OPERATING MAINTENANCE MANUAL FOR AUXILIARY BOILER

This instruction manual has been prepared to serve as a guide in operating and maintaining the one(1) unit of LP steam boilers for the National Vietnam Gas Company’s Gas Supply Project to be located in Vietnam as below ; It is not intended to cover all possible variations in equipment nor to provide for specific problems which may arise. If additional information be required, the company or its field representatives should be contacted.

Doc No : 09035-62-OPM-VD-MS015-001

Job No : 2009035 Rev No : C1

Doc No : 09035-62-OPM-VD-MS015-001

Job No : 2009035 Rev No : C1

1 OPERATING & MAINTENANCE MANUAL

FOR AUXILIARY BOILER

2 PIPING AND INSTRUMENT DIAGRAM

3 MECHANICAL EQUIPMENT OP & MT MANUAL

DINH VU POLYESTER PLANT PROJECT

STEAM BOILER PACKAGE

OPERATING & MAINTENACE

MANUAL FOR AUXILIARY BOILER

1 OF 2

OPERATION & MAINTENACE MANUAL

FOR STEAM BOILER

IN DIVZ HANOI, VIETNAM

Dec 2010

2-2-4 AUTOMATIC COMBUSTION CONTROL

2-6-2 PREVENTION OF UNBURNED FUEL ENTERING

2-6-3 TROUBLE OF BURNER

2-6-4 MISFIRE OF THE GAS IGNITOR

2-6-5 POOR BURNING OF THE GAS BURNER

2-6-6 PULSATION OF GAS FLAME

2-6-7 FLAME BRUSHING OF THE FURNACE WALL TUBES

2 OF 2

2-7 LOSS OF UTILITIES

2-7-1 INSTRUMENT AIR FAILURE

2-7-4 COOLING WATER FAILURE

2-8 TABLE OF CAUSE AND EFFECT

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1 INTRODUCTION

This instruction manual has been prepared to serve as a guide in operating and maintaining the one(1) unit of LP steam boilers for the National Vietnam Gas Company’s Gas Supply Project to

be located in Vietnam as below ;

It is not intended to cover all possible variations in equipment nor to provide for specific problems which may arise

If additional information be required, the company or its field representatives should be contacted

Boiler Specification

Boiler Outlet Steam Flow : 30,000kg/hr

Boiler Outlet Steam Temperature : SuperHeated

Boiler Outlet Steam Pressure : 26 Bar G

Feed Water Temperature : 115 ℃

Firing System

Ambient Temp for Mechanical Design : 23 ℃

(1) Before start-up, the boiler shall be inspected to ensure the following points

a All the peep holes and manholes are closed And make sure of no gas leakage

b The safety equipment and interlocks are normal position

(Not bypass position)

c The instrument air, cooling water and other utilities are in service

d The feed water equipment and the chemical injection unit are in good order

e All shutdown valves (except vent valve) on fuel lines are closed

(2) Check that the following valves are closed

a Feed water control valves

b All blowdown valves and drain valves on the drum, furnace header, and level gauge

c Main steam stop valve

d All bypass valves for control valve

(3) The following valves are opened

a Vent valve on the steam line

b Feed water stop valve

c Root valves and fitting valves for water level gauge

d Drain valves for main steam line

e Stop valves of all instruments and controlling equipment

(4) Check that all the preparation for start-up has been completed and that all the automatic control system (loop) are set at manual position

(5) Check that there is sufficient preparation of chemicals for treatment of the boiler feed water and that the chemical injection pumps are ready for use (6) Check that opening of the air register vane and damper are proper position

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2-1-1-2 WATER FILLING

Water can be filled in the boiler according to the following procedure

(1) Fill water in the boiler by adjusting the BFW control valve

Continue to fill water until the drum level rise below -50 ~ -100 mm of steam drum Normal Water Level (NWL)

(2) Open the drain valve of water level gauge to check whether level gauge is

in order

2-1-2 STARTING (COLD WATER START)

WARNING

It is necessary to take special attention during boiler cold start-up

At start-up, the pressure of steam drum shall be gradually increased according to the start-up curve as shown in para 2-1-3

The boiler shall be filled with demineralized feed water The water level in the steam drum should be –50~-100mm of the normal water level (NWL)

Drain valves and vent valve on steam piping and header shall be fully opened at the beginning of pipe warming

Drain valves shall be closed after confirming the (UPSTREAM) piping has been sufficiently warmed, no drainage can be seen at the outlet of valves

When steam pressure reaches to approx 2 kg/cm2g, vent valve can be closed, and when it reaches to approx 5 kg/cm2g, drain valves can be closed

The following step guide are of the procedure for bringing a cold boiler up to normal pressure and temperature

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FIRST STEP (PURGE PERMISSIVE CONDITION)

Before we going to the burner start, The furnace purge permissive conditions as listed below shall

be proven:

