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Sewage treatment plant pump equipment selection, installation and operation and maintenance
I. Introduction Qingdao a sewage treatment plant on the first phase of sewage 50,000 t / d, completed in 2002; the second phase of sewage treatment 50,000 t / d, completed in 2008; one or two upgrades completed in the renovation project year 2011. A total of 85 various types of pumps, with a total capacity of 1038kW. Through the pump equipment from the selection, installation, operation and maintenance point of view one by one to explore and analyze for the construction of similar projects and operation and management has a real meaning and help. Second, the selection of pumps In the sewage treatment plant, the pump is mainly used for water upgrade, three-stage treatment to enhance sludge return, the remaining sludge emissions. According to the characteristics of the medium through the use of dedicated sewage pumps, such as submersible sewage pump and sludge screw pump. In the specific selection should follow the following principles: 1) pump should meet the head and flow of technical requirements, the operating point should be within the high-performance area. 2) In the long-term operation of the pump, the device with high average lift over many years has high efficiency and low operation and maintenance cost. 1. Pump steady operation to determine the operating point of the pump installed in a particular pipeline system, the actual working lift and flow not only with the performance of the pump itself, but also with the characteristics of the pipeline. The intersection of the He-Qe curve of the pipeline and the HQ curve of the pump is the operating point of the pump (see Figure 1), that is, the flow Qm and the head Hm corresponding to the m point are the optimal flow and lift of the pump; The intersection of the NPSHa-Q curve with the NPSHr-Q curve of the pump is the critical cavitation point for the delivery system. The pump must operate at less than Qd, otherwise cavitation will occur. Pump characteristic curve obtained by the actual test pump, generally provided by the pump manufacturer. The characteristic curve of the pipeline device should also be actually measured, but it can not be measured before the design. It is often estimated by the empirical formula: H = K + BQ2. Figure 1 pipeline characteristics and pump characteristic curve 2. The selection of flow Q For small changes in flow circumstances, the pump flow directly according to the flow of the selected. For inlet lift pump, the flow has uncertainty and time periodicity, that is, there is a big difference between high and low point. In this case, the highest point flow can not be selected because it will cause most of the operation to deviate from high efficiency zone , Increase operating costs and energy losses. Generally desirable Q = Qmax / 1.2. 3. Head H to determine the flow rate is determined, determine the pump import and export diameter, complete the entire pipeline layout, to determine the head, in the actual choice, the pipeline resistance coefficient is often taken too large, and the other in the choice of pump Model, but also added a head allowance, resulting in the actual operation of the flow is too large, resulting in the following results: 1) Flow increases, the pump shaft power increases, while the motor's efficiency remains unchanged, so the input motor Power is bound to increase. Too much power causes the motor to be overloaded and may cause heat or even burn the motor. 2) If the flow rate exceeds Qd, cavitation will occur and the pump life will be seriously affected. Therefore, the election of the pump lift should not be too conservative, as close as possible to the actual head of the pipeline, in general, can not exceed 1.1 times the actual head of the pipeline. 4. Select the type of pump Select the appropriate pump type from the pump's sample manual, based on the Q and H determinations. It should be noted that the actual choice, in principle, should be chosen to be the closest pump model and device performance curve of the intersection point of the pump model, the best pump operating point in the pump efficiency curve as high as possible. Third, the installation of the pump 1. Installation Preparation According to equipment manufacturers equipment installation plans and design construction drawings, installation instructions, equipment details and other technical information, the development of construction programs, according to the construction program to prepare the necessary tools, appliances and materials; clean installation Site, check the embedded parts size. 2. Basic Preparation and Acceptance The equipment is based on the load bearing and vibration absorbing carrier, whose construction quality directly affects the quality of equipment installation and the normal operation of the pump. The basic acceptance of the pump shall include the pre-compression test; whether the dimensions and geometrical dimensions are the same as those in the drawings; whether the position of the pre-embedded anchor bolt, the elevation and the length of the exposed foundation exceed the required depth; Wait. To repair the basis of the ultra-poor and take other measures to correct. Basis of the line, to determine the installation location: According to the reference axis of the building to determine the vertical and horizontal centerline of the pump set to build the elevation or the preset elevation to determine the equipment installation elevation. Check the relative dimensions of the equipment, the relative positions of the reserved holes, and the relative deviations of the reference axis. Basic surface treatment: the surface treatment equipment to ensure the accuracy of the installation of the pump to clean up debris in the reserved hole and protect the hole. Set the horn or pad: to ensure that each anchor bolt on both sides have a set of reverse tilt horn, horn to ensure the elevation. 