material Selection Mistakes to Avoid

• Mismatching bolts materials and nut grades (e.g., B7 with non-2H nuts) reduces assembly strength and violates industrial norms.
• Using B7 (non-SSC resistant) in sour oil & gas environments—only B7M, L7M, and B8M meet NACE MR0175.
• Applying B7/B8 in sub -150°F conditions—L7M is the only suitable grade for extreme low temperatures.
• Using B8 (304 stainless steel) in chloride/marine environments—B8M (316) is required to prevent pitting corrosion.
• Overlooking ASME B18.2.1 dimensional specifications—material compliance alone does not guarantee assembly fit.

Quick Selection for ASME B18.2.1 Bolts

• General high-pressure (non-corrosive): A193 B7 + A194 2H
• Sour oil & gas (sulfide risk): A193 B7M + A194 2HM
• Ultra-high pressure/heavy-duty: A193 B16 + A194 7H
• Low-temperature/cryogenic: A320 L7M + A194 4M
• Mild corrosion (water/air): A193 B8 + A194 8
• Severe corrosion (marine/chemical): A193 B8M + A194 8M

Choose Us

As a professional engineering manufacturer, Zizi Engineering Co Ltd offers integrated solutions covering manufacturing, customization, and sales.

We undertake projects including industrial piping system assembly, prefabricated pipe spool fabrication, steel structure engineering, protective fencing, and custom non-standard metal components. Our full-process services—from cutting, forming, grinding to welding and assembly—help you shorten supply chains, cut costs, and boost project efficiency.

Contact Us

Zizi Engineering Co Ltd is committed to providing one-stop solutions from drawing design, manufacturing to finished product delivery.

We welcome inquiries by call or drawing from project developers, contractors and enterprise clients. We will offer professional technical support and efficient manufacturing services. 

Look forward to being your reliable partner.

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What is a Spiral Wound Gasket?

ASME B16.20 spiral wound gasket is a type of semi-metallic gasket designed specifically for sealing flange joints in high-pressure, high-temperature (HPHT) environments. It is constructed by spirally winding two distinct materials: a thin metallic strip (the “winding strip”) and a non-metallic filler material (the “filler strip”). The winding process creates a series of alternating layers of metal and filler, forming a flexible yet robust sealing structure. This unique design also allows them to withstand extreme operating conditions, making them a favorable choice for critical applications in oil and gas, petrochemical, power generation, and other heavy industries.

Key Components of a ASME B16.20 Spiral Wound Gasket

To understand how a spiral wound gasket works, it’s essential to acknowledge their core components. A typical spiral wound gasket consists of three main parts:

Winding Strip (Metallic Core)

The winding strip is the backbone of the spiral wound gasket, providing structural strength, pressure resistance, and temperature stability. It is usually made from thin, corrosion-resistant metal sheets that can withstand high stress without deforming permanently.

Common materials for the winding strip:

①304/304L Stainless Steel: The most widely used option, suitable for general-purpose applications and moderate corrosion resistance.

②316/316L Stainless Steel: Performs enhanced corrosion resistance, ideal for acidic or chloride-rich environments (e.g., marine, chemical processing).

Filler Strip (Non-Metallic Sealant)

The filler strip is the sealing element of the flange connection, responsible for filling in minor irregularities on flange surfaces and creating a tight barrier against leakage. It is made from compressible, heat-resistant non-metallic materials that can conform to flange textures under compression.

Common filler materials include:

①Flexible Graphite: The most popular filler, offering excellent high-temperature resistance (up to 650°C), chemical inertness, and resilience. It is applied in most industrial applications.

②PTFE: Known for its exceptional chemical resistance and low friction. Suitable for low to moderate temperatures (up to 260°C).

③Ceramic Fiber: Designed for ultra-high temperatures (up to 1,200°C), and suitable for boiler flanges and furnace connections etc.

Inner/Outer Rings (Optional Reinforcements)

Many flange gaskets include optional inner and/or outer metal rings (called “centering rings” or “anti-extrusion rings”) to enhance performance:
    – Outer Ring: Prevents the gasket from extruding between flange bolts under high pressure. It’s also helpful to center the gasket on flange face.
    – Inner Ring: Provides additional support for the inner diameter of the gasket, preventing deformation and improving sealing integrity in large-diameter flanges or high-pressure applications.

