operators face today is that the standard
efficiency rating of the filter will not
necessarily equate to the performance
of the installed system. Recent comparative studies carried out by a major
gas turbine OEM on the performance
of equivalent ePTFE membrane and
microfiber glass HEPA filter products
covered overall efficiency, pressure loss,
hydrophobic performance, wet performance and the dust holding capacity of
each technology. The tests showed the
microfiber glass filters to produce equal
or better performance than the ePTFE
equivalents, and at a lower cost.
This article is not trying to say microfiber glass media is better than ePTFE.
CLARCOR manufactures ePTFE membranes which are successfully installed
in many other filtration applications
and future developments may well deliver improved resilience to moisture
and hydrocarbons of this media type.
As the technology stands today, however, the unpredictable response eP TFE
membranes have to the wide-ranging
air contaminants found at gas turbine
installations means CLARCOR does not
recommend them for use on turbine installations.
Filter test standards and materials for
use in gas turbine filtration solutions
continue to develop as we learn more
about environmental impacts. What
is clear is that operators need to take
a wider view of filter and turbine performance rather than considering only
standard efficiency ratings.
Both microfiber glass and ePTFE
membranes can provide HEPA filtration
levels. While ePTFE membranes can
deliver a typical lifespan of two years,
however, this is still much shorter than
microfiber glass equivalents for power
plant gas turbine installations. Where
moisture levels are high or there is like-
lihood of fog or mist weather events,
the thicker microfiber glass media will
give a more predictable response. ePT-
FE solutions will require close moni-
toring and quick change out to protect
machinery if they suddenly become
As technology and understanding
develops, it is recommended that power plant operators consult filter manufacturers to understand the options
available to them. By working with
filter suppliers that appreciate and understand the varying needs of different
environments, a turbine can be better
protected and this may not be the most
expensive option. By eliminating unnecessary maintenance or shutdowns
and improving turbine performance,
the right solution can give a very quick
return on investment.
Microglass vs. Membrane 2
HEPA filters are typically constructed from two media choices – PTFE membrane or microglass.
The thickness of the media can play a large role in filter operating performance.