Problem Solved: Engineers take on challenge of failing equipment at paper mill - Paper Technology International 2023 - Paper Technology International 2023 - Flipbook - Page 70

Problem Solved: Engineers take on challenge of failing equipment at paper mill - Paper Technology International 2023

PAPERTECHNOLOGYINTERNATIONAL
Problem Solved: Engineers take on challenge of failing equipment at paper mill - Paper Technology International 2023
Tony Pallone, Deublin Company
INTRODUCTION:
An important aspect of engineering is the application of math and science to solve real-world problems. Case studies illustrate the
role of engineering in analyzing, identifying and solving operational problems in a production environment.
An example can be found in the case of a large paper mill
in the southeastern United States incurring increased maintenance
cost and time spent servicing the machine’s aging steam system,
which had been installed in the mid 90’s. The mill’s primary pain
point was to address high levels of water in its oil lubrication
system which reduced equipment life and increased
downtime. There was also the danger of unforeseen
equipment failure. The company’s specifications made
an allowance for water levels in the oil lube system
up to 0.03%, but samples showed levels as high as
0.26%.
The mill’s current solution was to deploy and maintain
costly dehydrators to reduce the excess water. However, that
solution was merely a Band-Aid, treating only the symptoms without
addressing the root cause. The problem, moreover, was going to be
progressively worse over time, as the mill was routinely experiencing
bearing failures. Meanwhile, the temporary solution represented an
exorbitant expenditure for the company.
Engineers at Deublin Company, an American manufacturer
of rotary unions and steam joints, had an alternative idea. By
examining the problem and analyzing its root cause, they were able
to devise a solution to help reduce the machine’s overall operating
costs, improve dryer efficiency and even present an opportunity for
modernizing the machine’s existing steam joints.
Investigating the problem
The papermaking process involves combining pulp made
from cellulose fibers with water, then placing it onto a machine
to form it, dry it and ultimately produce rolls of paper. There are
separate sections within the machine for each of these tasks. Each
section makes use of rolling elements with bearings that need to be
kept lubricated, either with circulating oil or grease. Essential to the
machine’s operation is keeping its lubrication system free of water
contamination.
This can be especially challenging in the machine’s dryer
section, where critical drying takes place in the paper making
process. This is achieved, in part, by drying cylinders heated by
steam supplied through steam joints, as shown in Figure 1.
At this particular paper mill, the steam joints were at least
20 years old, and each contained a carbon steel journal insulating
sleeve. When functioning normally, these sleeves would create air
cavities to provide thermal insulation from convective heat transfer
of steam. Boundary air and the sleeve material would protect the
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Figure 1: Essential to the machine’s operation
is keeping its lubrication system free of
water contamination. Source: Deublin Co.
inner bearing from thermal stress; this protection is particularly
important for machines operating with higher steam pressures,
such as those used to produce brown-grade paper. When properly
sealed, the sleeves would also prevent water contamination of the
circulating oil.
As an insulating material, carbon steel is susceptible to
“steam cuts” — small pits on the surface of the material, as shown
in Figure 2, that diminish seal integrity. Steam cuts are caused
by exposure to high-pressure, high-temperature steam over time.
Considering the age of the equipment and the composition of the
material, Deublin engineers correctly reasoned that the excess
water in the mill’s oil lubrication system was the result of leakage in
the steam joints.
Devising a solution
Although the mill had arrived at an intermediate fix —
removing excess water using dehydrators — it was not a sustainable
solution for the long term. The dehydrators were being rented at a
cost exceeding the value of the failing steam joints, the condition of
which would only grow worse over time.
Deublin engineers decided to integrate a new material into
the steam joints: stainless steel. Compared to carbon steel, which
had been used by the original equipment manufacturer (OEM) for
the composition of the steam joint insulating sleeves, the benefits of
stainless steel can be seen in the next column.

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