Causes and Solutions of Vacuum Reduction in Vacuum Pump System
Reasons for the slow decline of vacuum:
(1) Vacuum system is not tight.
(2) The water level of the condenser rises.
(3) The amount of circulating water is insufficient.
(4) Abnormal operation or low efficiency of the air extractor. It can be seen that every 1.3 kPa vacuum load drop by 1.2 mw, for a 12 MW unit, the load drop by 10%, you can imagine how great the loss is.
It is necessary to understand the characteristics of vacuum drop in condenser, analyze the causes of vacuum drop and correct treatment methods. Exhaust steam temperature increases. Vacuum gauge indication decreases. The end difference of condenser increases. Under the condition of constant valve opening, the load of steam turbine decreases. When using steam ejection, the amount of steam coming from the exhaust nozzle is usually increased.
When finding out the cause of the vacuum drop of steam turbine, we must start with the system, equipment, pipeline, valve and meter connected with the condenser. When the vacuum drop of the condenser is found when a guide of barnyard barnyard baking is broken by John, the attendant should quickly check the vacuum meters and the temperature of the exhaust chamber and make the following checks after confirming that there is no mistake: check the pressure inside the equalizer and the working condition of the water jet pump. Check condensate pump outlet pressure, current and condenser water level. Check the temperature and pressure of the circulating water outlet. Check whether the vacuum system valves, flanges, etc. are leaking. Check whether the inlet and outlet gate of low pressure heater has not been adjusted when the unit load changes. Causes and Solutions of Vacuum Unit Vacuum Reduction
Treatment of vacuum drop when circulating water is insufficient or interrupted:
(1) If a circulating pump is running, the standby circulating pump should be started to increase the water supply.
(2) When the vacuum drops due to fouling on the water side of the condenser, it should be cleaned.
(3) When the vacuum drops rapidly and the circulating water is interrupted, the load should be reduced immediately in order to supply water to the condenser by standby water source. If the interruption of circulating water causes the action of the exhaust valve, the circulating water population valve should be shut down and closed. Only when the temperature of the exhaust chamber drops below 50 C, can water be transferred to the condenser.
Processing methods for condensate pump failure and water level rise of condenser:
(1) To confirm the failure of condensate pump in operation, the standby pump should be started immediately. If the standby pump can not be connected, the load should be reduced to o immediately, otherwise the vacuum should be stopped when it falls to the prescribed value.
(2) When the water level of the condenser rises, the opening of the condensate water recirculation valve and the closure of the condenser water supply valve should be checked.
(3) Chemistry should be notified if the copper tube of condenser is broken, the hardness of water quality should be analyzed, and measures should be taken to stop the machine to find the leaking copper tube.
Treatment of vacuum drop caused by imprecise vacuum system:
(1) Insufficient and damaged valves should be repaired immediately.
(2) The leak is temporarily blocked with butter glycerol.
(3) If the vacuum of low load decreases and the vacuum rises when the load increases, the general reason is the leakage of the low-pressure extraction pipeline or the low-pressure cylinder joint surface, which can increase the unit load appropriately.
(4) If the vacuum drop is affected by the low pressure of the seal, the new steam valve can be opened for adjustment.
(5) Check the water-jet pump and the water-jet pump. The surface pressure of the air-pump population is not less than 0.294 mpa, and the water temperature of the water-jet tank will increase and the water will overflow.
(6) Taking the above measures, Roots water-ring vacuum unit should reduce its load when the vacuum still falls below 86.66 kpa, and shut down when the vacuum falls to 66.26 kpa. Valves, traps, pipes, etc. connected to the vacuum system.
Condenser copper tube and expander. The hydrophobic expansion vessel, pressure equalizer and other equipment connected with the condenser. The water-filling test was carried out on the condenser of two turbines. More than ten leakage points were found in the glass tube water level meter of low-pressure heater, the drain door of low-pressure heater, and treated one by one. The vacuum of the condenser reaches 72 kPa when the engine starts parallel with the front load. After careful inspection, it is found that the asbestos pad leaks from the exhaust air of the low pressure cylinder, the vacuum reaches 81 kPa after changing the pad, and the vacuum reaches 89kpa when the engine is fully condensed. After irrigation test, although the vacuum tightness is greatly improved, the vacuum is not ideal compared with the same working condition. After further inspection, it is found that the condenser follows the same pattern. The butterfly valve opening between the annular water outlet pipe and the second cooling tower is too small, resulting in poor circulation of circulating water and poor heat dissipation effect, thus affecting the vacuum. After opening the large butterfly valve, the vacuum of the condenser reaches 93 kpa, the vacuum level is raised, and the economic benefit is improved accordingly.
There are many factors affecting the vacuum level of steam turbine in actual operation, including the temperature and flow rate of cooling medium, the exhaust volume of the unit, the heat transfer of condenser, the tightness of vacuum system and the working condition of the extractor, etc. Therefore, the changes of various parameters should be closely monitored during operation, and corresponding adjustments should be made according to the actual situation to prevent the vacuum deterioration of the condenser from affecting the unit. Safe and economical operation.
Liquid ring vacuum pump system