UG－487/13.7－M Boiler Operation Manual 330B－SM8 Written by Checked by Examined by Approved by Standards WUXI HUAGUANG BOILER CO.LTD People’s Republic of China (WUXI BOILER WORKS) 330B-SM8 Boiler Operation Manual Page 1 of 46 August 2009 CONTENTS 0. Preface................................................................................................................................... 3 1. Preparation before Boiler Startup.......................................................................................... 3 1.1 Refractory Curing................................................................................................................ 3 1.2 Boiler Chemical Cleaning ................................................................................................... 7 1.3 Cold Aerodynamic Field Test .............................................................................................. 7 2. Boiler startup and operation .................................................................................................. 9 2.1 Cold Start ............................................................................................................................ 9 2.2 Warm Start (bed temperature>500℃, without coal feeding) ............................................ 17 2.3 Hot Start ............................................................................................................................ 20 3. Normal Operation ............................................................................................................... 20 3.1 Check Up During the Boiler Operation............................................................................. 20 3.2 The load Adjustment ......................................................................................................... 21 3.3 Water Level Adjustment .................................................................................................... 23 3.4 The Bed Temperature Adjustment ..................................................................................... 23 3.5 The Steam Pressure Adjustment ........................................................................................ 24 3.6 The steam temperature adjustment .................................................................................... 24 3.7 Steam Quality Control and Adjustment ............................................................................ 25 3.8 Air Distribution Control .................................................................................................... 25 3.9 Emission control of NOx and SO2.................................................................................... 26 3.10 Boiler Soot Blow ............................................................................................................. 26 3.11 Miscellaneous .................................................................................................................. 26 3.12 DCS Automation ............................................................................................................. 27 4. Boiler shut-down ................................................................................................................. 29 4.1 The scheduled shutdown of the boiler to cold state .......................................................... 30 4.2 Shutdown of the boiler to hot standby .............................................................................. 31 4.3 The emergency shutdown.................................................................................................. 31 4.4 The fast cooling down of the boiler after the shutdown .................................................... 32 5. The precautions ................................................................................................................... 33 6．The protection during the shutdown of the boiler ............................................................. 37 6.1 The Nitrogen Blanket ........................................................................................................ 37 6.2 The curing method through water release and drying under hot state............................... 37 6.3 The anti-corrosion under pressure filling for boiler .......................................................... 38 6.4 Anti-frozen Methods ......................................................................................................... 38 7. The trouble shootings .......................................................................................................... 39 7.1 The too high or too low bed temperature .......................................................................... 39 7.2 The bed pressure is high or low ........................................................................................ 39 7.3 The water wall tube bursts ................................................................................................ 40 7.4 The superheater tube burst ................................................................................................ 41 7.5 Agglomeration formation on the bed ................................................................................ 42 330B-SM8 Boiler Operation Manual Page 2 of 46 7.6 The firing inside the flue gas duct ..................................................................................... 42 7.7 The feed water shortage .................................................................................................... 43 7.8 The overflow of the drum.................................................................................................. 44 7.9 The water impact on the piping ......................................................................................... 44 7.10 The Stoppage of the fuel supply ...................................................................................... 44 7.11 The main fuel trip MFT ................................................................................................... 45 7.12 Attentions shall be taken for boiler overhaul................................................................... 47 330B-SM8 Boiler Operation Manual Page 3 of 46 0. Preface The super high pressure boiler is designed and manufactured by Wuxi Huaguang Boiler Co., Ltd (WHBC) according to WHBC’s experiences in designing and manufacturing of the Circulating Fluidized Bed Boiler. This boiler specification is made in accordance with the boiler design characteristics. The purpose of this boiler specification is to introduce the boiler operation requirements and the points where attention shall be paid to. The boiler start up and shutdown process are closely related to the other equipments of the plants, like steam turbine, auxiliary equipment and control system, this boiler specification can be applied for reference by the owner during making relative operation specification and during startup and commissioning. 1. Preparation before Boiler Startup Besides the commissioning of each boiler parts, following procedures shall be finished before whole boiler commissioning: boiler washing ， boiler refractory material curing, chemical boiling, steam-line blowing, boiler ignition test, boiler safety valve commissioning, interlock protection test for auxiliary equipment, boiler main protection test, cold aerodynamic field test etc. Processes for boiler dry-out and aerodynamic field test are expounded in this specification. 1.1 Refractory Curing Refractory curing process is applied before boiler commercial operation, the purpose is to dry out the refractory and insulation lining inside the boiler wall. Normally, the boiler drying-out process takes 120～150 hours. The newly built boiler lining contains certain amount of moisture, for which a slowly drying process is required. Otherwise the moisture evaporating may cause the refractory lining expansion, generate certain pressure, and result in flaking and spalling. Refractory curing process will speedup the chemical and physical change of the lining, increase 330B-SM8 Boiler Operation Manual Page 4 of 46 its strength, and guarantee a long service life under high temperature. Therefore, the boiler drying-out process shall be made carefully according to relative requirements before the boiler operation. This specification is provided only for reference. ♦ Refractory lining are mainly applied to locations like furnace, cyclone separator, material return device, inlet and outlet flue gas ducts, low temperature economizer casing and startup burner, etc. ♦ The method for refractory curing, as well as drying-out curve shall be made by the joint agreement between the manufacturer, client and commissioning company. ♦ On the material return leg, loop seal, outlet duct of the cyclone separator, a φ6～φ8 steam exhaust hole shall be made in every 500mm for discharging the moisture of the refractory lining, these holes shall be seal welded after drying-out of the boiler. ♦ Sampling points shall be made on the material return device and outlet duct of the cyclone separator to measure the water content and to estimate the effect of the boiler drying-out. ♦ Generally, special drying-out burner shall be applied as the heat source for boiler drying-out, and the heat-up device may used at the same time to achieve certain effect. At the initial stage, fire wood is also applicable for dry-out. 1.1.1 Preparation and Necessary Requirement before Refractory Curing ♦ After installation of the boiler proper, material return system and duct and flue system, completion of the air leakage and air pressure test, and completion of boiler insulation, all holes and doors shall be opened and naturally dried for over 72 hours. ♦ After the inspection inside the furnace, duct and flue, cyclone separator, loop seal, air preheater and dust catcher. ♦ Boiler expansion indicators are completely installed, the index are adjusted to “0”position. ♦ Oil system, after installation, qualified in hydraulic test and commissioning, ready to supplied oil to boiler. 330B-SM8 Boiler Operation Manual Page 5 of 46 ♦ Thermodynamic instruments: The installation and commissioning are complete; calibration is finished, and ready to be put into use. ♦ The installation of the drum internal is finished, the water lever indication is distinct and correct, with good illumination condition. ♦ Soft water or chemical demineralized water shall be filled into normal level, the water temperature shall be 40～60℃, the difference between water temperature and drum metal temperature shall not exceed 50℃,and the water level gauge shall be cleaned. ♦ Sampling points for refractory lining shall be made on the outlet ducts of the furnace, material return device and cyclone separator. 1.1.2 Refractory Curing Process Refractory curing will be started after the refractory lining and 72 hours’ natural drying. Refractory curing contains three steps: low temperature curing by under bed igniter, low temperature curing for whole boiler and high temperature curing. 1.1.2.1 Low Temperature Curing by Under Bed Igniter The under bed igniting chamber and flue gas mixing chamber is lined by refractory bricks and insulation bricks. The thermal load in these areas is relatively high and the temperature increasing speed is hard to be controlled, and the thermal shock to the opposite wall is relatively large. In case there is some moisture between the bricks, and the temperature is increased very quickly, the brick will be easy to be fall off. Therefore, before the startup burners are applied for boiler drying， fire wood shall be used for curing of the refractory and insulation material of the under bed ignition burner, the temperature is 300℃ (air chamber temperature). ♦ The flame shall be controlled, and the initial temperature shall be 100℃. ♦ Then the temperature shall be increased, after 2 hours, the temperature shall be 160℃, and be held for 6 hours. ♦ Increase the temperature by a speed of 30℃/hour to 300℃，and be kept for 10 hours. 