1) No MFT 2) No Flame 3) No Boiler trip condition 4) Steam drum level normal 5) Ignition isolation solenoids close(62SOV624A) and vent valves(62SOV624C) open

6) Main LPG gas isolation valves close(62NV622A) and vent valves(62SOV623) open

7) F.D Fan running 8) Combustion air flow above 25% MCR

SECOND STEP (FURNACE PURGE)

When these furnace purge permissive conditions are proven, furnace purge start can be initiated

by operator’s initiation (Push button switch)

With starting command of furnace purge interfaced to DCS, inlet vane opening position for the purge rate (25% MCR) of combustion airflow will be set automatically by pre set value from DCS When all purge permissive conditions including air flow rate are satisfied, the timer will count the purge time for five(5) minutes period and the "Furnace purge progress" lamp will be illuminated If

a furnace purge permissive is lost during this time period, furnace purge will be tripped back to zero time and "boiler purge required" lamp will be illuminated again The furnace purge control will provide CRT indications to the operator of the status of the furnace purge

These include as follows;

1) Furnace purge permitted

2) Furnace purge required

3) Furnace purge in progress 4) Furnace purge completed

5) Exceed permitted time

6) Unsuccessful furnace purge

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STEP GUIDE FOR START-UP

(IN CASE OF FUEL GAS FIRING)

1

Operation mode selection

Select the manual control

mode in the window menu

Furnace purge start

Depress the "PURGE

START" touch button

Confirming the air flow more

4 Furnace purge in progress "PURGE START" lamp blinked The timer will count the purge

time for five(5)

5

Furnace purge completed "PURGE COMPLETED" lamp

lights and "START" lamp lights-out

6

Leak test

Depress the "LEAK TEST"

touch button

Operator checks pressure

drop by PI for a few minute

after closing valve

7 Leak test completed

8

MFT reset

Depress the "MFT RESET"

touch button from CCR

"MFT RESET" button lamp lights

Main LPG gas vent valve close(62SOV623) then Main LPG gas isolation valve open (62NV622A)

Main LPG Gas flow control valve open in minimum point (62FCV622)

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9

Burner ignition

Depress the "IGNITION

START" Touch button

"IGN SHUT OFF VALVE ALL CL" lamp lights-out

Burner ignition shut off valve open(62XV602)

Burner ignition vent valve close(62SOV624C)

Burner ignition trans sparking (20 sec.)

10

Detecting pilot flame "IGN SCAN PROVEN" lamp

flame for 20 sec, ignition shut off valve close(62XV602) and ignition vent valve open(62SOV624C)

11

Fuel gas firing permissive

Check purge permissive

conditions

Depress the "BNR IGNITION

" Touch button

"MAIN SHUT OFF ALL CL"

lamp goes out

Main LPG gas vent valve close(62SOV623)

Main LPG gas shut off valve open(62XV601)

Refer to fuel gas firing permissive conditions

13 When boiler load should be over than 25% of MCR, Change over the operation mode form manual control to automatic control

14 Increase load by operating master controller

Pay special attention during open the the BFW control valve

(62FV601 or its bypass valve)

In case the hammering due to flushing of hot water in the piping at the out of BFW control valve, gradually open the manual valve and increase the water flow

After filling water, the start up procedure using hot water shall be almost the same as the procedure using cold water

2-2 STEAM SENDING

2-2-1 START UP

Gradually raise the boiler pressure and temperature to required value

During this operation, keep the main steam release valve at intermediate position

2-2-2 WARMING UP STEAM LINES

Before generating steam goes main steam line, provision should be made for gradually heating and adequately draining all cold steam piping

If the main steam line is cold, it is generally advisable to raise pressure on the line by opening all valves slightly

2-2-3 CONNECTING TO PROCESS

The main header block valve (DOWNSTREAM) should be opened, when the boiler side pressure is approaching a pressure of 2~3 kg/cm2 below the main header pressure When the boiler side pressure reaches the main header pressure, the valve will open in bumpless and the steam from the boiler will connect to line smoothly According to the required quantity of steam raise the boiler load manually while the boiler load is under 25% MCR, by controlling the fuel flow controller and the air flow controller

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2-2-4 AUTOMATIC COMBUSTION CONTROL

After boiler load exceeds 25% MCR, change the fuel flow control and the air flow control from MANUAL to AUTO And then individual master controller at MANUAL position can be operated After confirming the boiler operation is stable, and the pressure of steam header is maintained, change the steam pressure control from individual master to common master on existing common steam header

Then, after confirming the boiler load reaches sufficiently high, change over the master control from MANUAL CONTROL to AUTO CONTROL

Gradually close the Main Steam Release Valve and go on to normal operation

2-2-5 LINEAR/SUDDEN LOAD CHANGE

Linear(Ramp/constant) load change at the normal operation condition will be 10% /min based on automatic control

Sudden(Step) load change at the emergency condition will be 20% /min based on remote manual control

