Causes and Treatment of Deterioration of Phosphate Ester Fire Resistant Hydraulic Oil
October 31, 2022
In order to ensure more efficient and stable operation of steam turbine units in power plants and enhance the stability of operation of high parameter steam turbine units, the traditional mineral oil can be replaced by phosphate ester fire-resistant oil, which can be reasonably applied in the regulating system. Affected by the performance of phosphate fire-resistant oil, its own ignition point is relatively high, basically above 530 ℃. Even if the phosphate fire-resistant oil leaks, it also reduces the risk of fire to a large extent. 1. Hazards of deterioration of phosphate fire-resistant oil 1) An increase in acid value is a hazard. For phosphate fire-resistant oil, the acid value is an important indicator to measure the degree of qualitative change. That is to say, when the acid value of fire-resistant oil increases, more acidic substances will be produced, which will cause serious corrosion problems to turbine components. In addition, when phosphate fire-resistant oil produces deteriorated substances, it will also affect the particle size, resistivity, air release value, foam characteristics and other properties of fire-resistant oil to some extent. 2) Hazards of resistivity reduction. For phosphate fire-resistant oil, resistivity is a very critical electrochemical performance index. If it is lower than 6.0 * 109 Ω· cm, it will lead to electrochemical corrosion of system components. Take the servo valve as an example. It is a precise component. If it runs in the phosphate ester fire-resistant oil with low resistivity, it will be corroded. Once this problem occurs, it will seriously affect the regulating performance of the component. It will not only increase the leakage, but also cause the steam valve of the turbine unit to fluctuate, thus causing the unit load to fluctuate. If the unit load fluctuates significantly, it will even affect the stable operation of the entire power grid system.
2. Main influencing factors of phosphate fire-resistant oil deterioration 1) Moisture impact The hydrolysis of phosphate fire-resistant oil is actually a process of continuous and rapid decomposition of hydrolysates. If hydrolysis occurs, the degradation rate of phosphate fire-resistant oil will be accelerated. For the phenomenon of hydrolysis, it is most likely to occur in acid and alkali salts, becoming the main factor for the increase of acid value, aggravating the corrosion of turbine governing system components, which is not conducive to the safe and stable operation of equipment. 2) Acid value effect In order to ensure the stable operation of the steam turbine unit, the acid value of the phosphate fire-resistant oil is usually controlled at about 0.15mhKOH/g. However, if the acid value of the phosphate ester fire-resistant oil is rising continuously and the phenomenon of more than 0.15mhKOH/g appears, it indicates that the quality of the fire-resistant oil can no longer meet the operation requirements of the steam turbine unit, that is, the phosphate ester fire-resistant oil has deteriorated. When the acid value of the phosphate ester fire-resistant oil rises, the components of the steam turbine unit will be corroded, and a large amount of sludge will eventually form on the surface of the components, affecting the stability of the unit operation. 3) Temperature effect For phosphate ester fire-resistant oil, its most significant feature is that it has a higher ignition point, which can reduce the possibility of fire in the steam turbine unit. At the same time, once a fire occurs in the operation of the power plant, the fire will not extend to the direction of phosphate fire-resistant oil, because an appropriate amount of fire-resistant agent is added in the process of synthesizing phosphate fire-resistant oil.
3. Specific treatment path for deterioration of phosphate fire-resistant oil In order to apply phosphate ester fire-resistant oil reasonably in power plant operation, it is necessary to comprehensively control its deterioration and strengthen supervision. For the specific content of this work, we need to develop a more perfect and scientific management mechanism to optimize the way of oil filtering. Secondly, it is necessary to conduct a comprehensive test on the new phosphate fire-resistant oil to ensure its compliance with relevant regulations. Only in this way can the deterioration of phosphate ester fire-resistant oil be avoided and the steam turbine unit can operate more stably. 1) Remove sundries Generally, after a period of operation, the steam turbine unit of the power plant will produce a certain amount of impurities due to friction and other factors, which will affect the stability of its operation, and will also have a negative impact on the phosphate fire-resistant oil. Specifically, if the steam turbine unit has been operating for about 4 years, it is necessary to conduct a comprehensive calibration and inspection of all components of the fuel oil system to facilitate the removal of impurities. 2) Oil filtering treatment For phosphate fire-resistant oil, optimizing the oil filtering treatment is also the main factor to reduce and avoid deterioration, so as to optimize the overall performance of phosphate fire-resistant oil. The specific methods are as follows: (1) The bypass regeneration device runs together with the group. During the operation of the power plant, the bypass regeneration device is the oil filtering system of the fire-resistant oil system of the steam turbine unit. Most power plants are composed of cellulose filter+diatomite filter. After the oil filtering in this link is completed, it will be filtered by a precision filter. Specifically, diatomite filter can optimize and improve the moisture and acid value of phosphate fire-resistant oil, but its actual use effect does not reach the ideal effect. If the filter element is not replaced in time, the particle size of phosphate fire-resistant oil will exceed the standard. The precision filter and cellulose filter can improve the particle size of phosphate fire-resistant oil [4]. In this way, it can be ensured that the water content, acid value and particle size of phosphate ester fire-resistant oil meet the standard, so as to give full play to its role and value. (2) Irregularly use professional oil filters to optimize the resistivity, acid value, water content, etc. of phosphate ester fire-resistant oil. In specific work, a professional oil filter is used to treat the phosphate fire-resistant oil. After ensuring that the oil meets the standard, stop the oil filtering work. During the operation of the oil filter, it is necessary to conduct regular sampling tests on the resistivity, acid value, moisture, etc. of the sampling port. If the time interval between the two tests is more than 24h, and it is found that the resistivity, acid value, etc. of the phosphate fire-resistant oil have not changed, it means that the oil filter test has failed, and the filter element is replaced for retesting. In this way, the relevant performance of phosphate ester fire-resistant oil can be guaranteed, which meets the requirements of power plant steam turbine operation and reduces the possibility of its deterioration. 3) Oil sample test In order to solve the deterioration problem of phosphate ester fire-resistant oil, the technicians of the power plant should also take samples and test it in time. In fact, sampling is a basic step for testing the quality of phosphate fire-resistant oil, and also a key factor affecting the test results. Therefore, professional staff should be appointed to complete the sampling of phosphate fire-resistant oil. In addition, in order to ensure the accuracy of the test results of water content, acid value and other indicators, the cleanliness of the sampling bottle should also be guaranteed. After the basic work is done, the corresponding test can be carried out. The application of phosphate ester fire-resistant oil in power plants has many advantages, but if it deteriorates, it will also lead to potential safety hazards. In view of such problems, the staff of the power plant need to know the reasons for the deterioration of phosphate ester fire-resistant oil, and formulate targeted solutions, so as to avoid the deterioration of phosphate ester fire-resistant oil, enable them to play their own advantages, and ensure the safe operation of the steam turbine unit.
