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:Why is the temperature of the exhaust cylinder higher at no load than when under load? Why does it remain around 120°C at no load, while it is around 60°C under load? This is because during normal operation, the steam flow is high and the exhaust steam is in a saturated state; if the exhaust temperature rises, the exhaust pressure also increases, resulting in an increased heat load per unit area of the condenser and a decrease in vacuum. The expansion joints of the condenser copper tubes may also become loose and start leaking, so the exhaust temperature should be around 60°C when the unit is under load. At no-load conditions, due to the low steam flow, along with the throttling effect of the valves and the friction caused by ventilation, the exhaust gas is in a superheated state; however, the exhaust pressure is not high at this time, and the vacuum can still be adjusted. As a result, the expansion joints of the condenser copper tubes are not subjected to excessive thermal stress and thus are not damaged. Therefore, the exhaust temperature can be allowed to be higher – around 120°C at no-load conditions – but care must be taken regarding the cooling water for the exhaust cylinder. II: What are the hazards of operating the low-temperature heater without water level? Low-level heater water level: 1. A certain water level should be maintained during the operation of the low-pressure heater, which can improve thermal efficiency. 2. Operation of the low-temperature heater without water level can easily cause vibration in the drain pipes and water hammer, affecting thermal efficiency and equipment safety.3 Hydrophobic substances entering the condenser affect the vacuum and increase the workload on the condenser, resulting in significant losses in thermal efficiency. From a safety perspective, too low a water level leads to foaming, severe erosion of the tube bundle, and increased vibration of the tubes, which can cause fractures in flanges, welds, etc., thereby reducing the service life of the drain pipes. Secondly, from an economic perspective, some of the steam will flow into the next stage of heater through the drain pipes, which reduces the thermal efficiency of that heater and thus lowers its economic viability. Additionally: High- and low-pressure heaters should operate at a certain water level; if the water level is too low, some of the steam will enter the next stage of the heater before it has had time to condense. This reduces the efficiency of the heater, and it can also cause damage to the drain pipes as well as the steel tubes in the next stage of the heater, which is detrimental to the equipment. It displaces the lower-stage extraction steam, reducing the regenerative effect. Excessively high water levels can submerge the steel pipes, reducing the heat transfer area and preventing optimal utilization of thermal energy, which in turn affects the thermal efficiency of the cycle; in severe cases, it can lead to water entering the turbine. Therefore, high- and low-pressure heaters should operate at an appropriate water level. If the water level in the upper-level heater is low (there is water present), then there are more heat transfer tubes in that upper level, and the temperature of the drain water at that level becomes lower. As a result, the increase in temperature of the water in the current level heater decreases, while the increase in temperature of the water in the upper-level heater should increase. In actual operation, it is generally not very noticeable. Third: The vacuum level is high when the load is high; conversely, it is low when the load is low. This is a normal phenomenon. When the load is low, and the temperature and flow rate of the cooling water remain unchanged, the vacuum level increases. In such cases, more air will leak in through the valves and flanges that are under vacuum, which affects the vacuum level – sometimes even causing it to drop. This issue can be resolved by controlling the flow rate of the circulating cooling water. There are definitely leaks present. Because the higher the load, the greater the steam inflow, and the \"leak points\" are thus more tightly sealed by the steam; as a result, the vacuum level of the unit is higher. Conversely, this will result in a larger \"leak\" and a lower vacuum level. A similar situation occurred in the units at our plant as well; upon inspection, it was found that there was a \"gap\" at the interface between the steam inlet of the #4 low-pressure heater and the low-pressure cylinder, which served as a leakage point. IV: Jamming of the sales system – what impact does it have on the expansion difference? ； How can you tell if the slip pin system is stuck? During the start-up and shutdown of the unit, a sudden increase or decrease in the absolute expansion value of the cylinder indicates that there is a jam in the slip pin system. 5: Methods to reduce auxiliary power consumption – The key is for the turbine to increase the vacuum level! Basic methods to reduce auxiliary power consumption: 1. Adjust the operating time of less critical motors (the focus should be on maintaining the health of the equipment, selecting appropriate equipment, and ensuring proper installation and maintenance) ； 2. Under low-load operation, try to use one or two electric feedwater pumps (depending on the actual load requirements specified by the plant’s units and the control room) ； 3. The boiler team should adjust the coal supply and air (oxygen) supply as precisely as possible, in order to achieve the highest economic efficiency of the coal grinding system and combustion system. They must work together with the turbine team to ensure proper regulation of main steam pressure, temperature, and vacuum – something that requires extensive familiarity with the plant’s equipment and significant practical experience, making it a rather challenging task. ) 4. Improve the quality of coal to ensure complete combustion of the fuel; comprehensive insulation measures for the boiler should be implemented. This not only reduces the amount of oil used but also decreases the number of starts and stops of the motors in the coal grinding system. 