First, the pump high lift operation Plain Lake District axial pumping station usually flood, waterlogging case, although some pump stations in the design of some operating conditions under adverse conditions have been checked, but due to water environment changes , The riverbed along the river and the lake are getting silted up year by year. The water level inside and outside the pumping station fluctuate greatly. Especially in the extra-large flood, the water level of the outer river is high, the lift of the pumping station is beyond the scope of its design, Even damaged.
Solve the above problems, according to the actual situation of each pumping station, take measures separately.
1. Adjust blade mounting angle At present, the domestic axial flow pump diameter of 300mm or more, the blade angle can be adjusted. Adjusting the blade mounting angle to a certain extent, expand the scope of the use of the pump, when the pump head lift increases, the blade can be installed to reduce the angle, reduce the amount of water to meet the pump in the case of high-lift normal operation requirements.
At present, there are a large number of medium-sized and small-sized axial-flow pump stations (generally managed by villages and towns) in China with a large number and a wide distribution and a diameter of less than 1m. Due to the weak technical force, it is time-consuming and labor-intensive (half-toned). Therefore, after the pump station has been put into operation, the normal operation range of the pump is rarely checked or adjusted according to the change of operating conditions. As a result, the energy is wasted and the pumping station can not play the normal efficiency. Therefore, it is suggested to strengthen the technical guidance. Especially for those pumping stations which are used improperly and whose lift exceeds the normal range of use, the condition of the pump should be carefully reviewed according to the new operating conditions and corresponding technical measures should be put forward. In accordance with the principle of economical and effective use, generally only when the angle adjustment can not meet the new operating requirements, only consider other technical transformation programs.
2. Change the pump If the blade angle is still not adjusted to meet the long-term high-lift operating requirements, you can consider replacing the pump to a high lift, such as lower than the number of revolutions of the axial pump or guide vane mixed flow pump.
Replacement of the pump is usually a more easy way, but for large and medium-sized pumps, to consider the unit matching and flow path matching and other factors, so a larger project investment, high unit cost of equipment. In addition, due to the high lift of the pump, the possibility of pump cavitation and hydraulic vibration increases at the same flow rate. In particular, the problem of hydraulic matching with the inlet and outlet runners often becomes the main contradiction of changing pumps. Therefore, based on the original pump station hydraulic engineering, the pump replacement method is used to solve the problem of high lift, which is not only expensive but also technically complex. Therefore, it is generally applicable to small and medium-sized axial-flow pump stations. In addition, when changing the pump, it is necessary not only to consider the safe operation of the pump station at the top of the lift, but also to make it possible for the pump station to have a high average efficiency over many years of operation, and to pump stations with a big difference between the maximum lift and the average lift Consider this.
3. Change the impeller to change the impeller and change the pump about the same advantages and disadvantages. However, changing impellers only involves a certain part of the pump, so a great deal of savings can be made in retrofit investment, which is generally applicable to the rehabilitation and technological transformation of large and medium-sized axial-flow pump stations.
To solve the problem of high lift, the existing impeller of the pump must be replaced with an axial impeller with a lower specific speed (increase the lift and reduce the flow rate under the condition of constant power). As the lift of the impeller is increased, the impeller exit speed or momentum moment ring increases, thus requiring the export guide diffuser vortex, spin more powerful. At present, the large-scale vertical axial-flow pump with the impeller diameter of 2.8m and above is fixed in the reinforced concrete of the outlet flow passage, so that it is quite difficult to change the guide vane when changing the impeller. The working principle of the axial flow pump shows that when the lift of the impeller is raised, the absolute flow angle of the inlet flow of the guide vane (the installation angle of the guide vane inlet) α3 decreases, and the curvature θ of the guide vane increases. If the guide vane is not changed, under the same flow rate, the water flow will form a swirl zone on the back of the guide vane inlet, causing the pump efficiency to decrease and outlet pressure pulsation. Therefore, it is better to change the guide vane when changing the modified impeller. It is very difficult to change the guide vanes. It is a good idea to cooperate with the relevant research institutes and make every effort to seek improvement measures under the existing installation conditions. The final reconstruction plan should be determined through the model test.