330B-SM8 Boiler Operation Manual Page 6 of 46 1.1.2.2 Low Temperature Curing (300～350℃)（temperature at the outlet of the ～ ℃（ cyclone separator） ） ♦ No bed material to be filled into the furnace. ♦ On the outlet of the cyclone separator, a partition wall, partially block the duct shall be made to lead the flue gas from the material return system to the outlet of the cyclone separator. ♦ During the startup of lancer of the under bed igniting burner, the first under bed startup burner shall be started under lowest combustion rate, and the No.2,3&4 under bed igniting burners shall be started in every other 30 min by proper order and steadily operating for 3 hours. ♦ For nozzle protection, the mixed air flow of the burner shall be controlled to make sure the temperature of water cooled air chamber less than 900℃. ♦ The temperature of the cyclone outlets shall be increased by a speed of 28℃/h, when the drum pressure increased to 1MPa, ♦ The temperature shall be increase with a speed of 28℃/h, when the drum pressure reaches 4.15MPa, the lance shall be put into use with MAXIMUM combustion rate, and steadily operated for 24 hours. The inlet temperature of the cyclone separator shall be about 300℃. ♦ For the operation of the steam/water system, operation of the PC boiler with same capacity could be referred. ♦ Remove the temporary partition wall after the boiler curing is finished. 1.1.2.3 High Temperature Curing of the Whole Boiler ♦ Bed material shall be filled with a thickness of 700mm. the under bed burner shall be started, and the bed material fluidization shall be maintained. The temperature increase speed of the flue gas at the outlet of the furnace shall be controlled to ensure it not exceed 28℃/h. the temperature shall be maintained to be 500℃ and hold for 24 hours. The over bed oil lance can be applied when the temperature cannot reach 500℃. ♦ The curing shall be restarted no matter the curing process is interrupted by what reason. ♦ The requirements of the refractory anti-erosion material of the manufacturer 330B-SM8 Boiler Operation Manual Page 7 of 46 on sampling water content must be satisfied, the curing can be considered to be completed after the test is qualified. ♦ For material return device, it is necessary to make further boiler curing during first time of ignition, the return material temperature shall be controlled to be about 500℃(by periodical coal feeding), the boiler start up period shall be prolonged for curing of the refractory lining in the material return device. When there is no steam come out of the steam exhausting holes on the material return device, the curing can be considered to be completed. The above-mentioned curing works can be made by the professional curing company. 1.2 Boiler Chemical Cleaning For the chemical cleaning, the CFB boiler applies same way with the PC boiler. Special attention shall be paid to the protection of the high pressure valves. the materials applied for manufacturing of the superheater are: SA-210A1 （SA-106B） SA-213T12 、 （SA-335912） SA-213T22 、 （SA-335P22） SA-213T91 and （SA-335P91）. The materials applied for manufacturing the reheater are: SA-210A1（SA-106B） 、 SA-213T12、SA-213T22 and SA-213T91（SA-335P91） 1.3 Cold Aerodynamic Field Test 1.3.1 Purpose The purpose of the test is to measure the pressure loss of empty bed and the bed with solids, to find the critical fluidized air flow and provide reference information to the boiler hot state operation; to guarantee the safety combustion of the boiler and to prevent the agglomeration building on the grid, and to guarantee a stable steam pressure. 330B-SM8 Boiler Operation Manual Page 8 of 46 1.3.2 Test and the Method ♦ Calibration of the air flow inside the main air ducts of the primary and secondary air The air flow velocity is a key factor in determining the fluidization quality; therefore the calibration of the primary air flow is very important for CFB boiler. ♦ pressure loss of the empty bed The induced fan and the primary air fan shall be started without any bed material on the grid, then regulate the primary air flow and record the pressure on the grid, and the curve indicted the relationship between gird pressure loss and air flow shall be made based on the data recorded. ♦ Test on relationship between the thickness of the bed material layer and the bed pressure With certain air flow (generally, air flow for operation will be selected), the stationary thickness of the bed shall be of 700mm, 800mm, 900mm , 1000mm,and 1100mm, the bed pressure shall be recorded, and the recorded data shall be the basis for making the curves that indicate the thickness of the bed material and the bed pressure. Test for critical fluidized air flow The critical fluidized air flow is the minimum fluidized air flow during boiler operation especially during boiler part load, if the air flow is lower this value, the agglomeration may happen. For measuring the critical fluidized air flow, the stationary bed material layer thickness shall be 900mm. ♦ Test for the fluidization quality Stop air supply during fluidized condition, and people shall be sent inside the boiler to see the distribution of the bed material, and the fluidization condition can be determined by the flatness and evenly distribution of the bed material, in case the bed material distribution is uneven, the reason shall be detected and relative measures shall be taken to ensure the good fluidization condition. 330B-SM8 Boiler Operation Manual Page 9 of 46 2. Boiler startup and operation 2.1 Cold Start ♦ With large amount of refractory lining, especially in return leg, loop seal and outlet flue gas duct, the boiler startup speed is limited due to the requirements of the lining for temperature increase speed. The flue gas temperature increase speed is one of the key facts for thermal stress, and a reasonable startup process could prevent the excessive thermal stress. Normally the manufacturer’s allowable maximum temperature shift rate is ±80℃/h， therefore the temperature shift during operation shall not exceed 80℃/h during operation. ♦ During the boiler startup, due to the minimum primary air flow required for bed material fluidization and the air flow for burners, the excess air flow is relatively higher. ♦ Oil flow for the under bed igniting burners are 4×1000kg/h, and oil flow for the over bed igniting burners are 4×1200Kg/h. when the bed temperature maintains to be 550℃, coal feeding shall be started with first coal feeder on minimum operating speed. After coal is ignited (judged according to the bed temperature increase speed and change of the quantity of the oxygen), other coal feeders can be started to increase the combustion rate. ♦ The air flow of the under bed igniter is 30Nm3 air for 1kg oil, and make sure the flue gas temperature enters into water cooled air chamber not exceed 900℃. 2.1.1 Preparation before Boiler Igniting The ignition startup of the boiler can only be started after the completion of the followings: ♦ The drying out of the boiler is complete ♦ The boiling of the boiler is complete ♦ The flushing & cleaning of the piping is complete ♦ The steam blowing of the piping is complete 330B-SM8 Boiler Operation Manual Page 10 of 46 ♦ The steam sealing property testing is complete ♦ The Safety valve calibration work is complete. ♦ All the temporary facilities are removed thoroughly ♦ The hydrostatic testing has passed ♦ All the boiler proper equipment has been inspected and is under working condition, the flue gas duct is through and no people are staying inside the furnace and the erection tooling and affiliated items are completely removed from the furnace. ♦ All the auxiliary equipment is under working condition and the operators understand the operation procedures of the same. ♦ Check the water level gauge installation as per the drawings provided by the manufacturer. ♦ All the steam exhaust piping, drains piping, pressure release piping, safety valve piping, instruments cleaning pipes should be easy accessed and correctly and properly connected to the blow down system or other piping. ♦ All the thermodynamic and auto controlled instruments are calibrated with the specified and correct measuring precision. The control interlock system is under working condition. ♦ All the manholes, man doors, peep holes are closed. ♦ All the equipment related to the thermal expansion should be removed, like temporary frame used for erection, ladders, etc. ♦ The peep hole of the oil burner and the flame detector must be fully cleaned by using the cleaning air. ♦ The atomizer nozzles of the startup burner should be inspected to ensure that there is no chock. ♦ The fuel feeding system is under working condition and the no load operation of the same for 15 to 20 minutes should be carried out to test the functioning conditions of the same. 330B-SM8 Boiler Operation Manual Page 11 of 46 2.1.1.2 Water Filling The water filling could only be started when the water is qualified. The quality of the feed water shall be in accordance with the GB/T12145-1999 “thermal power unit and steam power equipment steam-water quality”. The water intake temperature shall be 40-60°C, and the drum wall temperature shall be controlled to be less than 35 °C. in case the water intake temperature higher than the wall temperature in more than 50°C the feed water flow shall be controlled to be 20-40 t/h, and the upper and lower wall temperature shall be ≯40°C , record the upper and lower wall temperature each 30min after the in taking of the water. ♦ Open the drum air release valves ♦ Close all the drain valves at the water side ♦ Open all the superheater air release valves ♦ Open superheater drain valves and the drain valves of the main steam piping ♦ Open boiler feed water bypass valves and manually control the feed water device to control it to be 10% to 15% of the feed water volume ♦ Open the economizer air release valves and close the same when the air is released. ♦ Fill the water to the minimum water level of the drum （50mm under the normal water level ） ♦ Manually close the attemperator ♦ Confirm that the recirculation stop valve between the drum and the inlet of the economizer is at the open position. ♦ Water filling time: no less than 2 hours in summer, and no less than 4 hours in winter ♦ The water level shall be checked after filling, in case of any change, the feed water valve shall be checked for leakage 2.1.1.3 Boiler Heat-up 330B-SM8 Boiler Operation Manual Page 12 of 46 Boiler heating up device is installed on the water wall lower header; the steam for heating is the low pressure and middle pressure steam from the neighboring boiler. With the boiler heat-up device, the time for steam generating and circulation start could be saved; therefore the startup time could also be saved. The heat-up device could also be applied for anti-frozen protection during boiler shutdown in winter time. After the water filling, the heat up device shall be started. For start the heat up device, the drain valve of the heating distributing header shall be started for draining and heating, when the heating is finished, the draining valve shall be closed and slowly open the steam heating valve of each lower header, and open the side air damper. When the pressure reaches certain value, the air damper shall be closed and open the drain valve damper of the superheater for draining and heating. During boiler heat up, the attention shall be paid to the following matters: ♦ The heat up shall be made slowly, and the boiler water saturated temperature increase speed shall be 28～56℃/h, the drum wall temperature shall be strictly controlled, during temperature increase, the