SKF - Industrial Shaft Seals

Radial shaft seals
Table 14
Material family Description Shaft hardness recommended 1)
PTFE, unfilled
“Virgin” PTFE. FDA approved. Low-friction material. Used for
general non-pressure applications on shafts with low hardness
value. Excellent for cryogenics.
A
PTFE + glass
FDA approved. Glass can be in the form of beads or fibres. Glass is
exceptionally strong and prolongs the life of the base PTFE. Due to
its inherent hardness, it also adds an abrasive property and is not
recommended on low-hardness shafts.
C
PTFE + MoS 2
Molybdenum disulphide (MoS 2 ) adds wear resistance to the base
PTFE. Not as abrasive as glass.
C
PTFE + glass + MoS 2
Improved elongation characteristics and less abrasive to running
surfaces compared to PTFE + glass.
C
PTFE + carbon
Carbon can be in the form of various grades of fibres or graphite
powder, either natural or synthetic. Carbon is an excellent natural
lubricant and provides wear resistance to enhance the low-friction
base PTFE material. Increased percentage of carbon will increase
the wear, creep, and extrusion resistance and improve performance
in steam and chemical service at elevated temperatures and
pressures.
A, B, C
PTFE + carbon + MoS 2
Excellent wear rate in non-lubricated services at high
temperatures.
B, C
PTFE + bronze
Suitable for high-speed dynamic sealing of hydraulic media. Should
not be used in chemical service, which could attack the bronze.
PTFE + bronze + MoS 2
High degree of wear and extrusion resistance in high-pressure
applications.
PTFE + polymer
Polymers, such as polyoxybenzoate, polyimide and many others
improve creep and wear resistance.
A, B, C
PTFE + organic pigment
FDA and/or USDA 3A approved.
1) Material selection recommendations for counterface hardness ratings (Rockwell C scale) combined with surface speed.
For material selection, please see table 16
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