Oil pressure adjusting method for double-flow-ring sealing oil system during impulse running period of steam turbine

Abstract

The invention relates to a method for adjusting oil pressure of a double-flow-ring sealing oil system during impulse rotation of a steam turbine, which can effectively inhibit oil intake of a generator due to parameter change of the sealing oil system in the impulse rotation process, prevent the generator from being damaged and ensure safe and stable operation of a steam turbine generator unit. The state of existing system equipment is adjusted before impulse rotation, and the hydrogen side oil return back pressure of a sealing oil system, the hydrogen side oil pump outlet oil pressure, the pressure difference between the air side sealing oil pressure and the generator hydrogen pressure, the air side and hydrogen side sealing oil pressure difference, the oil pressure of a standby oil source, the air side-to-hydrogen side oil supplementing amount and the floating oil pressure are adjusted to be in proper ranges in advance; before the steam turbine reaches the full rotating speed, the state of the sealing oil system does not need to be adjusted; when the steam turbine reaches the full rotating speed, if the hydrogen side oil return defoaming box gives a high-liquid-level alarm, the hydrogen side oil pressure is increased by slightly closing a hydrogen side oil pump outlet recirculation valve, and the high-liquid-level alarm of the hydrogen side oil return defoaming box is eliminated within a short time. Oil inlet of the generator is effectively inhibited.

Description

Technical Field

[0001] The present invention relates to an oil pressure adjustment method for a double-flow ring sealing oil system during the start-up of a steam turbine, which can effectively suppress oil intrusion into a generator due to changes in sealing oil system parameters during the start-up process, prevent the generator from being damaged, and ensure safe and stable operation of a steam turbine generator set. Background Art

[0002] At present, most hydrogen-cooled generator sets in China use double-flow ring sealing oil system to control the purity of hydrogen in the generator at a high level. For double-flow ring sealing oil system units, during the turbine run-up process, with the rapid change of turbine speed, the dynamic parameters of the sealing oil change greatly, such as oil temperature, oil pressure, hydrogen pressure, etc., and the adjustment of the oil-hydrogen pressure differential regulating valve and the hydrogen-side and air-side pressure differential valve has a certain delay effect, and the sealing oil system is prone to instability, which is manifested as: system oil pressure drops, oil-hydrogen pressure difference drops, hydrogen-side and air-side balance table leans to the air side, hydrogen-side return oil regulator oil level drops, and the amount of oil replenishment increases.

[0003] If the system equipment status is not intervened and adjusted in advance during the flushing process, it is easy to cause a high liquid level alarm in the hydrogen side return oil defoaming box, or even oil in the generator. Therefore, it is necessary to study a complete set of system oil pressure adjustment methods to suppress the occurrence of the above adverse situations. Summary of the invention

[0004] The object of the present invention is to provide a method for adjusting the oil pressure of a double-flow ring sealing oil system during the start-up of a steam turbine, so as to effectively suppress the oil inflow of the generator.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for adjusting the oil pressure of a double-flow ring sealing oil system during a turbine run-up period is disclosed. The method pre-adjusts the hydrogen side return oil back pressure of the sealing oil system, the hydrogen side oil pump outlet oil pressure, the pressure difference between the air side sealing oil pressure and the generator hydrogen pressure, the air side and hydrogen side sealing oil pressure difference, the standby oil source oil pressure, the air side to hydrogen side oil replenishment amount and the floating oil pressure to a suitable range by adjusting the existing system equipment status before the run-up. Before the steam turbine reaches full speed, there is no need to adjust the state of the sealing oil system. When the steam turbine reaches full speed, if a high liquid level alarm occurs in the hydrogen side return oil defoaming box, the hydrogen side oil pressure is increased by slightly closing the hydrogen side oil pump outlet recirculation valve, and the high liquid level alarm of the hydrogen side return oil defoaming box is eliminated in a short time. Subsequently, the oil temperature, oil pressure and hydrogen pressure have been stabilized, and the oil-hydrogen pressure difference regulating valve of the sealing oil and the hydrogen side and air side pressure difference valve have gradually shown their regulating effects. At this time, the hydrogen side oil pump outlet pressure and the oil-hydrogen pressure difference are adjusted back as a whole according to the pressure experience value, so as to avoid repeated high liquid level alarms in the defoaming box and even oil inflow to the generator.

