At a Midwestern producer of tubular
steel products, measures taken to counteract
the effects of impact on a quench
tank roll made it difficult to remove and
replace the conventional pillow block
bearings that support the roll’s shaft.
The bearings were replaced with adapter
mount roller bearings that are easier
to install and also will be easier to remove.
The mill produces oil and gas well
casing steel and line pipe in diameters
from 7" to 16", with wall thicknesses up
to ?".
Previously, as the head end of a tube
entered the quench tank to be cooled,
impact tended to move the shaft that
supported the roll to one side because
the former bearings did not lock tightly
enough to the shaft. To keep the shaft
centered, the company welded steel
washers to the end of the shaft. This
made it difficult to remove and replace
the bearings. The company’s maintenance
planner and supervisor explains,
“Any time we changed a bearing, we had
to cut the washer off and dress the shaft.
If the bearing was there for a long time,
the mill scale, dirt and grease would
build up, and we couldn’t get the bearing
off of the shaft.”

The design of the replacement bearings
addresses this common problem by
incorporating a withdrawal sleeve into
each bearing. As the adapter nut is unthreaded,
the design automatically pulls
the tapered adapter sleeve from the assembly,
releasing the bearing from the
shaft without causing damage, which
saves both time and repair costs.

Bearing installation also could be
problematic for the mill. The company’s
maintenance planner says, “The bearings
we had on previously just had locking
collars with no taper at all. Because
things didn’t work there in the past, we
were just buying regular pillow blocks
and tapping them in place ourselves.”
To address the problem, the company
selected Rexnord ZA6215F adapter
mount roller bearings with Shurlok
technology for the application because
they incorporate features that eliminate
the previous installation and removal
problems. These bearings are utilized
in industries such as forestry, mining,
steel, cement/aggregate and air handling.
They come equipped with a positive
locking system, tapered mounting
sleeve, hourglass rolling elements and
super-finished raceways and rollers.
These features allow for quick and
easy installation, reduce shaft damage
caused by loose mountings, provide
three degrees of static and dynamic misalignment
and provide a cool running,
quiet, high speed and high load capacity
design. An innovative tapered sleeve design maintains mounting tightness
during operation, provides 35 percent
greater shaft grip than other adapter
sleeve bearings, and allows for better
shaft grip in the mill’s application.
To ensure a correct installation, the new
bearings incorporate SpyGlass Optical
Strain Sensing (OSS) technology,
which provides visual feedback that tells
the installer when the bearings have
been correctly tightened to the shaft.
The sensor incorporates materials that
respond to strain by changing reflected
light wavelengths. It is calibrated so
that the window stays clear until there is
enough strain on the locknut to provide
a sufficient load. At that point, OSS
window changes color, showing that the
bearing is correctly installed.
Operating conditions for the bearings
include the effects of impact, as well as
typical mill scale, dirt and grease. The
spokesperson says the bearings have
performed well since their installation
in early 2008. He reports that the
company is considering using them on
other applications in the mill based on
their combination of features and performance.