Applications of ASME B16.20 Spiral Wound Gasket

Thanks to its versatility and ability to withstand harsh conditions, spiral wound gasket is used in a wide range of industries and applications:

• Oil & Gas Industry: Pipeline flanges, wellheads, refineries, and petrochemical plants (handling crude oil, natural gas, and petrochemical products).
• Power Generation: Boiler flanges, turbine connections, and steam pipelines (withstanding high-temperature steam and pressure).
• Chemical Processing: Reactors, distillation columns, and chemical storage tanks (resisting corrosive acids, bases, and solvents).
• Pharmaceutical & Food Processing: Sanitary flanges (using FDA-approved fillers like PTFE to ensure product purity).
• Marine Industry: Shipboard piping systems (resisting saltwater corrosion and vibration).

In general, spiral wound gaskets are the go-to choice whenever a reliable seal is required. For example, when pressure up to 20,000 psi, temperature up to 1,200°C, or corrosive media.

Advantages of Spiral Wound Gasket

①Excellent Sealing Performance: 

The multi-layer sealing construction forms a robust barrier that prevents gas and liquid leakage in harsh industrial flange connections.

②High Temperature & Pressure Resistance: 

Ideal for extreme HPHT conditions, ranging from cryogenic temperatures to ultra-high temperatures (up to 1000°C or higher) and from vacuum to high pressure (typically up to 25MPa or more).

③Corrosion Resistance: It compensates for flange displacement caused by temperature and pressure fluctuations, maintaining long-term sealing integrity without performance degradation.

④Flexibility & Resilience: The spiral design provides flexibility, and allows gasket to adapt to flange movement without losing sealing integrity.

⑤Cost-Effective Reliability: Spiral wound gaskets realize a perfect balance between all-metal gaskets (lower cost) and non-metallic gaskets (higher durability).

Important Considerations When Choosing Flange Connection

To select the suitable spiral wound gasket under ASME B16.20, following factors should be considered:

• Operating Conditions: Determine the maximum temperature, pressure, and type of media (e.g., corrosive, non-corrosive) the gasket will be exposed to. This helps to choose the winding and filler materials.
• Flange Type: Match the gasket type to the compatible flange design (e.g., Type BX for RTJ flanges, Type RX for raised-face flanges).
• Size & Dimensions: Ensure the gasket’s inner diameter, outer diameter, and thickness match the flange specifications by strictly following ASME B16.20 standards.
• Material Compatibility: Verify that the winding and filler materials are compatible with the process media to avoid corrosion or degradation.

Key Installation Steps to Ensure Sealing Performance

• Preparation: Clean the flange sealing surface to remove scratches, rust, or residues of former gaskets—any impurities may compromise the sealing integrity.
• Inspection: Verify the gasket type and material to ensure they match the application requirements; check for any damage (e.g., cracks, deformations) before installation.
• Centering: Align the gasket accurately with the flange hole. Avoid forced insertion.
• Pre-tightening: Tighten the bolts gradually in a diagonal sequence to 30%-50% of the specified preload force, ensuring initial uniform compression.
• Final Fastening: Re-tighten the bolts to the designed torque value in multiple steps (at least 3 steps) in a diagonal sequence again, ensuring uniform stress distribution across the flange.
• Hot Tightening (if necessary): For high-temperature operating conditions, shutdown for re-inspection or hot-state re-fastening may be required after the system heats up to maintain sealing performance.

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Not long ago, we received an order from a Singaporean customer for ASTM A234 WPB carbon steel butt weld pipe fittings and ASTM A105 carbon steel forged steel flanges.

Although all products in this batch of orders are made of carbon steel, there are various types of products available

Butt Weld Fittings: butt weld 90 degree/45 degree elbows, butt weld equal/reducing diameter tees；

Forged Flanges: weld neck flanges, slip on flanges, blind flanges, etc.

Therefore, in terms of product quality control, customers have also put forward high requirements for us.

As a regular customer who has been cooperating for many years, we fully understand customer needs, conduct strict product testing, and send inspection photos and reports to customers via email, making it convenient for customers to timely understand the results of product quality inspection.

Without a doubt, our professional service has once again been highly recognized by our customers, and this batch of American standard welded pipe fittings and forged flange orders have been successfully delivered.

Purchase Details

ASTM A234 WPB Butt Weld Fittings

ASTM A234 WPB pipe fittings are a type of pipe made from carbon steel, which has good welding performance, mechanical properties, and corrosion resistance. The carbon content in its chemical composition should be less than or equal to 0.30%, and other alloying elements are added to enhance its performance. These fittings have high strength and hardness, while maintaining good plasticity, making them suitable for the manufacturing of various pressure pipelines and pressure vessels.

ASTM A234 is a material standard developed by ASTM International, which specifies the chemical composition, mechanical properties, heat treatment, impact testing, and other aspects of carbon steel and alloy steel butt welded pipe fittings. This standard requires materials to meet specific chemical composition requirements to ensure the strength and corrosion resistance of pipe fittings.

