Abstract: This paper introduces the improvement of economy of DG385-185 type water supply shaft seal system and the improvement of several schemes in Yibin Power Plant, and provides references for the improvement of similar equipment. Key words: Feed water pump; Shaft sealing system; Improvement of 50% capacity water supply system of domestic 200MW unit with two types of shaft seal water system: Shaft seal pump and Shaft seal pump. The main difference between the two is: seal collection backwater different. According to some power plants to improve the situation, the improvement of the system without shaft seal pump shaft seal water back into the front pump inlet, unsealed shaft seal pump, the economy, high safety. A transformation of the implementation of 1.1 The first step to transform the original pressure back to the front pump inlet, stop the shaft seal pump operation, the rest unchanged. The first step to improve the operation: the first run after the renovation found that the distance from the multi-stage water seal on the 1st pump leakage larger end of the pre-pump inlet pressure 0.6MPa near the operation, the return temperature of 70 ℃ And a large number of leakage, rejection of water; 0.7MPa (unit close to full load), the backwater thrown a great amount of water and backwater temperature of 85 ~ 95 ℃. Free end of the front pump inlet pressure 0.7MPa (unit close to full load) running a large number of rejection of water, return water temperature of 70 ℃. 1.2 The second step transformation Based on the previous experience analysis of low pressure side backwater thrown large amount of water, high temperature, the possible reasons for poor multi-stage water seal back to the backwater can not be excreted in time; Too large, and low-pressure water inlet is smaller, resulting in low-pressure leakage, rejection of water, the temperature is too high; low pressure rejection, leakage larger. 1.3 The third step of transformation 1) According to the above two transformation analysis, the reasons for the failure of reconstruction is not in the pipeline itself, and the analysis of the system and equipment before the transformation is not enough to be re-analyzed. Analysis of the helical bushing, which has two: First, near the high-pressure end of the shaft seal before the transformation of water, after the transformation back to the front pump; Second, close to the end of the water before the transformation for the pressure back to water, after the transformation of the shaft seal Water. 2) for re-analysis. Screw bushing near the high-pressure port after the transformation back to the front of the pump: ①conducive to maintaining the screw bushing, screw bushing temperature stability; ② prevent cryogenic condensate into the pump (condensate water pressure in the operation and the front end of the sleeve pressure close to stop When the pressure is higher than the front bushing), to prevent uneven water heating and cooling caused by vibration and increased oxygen content in the feed water; ③ can make the spiral bushing and screw sleeve where the pressure from 1.2MPa reduced to 0.6 ~ 0 .7MPa (front pump inlet pressure). After the transformation of the shaft seal backwater, backwater temperature and pump load has nothing to do with is conducive to sealing. Screw bushing near the low-pressure port after the transformation of the shaft seal water inlet, the hub from the end face of about 60mm. After the transformation of the shaft seal backwater, backwater temperature and pump load. Through the above analysis, the screw bushing near the high-pressure port after the transformation for the pump solution back to the former; spiral bushing near the low-pressure port after the transformation of shaft seal water inlet, the hub from the end face closer, when the need to improve the shaft seal water pressure Inevitably, there will be large water leakage and poor reliability. To this end, the following transformation. ①try to make two close to the screw bushing to increase the throttling length, as long as the shoulder between the two can be sealed into the sealant rope can be. ② As the direction of water changes, the sealed water tank body is modified as follows, and the shaft seal water inlet and outlet pipes are the same as the original inlet and outlet water. 3) after the transformation of the situation. After the above improvements, 1 to 3 pump is operating normally, no water, water leakage; backwater temperature 45 ~ 50 ℃, in any condition are normal, indicating the complete success of the transformation. 2 retrofit postscript Although the transformation of success, but after the transformation due to the direction of water into and out of the original opposite, the pipeline cross, the scene affected the aesthetic, and affect the thermal components overhaul. If the replacement of sealed water tank, the single price of 24,400 yuan, higher cost (two machines need 292800 yuan six pumps). To this end, to further make the following transformation. 1) Free-end sealed water tank body and the transmission side seal water tank exchange, shaft seal out of the water pipe to restore the original installation location. 2) Since the free end of the sealed water tank body and the drive side of the sealed water tank body is different, this will be the free end of the water tank body taper cut off part of the cut-off part welded to the drive side of the sealed water tank cone body, and on the lathe Processing, the two dimensions exactly match. Through the above transformation, with a total investment of not more than 15,000 yuan, No. 21 Unit of Huangpizhuang Power Plant has been completely renovated and has achieved good results. 3 improved economy 3.1 The economy of operation according to the Huangpi Pile Power Plant No. 21 in 1995 actual load hours 5363 calculation, the shaft seal pump motor power is 30kW, the annual energy saving 5363 × 30 = 160890kWh due to Shaft seal pump running time is greater than the pump running time, more than the unit running time, which the value of not less than 180 × l03kWh. At the same time, the high temperature pressurized backwater (60t / h) no longer back into the condenser, and to the front pump inlet can reduce the loss of cold source, improve the thermal efficiency of the unit, its thermal economy can be calculated by the following formula. 1) back to the front pump, the parameters of Pl = 0.6MPa (front pump inlet pressure, the actual 0.6 ~ 0.7MPa); tl = 120 ℃ (Huangpi pile power plant 2l, 22 machine measured average); h1 = 504 kJ / kg. 2) When returning to the condenser, the parameters are P2 = -0.092MPa (actual operating parameters); t1 = 43.287 ℃ (saturated temperature corresponding to P2, actual operating parameters lower than 39 ℃); h2 = 183.28kJ / Kg (actually lower). 3) After the improvement can reduce the cold source loss Q = m × h = 60 × 103 × (504-183.28) / 360O = 5345.3kJ / s annual energy saving: 5363 × l2.5 = 67 × 103kWh thus , Each year can save 247 × 103kWh, 0 per kWh. l8 yuan calculation, can produce 44,486 yuan economic value, and the required about l5m∮32 × 2 stainless steel tube ratio, without six months to recover all the investment. 3.2 Overhaul economy and safety can be maintained after the pressure back to the water pressure and temperature stability, and maintain the same temperature rise with the pump and deaerator, the screw shaft sleeve and shaft in the operation of the minimum thermal deformation, equipment safety Sex improved. At the same time, eliminating the shaft seal pump, you can no longer consume expensive mechanical seals and other spare parts, reducing maintenance. Second, you can also cancel the pressure back to water pressure monitoring system, electrical, thermal control system equipment and power consumption, pump attached valves, to further reduce maintenance costs. 3.3 Feasibility of Operation Due to the abolition of the shaft sealing pump system, it can reduce the operation, reduce the labor intensity and the possible misoperation and malfunction and improve the safety of the unit.
