Turbine helpful intro

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Steam Turbine Training


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The world leader in gases for industry, health and the environment

Topics

General Information about steam turbine1) Definition of steam turbine

2) History of steam turbine

3) Turbine type

4) Principle of operation and design

5) Operation & Maintenance

6) Thermodynamics of steam turbines

HTC turbine type

HTC Turbine Introduction1) Condensing system 7) Rotor

2) Air ejector 8) Control Valve

3) Turbine casing 9) Main oil pump

4) Seal ring of L-shaped cross section

5) Eccentric guide stem

6) Guide blade carrier

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Topics

General Information about steam turbine

1) Definition of steam turbine


3) Turbine type




HTC turbine type







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Steam Turbine Definition

A steam turbine is a device that extracts thermal energyfrom pressurized steam and uses it to do mechanical

work on a rotating output shaft.

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Topics



3) Turbine type




HTC turbine type







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History of steam turbine

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The first device that may beclassified as a reaction steam

turbine was little more than a

toy, the classic Aeolipile.


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History of steam turbine

Parson steam turbine in 1884, 7.5 kW (10 hp) of electricity. de Laval turbine

Aurel Stodola, a Slovak physicist and engineer and professor

at Swiss Polytechnical The Steam Turbine and its

perspective as a Heat Energy Machine.

Brown-Curtis turbine developed in the 1900s

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Topics



3) Turbine type




HTC turbine type







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Turbine Types

According to Steam Supply & exhaust condition1. Condensing turbine

2. Back pressure turbine

3. Reheat turbine

4. Extracting type turbine

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Turbine Types

According to Casing or shaft arrangement1. Single casing turbine

2. Tandem compound turbine

3. Cross compound turbine

Two-flow rotors turbine

According the way extracting energy from steam

1. Reaction turbine

2. Impulse turbine

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Impulse & reaction turbine

To maximize turbine efficiency the steam isexpanded, doing work, in a number of stages. These

stages are characterized by how the energy is

extracted from them and are known as either impulse

or reaction turbines. Most steam turbines use a

mixture of the reaction and impulse designs: eachstage behaves as either one or the other, but the

overall turbine uses both. Typically, higher pressure

sections are impulse type and lower pressure stages

are reaction type.

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Impulse turbines

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An impulse turbine

has fixed nozzles that

orient the steam flowinto high speed jets.

These jets contain

significant kinetic

energy, which is

convert into shaft

rotation by the bucketlike shaped rotor

blades, as the steam

jet changes direction.


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Impulse turbines

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In the reaction turbine,

the rotor blades

themselves are

arranged to form

convergent nozzle's.

This type of turbine

makes use of the

reaction force produced

as the steam

accelerates through thenozzles formed by the

rotor. Steam is directed

onto the rotor by the

fixed vanes of the

Stator. It leaves the

stator as a jet that fillsthe entire

circumference of the

Rotor


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Topics



3) Turbine type




HTC turbine type







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Principle of operation and design

An ideal steam turbine is considered to be anisentropic process, or constant entropy process, in

which the entropy of the steam entering the turbine is

equal to the entropy of the steam leaving the turbine.

No steam turbine is truly isentropic, however, with

typical isentropic efficiencies ranging from 2090%

based on the application of the turbine.

The interior of a turbine comprises several sets of blades, One

set of stationary blades is connected to the casing and one set

of rotating blades is connected to the shaft. The sets intermeshwith certain minimum clearances, with the size and configuration

of sets varying to efficiently exploit the expansion of steam at

each stage.

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Topics



3) Turbine type




HTC turbine type







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Operation & Maintenance

Steam Turbine warm up

1) the main steam stop valves (after the boiler) have a bypass line to allow

superheated steam to slowly bypass the valve and proceed to heat up the

lines in the system along with the steam turbine.

2) Also, a turning gear is engaged when there is no steam to the turbine to

slowly rotate the turbine to ensure even heating to prevent uneven

expansion.

3) After first rotating the turbine by the turning gear, allowing time for the rotor

to assume a straight plane (no bowing), then the turning gear is

disengaged and steam is admitted to the turbine, first to the astern blades

then to the ahead blades slowly rotating the turbine at 1015 RPM(0.170.25 Hz) to slowly warm the turbine.

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Speed regulation

The control of a turbine with a governor is essential, as turbines need to

be run up slowly, to prevent damage while some applications (such as

the generation of alternating current electricity) require precise speed

control. Uncontrolled acceleration of the turbine rotor can lead to an

overspeed trip, which causes the nozzle valves that control the flow of

steam to the turbine to close. If this fails then the turbine may continue

accelerating until it breaks apart, often spectacularly. Turbines are

expensive to make, requiring precision manufacture and special quality

materials.

