Anti accident measures for the hottest steam turbi

Anti accident measures for steam turbine

because the steam turbine works under high temperature, high pressure and high speed, and there are various auxiliary equipment and auxiliary systems working in coordination, accidents often occur due to carelessness in a certain ring, which affects the smooth progress of commissioning work. There are many reasons for the accident. Such as the gap change of dynamic and static parts under thermal state, the vibration during startup and load change, and the change of axial thrust. Changes in steam parameters, abnormal operation of oil system and various hidden dangers may cause accidents if they are not found and handled in time. Therefore, effective measures should be taken to eliminate accidents in the embryonic stage during startup and test run

several common typical accidents of steam turbine and their monitoring, analysis and treatment methods:

8.1 during operation, the vacuum of condenser decreases:

the vacuum decreases and the exhaust temperature increases, which is easy to deform the exhaust cylinder, offset the center of the unit, cause the unit to vibrate, and the copper tube of condenser loosens, deforms or even breaks

during the test run, it should be monitored at any time. If it is found that the temperature of the exhaust chamber increases, the vacuum indication decreases, and the steam output of the air extractor increases, the load should be reduced first to find out the cause

causes and treatment of vacuum drop:

8.1.1 circulating water interruption or insufficient water supply: find the circulating water system, mainly check the circulating water pump and all electric valves

8.1.2 rear shaft seal steam supply interruption: find out whether the steam supply pressure changes, the steam with water interrupts the shaft seal steam supply, the shaft seal pressure regulator fails, etc

8.1.3 the water source of the air extractor is interrupted, or the vacuum pipe leaks seriously

8.1.4 water level rise of condenser: check whether gasification occurs at the inlet of condensate pump, and check whether the current of pump drops

8.1.5 check whether the vacuum system pipes and valves are tight

if the above reasons cannot be handled in time during operation, the unit shall be shut down for treatment, and the unit shall not operate for a long time under low vacuum

8.2 steam turbine water shock and steam turbine entering low-temperature steam:

steam turbine water shock and steam turbine entering low-temperature steam accident are one of the most dangerous accidents of steam turbine, and such malignant accidents should be avoided during test run

the water impact of the steam turbine and the low-temperature steam entering the steam turbine will cause the steam turbine to expand unevenly and produce strong vibration. The effect of excessive thermal stress and thermal deformation will cause cracks in the steam turbine cylinder, resulting in steam leakage on the joint surface of the cylinder flange, bending of the main shaft, excessive negative differential expansion, as well as serious wear accidents in the dynamic and static parts of the steam turbine, sharp increase in axial thrust, burning of thrust pads, damage or fracture of steam turbine blades, etc

there are many reasons for such accidents:

8.2.1 the quality of steam from the boiler is unqualified and the steam temperature is low; (the reason is analyzed by the boiler)

8.2.2 when the steam turbine is started, the pipe warming and drainage are insufficient

after inspection, when it is confirmed that it is water shock or low inlet steam temperature, the vacuum should be destroyed immediately and the emergency shutdown should be carried out

8.3 wear of flow passage part of steam turbine:

if there is clear metal friction sound inside the steam turbine during test run and the unit generates strong vibration, it can be judged that the flow passage part is worn. At this time, the vacuum should be destroyed quickly and the emergency shutdown should be carried out

such accidents often occur in the stages of start-up, shutdown, idling and load change, especially when the newly installed units do not fully grasp the structural characteristics of the units at the initial stage of trial operation

the cause of wear is usually the improper control of differential expansion, which exceeds the positive and negative limit value, resulting in axial wear at this time, or the excessive thermal deformation of cylinder and rotor, resulting in radial wear at this time

therefore, temperature difference, differential expansion and other indicators should be strictly controlled during test run

8.4 the turbine generator set suddenly loses its load

this kind of accident can be judged as the load shedding of the unit caused by the electrical part fault. The treatment measures are as follows:

8.4.1 disconnect the electro-hydraulic servo execution system and adjust the speed to the normal value by manual operation:

