SUBJECT: Shaft displacement and the original equipment seal (O.E.M.) 11-7

The following picture describes a typical original equipment seal (O.E.M.) used in the process industry. It should run trouble free until the carbon face (B) wears away.

To experience long life with this type of seal:

Just about all original equipment seals (O.E.M.) leak long before the carbon faces wear out because this type of seal is very sensitive to shaft displacement. Here is a list of some of the common causes of the shaft and seal components to be axially and radially displaced:

Causes of axial displacement of the rotating shaft :

Remember that sleeve bearings allow a lot of axial movement. Precision bearings limit axial movement to thousands of an inch (hundredths of a millimeter), but can still allow enough radial movement to open lapped mechanical seal faces.

Causes of a radial displacement of the rotating shaft

Both radial and axial shaft displacement

The shaft is not centered in the stuffing box.

Vibration of the rotating shaft. There are multiple causes of vibration.

Along with the seal problems just mentioned, excessive radial movement of the shaft could cause contact between:

The excessive shaft displacement could also:

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