Turbine vacuum drop

The oil quality has declined, causing scaling on the oil side of the condenser.

First, confirm that the table is good! Next, check the integrity of the system to see if there are any leaks! ! Check parameters such as the hot well level again. . . . . .

The level of the hot well fluid is normal, and the gauge readings are good as well. The airtightness has not been thoroughly checked yet. What other possible reasons could there be?

Let’s check the airtightness with a candle first!

Check for any leaks, and see if the vacuum pump is clogged. Check the circulating water as well; it’s possible that the condenser is blocked. Also, inspect the shaft seal

Well, let’s wait until the airtightness check is done; we’ll rule out each item one by one! ! !

Check the check valve of the standby pump, as well as the air pipeline of the pump and the cooling efficiency of the vacuum pump. Atmospheric safety valve sealing water and sealing performance

(1) Causes and solutions for a sudden drop in vacuum: 1. Interruption of circulating water – The fault of an interrupted circulating water supply can be determined by the operating condition of the circulation pump. If the current of the circulation pump motor and the pressure at the pump outlet drop to zero, it can be confirmed that the circulation pump has tripped; in such a case, the backup circulation pump should be started immediately. If the pump trips due to forced operation, check whether the pump is running in reverse ； If reversed, forced closing is strictly prohibited to avoid motor overload and shaft breakage. If there is no backup pump, the load should be quickly reduced to zero and the machine stopped. Fluctuations in the outlet pressure of the circulation water pump and the motor current are usually caused by an excessively low water level at the suction inlet of the pump or blockages in the strainer. In such cases, measures should be taken as soon as possible to raise the water level or remove the debris. If the outlet pressure of the circulation pump and the motor current decrease significantly, it may be caused by a fault in the circulation pump itself. If the outlet of the circulation pump closes accidentally while it is in operation, or if the outlet valve of the standby pump closes accidentally, causing the circulation water to flow back, this will also lead to a sharp drop in vacuum. 2. Abnormal operation of the jet pump: If both the outlet pressure of the jet pump and the motor current drop to zero, it indicates that the jet pump has tripped ； If the pressure and current of the water pump decrease, it indicates a fault with the pump itself or that the water level in the tank is too low. In such cases, the backup water-jet magnet and water-jet exhaust pump should be activated, and water should be added to bring the water level back to normal when it is too low. 3. Full water in the condenser: The condenser filling with water in a short period of time is usually caused by severe leaks in the copper tubes of the condenser, allowing large amounts of circulating water to enter the steam side, or by a fault in the condensate pump. The solution is to immediately open the water level control valve and start the backup condensate pump. If necessary, the condensate can be drained into the gutter until the water level returns to normal. Copper pipe leakage is also manifested as an increase in condensate water hardness. At this point, the leaking condenser should be stopped; in severe cases, the entire plant must be shut down. If the condensate pump fails, it can be determined from the outlet pressure and current. 4. Interruption of steam supply to the shaft seal: If the pressure of the steam supplied to the shaft seal drops to zero or becomes slightly negative, it indicates an interruption in the steam supply to the shaft seal. The possible causes include a malfunctioning pressure regulator for the shaft seal, a detached valve element, or water entering the steam seal system. At this time, the bypass valve of the shaft seal regulator should be opened to check whether the deaerator is filled with water (when the steam for the shaft seal comes from the deaerator). If it is full of water, quickly lower the water level and switch to the alternate steam source for the shaft seal. (II) Reasons for the gradual decline in vacuum and corresponding solutions: Due to the large scale of the vacuum system and the many factors that can affect the vacuum level, it is difficult to identify the cause when the vacuum decreases slowly. It is advisable to check the following items and take appropriate actions. 1. Insufficient circulating water volume: An insufficient circulating water volume is manifested by an increased temperature difference between the inlet and outlet of the condenser’s circulating water under the same load; this may be caused by debris entering the condenser and causing blockages. For a unit equipped with a gum ball cleaning device, backwashing should be performed. For units with siphoning in the condenser outlet pipe, it is necessary to check whether the siphoning has been disrupted; the signs of this are a vacuum level of zero on the condenser outlet side, along with an increase in the pressure at the condenser inlet. In such cases, the auxiliary extractor of the circulating water system should be used to restore the vacuum at the outlet; if necessary, the amount of circulating water flowing into the condenser can be increased. An increase in the temperature difference between the inlet and outlet of the condenser can also be caused by air accumulation in the circulating water outlet pipe or severe scaling of the copper tubes. At this time, the air release valve on the outlet pipe should be opened to remove air, or a rubber ball cleaning device can be used for cleaning; if necessary, high-pressure water can be used for flushing after shutting down the system. 2. Rise in condenser water level. The reasons for an increase in the condenser water level may include vaporization at the inlet of the condensate pump, or leaks in the condenser copper tubes allowing circulating water to enter. Vaporization at the inlet of the condensate pump can be detected by a decrease in the current flowing through the pump. Once it is confirmed that this is the cause of the rise in the condenser water level, it is necessary to check whether the packing at the pump inlet is not tight enough, allowing air to leak in. A cracked copper tube in the condenser can be detected by checking the hardness of the condensate water. 3. Increase in operating water temperature of the water jet pump: An increase in the operating water temperature raises the pressure in the pumping chamber, thereby reducing the efficiency of the pump. When an increase in water temperature is detected, industrial water should be added to reduce the temperature of the working water. 4. Air leakage into the vacuum system: Whether air is leaking into the vacuum system can be checked through a leak test. Furthermore, air leaking into the vacuum system is also manifested as an increase in the subcooling of the condensate water, as well as an increase in the temperature difference at the condenser side.

Vacuum – I thought it was simple, but actually it does require some knowledge! Check the extractor nozzle and filter screen; for the rest, follow the operating procedures

The technician on the 9th floor gave a very comprehensive answer, eliminating possibilities one by one based on the degree of vacuum drop.