maximum temperature difference on the drum wall shall not exceed 40℃. ♦ During the time of heat-up the water level of the boiler keeps rising, and high water level of +150～+200mm could be maintained at this time. When the metal temperature of the drum wall reaches100℃, the emergency drain valve could be applied for water discharge (in case of periodically discharge, the heating shall be stopped), to maintain the water level in the normal range. ♦ Before and after heating, the expansion indication shall be recorded: make sure the expansion of different parts are even, in case of abnormal condition, the temperature increase speed shall be decreased and heating at the bottom of the boiler shall be stopped, after the reason of abnormal is detected, the heating can be started again. ♦ Ventilation is prohibited during heating up. 2.1.1.4 The Startup of the Air Fans The startup sequence of the air fans is: ID fan ---- High Pressure Fan --- SA fan --PA fan 330B-SM8 Boiler Operation Manual Page 13 of 46 The startup of the ID fan ♦ During the startup of the boiler, the ID fan is the first fan to be started in the circulation fluidization system and the flue gas system. But before the startup of the ID fan be sure that its inlet baffle plate is adjusted at the MINIMUM position to avoid the motor over current during the startup period. After the startup of the ID fan the bearing vibration indicator should be monitored to ensure that the voltage and the current values are within the specified range. ♦ During boiler operation, In case the ID fan trips or stops caused by any reason, the PA fan, SA fan and the fuel feeding system should be interlock and stopped. Startup of HP Fluidizing Air Fan ♦ After the ID fan is properly started, the HP air fan should be started and check the air flow of different chambers of the loop seal. During the normal operation the HP air should be continuously flow to the sealing device. The operator should monitor the temperature of the seal leg to ensure that the suitable circulating flow to the combustion chamber. The HP air fan is of quantitative type, which will guarantee enough air quantity, and the rest air will be sent to the primary air duct through bypass. Startup of the SA fan ♦ The SA fan shall be stared after the startup of the high pressure fluidizing fan. Before the startup of the SA fan, make sure the inlet damper of SA is in close condition to prevent the motor from over load. The SA can be applied for cooling of the over bed burners, that’s why the SA shall be started before the PA fan. Startup of the PA fan ♦ The PA fan shall be started after the startup of the ID fan, HP fan and SA fan. Before startup of the PA fan, the inlet damper, and the PA duct damper and the dampers for the air ducts of the startup igniting burners shall be adjusted 330B-SM8 Boiler Operation Manual Page 14 of 46 to the MINIMUM position. ♦ After the operation of the PA fan, the inlet guide vane control damper shall be slowly opened, and pressure of the furnace shall be monitored. 2.1.1.5 Feeding of the Bed Material ♦ In case the furnace is empty before the startup of the boiler, a certain quantity bed material can be fed to the furnace with the precondition that the air fans are put into use. The bed material applied is furnace slag with the carbon content of less than 3% and the particle size of 0~5mm. with the operation of the fans, the bed materials will be evenly distributed on the grid, the thickness of the material layer ≧800mm. ♦ Check the bed pressure indicated to determine the bed material accumulated on the grid, and the bed pressure shall be recorded. The bed pressure will increase as increase of the bed material. 2.1.1.6 Air Cleaning ♦ Adjust the PA flow to maintain it at 30% ( set the PA control at manual position ) ♦ Open the oil burner damper. ♦ Clean the oil burners 2.1.2 Oil ♦ The PA flow shall be controlled to reache 30% of the total air flow ♦ Oil burner air flow control shall be adjusted to AUTO position ♦ The furnace pressure control set to AUTO ♦ SA damper be closed on “AUTO” mode ♦ Close the PA damper ♦ The opening of combustion air dampers for under bed burner shall be maintained to be 30%. ♦ Start the No.1 under bed startup oil burner till it burns steadily and the air supply to the oil burner shall be set at AUTO mode. ♦ The oil supply of the oil burner shall be adjusted to the lowest value ( the oil 330B-SM8 Boiler Operation Manual Page 15 of 46 pressure should be larger than the lowest oil pressure ) ♦ Set the bed temperature increasing speed at 80 ℃ /h ( as per the requirement of the refractory material supplier ) ♦ Start the No.2, No.3 and No.4 oil burners one by one in proper order after 15 minutes of the ignition of the No.1 oil burner and increase the oil supply based on the liner temperature increasing function curve. ♦ The air flow supplied to the burners shall be controlled, make sure the flue gas temperature at the outlet of the mixing chamber not exceed 900℃ to prevent the grid nozzle from been burnt out. ♦ To monitor the expansion situation of the drum, headers during the startup period and periodically monitor the expansion indicator and record the displacement value. ♦ If the bed pressure decreased to a value lower than the value of the initial record, the bed material feeding shall be started again. ♦ When the steam pressure reaches 0.1 MPa, close the air release valves of the drum and the superheaters. ♦ When the steam pressure reaches 0.15 ~ 0.2 MPa flush the pressure gauge and cross check with the neighboring pressure gauge to ensure that the readings are accurate. ♦ When the drum pressure reaches 0.3Mpa and the superheater temperature is higher than the saturated steam temperature and then open the motorized valve to 20% opening. ♦ When the steam pressure rise to 0.3Mpa ~ 0.5 Mpa, periodical blow down shall be applied to water wall lower headers. Inspect the blow down valve for flexible operation and leakage. During the process of blow down make sure that the drum water level should not be lower than the minimum level. Otherwise the makeup water should be filled to the drum. ♦ Close the superheater drain valves. ♦ Adjust the steam release to air valve to maintain that the outlet steam temperature of the superheater is at least 15 ℃ more than the saturated steam temperature and the steam flow should be more than 10% to cool the superheater. 330B-SM8 Boiler Operation Manual Page 16 of 46 ♦ Adjust the steam release to air valve to ensure that the temperature difference of the upper and lower wall not exceed 50℃and the drum water temperature increasing speed is around 1℃ per minute. ♦ When the steam reaches the requirement of the turbine and then supplies the same to the turbine. 2.1.3 Coal Feeding ♦ Ensure that the coal handling system is functioning properly. ♦ Ensure that the coal delivered to the front of the boiler is of qualified particle size. ♦ When the bed temperature is more than 550 ℃ (this is the recommended data and the actual value shall be determined during the commissioning) and then the coal maybe fed into the furnace. ♦ Keep the coal feeder control at the manual operation position. ♦ Open coal bunker gate valve and isolation valve. ♦ Seal air for coal feeder and isolation gate valve shall be started. ♦ During the operation of over bed igniting burners, No.1 and No.6 coal feeders shall be started (under minimum speed); the coal feeding shall be made in each 90 seconds, with 3 times of impulse coal feeding. The No.1 and No.6 coal feeders are installed close to both of the side walls, the volatile and fine coal particle of the coal are easy to be ignited by the flame of the over bed igniting burners, and the bed temperature can be increased by combustion of the coal volatile and fine coal particles. ♦ The ignition condition can be judged according the bed temperature increasing speed (more than 5℃ ), oxygen flow and irradiancy of the coal particles. ♦ After the confirmation of the ignition of the coal keep the coal feeder to be operated under the lowest RPM. ♦ Open No.2, 3, 4, 5 isolation gate valves. ♦ Put No.2, 3, 4, 5 feeders into operation under the lower RPM. ♦ The output of the under bed oil burners could be reduced according to the actual requirements, and the RPM of the coal feeders shall be increased. ♦ Check the bed temperature increasing speed, and further increase the coal feeding. 330B-SM8 Boiler Operation Manual Page 17 of 46 ♦ (Manually) start the limestone feeding function group, and the output of the limestone feeding shall be adjusted to 10%. ♦ With the minimum load, when the bed temperature is higher than 780℃, the oil supply can be gradually decreased, and the 2 over bed igniting burners can be shutdown, while the coal feeding can be increased to ensure the increase of the load. ♦ When the oil burners are shutdown, the PA damper shall be slowly opened. ♦ Under the precondition of maintain the bed temperature, the other 2 over bed oil burners shall be shutdown, while the coal feeding can be increased to ensure the increase of the load. ♦ Follow the specified curve to increase the PA flow along with the boiler load increasing. ♦ If the set values for the main steam pressure and temperature have been reached and then function the load control and the fuel feeding control. ♦ Changeover the control of the feeding of the lime stone to be AUTO mode and start the control of the SO2. ♦ The air chamber pressure shall be within the range of 12~15Kpa, the air chamber pressure shall be controlled by slag discharge or increase the bed material feeding. The alarming value of the air chamber pressure is 19Kpa. ♦ Set the main steam control to AUTO mode. 2.2 Warm Start (bed temperature>500℃, without coal feeding) ℃ During the warm startup of the boiler, the air cleaning process should be carried out before starting of the ignition through SA, and start the under bed oil burner. Because the bed temperature is already high before the air cleaning process and then it is not required to check the temperature increasing speed. After this the startup sequence maybe followed as per the startup of the boiler under cold state. 2.2.1 Fans ♦ Keep the inlet guide vane of the ID fan and PA fan are at close position. ♦ Keep the damper of the SA fan and the oil burner at MANUAL position and fully closed. ♦ Keep the ID fan and PA fan control system at MANUAL mode. ♦ Close the inlet guide vane wheel of the ID fan and then start up the ID fan ♦ Keep the furnace pressure control at AUTO mode. ♦ Startup the high pressure air fan for the loop seal and the open the air damper. 