4. Increase the pump speed by a similar law that increased pump speed, increase pump flow and lift, but the pump shaft power increases, the power need to increase capacity. Pumping station for the ultra-high lift, the key to using this method is the growth rate and variable speed equipment selection. For small irrigation and pumping stations, due to small units, easy to achieve variable speed (such as adjusting the intake of internal combustion engine, changing the pulley diameter, etc.). To the exchange of motor-driven, adjustable synchronous speed (sub-stepless frequency control and stepless frequency control), or adjust the slip (for induction motors, sub-regulation of the stator voltage, change the string around Wire motor rotor circuit additional resistance, etc.) two kinds of adjustment. The former belongs to the energy-saving type, which belongs to energy-saving type. Large and medium-sized farm pump stations, due to the larger unit capacity, speed control equipment more expensive, so use is subject to certain restrictions.
However, in recent years, combined with the pump growth and motor needs of transformation, Wuhan University of Hydraulic and Power Pumps and Pumping Station experts advocate the replacement of the aging motor coil at the same time, to achieve capacity and speed regulation two functions. That is, when aging motor is reformed, the motor power is increased by thinning the thickness of the insulation layer and increasing the cross section of the winding wire under the condition that the structure of the original motor is not changed. Meanwhile, the method of "losing pole" is used to increase the motor speed so as to adapt to high Pumping station needs to run when the head.
Pump new problems arising from the growth rate may be cavitation, unit structural strength, bearing life and the critical speed of the calibration and other issues. Pump growth may also change the inflow channel flow patterns, the pump inlet flow velocity and pressure distribution is uneven, thereby exacerbating the unit vibration. Adopt this kind of transformation scheme, it is suggested to work with the relevant research institutes and manufacturers of pumps and motors, and according to the actual conditions of the pumping station, agree on the concrete reform plan.
Second, the pump super-power operation In the event of a catastrophic flood disaster, in particular, the pump station needs to be as high as possible to increase the pump flow. At this moment, the shaft power of the pump is often greatly exceeded the rated shaft power, resulting in overload of the supporting power machine. Solve the pump super-power problems commonly used methods to reduce the blade mounting angle, lower pump speed, replace the power of larger power machines, motor capacity transformation and so on.
1. Reduce the blade mounting angle When the pump in the high-lift operation, reducing the blade mounting angle can effectively reduce the pump shaft power, to avoid unit overload; the same token, when the pump is running in large flow conditions and the unit overloaded for a long time , The blade angle should also be adjusted down to ensure the safety and normal operation of the unit. The smaller the angle of the blade, the negative impact is reduced pump flow, so it is more suitable for high-lift high-flow conditions not long running time, blade angle full-size large and medium-sized vertical axial flow pump station. Small and medium-sized pump station on the blade halfway, if due to high head, the power of the engine is not enough, in order to save the cost of reform, but also long-term blade mounting angle fixed in a smaller location.
2. Reduce power machine speed usually only applies to small and medium sized units that can be easily changed by gears. For large units, gearboxes are rarely used due to the expensive gearboxes.
3. Replacement of power larger power plant and deceleration similar to the general only applies to small and medium-sized units, for large motor unless it is necessary to increase capacity and update (such as aging and damage serious, repair as new buy), otherwise, should generally do May not be used to avoid unnecessary costs.
4. Motor compatibilization combined with motor aging transformation, the use of new materials and new technology to improve the original motor rated power. To 28CJ56 axial pump supporting 1600kW synchronous motor transformation as an example, if only to replace the aging coil, the motor rated power can be increased to 1800kW, the power increase of 12.5%. Such as the replacement of certain parts of the motor at the same time, such as the transformation of the stator casing and the core, the rotor shaft, yoke, cast steel, iron core, thrust head, mirror plate and guide tile, motor rated power up to 2200kW, The biggest increase was 37.5%. From the practice of motor capacity transformation, the method is successful, so it is one of the most important technical measures to solve the pump overload problem.
