Which characteristic of a gasket must be checked before the gasket is installed in a flange?

• A. Check the size and rating stamped on the flanges
• B. Check the material type
• C. Check the color
• D. Check the date of manufacture

Answer: (A)

The most important thing to verify before installing a gasket is that it matches the flange size and pressure rating. The size and rating stamped on the flanges tell you the exact bore, bolt pattern, and class the joint must seal against. If the gasket doesn’t fit that size or isn’t rated for the service pressure, it won’t seal properly and can fail under operating conditions. Material type matters for chemical compatibility and temperature, but it won’t compensate for a mismatch in size or rating. Color is cosmetic and the date of manufacture is less relevant to immediate fit and performance.