True or False questions (3 points each)
1. There are two standard methods for measuring boiler pressure, one is absolute pressure and the other is relative pressure, both are called gauge pressure. ( )
2. The water-cooled wall is a radiant heating surface arranged around the furnace. ( )
3. The newly purchased pressure gauge must be calibrated before use. ( )
4. Hot water boilers can also explode due to overpressure, so a safety valve must be installed. ( )
5. Do not supply water when the water level drops after the furnace tube is blasted. ( )
3. Multiple choice questions (3 points each)
1. The saturation temperature is related to the pressure. The higher the pressure, the saturated steam temperature ( ).
The lower A is; B is not necessarily the same; C remains unchanged; and the higher D is.
2. Set up ( ) at the end of the boiler to use the waste heat of the flue gas to heat the boiler feed water.
A air preheater; B superheater; C economizer.
3. The pressure gauge is generally calibrated ( ) at least once.
A half a year; B one year; C three months; D one month.
4. The valve in the closed position during normal operation is ( ).
A water level meter steam cock; B drain valve; C main steam valve; D pressure trap cock; E water level meter drain cock.
5. An accident in which the boiler pressure components are damaged and forced to stop operation for repair is called ( )
A explosion accident; B major accident; C general accident
4. Fill-in-the-blank questions (3 points each)
1. Boilers can be divided into power station boilers, boilers and boilers according to their uses.
2. According to the output medium, boilers can be divided into boilers for boilers, boilers for steam and water, and boilers for steam and water.
3. Boiler water circulation can be divided into two categories: circulation and circulation.
4. The boiler pressure gauge should be calibrated every one hour after installation, and the working pressure should be indicated on the dial.
5. The basic requirement for a stoker is to be one year old or above.
5. Short answer questions (5 points each)
1. What are the basic conditions for combustion? ?
2. Briefly describe the working principle of the boiler.
3. Briefly describe the structure of the boiler.
4. What are the necessary conditions for the boiler to be put into operation?
5. What are the inspection and preparation contents before boiler ignition?
6. What are the general procedures for normal boiler shutdown? What should be checked after shutting down the furnace?
7. Under what circumstances should the furnace be shut down urgently? What are the steps?
2. True or False Questions (3 points each)
1. X
2. √
3. √
4. √
5. √
3. Multiple choice questions (3 points each)
1. (D)
2. (C)
3. (A)
4. (B, E)
5. (B)
4. Fill-in-the-blank questions (3 points each)
1. Industry, life
2. Steam boilers, hot water boilers
3. Mandatory Cycle, natural cycle
4. Half a year, red line
5. 18
5. Short answer questions (5 points each)
1. What are the basic conditions for combustion?
Answer: ①Fuel, ②Higher temperature, ③Appropriate air.
2. Briefly describe the working principle of the boiler.
Answer: ① When fuel is burned in the furnace, its chemical storage energy is released in the form of heat energy, making the flame and combustion products (flue gas and ash) have high temperatures.
② The high-temperature flame and flue gas transfer heat to the working fluid (heating medium) through the "heating surface".
③The working fluid (heating medium) is heated, and its temperature rises or vaporizes into saturated steam, or is further heated into superheated steam.
3. Briefly describe the structure of the boiler.
Answer: It consists of boilers and furnaces as well as safety accessories to ensure safe operation, such as water level gauges, safety valves, pressure gauges, etc.
4. What work should be done to supply steam to parallel boilers?
Answer: ① For boilers with superheaters, the superheater outlet header trap should be closed.
② Open the economizer flue, close the bypass flue, and close the economizer feed water recirculation valve so that the boiler feed water and less flue gas pass through the economizer.
③Open the boiler continuous blowdown valve. For boilers equipped with automatic water supply regulators, put the automatic water supply regulator into operation and observe whether it operates normally.
④Rinse the water level meter again and compare it with the remote water level display and control device. Pay attention to monitoring changes in drum water level and steam pressure. Simultaneously observe and monitor each measurement and control instrument changes and indications.
⑤ Conduct an external inspection of each part of the boiler and start making boiler operation records.
