pwr_september-2024 - 14

O&M
Fasteners and Gaskets for
Power Plant Service
Anyone who works in the power industry
knows how important fasteners, such
as nuts, bolts, and rivets, and gaskets
are to plant operation. Fasteners provide
structural integrity, effectively holding everything
together. You couldn't operate a
turbine or generator, or maintain piping
systems and pressure vessels, without
them. Gaskets, meanwhile, create the
seal between mating surfaces, such as
flanges (Figure 1), covers, and joints.
These seals are essential for containing
and preventing the leakage of fluids, such
as steam, water, and oil, or gases within
the power plant. Proper sealing helps to
maintain system pressures, prevent environmental
contamination, and ensure the
efficient operation of the plant.
Choosing the Right Fasteners and
Gaskets for a Job
The type of power plant, such as nuclear,
coal, natural gas, or renewables, can affect
gasket and fastener requirements.
" Some of the older, traditional models,
such as coal, use standard and commodity
gaskets and fasteners, whereas,
in comparison to nuclear, there's more
regulation and specifications that are associated
with the purchase of gaskets
and fasteners to ensure a high-quality
product, " said Justinn General, engineering
manager with Lamons, one of the
largest privately held gasket, seal, bolt,
and hose assembly manufacturers in the
world. General said many renewable energy
power facilities are also dependent
on standard and commodity gaskets and
fasteners, but some are beginning to
move toward better alternatives.
There are many factors to consider
when selecting gaskets and fasteners
for power plant applications. Some of the
most critical parameters include temperature,
pressure, and medium, that is,
what's inside the pipes. The bolt and joint
connection, and how they interact with
each other, are also important. General
said when gaskets require a very tight
seal, then high-strength fasteners are
necessary. Engineers must also consider
whether the application is going to be
pressure cycling or thermal cycling. Furthermore,
if the media is corrosive, alloy
selection and gasket selection become
more important.
Power plants often experience significant
vibrations and thermal fluctuations
due to the high-speed rotation of
turbines, the combustion of fuels, and
the transfer of heat. Fasteners and gaskets
help to absorb and distribute these
stresses, helping prevent damage and
failure of critical components. This helps
to extend the lifespan of the equipment
and maintain reliable power generation.
Often, there is a tradeoff between
cost and performance, and the decision
on what gaskets and fasteners are used
is a compromise. " You have to really understand
the criticality of the application
and the importance of it not failing, " said
General. " When it comes to these highperformance
and cannot-fail systems,
it usually merits equipment and highperforming
gaskets that would give that
guarantee of not failing. "
Failure Modes and Solutions
Yet, even when critical factors have been
considered and the best materials chosen,
gaskets and fasteners can still fail
over time. It's not uncommon for bolted
connections to begin leaking a few years
after installation. General offered some
tips, however, to minimize failure rates.
" Workers must understand the impor1.
Bolted flanges are held together with
fasteners and kept leak-free with high-quality
gaskets. Courtesy: StockSnap / Tim Sullivan
14
tance of proper lubrication of the studs
to ensure a consistent k-factor, " he said.
K-factor, also known as the nut factor or
www.powermag.com
torque coefficient, is a dimensionless
number that represents the ratio of input
torque to the resulting clamp force
in a bolted joint. It helps engineers and
technicians determine how much torque
should be applied to achieve the desired
clamping force in a bolted connection.
Factors affecting k-factor include things
like friction between the bolt threads
and nut threads, friction between the
nut face and the joint surface, geometry
of the threads, material properties of the
fasteners and joint, surface finish and
coatings, and lubrication.
" It's also important to use proper instruments
and tools that give you the
highest accuracy of torque being applied
through
bolt-up, "
continued
General.
Meanwhile, having proper bolt-up procedures
and training workers appropriately
should not be overlooked.
When systems are exposed to cycling
at high temperatures, it may be worthwhile
to use high-recovery gaskets.
These are gaskets with the ability to " recover "
or return to their original shape
more readily than other types after being
compressed or exposed to thermal
cycling. Lastly, if a plant finds there is a
constant problem with leakage from a
specific joint or application, that could
mean a thorough engineering evaluation
is warranted. In such a situation, a better
alternative to the existing gasket material
could exist and may be worth trying.
Among innovative gasket designs
General mentioned was Lamons' CorruKamm
gasket. It utilizes " Kammprofile
technology " with a heavy substrate
capable of extreme load-bearing properties,
combined with a precisely located
corrugated pattern that greatly enhances
deflection and compression under load.
This makes the gasket more forgiving
when perfect alignment and parallelism
do not exist.
Concerning fasteners, General pointed
to load-indicating studs as a significant
improvement. He also said performance
coatings for fasteners, such as NanoGalv,
improve corrosion resistance and
thermal degradation, leading to improved
outcomes. NanoGalv, made by Modumetal,
is a proprietary zinc-nickel coating
that the company says " offers superior
performance, competitively and with
substantial sustainability benefits. " ■
-Aaron Larson is POWER's
executive editor.
POWER | September 2024
http://www.powermag.com
pwr_september-2024

Table of Contents for the Digital Edition of pwr_september-2024
