Spiral Wound Gasket Frequently Asked Questions
Everything you need to know about spiral wound gaskets, ASME B16.20 standards, material selection, and proper installation for flange connections.
What is a spiral wound gasket and where is it used?
A spiral wound gasket consists of alternating layers of V-shaped metal winding strip and soft filler material (typically flexible graphite or PTFE). It is widely used in petrochemical, oil and gas, power generation, and chemical processing industries for flanged connections requiring high reliability under extreme temperature and pressure cycling conditions.
What does ASME B16.20 specify for spiral wound gaskets?
ASME B16.20 is the standard governing metallic gaskets for pipe flanges. It specifies dimensions, materials, tolerances, and marking requirements for spiral wound gaskets used with ASME B16.5, B16.47, and MSS SP-44 flanges. The standard ensures interchangeability and reliable performance across manufacturers.
What filler materials are available for spiral wound gaskets?
Common filler materials include flexible graphite (high-temperature up to 450°C, excellent chemical resistance), PTFE (superior chemical resistance, lower temperature limit 260°C), mica (extreme high-temperature up to 1000°C), and ceramic fiber (oxidizing environments). Graphite-filled gaskets are the most widely used due to their excellent sealing performance and broad chemical compatibility.
How do I identify the correct spiral wound gasket for my flange?
Gasket selection requires matching the flange standard (ASME B16.5, B16.47 Series A or B), pressure class (150, 300, 600, etc.), nominal pipe size, and flange facing type (raised face, flat face, RTJ). The gasket must also have the correct inner ring material for the process fluid and outer ring material for the flange material compatibility.
What is the difference between inner ring and outer ring in spiral wound gaskets?
The outer ring (centering ring) centers the gasket on the flange and provides radial support to prevent buckling. The inner ring protects the sealing element from process fluid erosion, prevents inward buckling, and acts as a compression stop. Inner rings are required for PTFE-filled gaskets and recommended for all applications above Class 300.