1. The completed gasket is fitted into a steel ring of specific thickness. When the gasket is fitted into a flange and the bolt load is applied, flange closure is governed by the outer steel ring of the gasket. To further improve the pressure rating of the spiral wound gasket, a steel ring may be added to the inside. This also protects the windings (particularly the filler), from contamination, or attack by, the product.
2. The second usually compression control is not fitted to the gasket at all, but engineered into the flange. These Gaskets are called Unsupported Spiral Wound Gaskets.
Spiral-Wound Metal Gasket