Bab 8 - Turbine

7/28/2019 Bab 8 - Turbine

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Berbagi dan Menyebarkan Ilmu Pengetahuan Serta Nilai-Nilai Perusahaan 1

PT. PLN (PERSERO)

PUSAT PENDIDIKAN DAN PELATIHAN TURBINE

TURBINE

8.1 Background

Steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and

converts to useful mechanical work. The steam turbines are split into three separate stages,

High Pressure (HP), Intermediate Pressure (IP) and Low Pressure (LP) stage. After the steam

has passed through the HP stage, it is returned to the boiler to be re-heated to its original

temperature although the pressure remains greatly reduced. The reheated steam then passesthrough the IP stage and finally to the LP stage of the turbine.

Figure 8-1. View of the Internals of a Typical Power Station Steam Turbine

Steam turbines are generally configured in many different ways. Several IP or LP stages can be

incorporated in to the one steam turbine. A single shaft or several shafts coupled together may


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be used. Either way, the principles are the same for all steam turbines. The configuration is

decided by the use to which the steam turbine is put, co-generation or pure electricity

production.

Turbines are one of the major components of any thermal power plant, generate steam for

power generation. The brief details of typical boiler used in 210 MW thermal power plant is

given in the Table 8-1.

Table 8-1: Brief specifications of turbine


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8.2 Steps Involved In Conducting the Energy Audit

The steps involved in conducting energy audit of turbines are:

Data collection

Observations and Analysis

Exploration for energy conservation measures

Report preparation

8.3 Data Collection

The following data sheets give brief specifications to be collected. It is suggested to obtain the

comprehensive technical specifications of Turbines and its associated equipment.

8.3.1 Specification of turbine and associated equipment

a. Turbine

Collect the detailed design specifications of the turbine. The following Table 8-2 gives the list

of specifications to be collected for energy audit study in addition to following specific

details.

Type of the turbine

Make and model

No of stages (for HP, IP and LP)

Number of cylinders

No of main and reheat valves

Construction details of HP, IP LP

Turbine extraction systems

Control systems Type of governing

Type of sealing

Year of installation

Major modifications carried out during the recent past

The design specifications to be collected are given in the following Table 8-2


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Table 8-2: Design Specifications of turbine

Particulars Unit MCR NCR

Rated output MW

Turbine Heat rate Kcal/kWh

Efficiency of the turbine %

Steam flow for rated output tph

HP inlet steam pressure Kg/cm2

HP inlet steam temperature OC

HP exhaust steam pressure Kg/cm

2

HP exhaust steam temperature OC

IP inlet steam pressure Kg/cm2

IP inlet steam temperature OC

IP exhaust steam pressure Kg/cm2

IP exhaust steam temperature OC

LP inlet steam pressure Kg/cm2

LP inlet steam temperature OC

LP exhaust steam pressure Kg/cm2

LP exhaust steam temperature OC

Condenser vacuum mmWC

Cooling water inlet temperature to condenser OC

Cooling water outlet temperature to condenser OC

Cooling water flow through the condenser m3/h

Super heater spray tph

Reheater spray tph

8.4 Instruments Required

The following instruments are required for conducting turbine energy audit:

Temperature Indicator & Probe

Pressure gauges

Flow measuring instrument (steam and water)

Ultrasonic leak detector


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While conducting the turbine efficiency test, measurements of steam flow pressure and

temperatures are very essential. Calibrated on line instruments can also be used for conducting

the test

8.5 Measurements & Observation Be Made

While conducting the audit, the following measurements (temperature and pressure) are

necessary

Feed water at Inlet & Outlet of Heaters

Main steam

HP turbine extraction Hot reheat steam, Cold reheat Steam

IP extraction

IP Exhaust

In addition to the above, the following measurements are required:

Condenser back pressure

Cooling water flow and temperatures

Generator output

Barometric pressure

Reheater spray (flow)

Superheater spray (flow)

Feed water (flow)

8.6 Observations and Analysis

8.6.1 System familiarization and operational details

Detailed interactions with the plant personnel have to be carried out to get familiarization for

system detail and operational details. The brief details of the entire system have to be given in

the report along with the specifications. PG test reports of the turbine and associated

equipment data need to be collected. The consolidated data sheets need to be given in the

report for reference.