In case emergency condition (Sudden load increase or load decrease) happen during the boiler operation, the well trained operator shall perform the step load change by remote manual control as follow ;

First, the operator shall change over the operation mode in the window menu from automatic control mode to manual control mode

When the manual control mode is selected, the next window menu will be shown the click for load increase and load decrease

The operator will achieve the sudden load change by click on load change mark with careful supervision for the deviations of output parameters such as steam pressure and steam drum level

In case the deviation of steam drum level with change up to the set point (Low water level, high water level), the operator will stay for load stabilization with limitation for click use

After load stabilization, the operator will achieve the sudden load change by click

Confirm that boiler operators have completed the preparation of boiler shutdown in consideration of steam balance of whole plant in accordance with communication for process side at the operation position

IN CASE OF GASEOUS FUEL FIRING

1

Decreasing of boiler load Change over the master (steam pressure) Controller form auto control to manual control But the other controllers such as combustion control and drum level should be kept on auto control Decrease load by operating master controller manually

- -

25% MCR load When the boiler load falls into 25% of MCR, the following actions shall be carried out

2

Change over the combustion control from auto control to manual control

- -

3

change over the boiler feed water control form auto control to manual control

- -

4

Confirm the boiler water level before extinguishing the burner, feed water shall be fed to boiler up

to the level of 250mm above normal level by feed water control valve manually

Fuel gas shut off valve close

7 Confirming gas burner

flame is completely put out

"MAIN SCAN PROVEN"

lamp lights-out

8

Visually making sure of no flame in the furnace, purge the furnace with adequate air flow not less than 25%

MCR of full load air flow for

11

Handling of boiler feed water line after extinguishing all burner

-

Close (upstream) valve of block valves of feed water flow control valve

12 Stop the chemical feed

-

All individual shut off valves will be immediately closed

Fuel gas shut off valve will

be immediately closed Fuel gas vent valve will be opened

2

Visually making sure of no flame in the furnace, purge the furnace with adequate air flow

of not less than 25% MCR of full load air flow for 5 minutes

-

F.D fan vane is adjusted

to a purge position automatically

3 Improve the faulty condition

for the boiler

2-3-3 SHORT-TIME SHUTDOWN

The procedures for shutting down the boiler for no longer than 24 hours are described in the following It is assumed that in this case boiler pressure, etc is maintained in a condition as near the normal working condition as possible The shutdown procedures are same as those mentioned in "SCHEDULED SHUTDOWN" except the following :

(1) After complete extinction of fire in the boiler, fully close the main Steam stop valve

(2) Depending on the heat capacity held by the boiler, feeding water and blowing may be continued to such an extent as to prevent boiler pressure rise, but it is necessary to limit those operations to a minimum required

(3) Even after complete extinction of fire in the combustion system, continue to run the F.D Fan for several minutes for flue gas purging and when gas purging is deemed to be completed, fully close all the dampers on the air side

(4) It is necessary to maintain boiler water level within a visible range on the water level gauge and at the same time, to confirm that boiler water properties area satisfactory

Except the case of temporary fluctuation in water level due to abnormal changes in load, if water disappeared from the water level gauge owing to a failure of the feed water equipment or erroneous operation of the operator, extinguish fire immediately

In cases where there is no experienced person capable of coping with such an emergency or there is no reliable way of immediately recovering water level without causing failure to the boiler due to low water level, do not continue to run the boiler even under light load and for a short time, but proceed as follows :

(1) Fire extinguishing Stop the supply of fuel to extinguish fire as soon as possible, closing fuel gas supervisory cock for the Burners

(2) Stop the supply of feed water Simultaneously with the stop taken under item (1), above, if water is still being fed, change over the automatic feed water control to "MANUAL" to gradually decrease feed water (Never increase the supply of feed water) and when heat from the furnace and furnace wall has declined enough, close the feed water level completely

The reason for gradual reduction of feed water flow by manual operation as above is that if one raises water level, boiler pressure parts deemed to be overheated at low level of water will be cooled rapidly by relatively cool water Therefore this must be avoided by gradual reduction

Close the main steam stop valve at the time when almost no more generation

of steam can be seen

(3) Reduce pressure Gradually reduce steam pressure by opening the steam drum air vent valve

As the boiler is cooled, gradually reduce air being supplied to the boiler If the boiler has cooled down to safe condition, close the dampers to completely shut off the entry of air into the boiler

(4) Inspection of Boiler

To avoid rapid cooling of boiler tubes and drums, do not carry out boiler water blow-off until the boiler becomes cool enough to permit a person entry into the furnace Fully examine the cause of low water level encountered and further, inspect the boiler pressure parts to see whether they are overheated, resulting

in leakage and deformation, etc After confirming that every thing is in good order, proceed to running

