This article describes some examples of sand making machine troubleshooting in the equipment working. Give examples of some failures that occur easily in the sand machine. And analyzed the causes of the faults. This article will give the method of sand making machine troubleshooting, as well as the preventive measures.
1. Articulated pipe and chute, screen cloth stoppage
When a dry-mixed mortar company was manufacturing artificial sand, it was found that the fineness of fine sand and coarse sand decreased greatly at the same time. Then found the fine sand chute, the pipe is blocked. Check the screen that they found the most 2.5 mm screen and 1.18 mm screen are clung, and most of the mesh is blocked which leading to no-production and shutdown (see figure 1).
1.1 Failure cause
After analysis, it is found that because the dry-mixed mortar company is a newly-built sand plant. The production personnel has no clear understanding of the dry stone which must be used in dry sand making. They used wet stones with up to 2% water content which results in the manufactured sand containing 1% ~ 1.5% water content. The stone powders are wet with water viscosity is very large, and can’t be pumped through the air.
The sand is held together by very sticky stone dust, which makes the sand lose its fluidity and seals the sand groove and clay pipe. At the same time, a large viscosity of stone powder on the screen, and the more sticky the more. And gradually will screen plug up. In the process of making more and more stone powder stick on the screen, the screen hole is smaller and smaller. Which makes the sand passing through the screen Mesh smaller and smaller. The sand making machine can’t work after the articulated pipe and chute, most Mesh is blocked.
Use a special screen scraper to scrape off the stone dust and sand adhered to the screen, and clean the screen. Cut off the pipe with air at the proper place of the clay pipe and the clay groove to remove the wet sand blocking the pipe. All cleanup, dredge blocked pipes and then feed the dry stone into the sand making machine to make sand.
2. Artificial sand too fine and powder too much
In the process of sand making, a company finds that the sand and gravel is becoming finer and finer, the fineness is becoming smaller and the content of stone powder in the sand is becoming higher and higher. See table 1 (screening results of sand under normal conditions) and table 2 (screening results of abnormal sand). After checking the stone found that the stone is dry, not stone wet, the stone powder can not draw out caused. After checking the sieve, the sieve was found to be normal and the sieve hole was not blocked. All other readings are normal. Reducing the feed rate and increasing the air separation rate did not improve. Because the content of stone powder in the sand is too large, which affects the quality of mortar. We can only stop production to find out the cause of failure.
As can be seen from Table 1, the normal sand fineness is about 2.5, and the remaining percentage of the sifter of 0.075 mm and bottom should be less than 5 %. From table 2, it can be seen that the abnormal sand fineness has decreased to about 2.0, 0.075 mm and the bottom of the two grades of the residual fraction of the screen has been as high as 19% , the stone powder has not been taken away. In this way, according to the original mix ratio of normal sand design production of mortar, powder material more than 14%. Too much powder in the mortar will lead to strength reduction, plastering after the wall will also cause too much powder material shrinkage and cracking.
2.1 Failure cause
After careful investigation, it was found that the warehouse is full of stone powder. But the stone powder warehouse upper limit alarm failure which didn’t timely remind the stone powder full warehouse. The stone powders can not be drawn to the warehouse and have been full of stone powder, directly back to the sand.
Empty the granary of stone powder and continue to make sand. The gradation of sand produced is back to normal, see table 3. Repair the stone powder warehouse upper limit alarm device. the powder hooper rose to the upper limit, immediately stop making sand. Empty stone powder warehouse then sand machine woke on.
3 Hoist failure
A newly-built company made more than 600 tons of sand when it was tested. During the sand making, it was found that the load of the hoist increased sharply, reaching more than 80A. And the hoist was suffocated and stopped working. The damaged parts are shown in figures 2(breaking of the counterweight wheel) and 3(worn through of the engine valve) . Because of the hoist failure, many damaged parts, from the beginning to purchase parts from the manufacturer to complete repair. It takes more than a week, seriously affecting production.