5. What are the inspection and preparation contents before boiler ignition?
Answer: Inspection contents: ① Internal inspection before ignition. ②External inspection before boiler ignition. ③Inspection of safety accessories and various instruments. ④Inspection of steam and water pipelines. ⑤Inspection of combustion and auxiliary equipment. ⑥Inspection of boiler room and other aspects.
Contents to prepare: ① Fill the boiler with water. ②Oven.
Newly installed boilers whose pressure components have been overhauled or which have been out of service for a long time must be boiled before being put into operation.
6. What are the general procedures for normal boiler shutdown? What should be checked after shutting down the furnace?
Answer: The general procedure for normal boiler shutdown:
① First reduce the evaporation of the boiler, and then stop coal feeding.
② The mechanical grate should stop feeding coal to the boiler in advance. After all the coal in the coal hopper is sent into the furnace, stop the rotation of the grate; the pulverized coal furnace will grind all the coal in the coal mill into Pulverized coal is injected into the furnace until it is burned out (pulverized coal furnaces and boiling furnaces are shut down according to the temporary shutdown procedure). Then, remove all remaining coal in the coal hopper and close the coal gate.
③ When the fire reduces to a weak state, close the steam supply valve and stop the steam supply; when the coal is burned out, stop the blower and induced draft fan, and appropriately close the boiler outlet flue baffle and the lower part of the grate. The ventilation door is switched to natural ventilation to allow the coal on the grate to burn out. At the same time, the automatic water supply is changed to manual water supply to keep the boiler water level slightly higher than the normal water level.
④ Close the boiler outlet flue baffle, the ventilation adjustment door and the furnace door under the grate, and remove the slag on the grate (the mechanical grate starts the grate and sends the ash into the inside the hopper and continue running for about 1 hour to cool the grate), and remove the dust accumulated in the ash hopper and each air chamber.
⑤ When the boiler stops supplying steam, the isolation valve must be closed to isolate it from the steam main pipe. For boilers with superheaters, the superheater outlet header trap should be opened for 30 to 50 minutes to cool the superheater, and the continuous blowdown valve should be closed at the same time.
⑥ The steam pressure cannot drop too fast to cool the boiler quickly. When the steam pressure does not drop to atmospheric pressure, the operator should still monitor the boiler.
⑦ After shutting down, the boiler cools down slowly. After 4 to 6 hours, gradually open the flue baffle for ventilation. For boilers with bypass flues, the bypass flue should be opened and the cast iron economizer flue baffle should be closed, but the boiler water should still pass through the economizer; if there is no bypass flue, the economizer recirculation should be turned on Pipe valves and monitor the economizer outlet water temperature should be 40°C lower than the corresponding saturation temperature under boiler steam pressure. If the water temperature is higher than this temperature, you can appropriately use small amounts of water to cool down. After the boiler is shut down for 8 to 10 hours, if it is necessary to speed up the cooling, the induced draft fan can be started, and the number of times of water discharge and water filling can be appropriately increased. 18 to 24 hours after the boiler is shut down, all the pot water can be released only when the temperature of the pot water is lower than 70°C. In order to make the water discharge work go smoothly, the air valve of the drum should be opened or a safety valve should be raised.
⑧ After the boiler releases water, the steam, water supply, sewage and other pipelines should be completely isolated from other boilers running in parallel with blocking plates (blind plates) before entering the furnace for work.
Contents that should be inspected after shutting down the furnace:
① The flue should be purged once the furnace is shut down.
② After shutting down the boiler, a more detailed inspection of all parts of the boiler should be carried out, and equipment defects should be noted down for easy processing after shutting down the boiler.
③ During the shutdown operation, attention should be paid to water level changes at any time to avoid water shortage or water filling accidents.
7. Under what circumstances should the furnace be shut down urgently? What are the steps?
Answer: When encountering one of the following situations, the boiler should be shut down immediately:
① The boiler water level is lower than the visible edge of the lower part of the water level gauge;
② Keep adding water The large water supply pump takes other measures, but the water level continues to drop;
③ The boiler water level exceeds the highest visible water level (full water), and the water level still cannot be seen after draining the water;
④ Feed water pump All failure or water supply system failure, no water can be fed into the pot;
⑤ All water level gauges or safety valves fail;
⑥ Boiler components are damaged, endangering the safety of operating personnel;
⑦ The combustion equipment is damaged, the furnace wall collapses or the boiler frame is burned red, etc., which seriously threatens the safe operation of the boiler;
⑧ Other abnormal conditions endanger the safe operation of the boiler.