(3) Check the elimination of stack whether vapor is discharged

(4) Check the deviation of steam flow and feed water flow

When tube failure is deleted unfortunately immediately shut-down the boiler but not

to cool-down rapidly

Shout-down procedure is as follows

(1) Shut-down fire (2) Keep feeding water to maintain drum level, if possible

(3) Keep running F.D fan, if tube leakage is relatively small

(4) But in case tube leakage is a large degree and furnace is flooded by the water, stop F.D Fan, However, the inlet vane should be kept fully open

(5) After completely cool-down boiler, inspect in detail of damage and take a remedy action

(6) Stop the supply of feed water to the boiler

WARNING

Note :

In case that a serious tube failure of tube busting happens and so on, operator can shut-down boiler and stop auxiliary equipment only

Never approach to the boiler and keep your safe position

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2-6 FURNACE EXPLOSION

As furnace explosion originates in most cases in a failure of combustion system or an erroneous operation thereof, it is important for the boiler operator to be familiar with the specifications, performance and operation of the combustion system

2-6-1 CASES OF FURNACE EXPLOSION

(1) To avoid furnace explosion, it is necessary to pay attention to the following items :

a) No fuel in unburned condition should exist within the furnace

b) Explosive gas should not be produced by mixture of fuel and air

c) Such heat as causes the above-mentioned gas to reach ignitor temperature should not be applied

(2) In the following cases, unburned fuel may enter into the furnace

a) In case fuel leaks from a burner in the course of extinction

b) In cases where burner fire went out during boiler running and fuel could not be shut off immediately

c) In case combustion does not take place immediately at the time of ignitor

2-6-2 PREVENTION OF UNBURNED FUEL ENTERING

(1) Leak of unburned fuel This occurs in the case of a fuel gas burner ; therefore, to prevent this, be sure to take cautions against leak form the stop valve or failure to close it and

so on

CAUTION

(2) Extinction of burner fire during boiler running

In the case of extinction of burner fire during boiler running, in order that fuel may be shut off immediately in the event of a sudden extinction of fire, flame scanners always watch the burning condition, In such event, look into and eliminate the cause of the abnormal extinction of fire and undertake re-ignition

in the manner specified for the combustion system

As extinction of burner fire is often caused by the following, take due cautions :

a) Excessive lowering of fuel pressure

b) Excessive rising of wind box pressure

CAUTION

(3) Misfiring at the time of boiler start-up When ignition does not take place in several seconds after fuel injection at the time of boiler start-up, shut off fuel immediately and purge furnace interior gas, and then proceed to re-igniting

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2-6-3 TROUBLE OF BURNER

Although a burner may have been properly managed, after it has been in operation continuously over many hours, various troubles may occur because

of exhaustion and stain of the various components

Most of the troubles, which may occur during the ordinary operation, are divided as follows

(1) Misfire of the gas igniter (2) Poor burning of the gas burner

(3) Pulsation of gas flame (4) Smoke

(5) Slagging carbon on the diffuser corn or the wall tube

"Estimated Causes and effects" for each trouble are described in the table of cause and effect

It is necessary to regularly inspect and maintain the burning equipment to prevent any trouble from occurring

2-6-4 MISFIRE OF THE GAS IGNITOR

The causes of misfire are divided into the following categories

A No spark

B Sparks but misfires

C Sparks but in a short time goes out

D Miss-catch of the flame Confirm that the actual condition corresponds to one of the above and investigate the cause by referring to the following list

A 1 Power source has not been supplied 1 Inspect the fuse in the control panel

B.C 2 Excessive high wind box draft

Excessive air flow for combustion

2 Adjust the inlet vane of F.D Fan

B.C 3 Excessive low or excessive high gas

pressure for the igniter

3 Regulate the gas pressure for ignitor at 0.46 kg/cm2g at the igniter gas press Gauge

A 4 Inferior connection on the terminals of

the high tension cable

4 Inspect and clean the connection terminals

A 5 Inferior insulation of insulator for spark

plug

5 Replace the insulator

B.C 6 Blockade of the gas service pipe and

the gas nozzle

6 Clean the inside of the gas service pipe and the gas nozzle

B.C 7 Stoppage of the ignitor shutoff valve 7 Check the connections to the solenoid and

examine for any other wiring error

B.C 8 Leakage of the ignitor shutoff valve 8 Try to do leakage test If the ignitor shutoff

valve leaks, replace it

B.C 9.Inferior operation of the pressure

regulating valve

9 Repair the pressure regulating valve

C 10 Inferior insulation of insulator for flame

rod

10 Replace the insulator

2-6-5 POOR BURNING OF THE GAS BURNER

Troubles of poor burning are divided into the following categories

A Despite ignition of the igniter, gas burner misfires

B Loss of flame after ignition

C The burner has been lit off but its combustion is unstable

Confirm that the actual condition corresponds to one of the above and investigate the cause by referring to the following list

Example : Faulty condition A estimated cause item 1,2 and 4

A 1 Shortage of capacity of the gas igniter 1 Increase the igniter gas pressure

Regulate the gas pressure for igniter at 0.46 kg/cm2g at the igniter gas press Gauges

