External Mechanical Seal

The figure provided here illustrates a single external seal. The term “single” indicates only one sealing surface is provided, and the term “external” indicates the sealing surface is outside the stuffing box.

This type design is not very common, but it has certain advantages over the internal seal. The main advantage is that the seal can be adjusted after installation.

Here’s a description of the key elements of this type of mechanical seal:

The pump shaft is indicated by “A” in the illustration.

The rotating element (“C”) is mounted on the shaft. It rotates along with the shaft. There is no relative movement between the rotating element and the shaft. An O-ring is usually installed between the rotating element and the shaft – this O-ring is indicated by “D” in the illustration. The interface between the O-ring and the shaft is referred to as the “Static Seal Point of Rotating Unit to Shaft”.