What is the difference between a seal ring and a mechanical seal face?

A mechanical seal face is the friction pair of a complete assembly running against a counterface under controlled axial load. A seal ring is a simpler part that restricts the passage of fluid or gas at the shaft-to-housing interface, and it may be static, rotating, or segmented. Both are machined from graphite or carbon-graphite, but the selection criteria and tolerances differ.

Can segmented rings be manufactured?

Yes. The ring is machined and then sectioned to allow assembly without dismantling the shaft, while keeping the fit between segments. Quoting it requires the drawing or the reference part, plus the working temperature and medium.

What tolerances can be achieved?

Graphite and carbon-graphite machine to tight tolerances and accept good surface finishes. The achievable value depends on the grade, the grain size, and the geometry of the part, so it is defined against the drawing rather than generically.

Machined graphite seal rings for rotating equipment

Mechanical applications

Machine seal rings

Graphite and carbon-graphite seal rings for precision rotary and static applications.

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Machined seal ring

Also known as: Carbon-graphite rings · Segmented graphite rings · Shaft seal rings · Carbon seal segments

[ Technical summary ]

Graphite and carbon-graphite seal rings close the gap between a shaft and its housing, in rotating as well as static service. They are machined to precise flatness and diameter, sometimes in segments, and use the low friction and thermal stability of the material to seal without added lubricant. They are used in pumps, turbomachinery, industrial machinery, and chemical-process equipment.

[ Problem it solves ]

Limit leakage at a shaft-to-housing interface where an elastomeric ring cannot take the temperature or the medium, and where adding grease or oil is not acceptable.

Operating conditions

Rotary sealing
Static sealing
Face-to-face contact

When it is suitable

Temperature is outside the range of an elastomeric ring
The medium chemically attacks polymeric seals
Grease or oil cannot be added at the interface
Stable flatness and concentricity are required in service
The assembly accepts a rigid ring instead of an elastic one

When it may not be suitable

The seal must deform elastically to absorb wide tolerances
There are impact or repeated shock loads
The counterface is misaligned or carries abrasives
There is severe oxidation in air at high temperature without protection or impregnation

Process challenges

Leaks from wear
Ovalization and loss of flatness
Process contamination

Advantages

Machinable flatness and finish
Low dry friction
Compatibility with wide thermal ranges

Limitations

Oxidation in air at high temperature without protection
Lower mechanical strength than structural metals
Requires grade selection by load and environment

[ Critical selection variables ]

These variables define the grade and the geometry. Actual values are confirmed against the grade datasheet.

Operating temperatureDecisive
Differential pressureDecisive
Flatness and surface finishDecisive
Geometry and tolerancesDecisive
Fluid or medium in contactRelevant
Rotational speedRelevant
Counterface material and finishRelevant
Thermal and duty cyclingRelevant

[ Required material properties ]

Properties that guide selection. Numerical values come from each grade's datasheet.

Critical properties

Friction coefficient
Compressive strength
Flexural strength
Thermal expansion

Secondary properties

Impermeability
Self-lubrication
Dimensional stability
Machinability

[ Related ]

[ Frequently asked questions ]

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Technical content reviewed by ESGRAF — Last reviewed: September 8, 2026

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