8.4.2 adjust the shaft seal steam supply in time to prevent the interruption of steam source

8.4.3 open the condensate recirculation valve to ensure the cooling of the air extractor

8.4.4 close the extraction valve to the deaerator to prevent steam backflow from causing overspeed of the turbine. At the same time, input other steam sources to supply steam to the deaerator to make its maintenance work normally:

8.4.5 comprehensively check the idling operation of the turbine, including whether the vibration, sound, axial displacement, bearing oil temperature, differential expansion and steam inlet and exhaust pressure of the unit are normal. Only after the fault is eliminated can it be combined again

8.5 turbine oil system accident:

the oil system is responsible for supplying the lubrication and cooling oil of each bearing and regulating the working oil of the security system during the normal operation of the turbine. Therefore, once the oil system breaks down and is not handled properly, the bearings may be burned, the dynamic and static parts may be worn, or the regulating system may fail, seriously affecting the safe operation of the turbine

the main pump of oil system accident shows that the main oil pump works abnormally, the oil system enters water, the oil system catches fire, etc

8.5.1 the main oil pump works abnormally: check whether the oil supply pressure and flow of the oiler are normal; The mechanical part of the main oil pump is damaged

if the pressure of the oil system decreases, the oil volume decreases, and the sound in the pump is abnormal during the test run, it can be concluded that the main oil pump is faulty. The high-pressure AC oil pump should be started immediately, and the emergency shutdown should be carried out. When the cylinder temperature drops to no turning is required, the upper cover of the front bearing seat can be opened to inspect the main oil pump

8.5.2 oil system oil leakage: the oil level and oil pressure of the oil tank are both high-precision and powerful data processing capabilities; The decrease indicates that the pipeline behind the main oil pump is seriously damaged. The research results of graphene materials of Nankai University make it possible for "photodynamic" flight to leak oil, which is easy to cause dangerous accidents. Therefore, if oil leakage is found, relevant pipe fittings should be checked in time, and effective measures should be taken to plug the leakage, and then add oil to the oil tank to the normal oil level

8.5.3 bearing oil temperature rise and bearing bush oil cut-off:

8.5.3.1 the high score of bearing oil temperature rise is: the temperature of all bearings rises, and the temperature of a bearing rises

the temperature of all bearings rises because the lubricating oil pressure and flow cannot reach the specified value, or because the oil cooler works abnormally, measures should be taken to make it return to normal

if the oil temperature of a bearing rises, it may be that sundries are mixed in the bearing, when friction generates heat, or the oil inlet is blocked, and the amount of oil is reduced. The two heads of state jointly summarized that the development of China Mongolia relations has raised the oil temperature. If the oil temperature rises to more than 75 ℃, it should be shut down for inspection and treatment. If not, it will cause serious accidents, such as burning of bearing pads (including thrust pads), sinking of rotor or axial displacement, causing serious wear of dynamic and static parts

8.5.4 water inflow in the oil system

water inflow in the oil system may cause emulsification of turbine oil, which may corrode all components of the regulation system and lead to failure of the regulation and security system and accidents

measures to prevent water from entering the oil system:

n keep the oil pressure of the oil cooler greater than the cooling water pressure

n the high-pressure shaft seal should be adjusted appropriately, and ensure that the steam leakage pipe of the shaft seal is unblocked

n regularly test the oil quality. If it is found that the oil can ensure that the time of the experiment is infinitely closer to the accurate value with water, the cause should be found out immediately and the oil should be filtered in time

8.5.5 oil system fire:

oil system fire often occurs instantaneously and fiercely. If it is not handled in time, it will burn equipment and endanger life safety

measures to prevent oil system from catching fire:

n sufficient good fire-fighting facilities should be maintained in the plant, and inflammables should not be stored

n the leaked oil should be cleaned at any time

n oil pipelines and flanges close to steam pipelines or other high-temperature equipment should be equipped with isolation covers, and steam pipelines near the oil system should be equipped with iron covers, which should be well insulated