Classification of Mechanical Seals

Mechanical seal classification by arrangement:
Dual seals

Pressurized external fluid mechanical seal
Pressure between seals is higher than seal chamber pressure (typically min. 30 psig).

External fluid lubricates both sets of faces.

Leakage to the atmosphere is external fluid.

Is also called a "Double seal".

Un-pressurized external fluid design
Pressure between seals is lower than seal chamber pressure (typically atmospheric).

External fluid only lubricates the most outside set of faces. The most inside faces are lubricated with the pumped fluid. The most outside seal serves as a safety seal or containment device.

Leakage to the atmosphere is external fluid, possibly mixed with small amounts of pumped fluid.

Is also called a "Tandem seal".

Faces can be configured in several ways: face to back, face to face and back to back.

Next: Classification by configuration, i.e. design

Classification of Mechanical Seals

Mechanical seal classification by arrangement: Dual seals

Mechanical seal classification by arrangement:
Dual seals