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Benchmarking performance
The owners of this Atlantic coast LNG project approached
Camfil Group for a solution that would ideally enable
the plant to run continuously for five years without any
unexpected shutdowns for filter replacement or offline
washing.
The company recommended a three-stage filtration
solution with an M6 filter as a first stage, followed by a more
efficient F9 as a second stage and an extremely efficient E12
final filter stage. A fourth stage, featuring a G4 filter for safety
purposes, is also included. This enables the final E12 filter to
be replaced without shutting down the machines and
prevents the turbine from ingesting tools, for instance, in the
event of an accident.
The G4 will never be changed, as it is only there in case of
the need for an urgent change on the E12, and, since the new
air inlet filtration installation was commissioned
approximately three years ago, that has not been needed yet.
Indeed, by switching to a multi-stage system, the
availability of the engine is now almost at 100% because it
is also possible to replace the first two filtration stages with
the engine in operation. Furthermore, since the retrofit of
the three-stage solution, the operators have not been
required to shut down any of the trains for unscheduled
offline washing and, while the operators continue to
perform regular online washes as part of a maintenance
schedule, this is not required nearly so frequently. As a
result, the online washing interval has been changed from
two weeks to four weeks and the owners already plan to
increase the online wash interval to five weeks as they
move to find the optimum interval period, based on
operational experience.
Critically, the operators have not seen any degradation in
the compressor performance since they have been running
with the Camfil solution. Although the filtration medium
requirements are inevitably more costly than a basic
OEM-specified approach, the return on investment (ROI) for
that particular site was in the range of two years.
Periodic offline washing and inspection has revealed that,
to date, no offline washing was required as a result of fouling
of the turbine compressor stages.
Adopting a rigorous approach to air
inlet filtration
The clear cost benefit afforded by operational reliability
in an LNG compressor train application is helping to build
awareness of the importance of air inlet filtration among
the major oil and gas players. The majority of the world’s
oil giants, such as Shell, Total, and BP, are now specifying
more effective filtration solutions as a matter of course. This
is a trend that is likely to continue, reducing operating and
maintenance costs as a result of cleaner running machines
and reducing unscheduled outages.
In oil and gas applications, and LNG compressor stations
in particular, even small losses in efficiency due to engine
degradation or time offline for filter replacement are a
sensitive and costly issue.
For LNG applications, effective air inlet filtration can help
to ensure that all compressors are running all of the time. The
case for specifying appropriate filtration needs in such harsh
conditions, coupled with the cost performance effects of
misapplied systems, is a compelling one.
Figure 4.
The recommended upgrade was a static solution
with four stages: an M6 coalescing bag as the first stage, an F9
compact with vertical pleating for water drainage as the second
stage, a high efficiency E12 final filter, and a fourth stage G4 guard
filter that acts as a protector to ensure that the final E12 filter can
always be changed online.
