Industrial seal self study guide - SKF.com

Chapter 6—Wear Sleeves
How Shafts Wear
Seals operate with a closely controlled interference at the interface.
Continuous contact between a rotating shaft and a seal produces shaft
polishing friction. Under normal conditions, the friction causes a slight
wear track on the shaft (fig. 6a). However, as operating conditions
begin to worsen, shaft wear can accelerate. Dust, heat, dirt, shaft
speed, lack of lubrication, and even a cocked seal can cause the seal
lip to groove the shaft. Mechanical eccentricities can cause direct,
metal-to-metal contact between the seal and shaft surface.
The ultimate result is a leak.
How to Identify Seal Worn Shaft Surfaces
It’s not always easy to identify seal-worn shaft surfaces. The shaft may
be visibly scored or grooved. You can catch your fingernail in a wear
groove. A new seal that leaks soon after it’s installed is another telltale
sign of shaft damage.
The shaft surface can become so deeply grooved and worn that
a new seal will not eliminate leaks, nor compensate for the shaft
damage (fig. 6b).
Seal replacement does not solve the problem. The new lip will ride in
the rough, worn seal track and the new seal will leak and wear out
quickly.
Three solutions are possible:
• Reworking or metallizing the shaft surface at a machine shop—
high cost, requires hours of downtime.
• Replacing the shaft—Also expensive, with machine downtime.
• Installing a wear sleeve—Comparatively low in cost, virtually no
downtime, longer life.
Wear sleeves correct shaft damage instantly with the least amount of
downtime and cost. Wear sleeves require no special preparation or
machining of the shaft for installation. Applied over the damaged shaft,
a wear sleeve makes the shaft usable again. It eliminates shaft leaks
and smooths out damaged surfaces. And often the new shaft finish
created is better than the original.
SKF offers two types of wear sleeves: Speedi-Sleeves ® , for nominal
shafts .472” to 8.000” (12.00 to 203.20mm), and large diameter wear
sleeves, for shafts 8” to 45” (203.20 to 114.300mm). Made of
carbon steel and chrome-plated, the wear sleeve resists corrosion
in a wide range of applications.
Shaft
O.D.
W
As a seal continuously contacts
a rotating shaft, it creates shaft
wear (fig. 6a).
Shaft surface can become so
deeply grooved and worn that a
new seal will not eliminate leaks,
nor compensate for the shaft
damage (fig. 6b).
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