During the familiarization on power plant and its operation, plants observation and past data

should be obtained pertaining to the:

Past performance trends on turbine loading, operation,


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PLF Major constraint in achieving the high PLF, load or efficiency

Major renovation and modifications carried out in the recent past

Operational failures leading to in efficient operation

Tripping

Performance of associated equipment (condenser, boiler, etc)

Plant side initiatives to improve the performance and efficiency of the Turbine

All major observations arrived at during the discussions, which affect the performance and

energy efficiency of the turbine, it is suggested to verify the records and history.

8.6.2 Turbine heat rate evaluation and efficiency

The trials are to establish heat rate (kcal/kWh) and turbine efficiency under, as run conditions

have to be carried out. The efficiency method given in this procedure is the enthalpy drop

efficiency method. This method determines the ratio of actual enthalpy drop across turbine

section to the isentropic enthalpy drop.

This method provides a good measure for monitoring purposes. Each section of the turbine

must be considered as a separated turbine. Each section should be tested and results are

trended separately. While conducting the tests, it has to be ensured that, it is conducted over

normal operating load range. The following gives the data sheet for measurements:

The following Table 8-3 gives the data sheet for measurements and observations for conducting

as run test for turbine efficiency evaluation


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Table 8-3: Data sheet for turbine efficiency evaluation

Operating parameters Symbol Unit As run data

Date -

Duration h

Avg. Unit load MW

% of NCR %

Frequency Hz

Speed rpm

Control valve A % open

Control valve B % open

Main steam flow tph

Feed water flow tph

HP turbine inlet temperature (left/right)OC

HP turbine inlet Pressure (left/right) Kg/cm2

IP turbine inlet temperature (left/right) OC

IP turbine inlet Pressure (left/right) Kg/cm2

LP turbine inlet temperature (left/right)OC

LP turbine inlet Pressure (left/right) Kg/cm2

Condenser vacuum (A/B) MWC

LP gland steam line pressure Kg/cm2

LP gland steam line temperature OC

Super heater spray tph

Reheater spray tph

Others

Ext. to Feed Heaters Pressure

Ext. to Feed Heaters Temp

Turbine heat rate is given by:Q1 Main steam flow Kg/h

H1 Main steam enthalpy Kcal/kg

h2 Feed water enthalpy Kcal/kg

H3 Hot reheat enthalpy Kcal/kg

H2 Cold reheat enthalpy Kcal/kg

Q2 Reheat steam flow Kcal/kg


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Turbine cylinder efficiency is given by:

The following Table 8-4 data sheets given in the can be used for turbine cylinder efficiency

evaluation.

Table 8-4: Turbine efficiency evaluation data sheet

Operating parameters Unit DesignAsrun

Deviation fromdesign

Remarks

Avg. Unit load MW

% of NCR %

Frequency Hz

Speed rpm

Main steam parameters -

Pressure Kg/cm2

TemperatureOC

Enthalpy Kcal/kg

Entropy Kcal/kg/OC

Exhaust steam parameters -

Pressure kg/cm2

TemperatureOC

Enthalpy Kcal/kg

Entropy Kcal/kg/OC

Actual enthalpy drop Kcal/kg

Isentropic enthalpy drop Kcal/kg

Cylinder efficiency %

The above table can be used for all stages such as HP, IP and LP turbines.