The operating steps are:
① Immediately stop coal feeding and air supply to reduce draft;
② Quickly remove the coal from the furnace and extinguish the fire;
③ Quickly close the main steam valve at the boiler outlet, open the exhaust valve and safety valve, and reduce the steam pressure;
④ After the fire is extinguished, open the economizer bypass flue block plate, close the main flue baffle, and open the ash door and furnace door to promote air circulation and accelerate cooling.
8. What are the maintenance contents of the boiler?
Answer: A. Boiler shutdown maintenance, including dry maintenance and wet maintenance.
B. Regular maintenance of boilers and first-level maintenance of boiler equipment. Generally, first-level maintenance is required once the boiler has been running for 1 to 3 months. Special components (such as water level meter leakage, lighting damage, etc.) should be resolved promptly during daily operation and maintenance and patrol inspections. The specific time, maintenance content and requirements of the maintenance cycle are:
① Shell boiler. If the evaporation capacity of the shell boiler is less than 1t/h, maintenance should be performed once a month; if the evaporation capacity is above 1t/h (including 1t/h), maintenance should be performed once every three months of operation.
②Water tube boiler. If the water tube boiler has an evaporation capacity of less than 1t/h, it should be maintained once every one month of operation; if the evaporation capacity is above 1t/h (including 1t/h), it should be maintained once every three months of operation.
③Quick installation of boiler. The quick-installed boiler should undergo first-level maintenance once every 3 months of operation.
C. Secondary maintenance of boiler equipment: Once the boiler equipment has been in operation for one year, secondary maintenance is required.
Boiler Examination Questions
1. What parts does a boiler consist of? Answer: A boiler is composed of a pot and a furnace. The pot is the part where water turns into steam, which is usually called the steam-water system. The furnace is the part where fuel and air are burned, which is usually called the combustion system. The boiler is the combination of the steam-water system and the combustion system. composed unity. The steam-water system usually consists of an economizer, a drum (steam drum), a convection tube bundle, a water-cooled wall and a superheater. The combustion system usually consists of a blower, induced draft fan, flue duct, coal feeding device, air preheater, combustion equipment, dust collector and chimney. In order to ensure the safe operation of the boiler, various safety accessories and measuring instruments are required: such as water level gauges, safety valves, pressure gauges, valves and control instruments. 2. What is the thermal efficiency of a boiler? Answer: The thermal efficiency of a boiler is usually expressed as the percentage of heat that is effectively utilized to the heat that should be released by the fuel in the boiler. The heat that is effectively utilized is the heat required to turn water into steam, or the heat used to increase the water temperature. Boiler thermal efficiency reflects the economic effect of boiler equipment. Similar boilers have different thermal efficiencies due to different use and maintenance. Therefore, work responsibility and operating level are important factors that affect the economic effect of boilers. Boilers should be serious and responsible for their work and strive for technical excellence. , burn the boiler for the country. 3. How to determine the minimum safe water level of the boiler? Answer: Determining the minimum safe water level of the boiler is to prevent the heating surface from overheating and burning and to ensure reliable water supply to the boiler's downpipe. Due to the different structures of the boiler, the method for determining the low safe water level of the fire guest boiler and the water tube boiler is: ( 1) The minimum safe water level of vertical horizontal water tube boilers should be 100 mm higher than the highest point of the furnace roof; (2) The minimum safe water level of horizontal block-mounted boilers should be 75 mm higher than the highest fire boundary of the boiler; (3) The minimum safe water level of all types of water tube boilers should be 300 mm higher than the end of the downcomer in the upper drum.
