When it comes to sewage treatment plants and sedimentation tanks, the scraper is definitely an 'unknown hero'. It runs around the pool all day, scraping the settled sludge to the designated location to ensure smooth water purification. Many people may not be familiar with it, but in fact, it plays a crucial role in fields such as environmental protection, municipal governance, and industry. Today, let's talk in plain language about the classification, working principle, precautions to be taken during operation, and where it is used.
1、 What are the common types of mud scraper machines?
There are many types of mud scrapers, and different tanks and sludge properties require different mud scrapers. We can classify them by structure and working mode, and the common ones are mainly as follows:
Central transmission scraper
This mud scraper, as its name suggests, is powered by the center of the pool. It is usually used in circular sedimentation tanks with a diameter ranging from 6 meters to 50 meters. There is a pillar in the center, and the motor and reduction device are both located on the top of the pillar, which drives the scraper arm below to rotate through the transmission shaft. The scraper arm is equipped with a scraper, like a compass drawing a circle, slowly rotating along the bottom of the pool, scraping the sludge into the mud hopper in the center of the pool, and finally discharging the sludge through the sludge discharge pipe. Its advantages are simple structure and small footprint, suitable for small and medium-sized circular sedimentation tanks. However, if the tank is too large and the scraping arm is too long and easy to shake, other types need to be considered.
Surrounding transmission scraper
The peripheral transmission scraper is mainly used in large circular sedimentation tanks, with a diameter of over 20 meters or even hundreds of meters. Its power unit is not located in the center, but on the walkway at the edge of the pool, with two or more walking wheels that move along the track at the edge of the pool wall, driving the scraper frame below to rotate. The mud scraper is a truss structure that is relatively sturdy and can cover the entire bottom of the pool. In addition to scraping mud, some peripheral transmission scraping machines also come with suction pipes, which scrape mud while sucking it into the central mud hopper. This type of mud scraper has a more uniform force distribution and is suitable for large pools. The scraping effect is stable, but the equipment is relatively large and installation and maintenance are slightly more complicated.
Bridge scraper
The bridge type mud scraper is used in rectangular sedimentation tanks, like a bridge spanning over the tank, with both ends mounted on the walkways of the tank wall. Its scraper is located at the bottom of the pool and is driven by a motor to move back and forth along the length of the pool using a chain or wire rope. When moving forward, the scraper sticks to the bottom of the pool to scrape the mud, pushing the sludge to the mud hopper at the end of the pool; When retreating, the scraper will lift and not come into contact with the sludge. Some bridge scraper machines are also equipped with a skimming device to scrape the floating slag on the water surface into the slag tank. This scraper is suitable for rectangular horizontal sedimentation tanks, with simple operation and high scraper efficiency.
Gantry scraper
The gantry scraper and bridge scraper are similar in that they also work in rectangular tanks, but their operation is more flexible. Its main body is a gantry car that can move on the track above the pool, and the mud scraping device can move up and down, as well as left and right. When scraping mud, the gantry crane moves to the designated area, lowers the mud scraper, and then scrapes the mud along the length of the pool. After scraping one section, it moves to the next section, just like a robotic vacuum cleaner cleaning a room. It is suitable for situations where the pool is relatively wide and the sludge distribution is uneven, such as sedimentation tanks in industrial wastewater treatment, but the equipment cost is relatively high.
2、 The working principle of a mud scraper is actually very simple
Regardless of the type of scraper, the core principle is similar: the scraper is driven by a mechanical device to move, collect the settled sludge at the bottom of the tank to a designated location, and then discharge it outside the tank. At the same time, the clear water and sludge are separated, and the clear water flows away from the outlet tank at the top of the tank.
Specifically, after entering the sedimentation tank, the flow rate of sewage slows down, and suspended solids in the water slowly settle to the bottom of the tank under the action of gravity, forming sludge. The scraper of the mud scraper contacts the bottom of the pool, and with the movement of the mechanical transmission device, the scraper pushes the dispersed sludge towards the collection area of the pool (such as the central mud hopper and the end mud hopper). The sludge in the collection area accumulates more and more, and is discharged from the discharge pipe to the sludge treatment system through its own gravity or pump pressure. During this process, the speed of the scraper should not be too fast, otherwise it will stir up the settled sludge and affect the quality of the effluent water; The speed should not be too slow, otherwise the sludge will accumulate too thick at the bottom of the tank and cannot be scraped. So each scraper has a suitable operating speed, usually a few revolutions per minute or a few meters per hour, adjusted according to the nature of the sludge.
3、 Pay attention to these things when the mud scraper is running
Although the mud scraper looks sturdy, if not careful during operation, it is easy to malfunction, affect the treatment effect, and even damage the equipment. These points need to be remembered:
Pre startup inspection is essential
Be sure to check carefully before starting up. First, check if there are any debris in the pool, such as stones, plastic bottles, ropes, etc. These things can get stuck on the scraper or damage the equipment, especially for newly built pools where construction waste must be cleaned up. Then check whether the connecting bolts of each part are loose, whether the scraper is deformed or worn, and whether there are signs of breakage in the chain and steel wire rope. Let's take a look at the lubrication situation again, whether the lubricating oil in the motor, bearings, and gearbox is sufficient, whether the oil quality is good, and if not, add or replace it in a timely manner. Finally, try the motor and transmission device, run them without load, listen for any abnormal noise, and check if the rotation direction is correct. If there are no problems, then start the machine officially.
