to article 142 of this Guideline regarding quality of water, steamand remaining salt and article 102 of

this Guideline regarding quality of gas and oil. It must be refilled according touremanufact recommendation regarding chemicals.It must be complied with relevant regulations regardingash

and slag.

3. The gas infection of rooms, manholes, tunnels and other works must be checked;

It must be checkedhet gas infection of rooms, manholes, tunnels and other worksperiodically according to relevant regulations. In addition, it must be checked oxygen concentratiton prevent oxygen deficiency before going into manholes, tunnels etc. It must be referred to Article 126 of this Guideline regarding risk of oxygen deficiency.

4. Discharge water quality must be defined.

It must be referred to Article 228 of this Guideline regarding discharge water quality.

Article 230. Boiler water

It must be maintained the quality of boiler water to prevent erosion and destruction of boiler tubes and damage of steam turbine blades. It must be referred to Article 142 of this Guideline regarding ualityq

of boiler water and Article 225 of this Guideline regarding point to be checked at daily patrol and inspection of chemical dosing equipment.

Article 231. Discharge of boiler water

1. During boiler starting up

It must be conducted blow outside boiler at feed water rate 25% of ECR through outside blow valve of water separator drain tank by BFP booster pump system during boiler cold clean up. It must be

judged completion of blow byturbidity and total iron according to water quality standard of condensate demineralizer. After above blow, it must be changed water separator drain system from outside boiler to condenser return and enhanced water quality through condensate demineralizer.

2. During boiler operation

Impurities in feed water are condensed in steam drum in drum boiler.mpurityI concentration is kept within acceptable value by blowing feed water from drum and steam quality to steam turbine is maintained. On the other hand,mpurities in feed water are supplied to steam turbine with steam because drum is not installed and mpurities are not discharged by drum blow in once-through boiler.

Thus, it must be made use of high quality feed water meeting acceptable value in once-through boiler.

Chapter 11 Pipelines and Valves

Article 232. Inspection before operation

Pipeline and valves are damaged by various causes. Major root cause of damage of pipeline and valves are shown as follows:

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1.Major root cause of damage of pipeline and valves

(1)External root cause

1)Earthquake

2)Typhoon

3)Tidal wave

(2)Internal root cause

1)Resonance with vibration of connected equipment

2)Stress by binding pipeline

3)Thermal stress at startup, stop and load change of power plant

4)Corrosion due to fluid in pipeline and valve

5)Thermal impact due to back flow of drain

It must be checked status of pipeline, valve and auxiliaries to prevent above damage at daily patrol and inspection. Point to be checked at daily patrol and inspection is shown as follows;

2.Point to be checked at daily patrol and inspection

(1)Pipeline and valve

1)Leak

2)Corrosion

3)Breakage

4)Loose and defluxion of bolts

5)Overheat etc.

(2)Thermal insulation

1)Defluxion

2)Breakage etc.

(3)Fixed frames, brackets and sliding supports

1)Corrosion

2)Breakage

3) Loose and defluxion of bolts etc.

Article 233. Inspection in operation

It the must be conducted following items at an appropriate time, when pipelines are operated under existing regulations:

1.The thermal expansion by readings of indicators must be checked. Pipelines must not be stuck and vibration must not be increased;

When thermal expansion of pipeline is blocked, excessive stress is occurred in pipeline and pipeline is damaged. In addition, vibration of pipeline is occurred and pipeline is damaged by fatiguefracture. Thus, it must be confirmed status of ermalth expansion of pipeline compared to design value and measurement record up to the present when measuring movement of pipeline.

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2.Metal conditions must be monitored periodically and the shortcomings of welded seams must be checked;

It must be checked metal conditions and shortcomings of welded seams at daily patrol and inspection to detect defects in pipeline early. And, it must be referred to paragraph 1 and 4 of this article.

3. The tightness of valves and jointed flanges must be observed;

It must be checked leak form valves andjointed flanges at daily patrol and inspection to operate power plant stably and maintain efficiency of power plant. In addition, it must be checked loose of bolts of valves and jointed flanges by test hammer to prevent leak from them, and retightened bolts by torque wrench when detecting loose of them.