3.1 Failure cause
After investigation and analysis, it was found that the manufacturer did not fill the oil tank after installing the hoist. The maintenance staff of the company also neglected to check whether the oil tank on the top of the hoist was filled before the test because of their lack of experience. The lubrication and cooling role of lubricating oil are seriously inadequate which leading to parts that can not be lubrication and cooling, overheating and damage.
Confirm the damaged parts, immediately notify the manufacturer to send the damaged parts. At the same time request the manufacturer to send professional maintenance personnel to repair the hoist. The company repair personnel, clean up the hoist bucket in the accumulation of material. The alarm program is set in the control software of the machine. The full load of the hoist is 70A, and the safe load is 60 %, which is 42A. Set the emergency stop load at 90 %, or 54A. In this way, the hoist can timely alarm when there is a fault. Timely detection of a fault, it can timely be troubleshooting, to minimize the loss.
4. Pipe and chute wear too fast
A newly-built dry powder mortar company produced more than 6000 ~ 7000 tons of machine-made sand. The pipe and chute were worn through in many places, see figure 4, figure 5. After changing the wear-resisting steel plate, it also did not have much improvement, also be worn out very quickly. Every time cut wear parts, and then weld that takes several hours. It seriously affects production capacity.
4.1 Failure cause
After careful analysis, we found that the parts of the clay groove and clay pipe are worn through by the direct impact of stone and sand. Impact Force is very big, wear very fast, change into wear-resisting steel plate simply also do not have a too big effect.
The company’s maintenance staff to use their brains, analysis if not let the stone, the sand direct impact on these parts, can not reduce the wear and tear it? Therefore, the company’s maintenance staff in these stone, sand direct impact of the site, and welded with clay pipe and groove at an angle of 30 degrees, 3 ~ 5 cm wide wear-resistant steel plate. Let these places to form a layer of accumulated material, so that stone, sand impact deposited here stone, sand, rather than directly impact clay pipe, clay groove pipe wall. Let the Abrasive, rather than grinding the wall. This greatly reduces the wear and tear of clay pipes and GROOVES, improves service life, reduces maintenance time, and increases productivity.
5 Main engine vibration
In a company, after VSI sand making machine working for a period of time, it is found that the main engine vibration amplitude is larger. There is a clear sense of vibration, accompanied by a larger noise. If the small failure does not rule out, there is damage to the equipment caused by a larger failure, leading to the possibility of production suspension.
5.1 Failure cause
After opening the host carefully check, found that the replacement of throw material head, counter-block and other vulnerable parts of the installation is not tidy. The upper and lower runner plates are not even. The impeller wobbles seriously when rotating at high speed, and the balance is destroyed.
Clean up the impellers, re-install the butt end and counter block. Through the balance test, the position of upper and lower runner plates and small vertical plates are adjusted to make the impeller rotate balance after the material accumulated is uniform.
Sand making machine preventive measures
- The dry sand making method must be made with dry stone. The stone moisture content control in less than 1 % and the made sand moisture content control at 0.5 %.
- The powder in the hopper should be poured out in time. The stone powder in the bin should be kept below the half bin and two-thirds at the most. If more than two-thirds of the stone powder warehouse stone powder positions forbid the sand crusher working.
- Before production, all the equipment tanks and filling points must require the repairman to check whether the tank is filled with oil. During the production period, the repairman is required to fill the oil regularly according to the equipment operation instructions, and make a written record for traceability. Production manager to review, confirm. Make sure all the driving parts of the equipment are lubricated and cooled to work normally.
- Feeding quantity, belt speed, sand-making load, and hoist load should be coordinated. The control procedures to set the sand making machine and hoist load alarm. Overload, there should be emergency stop procedures, can stop feeding immediately. In case of overload damage to equipment, causing major failure, affecting production.
- Every time to replace the sand machine easily damaged parts, it must do a good balance test. So as not to shake or vibration too large and damage equipment.
- The bulkhead should be modified, or customized for the bulkhead of machine-made mortar, in order to improve discharge efficiency.
- The soft joint of the pipeline should be refitted to increase wear resistance and reduce maintenance frequency so as to improve production efficiency.