330B-SM8 Boiler Operation Manual Page 18 of 46 ♦ Check the air flow in the material returning damper. ♦ Startup the PA fan. ♦ Startup the SA fan. ♦ Slowly open the inlet guide vane of the ID fan and check the furnace pressure. ♦ Adjust the ID fan and set at AUTO mode. 2.2.2 Air cleaning ♦ Manually adjust the PA flow to 30%. ♦ Open the SA fan damper and the oil burner damper. ♦ Startup the air cleaning 2.2.3 Oil supply ♦ Make sure the PA flow exceed 30% of the total air flow. ♦ The oil control valve is set at MANUAL position. ♦ The air flow to the oil burners shall be set at MANUAL position, the primary air flow shall be controlled to make sure it is not less than the fluidized air flow. ♦ The burners shall be put into operation by proper order (site inspection). ♦ Slowly increase the PA flow and check the flame stability. ♦ Increase the oil supply. ♦ When the temperature is steadied and higher than 550℃, impulsive coal feeding shall be started. ♦ The temperature difference of the upper and lower side of the drum shall be checked to less than 40℃. ♦ Feed the limestone as per the specified ratio according to the requirement ( by checking the SO2 value ) 2.2.4 Coal feeding ♦ When the bed temperature is higher than 550 ℃ (this is the recommended value，the actual value shall be based on by coal characteristics , and to be 330B-SM8 Boiler Operation Manual Page 19 of 46 determined during commissioning) feed the coal to the furnace. ♦ Coal feeder is under MANUAL mode. ♦ Open the stop valve and isolation gate valve of the bunker. ♦ Start the supply of the sealing air to the coal feeder and isolation gate valve. ♦ Start the No.1&No.6 coal feeder (under the lowest RPM) and coal feeding shall be made in every other 90s for 90s. With 3 times of impulsive coal feeding. ♦ Ignition condition can be judged according the bed temperature increasing speed (more than 5℃), oxygen flow and irradiancy of the coal particles. ♦ After the confirmation of the ignition of the coal, the coal feeder shall be continuously operated under the lowest RPM. ♦ Put No.2, 3, 4, 5 coal feeder into operation. ♦ According to the requirement to reduce the output of the oil burner and at the same time to increase the RPM of the coal feeder. ♦ Check the bed temperature increasing speed and further increase the coal feeding. ♦ ♦ (Manually) start the limestone feeding function group and adjust the output of the limestone feeder to 10%. With the minimum load, and when the bed temperature high than 780℃, the oil supply can be gradually decreased, and the 2 middle burners can be shutdown, while the coal feeding can be increased to ensure the increase of the load. ♦ Under the precondition of maintain the bed temperature, the other burners shall be shutdown, while the coal feeding can be increased to ensure the increase of the load. Follow the specified curve to increase the PA flow along with the boiler load increasing. If the set values for the main steam pressure and temperature have been reached and then function the load control and the fuel feeding control. Changeover the control of the feeding of the lime stone to be AUTO mode and start the control of the SO2. The air chamber pressure shall be within the range of 12~15Kpa, the air chamber pressure shall be controlled by slag discharge or increase the bed material feeding. The alarming value of the air chamber pressure is 19Kpa. Set the main steam control to AUTO mode. ♦ ♦ ♦ ♦ ♦ 330B-SM8 Boiler Operation Manual Page 20 of 46 2.3 Hot Start ♦ After the startup of the air fans and if the bed temperature is more than 600 ℃ (fuel feeding is allowable) and then the startup under hot state may be carried out. ♦ During the process of the startup of the boiler under hot state the bed temperature is always higher than the temperature required for the fuel feeding and hence the coal feeding maybe immediately carried out without carrying out the air cleaning and the ignition. ♦ Once the fed coal is ignited under the lowest RPM of the feeder and then increases the combustion ration. After around 35 minutes the boiler load can reach the full load. Considering of that the cyclone cylinder is under hot state and has large heat reserved and then the above process is possible. This refers to that it does not need to consider the permissible temperature increasing speed of the refractory lined during the startup of the boiler under hot state. Consumption Data of Boiler Fatigue Life OPERATION CONDITION Cold startup (metal temperature < 40% of that at full load) TIMES DESIGNED 200 WASTING EVERY TIME (%) 0.02555 0.00876 0.00759 0.00426 0.000675 Warm startup (metal temperature: 40-80% of that at full 3000 load) Hot startup (metal temperature: >80% of that at full load) 4000 Very hot startup (metal temperature: around that at full 500 load) Step break load (10% of turbine rated power) 12000 3. Normal Operation 3.1 Check Up During the Boiler Operation 330B-SM8 Boiler Operation Manual Page 21 of 46 ♦ The cyclone inlet gas temperature should not exceed 950℃. The temperature is too high, and refractory materials or metal pressure parts can be burned out. ♦ Bed temperature thermocouple and corresponding instruments are under normal working conditions or not. ♦ Check primary air flow to gird to ensure flow between primary and secondary air is normally distributed. ♦ ♦ Check the percentage of oxygen in gas to ensure oxygen meter works well. Check the furnace bed pressure, validate the pressure measuring points and the pipelines transiting pressure are blocked or not, to ensure the bed pressure normally indicates. ♦ Watch there is anything wrong with bottom ash discharge system or not, measure bottom ash discharge temperature. ♦ Check the drum water level is normal or not. If necessary, blow off glass water gauge. Validate the feed water control valve is normal or not. ♦ Often sample and analyze “the coal in the front of boiler” and validate granularity distribution of solid fuel and the change of fuel ingredient. ♦ Periodically sample, analyze and assay feed water, the boiler water, saturated steam and superheated steam. ♦ Periodically test feed water quality effecting steam and timely chemically deal with the boiler water. ♦ Periodically place soot blowing system in service. When the boiler normally operates, it should blow soot if the economizer outlet gas temperature is 16℃ higher than normal temperature. ♦ Check there is abnormal voice, vibration or move in the area of the boiler. 3.2 The load Adjustment The load adjustment of the boiler is realized by means of changing of the fuel feeding speed and its corresponding air flow manually or automatically. To avoid the bed temperature variation, the adjustment shall be made frequently, and the range of 330B-SM8 Boiler Operation Manual Page 22 of 46 the adjustment for each time shall be small. The major adjustment of the boiler load is made by adjusting the bed materials layer height whereas the bed temperature control can also be used as an auxiliary method. ♦ The fuel feeding and the air supply increases during boiler load increasing, the bed height When the bed temperature remains unchanged and the bed material layer height is increased it can increase the heat absorbing volume of the furnace wall. Otherwise when the fuel feeding quantity and the air supply flow decrease the bed material layered height will be reduced and then the boiler generation capacity will also be reduced. ♦ When increasing of the load firstly slightly increase the PA and SA air volume and then slowly increase the fuel feeding quantity to realize that the bed material layer differential pressure gradually increase and then slowly increase the air supply and the fuel feeding quantity till the required output of the boiler reaches. ♦ When reducing the load of the boiler firstly reduce the fuel feeding quantity and then suitably reduce the PA and SA air volume and at the same time discharge slowly part of the circulation ash to reduce the bed material layer differential pressure. Conduct this process for a number of times till the required output of the boiler reaches. ♦ To avoid the fuel inside the boiler exceed the normal value, i.e. the risk of excessive fuel, the adjustment of air/coal ratio shall be made with the principle that: the increase of the air flow shall be made before the increase of the fuel feeding, and the reduce of the air flow shall be made after the reduce of the fuel feeding. ♦ The changing of the bed temperature can also adjust the boiler load. In principle the high load represents the high bed temperature and the low load represents the low bed temperature. But the bed temperature is affected by a number of factors and the adjustment range is also limited. Hence compared to the adjustment of the bend material layer height the adjustment of the bed temperature to realize the adjusting of the boiler load is not an ideal method. ♦ The height of the bed layer is mainly controlled by ash discharge, and the ash discharge flow is controlled in accordance with the air chamber pressure indication, during normal load, the ash discharge shall be made when the bed pressure indication is between 4~6Kpa. 330B-SM8 Boiler Operation Manual Page 23 of 46 3.3 Water Level Adjustment ♦ The rapid change of the drum water level will result in the variation of the steam pressure and temperature. If the water overflow or shortage incurs during the operation of the boiler and then the shutdown of the boiler will happen. Hence it is a must to maintain the uniform water feeding to the boiler drum to achieve the normal water level. ♦ The normal water level of the drum is at 150mm below the drum centerline. The maximum and the minimum (or the highest and lowest) water level is±50mm. The drum water level control should be: When the drum water level reaches -50 mm or 100mm the sound and light alarm will be sent by DCS. When the drum water level reaches -180mm or +200mm the MFT shall function. ♦ When the boiler is operated under low load the drum water level is slightly higher than the normal water level to avoid the formation of the low drum water level in case of the load increasing. Or when the boiler is operated under high load the drum water level is slightly lower than the normal water level to avoid the formation of the high drum water level in case of the load reducing. But in any case the variation of the water level should not be beyond the permissible range. 3.4 The Bed Temperature Adjustment ♦ The bed temperature of the boiler is generally at 890℃. Considering of that there is the requirement like load variation or others the bed temperature should be controlled at 850~920 ℃. The measuring is made at the dense phase of the lower furnace ♦ If the bed temperature is too high and the lasting time is too long it may create the agglomeration of the slag of the bed material and finally result in the unavailability of the function of the boiler. Or if the bed temperature is too low, the complete combustion may not be achieved and it may result in the fire loss. The major means to adjust the bed temperature is to adjust the fuel feeding quantity and the PA air flow to the air distribution plates. 330B-SM8 Boiler Operation Manual Page 24 of 46 ♦ If it is impossible to maintain a bed temperature of more than 990 ℃ ( limit temperature is 1050 ℃ ) the air supply flow should be immediately redistributed by increasing the PA air flow to the air distribution plates and reducing the SA supply. 3.5 The Steam Pressure Adjustment ♦ The load requirements for bed height and bed temperature shall be based in coal feeding to ensure a steadily combustion and control the fluctuation of the steam pressure, the steam pressure shall be within the scope of 13.7MPa±0.1MPa. ♦ The adjustment of the feed water flow is an alternative method to control the steam pressure. When adopting this method the drum water level should be controlled within the permissible range. 3.6 The steam temperature adjustment The steam temperature is influenced by many matters such as boiler load, feed water temperature, characteristics of the fuel, excess air coefficient, combustion conditions, etc. therefore, the adjustment shall be made based on the interrelationship of these matters. The main purpose of the steam temperature adjustment: ♦ Make sure the fluctuation of the steam temperature within the required range, when the boiler load is within 70~100% BMCR, the outlet temperature of the superheated and reheated steam shall be 540℃ ±5℃ ♦ Make sure the tube metal temperature of the superheater and reheater tubes not exceed the alarm value indicated in table2. ♦ For the superheater, 2 stage of spray desuperheater is installed for temperature control, the spray desuperheater is characterized by its simple structure, flexible control and facile in automatic control. The primary and secondary spray desuperheaters are installed between the primary wing walls and between the secondary wing wall and high temperature superheater respectively. The primary spray is applied to protect the wing wall 330B-SM8 Boiler Operation Manual Page 25 of 46 superheater from overheating, especially during partial load, and the secondary spray desuperheater is applied to control the live steam temperature at superheater outlet, make sure it is within the rated value. ♦ The reheater temperature is controlled by the flue gas damper. To make sure the system is safety and reliable, and the emergency spray desuperheater is installed in front of the low temperature reheater. ♦ Before and during the boiler startup, there is no steam for reheater cooling; therefore the bypass protection device is installed, which provide sufficient steam to the heating surface, to guarantee the boiler safety during boiler startup and shutdown. 