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Steam turbine maintenance1) Vibration (imbalance of rotor)

2) Rapid impingement / erosion of the blade (water get in)

3) Destruction of thrust bearing (water get in)

Maintain steam quality (Dry & Superheated steam)

1) PH (J10 water, 9.6 to 10.2)

2) Degas cation Conductivity 0.2 to 0.3 ps/cm

3) Pressure (J10, ST2, 10.2 bar, ST1, 42 bar)

4) Temperature (J10, ST2, saturated T 187C, ST T 217C, ST1 T 373C)

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Topics



3) Turbine type




HTC turbine type







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Thermodynamic of steam turbines

Rankine cycle

The Rankine cycle is a cycle that converts heat into work

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Thermodynamic of steam turbines

Process 1-2: pressure build up Process 2-3: temperature build up

Process 3-4: translate pressure & temperature into

kinetics

Process 4-1: condense stage

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Topics



3) Turbine type




HTC turbine type



3) Turbine casing 9) Main oil pump4) Seal ring of L-shaped cross section



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HTC turbine type

HTC mainly supplies the reaction turbine with following 10 basicmodels: NK, NG, HG, ENK, ENG, HNK, HNG, EHNK,

EHNG and WK. The meanings of each letter are defined as follow:

1. N: usual inlet steam parameters 10.0Mpa (a), 510C, max

2. H: High inlet steam parameters 14.0Mpa(a), 510C, max

3. K: Condensing steam turbine

4. G: Back-pressure steam turbine

5. E: Extraction steam turbine

6. WK: Condensing steam turbine with double split flow, Max Inlet steam

parameters: 1.6Mpa(a), 420C

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HTC turbine type

ST5001Type: NG32/25

NG: Backpressure steam turbine with usual inlet steam parameters

32: the inner diameter of steam inlet section is 320 mm

25: the diameter of last stage of the rotor is 250 mm

No extension section

ST5002

Type: NK50/56

NK: Condensing steam turbine with usual steam parameters

50: the inner diameter of steam inlet section is 500 mm

56: the diameter of last stage of the rotor is 560 mm

No extension section

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Topics



3) Turbine type




HTC turbine type

HTC Turbine Introduction

1) Condensing system 7) Rotor






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HTC turbine Condensing system

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Main Function of Condenser1) Condense the exhaust steam into condensate & carry

off the heat when steam was condensed

2) Build & maintain the vacuum at turbine exhaust port

so that the steam expander pressure is reduced as

low as possible

3) It increase the usable enthalpy drop of steam

4) Condensate may be circularly used

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The main failure of CondenserVacuum is keeping decreasing for some reasons

How to detect the vacuum failure1. Through vacuum gauge

2. Temperature condition of exhaust casing

3. Inlet opening of air ejector

4. Starting of the standby air ejector

Potential cause of the vacuum failure1. No cooling water supply

2. Not enough cooling waiter supply

3. Water level high

4. Cooling surface dirt of condenser

5. Vacuum system leakage is excess

6. Air ejector working abnormal

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Topics



3) Turbine type




HTC turbine type



3) Control system 9) Main oil pump

4) Turbine casing



7) Guide blade carrier30


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HTC turbine Air ejector

The main function of air ejectorTo extract air from steam side of condenser continuously so that condenser maintain a

vacuum and transmits heat

Main failure of air ejector1. Difference between water

outlet temperature & the

vent steam temperature

is increased

2. Water/steam accumulation

in vent outlet

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HTC turbine Air ejector

Potential cause of air ejector failure1. Leakage on the air suction piping or valve stem

2. Steam pressure is different with the design value

3. Humidity of steam is too high

4. Damage of the strainer cause nozzle blocked

5. Nozzle & expansion piping is rusty

6. Nozzle location is wrong

7. Condensing pressure is high

8. Ejector is running at over-load condition

9. Drain piping of inner-condenser and after condenser is chocked

10. Leakage with the tube sheet

11. The cooling of mix air is not enough

12. Cooling water quantity is not enough

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Topics



3) Turbine type




HTC turbine type




4) Turbine casing





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HTC turbine Control system

Control system = Governing system + Auxiliary

system + Monitoring system + protection system

1. Governing system=speed control 505

2. Auxiliary system= steam control, pump control,

ect

3. Monitoring system=vibration & positionmonitoring

4. Protection system= shutdown signal control

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Topics



3) Turbine type




HTC turbine type




4) Turbine casing





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HTC turbine turbine casing

The casing is a container for the through-flow section of the turbine. The casing consists of

the front casing and rear casing (exhaust casing) which have vertical joint surface. They arealso divided along the horizontal plane into top and bottom halves. The vertical and

horizontal split flanges are connected with bolts.