[0007] Parameter adjustment before start-up: Generator hydrogen pressure: The rated pressure of generator hydrogen is 0.48MPa-0.535MPa, and the generator hydrogen pressure is controlled within the range of 0.49MPa-0.495MPa.

[0008] Parameter adjustment before flushing: Hydrogen side oil pump outlet oil pressure: When the oil level of the hydrogen side return oil regulator is not lower than the lower limit and the oil replenishment volume is 8-16L / min, slowly close the hydrogen side oil pump recirculation valve to increase the hydrogen side oil pump outlet oil pressure to 1.35MPa-1.40MPa; the hydrogen side oil pump outlet oil pressure shall not exceed 1.45MPa, and the recirculation valve shall be closed 30° each time before the hydrogen side oil pump outlet pressure is lower than 1.35MPa, and the recirculation valve shall be closed 10° each time after reaching 1.35MPa, and observed for 2 minutes. At the same time, the hydrogen side filter outlet pressure shall be 0.2MPa higher than the air side filter outlet pressure.

[0009] Parameter adjustment before flushing: Oil pressure difference between hydrogen side and air side: maintain the indication close to the upper limit of 5kPa on the hydrogen side to ensure that the oil pressure difference between hydrogen side and air side is not biased towards the air side.

[0010] Parameter adjustment before flushing: Oil-hydrogen pressure difference: The main differential valve can be operated in advance to make the oil-hydrogen pressure difference 0.08MPa-0.095MPa. The initial adjustment range is 90 degrees each time. As the valve is gradually closed, the spring force increases and the adjustment range gradually decreases to 30 degrees each time. Observe for 2 minutes after each adjustment.

[0011] Parameter adjustment before flushing: Oil replenishment flow: Maintain the oil replenishment flow from the air side sealing oil to the hydrogen side sealing oil at 8L / min-16L / min.

[0012] Parameter adjustment before flushing: Backup oil source oil pressure: adjust the backup oil source pipeline pressure reducing valve, the target is 0.95-1.25MPa.

[0013] Parameter adjustment before flushing: Floating oil pressure: gradually close the floating oil pump outlet recirculation valve to make the pump outlet pressure 1.0MPa, which is 1.2-1.5 times the air side filter outlet pressure.

[0014] Flushing process: monitor that the fuel supply pressure on the hydrogen side is always greater than the fuel supply pressure on the air side and the fuel return regulator level on the hydrogen side is not lower than the pump trip value.

[0015] Adjustment after flushing is completed: After stable operation, adjust the hydrogen side oil pump outlet pressure and the oil-hydrogen pressure difference to 0.065MPa-0.07MPa as a whole according to the pressure experience value; according to the recorded number of main differential valve adjustment circles before flushing, adjust the main differential valve to reduce the oil-hydrogen pressure difference. At this time, the hydrogen side oil pump outlet pressure does not change temporarily, and the oil replenishment amount will increase. It is necessary to pay attention to whether the oil replenishment amount exceeds the limit and whether the oil level of the hydrogen side return oil regulator continues to decrease; if the oil replenishment amount exceeds the limit and the oil level of the hydrogen side return oil regulator continues to decrease, slightly open the hydrogen side oil pump recirculation valve to reduce the hydrogen side oil pump outlet pressure. If the high liquid level alarm of the defoaming tank continues to appear, or the main oil tank oil level change alarm signal appears, the frequency of adjusting the main differential valve should be accelerated to reduce the oil-hydrogen pressure difference again and reduce the flow of the hydrogen side sealing oil to the defoaming tank.

[0016] The beneficial effects achieved by the present invention are:

[0017] Save manpower: This oil pressure adjustment method does not require adjustment of the sealing oil system when it becomes unstable during the turbine speed increase process, thus reducing the manpower required for continuous adjustment and monitoring of the sealing oil system during the turbine start-up process;

[0018] Ensure equipment safety: This method can ensure that before the turbine speed reaches full speed, the hydrogen side oil return defoamer box will not have a high liquid level alarm, and the generator will not have the risk of oil ingress, effectively suppressing the erosion of generator components and insulation aging caused by oil ingress. It ensures the safe operation of the generator equipment and avoids the need to re-inspect the generator during overhaul, which delays the construction period;

[0019] No system transformation cost, good economic benefits: This method uses the existing equipment and valves of the sealing oil system to adjust its parameters, does not need to spend money and time to carry out technical transformation of the existing system, and has good economic benefits;

[0020] It has broad promotion value and wide application: At present, large domestic hydrogen-cooled generators basically adopt double-flow ring sealing oil system. This method lists detailed parameter ranges and operating experience for each adjustment of the system, which is easy to refer to for operation in similar power stations and has promotion value;

[0021] Operational safety: This method provides countermeasures for the occurrence of high liquid level in the hydrogen side return oil defoaming box in a few cases after the steam turbine reaches full speed. It can eliminate the high liquid level alarm and suppress the occurrence of oil inflow to the generator in a short time, and the overall operation is controllable and safe. DETAILED DESCRIPTION

[0022] The present invention is described in detail below with reference to specific embodiments.