4. What safety accessories are provided on the boiler? Answer: There are three main safety accessories on the boiler: pressure gauge, safety valve and water level gauge. Since the three accessories can help the boiler strictly monitor and control the steam pressure and water level in the boiler, they are directly related to the safe operation of the boiler, so they are Called a safety attachment. 5. Under what circumstances should the pressure gauge stop being used? Answer: When the pressure gauge has one of the following conditions, it should be stopped to avoid affecting the safe operation of the boiler: (1) When the boiler has no pressure, the pointer of the pressure gauge cannot return to zero; (2) The surface glass is broken or the dial scale is blurred. ; (3) The pressure gauge has no lead seal, or has expired and has not been calibrated; (4) Air leakage or pointer jump in the gauge; (5) Other defects that affect the accuracy of the pressure gauge. 6. What is the function of the safety valve? Answer: The function of the safety valve is: when the steam pressure in the boiler exceeds the specified allowable working pressure, the safety valve can automatically open to discharge steam, causing the pressure to drop to avoid overpressure explosion accidents in the boiler. Safety valves commonly used in industrial boilers include lever type and spring type: (1) Working principle of lever type safety valve: When the force generated by the steam pressure in the boiler exceeds the pressure on the valve core, the steam will push the valve core When the exhaust steam is turned on, it will automatically close. When the exhaust steam pressure needs to be adjusted, it can be achieved by moving the position on the weight lever. That is, if the weight moves outward, the exhaust steam pressure will increase. If it moves inward, the exhaust steam will increase. Stress is reduced. (2) The working principle of the spring-type safety valve: the valve core is pressed by the tension of the compression spring. When the force generated by the steam pressure in the boiler is greater than the spring tension pressing on the valve core, the steam will lift the valve core. Automatically exhaust steam outward. When the steam pressure decreases, the spring presses the valve core down and tightly closes the valve seat. When the exhaust pressure needs to be adjusted, the adjustment screw on the spring can be tightened or loosened to increase or decrease the amount of steam. achieved by the force of the spring. 7. What are the common faults of safety valves? How to exclude? Answer: Common faults of safety valves include: (1) Steam leakage; (2) Steam is not exhausted when the specified opening pressure is reached; (3) Steam is exhausted when the specified opening pressure is reached; (4) After exhausting steam, the valve core Does not return to position. 8. What is the function of the water level gauge? How many types are there? Answer: The water level gauge is used to indicate the water level inside the boiler. The boiler monitors the water level in the boiler according to the instructions of the water level gauge to prevent water shortage or water filling accidents. Common water level gauges include glass tube type and glass plate type. For boilers with a higher drum position (more than 6 meters above the ground), low-level water level gauges are also used to facilitate observation of the water level. 9. How to use the water level meter correctly? Answer: When using the water level gauge, you should pay attention to the following matters: (1) Flush the water level gauge frequently to prevent scale and dirt from clogging the steam and water connecting pipes. When flushing the water level gauge, do not open or close it violently, but operate it evenly and slowly. , to prevent the glass tube from breaking; (2) The steam and water leakage of the water level gauge should be tight. If the steam leakage occurs during operation, the water level displayed by the water level gauge will be higher than the actual water level in the pot. If the water leakage occurs, When the water level is displayed, the water level displayed is lower than the actual water level in the pot. Therefore, when the water level meter is found to be leaking steam or water, it should be repaired in time to ensure the accuracy of the water level measurement; (3) The water level meter is clean and bright; ( 4) For glass-type water level gauges, after replacing the glass tube, you should first turn on the steam and water to preheat it to prevent the glass tube from exploding and injuring people due to sudden heating. 10. What is the function of high and low water level alarms? Answer: The high and low water level alarm is a protective device on the boiler. Its function is: when the water level in the boiler is too high or too low, it can sound an alarm to attract the attention of the boiler and take timely measures to prevent accidents. Boilers with a high degree of automation can also use it to cut off the power supply to the water pump or stop fuel combustion. 11. What valves are generally installed in boiler steam and water pipelines? Answer: The valves installed on the boiler steam and water pipelines include steam valves, water supply valves, check valves, blowdown valves, pressure reducing valves and steam traps, etc. 12. What issues should be paid attention to when installing and using the water supply check valve? Answer: When installing and using the water supply return valve, you should pay attention to the following matters: (1) When installing, the flow direction of the water supply should be consistent with the direction of the arrow on the check valve body, and the valve body cannot be installed backwards; (2) The water supply check valve must be It should be used in conjunction with the water supply stop valve, and do not install the check valve alone on the pipeline; (3) Lift or swing water supply check valves should be installed vertically on horizontal pipelines to ensure reliable action.
