LNG Process Area	Flange Application
Liquefaction Plant	Heat exchanger outlets, compressor connections
LNG Storage Tank	Inlet/outlet nozzles, vent lines
LNG Carrier Vessel	Cargo piping, spray lines, ESD valves
Loading Arm Systems	Swivel joints, disconnect couplings
Regasification Terminal	Vaporizer piping, send-out lines

These flanges are used in both cryogenic liquid and cold vapor service, requiring durable performance in dynamic thermal environments.

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Suitable Flange Materials for LNG Service

Material selection is crucial in cryogenic applications. The flange must retain toughness, ductility, and mechanical strength at temperatures approaching -162°C. Common materials include:

1. ASTM A350 LF2 (Carbon Steel – Low Temperature)

• Minimum Charpy impact test at -46°C

• Often used in non-critical cold vapor lines

• Cost-effective, but not suitable for cryogenic liquid exposure

2. ASTM A182 F304/F304L and F316/F316L (Stainless Steel)

• Good cryogenic properties

• Excellent corrosion resistance in LNG vapor service

• Commonly used in piping, valves, and flange assemblies

3. ASTM A182 F321 and F347

• Stabilized stainless steels for high thermal cycling

• Used in lines exposed to frequent temperature changes

4. Nickel Alloys (e.g., Inconel 625, Hastelloy)

• Superior cryogenic performance and corrosion resistance

• Applied in critical LNG transfer lines and submerged service

5. Aluminum Alloys

• Used in certain tank and heat exchanger components

• Lightweight and good low-temp resistance, but not widely used for flanges

sasaflange provides flanges in certified low-temperature materials with full MTC documentation and impact-tested grades.

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Types of Flanges Used in LNG Systems

The selection of flange type depends on pressure class, flow requirements, and accessibility. Common flange types for LNG service include:

1. Weld Neck Flange (WN)

• Strong and resistant to stress

• Ideal for high-pressure and cryogenic applications

• Provides smooth flow with minimal turbulence

2. Slip-On Flange (SO)

• Easier alignment, but lower strength

• Used in low-pressure vapor lines

3. Blind Flange

• Used to seal the ends of pipelines and vessels

• Essential for pressure testing and future expansions

4. Lap Joint Flange

• Works with a stub end

• Useful in systems requiring frequent dismantling

• Enables cost savings by using corrosion-resistant stub ends

5. Socket Weld and Threaded Flanges

• Less common in LNG due to limitations under thermal cycling

• Used in small-bore instrumentation or auxiliary lines

sasaflange manufactures ASME and EN standard cryogenic flanges with precision machining and dimensional accuracy suitable for LNG operations.

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Sealing Technologies for Cryogenic Flanges

Achieving a tight seal is particularly difficult at cryogenic temperatures due to gasket shrinkage, thermal cycling, and differential expansion.

Recommended Gasket Materials:

• Spiral Wound Gaskets (SS + PTFE/Graphite)
  Flexible and high pressure-tolerant

• Kammprofile Gaskets
  Superior sealing with a metal core and soft sealing layers

• Corrugated Metal Gaskets
  High recovery and good for cycling conditions

• PTFE Envelope Gaskets
  Excellent chemical and cryogenic resistance

Sealing Considerations:

• Use serrated flange faces to improve gasket grip

• Apply proper torque patterns to avoid uneven loading

• Install insulating kits where galvanic corrosion may occur

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Engineering Considerations for LNG Flanges

1. Thermal Contraction

• Metal shrinks at cryogenic temperatures

• Allowances must be made in pipe alignment and bolt torque

2. Insulation Compatibility

• Flanges may be wrapped in perlite, foam glass, or polyurethane insulation

• Vapour barrier and sealing must not interfere with flange access

3. Vibration and Expansion

• Use expansion joints to absorb pipeline movement

• Design bolting to resist dynamic loads

4. Non-Destructive Testing (NDT)

• Flanges in LNG service often require radiography and ultrasonic testing

• Material certification must include Charpy impact values

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Standards and Certifications

LNG low-temperature flanges must meet global engineering standards for material, design, and inspection:

• ASME B16.5 / B16.47 – Flange dimensions and pressure ratings

• ASTM A350 / A182 – Low-temp and stainless material grades

• EN 1092-1 – European standard flange dimensions

• MSS-SP-44 – Large diameter steel flanges

• ISO 28921-1 / 2 – Valve and flange standards for cryogenic service

• NACE MR0175 / ISO 15156 – Sour gas resistance if applicable

• EN 10204 3.1 / 3.2 – Material test certificate requirements

sasaflange supplies LNG flanges with full traceability, impact-tested certifications, and compliance with global codes.

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LNG Project Case Studies: Flange Application

Case 1: Floating LNG Production Unit (FLNG)

• Application: LNG loading line from liquefaction module

• Flanges: ASTM A182 F316L WN flanges, RTJ face

• Gaskets: Spiral wound with PTFE filler

• Features: Tested at -196°C with NDT and PMI verified

Case 2: LNG Import Terminal

• Application: Submerged send-out pump connection

• Flanges: Inconel 625 lap joint with stainless stub ends

• Gaskets: Kammprofile with graphite layers

• Features: Cryogenic insulation and fire protection coating applied

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Maintenance and Inspection

Routine inspection is vital for LNG system safety:

• Visual inspections for frost lines, leaks, or bolt loosening

• Torque checks on fasteners due to thermal cycling

• Periodic replacement of gaskets and sealants

• Corrosion checks around insulation breaches

sasaflange also offers post-installation inspection support and flange replacement kits for maintenance projects.

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Conclusion

Low-temperature flanges are foundational to the safe, efficient, and long-lasting operation of LNG systems. From liquefaction plants to regasification terminals, these flanges must meet demanding requirements in terms of material performance, dimensional accuracy, sealing reliability, and code compliance.

At sasaflange, we provide specialized flange solutions engineered for LNG environments, including cryogenic material grades, advanced sealing systems, and compliance with ASME and EN standards. Our flanges are manufactured to withstand extreme cold, vibration, and pressure, ensuring your LNG operation runs safely and smoothly.