POWER March 2014 - 57

OPERATIONS & MAINTENANCE
2. Apply. Applying Belzona 1341 (Supermetalglide) to a runner reduces surface friction, resulting
in higher operating efficiency in fluid flow equipment, such as turbines and pumps. On the
bottom of this turbine, the paste grade material used to infill areas of erosion damage is visible
before application of the coating. Courtesy: Belzona Polymerics Ltd.
5. Increased efficiency. These performance
curve results were recorded by the UK
National Engineering Laboratory. Courtesy:
Belzona Polymerics Ltd.
Coated
Uncoated
30
25
90
80
70
60
500
Flow (m3/hr)
epoxy technology, these products are safe to
use, even in enclosed spaces.
Specialized filler materials, such as ceramics
and aluminium oxide, allow epoxy coatings
to achieve good wear resistance. Epoxy
coatings combine with the metallic substrate
to provide a composite component, which offers
ongoing maintenance advantages.
gradually, heating up the entire part first prior
to application of the repair technique, and
lengthy cooldown times are required after
application of the repair to avoid excessive
heat distortion. Care is also required when
selecting the repair metal (plates or welding
rods), as different materials can introduce local
galvanic corrosion, initiating even more
repair requirements.
A Better Alternative: Coatings
Modern polymeric repair systems offer an
excellent alternative to traditional repair
materials. These materials are supplied in
either paste grade filler type repair composites
used to infill damaged areas and restore
profiles (Figure 1) or as coating grade products
used to provide long-term protection
to equipment against specific damage. Ad3.
Ready to run. After coating application,
this runner is installed and ready to return to
service. Courtesy: Belzona Polymerics Ltd.
Belzona polymeric efficiency coating (Ra 0.078 um)
vanced polymeric coatings completely halt
corrosion by isolating the metals and closing
the corrosion cell.
Polymeric coatings have been used for
more than 60 years in many different applications,
such as on hydroelectric generation
equipment, offshore and onshore oil and gas
systems, pumps, and sewage treatment equipment,
and they have a reliable track record in
these environments. By utilizing solvent-free
4. No comparison. A Leeds University
surface inspection study found that polished
stainless steel was far less smooth than Belzona
1341 (Supermetalglide). Courtesy: Belzona
Polymerics Ltd.
Polished stainless steel (Ra 1.19 um)
Application Advantages
Prior to application, thorough surface preparation
is required in the area to be repaired.
This is commonly achieved using localized
grit blasting to clean and roughen the metal,
which allows the polymer to form an intimate
bond with the base metal.
Polymeric repair and coating composites,
such as Belzona, are supplied as two-part
products. The components are mixed prior
to application using spatulas and bowls
or with paddle mixers for larger projects.
This mixing initiates the chemical reaction,
which enables the product to solidify to its
final form.
Application is commonly carried out using
trowels for paste grade rebuilding composites
and by brush for coating grade epoxies (Figures
2 and 3). Many products can also be applied
by airless spray, allowing for rapid repair
times over large areas. The product is then allowed
to cure for a period of time before the
equipment can be returned to service.
Because modern epoxy polymer materials
are cold-curing, they eliminate the requirement
for hot work that is needed for
traditional repair techniques. This avoids
problems, such as:
■ Risk of equipment distortion.
■ Requirement for specialist rigging and jigs.
■ Lengthy repair times required to allow for
cooling of welds.
■ Grinding and finishing of weld overlay.
March 2014 | POWER
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55
1000
Efficiency (%)
Head (m)

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POWER March 2014

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