13. What issues should be paid attention to when installing and using a water trap? Answer: When installing and using a steam trap, you should pay attention to the following issues: (1) The form and specifications of the steam trap should be selected according to the amount of condensed water in the steam pipe or steam equipment; (2) The steam trap should be installed at the lowest point of the steam pipe. or the lower part of the bent pipe; (3) The steam trap should be equipped with a bypass pipe to facilitate maintenance. If necessary, this pipe can be used to directly discharge the condensate; (4) When installing the steam trap, pay attention to the direction of the arrow on the valve body. Do not install it backwards or tilt it. 14. How to cook the stove? Answer: The boiling work can be carried out immediately after the oven. The main purpose of boiling is to remove the oil stains and rust attached to the internal surface of the newly installed or overhauled boiler to avoid malfunction after the boiler is officially put into operation. The method of boiling the furnace is as follows: (1) The quantity of medicines used for boiling the furnace can be calculated by adding 2-5 kilograms each of sodium hydroxide and trisodium phosphate per ton of furnace water, and then melt the medicines with hot water, stir well, and prepare Add the 20% concentration solution into the boiler and feed water to the boiler to the highest water level; (2) Raise a slight fire in the furnace hall and boil the water in the pot. The steam generated can be discharged through the air valve or raised safety valve; (3) Keep the pot water boiling vigorously for 24 hours. When the water level decreases, you can add water with the same alkalinity to the boiler; (4) The boiling time should be determined according to different furnace types. After 24 hours of boiling for a small boiler, That is to say, the beacon fire is stopped, and after the pot water is cooled, all the water is released, and the manholes and hand holes are opened, and the dirt in the pot is washed away with clean water. The result of the boiler should be wiped with the inner wall of the boiler with hands or cotton gauze to reveal the Metallic luster is qualified. 15. How to supply steam? Answer: For a single operating boiler, after the steam pressure rises to the working pressure, the heating pipe work is completed, and the boiler worker gets in touch with the user and confirms that it is accurate and ready, then the steam supply work can be carried out. The operation method of steam supply is as follows: (1) Slowly open the main steam valve. When no abnormal sound is heard in the steam pipe, open the main steam valve wide. If there is water hammering sound in the pipe, open the main steam valve wide. After draining the condensed water, reopen the steam valve to supply steam. After the valve is fully opened, it should be closed half a turn to prevent the steam valve from being stuck due to thermal expansion; (2) After the official steam supply, The drain valve on the pipeline should be closed, and attention should be paid to changes in the boiler steam pressure and water level, and adjustments should be made in a timely manner. 16. How to clean the water level meter? Answer: Before flushing the water level gauge, you should pay attention to check the water level of the two water level gauges. When operating, you should move slowly and do not look directly at the water level gauge. The sequence of operations for flushing the water level gauge is as follows: (1) Turn on the water cock to flush the steam and water connecting pipes and glass tubes (plates); (2) Close the water cock and flush the steam connecting pipes and glass tubes (plates) separately ; (3) Turn on the water cock, close the steam cock, and flush the water connecting pipe separately; (4) Open the steam cock, close the water drain hose, and check the water level rise. If the water level rise speed, water line and other If the water level gauge is consistent and fluctuates slightly, it means that the water level gauge is in good condition. If the water level gauge rises slowly and the water line is inconsistent with another water level gauge and does not fluctuate, it means that the steam and water connecting pipes or corks of the water level gauge are still blocked. , should be flushed and inspected again. 17. How to verify the safety valve? Answer: The safety valve calibration method is as follows: 1. When calibrating the spring-type safety valve, you should first remove the outer cover, then use a wrench to adjust the screw to a position slightly lower than the exhaust pressure, and then gradually tighten the adjusting screw until The safety valve must exhaust steam immediately under the specified opening pressure. After the calibration is accurate, fix the position of the adjusting screw, install the outer cover and add a lead seal; 2. When calibrating the lever type safety valve, loosen the fixation of the weight first. screw, and then move the weight inward and place it at a position slightly lower than the exhaust pressure. If the safety valve exhausts steam before reaching the specified opening pressure, the weight can be gradually moved outward until the safety valve reaches the specified opening pressure. Until steam exhaust, after the calibration is accurate, tighten the weight fixing screw to fix it, and then add a lead seal. When inspecting the safety valve, attention should be paid to the following matters: (1) Before calibration, attention should be paid to checking whether the safety valve and exhaust pipe are in good condition, the pressure gauge must be accurate and reliable, and the boiler water level must be between the normal water level and the lowest water level; (2) During the inspection, the boiler pressure should rise slowly to avoid accidents caused by a sharp increase in pressure; (3) During the inspection, attention should be paid to preventing burns. If the safety valve is inflexible or inactive, it is strictly forbidden to hit it with a hand hammer; (4) After the calibration work is completed, the boiler pressure should be raised to the specified opening pressure and another automatic exhaust test should be conducted. When it is confirmed to be qualified, a lead seal should be added and calibration records should be kept.
