Why Upgraded Class 600 Spiral Wound Gaskets Are Reducing Leaks in Critical Flange Connections

Upgraded Class 600 spiral wound gaskets are cutting leak rates in critical flange connections across refineries, power generation and process plants. Built to ASME B16.20 with a 316 stainless steel winding, flexible graphite filler and both inner and outer rings, they keep the seal where flange gaskets see pressure and thermal cycling.

ASME B16.20 and the Class 600 Baseline

ASME B16.20 sets the dimensional, material and performance rules for metallic gaskets in flanged joints, so a Class 600 spiral wound gasket seats the same way whatever the maker. The Class 600 rating covers services up to about 1,440 psi depending on temperature, per ASME pressure-temperature ratings. Specifying to the standard is the first step to fewer leaks in critical connections.

• Metallic winding in 316 stainless steel for corrosion resistance and strength.
• Flexible graphite filler for sealing integrity and thermal stability.
• Inner ring as a compression stop; outer ring for centring and blowout resistance.
• Class 600 rating, about 1,440 psi at moderate temperature.

Design and Materials

The 316 stainless steel winding carries the mechanical load and resists aggressive media, while the flexible graphite filler flows into the face serrations and stays resilient through pressure swings. The spiral wind adds elasticity: the gasket recovers under thermal cycling instead of taking a set, so bolt load stays effective and the joint keeps sealing between maintenance outages.

Inner and Outer Rings

• Inner ring in 316 stainless steel stops the sealing element buckling inward.
• It shields the graphite from the process stream and limits flange-face erosion.
• Outer ring centres the gasket in the flange assembly during installation.
• The outer ring also resists blowout and protects against over-compression.

Performance in Critical Service

A tighter seal pays off three ways. Fewer fugitive emissions and product losses lift plant efficiency — pumps and compressors stop compensating for lost fluid. Emission control improves, with lower releases of volatile organic compounds and fewer headaches under environmental rules such as those of the US Environmental Protection Agency. And fewer unplanned outages cut the total cost of ownership.

In the Joint

The gasket sits between the flange faces and the bolts preload it into the serrations; the pipe flanges carry the pipe loads that try to open the joint. Match the gasket class to the flange rating, torque in stages and in a cross pattern, and replace the gasket every time the joint is opened.

Selection and Installation

Confirm the pressure class and temperature first — Class 600 covers about 1,440 psi only where the ASME pressure-temperature table allows it. Then pick the winding and filler for the media: 316 stainless steel with graphite suits steam, hydrocarbons and most chemicals. Check the flange facing, keep the faces clean, and never reuse a compressed gasket.

Frequently Asked Questions

What does Class 600 mean for a spiral wound gasket?

It is the pressure-temperature class: about 1,440 psi at moderate temperature, derated as temperature rises, per ASME B16.20 and the ASME pressure-temperature ratings.

Why does a spiral wound gasket need an inner ring?

The inner ring acts as a compression stop, keeps the sealing element from buckling inward and shields the graphite filler from the process media.

When is 316SS with graphite filler the right choice?

Choose it for steam, hydrocarbons and aggressive chemicals where corrosion resistance, thermal stability and recovery under cycling matter.