Thick-walled flanges for industrial use

Thick-walled flanges are critical components widely used in industrial systems to connect pipelines, pressure vessels, and heavy-duty equipment. What sets them apart is their increased wall thickness—typically 30% to 50% thicker than standard flanges—enabling them to endure extreme pressures, temperatures, and mechanical loads. Below, we explore their definitions, structural classifications, performance characteristics, manufacturing processes, and practical applications.

What Are Thick-Walled Flanges?

Thick-walled flanges are specially designed flanges manufactured either through integral forging or multi-layer welding. They are engineered for high-performance systems that require enhanced pressure resistance and structural reliability.

Main Types:

Integral Forged Flanges: Manufactured as a single piece for superior strength.

Multi-Layer Cladded Flanges: Constructed using layered structures for enhanced corrosion resistance and pressure tolerance.

Key Performance Features of Thick-Walled Flanges

1. Enhanced Mechanical Strength

Rated for pressure classes of PN160 or higher, exceeding standard flange capacity by 2–3 levels.

40% increase in ring stiffness, providing greater resistance to cyclic loading and pressure surges.

Excellent for environments with extreme temperatures, including:

High heat (>500°C)

Cryogenic applications (e.g., LNG systems)

Superior resistance to deformation and fatigue in dynamic systems (e.g., chemical reactors with frequent startup/shutdown cycles).

2. Superior Sealing Integrity

Typically paired with metal ring gaskets or spiral wound gaskets.

Precision-machined sealing faces—such as Raised Face (RF) or Ring Type Joint (RTJ)—ensure leak-proof performance under harsh conditions.

3. Material Versatility and Durability

Common materials include carbon steel, alloy steel, and stainless steel, often enhanced via heat treatment.

Carbon steel: Effective up to 480°C.

Alloy steel: Performs well at temperatures up to 560°C.

Stainless steel: Offers high corrosion resistance with Cr ≥ 17%.

4. Customizable Design Options

Tailored features such as neck height, bolt hole patterns, and flange face types can accommodate non-standard systems or specialized equipment like nuclear reactors.

Forging and Heat Treatment Processes of Thick-Walled Flanges

Forging Process Essentials

Utilize multiple heating and gradual deformation to prevent thermal cracking and over-stressing.

Maintain strict control of forging temperature and speed.

Apply precision forging dies and calibrated equipment to ensure dimensional accuracy and consistent quality.

Conduct surface treatment and stress-relief procedures prior to machining.

Heat Treatment Guidelines

Uniform heating and soaking to refine grain structure and achieve homogeneous material properties.

Carefully controlled cooling and tempering to balance strength and toughness.

Monitor temperature and duration throughout to avoid issues like phase transitions or cracking.

Typical Applications and Advantages of Thick-Walled Flanges

1. Extreme Operating Environments

Oil & Gas:

Natural gas compressor outlets (up to 25 MPa)

High-pressure transport pipelines

Offshore drilling wellheads

Refining:

Hydrogenation reactors (400°C+)

Nuclear Power:

Reactor vessel connections requiring radiation resistance

Thermal Power:

Steam lines using heat-resistant steel like 12Cr1MoV

Chemical & Petrochemical:

Hydrogenation towers, synthesis columns, and corrosive lines using plastic-lined or super austenitic stainless flanges

Heavy Industry & Marine:

Hydraulic press systems and ship shaft flanges exposed to vibration and torque

Aerospace & LNG:

Cryogenic tanks and engine pipelines needing low-temperature toughness or lightweight alloys (e.g., titanium)

2. Operational and Maintenance Benefits

Service life of sealing surfaces extended to 8–10 years, versus 3–5 years for conventional flanges.

Maintenance downtime reduced by over 60%, resulting in better system uptime and lower lifecycle costs.

Selection Criteria and Quality Control of Thick-Walled Flanges

Key Standards to Follow:

ASME B16.5, ASME B16.47

EN 1092-1

GB/T 9124

Manufacturing Notes:

Typically produced via open-die or closed-die forging.

Large-diameter flanges may combine casting and machining.

100% radiographic testing is required for weld seams.

Ultrasonic testing must meet Level II flaw detection standards.

Post-Weld Heat Treatment (PWHT) is mandatory for high-temperature service.

Failure Risk Mitigation:

Stress concentration: Addressed via smooth transition fillets.

Corrosion fatigue: Minimized through anti-corrosive coatings.

Thermal expansion issues: Solved by using flexible flange designs.

Why Flange Thickness Matters

The thickness of a pipe flange is directly related to the pressure and temperature conditions of the connected system.

Thick-Walled Flanges

Used for high-pressure, high-temperature services.

Prevent deformation and leakage in demanding environments.

Essential for critical systems like LNG terminals and nuclear power infrastructure.

Thin-Walled Flanges

Suitable for low-pressure, low-temperature operations.

Lightweight and cost-effective.

Ideal for general-purpose industrial piping where extreme conditions are not a concern.

Final Thoughts

The correct selection of thick-walled flanges dramatically enhances system reliability in critical infrastructure. With outstanding resistance to pressure, temperature, and cyclic loading, they are the go-to solution for high-performance piping networks. Engineers and procurement specialists must evaluate operating conditions, material compatibility, and total cost of ownership, and when needed, conduct stress simulations to ensure long-term safety and performance.