Common problems in turbine operation and factors causing turbine oil deterioration
2019/12/19??????view:
Performance requirements of turbine oil:
1. Good oxidation stability. In the process of recycling, it is in contact with air and metal for a long time, with a service life of 5-15 years. During long-term operation, there is less sediment and no significant increase in acid value.
2. Good viscosity temperature performance. The viscosity index of oil is high, and the viscosity changes little with the change of temperature.
3. Good demulsibility. The mixing of steam and condensate leads to oil emulsification, and the high anti emulsification performance can separate oil and water as soon as possible.
4. Good anti rust and anti-corrosion performance. Prevent corrosion of equipment caused by water, air and other impurities.
5. Good antifoam.
Common problems in turbine operation:
(1) Abnormal vibration of steam turbine (auxiliary machine)
The abnormal vibration of steam turbine is caused by air flow excitation, rotor thermal deformation, friction vibration and other reasons. If it is caused by air flow excitation, a large number of low-frequency components will appear or the vibration will increase significantly under the influence of operation parameters; the thermal deformation of the rotor is closely related to the rotor temperature and steam parameters, and the thermal deformation of the rotor will cause an increase in the amplitude of one fold frequency, and the unit will have abnormal vibration after the unit is in accordance with the fixed speed in cold state; friction will produce jitter, whirl and other phenomena, making the rotor inside The uneven temperature of the rotor will eventually cause the thermoelastic bending (thermal deformation) of the rotor.
(2) Turbine (auxiliary) oil system failure
The oil system of steam turbine (auxiliary machine) is easy to enter impurities during the installation of steam turbine unit in thermal power plant or the middle journal part, which may lead to the journal scratch. The failure of oil system may also cause the servo valve of intermediate pressure main steam valve of steam turbine unit to be stuck, the servo throttle hole to be blocked and other failures, which will seriously affect the operation of the unit. It is necessary to pay attention to the analysis and elimination of the faults of the oil system of the steam turbine unit, so as to ensure the safe and stable operation of the steam turbine.
(3) Low vacuum of auxiliary condenser of steam turbine
Factors of turbine oil deterioration:
1 chemical composition
There are many factors that lead to the deterioration of oil products in operation, and the internal factors are mainly the chemical composition of oil products. The relative proportion of paraffin, cycloalkane and aromatics in base oil directly affects the physical and chemical properties of oil, such as viscosity index and pour point. The influence of aromatics on the oxidation stability of oil has certain regularity, which is related to the structure and content of aromatics. Generally, we should improve the refining depth of base oil, reduce harmful substances in oil, and add additives to improve the quality of oil. However, if the additives are not selected properly, the compatibility of various additives will affect the oxidation stability of oil products to a certain extent, which will lead to the deterioration of oil performance.
2 oil system structure and design
a. The oil tank is used to store all the oil used in the system, and also plays a role in separating air, water and various impurities in the oil, so the structural design of the oil tank plays a certain role in the deterioration of the oil. If the capacity of oil tank is too small and the number of oil circulation is increased, the residence time of oil in oil tank will be shortened correspondingly, which can not play the role of water precipitation and demulsification of emulsified oil, and accelerate the deterioration of oil.
b. Oil flow rate and oil pressure are related to oil deterioration. The oil in the oil inlet pipe should not only have a certain oil pressure, but also maintain a certain flow rate (about 1.5-2m / s). There is no pressure in the oil return pipe, but a certain flow rate (about 0.5-1.5m / s) should be maintained. If the speed of oil return is too small and the impulse to return to the oil tank is also large, the oil in the oil tank will splash, and it is easy to form foam, resulting in the gas remaining in the oil and accelerating the deterioration of the oil. At the same time, the strong stirring caused by the impulse will make the oil with water emulsion.
3 condition of oil system at startup
Before the new unit is put into operation, welding slag, debris, sand and other sundries often exist in the pipeline of the lubrication system. If they are not completely removed, they will cause trouble after being put into operation. If they are serious, they will cause problems such as bearing wear and governor jamming. These impurities can also affect the physical and chemical properties of the oil, resulting in the deterioration of the oil quality. Therefore, each part of the lubrication system should be cleaned in advance and strengthened to prevent them Protective measures shall be taken to prevent corrosion and pollutants from entering. The internal surface of the lubricating oil system shall be kept clean during on-site storage. When installing components, the opening of the system shall be small to reduce and avoid pollution and keep clean.
4 operating temperature of oil system
One of the important factors that affect the service life of turbine oil is the operating temperature. Especially in the system, when there is too hot spot on the bearing, it will cause oil deterioration. At this time, the oil cooler should be adjusted to control the oil temperature.
5 maintenance of oil system
The quality of oil system maintenance is directly related to the physical and chemical properties of oil products. In particular, the oil system of the unit with steam leakage and water leakage is dirty, and there will be rust, emulsion and sediment in the oil. If the oil cannot be completely cleaned, the performance of the oil will be reduced. Sometimes, due to improper maintenance methods, such as washing powder and other cleaning agents, the oil will be polluted if not cleaned. During maintenance, mechanical methods should be used to remove the sundries as much as possible, and then oil washing and circulating filtration should be used The temperature range is 30-70 ℃. The flushing process shall be sampled for inspection, and the content of impurities in the oil shall meet the specified requirements.
6 pollution
During operation, the pollutants in turbine oil come from two aspects: one is the pollutants outside the system enter through the shaft seal and various pores; the other is the pollutants generated inside, including water, metal wear particles and oil oxidation products, which will reduce the lubrication, anti foam and other properties of turbine oil. Therefore, it is necessary to eliminate the pollution in the operation of turbine oil, otherwise it will not only accelerate the deterioration of oil, but also affect the safe operation of the unit.
7 turbine oil radiated
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