An SS outer ring, in the context of spiral wound gaskets, refers to a solid, often carbon steel, ring that serves as a centering and support structure for the gasket within a flange joint. It helps to accurately position the gasket, provide radial strength to prevent blowout, and act as a compression limiter. 

Here's a more detailed breakdown:

Purpose:

• Centering and Support:

  The outer ring ensures the gasket is properly aligned within the flange joint. 

• Radial Strength:

  It adds stability and helps prevent the gasket from blowing out under pressure. 

• Compression Limiter:

  It acts as a stopper to prevent excessive compression of the gasket, which can damage the seal. 

Material:

• The outer ring is typically made of carbon steel, often with a corrosion-resistant treatment. 
• It can also be made of high-grade steel. 

Types:

• Outer Ring Only:

  A simple outer ring used with flat face and raised face flanges, suitable for Class 900 and below.

• Inner & Outer Rings:

  Gaskets with both inner and outer rings provide additional compression limiting on both sides of the gasket, suitable for higher pressure applications and corrosive media. 

Applications:

• Spiral wound gaskets with outer rings are commonly used in various industrial applications involving high pressure and temperature, such as:
  • Oil and gas pipelines
  • Chemical plants
  • Power stations
  • Pharmaceutical industry