[0023] By adjusting the status of existing system equipment before the flushing start, parameters such as the hydrogen side return oil back pressure of the sealing oil system (generator hydrogen pressure), the hydrogen side oil pump outlet oil pressure, the pressure difference between the air side sealing oil pressure and the generator hydrogen pressure, the air side and hydrogen side sealing oil pressure difference, the standby oil source oil pressure, the air side to hydrogen side oil replenishment amount and the floating oil pressure are pre-adjusted to the appropriate range.

[0024] Before the steam turbine reaches full speed, there is no need to adjust the state of the sealing oil system, and the hydrogen side return oil defoaming box will not have a high liquid level alarm, to avoid oil intrusion into the generator due to improper adjustment of the system oil pressure when parameters such as the sealing oil system oil temperature and backup oil source are unstable.

[0025] When the steam turbine has reached full speed, if the high liquid level alarm appears in the hydrogen side return oil defoaming box, the hydrogen side oil pressure can be increased by slightly closing the hydrogen side oil pump outlet recirculation valve, which can eliminate the high liquid level alarm of the hydrogen side return oil defoaming box in a relatively short time. The subsequent oil temperature, oil pressure, hydrogen pressure and other parameters have stabilized, and the oil-hydrogen pressure differential regulating valve of the sealing oil and the hydrogen side and air side pressure differential valve have gradually shown their regulating effects. At this time, the hydrogen side oil pump outlet pressure and the oil-hydrogen pressure differential are adjusted as a whole according to the pressure experience value, which can avoid repeated high liquid level alarms in the defoaming box and even oil inflow to the generator.

[0026] This oil pressure adjustment method was designed based on the operation experience of the units since the operation of the Tianwan Phase II project. It is based on the changing trends of parameters such as the hydrogen side return oil back pressure of the generator sealing oil system (generator hydrogen pressure), the hydrogen side oil pump outlet oil pressure, the oil-hydrogen pressure difference, the air side and hydrogen side sealing oil pressure difference, the hydrogen side return oil regulator oil level, the air side to hydrogen side oil replenishment amount and oil temperature during the turbine run-up period. This method can effectively suppress the oil inlet of the generator during the turbine run-up period. It has been well verified in Tianwan Units 3 and 4 and has achieved the expected effect.

[0027] Parameter adjustment before punching:

[0028] 1) Generator hydrogen pressure: The rated hydrogen pressure of the generator is 0.48MPa-0.535MPa. The hydrogen pressure of the generator is controlled within the range of 0.49MPa-0.495MPa to avoid excessive increase in hydrogen pressure and parameter exceeding the limit due to temperature rise during the run-up process;

[0029] 2) Hydrogen side oil pump outlet oil pressure: When the oil level of the hydrogen side return oil regulator is not lower than the lower limit and the oil replenishment volume is 8-16L / min, slowly close the hydrogen side oil pump recirculation valve and try to increase the hydrogen side oil pump outlet oil pressure to 1.35MPa-1.40MPa. The hydrogen side oil pump outlet oil pressure should not exceed 1.45MPa to prevent the safety valve from operating. Before the hydrogen side oil pump outlet pressure is lower than 1.35MPa, close the recirculation valve 30° each time. After reaching 1.35MPa, close the recirculation valve 10° each time and observe for 2 minutes. At the same time, make the hydrogen side filter outlet pressure about 0.2MPa higher than the air side filter outlet pressure;

[0030] 3) On-site balance table (oil pressure difference between hydrogen side and air side): keep the reading biased towards the hydrogen side, preferably close to the upper limit of about 5kPa (normal range 2kPa-5kPa), to ensure that the oil pressure difference between the hydrogen side and the air side is not biased towards the air side, otherwise there is a risk of high liquid level alarm in the defoaming box or even oil intrusion in the generator;