A.B.C 2 Excessive high wind box draft

Excessive air flow for combustion

2 Adjust the inlet vane of F D Fan

B.C 3 Excessive low burner gas pressure 3 Increase the burner gas pressure

C 4 Blockade of the nozzle body 4 Clean the gas nozzle

B 5 Mis-catch of the flame detector 5 Clean the inside of the guide pipe and lens at

the end of the detector body

2-6-6 PULSATION OF GAS FLAME

1 Shortage of air flow for combustion

2 Fluctuation of air flow for combustion

3 Inferior movement of the fuel - air ratio

control system

4 Hunting of the burner gas pressure

5 Blockade of the gas nozzle

6 Mixing of the drain in the fuel gas

1 Increase air flow

Re regulate fuel-air ratio

2 Check the hunting of the F D Fan inlet vanes, and the windbox dampers

Check the hunting of operating air pressure (Instrument air)for Auto Combustion Control Equip 3.Check and re-regulate the equipment for the fuel-air ratio control system (after switching the boiler control system to manual operation)

4 Check the following items Blockade of the gas nozzle

Hunting of the gas supply pressure control valve Hunting of the gas flow control valve

5 Clean the gas nozzle

6 Remove the drain in the fuel gas piping

(Water and liquefied gas)

7 Reset the opening of the air register vanes to normal positions

7 Miss setting of the opening for the air

register vanes

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2-6-7 FLAME BRUSHING ON THE FURNACE WALL TUBES

It is generally called flame brushing that the burner flame touches on the furnace water tubes It has been recognized that the flame brushing is observed as usual phenomenon during boiler operation and it has no troubles against the furnace water tubes as described below

Even if the flame brushing on the furnace water tubes is continuously observed, the metal surface temperature of the furnace water tubes being brushed by the flame is only about 14 ℃ higher than the saturated water temperature inside the tube from actual field tests on several industrial boilers, because they are cooled by water circulation

And even if the carbon adhered by flame brushing, the metal surface temperature of the furnace water tubes at those points will become lower than the ordinal temperature, because the heat transfer become less at those points

The burn out trouble of the water tube is mainly caused by the scale adhesion at the tube inner in consequence of the bed feed water treatment

So, it is important to supply the fuel in stable composition

2-7 LOSS OF UTILITIES

2-7-1 INSTRUMENT AIR FAILURE

If the instrument air pressure is completely lost with failure of the air source facilities for the control and interlock system, the boiler shall be safety tripped

2-7-2 PLANT AIR FAILURE

If the plant air pressure is completely lost with failure of the air source facilities, the boiler shall be operated with instrument air for burner scanner cooling

2-7-3 ELECTRIC POWER FAILURE

In case that entire control power failure happens, the boiler shall be safely tripped

In case electric power failure, continuous operation of Motor driver can't be maintained

2-7-4 UTILITY WATER FAILURE

Sampling cooler cannot be operated without cooling water

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2-8 TABLE OF CAUSE AND EFFECT

Unstable combustion

At the time of ignition a) Too much air quantity b) Sudden increase of combustion rate

(flame is elongated and carbon

is fixed to furnace when it is increased rapidly in spite of low temperature of furnace interior.)

1) Adjust the air quantity by inlet vane of F.D Fan

2) Increase combustion rate gradually

Normal operation a) Erroneous opening of the FD Fan vane damper

b) Inadequate quantity of air

1) Adjust the optimum damper opening during the commissioning test

2) Pay attention to O2meter, and then adjust the air quantity

Generation of black

smoke

a) Inadequate quantity of air (CO gases are generated by Insufficient quantity of air.)

1) Pay attention to O2 meter, and then adjust the air quantity

2) Pay attention to the combustion state

Pulsated combustion

a) Too small quantity of air b) Insufficient draft

1) Change the air quantity

2) Readjust air register damper

3) Investigate the fan

Accidental fire

a) Blockade of burner tip

b) Insufficient air quantity c) Stop of the F.D Fan

1) Inspection of the tip, cleaning if necessary

2) Pay attention to erroneous operation

of air supply system

a) Leakage from piping system

1) Repair the leakage from the piping system even if the leakage is the smallest

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Too high rise of water

level

(the water level has

exceeded the visual

range of water level

gauge)

a) Insufficient operation of feed water flow control valve

b) Sudden increase of load

1) Stop the boiler

2) Shut the register after burner is extinguished

3) After the boiler is stopped, blow the water till it reaches the normal water level by means of blow valve

High water level

(Within the visual

range on the water

to decrease the water level

2) Check and adjust the control valve while using the by pass as necessary

a) Sudden increase of load 1) Reduce the water level somewhat

before the load is increased

2) Increase the combustion rate

3) Never reduce the quantity of feed water

Drop of water level

(outside the visual

range on water level

gauge)

a) Insufficient operation of feed water flow control valve

b) Trouble of feed water process

c) Leakage from piping system

1) Stop the boiler

2) Shut the register after burner is extinguished

3) Feed the water after the boiler is cooled

4) In case of tube breakage, inspect in detail of damage after completely cool down boiler and take a remedy action

