Hydrocarbon Processing - July 2022 - 77

Maintenance
and Reliability
I. WADE, Belzona Polymetrics Ltd.,
Harrogate, UK
Developing and utilizing a novel, toughened
epoxy adhesive
When identifying solutions that can offer assurance and longevity,
the maintenance and reliability of asset repairs can be
challenging. This article will examine the use of structural adhesives
as the first-choice solution.
Since structural adhesives provide high modulus and high
strength, they can be used for affixing metal substrates or components.
Even though adhesives are used in a wide range of industries
(including aerospace, rail and construction), they are not
presently recognized internationally like traditional methods.
Traditional practices-such as welding, riveting, nuts and
bolts, and mechanical fixing-are perceived as the go-to methods.
However, they all have their inherent inadequacies. Welding,
for instance, can be hazardous to health. Riveting, nuts, bolts
and fasteners can concentrate stress.
This article introduces a novel, two-component, solvent-free
toughened epoxy adhesive material that provides high adhesion
to metallic substrates, while also being able to withstand high
movement or cyclic fatigue vs. general epoxy materials.
In addition to potential application areas, this article also
discusses several benefits of this adhesive material, including its
ease of use, and its load bearing and impact-resistance properties.
Maintenance and repair
procedures. Most industrial
maintenance or repair procedures can involve either welding or
the use of mechanical fasteners, as these methods can be perceived
as easy and quick fixes; however, while these procedures
might initially seem to correct the issue, they may cause more
harm than good. Depending on the repair situation, welding or
drilling to connect mechanical fasteners on a storage tank containing
flammable liquid is not recommended for obvious reasons.
This is where a structural adhesive can offer a solution for
that type of maintenance repair.
There are many structural fixings used across a range of industries
that may be part of any maintenance or repair, including
support brackets (e.g., cable trays, antennas, heating coils,
filter pans) or any other internal fixtures in vessels that suffer
from corrosion, impacts or vibration damage.
Process equipment or piping can suffer from steel thinning
or even from wall defects, which will require either monitoring
or repairing depending on the severity of the integrity lost.
Structural fittings are generally used for fixing static members,
but they may be subjected to forces unbeknown at the time of
installation, including thermal cycling of the joints, cyclic loading
or vibration due to the fatigue of a component. If repairs
are needed, the contractor may be in a situation where a choice
of solutions can be made. If so, before a decision is made on a
course of action, the strengths and weaknesses of the possible
solutions should be identified.
Welding is regularly used for repairs since it is widely available.
Although welding is well regulated and results in a high-strength
repair, it does come with inherent risks (including heat stress and
other types of harm to the user), as welding can cause both acute
and chronic health risks.1
The application of welding repairs onto
piping sections, storage tanks, or process systems and equipment
should not be undertaken due to the high temperatures involved
and the combustible nature of the process fluids or gases running
through these systems or being stored in these components.
Bolted joints are a simple and low-cost repair because of
their ease of disassembly/reassembly. However, bolted joints
often use dissimilar metals, which contributes to galvanic corrosion,
adds weight to the joint, and requires routine inspection
and tensioning. Also, drilled holes in the support material create
uneven stress distributions.
Structural adhesives have a high bond strength and are lightweight.
In addition, adhesives that are applied to cover the entire
joint result in a uniform stress distribution, reducing metal
distortion under strain.
The importance of a strong bond. Adhesive bonding is the
joining of similar or dissimilar members together, while creating
permanent high-strength bonds that can transfer structural
stress without loss of structural integrity.
Regardless of the joint type used, it is important to understand
the different stresses that are imparted onto a bonded
assembly. Adhesives perform the best when the stress is twodimensional
to the adhesive, allowing the force to be applied
over the entire bond area.
Joints that are well designed for adhesives place most of the
stress into compression or shear modes. Adhesives perform the
worst when stress is one-dimensional to the adhesive, concentrating
the load onto the leading edge of the bond line. Joints that
are placing stress on peel or cleavage adhesion concentrate this
stress onto the leading edge, which may lead to premature bond
failures, especially if subjected to vibration, impact or fatigue.
Hydrocarbon Processing | JULY 2022 77
Hydrocarbon Processing - July 2022

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