3.7 Steam Quality Control and Adjustment The steam quality shall be in accordance with the requirements of the relative standard and regulation. ♦ By controlling the continuous blow down valve and periodical blow down valve to make sure that the solid content of the water is lower than the critical value. ♦ Make sure the drum level is ±50mm within the normal water level, to avoid the abnormal water level condition. ♦ Avoid the abrupt increase of the unit load and abrupt decrease of the steam pressure. 3.8 Air Distribution Control The principle for adjusting the primary and secondary air is: ♦ PA: adjusting the bed material fluidization, bed temperature and bed pressure. ♦ SA: control the total air flow, with the precondition that the requirements for bed material fluidization, bed temperature and bed pressure are satisfied by the PA, when the total air flow is not enough, the secondary air damper could be gradually opened, and the SA flow will increased with the increase of the boiler load. ♦ When it is judged that part of the bed material is not properly fluidized, the 330B-SM8 Boiler Operation Manual Page 26 of 46 PA flow and slag discharge shall be temporary increased. ♦ Special attention shall be paid to the fluidized condition of the bed, combustion condition and material return; any problem shall be solved as soon as possible. PA and SA ratio, PA and SA flow, as well as the coal feeding shall be adjusted in time. 3.9 Emission control of NOx and SO2 ♦ Check the discharge concentration of the SO2 and then manually or automatically adjust the feeding speed of the limestone to ensure that the SO2 discharge concentration to conform to the Regulations. The discharge concentration of SO2 should not be 75% lower than the Regulation for long time because this will make the boiler to be operated under low efficiency. ♦ The control of the discharge concentration of the NOx in the flue gas maybe realized by means of adjusting of the bed temperature. When the bed temperature is higher than 940 ℃ the NOx in the flue gas will be obviously increased whereas the same maybe adjusted by changing the distribution between the PA, SA air flow and the SA flow and further adjust the excess air factor. When the bed temperature is between 820 ℃ and 900 ℃ the concentration of the NOx in the flue gas will reach the lowest level. 3.10 Boiler Soot Blow ♦ The purpose of the boiler blow down is to keep all the heating surfaces clean, and to make sure the duct is not blocked. ♦ It is recommended that the soot blow shall be made in each shift, and this frequency shall be adjusted according to the actual condition. During the normal operation, the soot blow shall be made at least in each shift, during the boiler soot blowing, the boiler load shall not be less than 70% BMCR, and the outlet pressure of the furnace shall not exceed -250Pa. 3.11 Miscellaneous ♦ When the bed temperature is lower than 760 ℃ the startup burner should be functioned. 330B-SM8 Boiler Operation Manual Page 27 of 46 ♦ During the operation of the boiler carefully check the temperatures changes and the resistance changes of the various parts of the boiler. When the temperature or the resistance changes abnormally the inspection should be carried out to verify if there is any air leakage, or excessive excess air, or agglomeration on the bed or abnormal combustion. ♦ During the operation of the boiler please also monitor the variation of the coal quality and adjust the boiler accordingly. 3.12 DCS Automation 3.12.1 Thermodynamic inspection Thermodynamic inspection is an operation condition which automatically inspects the operation condition of the equipments and measures the different parameters that reflect the process of the boiler. Thermodynamic inspection could timely reflect the manufacture process and the trend of the operation, provide the basis for operating, and provide single for other automatic thermal device. The thermodynamic inspection is very important to ensure the safety and reliable operation of the unit. The main item of the thermodynamic include the pressure of the live steam and reheat steam, temperature, feed water pressure, feed water temperature, feed water flow, drum level, furnace pressure, 02, exit gas temperature, air temperature, air pressure, fuel flow etc, which is completed by the DCS of the data collection system, and it including all the basic content including the dispose, display, alarm, record, storage etc. of the non-electric and electric measuring data, and also including data statistics, data analysis, operation guidance, failure analysis etc. this system is basically the same as the DAC of the DCS of the normal boiler. 3.12.2 Analog Control With analog control, the boiler operation condition is automatically and continuously controlled, the boiler operating parameter will be controlled to fluctuate according to certain rules and within a certain scope, e.g. to maintain a specified drum level, to adjust the steam pressure to satisfy the load requirements. The main item of the analog control include the automatic feed water control, automatic combustion control and automatic control of the superheater and reheater steam temperature, etc. 3.12.3 Sequence Control 330B-SM8 Boiler Operation Manual Page 28 of 46 Sequence control is a series of automatic operations, which are made on the basis of pre-determined steps, conditions and times, to adjust the operation condition of the different systems and equipments. It could be applied not only to single equipment but also to a system, even to the whole unit. The sequence control is mainly applied to the section concerning the fuel and combustion, e.g. FSSS, which is applied to control the control valves and the switches relevant to startup and shutdown of the combustion system. Currently, the sequence control is mainly applied to the startup and shutdown of the boiler proper and auxiliary equipment and the operation and emergency control for part of the system. 3.12.4 Thermodynamic Protection Mains that during the startup or shutdown of the boiler units, when the operation conditions that may jeopardize the safety of the equipments and/or people’s life happens, to prevent the emergency or avoid the emergency from becoming severe, the thermodynamic monitoring devices will automatically function and carry out the protection measures, the thermodynamic protection include three actions: 1. Alarm signal: tell the operators about the abnormal condition of the units; 2. Linkage action: the program automatically startup or shutdown certain equipment and/or system if necessary, and make sure the units maintain the original load and decrease the load. 3. Trip protection: the trip protection is made during major failure or when the safety of the unit and people are jeopardized, to stop certain equipment or unit to prevent the emergency from becoming severe. CFB Furnace Safety Supervision System (FSSS) The safety protection of the boiler is particularly emphasized on the accuracy of the order as well as the linkage of the fuel feeding and combustion to guarantee the steady of the combustion. This protection function is called “Furnace Safety Supervision System (FSSS)”, which follows the former parlance of the PC boiler. The FSSS system include the furnace safety system (FSS) and burner control system (BCS), the main functions of this system are main fuel trip (MFT), startup oil system leakage test, CFB boiler cold startup (establish of the fluidized air and initial bed material) as well as the control operation during the temperature of the CFB boiler is increasing, hot startup, control of the under bed oil igniter, fire detection, control of the over bed oil 330B-SM8 Boiler Operation Manual Page 29 of 46 igniter, control of the coal and limestone system, and linkage control of the PA fan, SA fan, high pressure fluidized bed air fan, induced air fan, etc. The combustion style of the CFB boiler is different from that of the PC boiler. During the boiler operation, the CFB boiler, with large amount of high temperature solids that could be applied as the constant ignition resource, bears no risk of fire extinction and improper accumulation of the explosive mixture. At the same time, the combustion temperature of the CFB boiler is relatively lower, the flame is not as strong as in PC boiler, the continuous supervision for coal powder burners and the combustion condition of the whole boiler furnace is therefore unnecessary. Furthermore, to compare with the PC boiler, CFB boiler has less coal burners and oil burners, so it is unnecessary to start the burners installed on different layers and corners to follow the load change. CFB start the oil lance only during the boiler startup stage or when the bed temperature is low, and for the CFB boiler, the number of burners is much less than then the PC boiler, so the burner control system of the CFB boiler is simpler than that of the PC boiler. The thermodynamic inspection parameters, the alarming value, linkage requirements, condition for MFT for this boiler are mentioned in the corresponding chapters of this specification. 4. Boiler shut-down The boiler shutdown may be resulted by different reasons, include scheduled shut down and shut down caused by fail of the boiler. Therefore there are two kinds of shut down: boiler shut down to hot state and boiler shut down to cold state. Boiler shutdown to cold state means boiler is cooled to normal temperature for spare or overhaul, i.e. normal shutdown, for which variable pressure is applied. The boiler fuel supply shall be decreased with the load decrease of the steam turbine, make sure the turbine requirements for steam temperature, pressure and flow are satisfied. Boiler shutdown to hot spare state means to prevent the boiler from heat loss after boiler shutdown to facile the boiler shutdown within a short period. For boiler shutdown to hot state, the constant pressure shall be applied, and the unit load shall be larger than 30%, and the speed adjustable port shall be gradually closed, and the load shall be decreased. Along with the decrease of the boiler combustion rate, the steam temperature shall be less than 100℃, otherwise, the set value of live steam pressure 330B-SM8 Boiler Operation Manual Page 30 of 46 shall be decreased to ensure the degree of superheat is enough. The emergency means the boiler shutdown due to certain emergency, e.g. damage of the heating surface, failure of the separator or material return device, serious accident of the auxiliary equipment, failure or problem of the turbine or grid. In this insistence, the fuel feeding shall be stopped during operating condition to ensure a fast cooling of the boiler. 