.jpg)
Specific
steam consumption is the amount of steam consumed by a Turbine to generate unit
power.
Or else, Specific steam consumption is the
ratio of steam entered into the Turbine to the power generated
SSC
= Steam consumption / Power generation.
For example: A 50 MW steam turbine consumes 190
TPH of steam to operate on full load, then its Specific steam consumption (SSC)
will be;
SSC = 190 /
50 = 3.8 TPH/MW or 3.8 kg/kwh
Specific steam consumption (SSC)
of a Turbine depends on following factors;
1-Inlet
steam parameters
2-Vacuum or
exhaust pressure
3-Exhaust
pressure
4-Bleed
steam pressure, temperature & flow
5-Extraction
steam pressure, temperature & flow
6-Turbine
maintenance practice or preventive and corrective maintenance
Specific
steam consumption (SSC) of a Turbine can be reduced by taking following
corrective measures.
Maintaining inlet steam parameters: Maintaining Turbine inlet steam
parameters play a vital role in improving Specific steam consumption (SSC). The
steam pressure and temperatures lower than the design will lead to increase Specific
steam consumption (SSC).
Therefore, always maintain Turbine inlet main
steam temperature as per OEM recommended to reduce steam consumption.
Maintaining
higher vacuum & lower exhaust temperature: Turbines operating at lower vacuum (exhaust
pressure) and higher exhaust temperature call for more steam consumption to
generate unit power as compared to Turbines operating at higher vacuum &
lower exhaust temperatures.
So, it’s always recommended to maintain vacuum
on higher side.
Ensure following to get
more vacuum.
1-Sufficient cooling water for condenser
2-Condenser Tubes are being cleaned regularly
3-Enough temperature drop in cooling tower
4-Operation of the Turbine at optimum load. Operation
of the Turbine at lower loads results into higher exhaust temperature.
5-Ejectors steam pressure & temperature are
as per OEM
6-Use of Liquid ring vacuum pump (LRVP) saves steam energy & consumes around 40% of its power in terms of electrical power.
Bleed
steam pressure, temperature & flow: Higher the bleed steam pressure, temperature & flow
than design higher will be the Specific steam consumption (SSC) or lower will
be the power generation at same quantity of inlet steam flow.
Hence, always try to maintain bleed steam
pressure & temperature within limit.
Read>>>>Calculated reasons for more SSC
Higher bleed steam pressure & temperature
carries away the heat from Turbine without doing any work in Turbine, hence
steam consumption to generate specific power will increase.
Extraction
steam pressure & Temperature: Similarly, steam extraction at higher steam pressure & temperature
will lead into more steam consumption.
Wear out
of labyrinth seals: If there is
more clearance between internal seals & rotor, some amount of steam directly
escapes into next stages of rotor without contributing work done. Hence in such
case, Turbine draws more steam to generate desired power.
Therefore, always carryout the Turbine
preventive maintenance regularly and replace worn out parts especially seals
& gaskets
Steam
leakages: Arresting all
internal & external steam leakages.
Operation
of the Turbine at optimized load: Operating the Turbine at lower loads will lead to more steam consumption
to generate particular unit of power.
Hence always try to avoid the operation of the
Turbine at partial loads.
Proactive
operation & maintenance practice: Following operation & maintenance practices
should be followed to reduce Specific steam consumption (SSC) of a Turbine.
Timely replacement of worn out bearings, ensuring
precision alignments
Read more on>>>>Turbine major overhauling
Maintaining correct temperature of lube oil for
bearings
Regularly servicing of actuators to avoid load
hunting
Maintaining good quality for steam and water
Ensuring turbine blades cleaning during every
major overhauling
Monitor the load & steam consumption on
various loads & observe any deviations
Read more>>>>>Interview questions & answers on steam Turbine
