MAINTENANCE SEPTEMBER 2019
SIGNED,
SEALED, DELIVERED
Many companies remain unaware of the potential for signifi cant energy
waste that may be embedded in their operational equipment and processes
BY TOM GROVE, CEO, AESSEAL
Mechanical seals are a vital, but
relatively small, pump component
and the power they consume due to
friction accounts for a tiny percentage
of the total power consumption. It’s
therefore easy to see how they can be
overlooked by managers seeking to target energy
losses and improve effi ciency.
However, if you don’t look at the seal in
isolation, while at the same time examine the
support system which ensures it operates to
maximum effi ciency, the potential for much
higher energy consumption, and hidden cost,
can be readily identifi ed.
With the exception of gas-injecting seals, a
large proportion of mechanical seals are set up
with a clean fl ush liquid to provide lubrication,
prevent overheating and maximise reliability.
This fl ush liquid is provided from a separate
seal support system, or ‘piping plan’, which
improves the operating environment to provide
reliable operation and longer seal life. It is the
energy consumed indirectly by the piping plan
that is often overlooked, and the amount that can
be saved is often considerable.
There are two key types of piping plan:
Flush: clean, cool liquid is injected into the seal
chamber to improve the operating environment.
Barrier or buff er: a secondary fl uid is fed to
the space between two co-axial mechanical seals
to prevent atmospheric contact with the pumped
fl uid, improve seal cooling, or enhance safety.
With hot processes, cool
liquid from a fl ush system
is injected into the process
stream, removing heat which
must in turn be reheated to
compensate. Some piping plan
confi gurations remove part
of the process fl uid and cool
it in a heat exchanger before
reintroducing it to the process
stream, which again requires
a process of reheating. Where
cool liquid has been added to
the process, evaporation may
also be used.
When combined, all these
processes can lead to increased
energy use; therefore the
judicious selection of piping
plans is of great relevance
to any company looking to
contribute to environmental
sustainability.
Identifying where signifi cant
amounts of energy are being
wasted can be as simple and lowcost
as carrying out a periodic
seal energy audit. This will
identify energy improvement
opportunities that can be
achieved by using alternative
fl ush liquid piping plans.
Seal energy audits
A seal energy audit involves
the inspection of each piece of
equipment, recording various
metrics and parameters.
Heat fl ow calculations are
performed, making it possible
to calculate the amount
of energy impact of each
individual mechanical seal on
the plant. Energy costs are
calculated on the frictional
energy consumed by the seal
or packing, plus the pump heat
soak, and the energy consumed
in additional downstream
processes to remove fl ush-toprocess
dilution and/or restore
process temperature. Where
high energy use is identifi ed, it
can be reviewed to identify a
potentially more effi cient seal
support confi guration. A typical
seal energy audit summary
will provide the company
with a review of potential
opportunities, the investment
required to upgrade and the
potential returns.
It off ers a ‘quick-win’
overview, highlighting lowhanging
opportunities which,
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