[0031] 4) Oil-hydrogen pressure difference: The main differential valve can be operated in advance to make the oil-hydrogen pressure difference 0.08MPa-0.095MPa, and try to be closer to the upper limit (record the total number of main differential valve operation circles, which can be used as a reference for recovery after flushing). The initial adjustment range is 90 degrees each time. As the valve is gradually closed, the spring force increases, and the adjustment range should be gradually reduced to 30 degrees each time. Observe for 2 minutes after each adjustment;

[0032] 5) Oil replenishment flow: Maintain the oil replenishment flow from the air side sealing oil to the hydrogen side sealing oil at 8L / min-16L / min;

[0033] 6) Backup oil source oil pressure: adjust the backup oil source pipeline pressure reducing valve, the target is about 0.95-1.25MPa;

[0034] 7) Floating oil pressure: gradually close the floating oil pump outlet recirculation valve to make the pump outlet pressure about 1.0MPa, which is about 1.2-1.5 times the air side filter outlet pressure (about 0.89MPa-1.11MPa).

[0035] The upper limit is better.

[0036] Punch process:

[0037] Before the steam turbine reaches full speed, the sealing oil system status does not need to be adjusted, and the hydrogen side return oil defoaming box will not have a high liquid level alarm. It is sufficient to monitor that the hydrogen side oil supply pressure is always greater than the air side (the balance table is biased towards hydrogen) and the hydrogen side return oil regulator liquid level is not lower than the pump trip value.

[0038] Adjustment after the flushing is completed:

[0039] When the turbine has reached full speed, if the high liquid level alarm appears in the hydrogen side return oil defoaming tank, the hydrogen side oil pressure can be increased by slightly closing the hydrogen side oil pump outlet recirculation valve to eliminate the alarm; after the system is running stably, the hydrogen side oil pump outlet pressure and the oil-hydrogen pressure difference are adjusted back to 0.065MPa-0.07MPa according to the pressure experience value. According to the recorded number of main differential valve adjustment circles before the rush, adjust the main differential valve to reduce the oil-hydrogen pressure difference. At this time, the hydrogen side oil pump outlet pressure does not change temporarily, and the oil replenishment amount will increase. It is necessary to pay attention to whether the oil replenishment amount exceeds the limit and whether the oil level of the hydrogen side return oil regulator continues to decrease. If the oil replenishment amount exceeds the limit and the oil level of the hydrogen side return oil regulator continues to decrease, slightly open the hydrogen side oil pump recirculation valve to reduce the hydrogen side oil pump outlet pressure. If the defoaming tank liquid level high alarm continues to appear, or the main oil tank oil level change alarm signal appears, the frequency of adjusting the main differential valve should be accelerated to reduce the oil-hydrogen pressure difference again and reduce the flow of hydrogen side sealing oil to the defoaming tank.

Claims

1. A method for adjusting the oil pressure of a double-flow ring sealing oil system during the start-up of a steam turbine, characterized in that: By adjusting the status of existing system equipment before the flushing start, the hydrogen side return oil back pressure of the sealing oil system, the hydrogen side oil pump outlet oil pressure, the pressure difference between the air side sealing oil pressure and the generator hydrogen pressure, the air side and hydrogen side sealing oil pressure difference, the standby oil source oil pressure, the air side to hydrogen side oil replenishment amount and the floating oil pressure are pre-adjusted to the appropriate range; before the steam turbine reaches full speed, there is no need to adjust the status of the sealing oil system; when the steam turbine has reached full speed, if the hydrogen side return oil defoaming tank has a high liquid level alarm, at this time, the hydrogen side oil pressure is increased by slightly closing the hydrogen side oil pump outlet recirculation valve, and the high liquid level alarm of the hydrogen side return oil defoaming tank is eliminated in a short time; subsequently, the oil temperature, oil pressure and hydrogen pressure have stabilized, and the sealing oil oil-hydrogen pressure difference regulating valve and the hydrogen side and air side pressure difference valve have gradually shown their regulating effects. At this time, the hydrogen side oil pump outlet pressure and the oil-hydrogen pressure difference are adjusted as a whole according to the pressure experience value to avoid repeated high liquid level alarms in the defoaming tank or even oil inflow to the generator.

2. The method for adjusting the oil pressure of the double flow ring seal oil system during the start-up of a steam turbine according to claim 1, characterized in that: Parameter adjustment before start-up: Generator hydrogen pressure: The rated pressure of generator hydrogen is 0.48MPa-0.535MPa, and the generator hydrogen pressure is controlled within the range of 0.49MPa-0.495MPa.

