Problems and Countermeasures of the double flow ri

The problems and Countermeasures of the double flow ring seal oil system of the generator (II)

there are two main reasons for the pressure imbalance between the air side seal oil and the hydrogen side seal oil. One is the poor adjustment accuracy of the balance valve of the hydrogen side seal oil system. At present, the required accuracy of the balance valve is 50 mm water column (490pa). During operation, due to the small gap between the balance valve piston and the oil cylinder, a little impurity may increase the movement resistance of the piston, or even block, resulting in the poor adjustment accuracy of the balance valve, which cannot effectively maintain the balance of the sealing oil pressure on the air and hydrogen sides, resulting in hydrogen pollution and increased hydrogen replenishment

the second main reason for the pressure imbalance between the air side seal oil and the hydrogen side seal oil is the measurement error of the air and hydrogen side seal oil pressure. During the operation of the unit, only by maintaining the oil pressure balance between the sealing pad and the rotating shaft can the mutual channeling of the sealing oil on the air and hydrogen sides be reduced. However, due to the structure of the equipment, at present, only the pressure at the oil inlet of the sealing oil on the sealing pad on the air and hydrogen sides can be measured as the regulating signal of the balancing valve, which will inevitably cause measurement errors. The balancing valve cannot effectively maintain the balance of the sealing oil pressure on the air and hydrogen sides, resulting in an increase in the amount of hydrogen replenishment of the generator

2.2 the clearance between the seal pad and the generator rotor increases

the oil flow from the seal pad and the shaft along the axial direction of the shaft to the air side and the hydrogen side is called axial flow. When the seal oil pressure difference between the air side and the hydrogen side remains constant, the exchange volume of the seal oil on the air and hydrogen sides is proportional to the clearance of the seal pad. For 300MW steam turbine, the diameter clearance of sealing pad is 0 Mm, when the seal pad clearance increases from 0.15mm to 0.28mm during operation, the seal oil flow will greatly increase. Due to the inevitable existence between the seal oil on the air side and the hydrogen side, the most easily damaged equipment generally includes the pressure difference. The increase of the seal oil flow will lead to a doubling of the exchange volume of the seal oil on the air side and the hydrogen side, and the air and moisture carried in the seal oil on the air side will enter the seal oil on the hydrogen side through exchange, Then, through the contact between the hydrogen side sealing oil and hydrogen, it enters the hydrogen of the generator to pollute hydrogen and reduce the purity of hydrogen. The increase of sealing oil will cause the static pressure oil return pipeline to be blocked. When the oil level in the oil return chamber (defoaming tank) on the hydrogen side of the generator rises above the lowest position of the journal, it will cause the generator to feed oil

2.3 the generator seal oil temperature is high

the viscosity of the seal oil decreases with the increase of the oil temperature. Within the same flow area, a certain seal oil pressure should be maintained. When the seal oil temperature is high, a large flow of seal oil is required. Similarly, the increase of seal oil temperature will lead to the increase of seal pad clearance, which also requires increasing seal oil flow to maintain a certain seal oil pressure. The generator manufacturer generally stipulates that the normal temperature of the sealing oil at the air and hydrogen sides of the hydrogen cooled generator is between ℃. For the 300MW turbine generator packaged seal oil system, the outlet oil temperature of the oil cooler of the seal oil system at the air and hydrogen sides is controlled by a water return regulating valve, which is generally maintained at about 42 ℃. The viscosity of oil at 42 ℃ is smaller than that at 27 ℃. To maintain a certain sealing oil pressure, a large sealing oil flow is required. Similarly, due to the increase of the seal oil temperature, the inner diameter of the seal Bush will increase. In order to ensure that the hydrogen in the generator does not leak out, it is also necessary to increase the seal oil flow to maintain a certain pressure. Therefore, too high sealing oil temperature will lead to the increase of sealing oil flow. According to the analysis in article 2.2, it will also lead to the decrease of hydrogen purity in the generator or the narrow melting temperature range of generator oil inlet

2.4 the output of the smoke exhaust fan is small

from the sealing oil system of 300MW steam turbine generator, the oil source of the air side sealing oil pump is from the hydrogen oil separator, and the main function of the smoke exhaust wind of the hydrogen oil separator is to extract trace hydrogen from the air side oil, so as to prevent hydrogen from returning to the main oil tank with the lubricating oil. Increase the output of the exhaust fan of the hydrogen oil separator, so that the hydrogen oil separator forms a large negative pressure. The company has developed a "unique and innovative" technical pressure, so that the air in the air side oil is extracted together with hydrogen, which will reduce the air content in the air side sealing oil, According to the analysis in Article 2.1 (the hydrogen pollution of the generator is mainly the air carried by the air side sealing oil, etc. through the fatigue life test machine of elastic elements produced by Shandong Sida high tech, which is mainly used for the fatigue life test of various bellows, fiberglass tubes, elastic elements, etc., the sealing oil is exchanged into the hydrogen side sealing oil, and then the hydrogen is polluted through the exchange of hydrogen side sealing oil and hydrogen), the hydrogen pollution will be reduced