4. The working temperature mode of metal in each startup and stop must be checked.

Thermal stress is occurred at startup and stop of power plant and it is repeated every startup and stop. And they are accumulated as time goes by, there is a possibility that pipelines are damaged regionally. Thus, it must be confirmed pipelines is not overheated by using portable thermometer etc.

5. Maintenance

When detecting defects in valves and pipelines during operation of power plant and standby system or standby equipment is installed, it must be changed from operating system (equipment) to standby system (equipment) and maintained damaged parts. When standby system or standby equipment is not installed, it must be maintained under operation or stopped power plant if necessary. In addition, it must be referred to TCVN 6158 (1996) regardingechnicalt requirements for vapor and hot water pipelines.

Article 234. Safety of pipelines system

When connecting low-pressure pipeline with high-pressure one, it must be opened valve gradually confirming status of low-pressure one. There is a possibility that low-pressure pipeline is damaged when opening valve quickly. As well as connecting low-temperature pipeline with high-temperature pipeline, it must be opened valve gradually confirming status of low-temperature one.

Article 235.

(Nothing)

Article 236. Check of thermal insulation

It must not be touched bnormal temperature rises of thermal insulation surface and heat leakspart directly to prevent burn injury. When there is a possibility that abnormal temperature rises of thermal insulation surface and heat leaksare conducted, it must be checked temperature by portable thermometer. Major piping and valve installed with thermal insulation are shown as follows;

1.Boiler

(1)Steam piping (main steam piping, reheat steam piping, high temperature turbine bypass piping), safety valve

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2.Steam turbine

(1)Steam piping (main steam piping, reheat steam piping, high temperature turbine bypass piping), feed water piping, main valves (MSV, CV, RSV and CRV)

Photo 236-1 Steam turbine

3.Gas turbine

(1)LNG piping, LNG valve

Photo 236-2 LNG piping

Article 237.

(Nothing)

Chapter 12 Auxiliaries for Thermo-mechanical Section

Article 238. Confirmation before start-up

After repairing or stopping operation over period set by the Owner, status of protectors, automatic and safety equipment, valves and metersmust be checked before energizing auxiliaries for operation. Because it must be stopped these auxiliaries safely and stably by protectors and safety equipment etc. when they have troubles and are stopped urgentlyPoint. to be checked at inspection ofprotectors, automatic and safety equipment, valves and meters are shown as follows;

1.Protectors, automatic and safety equipment

(1)Corrosion

(2)Breakage, crack, deformation

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(3) Loose and defluxion of bolts etc.

2.Valves and meters

(1)Leak

(2)Corrosion

(3)Breakage

(4) Loose and defluxion of bolts etc.

Article 239. Protection of auxiliaries

It must be prohibited from energizing auxiliaries after any stop due to the fault of protectors to stop auxiliaries until the fault is removed.Because there is a possibility that auxiliaries are damaged by energizing them. Point to be checked at energizing auxiliaries is shown as follows;

-It must be confirmed maintenance of auxiliary is completed.

-It must be confirmed pertinent auxiliary is not under another maintenance work.

-It must be prepared staring of auxiliary if it is started afterenergizing it. (e.g. Filling water in pump)

-It must be informed central control room of energizing auxiliary.

-It must be conducted operation test for protector of auxiliary and confirmed that it is operated stably if necessary.

-It must be informed central control room and returned to normal operation after confirming that repaired auxiliary is normal.

Article 240.

(Nothing)

Article 241. Pressure reducer and attemperator device

It must be prohibited from operating pressure reducer and attemperator when safety valve at depressurized steam point is locked or brokenBecause. it can not be reduced fluid pressure and auxiliary body and piping etc. are damaged when fluid pressure is raised suddenly. Thus, it must be confirmed status of safety valve at daily patrol and inspection.

Article 242. Check of vibration

Vibration of auxiliaries metered in bearings must not exceed rated value in power plant’s regulations. Thus, it must be checked vibration of rotary machine such as pump etc. periodically by potable vibration meter. It must be measured following 3 placeshenw measuring vibration ofpump and confirmed measured value is met acceptable value. In addition, vibration of large size auxiliaries such

as FDF, BFP etc. can be confirmed by auxiliary’s vibration monitoring system in central control room.

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