A combined cycle unit steam turbine intermediate pressure cylinder into cold cause the event holding shaft

A combined cycle unit steam turbine intermediate pressure cylinder starting into the cold lead to 2021 - holding shaft events 02 - 01, the occurrence of the incident on March 18, at 8:30, # 1 gas turbine is scheduled to start up, run on duty personnel to perform the # 1 combined cycle unit operation. Chariot, operators open low export electric warming pipe, as full open. Came, # 1 gas turbine interconnection with the initial load 20 mw, gas turbine running stability. Rev machine after the turbine speed by turning speed, 49 rpm) Rise gradually. 8:42:23, turbine speed rapid decline after the highest up to 100 RPM. 8:43:30, turbine speed to 0 RPM, check intermediate pressure cylinder and cylinder temperature difference is bigger and has increasing trend, Medium pressure cylinder cylinder temperature 235 ℃ is kept constant, the cylinder temperature decreased from 223 ℃ to 195. 5℃） 。 27, judge intermediate pressure cylinder into the condenser, long-term value to # 1 gas turbine manual hits the brake. At 8:45, # 1 generator and system solutions. Immediately notify operators with tools to the scene manually turning, plate. 8:46 a. m, the value of long notice to perform the unit # 1 turbine boring cylinder measures: closing high, medium and low electric door and reheater export electric door, open the high voltage, medium voltage, low voltage main steam pipeline dredging watergate, high voltage, medium voltage, low voltage main steam pipe pressure to 0 mpa, damage the vacuum kpa 0, A and B vacuum pump, back # 1 machine shaft seal steam; Intermediate pressure cylinder body thin gate closed after 10 minutes. Second, check the situation 1, consult the history curve parameters and process analysis, operation personnel opened lower after warm tube operation on export of electric door, under the intermediate pressure cylinder cylinder temperature began falling fast, in combination with had already found that low pressure main steam door shut imprecise problems (and tone No chance for processing after transfer operation) Cold vapor, determine the pipe through the low voltage main valve, tone imprecise place into the intermediate pressure cylinder exhaust port. The process analysis and parameter change trend is shown in figure 1. 2, interlock protection action in the process of normal downtime, on-site inspection jacking oil pressure, oil pressure is normal, the steam turbine rotor plate fixed manually. Continuously perform # 1 unit turbine boring cylinder measures: to open every two hours by the regulation turbine ontology in thin gate # 1 machine, hydrophobic closed 2 minutes, and close to the corresponding manual door. On March 22, little, the # 1 machine in continuous turning, the data is normal, restore backup unit. Figure 1 process analysis and parameter change trend in figure 3, the preliminary inspection of low voltage automatic main steam door, found the closed position has reached the position of mechanical protection, monomer debugging tend to retain a little allowance, when the valve mechanical position and adjust the space, need further disintegration check thoroughly. Three, cause analysis 1, # 1 steam turbine low pressure automatic main steam door shut is not strict, and tone in the unit operation to the low voltage main steam pipe warm, with cold vapor by importing retrograde streaming into the intermediate pressure cylinder low pressure cylinder internal ( In the low pressure cylinder cylinder) , leading to medium pressure cylinder, cylinder temperature difference is big, cause local deformation of cylinder, dynamic-static gap reduced or even disappear, cause of dynamic and static friction, the rotor disc droop to 0 RPM, immobilized. 2, automatic operation personnel did not fully understand low pressure main steam door shut imprecise and tone of the risk of major no advance for low pressure main steam pipe fully hydrophobic plumbing, caused by low temperature steam automatically by the low voltage main steam into the intermediate pressure cylinder door to tone and imprecise. Four, exposed the problem 1, operation department of the # 1, 2 unit measures to prevent steam turbine cold water into steam, not perfect, not for the main valve and found that low pressure before automatically close tone imprecise defects fully 辧 general risk, not laying targeted prevention and control measures of risk. 2, boosting and sequence control system in the original design have a drum temperature, if according to the logic sequence control can avoid the problem, but due to improper sequence control parameter is set to input, make the operation personnel to adopt manual operation, increase the risk of operation. 3, run the loopholes in management, standard operation ticket is imperfect. February 4, stock company has issued by the similar event notification, power plant related professional and technical personnel not serious organizational learning, introspection, draw lessons from. Five, improvement of 1 / preventive measures, timely find downtime opportunities, thorough treatment # 1 steam turbine low pressure main steam door shut imprecise and tone defects, prevent the rev. Stop the process steam cold cold water into the medium and low pressure cylinder. 2, before the defects did not eliminate, run deep in risk identification, further improve the measures to prevent cold vapor in the cold water enters the low pressure cylinder, prevent similar incidents from happening again. 3, improve the drum unit heat booster sequence control logic, as far as possible to prevent human error caused from the intrinsically safe equipment unsafe events, extrapolate check other thermal problems of logic, after professional discussion to improve as soon as possible. 4, the use of downtime, maintenance staff actively carry out relevant equipment inspection work, including the main steam pipe of the drain pipe, valves, comprehensive inspection. 5, to conduct a comprehensive reorganization of operation and management, improve and refine the operation ticket, carry out skills training, improve the technical level and emergency disposal ability of the operators. Source: turbine supervision ( ID：qijijiandu）