It must be checked following provisions after confirming transmitted alarm.

-Vibration value

-Bearing oil pressure

-Bearing metal temperature

-Bearing supply and return oil (scavenge oil) temperature

-Bearing return oil (scavenge oil) flow

-Differential expansion

It may be started turning oil pump when fluctuating bearing oil pressure.

It must be kept present output when changing gas turbine output.

It must be informedload dispatch center ofemergency decrease of gas turbine output if vibration value is not within acceptable value.

It must be confirmed operation status of gas turbine after decreasing output.

It must be stopped gas turbine urgently after informing load dispatch cen vibration value is not within acceptable value.

It must be referred to Article 199 of this guideline regarding emergency stop of gas turbine.

Figure 208-1 Point to be checked when going up vibration of gas turbine

Article 209.

(Nothing)

Chapter 8 Diesel Generator

Article 210. General provision

A diesel generator for “emergency power” should supply power to maintain the security and function of electrical equipment in the power station to prepareforthe next plant start-up, when the commercial power supply is lost.

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AC power source is commonly switched from receiving power supply to emergency power supply automatically after the diesel generator terminal voltage is established.

For this reason, technical regulation requires prevention of damage to the components of diesel generators.

Thus, a diesel generator is recommended to be capable of operating continuously for more than 60 minutes at the rated load, quantity is to be capable of operating in more than two hours, and the voltage is to be established as soon as possible in order to protect the facility during outage. Arrow of Figure 210 shows emergency power supply from the diesel generator.

P/C

D/G

Diesel Generator

Figure 210 An example of electrical connection of a diesel generator

Article 211. Operating conditions of diesel generator

1. Principles of diesel generators

Many diesel generators are driven by diesel engines of four cycles with superchargers.

The fuel of diesel engines is injected into the combustion chamber with compressed air, applying high pressure of approximately 10 to 500MPa.

Cycles of diesel engines are repetitions of intake, compression, expansion and exhaust in the same cylinder.

The air is compressed rapidly with high temperature and fuel is injected into this compressed air in the cylinder. This injection causes a blast-ignition at the same time of the injectioand; energy by expansion is transformed to rotating energy. Exhaust gas is emitted outside of the machine.

2.Fuel supply system

(1)Leakage from oil pipes

Leakage from oil pipes, etc is inspected for safety and stable combustion.If there is a leak, bolts or pipes or packing are tightened or repaired or replaced.

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(2) Amount of fuel

In order to continue operation during emergency, the amount of fuel in the fuels tank i inspected. If there is a shortage, fuel should be replenished.

(3) Fuel oil filter

A fuel oil filter is inspected by checking the difference pressure of the filter. If it is over the certain value, it is replaced for stable combustion.

(4) Characteristics of the fuel

Operations of diesel engines are greatly influenced by the characteristics of the fuel in the operating performance and durability.

Therefore, it is necessary for fuel oil to have good flammability, less hazardous combustion products.

Following items are recommended to be checked 1) Viscosity

In the combustion of fuel oil, it is necessary for atomized fuel oil to have uniform and appropriate size of the fuel particles.

Viscosity affects the atomization of the fuel.

Optimum viscosity for the combustion is determined by considering operating conditions and the design such as combustion chamber shape and dimensions.

2) Residual carbon and ash

Amount of these items do not influence the combustion directly. However, these items are difficult to burn in the combustion chamber; therefore, these substances promote the wear of each part and stick the piston ring as sediment in the cylinder.

3)Sulfur content

There is sulfur as compounds with hydrocarbon polymer, and this sulfur is reacted to sulfurous acid gas (SO2) by the combustion, finally changed to sulfuric acid gas (SO3) by combination with moisture.

This sulfuric acid causes corrosion and abrasion of cylinder liners and piston rings.

4)Moisture

High moisture contaminants cause decrease of heat generation, stain, valve stick.

Moreover, corrosion and abrasion of cylinder liners and piston rings may be caused, as mentioned above.

5)Cetane number

Cetane number indicates the ignitability of the fuel oil, therefore this number affects the start-up performance of the diesel generator, because knocking may occur if this value is too small.

It is desirable that the cetane number is not less than 45, because nitrogen oxides in the exhaust gas are increased and starting performance is deteriorated.

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3.Lubrication system

(1)Equipment in the lubrication system

In general, following equipment is installed in the lubrication system of diesel engines.

1)A main oil pump to supply lubrication oil in operation

2)An oil tank to store lubricants during stop

3)An equipment to keep the lubricant clean

4)An apparatus for adjusting the temperature of the lubricating oil

5)Flow indicator or oil pressure gauge device or situation can be seen in the appropriate position.