3. Pump installation Lifting equipment with the pump base or pump hoisting in place. Pump base should be adjusted to slowly fall anchor bolts until it falls on the pre-placed horn, the bolt after the first twist, remove the spreader. After the pump is in place, first find the pump horizontal position, in accordance with the vertical and horizontal centerline installation to find, and then use the tilting horn to adjust the design elevation and check the level, the import and export flange in the center line of the vertical adjustment it is good. Install the accuracy of the review: The anchor bolts in turn all symmetrical tightening, and then retest all records, such as exceeding the allowable error should be in the study data, loosen the anchor bolts and then adjust all the control data in the anchor bolt fastening state Under full compliance with the standard. Tighten the anchor bolts as required to record the final data. Finally, the tilting horn, base plate welding firm. 4. Motor Installation Lifting the motor and the base plate together with the anchor bolts and dropping them on the tilting horn. The horizontal position and elevation of the motor should be subject to the adjustment of the concentricity of the motor shaft and the pump shaft. Accurately adjust the distance between the two axes within the allowable range. Dial indicator fixed to the motor shaft, tighten the motor anchor bolts, turn the motor, measuring different axis, loosen the anchor bolts, according to the measured data, adjust the height and the horizontal position of the motor by tilting the horn, and then tighten Anchor bolts, and then measure different axis, so repeated until the coaxial control within the allowable range. After the motor is adjusted, symmetrically tighten the anchor bolts, re-check the data is correct, the base plate and the tilting horn welding firm. After the motor running normally, connect the coupling. 5. Grouting unit installation is complete, clean up the installation of oil and debris, filling to the installation elevation. Fourth, the operation of the pump management 1 submersible pump operation and management (1) the optimal operation of the pump group according to changes in water and liquid level, the use of variable frequency speed control technology can achieve pump energy saving, but due to high investment in frequency control, not It is possible to speed up all the pumps. Therefore, pumps with different numbers of pumps, different operating speeds and different flow rates can be operated in parallel to meet the changing conditions. The sewage pumping station adopts 2 sets of 100kW Flygt pumps, one of which adopts frequency conversion technology and one frequency operation; 5 sets of 44kW Flygt pumps, of which one adopts frequency conversion technology and the other 4 operate at the same frequency. In the design of water conditions and to meet the normal flow, generally take a big variable frequency pump, a large frequency pump, 3 small work frequency pump program; or to take a large frequency pump, 4 small working frequency pump, 1 Small inverter pump running mode. The unit has been running for 10 years, has been stable and normal, there is no change because of frequent changes in the amount of water on and off the pump, the energy saving effect is also very significant. (2) the level of the water pump to run at the best operating conditions point in the equipment selection, the characteristic curve of the pump and the intersection of the characteristic curve of the device for the best operating point, but with the pump running time Increase, inevitably accompanied by the reduction of pump efficiency and over-current components wear, which affect the pump characteristic curve of the most serious parameters for the pump impeller wear, impeller wear, the pump is equivalent to the HQ curve down, making the flow and head have The smaller the trend, in order to maintain the original treatment of water, without increasing the number of pumps, you can adjust the pool float, increase the reservoir level, reservoir level increased, the device's He-Qe curve must have a right shift At this point, the head of the intersection of the two curves becomes smaller and the flow remains the same. This ensures that the pump has been running at the best operating conditions, not only to meet the process needs, but also reduce equipment wear and tear, help to extend the economic life of equipment. (3) Submersible pump daily inspection and maintenance personnel should be a listen, two see, three touch, four records. That is to listen to the equipment operating noise is reasonable to see whether the alarm unit leaks and overheating alarm signal, the three touch guide rod vibration is normal, four records of pump operation flow and current. If there is a problem with the above examination, it is necessary to analyze the reason in time and report it. Maintenance personnel regularly check the diving cable elastic condition, whether the wire rope or chain wear, whether fixed, whether there is garbage; regularly check the water pump three-phase resistance is balanced, to the insulation resistance is less than 1M Europe; regular inspection of electrical protection The device is reliable, regularly tighten the terminal. Every six months to check the oil chamber oil, whether there is a leak, and forced to replace; check the impeller wear and tear to determine whether the need to repair and replacement. Perform comprehensive preventive maintenance annually, including: replacing all O-rings; checking bearing wear and adding new grease; checking mechanical seal wear to determine if replacement is required; inspecting the impeller for wear and checking the impeller Pump seal between the sealing ring wear, but it is whether the need to repair and replacement; Check the motor stator insulation, whether the broom damage marks; check the pump at the end of the sand and fouling, check the bottom of the pool grit, Whether the need to stop dredging. 