1. Main construction technology in the construction of municipal drainage pumping station
1. 1 construction joint treatment
When cast-in-situ concrete is used in the enclosure structure of pumping station project, continuous casting is generally used in the vertical parts such as pool wall and partition wall to avoid construction joints. The time interval between two construction layers shall not exceed the initial setting time. Correctly mastering the secondary vibrating technology can not only improve the bonding degree of construction joints, but also improve the compactness of concrete. That is, the concrete poured first is vibrated again before and after the final set (usually 2-4 hours), and then the concrete is poured again. If construction joints must be left, they should be left in the parts of the structure where the shear force is small and convenient for construction. Generally, horizontal construction joints can be made by the following methods: (1) In order to combine new and old concrete firmly, the contact surface should be cleaned and chiseled, and a layer of cement mortar with the same proportion as the mortar in concrete should be laid on the surface of old concrete, and its thickness should be less than 2 cm. Then, concrete can be poured before the mortar sets. (2) For projects with high water pressure or high waterproof requirements, the treatment of construction joints also needs to consider embedding water stops and tamping them carefully.
1.2 waterproof requirements of concrete
In the design and construction, the self-waterproofing of the structure is emphasized, and the requirements of impermeability grade are defined. The key to self-waterproofing of concrete structure is to ensure the compactness of concrete and control the concrete from cracking. Paper reference network. We can start from the following aspects. (1) water-cement ratio: under the premise of not affecting concrete mixing and tamping and avoiding honeycomb pits, reduce the water-cement ratio as much as possible. (2) Mix proportion: Pay attention to improving the particle size of aggregate, and use platform cement and sand. (3) Construction conditions Pay strict attention to the concrete mixing, transportation, pouring and tamping, and take effective maintenance measures. (4) Admixtures: Admixtures (compaction agent, waterproofing agent, water reducing agent and air entraining agent) are properly mixed into ordinary concrete mixture. Waterproof concrete with good impermeability can be prepared by plugging capillary channels in concrete with 3% densifier and forming tiny closed pores with air entraining agent. Generally speaking, the maximum water-cement ratio of cement concrete should be controlled below 0.6. When the cement grade is greater than 425 and mixed with fine active powder, the cement dosage should not be less than 280kg, and the selected cement is pozzolan or ordinary portland cement. The maximum particle size of stone should not be greater than 40mm, and medium-coarse sand should be used for sand. In addition, spraying protective layer on the surface of concrete structure can also improve the waterproof performance of cement structure.
1.3 Waterproofing at wall-penetrating pipeline
There are many kinds of through-wall pipes in pumping station engineering, which are the weak parts of waterproof. Common waterproof methods for through-wall pipelines should be carefully treated as follows: (1) Wrap a circle of water-stop rubber in the middle of the through-wall pipeline, and embed two-component polysulfide rubber in the root of the pipeline. Paper reference network. (2) Spray polyurethane (PU) foaming filler in the gap between the wall-penetrating pipe and the wall. The foaming filler is liquid before use, and it foams after being sprayed into the gap, and its expansion reaches 45 times. Practice has proved that this method has good waterproof effect and simple operation.
1.4 deformation joint setting
In order to avoid cracks in concrete structures, deformation joints should be set for larger pool structures, which should meet the requirements of sealing, waterproofing, deformation adaptation and convenient construction. Common ones are caulking type, sticking type (sticking rubber sheet), embedded rubber water stop and attached rubber water stop. But these kinds of deformation joints are not ideal, because improper handling of deformation joints will lead to a large number of water leakage in the pool. Three types of deformation joints, namely caulking, caulking and pasting, can be combined to form multiple lines of defense and improve waterproof reliability.
