Adjustment method of multistage centrifugal pump
1. Valve throttling
The easiest way to change the flow of the centrifugal pump is to adjust the opening of the pump outlet valve, and the speed of the multi-stage centrifugal pump remains unchanged (generally the rated speed), which essentially changes the position of the pipeline characteristic curve to change the working point of the pump . The intersection of the pump characteristic curve Q-H and the pipeline characteristic curve Q-∑h is the limit operating point of the pump when the valve is fully open. When the small valve is closed, the local resistance of the pipeline increases, and the pump operating point moves to the left, and the corresponding flow decreases. When the valve is fully closed, it is equivalent to infinite resistance and zero flow. At this time, the pipeline characteristic curve coincides with the vertical coordinate. It can be seen that when the flow is controlled by closing the small valve, the water supply capacity of the multi-stage centrifugal pump itself does not change, the head characteristic does not change, and the tube resistance characteristic will change with the change of the valve opening. This method is easy to operate, continuous flow rate, can be adjusted between a certain maximum flow rate and zero, and no additional investment is required, so it is widely used. But throttling adjustment is to consume the excess energy of the centrifugal pump to maintain a certain supply, the efficiency of the centrifugal pump will also decline, which is not economically reasonable.
2. Frequency conversion speed regulation
The deviation of the operating point from the high-efficiency zone is the basic condition for the pump to adjust its speed. When the rotation speed of the multistage centrifugal pump changes, the valve opening remains unchanged (usually the maximum opening), the characteristics of the pipeline system remain unchanged, and the water supply capacity and head characteristics change accordingly. In the case where the required flow rate is less than the rated flow rate, the head of the frequency conversion speed regulation is smaller than the valve throttle, so the water supply power required by the frequency conversion speed regulation is also smaller than the valve throttle. Obviously, compared with valve throttling, the energy-saving effect of frequency conversion speed regulation is very prominent, and the working efficiency of horizontal multistage centrifugal pumps is higher. In addition, the use of frequency conversion speed regulation not only helps to reduce the possibility of cavitation in the centrifugal pump, but also can extend the startup/stop process by presetting the speed-up/speed-down time, so that the dynamic torque is greatly reduced , To a large extent, the extremely damaging water hammer effect is eliminated, and the life of the pump and piping system is greatly extended.
Multi-stage centrifugal pump efficient and energy-saving method
1. When multi-stage pumps are used, multi-stage pumps should be selected according to actual operating parameters. Only when the parameters are not much different can the pump be in a highly efficient and stable operating state. Once in an efficient operating state, energy consumption can be well saved, and the purpose of energy saving is achieved.
2. When choosing multi-stage centrifugal pumps, energy-saving and high-efficiency products using new technologies should be selected.
3. The frequency conversion energy-saving technology is used to provide energy according to the actual working conditions. Generally, the energy is given as much as possible, which also achieves the effect of energy saving.
4. Regular maintenance and maintenance of the pump must use the correct maintenance method, so that the service life of the pump can be greatly improved.
Test and acceptance of multistage centrifugal pump
1. Preparation of the inspection machine before commissioning of the multistage centrifugal pump
1). Check the maintenance records, the quality of the maintenance should meet the requirements of the maintenance regulations, and confirm that the maintenance records are complete and the data is correct.
2). Check the lubrication situation, if it does not meet the requirements, replace or add lubricating oil in time.
3). The cooling water system should be unobstructed.
4). There is no feeling of unevenness and noise in cranking, and the packing gland is not skewed.
5). The hot oil pump must be warmed up before starting, and the preheating temperature increase rate is not higher than 50℃ per hour.
2. multi-stage centrifugal pump load test
Complete the no-load test run, the performance indicators of the multi-stage pump meet the technical requirements, and the load test run can be carried out. The load test run steps are as follows.
1). Turn the car and turn on the cooling water.
2). Irrigation pump.
3). Start the motor. Pay attention to observe the pump outlet pressure, motor current and running conditions.
4). Slowly open the outlet valve of the multistage pump until the normal flow rate.
5). Use the regulating valve or the pump outlet valve to adjust the flow and pressure.
The requirements for load test should be as follows:
(1) The operation is smooth and no noise, and the lubrication and cooling system works normally.
(2) The flow rate and pressure are stable, reaching the nameplate ability or checking ability.
(3) Under the rated head and flow, the motor current does not exceed the rated value.
(4) The temperature of each part is normal.
(5) Bearing vibration amplitude: working speed below 1500r/min, should not be less than 0.09mm; working speed below 3000r/min, should not be less than 0.06mm.
(6) There is no leakage at all joints and auxiliary pipelines.
(7) The shaft seal leakage should not be higher than the following standards. Packing seal: general liquid, 20 drops/min; heavy oil, 10 drops/min. Mechanical seal: general liquid, 10 drops/min; heavy oil, 5 drops/min.
The above are the adjustment methods of multi-stage centrifugal pumps, high-efficiency and energy-saving methods, commissioning and acceptance, ten reasons for excessive power consumption, common repair methods of impellers, fault judgment and elimination, and use process explained by Xianji. Inspection and maintenance. Hope to help everyone! Of course, if you want to extend the life of the multi-stage centrifugal pump, you must regularly clean and maintain it to ensure that the requirements for the cleanliness of the parts are met. During the repair, various different parts have different degrees of cleaning requirements . During assembly, the cleanliness requirements of mating parts are higher than non-mating parts, dynamic mating parts are higher than static mating parts, and precision mating parts are higher than non-precision mating parts. For sprayed, plated, and bonded workpiece surfaces, the cleaning requirements are very high. When cleaning, different cleaning agents and cleaning methods must be adopted according to different requirements to ensure the required cleaning quality. To prevent corrosion of parts, no process is allowed for precision parts
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