Page 68 - Industrial Plant 2015

Fig. 1 - Air Inlet The gas turbine Inlet filtration system therefore has two
System for a Siemens main missions:
SGT800 gas turbine • reliable operation;
(courtesy Camfil • engine efficiency.
Power Systems)
The costs of fouling far exceed the cost
of eliminating it but since capital costs
tend to be weighed heavy in equipment
purchase decisions many gas turbines
are equipped with inadequate inlet air
filtration and the operator ends
up paying many times more in extra
operating costs.
Reliability means that the inlet filtration system be able power output and an increase in heat rate for a given
must protect the gas turbine from penetration of
particles that could over time be a danger to the gas
turbine. These typically are particles that could cause
wear, or fine particles that could plug the holes in vanes A secondary effect of fouling is an increase in airfoil
and blades for cooling air and consequently cause
Fig. 2 - Particle size
and engine
degradation intervals
Industrial Plants - May 2015
66
damages due to overheating. In addition the inlet
system has to prevent the entrance of humidity and salt
which could cause corrosion and in combination with
sulphur in the fuel and high temperature, hot gas
corrosion in the power turbine.
Engine efficiency assurance means that the Inlet
filtration system efficiently must remove the entrance of
small particles in order to avoid compressor fouling
resulting in degradation of the gas turbine performance.
A gas turbines sensitiveness to fouling is normally
increasing with its efficiency. Axial compressor fouling is
primarily caused by airborne particles below one micron
in size (figure 2). Fouling changes the shape of both
rotating and stationary vanes and results in a reduction
of both mass flow and pressure ratio generated by the
compressor. The net result of fouling is a reduction of
combustor outlet temperature – conversely if an engine
is not running at its temperature limit a fouled engine
has to run hotter to produce a given output.
temperatures in the high pressure turbine as fouling in
the internal vane and blade cooling passages reduces
heat transfer effectiveness and ultimately reduces the
life of the hot section. The costs of fouling far exceed
the cost of eliminating it but since capital costs tend to
be weighed heavy in equipment purchase decisions
many gas turbines are equipped with inadequate inlet
air filtration and the operator ends up paying many
times more in extra operating costs.
The major cost consists of the actual and potential loss
of revenue. The filter maintenance costs, often looked
upon as high, is in reality marginal compared to mayor
ones such as:
• poor efficiency gives rapid engines degradation
resulting in loss of production and/or higher fuel