Problem Solved: Engineers take on challenge of failing equipment at paper mill - Paper Technology International 2023 - Paper Technology International 2023 - Flipbook - Page 71

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
Figure 2: Steam cuts are small pits caused
by exposure to high-pressure, hightemperature steam. Source: Deublin Co.
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stainless steel
Better insulation at the temperatures in dryer sections
Lower thermal conductivity (approximately 30% of
carbon steel conductivity)
Increased material hardness
Greater resistance to corrosion and steam cuts
It is not accurate to state that carbon steel should have
no place in the composition of steam joint journals. Compared to
stainless steel, the material’s lower coefficient of thermal expansion
is ideal for protecting equipment during transient conditions such as
startup, shutdown and changes in pressure.
This is where true engineering ingenuity came into play.
As shown in Figure 3, Deublin devised a custom solution that
incorporated the essential properties of both materials — one that
incorporated carbon steel to allow for thermal expansion, without
compromising the advantages offered by stainless steel. A carbon
steel journal flange was used to make contact with the dryer, while a
stainless-steel insert was positioned inside the flange. This brought
the differing thermal expansion rates of the two materials into sync,
producing the same level of thermal expansion between the flange
and journal.
Considering the potential impact of stainless-steel thermal
expansion on seal integrity, Deublin also positioned static sealing
elements in the external counter flange, around the diameter of the
stainless-steel sleeve. Each element was chosen for their resilience
to high temperatures. These included a Slyd-Ring, an Aflas O-ring
and a Teflon C-ring inside a stainless-steel insert applied by
interference in the adapting flange. A weep hole in the external
adapting flange was incorporated for leak detection
and identification in case of a static seal breach.
Building a system
Deublin’s approach looked beyond the immediate concern of
protecting the machine’s bearings, toward building a whole system
with long-term viability. Its custom-designed insulating sleeve is just
one element designed to reduce water contamination and extend
system life.
Another feature of the system design is an isolation tube that
allows for the passage of steam without contact with the mechanical
seal. The space between the inside diameter of the insulating sleeve
and the outside diameter of the isolation tube is filled with saturated
steam from inside the dryer. The seal surfaces are exposed only
to saturated steam and not dry superheated steam. Due to the
high level of water content, saturated steam serves as a thin film of
lubrication between the two rotating seals, extending seal life.
Figure 3: This innovative insulating sleeve employs elements of carbon
steel and stainless steel, along with static sealing elements. Source:
Deublin Co.
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