4.1 The scheduled shutdown of the boiler to cold state ♦ Gradually reduce the fuel feeding and the air supply to reduce the boiler load to 50%. This maybe realized by adjusting the set value of the master controller of the boiler but the normal bed temperature should be maintained. ♦ During the load reducing process the drum upper and lower wall temperature difference of not more than 50 ℃ should be maintained. ♦ When the load is reduced to 50% and before the stop of the operation of the boiler the soot blowing process should be carried out to avoid the sulfur contained accumulated ash to absorb the moisture from the air to result in the erosion of the tubes. ♦ Continue the reducing of the boiler load and reduce the fuel feeding quantity with the speed of not more than 10% per minute. ♦ When the load is reduced the steam temperature should be maintained to be higher than the saturated steam temperature. ♦ Before the bed temperature is lower than 650 ℃ start the oil burner and continues the reducing of the fuel feeding quantity. ♦ When the temperature variation of the flue gas temperature inside the cyclone separator is separately maintained at 100 ℃ and 50 ℃ temperature reducing limit and then reduce the oil burner firing speed. ♦ Maintaining the limestone feeding at AUTO mode till the fuel feeding stops. ♦ If required set the drum water level controller at MANUL position but always maintain the normal water level inside the drum. ♦ Stop the feeding of the fuel and stop the limestone feeding as well as the discharge of the bed material. ♦ During the stop process of the boiler the drum water level should be maintained at the upper limit of the level gauge which should be visible. 330B-SM8 Boiler Operation Manual Page 31 of 46 ♦ Continue the fluidization of the bed material and keep the pressure parts temperature reducing speed of not more than 50 ℃. ♦ When the bed temperature reaches 450 ℃ stop the oil burner. ♦ When the bed temperature reduces to at least 400 degree close the inlet control baffler plates of the PA fan and SA fan. ♦ After the air fans baffler plates are closed and the stop all the air fans. ♦ In case the boiler is shut down for a long period, the water inside the drum shall be discharge, or the nitrogen blanket shall be applied to protect the drum. 4.2 Shutdown of the boiler to hot standby ♦ If required to temporary shutdown the boiler the fire banking method maybe adopted to keep the boiler to be functioned under hot standby. ♦ When carrying out the fire banking process the boiler load should be reduced to the lowest level and stop the fuel feeding to make sure that the fuel in the bed maybe completely combusted. When the oxygen content in the flue gas is increased at least to 2 times of the normal value stop the air supply to the combustion chamber to reduce the bed heat loss and then close the baffler plates of the inlet wheel and the air duct to maintain that there is no firing inside the furnace ) ♦ When the bed temperature is lower than 600 ℃ the oil burner maybe started to increase the bed temperature to more than 600 ℃ and then start the feeding the fuel. ♦ During the process of the fire banking and the hot startup of the boiler the drum water level should be maintained. 4.3 The emergency shutdown If any of the following happens the boiler should be shutdown immediately: ♦ The serious shortage of the drum water and the drum water level is still not visible even after make-up of the water. ♦ The serious water overflow and the drum water level increases above the highest visible water level and even after the emergency release of the water the water level is still not visible. ♦ The heating surface tube bursts and not possible to maintain the normal water level. ♦ The boiler is seriously forming of the slag. 330B-SM8 Boiler Operation Manual Page 32 of 46 ♦ All the water levels are damaged and not possible to monitor the drum level. ♦ The back firing happens inside the flue gas duct after the boiler outlet and the flue gas temperature is abnormally increasing. ♦ The furnace wall cracks and there is chance of falling down to hamper the safety of the operators and the equipment. ♦ Fire went out. ♦ The system incurs the load throw-off and the safety valves does not function even when the steam pressure is beyond the limit value and the steam release to air could not reduce the pressure. During the emergency shutdown a lot of factors are being changed related to the boiler and hence certain measurements should be taken to limit the incidents to widely spread. These measurements include: ♦ Immediately cut off the fuel supply and timely reduce the boiler load. ♦ Adjust the fee water to the boiler to maintain the normal water level. ♦ If the combustion chamber incurs the serious leakage and then the feed water supply to the boiler should be stopped and immediately discharge the bed material from the bed. ♦ If the leakage incurs inside the convection flue gas duct the normal water level of the drum should be maintained. ♦ The cooling process for the emergency shutdown of the boiler is the same as the scheduled shutdown of the boiler but the time maybe shortened. 4.4 The fast cooling down of the boiler after the shutdown ♦ When the boiler bed material layer reduced fully close the bafflers of the flue gas system. ♦ When the bed temperature reduces to 400 ℃ start the ID fan, the high pressure air fan, the PA fan and the SA fan to carry out the compulsory cooling to the furnace. But the air baffler plates should not be opened too wide and control the temperature reducing speed at 100 ℃ per hour ( as per the requirement of the refractory supplier ) ♦ When the bed temperature reduces to 150 ℃, stop the high pressure air fan, the SA fan and the PA fan and then open the manhole at the lower portion of the furnace wall and suitably increase the furnace negative pressure value according to the temperature reducing speed. 330B-SM8 Boiler Operation Manual Page 33 of 46 ♦ When the temperature reduces to less than 60 degree stop the ID fan. ♦ If the boiler is shutdown for hot standby or it is not required to speed up the cooling of the boiler the compulsory cooling of the boiler may not be carried out. ♦ When the boiler shutdown for 5 days and then the bed material should be discharged to recover the small particle size bed material or may not discharge the bed material. In order to guarantee the safe and correct startup and operating of the boiler the above procedures should be followed. The operation manual may be prepared by the client according to the actual operation experience. The operation of the auxiliary equipment affiliated with the boiler please refer to the operation manuals of the equipment provided by the manufacturer. 5. The precautions The operator should abide the following precautions during each stage of the operation of the boiler: ♦ ♦ During the operation of the boiler the furnace inside, especially the lower portion of the furnace is positive pressure state. The furnace door should be kept closed. The over high or over low pressure inside the furnace may result in the damage of the boiler and its auxiliary equipment. Hence the control of the furnace pressure is key important factor. The following controls should be reliably functioned before the startup of the boiler. a． Monitor the furnace negative pressure (measured at the furnace outlet balancing point). The negative pressure should be automatically controlled between -100 ~ -250 Pa. The operator should not allow the pressure at the balancing point of the furnace to be more than +/-500Pa. ( alarm value ) b． The MFT is set at +/-2500Pa at the outlet pressure of the furnace with 5 seconds lagging. c． The trip is set for the air supply at +/-400Pa at the outlet pressure of the furnace without lagging. ♦ After the trip of the MFT a lot of heat is still reserved inside the circulated material inside the boiler and then the boiler drum level and the steam pressure should be monitored. The drum water level control and its alarm value please clause 3.3. ♦ The calibration of the safety valve 330B-SM8 Boiler Operation Manual Page 34 of 46 All the safety valves have been calibrated in the manufacturer’s workshop but the same should be again checked during the startup of the boiler. Any defect should be rectified. ♦ The requirement of the excess air In order to maintain the proper combustion conditions the excess air factor inside the furnace should be controlled to guarantee the suitable ratio between the air and the fuel. Under the rated load the corresponding oxygen content is controlled at 3~4.2% which maybe taken as the reference date to be adjusted according to the combustion situation. ♦ The various temperatures distribution The thermocouples are arranged around the furnace on top of the air distribution plates through which to closely monitor the variations of the bed temperature. There are 6 measuring points under the boiling, the average value of these 6 measured temperature to be taken as the control temperature for fuel feeding quantity adjustment. (The highest temperature and the lowest temperature may be not considered and the average value may be taken from the balance 4 temperature values). The bed temperature range is 850 ℃ ~ 900 ℃, the high value alarm point is 990 ℃ and when the temperature is above 1050 ℃ the main fuel supply shall trip. The minimum bed temperature for operation of the boiler is 830 ℃ and in principle the bed temperature is not allowed to be lower than this value without the functioning of the oil burner to provide the supporting combustion. The low value alarm point is 820 ℃ and when the bed temperature is lower than 800 degree the main fuel supply shall trip. Until the oil burner is functioned to provide the supporting combustion and when the bed temperature is reduced to less than 650 ℃ the fuel feeder shall trip irrespective of the functioning of the oil burner. ♦ Protection of tubes on heating surface of the cyclone separator If cut off the assembling unit, the temperature of heating surface tube may rise rapidly. In case the thermal couple of the header on the top of the separator indicates the temperature of steam higher than 500℃, the control system will enlarge the exhaust quantity automatically to increase the velocity of the steam and cool the tubes of the heating surface on separator. ♦ In order to monitor the startup and the operation situation the thermocouples are arranged on the piping at the steam side to monitor the operation as well as control the startup 330B-SM8 Boiler Operation Manual Page 35 of 46 speed. The details refer to the following table: 330B-SM8 Boiler Operation Manual Page 36 of 46 Location Drum Installation location Top and bottom Qty.& Spec. 12-thermocouple Alarm Temp. Temperature difference between the top and lower wall ＜40℃ Remark 6 points on top and 6 points at the bottom SH hanger tube Hanger tube get through the ceiling 24-thermocouple 445℃（455℃） Please refer to the arrangement DWG. of the measuring points for the position, the function is to supervise the wall temperature of hanger tube RH O/L tube the wall of the coil tube get through the front cage 24-thermocouple 582℃（592℃） Please refer to the arrangement DWG. of the measuring points for the position, the function is to supervise the wall temperature of coil tube Wing Wall I tube Wing Wall 1 tube Wall Through the ceiling 6×1- thermocouple 507℃（517℃） Please refer to the arrangement DWG. of the measuring points for the position, the function is to supervise the wall temperature of wing wall tube Wing Wall II tube Wing Wall II tube Wall Through the ceiling 6×1- thermocouple 543℃（553℃） Please refer to the arrangement DWG. of the measuring points for the position, the function is to supervise the wall temperature of wing wall tube HT SH O/L tube Coil Tube Wall Through the rear cage 24- thermocouple 585℃（595℃） Please refer to the arrangement DWG. of the measuring points for the position, the function is to supervise the wall temperature of coil tube Feed Water Control Board ECO O/L Heater Spray Attemperator I Spray Attemperator II Live Steam O/L Piping RH Emergency Spray Attemperator RH O/L Piping ECO I/L Header 1- thermocouple supervise the inlet water temperature ECO O/L Header both ends of the Attemperator I header both ends of the Attemperator II header Live Steam O/L header 2- thermocouple 3- thermocouple O/L dry steam saturated temperature 11℃ 3- thermocouple O/L dry steam saturated temperature 11℃ 2×2- thermocouple supervise the ECO outlet water temperature supervise Wing Wall I O/L steam temperature and Wing Wall II I/l steam temperature supervise Wing Wall II O/L steam temperature and HT SH I/L steam temperature supervise Live Steam Temperature 540±5℃ top of the header 3- thermocouple O/L dry steam saturated temperature 11℃ supervise RH I/L Steam Temperature RH O/L Header 2×2- thermocouple Supervise the RH steam temperature 540±5℃ The above thermal couples and all other thermal couple should be inspected (including indicating value in the control room) and put into operation at any time. During the operation, the boiler can keep on running as long as the steam temp. is not exceeding the alarm value mentioned above. 