ASTM A234 WPB is the most commonly used carbon steel material in welded pipe fittings, with excellent low-temperature toughness, corrosion resistance, and high-temperature strength. It is mainly used in the manufacturing of high-pressure valves, pipe fittings, chemical equipment and other fields.

WPB is an abbreviation for the following English words:

W = WELDABLE / wrought

P = RELATED TO P NUMBER OF ALLOY MATERIAL

B = REFER TO MINIMUM YIELD OF MATERIAL

Characteristics of ASTM A234 WPB material

Chemical Composition

Mechanical Propertie

ASTM A234 WPB fittings have high strength and hardness while maintaining good plasticity.

ASTM A234 WPB fittings have excellent welding performance, making them easy to connect and maintain in pipeline systems, thereby improving the reliability and service life of the entire system.

Manufacturing Standard for Carbon Steel Buttwelded Pipe Fittings

The ASME B16.9 standard applies to buttwelded fittings with nominal sizes ranging from 1/2 inch (DN15) to 48 inches (DN1200), covering various common pipe specifications.

This standard is applicable to butt welded fittings made of various materials such as carbon steel, alloy steel, and stainless steel, and can meet the needs of different industrial environments.

Types of ASME B16.9 Butt Weld Fittings

According to ASME B16.9 standard, butt welded pipe fittings mainly include various product types such as butt welded elbows, butt welded tees, butt welded tees, reducers, butt welded pipe caps, and flanged short sections.

These different types of butt welded pipe fittings each have unique structures and functions, which can meet different installation requirements in pipeline systems.

ASME B16.9 Dimension of 90 Degree and 45 Degree Butt Weld Elbows

ASTM A105 Forged Flange

ASTM A105 carbon steel flange is a type of pipeline connection accessory forged from carbon steel raw materials. This flange has high strength and hardness, good corrosion resistance, and is inexpensive, so it is widely used in pipeline connections.

Characteristics of ASTM A105 material

Chemical Composition

Mechanical Properties

ASME B16.5 Forged Flange Standard

ASME B16.5 “Pipe Flanges and Flange fittings” is one of the most widely used standards in the field of forged pipe flange manufacturing, which specifies the design, manufacturing, inspection, and connection requirements of pipe flanges and flange fittings. It enables different manufacturers to replace forged flange products produced according to this standard, while meeting the structural strength and pressure bearing capacity required for different pipeline designs.

Types of Forged Carbon Steel Flanges

There are various types of carbon steel flanges, including weld neck flanges, slip on flanges, socket weld flanges, threaded flanges, lap joint flanges, and blind flanges. Suitable for connecting various forms of pipelines and equipment.

Class 300 WN Flange Size and Weight

Dimension of Class 150 Slip On Flange

Class 600 Blind Flange Dimension and Weight

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ASME B16.9 Butt Weld Fittings Dimensions Inspection

Port Diameter: Measure the inner and outer diameters of the main pipe and branch pipes to ensure compliance with design specifications.

Wall Thickness: Inspect pipe wall thickness using calipers or ultrasonic thickness gauges to guarantee pressure resistance meets standard requirements.

Total Fitting Length: Measure the total length of the main pipe and branch pipes to ensure proper alignment during on-site installation.

Branch Angle: Measure the connection angle between the branch pipe and main pipe (typically 45°, 90°, or custom angles) to ensure correct fluid flow direction.