Low water level

(within the visual

range on water level

2) Check and adjust the control valve

a) Sudden decrease of load 1) Increase the combustion rate

2) Never rapidly increase the quantity

of feed water

b) After burning 1) Readjust the combustion state not to

cause unburned gas

High draft

a) Incorrect opening of FD FAN

b) Fouling of gas passage 1) Clean out the boiler and ducts

High steam purity

(High conductivity, PH

and/or alkalinity of

boiler water.)

a) Insufficient blow down 1) Adequate regulation of blow down

b) Inadequate utilization of boiler water treating chemicals

1) Check the chemical consumption injected to steam drum and feed water line

Priming or water carry

2) Perform soda boiling

Water carry over

a) High concentration of impurities in drum water

b) Too high water level c) Sudden change of the load d) Sudden change of steam pressure

e) Overload

1) Increase blow down quantity

2) Investigation of feed water control system

3) Investigation of quantity of boiler water treating chemicals

4) Pay attention to the load

2-2-4 AUTOMATIC COMBUSTION CONTROL

2-6-2 PREVENTION OF UNBURNED FUEL ENTERING

2-6-3 TROUBLE OF BURNER

2-6-4 MISFIRE OF THE GAS IGNITOR

2-6-5 POOR BURNING OF THE GAS BURNER

2-6-6 PULSATION OF GAS FLAME

2-6-7 FLAME BRUSHING OF THE FURNACE WALL TUBES

c) Scale on the interior of the tubes

a) Dissolved oxygen in boiler water

1) Inspect in detail of damage after completely cool down boiler

2) Examine the progress of pitting and corrosion

3) Take a remedy action according to the detail procedure in the operation

& maintenance manual

4) Do not forget soda boiling and hydrostatic test in tube replacing

1) Repair as soon as possible

2) In case bricks in the furnace are removed or dropped, shut down the boiler immediately and repair them 3) Avoid sudden rise of the load

4) Avoid sudden cooling

Since the equipment is going to be stored on-site in the condition it left the shop, there is

no reason to drain the modules The modules have been air dried and have been purged

of moisture There will also be a slight residual of oil on the inside and outside heating surfaces which protects from corrosion

3-1-2 NITROGEN PURGE

The steam-side of the exchanger and tubes have been protected with a nitrogen purge which will not dry out the inside of the equipment, but is designed to eliminate oxygen and, therefore, the resulting corrosion The protected coils and steam-side space of the exchanger require a nitrogen pressure of between 4.5-5.0psig(0.32-0.35 kg/cm2g) A pressure gauge at the bottom of these areas has been attached in the shop for pressure verification If nitrogen pressure starts receding below 4.5 psig (0.32 kg/cm2g), additional nitrogen must be added to maintain pressure If all nitrogen has been lost, the unit must be refried and purged to the correct pressure rating Nitrogen pressure should be monitored weekly in order to prevent loss of the purge on this equipment

3-1-3 VAPOR CAPSULES

The gas-side of the exchanger and boiler the steam-side of the boiler and the steam drum contains Zerust Vapor Capsules The Vapor Capsule emits a vapor which is diffused within the atmosphere of the protected space and attaches to all metal surfaces which passives the metal against airborne corrosion These areas will require maintenance, since the vapor dissipates over time The equipment must be opened and inspected at least once every six months and the capsules changed

If the boiler is inside there is still a possibility of freezing if the outside ambient temperature

goes below freezing

If a boiler is going to be shutdown for less than two days, DRB recommends that it be

“bottled up”

This wet storage involves injecting slightly higher doses of chemicals just before shutdown and closing all valves as the heat is removed Depending on job specific conditions, the pressure will remain in the boiler for quite a long time

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3-2-2 PROCEDURE

Prior to shutting down the boiler, blow down the lower drum until the water is clean

If the water is free of solids, there is no need to drain the boiler

1) Close the non-return valve and all boiler drains

2) Open the boiler drum vent

3) Fill boiler with water to overflowing Demineralized water is recommended Since there will

be little or no head imposed on the feedwater by the boiler system, the feedwater control valve bypass should be used while filling

4) Manually close the feedwater control valve and throttle the bypass valve to protected

CAUTION : All chemicals must be added in a diluted liquid form Concentrated chemicals or

soil chemicals should never be introduced into the system

5) After the chemicals have been added, the water must be circulated by one of the following methods :

▣ Lower the drum water level to centerline and open the steam drum vent valves

Introduce saturated steam through inner coil tube in water drum Circulated the boiler by this method for approximately 2 hours

OR

▣ Circulate the drum water from the feedwater connection back to the intermittent blowdown with an external pump Recalculate the boiler water for approximately two (2) hours with the boiler and economizer full and all vents closed