330B-SM8 Boiler Operation Manual Page 37 of 46 6．The protection during the shutdown of the boiler ． 6.1 The Nitrogen Blanket If the boiler shutdown period exceeds one week the nitrogen blanket shall be applied to protect boiler. ♦ When the drum pressure reduced to 0.3Mpa, the nitrogen shall be filled into the drum and keep the nitrogen pressure at 0.3-0.5Mp,open the draining valves to fully discharge the water .After water have full discharged by nitrogen pressure, close the draining valves. ♦ Make a fully inspection to boiler steam & water system, close all the air valve, drain and release valve, blow down valve, feed-water pipe, main steam pipe and drain valve, seal the whole nitrogen system. ♦ During the nitrogen injection, the nitrogen pressure within the drum should not less than 0.03MPa; the purity of nitrogen should not less than 98%. 6.2 The curing method through water release and drying under hot state When shutdown of the boiler for maintenance of the pressure parts or if the shutdown time is within one week the curing method through water release and drying under the hot state may be adopted. ♦ After the bed is fall down, all dampers for air and flue gas shall be close. and the flue gas and air system shall be closed, ♦ When the drum pressure reduced to 0.5 MPa ~ 0.8 MPa, open the drain and water release gate, and the water in the boiler should be released as soon as possible. ♦ When the drum pressure reduced to 0.1 MPa ~ 0.2 MPa open the air gate of the boiler proper. ♦ When the drum water is almost fully released (discharged) and the bed temperature is reduced to 120℃ and then start the ID fan, the High voltage air fan, the PA fan the SA fan and the function the two numbers of the oil burner to maintain the fluidization air volume and the temperature between 220 ℃ and 300 ℃. And the drying the boiler by means of the hot air continuously for 10 to 12 hours and then stop and close the boiler. When the outlet flue gas temperature at the outlet of the economizer is reduced below 330B-SM8 Boiler Operation Manual Page 38 of 46 120 ℃, close all the air gates of the boiler proper and the drain and water release gate. ♦ During the curing of the boiler the relative humidity inside the boiler should be less than 70% or shall be equal to the environmental relative humidity. 6.3 The anti-corrosion under pressure filling for boiler ♦ If the shutdown period of the boiler is only 2 to 3 days the pressure filling method maybe adopted for protection of the boiler. ♦ After the stop of the operation of the boiler maintain the natural pressure reducing ( the CBD may not be stopped ) ♦ When the boiler pressure reduces to 5.8Mpa analyze the boiler water parameters. If found the water quality is not qualified and then change the boiler water till the water quality matches the requirement and then close the first and second gate of the IBD as well as the main gate of the IBD to stop the IBD function. ♦ The boiler water has to be made qualified before the boiler pressure decreases to 0.5Mpa. ♦ When the boiler pressure is above 0.5Mpa and the superheater wall temperature is below 200 ℃ the water maybe fed to the boiler to start the pressure increasing. ♦ The anti-corrosion pressure is generally maintained at 2.0Mpa ~ 3.0 MPa but not more than 5.8Mpa and not less than 0.5Mpa. ♦ If the boiler pressure decreases to below 0.5Mpa (the pressure reaches 0) due to certain reasons and then the re-ignition is a must to increase the pressure to 4.0 Mpa and then repeat the above procedures. ♦ Once the pressure filling is completed the dissolved oxygen should be analyzed. 6.4 Anti-frozen Methods Before the winter started, the anti-frozen measures shall be fully inspected; the bare tubes are not allowed, the anti-frozen heating devices shall be put into use. The heating device of the oil tubes shall be operated through out the year; overhaul during winter time is prohibited. All the water deposited inside the instrument pipe shall be discharged; the doors, holes and dampers for spare boiler shall be closed. For boiler under overhaul, measures shall be taken to prevent the cold air from coming in. For boiler not in operation, dry method shall be applied for maintenance, in case there is water 330B-SM8 Boiler Operation Manual Page 39 of 46 inside the boiler, when the boiler water temperature lower than 10℃, the water fill and water discharge shall be made, and the water shall be discharged at the lower points, and the heating up system from the neighboring boiler shall be applied when necessary. 7. The trouble shootings 7.1 The too high or too low bed temperature Phenomenon: ♦ The displayed bed temperature is high or low. ♦ The alarm for the high bed temperature ♦ The load increase or reduce. Reason: ♦ The fuel particles may be oversize or downsized. ♦ The measuring fault of the thermocouple. ♦ The fuel feeder not in working condition. ♦ The mismatch of the PA and SA distribution. ♦ Bed ash cooler system fault. ♦ Limestone feeding system not functioning. Measurements: ♦ Check the thermocouple for the bed temperature measuring. ♦ Check the fuel feeder performance as well as its controls. ♦ Adjust the air distribution of the PA and SA. ♦ If the bed temperature is too low and results in the unstable combustion the oil gun should be functioned to provide the supporting combustion. 7.2 The bed pressure is high or low Phenomenon: ♦ The alarm is sent for the high or low bed pressure ♦ The bed ash cooler discharge load is seriously increased or the discharge stops. ♦ The air box pressure is too high or too low. Reason: ♦ The bed pressure measuring fault. ♦ The bed ash cooler fault ( discharge volume is more or too less ) 330B-SM8 Boiler Operation Manual Page 40 of 46 ♦ The feeding of the limestone and the fuel is not proper. ♦ The PA volume is not proper. ♦ The boiler load increasing is too fast or the fuel quality variation is too large. Measurements: ♦ If the bed pressure is high and then increase the discharge volume of the bed ash cooler and reduce the fuel feeding quantity. If the bed pressure is too low and then reduce the discharge volume of the bed ash cooler and if required to increase the fed quantity of the limestone or sand. ♦ Check the bed pressure measuring points. ♦ If the bed ash discharging fault could not be solved whereas the bed pressure is larger than 8 KPa and the boiler should be shutdown. 7.3 The water wall tube bursts Phenomenon: ♦ If the tube is minor burst and the welding portion leakage happens the steam leakage sound will happen and the feed water volume will be slightly increased. ♦ If the tube burst is serious there is the obvious cracking sound and the steam sound and the furnace pressure will become positive instead of negative and the feed water flow is abnormally larger than the steam flow. Reason: ♦ The boiler water and the feed water quality is not up to the mark for a long time and has resulted the fouling inside the tube and the further resulted in increasing of the resistance locally to form the local over heated. ♦ The water circulation is not proper and results in the local over heated. ♦ The tube material may not be qualified or the welding quality is poor or serious erosion happens on the outer wall of the tube. Measurement: ♦ When the water wall damage is not serious: a、 Increase the feed water flow to maintain the drum water level and then operate the boiler at lower load or shutdown the boiler as per the normal procedures. b、 If the combustion is not stable the oil burner should be started to provide the support. 330B-SM8 Boiler Operation Manual Page 41 of 46 ♦ If the water wall is seriously damaged and not possible to maintain the normal water level: a、 Emergency shutdown the boiler and stop the feed water supply to the boiler. b、 Maintain the operation of the ID fan to remove the steam inside the boiler and if the bed temperature decreasing speed is beyond the permissible value and then stop the ID fan. c、 After the shutdown of the boiler immediately remove the bed material. d、 The other operations left please refer to the shutdown of the boiler under normal shutdown procedures) 7.4 The superheater tube burst Phenomenon: ♦ There is the sound of the steam spout and the feed water flow is larger than the steam flow. ♦ The furnace negative pressure decreases or changes to positive pressure and the superheated steam pressure decreases. Reason: ♦ The fouling happens inside the furnace or the foreign substances chocked the tube to affect the heat transmission. ♦ The erosion happens on the outer wall of the tube or the corrosion happens due to high temperature. ♦ The steam temperature or the wall temperature is beyond the limit for long time. ♦ The tube material quality is not up to mark or the welding quality may have problem or the soot blowing is not functioning properly. Measurement: ♦ If the tube burst is not serious and then it is permitted to operate the boiler for a certain time but the load should be reduced and prepare for the shutdown. ♦ If the tube burst is seriously: a、 Maintain the operation of the ID fan to control the bed temperature decreasing speed not to be beyond the specified value. 330B-SM8 Boiler Operation Manual Page 42 of 46 b、 Maintain the feed water supply as less as possible to maintain the normal water level. c、 Other operations according to normal cases. 7.5 Agglomeration formation on the bed Phenomenon: ♦ The indicated value of one or more thermocouples has large difference with the average value ( with the difference of more than 100 ℃ ) ♦ Under the normal bed pressure the air box pressure increases. ♦ The reading of the indication value of one or more bed pressure keep still but not the fluctuation reading during the normal operation. ♦ There is the white color flash in the bed and the slag formation can be seen from the peephole. When the slag formation becomes serious it is difficulty to deliver the load. Reason: ♦ The bed temperature is too high or the bed material melting point is too low. ♦ During the operation of the boiler the air supply and the coal supply does not match for a long time. ♦ More numbers of the air nozzles for fluidization are chocked before the startup of the boiler or there maybe the left inside of substances of the refractory pieces, etc. Measurement: ♦ To increase the PA volume. ♦ To suitable reduce the bed temperature. The precaution should be given to that the increasing of the bed temperature should not the too fast. ♦ After the adjustment and if there is no improvement the boiler should be shutdown. 