ASME B16.9 Duplex Pipe Fittings Specification

UNS S32205 Pipe Fittings Chemical Composition

ASTM A815 UNS S32205 Pipe Fittings Mechanical Property

2205 Duplex Steel Pipe Fittings Dimensions

Buttweld Concentric Reducer Dimension

Buttweld Pipe Elbow Dimension

Nominal Size		Outside Diameter at Bevel	Center to End		Center to End			Center to Center		Back to Face
			90° Elbows	45° Elbows	90°  Elbows		45° Elbows	180  Returns
DN	NPS	OD	A	B	A		B	O		K
			3D	3D	LR	SR	LR	LR	SR	LR	SR
15	1/2	21.3			38		16	76		48
20	3/4	26.7	57	24	38		19	76		51
25	1	33.4	76	31	38	25	22	76	51	56	41
32	1 1/4	42.2	95	39	48	32	25	95	64	70	52
40	1 1/2	48.3	114	47	57	38	29	114	76	83	62
50	2	60.3	152	63	76	51	35	152	102	106	81
65	2 1/2	73.0	190	79	95	64	44	190	127	132	100
80	3	88.9	229	95	114	76	51	229	152	159	121
90	3 1/2	101.6	267	111	133	4、89	57	267	178	184	140
100	4	114.3	305	127	152	102	64	305	203	210	159
125	5	141.3	381	157	190	127	79	381	254	262	197
150	6	168.3	457	189	229	152	95	457	305	313	237
200	8	219.1	610	252	305	203	127	610	406	414	313
250	10	273.0	762	316	381	254	159	762	508	518	391
300	12	323.8	914	378	457	305	190	914	609	619	467
350	14	355.6	1067	441	533	356	222	1067	711	711	533
400	16	406.4	1219	505	610	406	254	1219	813	813	610
450	18	457.0	1372	568	686	457	286	1372	914	914	686
500	20	508.0	1524	632	762	508	318	1524	1016	1016	762
550	22	559.0	1676	694	838	559	343	1676	1118	1118	838
600	24	610.0	1829	757	914	610	381	1829	1219	1219	914
650	26	660.0	1981	821	991	660	406
700	28	711.0	2134	883	1067	711	438
750	30	762.0	2286	964	1143	762	470
800	32	813.0	2438	1010	1219	813	502
850	34	864.0	2591	1073	1295	864	533
900	36	914.0	2743	1135	1372	914	565
950	38	965.0	2896	1200	1448	965	600
1000	40	1016.0	3048	1264	1524	1016	632
1050	42	1067.0	3200	1326	1600	1067	660
1100	44	1118.0	3353	1389	1676	1118	695
1150	46	1168.0	3505	1453	1753	1168	727
1200	48	1219.0	3658	1516	1829	1219	759

Tolerances for Buttweld Fittings

ASME B16.9 Standard

This Standard covers overall dimensions, tolerances, ratings, testing, and markings for factory-made wrought buttwelding fittings in sizes NPS 1/2 through NPS 48 (DN 15 through DN 1200).

Standard Fittings. 

That the fitting was manufactured in conformance with this Standard, including all dimensional requirements, is certified by a prefix”WP” in the material grade designation marking.

Special Fittings.

That the fitting was manufactured in conformance with this Standard, except that dimensional requirements are as agreed between the purchaser and the manufacturer, is certified by a supple mentary suffix to the material grade designation marking as follows:

(a) “S58” of ASTM A960 applies for fittings in accordance with ASTM A234, A403, and A420.

(b) “S8” applies for fittings in accordance with ASTM A815.

(c) “SPLD” applies for fittings in accordance with ASTM B361, B363, and B366.

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The customer specifically requested that all flanges undergo solution annealing—a critical step for enhancing corrosion resistance and ensuring uniform mechanical properties.

At ZIZI, we understand the importance of heat treatment in stainless steel products. Our production team strictly adheres to ASME B16.5 standards and performs solution annealing to ensure superior performance, a smooth surface finish, and durability in harsh environments. Every flange we deliver reflects our commitment to quality, precision, and customer satisfaction.

Products List:

Inspection photos

ASME B16.5 Class 300 Weld Neck Flange

An Class 300 ASME B16.5 Weld Neck Flange is a type of high-pressure pipe flange designed to connect piping systems securely and withstand elevated temperatures and pressures.
The “Weld Neck” design features a long tapered hub that provides reinforcement at the weld area, reducing stress concentration and ensuring excellent structural integrity.

This flange type is commonly used in oil & gas, petrochemical, power generation, and offshore industries, where reliable and leak-free connections are critical.

Specification of ASME B16.5 Weld Neck Flanges

ASTM A182 F316 Forged Flange Chemical Composition

ASTM A182 F316 Forged Flange Mechanical Property

Class 300lb Weld Neck Flange Dimensions & Weight

Solution Treatment of Flanges

Solution treatment (or solution annealing) of flanges is a key heat treatment process used to improve the properties of certain materials (especially stainless steel and nickel-based alloy flanges), particularly corrosion resistance and machinability.

Which flanges require solution treatment?

Not all flanges require solution treatment; primarily stainless steel flanges, such as:

Austenitic stainless steel flanges such as 304, 304L, 316, 316L, 321, and 347

Special corrosion-resistant alloy flanges (such as Inconel, Duplex, and Hastelloy)

Note : A solution annealing temperature above 1950 °F [1065 °C] may impair the resistance to intergranular corrosion after subsequent exposure to sensitizing conditions in F 321, F 321H, F 347, F 347H, F 348, and F 348H. When specified by the purchaser, a lower temperature stabilization or resolution annealing shall be used subsequent to the initial high temperature solution anneal (see Supplementary Requirement S10)

SS316 Weld Neck Flange Benefits

High Pressure & Temperature Resistance
Excellent Leak Prevention
Enhanced Durability
Versatile Applications

Applications

Oil & Gas Pipelines

Petrochemical Processing Plants

Power Generation Systems

Water Treatment Facilities

High-Pressure Steam Lines

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