5. Other technical measures to solve the problem of short-term pump overload, but also the use of some economical and practical temporary measures, such as pumping station run away from the outer water level of the river during the operation of the pump in the impeller inlet into a small amount of air, etc. .
Third, to increase the flow pump operation Drainage pumping station to consider its own characteristics, try to increase the rush to pump pumping station row to reduce the economic loss of significant significance. On the pump station has been built to increase the flow of measures in addition to increase grab row time, the main is to increase the blade mounting angle and increase the pump speed.
Increase the blade installation angle is within the allowable range of motor power, as much as possible adjust the blade angle, the unit at full capacity operation, so that the pump station in a shorter period of time to rule out more water. However, this mode of operation is often limited by the high water level in the outer reaches of the river, which means that there is a contradiction between high lift and large flow and the unit capacity can not be adapted.
In order to solve the above contradiction and meet the objective needs of safe, normal and efficient operation of pumps in both high and low lift positions, it is worthwhile to study the two-speed motor speed by using the pole-changing pole-changing method combined with the capacity- And promotion of a good way.
Taking the retrofit of a 1600kW synchronous motor matched with a 28CJ56 pump as an example, the rated speed of the motor is 150r / min (40 poles). If the pole-changing pole-changing method is used to increase speed, in order to obtain stable magnetic pull force , Throwing 4 poles evenly around the circumference, that is, the pole speed of the 36 pole after the pole throw becomes 166.7r / min, which is 11.1% higher than that of the former 40 pole. When the pump is running at this speed, it not only allows the pump head to reach 10m, but the flow rate increases a lot more than when the angle is adjusted. When the motor power is increased to 2000kW and the pump operates at 5.6m head, the blade angle can be adjusted to + 8 ° and the single pump flow rate can reach 28.2m3 / s, compared with that before motor capacity increase (blade angle is + 2 ° ), An increase of 6.2m3 / s in flow rate and an increase in efficiency of 1.4% (pump efficiency at + 8 °). In this case, a total of 62 m3 / s of pumping stations with 10 pumps installed will increase the number of pumping stations with 8 ports of 1.6 m.
Increase the speed with the way to increase the pump head and flow, the main problems that may exist is the pump cavitation and impeller inlet flow stability affected. When adopting the scheme, the cavitation condition of the pump should generally be checked according to the condition of the installation. When the cavitation condition of the pump can not meet the requirements after the increase, other measures may be adopted to solve the problem, such as taking measures to improve the inflow of the forehearth State; in the import of impeller front guide wheel and so on.
Fourth, insufficient axial flow pump impeller flooding and improve the import flow impeller due to changes in water environment, the former pool to reduce the water level, or because of the impeller installation is too high, the pump can not work in the lower forewaters, these are the impeller submerged Insufficient problem. In addition, some new problems encountered by pump stations in actual operation have raised extraordinary demands on the flooded impellers. For example, due to the improvement of irrigation and drainage standards, it is required that the pump should be able to operate normally in the lowest possible water level in the forebay (eg, lowering the water level in Neihu, increasing the regulation of water storage and raising the standard of drainage in pumping stations; , Dry-lift irrigation, etc.). On the other hand, axial flow pump due to large flow, the stability of the inlet flow requirements, such as supporting the influent buildings designed poor, or because of changes in external environment and working conditions, will destroy the normal import of impeller Flow conditions, which brings many unsolvable problems to the safety and economic operation of the pump station, such as cavitation, hydraulic vibration and noise, low pump efficiency, and the flow head can not meet the normal requirements specified in the sample.