(2)Quality of the lubricating oil

Fundamental functions of the lubricating oil are as follows:

a.Antifriction

To prevent abrasion due to metal contact

b.Engine cleaning

To prevent the adhesion of parts by sludge

c.Engine cooling

To prevent the overheat of parts

d.Engine sealing

To prevent the leak the combustion gases from the chamber

e.Corrosion prevention of the engine

To prevent the corrosion of the parts by combustion products such as water, acid

2)Fundamental properties of the lubricating oil

To satisfy functions above, following properties are required as lubricating oil properties for a diesel engine.

a.Viscosity

Viscosity is one of the most important properties. The effect of anti-friction is due to forming fluid film on the surface, and the degree of viscosity should be enough to form this film. Lower viscosity reduces film strength, causing metal contact.

However, too high viscosity causes increase of film resistance on the surface, and engine performance is reduced as a result.

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Temperature in a diesel engine depends on the operating conditions. Particularly; temperature difference between startup and normal operation is large. Therefore, the characteristic of viscosity is required not to be varied too much by the temperature.

b.Dispersibility for cleaning

Dispersibility for cleaning means the performance to prevent aggregation of material produced by the combustion or oxidation. It is necessary to use a lubricant with excellent dispersibility for cleaning.

Some of the lubricating oil sludge-generated ash and unburned carbon, by, is dispersed as fine particles. Dispersibility for cleaning can be improved by the addition of dispersant cleaning, institutions harsh institution high output high degree of supercharging, operating conditions,

c.Acid neutralizing

Sulfur content in the fuel becomes sulfurous acid gas by combustion, and some become anhydrous sulfuric acid.

As for exhaust gas, sulfurous acid gas is corrosive to metal but not very strong, on the other hand, sulfuric anhydride produces highly corrosive sulfuric acid by reaction with the condensed water.

In order to prevent corrosion caused by these harmful substances, the lubricating oil is required to have the function of neutralizing acid by alkali.

"Alkalinity value” is the reasonable indication which evaluates this acid neutralizing (mg KOH/g). Many additives to improve the alkalinity value are identical to those for improving the dispersibility for cleaning.

d.Oxidative stability

Lubricating oil oxidizes associated with the oxygen in the atmosphere and its characteristic is altered. This oxidation reaction rate is faster in the higher the temperature condition.

Oxidation of lubricating oil causes increase of viscosity at first, worse hue next and, c black sludge at last. This sludge may clog oil holes, and piston ring may stick.

Therefore, the addition of antioxidants is recommended in order to stop this oxidation.

4.Cooling system

(1) Water quality

If cooling water is used, it is necessary to inspect water quality in advance in order to prevent scale, clogging, and corrosion.

Detail items and standard should be shown from the manufacturer, but items maythebe following.

1)pH

2)Conductivity [μS/cm]

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3)Hardness(CaCO3) [ppm]

4)Alkalinity(CaCO3) [ppm]

5)Silica SiO2 [ppm]

6)All irons Fe [ppm]

7)Ammonium ion. NH4+ [ppm]

8)Chlorine ion Cl- [ppm]

9)Sulfate ion SO42- [ppm]

10)Hydrogen sulfide H2S [ppm]

(2) Water flow

In order to maintain the temperatures at diesel generators and surroundings, water flow is inspected by an instrument such as a flow meter.

5.Generator

(1)Inspection of lubricating oil

Quantity of lubricating oil is checked by an instrument such as a level gauge.

(2) Inspection of the ground wire connection

Disconnection of the grounding system causes disasters such as electrification. Therefore, the presence of corrosion or disconnection at the grounding wires and terminals should be inspected.

If there is a slack at a terminal, it should be tightened. 6. Other items to be noticed

(1) Light load operation

In operating diesel engines, cares should be taken during light load operation. If the load is light, fuel combustion may not be good enough because fuel injection pressure is low.

In addition, temperature of piston, cylinder, and lubricating oil cannot rise enough, oil may drip from exhaust pipes, or there may be black smoke in the exhaust gas due to imperfect combustion.

Article 212. Control system

Microprocessor based modules is generally installed to enable direct interface with engine control. Therefore, circumstance such as temperature, humidity etc should be cared.

Control systems can also be designed and built using (PLC) programmable logic controllers for schemes where a more complex switching or operation is required.

1. Function

Control system of a diesel generator is classified as follows:

(1) Speed control

Speed is controlled by the governor. The fuel control valve is adjusted by the governor output signal.

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(2) Electric control

Voltage is measured by the voltage transformer and controlled by the AVR.

(3) Starting and shutdown controls

The process stipulated in Article 214 of this guideline is controlledIn.general, a diesel generator starts with low voltage detection by a relayAfter. start of the diesel generator and establishment of voltage, a synchronizing system may be used to remove human reaction time from the starting time, or the case that personnel is not available such as at remote controlled or automatic starting cases.

(4)Diesel engine and generator protection and alarm systems Diesel engine and generator protection and alarm are performed.

2.Check items

(1)Panel indication

Panel indication is checked considering following points.

1)Alarms of failure on the panel and inside the panels such as processor

2)Operating condition

3)Panel damage

4)Indicating values of instruments

(2)Cabinet (inside the panel)

Cabinet (inside the panel) is checked considering following points.

