Paper mill maintenance painting: Safe work practices, state-of-the-art coatings solve application problems, Solutions!, Online Exclusives, November 2002
MILL MAINTENANCE PAINTING:
SAFE WORK PRACTICES, STATE-OF-THE ART
COATINGS SOLVE APPLICATION PROBLEMS
Dave Schutz, The Sherwin-Williams Company
Productivity and safety
rank as top priorities for pulp and paper mill managers. But how do these
priorities apply when it comes to plant maintenance painting projects?
Georgia-Pacific Corp. is a leading manufacturer of tissue, towel and other
paper products for both the home and away-from-home markets. The Old Town
paper mill, a former Fort James Corp. facility in Orono, Maine, just north
of Bangor, has an exemplary maintenance painting program that is part
of the mill’s overall corrosion control program.
Two recent projects at the mill—the refurbishment of a chemical tank
and the repainting of a steel and concrete ceiling deck above a kraft
paper machine—demonstrate the effective use of teamwork, innovative
safety techniques and advanced coatings technologies to put safety concerns
to rest, minimize productivity disruptions and maximize equipment service
The chemical tank, a caustic soda storage tank located in the bleach plant
building, is used to feed the papermaking process. The tank’s carbon steel
exterior showed significant rusting. The tank is surrounded by nearby
operating equipment, walkways and structural support steel. This posed
a challenge for on-site painting contractor Corrosion Control Inc., along
with mill maintenance and engineering personnel, to develop a painting
plan that would minimize any unwanted effect on the nearby equipment.
The painting contractor’s three-year maintenance contract at the site
runs concurrently with a three-year supplier contract from The Sherwin-Williams
Company. Corrosion Control, based in Smithfield, Maine, employs only 15
or 20 full-time painters, yet the company keeps a full-time safety director
on staff and has an outstanding safety record. Ted Ocana, a site engineer
employed by the Old Town mill, oversees the purchase of coating materials
with input from the painting contractor.
The group determined that a portable "spider staging" that would
move up and down the sides of the tank to conduct surface preparation
and coating application would help ensure safety and eliminate the potential
for damage to nearby structures. "The fact of the matter is that
safety today is so much more than making sure you have a belt on,"
said Jim Marston of Corrosion Control. "It’s a science."
All old coating and rust were removed from the tank’s exterior using a
combination of different techniques. Power tool cleaning to bare metal
(SSPC-SP-11) was accomplished over most of the accessible surfaces. This
was supplemented with abrasive blast cleaning using baking soda, which
effectively cleaned and removed any of the old coating and remaining rust.
Baking soda is also environmentally friendly and can be easily washed
off any nearby equipment with water.
The mill chose a three-coat moisture-cure urethane system to allow fast
recoatability and quick curing. The primer, COROTHANE® I Zinc, was
spray applied to achieve 3 to 4 mils dry film thickness (DFT). The intermediate
coat, COROTHANE® I Mastic, was applied to achieve 2 to 3 mils DFT.
Finally, the topcoat, COROTHANE® I Aliphatic, matched to the mill’s
beige color, was applied at 2 to 3 mils DFT.
Corrosion Control finished applying three coatings within three days.
There was minimal disruption in the operational area and the tank received
a sound corrosion protection system. The equipment surrounding the area
also went unharmed.
Despite working in gritty, industrial environments, Corrosion Control
pays attention to the appearance of its projects. "Sometimes you’ll
encounter the attitude that since this is industrial paint, you just have
to throw it on," said Marston. "That doesn’t work with us. I’m
very fussy. It has to look good."
That can be a challenge in paper mills, where concrete ceilings and steel
infrastructure, processing units and machines function in hot, humid environments.
Temperatures at the ceiling during "on-the-run" painting operations
can eclipse 130°F and the relative humidity is constantly at or near
100 percent. These conditions create unique challenges in specifying coatings
for long-term performance, and for coatings application.
Ocana has a clear understanding of the Old Town mill’s coating needs and
is capable of writing specifications for virtually any coatings job in
the plant, Marston said. That helps, he added, because "at some places,
the customer just says, ’Go paint it.’ That can be tough because you’re
the scapegoat if something goes wrong. Some will tell you to paint right
over grease, but you’ve got to remember that your name is going to be
on the job when it’s done."
Marston and Ocana were supported by Jim Bouier, the Sherwin-Williams Industrial
and Marine Coatings representative. High-performance coatings—such
as the Sherwin-Williams COROTHANE® family of moisture-cure urethanes-are
designed with high-humidity applications in mind. Marston is also pleased
with the results he’s experienced with Sherwin-Williams DURA-PLATE®
235 Epoxy Coating.
"For mill work, we look for a coating that can tolerate minimal surface
preparation and still perform," said Marston, who calls for surface
preparation of SP-11 for most steel finishing tasks in the mill. However,
surface prep remains the most important aspect of any job in the mill.
"Without it, product won’t mean a thing," Marston said.
breath of fresh air
Both surface preparation and product were critical when the mill gave
Corrosion Control the task of developing a plan to clean and repaint the
concrete decking and structural steel above kraft paper machine #1—while
the paper machine continued to operate. "Downtime on these machines
is US$ 50,000 an hour. At the mill, they’ve got to be comfortable that
we can not only work safely, but do so without dropping anything onto
Close inspection of the ceiling showed some spalling of the concrete deck
panels. The steel support members showed considerable rust but no significant
loss of thickness. No wholesale replacement of steel or concrete was considered
necessary, but some concrete panels required cement patching done before
a moisture-proof barrier coating could be applied.
Essential to the project was the construction of a work platform to allow
repainting of the ceiling without disrupting the paper machine’s production.
The platform was designed with flexible air ducts feeding into it to pump
and continually circulate cool air through the work area. Without the
much-needed relief offered by the cooler air, painters would have had
to work in the 130°F temperatures generated by the paper machine.
The platform also had to prove "air tight," keeping any debris
generated from the surface preparation process away from the machine.
Abrasive blasting was ruled out as a preparation method on the steel due
to the proximity of the paper machine. Instead, worked used hand tool
and power tool cleaning (SSPC-SP-2 and 3). They patched the concrete to
cover any exposed rebar.
The addition of the air ducts considerably improved the working environment
and application of the coatings. The painters were able to work for extended
periods of time, avoiding any potential for dehydration or heat exhaustion.
Painters first brushed and rolled the Sherwin-Williams primer, MACROPOXY®
920 Pre-Prime, onto the steel to achieve the recommended 1 to 2 mils DFT.
This low viscosity, epoxy primer is designed to penetrate into any remaining
rust. The resultant surface is ready to receive a high performance topcoat.
The topcoat, DURA-PLATE® 235, is a two-part high build epoxy designed
to withstand the heat and high humidity that comes off the paper machine.
DURA-PLATE 235 was applied at 6 to 8 mils DFT. After the concrete patching
operation, workers applied an acrylic elastomeric coating. This provided
a moisture barrier against the high humidity given off of the paper machine.
The addition of air ducts and the work platform allowed painters to work
through the extreme temperatures and humidity to successfully complete
the ceiling project. The work platform also allowed the paper machine
to continue operation without interruption. The specification and application
of state-of-the-art coatings accommodated limits on surface preparation
without compromising coating performance. By working with its supplier
and contractor, the Old Town mill was able achieve a highly effective
pulp and paper mill maintenance painting program.
the author: Dave Schutz is product information specialist, The Sherwin-Williams
Company, Industrial and Marine Coatings.