Hydrocarbon Processing - November 2022 - 47

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 2
Most industrial assets operating at eleEXPERIMENTAL
PROCEDURE
vated 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 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 generating, 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 potentially
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
Part 1 of this article (October 2022)
detailed the development of a novel epoxy
closed-cell foam insulating and corrosion
protection barrier by a coating
manufacturer. Design considerations of
such a material, fitness-for-service testing
and results were also presented. Potential
application areas and benefits, including
worksite personnel and CUI protection,
were discussed.
Thermal conductivity (EN 12667/
ASME C177). Thermal conductivity is
used to measure the ability of a material
to conduct heat when in thermal contact
with another surface. Two samples of the
proprietary epoxy foama
were cast and allowed
to grow at ambient temperature, as
shown in FIG. 4. The samples were sandwiched
between a central heating slab
(hot plate) and two peripheral flat cooling
slabs (cold plates) in a guarded box,
as depicted in FIG. 5.
Heat was generated and the temperatures
of the sample surface adjacent to
both the hot and cold slabs were measured
and averaged. The thermal conductivity
of the epoxy foam was then
calculated based on one-dimension heat
transfer equations at sample mean temperatures
of -40°F, -4°F, 32°F, 68°F,
140°F, 248°F and 302°F.
CUI protection (modified ISO 19277).
The objective of this test was to subject
the epoxy foama
to simulated scenarios
of multi-phase cyclic CUI and assess its
performance based on the possible development
of rusting, cracks and/or delamination
after exposure. A pipe section
constructed of mild carbon steel and of
known dimensions was prepared using
two different surface cleanliness methods:
abrasive blasting to the requirements
of SSPC SP 10 and power tool cleaning
according to SSPC SP 11. The average
FIG. 4. Cast sample of the proprietary
epoxy foama
.
FIG. 5. Schematics of the guarded-hot-plate
experimental apparatus.
FIG. 6. Specimen for simulated corrosion under insulation testing.
Hydrocarbon Processing | NOVEMBER 2022 47
Hydrocarbon Processing - November 2022

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