Turbine section of gas turbine

MAKTAB KEJURUTERAAN JEFRI BOLKIAH
KUALA BELAIT
NEGARA BRUNEI DARUSSALAM

ASSIGNMENT No.ONE
Please Tick (  ) First Attempt:  Re-Do: 

TITLE: TURBINE SECTION OF GAS TURBINE

UNIT TITLE: INDUSTRIAL GAS TURBINE

NAME/ID CARD NUMBER: (session 2012/2013)

GROUP/LEVEL: DIPLOMA YEAR 1 MARINE ENGINEERING ( )
TH
DATE GIVEN: 21 NOVEMBER 2012 DATE SUBMITTED: 02TH NOVEMBER 2012

Assessor: Mohammad Iskandar Bin Hj Jani
FINAL MARK
Signature: Date.

Internal/External Verifier. %
Signature: Date.

1

Industrial Gas Turbine, Assignment
DIP 1 Marine Engineering 2011/2012
TURBINE SECTION OF GAS TURBINE

NAME: ABD AMMAR AR-RASYID BIN RAZALI

COURSE: ND1 MRE ‘A’

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Abd Ammar Ar-rasyid bin Razali
ND1 MRE ‘A’

Table Of Content
Intro
1. Introduction Pg.4
2. Turbine definition Pg.4
3. Turbine section of Gas turbine Pg.5

Turbine section part
1. Turbine Section part Pg.7
2. Turbine Section Part Pg.8

Turbine Inspection
1. Turbine inspection Pg.9
2. Type of inspection Pg.10
3. Combustion inspection Pg.11
4. Borescope Pg.13

Purpose of Preventive Maintenance Pg.14
Procedure for Carrying Major Inspection Pg.15
Conclusion pg.16
References Pg.16

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Introduction
This assignment was given on the last week of school days before the end of the first
semester of 2011/2012 season by our Industrial Gas Turbine instructor Mohd Iskandar
B. Hj Jani , it is to be done during the one month holiday . For me this is quite good
for the student so that the will be able to learn on their own. In this assignment, I will
talk about the turbine section of a gas turbine. First of all what is a turbine?

Turbine definition:
A turbine is a rotary engine that extracts energy from a fluid flow. Claude Burdin
take the term from the latin name turbinis, or Vortex (during an 1828 engineering
competition).

The simplest turbines have one moving part, consist of a rotor assembly, which is a
shaft with blades attached. Moving fluid acts on the blades or the blades react to the
flow, so that they rotate and impart energy to the rotor. Early turbine examples are
Windmills and Water Wheels.

Gas, steam and water turbines usually have a casing around the blades that focuses
and control the fluid. The casing and blades may have variable geometry that allows
efficient operation for a range of fluid-flow conditions.

A device similar to a turbine but operating in reverse is a Compressor and Pump. The
Axial Compressor in many Gas Turbine engines is a common example .

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TITLE: TURBINE SECTION OF GAS TURBINE

Turbine section of the Industrial Gas Turbine does a number of things depending on
what type of engine its coming from, but in all engines, it extracts energy from the
combustion gasses and turns the shaft which also turns the compressor section.

(diagram of a turbine section)

Rotating compressor: sucks in the atmospheric air (pressurized it) and forces it into
the combustion chamber in a steady flow. Since the working fluid for the turbine is
air, the expansion will be done by adding fuel to the compressed air which gives rise
in temperature of the mixture air and combustion product.

Combustion chamber: is a rotary engine engine that extracts energy from the flow of
hot gas produced from by combustion of gas/fuel oil in a steam of compressed air. It
has an upstream Air Compressor (radial or axial flow) mechanically coupled to a
downstream Turbine and a Combustion Chamber in between.

TURBINE : Is a rotary engine that extracts energy from a fluid flow.To extract the
energy from the high velocity gas flowing from the combustion chamber.The resulting
gases are directed over the turbine’s blades, spinning the turbine, and, mechanically,
powering the compressor.Finally, the gases are passed through a Nozzle, generating
additional thrust by accelerating the hot exhaust gases by expansion back to
atmospheric pressure.
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Function of the turbine section

The main purpose of a Turbine is to extract the energy from the high pressure and high
velocity gas flowing from the combustion chamber , these will cause the turbine blade to
rotate and run the compressor, if the turbine is assembled in a single shaft with the
compressor .

