Hydrocarbon Processing - October 2022 - 57

Maintenance
and Reliability
O. OHARRIZ, Belzona Inc.,
Miami Lakes, Florida, U.S.
Development of novel epoxy closed-cell foam
for personnel and corrosion protection-Part 1
Most industrial assets operating at
elevated temperatures require thermal
insulation for energy conservation, thermal
protection or process stabilization.
As soon as the insulation is installed and
in service, the risk of the underlying substrate
of suffering from corrosion under
insulation (CUI) increases. It should be
noted that CUI represents a severe threat
to the onstream reliability of many of
today's refining, chemical, power generation,
and pulp and paper industries,
including onshore and offshore installations.
The mechanism of CUI is initiated
by the ingress of water into the thermal
insulation, which traps the solution at
the annular space between the metal substrate
and the insulation. As a result, the
substrate starts corroding under the insulation.
Elevated temperatures exacerbate
this corrosion mechanism.
NACE SP0198 defines carbon steel,
austenitic and duplex stainless steels as
the primary metallic substrates potenTABLE
1. Foaming perspectives
Perspective
Types
Material
Mechanism
Nature
Structure
Cell Size
Density
Thermoplastic/Thermoset
Physical/Chemical
Flexible/Rigid
Closed-cell/Open-cell
Microcellular/Cellular
High-density/Low-density
tially suffering from CUI. In practice,
CUI commonly appears in thermal ranges
between 50°F and 350°F, or where
there is cyclic operation of the equipment.
For carbon steels, CUI manifests
in the form of uniform and localized corrosion.
For austenitic and duplex stainless
steels, CUI is normally localized,
leading to stress corrosion cracking if appropriate
environmental conditions and
stress levels are met.1
Additionally, thermal insulation can
prevent operators and personnel in
general from experiencing skin burns
after accidentally touching substrates at
moderately elevated temperatures. As
technology has expanded, the processes
and associated equipment and pipework
have become more complex and convoluted,
creating more situations where
workers are exposed during their shifts.
Subsequently, worker organizations and
governmental agencies have demanded
the increased use of insulation for perComments
A
wide variety of thermoplastics, such as polypropylene, polyethylene, polystyrene, polycarbonate
and polyvinyl chloride, have been used in foam processing techniques. Epoxy is an example of a
thermosetting insulating material.
Physical (or soluble) mechanism involves physical action (e.g., blowing a gas into a polymeric
matrix). Chemical action is when the foaming mechanism solely depends on a chemical reaction
(e.g., the reaction of an isocyanate with water).
Flexible foams tend to be less cross-linked than rigid foams.
Closed-cell refers to a foam that minimizes permeability by entirely isolating the substrate,
whereas open cells are higher in permeability.
Microcellular cell sizes are reported in the order of 10 μm.4
The density of foams varies, in general. Lower densities are achieved when the polymer holds
higher proportions of air.
Hydrocarbon Processing | OCTOBER 2022 57
sonnel protection, mostly for metallic
equipment at ≥ 140°F. No mandates or
statutes govern the upper limit temperature
for personnel protection.
To correct potential CUI problems
and provide effective thermal insulation,
asset owners are urged to implement
comprehensive corrosion and insulation
protection strategies. As a rule, any
such strategies should comprise at least
three components: coating, insulation
and jacketing. High-quality corrosion
resistance coating is applied to the substrate
and, if it is properly applied, should
perform as a water barrier isolating the
substrate from the trapped water. Conversely,
the insulating material should be
protected with an effective and durable
weather barrier or jacketing.
However, today's high energy prices-
and, at times, maintenance budget reductions-render
these solutions costly and
laborious. This is the reason why asset
owners and process engineers are con

Hydrocarbon Processing - October 2022

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