3. The method for adjusting the oil pressure of the double flow ring seal oil system during the start-up of a steam turbine according to claim 1, characterized in that: Parameter adjustment before flushing: Hydrogen side oil pump outlet oil pressure: When the oil level of the hydrogen side return oil regulator is not lower than the lower limit and the oil replenishment volume is 8-16L / min, slowly close the hydrogen side oil pump recirculation valve to increase the hydrogen side oil pump outlet oil pressure to 1.35MPa-1.40MPa; the hydrogen side oil pump outlet oil pressure shall not exceed 1.45MPa, and the recirculation valve shall be closed 30° each time before the hydrogen side oil pump outlet pressure is lower than 1.35MPa, and the recirculation valve shall be closed 10° each time after reaching 1.35MPa, and observed for 2 minutes. At the same time, the hydrogen side filter outlet pressure shall be 0.2MPa higher than the air side filter outlet pressure.

4. The method for adjusting the oil pressure of the double flow ring seal oil system during the start-up of a steam turbine according to claim 1, characterized in that: Parameter adjustment before flushing: Oil pressure difference between hydrogen side and air side: maintain the indication close to the upper limit of 5kPa on the hydrogen side to ensure that the oil pressure difference between hydrogen side and air side is not biased towards the air side.

5. The method for adjusting the oil pressure of the double flow ring seal oil system during the start-up of a steam turbine according to claim 1, characterized in that: Parameter adjustment before flushing: Oil-hydrogen pressure difference: The main differential valve can be operated in advance to make the oil-hydrogen pressure difference 0.08MPa-0.095MPa. The initial adjustment range is 90 degrees each time. As the valve is gradually closed, the spring force increases and the adjustment range gradually decreases to 30 degrees each time. Observe for 2 minutes after each adjustment.

6. The method for adjusting the oil pressure of the double flow ring seal oil system during the start-up of a steam turbine according to claim 1, characterized in that: Parameter adjustment before flushing: Oil replenishment flow: Maintain the oil replenishment flow from the air side sealing oil to the hydrogen side sealing oil at 8L / min-16L / min.

7. The method for adjusting the oil pressure of the double flow ring seal oil system during the start-up of a steam turbine according to claim 1, characterized in that: Parameter adjustment before flushing: Backup oil source oil pressure: adjust the backup oil source pipeline pressure reducing valve, the target is 0.95-1.25MPa.

8. The method for adjusting the oil pressure of the double flow ring seal oil system during the start-up of a steam turbine according to claim 1, characterized in that: Parameter adjustment before flushing: Floating oil pressure: gradually close the floating oil pump outlet recirculation valve to make the pump outlet pressure 1.0MPa, which is 1.2-1.5 times the air side filter outlet pressure.

9. The method for adjusting the oil pressure of a double flow ring seal oil system during the start-up of a steam turbine according to claim 1, characterized in that: Flushing process: monitor that the fuel supply pressure on the hydrogen side is always greater than the fuel supply pressure on the air side and the fuel return regulator level on the hydrogen side is not lower than the pump trip value.

10. The method for adjusting the oil pressure of a double-flow ring seal oil system during the start-up of a steam turbine according to claim 1, characterized in that: Adjustment after flushing is completed: After stable operation, adjust the hydrogen side oil pump outlet pressure and the oil-hydrogen pressure difference to 0.065MPa-0.07MPa as a whole according to the pressure experience value; according to the recorded number of main differential valve adjustment circles before flushing, adjust the main differential valve to reduce the oil-hydrogen pressure difference. At this time, the hydrogen side oil pump outlet pressure does not change temporarily, and the oil replenishment amount will increase. It is necessary to pay attention to whether the oil replenishment amount exceeds the limit and whether the oil level of the hydrogen side return oil regulator continues to decrease; if the oil replenishment amount exceeds the limit and the oil level of the hydrogen side return oil regulator continues to decrease, slightly open the hydrogen side oil pump recirculation valve to reduce the hydrogen side oil pump outlet pressure. If the high liquid level alarm of the defoaming tank continues to appear, or the main oil tank oil level change alarm signal appears, the frequency of adjusting the main differential valve should be accelerated to reduce the oil-hydrogen pressure difference again and reduce the flow of the hydrogen side sealing oil to the defoaming tank.