The system goes like this, something boils water which creates steam, this being much
larger than liquid water increases pressure, creating a movement of air through the
turbine. This makes the turbine rotate, which generates electricity. It does this by
rotating a magnet inside a coil. This induces an electric current in the coil. Magnetic
fields and electric fields are related: when one changes, the other is created. And an
electric field pretty much means voltage, which creates a current.

The Turbine Section of an Industrial Gas Turbine does a number of things depending on
the type of engine from the combustion gases and turns the shaft which also turns the
compressor section.

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TURBINE SECTION PARTS

1) First Stage Nozzle
2) Second Stage Nozzle
3) First Stage turbine wheel
4) Second Stage turbine wheel
5) Distance Piece

1 2 5 3 4

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First Stage Nozzle

The nozzle accelerate the gas stream and direct it onto the first row mobbing blades
where the pressure energy and kinetic energy of the gas stream is converted into a
force on the blade which in turn produce a torque at the shaft in which the moving
blades are attached. The hot gas stream leaving the moving blades is directed into
the next stage where the process is repeated.

Second Stage Nozzle

The general concept with two-shaft GE-design heavy duty gas turbines is: Fuel control
is used to control the low pressure shaft speed (torque), and nozzle control is used to
control high performance shaft speed. Fuel is increased to increase or decrease Low
pressure speed (torque) and the second stage nozzles are used to "split" the power
between that required to turn the HP shaft, and control its speed, and that required
to turn the LP shaft.

FIRST STAGE TURBINE WHEEL

The first stage turbine wheel is a component of the hot section of the auxiliary power
section which converts gas energy to a rotational energy to the processor.

Second Stage Turbine Wheel

The second stage turbine wheel is use to drive the air compressor or water pump.
Main reason for multi stage of turbine is to increase the i.e the more the stages the
higher is the power produce by engine

Distance Piece

The distance piece is a structural member connecting the compressor frame. The
distance Piece are designed to contain the gas within the cylinder, but with the high
pressure it is possible that some of the compressed gas will leak.

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Turbine Inspection

Operation of the combustion gas turbine, as of any rotating power equipment, must
include a planned program of periodic inspection, with accompanying repair and
replacement of parts as necessary, to ensure the maximum availability and reliability
of the unit. Benefits, it is best to repair the turbine parts than spending more money
buying new parts for it.

Things to be inspected are such as;

Check all lubrication tube (check for any leakage and deformation)
Check lubricating oil level (from sight glass)
Take reading of oil pressure and temperature (for comparison and monitoring)
Take reading of oil pressure and temperature (for comparison and monitoring)
Take reading of engine working hours meter (for record and maintenance
purposes) i.e maintenance of lube oil carried out every 1000hrs of engine operation
Check and record ahead and astern bearing clearances (to check for shaft
misalignment)
Monitor the fuel oil consumption ( record daily fuel tank and make comparison) for
any pipeline leakage and fuel nozzle breakdown
Check for pump and motor condition for any un-usual noise, vibration and high
temperature (may indicate of bearing failure etc)
Check tank for peeling paint(indicate of overheating/rusting due to moisture)
,present of sludge and unusual foreign matter in the bottom of the tank by draining
some of the oil from the drain valve
Check lube oil properties by doing lube oil viscosity test ( to check the viscosity of
oil)
Check heat exchanger for any leak(only possible if fin type heat exchanger)

Maintenance
 Replacement of oil filter(clean the filter or change with new one if necessary)
 Check for oil contamination by doing the lube oil test(change lube oil if
necessary)
 Check for loose fitting/connection/pipe etc.
 Check oil cooler(for accumulation of dirt, grime, foreign material etc)

Cleaning of air inlet filter for diesel and compressor(change if necessary)

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Types of Turbine Inspection

The types of inspections may be broadly classified in;

1. Running Inspection is performed during start-up and while the unit is operating.
This inspection indicates the general condition of the gas turbine unit and its
associate equipment.

2. Shutdown Inspection is performed while the unit is at standstill. The shutdown
inspections include Combustion inspection, Hot gas path inspection and Major
inspections.

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Combustion Inspection

A short shutdown inspection is required to change out fuel nozzle and to check the
combustion liners, transition pieces and cross fire tubes. These parts require the most
frequent attention since continued operation with a deteriorated combustion system
and can result a much shortened life of the downstream parts, such as turbine nozzle
and buckets.