In order to solve the above problems, in recent years, Wuhan University of Hydraulic and Electric Pumping and Pumping Station Laboratory proposed in the axial flow pump impeller (hereinafter referred to as the main impeller) imported front guide wheel. The front guide wheel is a light-duty, special-structured axial impeller that rotates coaxially with the main impeller to provide energy for its incoming water flow. Due to the lower installation position of the guide wheel (opposite) and the special structure of the guide wheel, the guide wheel itself has strong anti-cavitation characteristics, which can solve the problems of pump cavitation and insufficient impeller flooding to a certain extent. At the same time, as the guide wheel can forcibly improve the inlet flow of the main impeller and adjust the flow velocity and pressure distribution of its cross section, it is expected to eliminate the problems of hydraulic vibration due to the poor flow state and poor performance quality.
The guide wheel can be composed of 3 to 4 helical blades and streamlined wheels. It is connected with the main impeller only by the wheel rim of the two wheels and screwed without damaging the original pump and the unit structure. For large vertical axial flow pump, in order to reduce the guide wheel weight (to improve the unit stress conditions), the guide wheel can be made of light materials, such as aluminum alloy, fiberglass and so on. Theoretical analysis and related experiments show that this method is technically feasible and its effect has been preliminarily verified in a field test of a 28ZLB-70 axial-flow pump station in China. Due to the fact that this method is technically uncomplicated, the cost of reform is low and its implementation is easy, it is especially recommended to further study and try all over.
Fifth, the pump unit vibration and vibration mitigation measures In the floods, due to severe vibration of the pump unit was forced to shut down resulting in "close the door flooded" situation is more common. Some pumping station during abnormal vibration violent vibration of the pump room glass.
According to the different interference force, the vibration of pump unit can be divided into three categories: hydraulic vibration, mechanical vibration and electromagnetic vibration. The vibration in production is inevitable. The vibration of different types of pump units are always generated at the same time. Separately. The direct cause of these vibrations is also different. During the flood, the main source of disturbance to the abnormally severe vibration of the pump unit is the hydraulic imbalance. The reasons should be correctly analyzed according to the actual situation at that time, and the main contradiction should be grasped to take effective measures to reduce vibration.
1. The flood level is extremely high in the river and the pumping station needs to be lifted. The pump works in a saddle-shaped unstable area near the inflection point. The main features of this vibration are instability and periodic repetitions within moments. If the frequency of this cycle and the system's oscillation frequency of the time, it is possible to induce resonance and cause more serious damage, the damping measures are:
(1) clear the local blockage, clear the diversion channel such as water diversion, inflow and outflow, on the one hand, improve the flow regime, on the other hand, reduce the pumping head as much as possible.
(2) For the fully adjustable pump can change the blade angle, reduce or increase the blade angle may make the pump work to avoid the inflection point. Adjust the angle of small leaves can also improve the pump Q ~ H performance curve, reduce the unstable work area.
(3) Use variable speed adjustment method under the possible conditions to change the working point of the pump to stable working area.
(4) small and medium-sized pump can be set bypass or bypass valve, control the pump outlet flow is not less than the unstable working flow.
2. The flood level is extremely high in the outer river, and some are even 2 to 3 meters high. In this case, the pump is started and the air in the water outlet channel is difficult to be discharged and the water holding capacity is also greatly reduced. Repeated compression of the air expansion, causing pressure pulsation, induced vibration of the unit, the crew will not be able to start serious. According to the actual project situation, to divert, improve or increase the outlet of the effluent facilities to improve exhaust speed and ability to seize gas, as far as possible to shorten the start-up process.
3. Front pool water level is too low, changing the water flow pattern, the formation of water entrainment surface vortex and Coanda vortex into the impeller studio after being cut by the blade caused by vibration, the frequency is proportional to the number of blades, and often accompanied Have a lot of noise. Usually diversion, set the partition and other emergency measures to effectively reduce vibration.
4. Fluctuations in the flood outside the river are large, the flow pattern is disorderly, wave pressure waves are reflected into the water runner and lead to unit vibration. Active and effective outlet anti-wave and wave-stabilizing measures should be actively taken.
5 waterlogging water (may diffuse through the trash rack) impulse foreign matter, into the runner and impeller studio, resulting in partial blockage, the formation of asymmetric flow field in the triggering of hydraulic vibrations may also aggravate arcuate gyratory mechanical vibration . Timely discovery of thorough decontamination, you can effectively vibration.
