Flange Sealing & Seating Stresses (y and m values)
Gasket selection relies on standard ASME boiler and pressure vessel code parameters:
- Min. Seating Stress (y): The minimum initial compression stress (psi) needed on the gasket's contact face to deform the material and seal minor flange scratches, even before pressure is applied to the pipeline.
- Gasket Factor (m): The multiplier ratio of excess gasket compression stress to internal pipeline pressure required to prevent joint blowout under service loads.
Summary of Gasket Properties:
- Spiral Wound Graphite: High performance. The stainless metal winding resists blowout, while graphite filler handles high temperatures and steam.
- PTFE (Teflon): Virtually inert to almost all chemicals (including concentrated sulfuric acid). Highly compressible, but prone to creep at elevated temperatures.
- EPDM Rubber: Excellent for water networks. High compressibility, but fails in hot steam or hydrocarbons.