Pay close attention to parameters during operation
When the mud scraper is running, it cannot be ignored and must be observed at all times. Pay attention to the temperature of the motor. During normal operation, the temperature of the motor casing generally does not exceed 60 ℃. If it is hot, it may be due to overload or motor problems, and the machine should be stopped for inspection. Listen to the sound of the device running. Under normal circumstances, it should be a smooth and low noise. If there is a "creaking" friction sound or a "clicking" impact sound, it may be due to the scraper hitting a hard object, or the bearings or gears malfunctioning. Stop the machine in time for troubleshooting. It also depends on the scraping effect, whether the sludge at the bottom of the pool is scraped clean, whether the sludge discharge pipe is blocked, and whether there is a large amount of sludge surging on the water surface. If the effluent becomes turbid, it may be due to the scraping speed being too fast or the scraper not being adjusted properly.
Regular maintenance and upkeep extend lifespan
Mud scraper is a mechanical equipment, and regular maintenance is very important. After each day's operation, clean the debris on the scraper, wipe off the sludge and water on the equipment, keep it dry, and prevent rusting. Check the transmission components such as chains and gears once a week, and add lubricating oil to make the rotation smoother. Check the wear of the scraper every month. If the scraper is worn too much and the gap between it and the bottom of the pool becomes larger, the scraping effect will decrease. It needs to be adjusted or replaced in a timely manner. Conduct a comprehensive inspection of the motor and gearbox every quarter to check for loose wiring, good sealing, and oil leakage, ensuring that the equipment is in good operating condition.
Timely handling of special circumstances
During operation, it is inevitable to encounter special situations, such as sudden power outages. The power switch should be turned off first, and after the power is restored, the equipment should be checked for any abnormalities before restarting. If too much sludge is found and the scraper is stuck and cannot be forcefully opened, it is necessary to manually clean a portion of the sludge in the pool first, or reduce the scraping speed, eliminate the fault, and then operate. When it rains or there is a significant change in the quality of the incoming water, the amount of sludge may suddenly increase. It is necessary to adjust the discharge frequency in a timely manner to prevent sludge from accumulating too thick at the bottom of the tank.
4、 The application scenarios of mud scraper are very wide
Scraper is a key equipment for sewage treatment and water quality purification. As long as there is a sedimentation tank that needs to treat sludge, it can be used almost everywhere. It is mainly used in these fields:
Municipal sewage treatment plant
The municipal sewage treatment plant is the "main battlefield" of the scraper. Whether it is a primary sedimentation tank or a secondary sedimentation tank, it cannot do without a mud scraper. The sludge in the primary sedimentation tank is mainly suspended solids in the sewage, which are relatively coarse; The activated sludge in the secondary sedimentation tank is relatively delicate. Different sedimentation tanks will use suitable scraper machines, such as bridge or center driven scraper machines for primary sedimentation tanks, and peripheral or gantry driven scraper machines for secondary sedimentation tanks, to ensure timely discharge of sludge and stable operation of sewage treatment plants.
Industrial wastewater treatment
There are many types of industrial wastewater, and the properties of sludge are also complex. Some sludge contains oil, some contain heavy metals, and some are relatively viscous. Scrapers are equally important in wastewater treatment stations in industries such as chemical, printing and dyeing, papermaking, and food. For example, in the sedimentation tank of a paper mill, there are pulp fibers in the sludge, which can be efficiently removed by a bridge scraper; The wastewater and sludge from food factories contain a lot of organic matter and are prone to decay. Therefore, the scraper needs to operate more frequently and discharge the sludge in a timely manner to prevent odors.
waterworks
The sedimentation tank of the water plant also requires a scraper. After coagulation and sedimentation of raw water, there will be alum sludge at the bottom of the tank. If these sludge are not cleaned in time, it will affect the quality of the effluent. The sedimentation tank of a water treatment plant generally uses a center driven or peripheral driven scraper, which is required to scrape the mud clean and not stir the bottom of the tank, ensuring that the effluent water is clear and meets the standard.
Metallurgical and mining industries
The wastewater from the metallurgical and mining industries contains a large amount of sediment and metal debris, and the sludge in the sedimentation tank is large and relatively hard. At this point, a sturdy and durable scraper is needed, such as a peripheral transmission scraper or a heavy-duty bridge scraper, which can withstand large loads, scrape hard sludge to the discharge port, and reduce the wear and tear of the equipment caused by sludge.
Agriculture and animal husbandry
Scrapers can also be used in sedimentation tanks for agricultural irrigation or wastewater treatment tanks for aquaculture. The wastewater from animal husbandry contains a large amount of feces and organic matter, and sludge is prone to accumulate. Small bridge or central transmission scraper machines can be used to clean it in a timely manner to prevent water quality deterioration and achieve water resource recycling.
5、 Finally, let me say a few words
Although the scraper is not as eye-catching as other environmental protection equipment, it is a real "cleaner" in the water treatment process, which is related to the operating efficiency and effluent quality of the sedimentation tank. Understanding the classification of mud scraper machines can help us choose the right equipment; Understand the working principle and better comprehend its function; Mastering the operating precautions can make the equipment last longer and more stable; Knowing its application scenarios, one can understand its importance in the field of environmental protection.
When using a mud scraper in daily life, it is necessary to do a good job of daily inspection and maintenance, and deal with problems in a timely manner, so that it can work diligently and contribute to water quality purification. If you encounter special situations in practical operation, in addition to referring to these knowledge, you also need to handle them in conjunction with the equipment manual and on-site conditions to ensure safety and effectiveness!
