3, the liquid pump performance test In order to find the cause of the malfunction, the pump was characterized by testing, the use of conventional test methods. Check the relevant meter before the test. Test, the load in each case in Table 1. Through the liquid pump to enhance the pressure after the feed water through the orifice as much as possible to reduce test error. Minimize the use of water, and give the appropriate amendments. On this basis, copy the relevant data. 4, failure analysis test, manual operation spoon tube, the flow does not fluctuate, the current stability, balance pressure is normal, indicating that there is no movement of the pump shaft phenomenon. The motor is working properly and the hydraulic coupling can operate normally at each load point. According to the needs of load regulation, when operating the terminal, the flow has undergone great changes, to control the flow in the required more difficult. Spoon tube stroke changes from 61mm to 71mm, the flow changes from 284t / h to 430t / h. It can be seen from Fig. 1 that the whole speed regulation system has a good linearity but a steeper curve, and the opening degree changes by 1%. The flow rate changes to 11.23t / h and the flow rate of the feed water pump depends on the speed of the feed water pump. The pump shaft is mounted on the turbine of a fluid coupling, and the turbine speed depends on the amount of oil returned to the scoop. If the return stroke unit within the amount of change is too large, will seriously affect the stability of the flow to the pump. To this end, should reduce the rate of change of spoon pipe back to the amount of oil. 4.1 Magnification factor K The maximum travel of the spoon tube is 110mm and the maximum flow rate is 440t / h. According to Table 1, the flow rate changes from 284t / h to 430t / h and the travel distance changes from 61mm to 71mm. K = dg / dμ = αmax / Gmax · dG / dα = (110/440) · [(430-284) / (71-61)] = 3.65 The slope of the curve is 74.7b, which means the curve is steeper Caused by the hydraulic coupling speed instability of the main reasons. To improve the performance of hydraulic coupling adjustment, it is necessary to solve the change of the amount of oil return to the spoon tube, so that the amount of return oil decreases with the same opening degree of change. 4.2 Cam The demolition of the old cam to re-install, put into operation and found that the hydraulic coupling to adjust the performance of the improvement is not obvious. To this end, plus the cam at the same time, change the cam profile, to adapt to the needs of load regulation. That is, under 50% load, the cam profile is steeper. In the region where the load is adjusted constantly, the cam profile is relatively flat and the profile line in the other load regions is also steeper. 4.3 to reduce the rack and gear ratio Hydraulic coupling adjustment, the cam drives the rack up and down movement, the rack and then drive the gear, the gear and then drive the sector gear, causing the spoon tube opening changes, regulating water flow. Spoon tube adjustment is driven by the fan gear rotation, the gear rack and the sector gear coaxial gear. Reduce the rack and gear ratio, that is, increase the gear diameter, extend the length of the rack to ensure that the Spoon open and close strict. Which reduces the gear ratio of the rack and the gear, that is, the cam of the same stroke, the opening of the sector gear becomes smaller, and the return oil regulation of the spoon pipe becomes smaller, thereby reducing the fluctuation of the feed water flow. 5, treatment methods and results According to the above analysis, taken the appropriate measures. First consider increasing the cam, if you increase the cam is invalid, then consider the use of computer regulation and other measures. Increasing the difficulty of the cam is relatively small, easy to implement, and the profile of the cam has been improved. According to the unit load range of normal operation, taking into account the load below 50%, the cam profile steep; at 50% to 100% load, the corresponding profile is relatively flat. At low loads or during startup, the pump can also maintain a high flow rate due to the need to turn on the feed pump recirculation valve. Increase the cam and improve the line after the flow and related parameters in Table 2. Recovery of the original cam spoon tube itself has little effect, spoon tube stroke (60 ~ 70) mm, the slope is still 3.45. According to Table 2, after the improvement of the cam profile, the slope of the whole speed control system (including the hand terminal) is 100/440 · [(416-274) / (71-48)] = 1.4, the inclination is 540, Amplitude decreases, basically meet the needs of load regulation, as shown in Figure 3. Unit through the above transformation after normal operation. 6, the conclusion Hydraulic couplings are generally equipped with a cam, and sometimes in order to prevent the cam jams and cancel the cam, because of regulatory characteristics of the spoon pipe unclear, put into operation before the speed control system has not done static, dynamic flow Characteristic curve test, put into operation after the adjustment performance may be poor, but also may cause fatigue fracture shaft. Once found to pump fluctuations in flow, it is necessary to find out the cause of the malfunction, take appropriate precautionary measures.
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