What surface finish is generally required for raised face flanges?

What surface finish is generally required for raised face flanges?

• A. 32-63 micro-inches
• B. 125-250 micro-inches
• C. 500-750 micro-inches
• D. 10-20 micro-inches

Answer: (B)

Raising a proper seal on a flange depends on how the gasket seating surface is finished. For raised-face flanges, the gasket seat needs enough texture so the gasket can embed slightly and form a tight seal under bolt load, but not so rough that it damages the gasket or causes leaks. The commonly specified finish for this surface is around 125–250 microinches (Ra). This range provides a balanced texture that promotes reliable seating for most gasket materials. Finishes much smoother (like 10–20 microinches) can prevent adequate embedding and lead to leaks, while much rougher finishes (500–750 microinches) can damage the gasket and create irregular sealing.

Raising a proper seal on a flange depends on how the gasket seating surface is finished. For raised-face flanges, the gasket seat needs enough texture so the gasket can embed slightly and form a tight seal under bolt load, but not so rough that it damages the gasket or causes leaks. The commonly specified finish for this surface is around 125–250 microinches (Ra). This range provides a balanced texture that promotes reliable seating for most gasket materials. Finishes much smoother (like 10–20 microinches) can prevent adequate embedding and lead to leaks, while much rougher finishes (500–750 microinches) can damage the gasket and create irregular sealing.