Things that need to be inspects are:

1. The nozzle
2. Combustion liners
3. Transition pieces
4. Cross fire tube

Below is a list of a typical combustion inspection and things to be inspected

• Inspect and identify combustion chamber components.
• Inspect and identify each crossfire tube, retainer and combustion liner.
• Inspect combustion liner for TBC spalling, wear and cracks. Inspect combustion system and
discharge casing for debris and foreign objects.
• Inspect flow sleeve welds for cracking.
• Inspect transition piece for wear and cracks.
• Inspect fuel nozzles for plugging at tips, erosion of tip holes and safety lock of tips.
• Inspect all fluid, air, and gas passages in nozzle assembly for plugging, erosion, burning, etc.
• Inspect spark plug assembly for freedom from binding; check condition of electrodes and
insulators.
• Replace all consumables and normal wear-and-tear items such as seals, lockplates, nuts,
bolts, gaskets, etc.
• Perform visual inspection of first-stage turbine nozzle partitions and borescope inspect
turbine buckets to mark the progress of wear and deterioration of these parts. This inspection
will help establish the schedule for the hot gas path inspection.
• Perform bores cope inspection of compressor.
• Enter the combustion wrapper and observe the condition of blading in the aft end of axial-
flow compressor with a bores cope.
• Visually inspect the compressor inlet, checking the condition of
the IGVs, IGV bushings, and first stage rotating blades.
• Check the condition of IGV actuators and rack-and-pinion gearing.
• Visually inspect compressor discharge case struts for signs of cracking.
• Visually inspect compressor discharge case inner barrel if accessible.
• Visually inspect the last-stage buckets and shrouds.

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• Visually inspect the exhaust diffuser for any cracks in flow path surfaces. Inspect insulated
surfaces for loose or missing insulation and/or attachment hardware in internal and external
locations. In E-class machines, inspect the insulation on the radial diffuser and inside the
exhaust plenum as well.
• Inspect exhaust frame flex seals, L-seals, and horizontal joint gaskets for any signs of wear or
damage.
• Verify proper operation of purge and check valves. Confirm proper setting and calibration of
the combustion controls

After the combustion inspection is complete and the unit is returned to service, the removed
combustion hardware can be inspected by a qualified field service representative and, if
necessary, sent to a qualified Service Center for repairs. The removed fuel nozzles can be
cleaned on-site and flow tested on-site, if suitable test facilities are available. For F Class gas
turbines it is recommended that repairs and fuel nozzle flow testing be performed at qualified
Service Centers.

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Borescope

A Borescope is an optical device consisting of a rigid or flexible tube with an eyepiece
on the end, an objective lens on the other linked together by a relay optical system in
between. The optical system is usually surrounded by optical fibers used for
illumination of the remote object and a rigid or flexible protective outer sheath.

Borescopes are used for inspection work where the area to be inspected is
inaccessible by other means. Commonly used in the visual inspection of turbine
engines and to a lesser extent conventional engines. . A flexible borescope includes a
bundle of optical fibers which divide the image into pixels and can be used to access
cavities which are around a bend, such as a combustion chamber or "burner can", in
order to view the condition of the compressed air inlets, turbine blades and seals
without disassembling the engine . It lets you know what to expect when you
dismantle the parts to be maintained.

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The Purpose of Preventive Maintenance

1. The care and servicing by personnel for the purpose of maintaining equipment
and facilities in satisfactory operating condition by providing for systematic
inspection, detection, and correction of incipient failures either before they
occur or before they develop into major defects.
2. Maintenance, including tests, measurements, adjustments, and parts
replacement, performed specifically to prevent faults from occurring.
The primary goal of maintenance is to avoid or mitigate the consequences of failure
of equipment. This may be by preventing the failure before it actually occurs which
Planned Maintenance and Condition Based Maintenance help to achieve. It is designed
to preserve and restore equipment reliability by replacing worn components before
they actually fail. Preventive maintenance activities include partial or complete
overhauls at specified periods, oil changes, lubrication and so on. In addition, workers
can record equipment deterioration so they know to replace or repair worn parts
before they cause system failure. The ideal preventive maintenance program would
prevent all equipment failure before it occurs.

Advantage of Preventive maintenance are:

Extends the useful lifecycle of assets decreasing the need for capital
replacements.
Enhances the efficiency of equipment keeping them running more efficiently and
lowering power expenses.
Enhances the performance of assets by increasing uptime.
Enhances customer (internal or external) service because maintenance teams
have less unplanned maintenance and can respond quicker to new problems.
Contributes positively to the reputation of companies.