6. Because the working point of the pump is far away from the normal working range, the pump itself has an excessively large required Naphthic residual Δhr, or cavitation occurs due to the deterioration of the influent flow condition, causing the vibration of the pump unit. Cavitation vibration frequency higher, up to tens of thousands of times per second, accompanied by strong noise, the vibration reduction measures are as follows:
(1) The use of variable angle, variable speed or bypass method to adjust the pump conditions, reduce the pump required NPSH Δhr, to avoid cavitation operating conditions.
(2) to take practical measures to diversion, water diversion and other measures to improve the flow pattern.
(3) consider the pump outlet pipe (or flow) in the water into the inlet pipe (or flow), but also set up another pressure pump device, the nozzle with a ring mixer to improve the pump inlet Pressure, to eliminate or reduce cavitation and its vibration, the nozzle can be used for a small nozzle, the pump can consider the use of multiple nozzles. The length of the mixing section, the position of the nozzle and the flow rate injected shall be reasonably determined according to the pilot pressure, the head of the booster, the flow velocity at the nozzle mouth, the main velocity and the number of nozzles.
(4) Replenishment (0.4 ~ 1%) of the gas at the pump inlet (calculated as the volume flow rate) can greatly reduce the cavitation strength of the pump and significantly reduce the erosion, noise and vibration. Specific qi mode and location, should be based on cavitation phenomenon and the relevant engineering experience to determine. 5. If possible, consider the main impeller in the axial flow pump set before the guide wheel, on the one hand can be rectified, on the other hand to provide energy for the import of the main impeller to improve its cavitation performance, eliminate or reduce cavitation vibration.
7. Foreign material entrained in the waterlogging water is clogged and adsorbed on the rotating impeller. In addition to the above-mentioned asymmetric hydraulic vibrations of the flow field, the static and dynamic balance of the rotor will also be destroyed and mechanical unbalance disturbances will cause the mechanical Vibration phenomenon. Stop pumping part of the water after the backwash back to boot, the vibration will be greatly reduced.
8. Under the effect of long-term flooding and waterlogging, if the pump house is unevenly subsided, its inclination may cause asymmetric hydraulic flow in the flow field due to the unevenness of the impeller clearance. Due to the uneven bearing clearance, Dry friction and vibration and other mechanical vibration, and due to uneven air gap generated electromagnetic tension imbalance vibration. The corresponding damping measures are:
(1) Deviation correction of main plant of pump station, see section III of this chapter.
(2) For large vertical axial-flow pump units, the vertical concentricity, horizontalness, rotor verticality, swing, center, and motor of the fixed components of the unit can be re-measured based on the inflow passage within the allowable adjustment range The magnetic field center and bearing clearance, blade clearance and air gap.
9. At present, most pumping station projects have serious aging problems. Under these circumstances, long-term floods may cause unbalanced electromagnetic tension due to faults such as short circuit of rotor windings caused by insulation damage. After confirmation can take the appropriate repair measures.
Sixth, the pump unit was immersed in timely repair After the pump unit is soaked repair is a very urgent and arduous and complex technical work. Should be based on the extent of submergence, immersion time and the status of the unit and other actual conditions, based on a comprehensive inspection, purposeful, targeted and prepared in a timely manner, in addition to the insulation of the motor and other work, the spindle, Bearings and shaft seals and other parts of the repair as a key job.
(A) a comprehensive inspection of plant, unit
1. Check the plant subsidence and compare with the raw data to determine if the unit's level, axis, etc. need to be adjusted.
2. Check the swing, generally only need to use a dial indicator to check the swing connection at the flange, control the original record to determine whether the swing is increasing.
