What Is an ASME B16.20 Spiral Wound Gasket
ASME B16.20, developed by the American Society of Mechanical Engineers (ASME), specifies the design, materials, dimensions, tolerances, and marking requirements for metal gaskets (including spiral wound gaskets, toothed combination gaskets, and ring-connected gaskets). It applies to pipe flanges covered by ASME B16.5, B16.47, and MSS SP-44 standards.
ASME B16.20 Spiral Wound Gaskets (SWG) are the most widely used sealing element for RF raised face flanges. The core structure consists of alternating V-shaped metal spiral wound tape and soft filler material, configured with inner and outer locating rings (D-type structure). The standard explicitly requires that the metal tape and filler material must not protrude from the sealing contact surface; under high temperature and high pressure conditions, an inner ring must be installed to prevent gasket blow-out failure.
|
Category |
Type |
Material Combination |
Filler |
Temperature Limit |
Typical Service |
Key Advantage |
|
Spiral-Wound |
SWG (D-type inner & centering ring) |
316L Winding |
Flexible Graphite / PTFE |
550–760°C |
Crude Oil, Natural Gas, Process Piping |
Excellent heat cycle & vibration resistance, perfect blow-out protection |
|
Grooved Metal |
Kammprofile |
316L Grooved Core |
Flexible Graphite / PTFE |
550–1000°C |
Refinery Compressors, Heat Exchangers |
Superior vibration & heat cycle resistance, lower bolt preload |
|
Ring Joint |
RJ (Oval / Octagonal) |
Carbon Steel / 304 / 316L / 347 / 410 |
None (All-metal) |
High temp & pressure |
High-pressure hydrogen, Heat Exchangers, Christmas Trees |
Extremely high sealing stress, ideal for extreme conditions |
D-type design is the standard configuration for Class 150–600.
Core Specifications
Standard：ASME B16.20-2023
Size Range：NPS 1/2"–60" (Class 150–2500#)
Sealing Surface Bite：Serrated RF flange bites into the filler layer to prevent blow-out
Compressed Thickness：4.45 mm (compressed to 3.30 mm ± 0.13 mm at Bolt Stress 172–250 MPa)
Marking：NPS + Class + filler (e.g. 4-600/150-600 FG)
Color Coding：316L winding (green), Flexible Graphite (grey stripes)
Mechanical Properties & Operating Range
Seal Stress：Minimum 10,000 psi (69 MPa), Maximum 30,000 psi (207 MPa)
Temperature Range：-240°C to 760°C (Graphite) / Higher (RJ all-metal)
Maximum Pressure：Class 2500# (RJ for high-pressure hydrogen)
Gasket Factor (m)：3.0
Compression Recovery：Excellent for temperature/pressure cycling.
Key Advantages
ASME B16.20 spiral wound gaskets offer several outstanding performance advantages, making them suitable for harsh industrial conditions:
* Superior Sealing and Resilience: The unique spiral wound structure combines high compressibility with excellent resilience, adapting to fluctuations in pipeline temperature and pressure, maintaining a stable seal, and effectively preventing flange leakage.
* Excellent High Temperature and Pressure Resistance: The product can withstand high temperatures up to 450°C (850°F) for extended periods, with a pressure capacity of up to 1500psi+, perfectly suited for high-temperature and high-pressure process piping conditions.
* Broad Media Compatibility: By combining different filler materials such as graphite and PTFE, it is compatible with various media including water, steam, gas, chemical solvents, and hydrocarbons, exhibiting excellent chemical compatibility.
* Standardized Design, High Versatility: Manufactured strictly according to ASME B16.20 standards, it boasts precise dimensions, high interchangeability, stable and controllable performance, and compatibility with all ASME standard flange systems.
With inner ring protection, the risk of failure is eliminated. The optional built-in inner ring can effectively prevent the gasket from shrinking, deforming and being blown off under high pressure, and isolate the medium from erosion, which can greatly improve the sealing reliability and service life under extreme conditions.
Applications & Industries
Crude Oil, Natural Gas, Process Piping (most common)
Refineries, Oil & Gas Pipelines, Offshore Platforms, High-Pressure Flanges
Boilers, Heat Exchangers, Critical Flanges in Compressors
Temperature/Pressure Cycling Environments (thermal expansion/contraction, bolt loosening).
FAQ
What is the difference between Spiral-Wound and Kammprofile?
SWG is more flexible and heat-cycle resistant; Kammprofile offers better vibration resistance, lower bolt preload, and is ideal for high-temperature heat exchangers.
Is zinc-coated outer ring available?
Yes, carbon steel zinc-coated outer rings are common, and 316L can be customized.
Can PTFE be used for high-temperature service?
Not recommended (limit 260°C); Flexible Graphite provides higher temperature resistance and is suitable for oil & gas.
Can non-standard wall thickness and length be supplied?
Yes, non-standard dimensions and lengths are fully supported.
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