After evaluating the turbine heat rate and efficiency evaluation, check for the deviation from the

design and identify the factors contributing for the deviations. The major factors to be looked

into are:

Main steam and reheat steam inlet parameters

Turbine exhaust steam parameters

Reheater and super heater spray

Passing of high energy draining

Loading on the turbine


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Boiler loading and boiler performance

Operations and maintenance constraints

Condenser performance and cooling water parameters

Silica deposition and its impact on the turbine efficiency

Inter stage sealing, balance drum and gland sealing

Sealing fins clearances

Nozzle blocks

Turbine blade erosion

Functioning of the valves

Operational status of HP heaters Performance of reheaters

8.6.3 HP Feed Heaters and LP Feed Heaters

Collect the specifications given in the for HP heater Table 8-2.

Table 8-2: Specifications of HP heaters

Unit HP heater # HP Heater # HP heater #

Heater position (horizontal/vertical) -

H P heater ID code & number -

No of zones (De-superheating,condensing, drain cooling)

-

No of tubes No

Surface area m2

Tube size (OD x thickness) mm

Feed water inlet temperatureOC

Feed water inlet temperatureOC

Extraction steam flow tph

Extraction steam pressure Kg/cm2

Pressure drop (water side) mWC

TTDOC

DCA Drain cooler approachtemperature

OC

Temperature raiseOC

Similarly collect the specifications of LP heaters.


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8.6.4 H P Heaters and LP heaters

The performance of the feed water heaters can be analyzed by monitoring:

The terminal temperature difference,

Drain cooler approach temperature,

The pressure drop on the feed water side

Temperature side across the heater

The approach temperature (DCA)

Use the following data sheet Table 8-3 for compilation of data of HP heaters (as an example, if

the plant has three HP heaters HPH-5, HPH-6 & HPH-7)

Table 8-3: Data sheet for HP heaters

Unit HPH 5 HPH 6 HPH 7

Design Actual Design Actual Design Actual

Feed water entering temp. OC

Feed water entering press. kg/cm2g

Feed water leaving temp. OC

Feed water leaving press. kg/cm2

HPH shell press. kg/cm2

HPH extraction temp. ppm

HPH extraction press. kg/cm2

HPH drain temp. OC

Feed water diff. pressure. kg/cm2

While collecting the heater wise parameters, collect the following

Unit load MW

Main steam pressure

Main steam temperature

Feed water flow

Super heater attemperation flow

Reheater attemperation flow

Boiler feed pump discharge pressure

HPH levels


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Condenser vacuum

Barometric pressure

After the collecting the above data, evaluate the following

Terminal temperature difference TTD

Heater drain cooler approach temperature difference DCA

Temperature rise across TR

Terminal temperature difference, TTD = tsat- tfw out

where:

Drain cooler approach temperature, DCA inOC = tdrain- tfw out

where:

Temperature raise TR = tfw in - tfw out

where:

While conducting the energy audit of HP heaters, check for the following, the above three

performance parameters are deviating from the design and actual raise in feed water

temperature is low:

Excessive make up

Poor water heater performance

High terminal temperature difference

Excessive venting (worn vents, altered set point, vent malfunctioning)


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High water level (tube leaks, improper setting)

Header partition leaks

Non condensable gases on shell side

Excessive tube bundle pressure drop (excessive number of tubes plugged, tubes folded

internally)

High drain cooler approach temperature

Drain cooler inlet not submerged

Low water level (improper setting, excessive FW heater drain bypass improper setting

/bypass valve left open/bypass malfunctioning/bypass valve leaks)

Excessive tube bundle pressure drop (excessive number of tubes plugged/tubes folded

internally)

Feed water heater bypassed

FW heater bypass valve leaking

Similar approach shall be followed for LP heaters. Based on the above, if the HP heaters

performance is poor, then additional load on economizer can be estimated by using the data

sheet.

8.6.5 Key observations and Analysis

This forms the major component of energy audit system the details should be given in details

pertaining to the section mentioned in the earlier sections:

High Reheater Spray

Superheater Spray

Deviation from Design parameter Main steam Pressure, temperature, flow

Condenser Vacuum.

Bab 8 - Turbine

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