1)Alarms of failure at the processors or the controllers

2)Operating condition

3)Damage inside the panel

4)Condition of wirings and connections

5)Circumstance (Temperature, humidity, existence of moisture or dust, odor)

6)Condition of cooling fans and air filters

(3)Battery (If equipped)

Battery is used for start-up. Following points are considered when it is checked.

1)Voltage

2)Condition of electrodes

3)Liquid level

4)Condition of wirings and connections

5)Circumstance (Temperature, humidity, existence of moisture or dust, odor)

6)Damage of each part

7)Measurement of internal resistance

(4)Instrument

1)Damage or distortion ,or pollution, or corrosion of each part

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2) Indicating value

Article 213. Operation after overhaul

Following items are recommended to beinspected before the operation after overhaulto prevent hindrance during operation.

1. Conditions of each part

Following items are recommended to be inspected before operation after overhaul.

(1)Items stipulated in Article 212 and Article 216 of this guideline.

(2)Connection of wirings at terminals

(3)Conditions of installation (bolts, couplings, etc)

Operating hours are specified so thattemperature of each part of the engine and generato becomes constant.

2. Speed control test

Device test for the speed control is recommended to be performed to confirm the operating conditions of the speed control device of the diesel engine if speed control device is inspected.

3. Start-up and shut down test

Start-up and shut down test is recommended to beperformed to verify the performance of thediesel engine starting in the cold state.

Moreover, minimum starting pressure measurement is recommended to be performed, if necessary.

(1) Compressed air start

Minimum compressed air pressure to start or the possible number of start ischecked without charging air.

(2) Electric start

Start-up performance is verified by pushing the start button. 4. Load operations

Load operation is necessary to confirm the performance of thediesel engine by continuous operation for a predetermined period of time after overhaul.Test loads are selected at full load, 75%, and 50% load, in general. During this test, vibration and noise and emission should be measured to confirm the compliance with QCVN 22/2009/BTNMT, TCVN 5949 and TCVN 6962.

In addition, test items are determined, considering testing purposes and tested the type and the usage of diesel engine.

Following are examples of test items.

-Calibration records of the instruments

-Output

-Rotating speed

-Fuel consumption

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-Amount of lubricating oil consumption

-Pressure

-Temperature

-Flow of cooling fluid circulation system, total head loss

-Measurement of exhaust gas temperature and back pressure

-Exhaust gas analysis

-Vibration and noise

-Speed control

-Governor performance

Article 214. Safety of diesel generator start-up

As stipulated in Article 210 of this guideline, a diesel generator is used as emergency power supply

for the plant security. Therefore, following items are recommended to be satisfied ngas starti performance.

1. The generator is capable of starting more than three times during outage.

When starting the diesel engine, crankshaft is rotated by the starter motor, and combustion cycle starts.

When starting the diesel engine of large capacity, compressed air is blown into the cylinder in order to move the piston directly.

Therefore, start-up devices such as battery voltage or compressed air pressure are inspected for emergency.

2. The voltage of the generator is established as soon as possible seconds after it started.

In general, a diesel generator starts with low voltage detection by a relayAfter. the diesel generator start and establishment of voltage, a synchronizingsystem may beused to remove human reaction time from the starting time, or the case that personnel is not available such as at remote controlledor automatic starting cases.

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Emergency switchgear close Emergency switchgear open

Normal switchgear open

Figure 214 An example of diesel generator start-up and shutdown

Article 215. Check of vibration

The mechanism of diesel engine is to convert reciprocating piston movement, generated from the heat energy of combustion gas, to the rotating movement by the crankshaftIgnition. of a diesel engine is self ignition byhigh compression ratio.In order to obtain high compression ratio, diesela engine requires long crankshafts. This long movement of crankshafts is the source of vibration and noise of the engine.

Moreover, changes of combustion pressure generate torque fluctuations and also cause torsional vibration.

In the case of long crankshaft, this torsional vibration may destructrankshafts,c in faster speed operation.

Thus, vibration should be checked in order to prevent harmful effects on structure and performance. Allowable value of vibration should be shown from the manufacturer.

Article 216. Check of pipeline system

Pipeline system may be classified to cooling water, lubricating oil, fuel, exhaust gas and compressed air system.

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1. Cooling water

Water leak from the pipes, flow of water etc are checked. When there is a leak, bolts or packing are tighten.

2. Lubricating oil

Oil leak from the pipes, flow of oil etc are checked for fire prevention and safe operation. If there is a leak, bolts or pipes or packing are tightened or repaired or replaced.

3. Fuel oil

Oil leak from the pipes, flow of oil etc are checked for fire prevention and safe operation. Ifthere is a leak, bolts or pipes or packing are tightened or repaired or replaced.

4. Exhaust gas

Odor and noise from pipes etc are checked. Exhaust gas contains toxic gas such as nitrogen oxides and carbon monoxide, therefore, if there is a leak, bolts or pipes or packing are tightened or repaired or replaced.

5. Compressed air

If a diesel generator uses compressed air system for start-up, air leak from the pipes may cause failure of start-up. Therefore, if there is a leak, bolts or pipes or packing are tightened or repaired or replaced.

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