Effective Diameter


In metal bellows seal terminology it is the calculated diameter where the pressure penetrates between the metal plates.

This number is used to determine the hydraulic balance diameter of the mechanical seal face.

In the above drawing the effective diameter would be about half way across the bellows span, placing about 70% of the seal face area above the line and 30% of the seal face area below the line.

Unlike O-ring type seals, the effective diameter of a bellows design can alter with a change in stuffing box pressure, causing a shift in the seal face balance ratio.