Efficient Plant April 2020 - 25

feature | solution focus

Air Seal
Stops
Pulper
Leakage

The slurry that results in
this pristine paper was
leaking and destroying
the pulper shaft and
gearbox in a New York
mill. A new configuration,
with an air seal at its
core, solved the problem.

An air seal is at the center of a new pulper configuration that eliminated 20 hr. of annual downtime.
AN UPSTATE NEW York paper mill had
an ongoing problem with a leaking pulper.
Similar to other pulpers, it had significant
shaft runout caused by uneven distribution
when paper bales were dumped into it.
Many mixers, agitators, and pulpers experience similar shaft leakage. The material
weight in the bowls and any other movement, cause packing movement, contamination, and premature failure. If mechanical
seals are used in these applications, the
same movement, the abrasive stock mixture, contamination, and shock damage the
seal faces, again causing premature failure.
Impact of the problem was significant
and included:
 paper stock losses, housekeeping issues,
and stock disposal
 gearbox-oil contamination
 frequent packing replacement

APRIL 2020

EP2004fsolfocus.indd 25

 belt and shaft wear
 safety issues
 eventual gearbox and shaft replacement
 downtime with lost production.
The pulper leakage was nonstop. The
mill's team estimated the yearly loss at
$100,000. As tolerances were affected more
by the movement and related shaft wear,
losses would only increase. The stock also
had to be cleaned up and sent to a disposal
service. In addition to the housekeeping
labor costs, disposal costs were about
$25/ton.

ONGOING ISSUES
The packing that sealed the pulper was ineffective. To some extent, it helped minimize
shaft movement, but it also trapped pulp,
which then wore the shaft. The on-site team
replaced the packing every three months.

The pulper was down for 5 hr. for every
packing change.
The gearbox, located below the pulper,
also became a victim of the leaking. As the
stock fell on it, lubricating oil became contaminated with water and stock particles.
The maintenance team estimated that they
used about 5 gal. of oil weekly to replace the
contaminated oil. Though an oil seal was in
place, the contamination breached the seal.
As the pulp fell onto the gearbox, it also
contaminated the drive belt on the gearbox. The wear resulted in belt replacement,
including the cost of the material, labor
hours, and downtime.
Because the pulper was installed in a
vertical orientation, there was limited
workspace and performing the frequent
maintenance was difficult and dangerous.
Personnel worked in a contaminated space
EFFICIENTPLANTMAG.COM |

25

3/26/20 3:36 PM


http://www.EFFICIENTPLANTMAG.COM

Efficient Plant April 2020

Table of Contents for the Digital Edition of Efficient Plant April 2020

Efficient Plant April 2020 - Cover1
Efficient Plant April 2020 - Cover2
Efficient Plant April 2020 - 1
Efficient Plant April 2020 - 2
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Efficient Plant April 2020 - 4
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Efficient Plant April 2020 - Cover3
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