2. Screw pump operation and management Naimo pump (single screw pump) is a positive displacement pump, sludge containing solid particles in the sewage treatment plant, has a wide range of chemical agents. The working principle is: when the screw is working, the liquid is sucked into the sealed cavity formed by the rotor and the stator. Due to the rotation of the rotor, the liquid follows the sealed cavity along the axial direction by the suction side of the pump, and continuous suction And discharge to achieve the liquid transport function. (1) The variable speed operation of screw pump In the sewage plant, the screw pump is generally used with the sludge dewatering machine. Whether conveying the sludge to be treated or flocculant, the flow of the conveying medium is strictly controlled. Screw pump delivery flow and delivery pressure has nothing to do, the delivery pressure is only related with the screw pump series, and flow and speed are strictly proportional relationship. So need to control the delivery flow only by adjusting the motor speed with the inverter or through the belt stepless speed regulation. (2) Operational Protection A temperature sensor is generally installed on the stator to detect the temperature of the stator. In the event of dry running due to lack of medium, the stator and rotor wear will be very large and the temperature will increase with the friction The higher, further increased wear and tear. So now all basic screw pump manufacturers to dry run protection as an essential unit procurement equipment. (3) normal operation of the screw pump process pre-processing unit requirements Screw pump stator is generally rubber material, the rotor is stainless steel, if the transmission medium contains sand, will cause double wear of the stator and rotor, due to the processing technology and materials At present, the quality of the substitutes produced domestically is still relatively low, and the imported spare parts are expensive. In the subsequent sludge treatment units, the overcurrent components of the centrifugal dewatering machine are more sensitive to gravel. Therefore, we should try to reduce the gravel in the transport medium. Screw pump operation Pre-treatment unit aeration grit chamber suction sand pump and sand water separator equipment is used to remove the sand in the sewage, we must ensure its normal operation to reduce the grit in the sludge to extend Screw pump life. Fifth, on-site use of two pump failure analysis and solutions 1. Impeller corrosion and wear As the sewage contains a strong corrosive, return sludge concentration of oxygen is relatively large, increasing the impeller corrosion process. Also, salts dissolved in water have a significant impact on corrosion because they increase the conductivity of water and also increase the galvanic corrosion current. Therefore, the sewage plant's impeller corrosion rate. Municipal sewage also contains more gravel, increased wear on the impeller, the role of the pump at different angles impact impeller surface, the metal first elastic deformation occurs at the impact point, the center of the contact surface by the maximum stress, and then began Into the plastic flow state. With the consumption of gravel kinetic energy, the kinetic energy of gravel gradually transforms into the plastic deformation work of metal, the speed slows down until the gravel stops pressing in and the plastic deformation zone expands further. Thereafter, the elastic deformation of the metal surface will be restored, while the plastic deformation will continue to form impact pits, pits edge extrusion metal deposits. Under the constant impact of gravel, these metal deposits fall off from the metal surface due to new crushing deformation and displacement, and at the same time, the raised deposits are sheared off by the small gravel impact to form a metal grinding , Macroscopically showed scaly pit and short-groove, and honeycomb pitting (see Figure 2). Figure 2 impeller wear photo Corrosion and wear of the impeller, the pump performance curve changes, the pump is operating at abnormal operating conditions, at the same time, due to impeller wear and tear, causing the impeller dynamic imbalance, vibration, likely to cause damage to the machine seal, Bearing damage and other failures, it is necessary to take measures to repair or replace the impeller. The surface of the impeller can be repaired by means of shot peening, carburizing or thermal spraying, etc. The surface repairing with the polymer material also achieves a good effect in actual use (see FIG. 3). It should be noted that the impeller repair needs to be done after the balance test. Figure 3 Bell left satisfied after the nano-polymer material repair of the impeller 2. Dosing liquid pump at the end of the valve is blocked In the upgrading process of the sewage treatment plant, used to enhance the centrifugal pump of ferric chloride solution due to frequent blocking at the end of the valve stuck Pump failure caused by the failure of medicine, because the end of the valve can easily be ferric chloride hardened and stuck stuck and leaking, add water diversion centrifugal pump failure, resulting in centrifugal pump unusable. After analyzing the actual situation in the field, we designed a liquid storage device (see Figure 4), without using another irrigation, the effect is very good in use. How it works: After the pump is started, slowly open the valve on the water, the water level inside the tank drops, and the tank forms a negative pressure. Under atmospheric pressure, the liquid medicine flows into the tank to fill the liquid level along the suction pipe so that the pump can work normally . It should be noted that, after stopping the pump, can not immediately close the outlet valve, to be returned to the tank through the liquid pipe to fill it, and then close the outlet valve, so the next start without irrigation, start the pump and then slowly open the water valve Can be. Figure 4 does not need to pump the liquid storage device VI Conclusion As a sewage plant occupies a large-scale pump equipment management, from the selection, installation and operation and maintenance of each link, to enhance learning, lessons learned, ability The sewage treatment plant equipment good, make good use, so that the effective operation of the normal operation of the sewage plant.