6) The nitrogen is supplied from nitrogen header instead of nitrogen bottle with pressure regulator The supply pressure is 7barg

7) Test the boiler water once each week by taking a sample form the continuous blowdown line Add chemicals through the chemical feed connection as necessary

In case the system has been drained, the chemicals may be added as the boiler is refilled Solutions of these chemicals must be added slowly so that they are dilute as water is being added

If chemicals are added, recirculation will be necessary

4 INSPECTION

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4-1 EXTERNAL INSPECTION OF BOILER

After the boiler has been shut down and the furnace has been cooled sufficiently, be sure to inspect the exterior of boiler proper, water-cooled wall and economizer At the same time, inspect boiler supports

Those tubes facing the furnace should be cleaned quite carefully and checked for corrosion, deformation, bulging, burning and cracking External fouling (slugging) cannot be entirely avoided

However, it should be kept to a minimum Especially local accumulations should be avoided Heavy accumulations of slag (greater than 1/8" thick) can be removed by reducing the firing rate and allowing the ash deposit to burn off

If necessary, the fire sides should be water washed during outages

4-2 INTERNAL INSPECTION OF BOILER

Boiler interior should be examined at each time of periodical inspection The particulars there of will be described in the following :

(1) Internal inspection of boiler drum

Take off the manhole cover and check whether boiler drum internals are fixed securely and not contaminated

Before entering into the boiler drum, confirm the following, that is, the steam stop valve, feed water valve, chemicals injection valve and continuous blowdown valve are closed firmly Further, provide them with appropriate marks so that other persons will not open them inadvertently

Upon entering into the boiler drum check for corrosion and pitting The most common type of corrosion occurring inside the boiler drum is "pitting" due to dissolved oxygen, Such pitting generally occurs at both lower ends of the water drum where sludge is staying, but it can be found at other positions, too

However, if the properties of boiler water during wet lay-up of the boiler are appropriate, pitting will scarcely occur the steam drum Further, incases where the water tube is expanded to the drum, one may often find pitting in the expanded water tube part of the water drum and therefore, the said part should be inspected carefully Pitting occurs frequently in boiler bank tube group up to the 10th row from the down comer tube side, against which due cautions should be taken

However, there is little change of occurrence of pitting in the water-cooled wall tubes, even when they are expanded to a header, if the boiler is run continuously

Normally the holes made by pitting are covered with dark red oxide, below which black openings are existing

As the main cause there of is dissolved oxygen existing in feed water, it can be completely prevented if feed water and boiler water control is carried out rationally Bear this fully in mind

(2) Internal inspection of water tube

Carefully check up the interior of upper and lower drums and the condition of deposits

at the tube end To eliminate the deposits, fully wash the drums and tubes In respect

of the water-cooled furnace wall tubes, once per about 3 years, to fully check up the condition of scales, cut off a part of tube which is subjected to the highest thermal load as a sample tube and check up deposits of scale, and make analysis of the scale for use as the data for chemical cleaning

When mounting the internals, pay attention to the following :

1) Fully understand beforehand the manner of assembling and the shaper of internals

2) As the internals are divided in a large number of parts, it is advantageous to assort them into those being to be mounted above water level and those being to be mounted below water level to avoid mistake

3) At the time of mounting, fully inspect the parts to assure that there is no possibility of steam -water mixture, dry steam feed water, etc leaking form joints and being mixed with each other

4) In particular, the portion near the dry steam outlet should be completely tight

5) When new packings have been inserted in bolted joints, the bolts should be retightened after preliminary tightening

6) Joints not using any packing should be well fitted each other proper to tightening the bolts

The internals should be fully inspected also in the course of their assembling After completion of mounting, it is impossible to check them up in every nook and corner

4-3 OTHER INSPECTION

Inspect and clean the gas side of boiler heating surface and the furnace wall

At the time annual inspection, perform the following completely :

(1) Complete inspection of boiler interior (2) Elimination of scale form boiler proper and water-cooled wall tubes

(3) Checking furnace wall for cracking and peeling-off

If water washing is employed to clean the unit, make sure electrical equipment and local panels are protected form direct water splashing

All inspection should be made by competent persons who are qualified to pass judgement on scale conditions, etc

A record of each inspection should be kept in a uniform manner so that results of any change can be compared with former conditions Inspections of tubes, as a result of tube failures or conditions expected to lead to failures, should be even more thorough,

if the cause of the conditions is not obvious or cannot be determined clearly, such inspections should include metallurgical examinations of tube sections, chemical analysis of deposits, etc

1) Cut off the tube with the acetylene torch at both drum ends

2) Sufficiently heat the tube inside surface with the heating torch (about 600℃-800 ℃ )

3) After heating, immediately cool the tube inside with water, Repeat these step until

a clearance is made between the tube and the drum plate

4) Strike the tube tip with a hammer till the tube comes out

5) In case of the groove being on the inside surface of the drum tube holes, it will be necessary to gouge the tube inside with gouging tool