7.6 The firing inside the flue gas duct Phenomenon: ♦ The discharge temperature of the flue gas is abnormally increasing. ♦ When the horizontal glue gas duct is firing and the oxygen content in the flue gas will be decreased and the main steam temperature will be abnormally increased. ♦ When the vertical flue gas duct is firing the PA and SA air temperature will be increased and the outlet water temperature will be increased at the outlet of the economizer. ♦ The furnace negative pressure fluctuation is more. 330B-SM8 Boiler Operation Manual Page 43 of 46 ♦ The fire comes out from the portion of the flue gas duct which is not properly sealed. Reason: ♦ The air and fuel supply ratio is not proper. ♦ During the startup the oil gun atomization is not proper. Measurement: ♦ Start the soot blowing to the flue gas duct heating surface and if required to reduce the load. ♦ If the above measurement does not help and the discharge flue gas temperature is increased 200 ℃ and then the boiler has to be emergency shutdown. ♦ Stop all the air fans and close the combustion and the flue gas, air supply system. ♦ Maintain the continuous feed water supply to the boiler. 7.7 The feed water shortage Phenomenon: ♦ The drum water level is lower than the normal water level or the water level is not visible from the window. ♦ The water level alarm sends the low level signal. ♦ The steam flow is larger than the actual effective feed water flow in s sudden. Reason: ♦ Due to the negligence of the operator the monitor of the water level is not followed. ♦ The fault of the water supply equipment, like failure of the auto water feeding adjustment or the water level gauge chocked to form the fake water level. ♦ The leakage of the drain and blowdown system of the boiler is more or the discharge is more. ♦ The feed water pipe or the heating surface tubes burst. Measurement: ♦ First cross-check all the water level gauges to verify the authenticity of the water level or the seriousness of the shortage. ♦ If found that the feed water shortage is serious and then the boiler maybe emergency shutdown. ♦ If the shortage is not serious enough to influence the operation of the boiler, the water level shall be resumed by manually water feeding. 330B-SM8 Boiler Operation Manual Page 44 of 46 7.8 The overflow of the drum Phenomenon: ♦ The water level is not visible and the drum water is not clear. ♦ The water level alarms send the high water level signal. ♦ The superheated steam temperature decreases and the salt content in the steam increases. ♦ The feed water flow is larger than the steam flow in a sudden. Reason: ♦ The negligence of the operator to monitor the water level. ♦ The auto feed water adjustment failure or the feed water pressure is more. Measurement: ♦ First cross-check all the water level gauges to verify the authenticity of the water level or the seriousness of the shortage. ♦ Changeover the auto feed water adjustment to manual feed water adjustment. ♦ If the overflow is not serious manually adjust the same by increase the blowdown volume, drain volume and the emergency water release. ♦ If the overflow is serious and the manual adjustment is not helpful and then emergency shutdown the boiler. 7.9 The water impact on the piping Reason: ♦ The pipes are not properly heated and drained before carrying the steam or there is the air left inside the piping. ♦ The intermittent close and open of the BFP to create the unstable water pressure. Measurement: ♦ In case of the water impact, open the drain valve of the superheater system to smooth the drainage and timely release the air from inside the superheater piping system. ♦ For the feed water piping, the water pressure should be stabilized and the air should be released completely. 7.10 The Stoppage of the fuel supply Reason: ♦ The bunker is blocked ♦ The feeder fault. 330B-SM8 Boiler Operation Manual Page 45 of 46 ♦ The fuel feeding pipes are chocked. ♦ The furnace back pressure is too high. Measurement: ♦ Check the Oxygen value from the meter and if found it is obviously higher than the normal value firstly check if there is any breakage of the fuel supply (if found that the bed temperature is continuously decrease and then verify the breakage of the fuel and it will be too late). Conduct the routine check and locate the location of the breakage of the fuel and at the same time increase the speed of the fuel feeder to maintain the total feeding flow. If the back pressure of the furnace is too high, the discharge flow of the ash coolers shall be increased. 7.11 The main fuel trip MFT ♦ The MFT incurs along with the following activities: 1．The cutoff of the main fuel 2．The cutoff of the lime stone supply system 3．The cutoff of the under bed ignition system 4．All the air volume control to be changed over to manual mode and maintain the same. 5．All the air fans control to be changed over to manual mode subject to the cutoff of the air fans itself is not realized. If the air fans itself trip and then the logic control will be followed. 6．The output signal of the combustion control will limit the ID fan auto control to ensure that the furnace pressure is not beyond the limit. 7．If the boiler is at the condition for hot restart the logic for the “specified soot blowing” will be established. 8．The printer shall print the MFT time and the reason. ♦ Any of the following cases will result in the MFT: 1． The two numbers of the MFT buttons are pressed at the same time. 330B-SM8 Boiler Operation Manual Page 46 of 46 2． The bed temperature is as high as 1050 ℃ ( the signal is from the combustion control system ) 3． The loss of the logic control power 4． 2 out of 3 logic control displays the outlet pressure of the furnace is high high +2500Pa ( delayed ) 5． 2 out of 3 logic control displays the outlet pressure of the furnace is low low -2500Pa ( delayed ) 6． 2 out of 3 logic control displays the drum water level is high high ( higher of 250mm above the normal water level ) ( delayed ) 7． 2 out of 3 logic control displays the drum water level is low low ( lower of 250mm below the normal water level ) ( delayed ) 8． ID fan trips 9． PA, SA fan trip 10． Total air volume is lower that 25% ( delayed ) ( the signal is from the combustion system ) 11． The loss of the power for the combustion control system, and the signal is from the combustion control system 12． The air & fuel ratio is less than the minimum value ( the signal is from the combustion control system ) 13． 14． 15． 16． The bed temperature is lower than 800 ℃ and the ignition operates. The material returning air fan trips The turbine trips Only one coal feeder is running. ♦ The dealing after the MFT 1． If the MFT is not caused by the trip of the ID fan, the PA and the SA as well as the ． 330B-SM8 Boiler Operation Manual Page 47 of 46 DCS system fault and the following procedures maybe followed: a) b) c) d) Adjust the baffler plate of the air fans to maintain the normal furnace negative pressure. Adjust the feed water flow to maintain the normal drum water level. To immediately find out the reason for the MFT If the reason for the MFT could not be found out in a short time or could not be solved and then the boiler maybe shutdown and keep it for re-startup under got state. Reason can be found out in short time and the re-startup the boiler as per the procedures for startup of the boiler under hot state. 2． ． If the MFT is caused by the trip of the ID fan, PA fan, SA fan as well as the DCS system in addition to the above procedures the local bed material piling up phenomenon and the fluidization problem maybe considered, the major phenomenon is as followings: a) One or more bed temperature displayed value is largely varied from the display of the other bed temperature. b) All the readings of the bed temperature is still without fluctuation. 3．The sequence of the self fluidization of the bed material: a) Changeover to the manual adjustment for the air volume supply. b) Immediately increase the PA air gate and then resume to its original position and check if the display of the bed temperature. c) After three times repeat in 10 minutes of the above operations could not help and then further discharge of the bed material to carry out the bed material fluidization. d) And then changeover the manual adjustment to Auto mode. 7.12 Attentions shall be taken for boiler overhaul 1. The regular inspection, adjustment and calibration of the equipment shall be made to guarantee the safety, reliability and high efficient operation of the equipment. ♦ The instrument and control equipment shall be maintained on the best operation condition. The equipment efficiency is depended on its performance. When planning the boiler overhaul, the primary measuring instruments and control system shall be calibrated, repaired or changed according to the actual needs. ♦ During the daily inspection of the boiler, the special attention shall be paid to the sealing 330B-SM8 Boiler Operation Manual Page 48 of 46 condition of the valves; the lubricant shall be applied every 6 months to the valve stem, or made in accordance with the requirement of the valve manufacturer. ♦ During boiler overhaul, all the startup burner, and the cleaning nozzle, atomizer, igniter and flame detector shall be inspected. ♦ After the boiler shutdown, inspection shall be made to all the erosive places, include the material inlet opening at the lower furnace, opening for material return, opening for SA, the joint between the refractory material and water wall tubes, water wall panel, superheater panel, anti-erosion casting material at the bottom of the reheat panel, inlet of the separator, internal wall of the separator, ceiling, enclosure of the HRA, heating surface at the boiler HRA, anti-erosion casing at the boiler HRA, and the anti-erosion tile. 2. All the inspection records, including the location, condition, data and the maintenance to the equipments shall be kept to dynamically control the equipment condition. Record the erosion data for different locations, and calculated the erosion velocity of time N-1,N and N+1, to prevent any problem from happening. ♦ During boiler stoppage, anti-erosion casing and anti-erosion tile of HRA shall be inspected and repaired. Any erosion, inclination of the casing will result in the unevenness of the flue gas, and accelerate the erosion problem in that area. ♦ For many locations inside the CFB boiler, refractory material shall be lined; regular inspection shall be made to maintain the integrity and insulation of the refractory lining. 3. The allowable erosion thinning of the refractory material at the high temperature insulation area shall be within 25mm, and the maximum allowable crack at the vertical tubes and the opening for material return is 50mm. the allowable erosion thinning of the refractory material at the openings for coal feeding and for material return is 50mm (the extreme condition is that the opening tubs of the membrane wall shall be exposed). ♦ The service life of the refractory material is influenced by the boiler startup and shutdown time, after the boiler is put into use, the cracks of the refractory material will be filled with the bed material, and each time during the boiler startup, the bed material filled into the cracks will influence the close of the cracks, and the cracks will expand. Therefore after boiler shutdown, the bed material inside the cracks shall be cleaned to extend the boiler service life. ♦ The hydrostatic test shall be made after repairing any pressure parts, before the water filling and the start of the test, the temporary support or block piece shall be provided to all the steam interconnecting tubes after the hydrostatic test and before the boiler ignition, 330B-SM8 Boiler Operation Manual Page 49 of 46 this temporary support or block piece shall be removed), to ensure that during water filling, the weight of water will not make the pressure parts go down, and to avoid the stress concentration. ♦ During the hydrostatic test, the metal temperature of the drum out wall shall not exceed 35℃. ♦ The drum material is low alloy high strength steel, to make sure the safety operation of the drum, arc strike, electrical connection, spot welding and welding is not allowed on the drum.