Flange Seal ASME/ANSI B16.20 Spiral Wound Gaskets Hot Trends and Applications

A spiral wound gasket made to ASME/ANSI B16.20 pairs a preformed metal winding with a flexible graphite filler, so the joint holds its seal while the winding carries the bolt load. That mix of spring-like resilience and a soft, temperature-tolerant filler is why the design is specified on hot, high-pressure joints, where ordinary flange gaskets lose their recovery after a few thermal cycles.

How a Spiral Wound Gasket Is Built

Every spiral wound gasket to ASME/ANSI B16.20 relies on four parts working together. The winding supplies the spring force, the filler takes up the surface irregularities of the flange, and the rings keep the assembly in place during bolt-up and service.

• Metal winding - preformed strip, usually stainless steel, wound with the filler in a V pattern so the assembly compresses and recovers like a spring.
• Flexible graphite filler - soft, compressible and stable at elevated temperature, it flows into machining marks and keeps the medium inside the joint.
• Outer centering ring - locates the gasket on the flange and limits outward flow of the filler under bolt load.
• Inner ring - stops the filler from extruding toward the bore and reduces turbulence at the pipe wall.

Because the winding recovers, the gasket keeps its sealing stress through thermal cycling and pressure swings. In the field that shows up as tolerance for slightly warped or misaligned pipe flanges that would crush a flat sheet gasket and start a leak.

Note: select the gasket by flange size, pressure class and facing. A mismatched element cannot be corrected by bolt load.

Where Spiral Wound Gaskets Are Used

The same construction works across industries that handle hot, high-pressure or chemically aggressive media:

• Oil and gas - refineries, petrochemical units and pipelines, sealing flange connections on hot hydrocarbon lines.
• Chemical processing - plants handling corrosive substances, where the graphite filler resists attack and prevents leaks that would break process integrity.
• Power generation - steam lines, boiler systems and turbine auxiliaries, where the seal must survive repeated thermal cycling.
• Water treatment - intake and distribution piping, where the gasket resists water, treatment chemicals and changing temperatures.
• Food and beverage - processing equipment, where the closed construction gives a clean sealing surface.

Demand is strongest wherever a joint must stay tight without frequent re-torque, which is exactly the service condition the spiral wound design was developed for.

Current Trends and Selection Points

Four trends shape how these gaskets are specified today.

• Sensor-equipped gaskets and predictive maintenance - seal integrity is monitored in real time instead of being inspected on a fixed calendar.
• Lower-impact materials - manufacturers keep developing fillers and windings with sustainability in mind.
• Custom designs - sizes, materials and performance targets are set for a particular joint rather than taken from a catalogue.
• Digital simulation - virtual testing of gasket behaviour helps optimize the selection before the joint is ever assembled.

For selection, three details decide whether the joint will hold: the correct flange size, pressure class and facing; a filler that suits the medium and the operating temperature; and a controlled bolt load during assembly.

Frequently Asked Questions

What does flexible graphite add to a spiral wound gasket?

It gives the gasket its conformability and temperature tolerance. The soft filler flows into flange surface irregularities while the metal winding keeps the sealing stress, so the joint stays tight through thermal cycling.

Can a spiral wound gasket be reused after the joint is opened?

No. The winding takes a permanent set under bolt load and the filler is already compressed. Fit a new gasket whenever the joint is reassembled.

Why does a spiral wound gasket leak after bolt-up?

The usual causes are a wrong size or pressure class, uneven bolt load, a damaged centering ring or filler, and flange faces that are not parallel. Correct the cause before re-torquing.

When is an inner ring required?

Add an inner ring on high-pressure or high-temperature joints and with soft fillers, where the filler would otherwise extrude toward the bore and disturb the flow.

How do I match the gasket to the flange?

Check the flange size, pressure class and facing first, then confirm that the winding and the filler suit the medium and the operating temperature of the joint.