Analysis and treatment of main problems of the hot

Analysis and treatment of main problems of steam turbine

Sichuan Huadian Yibin power plant 1 × The steam turbine of 100 MW Circulating Fluidized Bed project adopts n100-8.83/535 high-temperature and high-pressure, double cylinder, double exhaust, impulse and condensing steam turbine manufactured by Beijing turbine motor Co., Ltd. QFS covestro hopes to break the traditional chemical industry that only paid attention to industrial production in the past through this "point to surface" way Do not care about the inherent situation of the market and customer requirements - 100-2 double water internal cooling generator and dg410/98 circulating fluidized bed boiler manufactured by Dongfang Boiler Works. The unit is jointly controlled by max1000dna DCS distributed control system and Xinhua DEH electro-hydraulic regulation control system. The project is designed by Sichuan Electric Power Design Consulting Co., Ltd., installed by Sichuan Electric Power Construction No. 2 and No. 3 company, and commissioned by Sichuan electric power adjustment and testing institute

treatment and suggestions of main problems in the process of integrated startup and commissioning of 1 unit

the unit was first started at 22:33 on December 21, 2003 to the ninth start at 17:42 on January 10, 2004, and completed 72 hour trial operation and handover for production. During this period, problems such as shaft seal steam source, low safety oil pressure, poor drainage of low-pressure heater and so on were encountered

1.1 unit shaft seal steam source problem

the Design Institute of unit steam seal steam source only designs to supply steam from the steam balance header, which makes it possible to provide shaft seal steam supply only when the deaerator is pressurized first during cold start-up. Because the deaerator takes a long time to pressurize and requires a large number of heating steam sources, the cold start-up time of the unit is prolonged and the thermal economy is very poor. At 22:33 on December 21, 2003, when the unit was first started, the steam turbine was shut down because the deaerator could not provide sufficient shaft seal steam supply. At the suggestion of the commissioning personnel, a pipeline from the auxiliary steam header to the steam seal steam supply is installed. The installation and transformation cost is very low, but the reliability and safety of the shaft seal steam supply of the unit are greatly improved, and the start-up time of the unit is shortened, which is conducive to the rapid and safe start-up of the unit

1.2 water injection problem of high-pressure heater

due to design reasons, the high-pressure heater integrated valve is not installed with water injection pipeline and valve, the high-pressure heater system cannot inject water, and the high-pressure heater integrated valve cannot be put into operation. After installing water injection pipeline and water injection valve, During water injection, it was found that when the feed water pressure reached 8.0 and the injection pressure achieved low porosity and good bonding between the insert and the overmolded polymer MPa, the high-pressure heater combined valve still could not jack up normally. After disassembling the combined valve, it was found that the piston through-flow hole was 2 too small, and such a small through-flow led to the backlog of long water that could not be completely discharged. After expanding the through-flow hole on the piston of the combined valve to 3.5 and reducing the control water long flow orifice from 3 to 1, the combined valve of the high-pressure heater can be jacked up normally at 4.0 ~ 5.0 MPa, which solves this problem

1.3 drainage of shaft seal pipeline

the pipeline from live steam to the primary steam leakage chamber of the front steam seal is very long, and the height drop is large, but there is no drainage in the design, which will lead to pipeline vibration and steam with water when passing steam. According to the suggestions of the commissioning personnel, this pipeline is installed to solve this problem

1.4 condensate with the rapid development of the automotive industry, especially new energy vehicles, the condensate and demineralized water are interconnected

the make-up water of the cold water tank in the unit and the make-up water of the vacuum pump steam water separator are from the condensate and demineralized water, which are separated from each other through valves. Due to the unreasonable design, the condensate cannot be isolated when making up water with demineralized water, because the high pressure of the condensate will cause the condensate to cascade into the demineralized water pipeline, When the quality of condensate water is unqualified, it will affect the quality of demineralized water and cause harm to the whole unit. This problem is solved after modifying the pipeline

1.5 wrong installation of oil ejector

when starting the high-pressure oil pump for the first time, it was found that the inlet pressure of the main oil pump reached 0.5MPa, which was obviously abnormal. After checking the oil ejector, it was found that the oil ejectors 1 and 2 were installed reversely, which was inconsistent with the installation drawing. After reinstallation, the inlet pressure of the main oil pump returned to normal

1.6 the safety oil pressure of the steam turbine is low

the safety oil pressure is found to be low during the trip of the steam turbine, which is only about 1.5MPa, resulting in the failure to trip normally. It is suspected that the two 6 orifices on the start valve are too small, resulting in the failure to establish the safety oil pressure normally. After expanding one of the orifices to 7, the safety oil pressure increases to 2.0MPa, and the unit can trip normally and return to normal

1.7 generator water cut-off protection

because the internal cooling water flowmeter supporting Beizhong cannot be used as the water cut-off protection switch, only the internal cooling water pressure is used as the generator water cut-off protection signal during the whole trial operation. Since the generator water cut-off protection is an important protection device of the unit, and there is great potential harm in the operation of the unit without a flow switch, it is recommended to purchase a reliable internal cooling water flow switch as soon as possible to ensure the long-term safe operation of the unit

1.81, No.2 emergency governor

after the first startup and load of the unit, the mechanical overspeed test of the unit was carried out. No.1 flying hammer could act, but the throttle cover of No.1 wrong throttle was found to have broken and fallen off during the third overspeed test. After replacement, No.1 flying hammer could be in a warning state and hit out normally, while No.2 flying hammer did not act after more than ten tests. Disassemble and inspect No.2 wrong throttle. The following problems were found:

1) the clearance between No. 2 flyweight slide valve and seat sleeve reached 180 μ m. Much higher than the normal 100 μ m. The reset oil hole is 3 mm. After calculation, its flow area is much smaller than the discharge area between the slide valve and the seat sleeve, resulting in the safety oil pressure can not be completely discharged after the unit is tripped, the unit cannot be tripped, and the parts are rough

2) after hanging the brake, the reset oil pressure is still about 0.08 MPa and cannot reach zero

3) the flying ring spring has been deformed and softened after several assemblies, so that the flying ring cannot be in place correctly when hanging the brake, or the brake falls due to insufficient tension after it is in place

to sum up, No. 2 emergency governor has serious quality problems and should be replaced as a whole. However, in view of the urgent time of test run, a temporary measure of installing an oil drain valve on the reset oil pipe was taken, but the flying ring could not be in place correctly when hanging the brake, which often caused the turbine to trip. Finally, change the throttle cover of the wrong throttle of No. 2 emergency governor to No. 1. The test run of the unit was completed under the condition of a mechanical flying hammer

because mechanical overspeed is an important protection of steam turbine, it is directly related to the safe operation of the unit. It is suggested that the qualified No. 2 emergency governor should be assembled as soon as possible and the overspeed test should be carried out, and the original temporary measures should be canceled and restored to the original state to ensure the safe operation of the unit

1.9 extraction check valve water control solenoid valve