3. Check the lubricating oil and oil level.
4 Check the unit fasteners, check for looseness and corrosion and other phenomena, and make the appropriate treatment.
5. Check spindle connection, seal condition, and shaft corrosion.
6. Check the thrust bearing and the guide bearing the force, clearance and deposit deposit sand and rust and so on.
7. Check the shaft seal packing deposit settling, decay and the degree of reliability of the seal.
8. Check the impeller clearance and air gap, if larger changes should be analyzed and dealt with accordingly. In addition to the hydraulic fully adjustable pump unit, but also the blade angle adjustment agencies should check to check the status of water and seal. Auxiliary system inspection and repair work should also keep up. On the basis of comprehensive inspection work, determine the appropriate repair objects and specific methods. Should be dismantled as little as possible demolition, to avoid blind dismantlement. Follow the first outside the first, after the first, after the first part of the principle of components.
(B) the spindle repair Rust cleaning, measuring the journal at the corrosion and wear, if the wear is small, only the rust grinding process to restore the finish requirements. Grinding grinding wheel should be used at the same time as a saponification liquid coolant and lubricant. Also available emery cloth plus oil grinding, indigenous polishing. If the amount of wear larger, such as the rubber bearing journal, unilateral partial wear value greater than 0.5mm, then the journal for processing, the treatment methods such as spraying, setting and surfacing and so on. Resume dimensions before cutting and grinding.
(C) bearing repair 1. Cleaning (1) wash also known as rough wash, mainly to remove sediment, oil and rust and so on.
(2) fine washing, also known as oil wash, wash the dirt with a cleaning oil wash, clear oil temperature shall not exceed the flash point to prevent burning.
(3) Fine wash also known as net wash, clean the final cleaning of the oil can also be used to blow compressed air and then wash with oil.
2. Bush scraping and grinding the bearing buckle on the mirror plate or journal, repeatedly polish the surface of the bush, and scratch the scraper to highlight highlights, pick flowers and repair scraping into the oil side, chamfer and chamfer, rubber water guide Bearing generally do not need repair scratch.
3. Reinstall the motor in place with the guide bearing on the center of the rotor in place, the thrust bearing to combine the rotor disk level and magnetic field in place. Put in place but also adjust the guide bearing clearance and thrust bearing force.
Conductive rubber bearings in place before the first support surface clean, put stopwatch rubber rope, check the shaft nest with or without debris, wipe the spindle shaft surface, and coated with a layer of castor oil, and then install the bearing, Adjust the gap.
4. Rolling bearing cleaning and installation (1) cleaning and inspection. Before cleaning the bearings in the sediment and dirty oil dredged, and then the bearings on the hot oil to dissolve the residual oil, and then rinse with kerosene, and finally washed with gasoline and dried with a white cloth. After cleaning to check the following items:
a. Bearing rotation is flexible, there is no stuck phenomenon;
b. bearing clearance is appropriate;
c. bearings inside and outside the ring, rolling and other components for bumps, corrosion, burrs and cracks;
d. Measure the roundness and cylindricity of the bearing with an ID micrometer and check that the journal fillet matches the bearing inner race.
(2) installation and adjustment. Rolling bearing installation and bearing structure, size and bearing parts with the nature of the fit. The assembly pressure should be added directly to the ferrule end to be fitted and fitted, and pressure on the roller body is strictly prohibited. The tools and methods used to install the bearings can be determined according to the size of the interference. When the interference is small, the bearing can be gently tapped into the bearing body with a hand hammer. When the interference is large, the bearing should be press-in with a press machine or the heat set method can be used to place the bearing on the oil pan at 80-100 ° C Heating and then install, you can also use the cooling method, but the shaft temperature not lower than -80 ℃.
Rolling bearing clearance is divided into radial clearance and axial clearance of two kinds, the gap used to ensure the normal operation of rolling elements, lubrication and compensation for thermal elongation, which for the bearing performance and service life have a great impact, should be related to Technical documents require inspection and adjustment.
(D) of the shaft seal repair packing box, water seal ring, gland and lining, clear water seal tube replacement filler. The interface is beveled when packing is installed and staggered by 120 ° per turn. Tight packing stuffing should be appropriate, the general control of pressure seal water leakage from the filler 30 to 60 drops / minute is appropriate.
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