ROC Carbon Type MB carbon/graphite compressor seal rings
are typically double-face seals that provide a critical
seal to prevent fugitive emissions. The seals are installed
over the shaft and are sandwiched between the rotating seal
ring and stationary sleeve . The hardness of the carbon
and the lubricating properties of the graphite combine to
provide a long-life seal; typical service life is one to
two years, depending on the application. Type MB compressor
seal rings have an outer metal ring that reinforces the
carbon/graphite material. The ring prevents damage to the
carbon/graphite during handling and installation and preserves
seal geometry in high-speed service.
ROC metal-backed seals are available in standard replacement
styles and in custom configurations designed to solve specific
Seal geometry is extremely important for proper service
life. The two seal faces must be identical so that the seal
will rotate at one-half speed relative to the rotating seal
ring, subjecting both seal faces to the same wear rate.
If the sides are not identical, one seal face will be subjected
to an excessive wear rate, shortening seal life. The roundness
of the seal assembly is also important, because ovality
causes eccentric seal rotation, leading to vibration and
premature seal failure.
ROC Carbon's manufacturing technology produces seal rings
with high-precision seal surfaces that are lapped and polished
for optimum sealing performance. Precise machining also
produces perfectly round seals, and careful shrink fitting
and stress relieving ensure that the seals retain their
roundness in storage and service.
Shrink Fitting and Stress Relieving
Material selection and close machining tolerances are critical
to maintaining optimum stress distribution in the seal assembly.
To prevent stress buildups that can shorten service life,
ROC Carbon follows a proprietary manufacturing procedure
that involves high-precision shrink fitting of the metal
ring over the carbon/graphite, as well as full stress relieving.
For added assurance of optimum geometry, larger ROC Carbon
Type MB seal rings are shipped with a precision-machined
carbon/graphite plug that helps prevent seal damage during
storage and handling. The plug is easily removed at installation.
The carbon/graphite material is chosen to be compatible
with the fluids being handled and with the mating seal surfaces.
Typical carbon grades used are in our A Series, which have
Shore Scleroscope hardnesses ranging from 50 to 90. For
operating temperatures above 500° F, high-temperature-treated
or metal-impregnated carbon/graphite is used. Metal for
the reinforcing ring is selected according to the metal's
coefficient of thermal expansion, which must be compatible
with that of the carbon/graphite in order to prevent unwanted
stress buildups during thermal transients. The metal also
has the appropriate corrosion resistance for the intended
For original equipment replacement parts, please furnish
the OEM part number or the specifications of the machine.
For custom-designed parts, we manufacture according to your
drawings, or, if you wish, we will design a seal for you.
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