Which flange material requires full-face gaskets on gas piping flanges?

Which flange material requires full-face gaskets on gas piping flanges?

• A. Bronze and cast iron
• B. Steel
• C. Aluminum
• D. Copper

Answer: (A)

Gasket coverage is tied to how cleanly and evenly the flange faces sit together. Full-face gaskets cover the entire flange face, including the bolt-hole area, to ensure a seal even if the mating surfaces are imperfect or not perfectly machined. Bronze and cast iron flanges are typically softer and can have more surface irregularities from casting and aging. In gas piping, where a small leak isn’t acceptable, using a full-face gasket ensures the seal spans the entire mating surface, including around the bolt holes, reducing the chance of leakage at the edges. Steel, aluminum, and copper flanges generally have flatter, more uniform faces, so a ring gasket that seals only in the bore is usually adequate for those materials. Hence, full-face gaskets are specified for bronze and cast iron to compensate for surface roughness and to maximize reliability in gas service.

Gasket coverage is tied to how cleanly and evenly the flange faces sit together. Full-face gaskets cover the entire flange face, including the bolt-hole area, to ensure a seal even if the mating surfaces are imperfect or not perfectly machined.

Bronze and cast iron flanges are typically softer and can have more surface irregularities from casting and aging. In gas piping, where a small leak isn’t acceptable, using a full-face gasket ensures the seal spans the entire mating surface, including around the bolt holes, reducing the chance of leakage at the edges.

Steel, aluminum, and copper flanges generally have flatter, more uniform faces, so a ring gasket that seals only in the bore is usually adequate for those materials. Hence, full-face gaskets are specified for bronze and cast iron to compensate for surface roughness and to maximize reliability in gas service.