6: What is the relationship between #1 shaft addition and the vacuum system? The negative pressure introduced by #1 shaft addition helps to prevent steam leakage from stage 2, while also recovering the steam that leaks from stage 1 as well as the air that inevitably gets in through the outer stages. In other words, the steam source for the shaft seal is a mixture of steam and air; this air is directed directly or indirectly into the condenser via #1 shaft. Under normal conditions, #1 shaft is kept at a slight negative pressure. Changes in water level or pressure will certainly affect the vacuum level – when the water level drops, the negative pressure increases, which leads to more air flowing from the shaft seal to the condenser through #1 shaft, thereby causing changes in vacuum. Conversely, when the water level is high, the negative pressure decreases or even turns positive, resulting in steam escaping from the shaft seal and wasting process fluid. 7: Issue with steam supply for shaft seals – it isn’t activated even during hot start-ups when the cylinder temperature is below 300 degrees. Is this reasonable? The shaft seal has two functions. At the high-pressure end, it is to prevent high-pressure steam from leaking out from the shaft end. The low-pressure side is there to prevent air from leaking in from the shaft end. During normal operation, if the air leakage at the high-pressure side is not severe, it is possible to omit the use of the high-pressure side. But the low-voltage side usually needs to be connected. When it’s hot, should vacuum be drawn without installing an axis seal? I’m not quite able to understand this. Because when you draw air in, there is no pressure inside the engine; in other words, it cannot seal the high and low shaft ends on its own. If you don’t inject it, won’t the cold air leak into the turbine through the high and low axes? Once cold air gets in, the rotor cools down rapidly – won’t the main shaft bend? Our procedures strictly prohibit vacuuming while the shaft seal is not in use when the system is hot. . . That’s how it should be. In normal operation, it’s also possible to use the shaft seal on the high-pressure side, but it’s necessary to closely monitor the axial displacement and the increase in high-pressure difference. In fact, given the high leakage pressure associated with the shaft seal on the high-pressure side, there’s no need to use it ； What you mean is probably \"hot start\" where the temperature of the inner lower wall of the high-pressure cylinder is greater than 350 degrees! At that time, the cylinder temperature was high; the steam seal could not be supplied with steam from a temperature regulator. A high-temperature steam source was necessary, otherwise the negative pressure difference would increase beyond control. 8: How does thermal stress change during startup? What types of forces act on the cylinder? During startup, as the cylinder is heated, there is thermal compressive stress on its inner wall, while thermal tensile stress exists on its outer wall. In addition, the forces to be endured are the force exerted on it by steam resulting from pressure differences inside and outside, as well as its own weight. Other forces can be ignored. If it is a hot-start, such as when the pipes are not warmed up sufficiently or the steam temperature is low, the cylinder may be in a cooling process. The force applied is the opposite of the one mentioned above. 9: What is the purpose of shutting down the machine to disrupt the vacuum? What are its disadvantages? The purpose of breaking the vacuum is to reduce the rotor’s coasting time by increasing frictional losses. When the vacuum is not disrupted, after cutting off the steam supply to the turbine, the rotor continues to rotate in a medium with very low vacuum density, and it can maintain this rotation for a long time ； When the vacuum is broken, the frictional resistance and braking torque in the cylinder increase by many times, and the time it takes for the rotor to stop rotating is reduced by more than two times. The disadvantage of disrupting the vacuum shutdown is that cold air entering the rotating turbine causes rapid cooling of the rotor and the inner surfaces of the cylinders, as air, with its higher density, has a much greater heat transfer coefficient to the metal walls than steam at only 0.005 MPa. Such rapid cooling of the flow path in steam turbines is particularly undesirable in ultra-high pressure and supercritical pressure units. Therefore, this method of shutting down is applied only in those special cases where continued operation of the turbine could lead to further damage. What does water-hydrogen-hydrogen mean regarding the generator’s cooling method? Generator cooling method: water-hydrogen-hydrogen. a. The stator windings (including stator coils, stator leads, and stator terminals) are cooled by water. b. Hydrogen internal cooling for the rotor windings. c. The stator core and structural components are cooled by hydrogen surface cooling. 11: The principle behind closing the high-pressure throttle when the speed reaches 2800 revolutions per minute at startup. Before the speed control throttle operates, it is in an fully open state; the automatic main steam valve controls the amount of steam supplied, thereby adjusting the speed of the unit. At this time, the speed control throttle remains fully open because no pulse oil pressure has been established yet – the throttle slide valve and synchronizer fall to their lowest position under the action of the upper springs, and the pressure oil enters the upper part of the actuator, keeping the throttle fully open ； As the rotational speed increases, the pulse oil pressure rises gradually, causing the synchronizer spool and the throttle spool to move upward in order to control the pressure oil. When the pulse oil pressure at the lower part of the throttle spool balances the pre-tension force of the spring at the upper part, the hydraulic actuator stops operating. The pre-tension of the 2800 rpm throttle control valve and the throttle spring is related to the position of the synchronizer; adjusting these two elements can change the operating speed