2. Problems and solutions in the operation of municipal drainage pumping station equipment
2. 1 pump
The water pump is the core of the pumping station, and the lifting and discharge of rain (sewage) water is realized by the water pump. In multi-pump pumping stations, the current of the side pump is higher than that of the middle pump, some pumping stations have a current higher than 20%, and some pumping stations need to start the side pump first, otherwise the side pump will not start, indicating that the water diffusion flow pattern in the pumping station is not good, and the water distribution is uneven and unstable. Some pump houses are equipped with multiple pumps, but the water outlet tank uses lateral water outlet, which has large water outlet resistance and running current, and even the side pump far away from the water outlet frequently trips. It shows that the layout of the outlet pipe of the pumping station is unreasonable and the head loss is too large, which seriously affects the operation of the pump. Main faults in water pump operation. (1) sundry jam. During the operation of the water pump, the pump blades are easily caught by debris or damaged by hard objects such as wood blocks and steel bars due to garbage and debris in the water inlet pipeline. In operation, it is often found that the pump suddenly trips, the current is too large, the motor is stuck, the vibration is too large, and there is abnormal noise. After lifting the pump, it is found that there are a lot of sundries in the pump impeller, or it is stuck by wood blocks or steel bars. After cleaning the impurities in the water inlet pipe and water inlet tank, the frequent blockage of the water pump is basically eliminated. (2) The water pump cable is worn. Pumps used in sewage pumping stations and large rainwater pumping stations are mostly submersible sewage pumps and submersible axial-flow pumps. Most of the cables of submersible pump are in water. If it is not fixed properly, the cable will shake with the operation of the water pump, and the cable will wear after a long time, causing the water pump to enter the water or the cable to trip due to short circuit. In the process of operation, often due to negligence or lack of experience, problems were not found in time, leading to such failures of pumps. Therefore, in the operation of the pump, it is necessary to regularly check the fixing of the pump cable to prevent the cable from being worn and affecting the safe operation of the pump. (3) cavitation. During the regular maintenance of water pumps, it is found that some pump blades are seriously cavitation, almost all vertical axial flow pumps will have cavitation, and some blades are damaged to 1/3- 1/2. After the blades are worn, the flow rate of the pump will be reduced and the vibration will be intensified, which will seriously affect the normal operation of the pump. After the pump cavitation occurs, the design department should be consulted to review the operating conditions of the pump to check whether the operating conditions and cavitation allowance of the pump meet the requirements.
2.2 Clean the machine
The main function of the cleaner is to intercept a large number of solid sundries in rain (sewage) water and prevent sundries from entering the pump and blocking the pump. Judging from the effect of cleaning machines, some well-known brands of cleaning machines run stably with low failure rate, but their prices are higher. Domestic cleaning machines are cheap, but the failure rate is relatively high. In the process of operation, it is often blocked by wood blocks or fiber fragments. If the protection can't play its role in time at this time, it will often damage the cleaning machine. Such as rake tooth deformation, grating deformation, frame displacement, etc. Therefore, sensitive, reliable and complete protection plays an important role in ensuring the normal operation of the cleaning machine. Because there are many sundries in the water, the rake teeth are very easy to get stuck in the rotary washer, especially when there are many sundries. Therefore, only by increasing the frequency of fishing and observing frequently can we reduce the number of jams. Paper reference network.
2.3 categories of electrical equipment
There are more and more power transformation and distribution equipment in pumping stations, and the trend is increasing year by year, and the safety level exceeds the standard. At present, the power transformation and distribution equipment used is not updated quickly, and some water pump starting cabinets are started by one-to-one autotransformer decompression. In operation, electrical equipment failures will be encountered more or less: (1) electrical connectors are overheated. After running for a period of time, the electrical connector will be corroded to varying degrees, which will make the contact surface smaller and the water pump will generate local heat when running. If it is not found in time, it will burn out equipment or lines. Therefore, in the process of equipment operation, we should check the contact and tightness of each electrical connector, and form the habit of regular inspection. (2) The protection setting value is unreasonable. After the equipment runs for a long time, the current and voltage will fluctuate in different degrees after aging. Many electrical protection devices, such as thermal relays and short-circuit protectors, have protection settings for the corresponding protected equipment. When the current of electrical equipment fluctuates due to aging, the protection will be too sensitive and the equipment will trip frequently, but it is found that the equipment is normal after inspection. When the set value increases, it will cause equipment failure and the power protection equipment cannot be cut off in time. Therefore, the running state of the equipment should be carefully checked during the operation to ensure the safe and reliable operation of the equipment.
3. Concluding remarks
In the construction and operation of municipal drainage pumping stations, many unexpected problems are often encountered, which may be far more than the above points. The key is to see whether our engineers and technicians can accumulate experience, prevent the failure from happening again as much as possible, and take effective measures to solve it quickly after the failure, so as to ensure the normal operation of the drainage pumping station and maximize the benefits.
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