18. How to discharge sewage? Answer: The operation method of sewage discharge is as follows: (1) Before discharging sewage, you must check whether the sewage valve and sewage pipe are in good condition; (2) When discharging sewage, after opening the valve, there should be no impact sound in the sewage pipe. If there is impact sound, close the valve until Open the large valve after the impact disappears; (3) During the blowdown process, pay attention to monitoring the changes in the water level of the boiler to prevent missing accidents; (4) After the blowdown is completed, close the blowdown valve for a period of time, and then based on the sound in the blowdown pipe, Confirm whether the sewage discharge has stopped, or touch the temperature of the sewage pipe with your hands to determine whether the sewage valve is closed tightly. Things to note when blowing down sewage: (1) If two or more boilers use one sewage pipe, it is strictly prohibited to blow down sewage at the same time; (2) The best time to blow down sewage is when the load is low and the water level is high. 19. How to keep the main accessories of the boiler sensitive and reliable? Answer: The pressure gauge, safety valve and water level gauge on the boiler are called the three major safety accessories on the boiler. Whether these main accessories are sensitive and reliable during boiler operation is very important to ensure the safe operation of the boiler and prevent accidents. It must be done To do this job well, the boiler should operate according to the following methods: (1) Pressure gauge: flush the water trap regularly to prevent blockage and failure. For boilers equipped with two pressure gauges, the pressure values ??indicated by the two gauges should be checked frequently. If the indicated pressure is different, check the cause immediately and eliminate it. In order to keep the pressure gauge sensitive and reliable, send the pressure gauge to the measurement department for verification at least once every six months and add a lead seal; (2) Safety valve: every shift Or a manual steam exhaust test should be done once a day (pull, lift, and release gently during operation), and an automatic steam exhaust test should be conducted once a month to prevent the valve core and valve seat of the safety valve from sticking, causing malfunction. At the same time, pay attention to check whether the lead seal of the safety valve is intact and whether the weight on the lever safety valve has been moved or a heavy object has been added; (3) Water level gauge: It must be flushed at least once per shift to ensure the indication. The water level must be accurate and reliable. If it is found that the water level displayed by the glass tube (plate) is abnormal, the water line has stopped or the boundary is unclear, it should be flushed in time. Pay attention to daily maintenance to prevent the leakage of steam and water in the water level meter. . 20. How to shut down the furnace completely? Answer: To completely shut down the boiler, follow the following methods: (1) Stop supplying fuel, stop supplying and drawing air, and close the flue baffle and the ventilation door and ash door under the grate; (2) Feed water to the boiler to the highest water level; (3) When the steam pressure drops to zero, the windshield and gray door can be slightly opened for ventilation and cooling. At the same time, water supply and discharge can be performed alternately to gradually reduce the water temperature in the pot. When it drops to 70°C (hand The pot shell or head does not feel very hot to the touch) Drain all the water in the pot. Before draining the water, you should first open the air valve on the boiler or lift the safety valve; (4) After the boiler has drained all the water, if there is any parallel operation For boilers that are out of service, the steam and water pipes of the out-of-service boiler should be blocked by blocking plates to facilitate access to the boiler for maintenance; (5) The cooling down of the boiler must be kept slow to avoid rapid cooling, which may cause damage to the boiler.
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