Cause, harm and preventive measures of water ingre

2022-07-24
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Causes, hazards and preventive measures of water inflow in main engine oil

the exhaust condensing steam turbine generator unit adopts an electro-hydraulic control system, and the unit lubricating oil and control oil are the same oil source. Since it was put into operation, there have been many times of shaft seal steam leakage into lubricating oil, resulting in deterioration of oil quality, which has seriously affected the safe and stable operation of the unit

1 the main cause of water inflow in the oil

(1) the radial clearance of the shaft seal is adjusted too large, and the steam leakage of the shaft seal flows into the bearing chamber along the shaft, resulting in water in the oil. During the unit maintenance, in order to avoid the shaft system rotating at high speed during the start-up process from rubbing the shaft seal sharp teeth due to over critical speed vibration or rotor thermal expansion. Generally, the shaft seal clearance is increased when adjusting the shaft seal. During the normal operation of the unit, the tightness of the shaft seal is affected, resulting in the leakage of the shaft seal into the bearing chamber along the shaft, which is the fundamental cause of water in the oil

(2) the shaft seal teeth fall down and the sealing effect is reduced, causing water to enter the oil. During the adjustment of shaft seal radial clearance, considering the rotor expansion and incomplete shaft system vibration, the shaft seal radial clearance is too small, which causes the shaft seal sharp teeth to rub against the rotor due to rotor expansion and shaft system vibration during the unit startup, resulting in sharp teeth lodging and reduced sealing effect, resulting in shaft seal steam leakage and steam channeling into the bearing chamber along the shaft

(3) the steam supply pressure of shaft seal steam inlet header is too high, which makes the shaft seal chamber become positive pressure, resulting in shaft seal air leakage

(4) the extraction pressure of the shaft seal steam extractor is insufficient, and the extraction pipe is blocked, resulting in insufficient negative pressure, which makes the steam blow out along the shaft, resulting in shaft seal steam leakage

(5) the suction effect of the turning gear or coupling rotating blast causes local negative pressure in the bearing box and sucks steam. In addition, the output of the smoke exhaust fan in the bearing room is too large, which increases the negative pressure of the bearing room and makes the shaft seal leak steam. Its purpose is to unload the load and make the oil pressure of the working oil cylinder drop quickly into the lubricating oil system as long as conditions permit

(6) the inborn problem of poor expansion of the high and intermediate pressure cylinders of the unit has plagued the unit operation for a long time. When the unit is started, the No. 3 bearing pedestal is tilted forward and the No. 2 bearing pedestal is tilted backward. When the shaft system of the unit passes the critical speed and vibrates only one eighth of the aluminum, both determine the oil baffle clearance of the bearing box. Sufficient consideration must be given to the clearance adjustment, otherwise the sharp teeth of the oil baffle will be abraded. How to use the wood testing machine equipment will cause excessive oil baffle clearance, Make it easier for shaft seal steam leakage to enter the bearing chamber

(7) the joint surface of the cylinder is deformed and the seal is not tight, resulting in steam leakage and entering the bearing chamber, causing water in the oil

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