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Procedure for Carrying Out Major Inspection

A major inspection is primarily a mechanical outage in which the gas turbine (and
sometimes the generator if conditions warrant) are disassembled and inspected.
Major mechanical and hot gas components are refurbished, replaced or repaired.

Whilst the machine is shut down, very often the operation of control devices (pressure
switches and -transmitters, temperature switches, etc.) are confirmed (incorrectly
called "calibrations"). Quite often LVDTs are unnecessarily "calibrated".

Typical Major inspection requirements for all machines are :
• All radial and axial clearances are checked against their original values (opening and
closing).
• Casings, shells and frames/diffusers are inspected for cracks and erosion.
• Compressor inlet and compressor flow-path are inspected for fouling, erosion,
corrosion and leakage.
• Visually inspect the compressor inlet, checking the condition of the IGVs, IGV
bushings, and first stage rotating blades.
• Check the condition of IGV actuators and rack-and-pinion gearing.
• Rotor and stator compressor blades are checked for tip clearance, rubs, impact
damage, corrosion pitting, bowing and cracking.
• Turbine stationary shrouds are checked for clearance, erosion,rubbing, cracking,
and build-up.
• Seals and hook fits of turbine nozzles and diaphragms are inspected for rubs,
erosion, fretting or thermal deterioration.
• Turbine buckets are removed and a nondestructive check of buckets and wheel
dovetails is performed (first stage bucket protective coating should be evaluated for
remaining coating life). Buckets that were not recoated at the hot gas path inspection
should be replaced. Wheel dovetail fillets, pressure faces, edges, and intersecting
features must be closely examined for conditions of wear, galling, cracking or
fretting.
• Rotor inspections recommended in the maintenance and inspection manual or by
Technical Information Letters should be performed.
• Bearing liners and seals are inspected for clearance and wear.
• Inlet systems are inspected for corrosion, cracked silencers and
loose parts.
• Visually inspect compressor and compressor discharge case
hooks for signs of wear.
• Visually inspect compressor discharge case struts for signs of
cracking.
• Visually inspect compressor discharge case inner barrel if
accessible.
• Visually inspect the turbine shell shroud hooks for sign of

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cracking

CONCLUSION

The parts are quite confusing for the first time, but with a help of a reference and
the internet I’ve able to distinguish parts of the turbine. Also, it happens to show that
great machine have their problems needed to be taken care of. Overall, I gain some
knowledge about gas turbine section parts which will help me to go through my course
much simpler and easier.

References

https://www.google.com.bn/search?q=procedure+for+major+inspection&hl=en&sa
fe=off&tbo=d&source=lnms&tbm=isch&sa=X&ei=aGHiUIPcBqeziQev14BQ&ved=0CA
cQ_AUoAA&biw=1366&bih=662

http://en.wikipedia.org/wiki/Preventive_maintenance

http://www.proscopehr.co.za/hawkeye-borescopes/hawkeye-product-range/flexible-
borescopes/pro-flexible-borescopes.html

https://www.google.com.bn/#hl=en&safe=off&tbo=d&tbm=dsc&sclient=psy-
ab&q=distane+piece&oq=distane+piece&gs_l=serp.3..0i13l4.227912.232939.11.233989
.13.12.0.1.1.0.135.1381.0j12.12.0.les%3B..0.0...1c.1.cV8GzWa_1-
4&pbx=1&bav=on.2,or.r_gc.r_pw.r_qf.&bvm=bv.1355534169,d.aGc&fp=c43b932bc261
b565&bpcl=40096503&biw=1366&bih=705

https://www.google.com.bn/search?q=honeywell+second+stage+turbine+wheel+turbi
ne+section&hl=en&safe=off&tbo=d&noj=1&source=lnms&sa=X&ei=15_hUM2kKcufiAeG9
IH4DA&ved=0CAkQ_AUoAA&biw=1366&bih=705

https://www.google.com.bn/#hl=en&safe=off&tbo=d&sclient=psy-
ab&q=how+second+stage+turbine+wheels+works&oq=how+second+stage+turbine+whe
els+works&gs_l=hp.3...4478.7891.2.8216.12.11.1.0.0.2.551.2248.3j4j1j1j1j1.11.0.les%
3B..1.0...1c.1.m-
cRrp3DGos&pbx=1&bav=on.2,or.r_gc.r_pw.r_qf.&bvm=bv.1355534169,d.aGc&fp=ecbd
d52f22bc6188&bpcl=40096503&biw=1366&bih=705

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Turbine section of gas turbine

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