For inaccessible tubes that cannot be cut close to the drums, the procedure is similar except that the slots must be cut, and that tube ends come out the boiler drums,

Remove as much grease and oil as possible form the inside of the tube by running swabs soaked in kerosene through the tube if possible Then clean the outside surface

of the tube ends with emery cloth and wipe off with a solvent such as Varsol, Stoddard Solvent or Safety Naphtha

Competent persons should do the rolling of expanding of tubes

Proper rolling of tubes is very important The tube should be expanded and flared with the proper expanding equipment See that the expander is equipped with the proper rollers The tubes should be expanded only enough to make them tight Overolling may make it necessary to replace the tube

Care must be taken that the tube hole is completely filled and that the tube is not rolled too thin

If the hole is not completely filled the contact will be weak and there is a big chance of corrosion on the fireside If the tube is rolled too thin, a groove will be cut in the tube at the outer side of the wall

Tubes can be rolled by hand with a ratchet wrench or by using a reversible air motor

In cases when only a portion of a tube is replaced, it may be necessary to touch up one

of other rolled joints it the application of heat for the replaced tube hole has been close enough to loosen it it may be advisable to include such a joint in the replacement section ; if so make up the rolled joint last

(3) Tube Repairs

Replacing just the damaged section rather than the entire tube can in most cases repair

a tube which has failed or which is in danger of failure After removing the furnace wall insulation behind the effected area, the tube section can be removed by cutting Proper techniques should be used when re welding a new tube section, especially when the wall is fin or tangent welded

Competent and qualified persons should do all repairs All welding should be in accordance with the Recommended Rules for Repairs of Power Boilers by the National Board of Boiler and Pressure Vessel Inspectors

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5-2 TABLE OF MAINTENANCE SERVICES

(Periodic maintenance services)

Intermittent blow off when boiler load is not very high or when it has become stable

leakage

1 Repair leaking part immediately

2 Drainage in air piping

Operation recording Make a recording at least once

every hour during use

1) Pressure Drum Main steam, Feed water, Fuel etc 2) Temperature

Feed water, Combustion air and Flue gas etc

3) Level Steam drum

4) Draft F.D fan outlet air, wind box and Furnace 5) Flow rate

Feed water, Main steam and Fuel 6) Other

Conductivity of feed water and boiler water

O2 % of flue gas

Press and temp of Aux Equipment

Check the shapes of valves

1) Check leakage of valve

2) Lubricate the rotational parts

Manhole of drum

casing etc

Check whether nuts are tightened

1) Tighten them if loose

2) Change packing in case of leakage 3) Pay attention to the lid and the contact with seat

Boiler inside Check whether tools and rag

1) Clean

Refractory material Check for breaking, bulge

cracks as well as texture

1) Repair

2) Record and investigate for the next

Boiler tube water-

cooled wall tube Check for bulge, blow, soil

1) Repair or replace, if necessary

2) Investigate the cause bulge

3) Do not forget soda boiling and hydrostatic test in replacing a tube

pressure rise

1) Repair a part of unsatisfactory air tightness during off period

Before

each use

Water level gauge Check whether it works 1) Check the readings

others

Burner and throat

Check the movement air register dampers

Check for cracks and soil of throat part

Check the position of diffuser and register

1) Clean the Burner

2) Replace with spare, if necessary

3) Clean the throat part

4) When the damper is hard, remove impurities

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Boiler tube and

1) Check the part inserted into the drum especially

2) Clean around the part inserted into the drum well

leakage

1) Treat corroded part and paint

2) Give air tightness test and repair leaking part

Boiler tube Inspect interiors sufficiently

1) Examine the progress of pitting and corrosion for the next opportunity 2) Do not forget soda boiling and hydrostatic test in tube replacing

* Primary resister damper and secondary resister vane

1) Treat pitted part

2) Examine cracks, if any, and replace

Check for any abnormality

Make sure that they do not leak and that they operate smoothly

1) Replace with new ones, if necessary 2) Tighten both etc., if loosen

corrosion and leakage

1) Treat corroded part and paint

2) Repair leaking part

Monthly Safety valve

Check the conditions of valve, valve seat and spring.

Give tension test to spring

After overhaul, assemble

1) Lapping

2) Lubricate witching device

3) Replace packing of leaking part

Pressure part Check the external and the

internal surface

1) In case of corrosion or pitting etc., investigate causes and replace with new one, if necessary

Instruments and

A.C.C

Check pressure gauge thermometer, flow meter, o2 meter etc

instruments

2) Repair if error is large

3) Clean and lubricate lapping part, if necessary

1) Check the opening diameter

Replace and record, if worn seriously

interiors,

1) Check for corrosion and pitting

2) Clean and paint, if necessary

DINH VU POLYESTER PLANT PROJECT

STEAM BOILER PACKAGE

PIPING AND INSTRUMENTS

DIAGRAM FOR AUXILIARY BOILER