The front casing is a steel casting, while the exhaust casing is iron casting or welds.

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Topics



3) Turbine type




HTC turbine type



3) Control system 9) Main oil pump4) Turbine casing





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HTC turbine Seal ring of L-shaped cross section

In the reaction turbine (except for the model WK), an seal ring of

L-shaped cross section is used as the connection between the

outer casing and inner casing, nozzle box or steam chamber.

The steam from the governing valve enters into the

corresponding steam dome of the nozzle box via the angle ring.

There are 2 structures of angle ring.

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HTC turbine Seal ring of L-shaped cross section

In the reaction turbine (except for the model WK), an seal ring of

L-shaped cross section is used as the connection between the

outer casing and inner casing, nozzle box or steam chamber.

The steam from the governing valve enters into the

corresponding steam dome of the nozzle box via the angle ring.

There are 2 structures of angle ring.

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Topics



3) Turbine type




HTC turbine type








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HTC turbine Eccentric guide stem

The lateral or axial centres of the inner casing, the steam

chamber, the guide blade carrier and the labyrinth seal isadjusted with the eccentric guide stem when mounting them into

the outer casing. In the backpressure turbine, the alignment

between the casing and the rear pedestal is adjusted with the

eccentric guide stem.

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Topics



3) Turbine type




HTC turbine type








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HTC turbine Guide blade carrier

The guide blade carrier is one of the essential component in

turbine through-flow section and accommodates several stagesof fixed blades. There is one or several guide blade carriers of

pressure stages with different size in a turbine according to the

different parameters and characteristics. The structure of the

guide blade carrier is showed below.

The guide blade carrier is

horizontally split into top

and bottom halves jointed

with bolts and positioned

with the pins

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Topics



3) Turbine type




HTC turbine type

HTC Turbine Introduction

1) Condensing system 7) Rotor



4) Turbine casing





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HTC turbine - Rotor

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HTC turbine - Rotor

The rotor is a single forging together with the control stage disc andthrust collar, on which the emergency governor, the moving blades, the sealing

strips, the ratchet wheel for turning gear and the coupling are mounted.

3 kinds of blades, control stage, the pressure stage (or called as

drum stage) and the low-pressure stage. The front two are the milledstraight blades with integral shroud, while the moving blade of the low-pressure

stage is twisted blade made with finish forging or machined electrochemically. The low-pressure stages of the condensing turbine work in the wet-steam

region, so the steam flowing out of the guide blade contains the water droplets.

The axial distance between the guide and moving

blades in the low-pressure stage is kept large to facilitatethe acceleration, separation and atomization of any water droplets. This will

reduce the impact and corrosion of the droplets on the leading edges of theblades. Taken the effects of the speed, humidity and condenser pressure into

account, the leading edges of the last moving blades are hardened if necessary.

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HTC turbine - Rotor

dynamic balancing and over speed testing of the

rotor

1. The rotor dynamic balancing is done on the high speed dynamic

balancing machine at the turbine operating speed to correct the

dynamic unbalance quantity within the limit defined in the relative

standard through changing the mass distribution of the balancing

weights or screws on the balancing planes. The dynamicunbalance quantity on the rotor is caused by non-uniform mass

distribution of the rotor material, machining error and assembling

deviation.

2. The rotor over speed test is one of the factory inspection items, it

should be done on special device under defined operating

condition and environment,

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Topics



3) Turbine type




HTC turbine type




4) Turbine casing




HTC t bi C t l l


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HTC turbine Control valve

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HTC t bi C t l l


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Function of Control valve

The control valve functions for regulating the steam flow based on the

command from the control unit to make the controlled parameters

(output or speed , inlet steam pressure, back pressure and etc.) of the

turbine meet the operation requirement.

Structure of Control valveThe control valve consists of three main sections, the governing

valve -- valve spindle, valve beam, valve cone and valve seat, the

operating mechanism-- support and lever, the oil relay

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HTC t bi C t l l


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Governing Valve

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HTC t bi C t l l


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Oil relay

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T i


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Topics



3) Turbine type




HTC turbine type







HTC t bi M i il


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HTC turbine Main oil pump

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HTC t bi M i il


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HTC turbine Main oil pump

Function of main oil pump

1. The main oil pump provides the turbine-set with governing oil

and lubricating oil. It is a single-stage, horizontal centrifugal

pump and is directly driven by the turbine rotor.

Structure of main oil pump

1. single-cast design

2. aluminium alloy impellor

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ENDQ&A

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