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33 questions for you to fully understand machine sand and processing technology
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机制砂

1. What is machine sand?

Answer: Machine sand refers to sand processed by sand making machine and other auxiliary equipment, which can be processed into sand of different rules and sizes according to different process requirements.

2. What equipment are usually required for machined sand production lines?

A: Machine sand production line usually requires sand making machine, vibrating feeder, jaw crusher, cone crusher, impact crusher, vibrating screen, belt conveyor, sand washing machine and other equipment. According to different process requirements, Various types of equipment are combined to meet the different process requirements of customers.

3. Advantages of machine-made sand over natural sand

Answer: 1) In terms of stable supply: due to years of mining, natural sand resources are becoming less and less, supply is in short supply, prices are soaring, and supply and quality are not guaranteed; while machine-made sand has sufficient raw materials, urban construction waste (construction waste), and crushed stone tail Materials, scraps, stone chips, gravel, mine tailings, etc. can be used as raw materials for machine sand.

2) Price: The price of mechanical sand varies from place to place, but it is basically much cheaper than river sand. Compared with river sand, machine sand is about 20 yuan cheaper per ton. In addition, the profit of machine-made sand is also considerable. At the scale of 2,000 tons / day and calculated at the current market price, the estimated gross profit is more than 1 million yuan per month.

3) Environmental protection: Traditional sand production does bring environmental problems such as dust pollution. However, with the continuous improvement of sand making technology, the production is now basically a fully enclosed structure, and each machine port has a water spray setting. Spillover, and the environmentally friendly dry process does not require water washing, and does not produce problems such as sewage, silt, and dust.

4) In terms of adhesion and life: When the granularity of machine-made sand is used for structural bonding such as cement, it often has better adhesion, more compression resistance and longer service life.

4. What are the main advantages of the dry production process?

Answer: The main advantages of dry production process are:

1) The moisture content of the produced sand is low, generally less than 2%, and commercial and dry-mix mortars can be used directly.

2) The stone powder content in the finished sand is adjustable and controllable, and the centralized recovery can be comprehensively utilized to reduce dust emissions.

3) Little or no water is used in the production process, saving water resources and protecting the environment.

4) Easy centralized operation control and automatic management.

5) It is not affected by the drought and cold season, and can continuously produce all year round.

5. Why are wet processes becoming less and less used?

Answer: The main reasons are:

1) Consumption of a large amount of water, 1t of sand and gravel need 2-3.5m of water;

2) The product has high content of sand and water, and must be dehydrated, and dry-mixed must be re-dried;

3) The sand fineness modulus of the product is too coarse, and the sand output is low;

4) Produce a large amount of mud powder sewage, pollute the environment, and stone powder is not easy to recycle;

5) There are many types of infrastructure investment and equipment, and the production cost of machined sand is high;

6) Production is not normal in arid and rainy areas or during icing season.

机制砂生产线

6. What are the characteristics of the semi-dry sand making process?

A: The semi-dry production process is relatively wet production. The biggest feature is that the mud and stone powder on the surface of the sand making raw materials are washed away with water. Part or all of the finished sand is no longer washed, so the water consumption is relatively small. Less loss and lower water content. However, this sand and gravel production process still requires more water resources, and the sewage treatment device must still be equipped, but the specifications are much smaller. Its investment cost is less than wet method and more than dry method. The content of finished sandstone powder is between the two, and the running cost is also between the two.

7. What is the mechanized sand methylene blue (MB) value?

Answer: It is an indicator used to determine whether the content of particles with a particle size of less than 0.075mm in the machined sand is mainly soil or stone powder with the same chemical composition as the processed parent rock. The methylene blue value of the machine sand requires MB≤1.4, and it should be controlled below 1.0 as well.

8. Why do we need to humidify and mix the finished sand?

Answer: In the production process of machine-made sand, the finished machine-made sand is humidified and mixed, which can make the water content of the machine-made sand reach a saturated surface and dry state, which is conducive to the control of the water consumption of the subsequent concrete mixing and can reduce the segregation during transportation. And flying dust.

9. Why is the fineness modulus of machine sand unstable?

Answer: During the production process, the lithology, moisture content and gradation of the feed are easy to change, and problems such as hole plugging and damage will occur during the screening process. The efficiency and parameters of the crushing and dust removal equipment are also unstable, which may easily cause the sand fineness model of the machine. The number is unstable.

10. Can waste concrete and masonry be used for production mechanism sand?

Answer: Waste concrete, masonry and industrial waste slag go through special equipment through sorting, cleaning, crushing, screening and other processes to produce machine-made sand. However, the current industry is mainly used to produce recycled coarse aggregate.

11. What is the basis of the artificial sand stone production process?

Answer: The basis for selecting dry, wet and semi-dry artificial sand and gravel production processes:

1) First of all, it depends on the area where the mechanism sandstone system is located, the water resources, the cleanliness of the raw materials, and the specific requirements for the aggregate, the content of the sandstone powder and the modulus of fineness. If the original conditions allow, dry production is preferred, followed by semi-dry production, and finally wet production.

2) Considering equipment investment, floor area size, ease of production management, and processing cost of mechanism sand and gravel, dry methods are also given priority, followed by semi-dry methods, and finally wet methods.

12. How to sample machine sand?

Answer: The general method for sampling of machined sand is:

1) When sampling on the stockpile, the sampling locations should be evenly distributed. Before sampling, the surface of the sampling site is scraped out, and then 8 parts of approximately equal amounts of sand are drawn from different sites to form a group of samples.

2) When taking samples from the belt conveyor, the feeder should be used to periodically extract about 4 equal amounts of sand at the outlet of the belt conveyor tail to form a group of samples.

3) When sampling from trains, cars, and cargo ships, extract approximately 8 parts of sand from different parts and depths to form a group of samples.

13. What are the main detection methods for the content of mechanism sandstone powder?

Answer: The content of machined stone powder generally includes two test methods, water washing method and dry sieve method. The representative is American ASTMC136 or AASHTOT27, which is suitable for dry sieve, ASTMC117 or AASHTOT11, and suitable for water sieve. However, in China, cement aggregate aggregates or asphalt pavement aggregates have always been used, and the dry sieve method is used directly. The 0.075mm sieve throughput is determined without washing, so the accuracy is poor. The dry sieve method is mainly applicable to aggregates for cement concrete, and it needs to be comprehensively evaluated in combination with the test results of methylene blue value.

14. What are the main methods of stone powder separation?

Answer: From the perspective of the development of industrial process equipment: the current methods for removing excess stone powder from undisturbed sand mainly include water washing hydraulic classification method, high-frequency sieve mechanical sieving method and powder selection and dust removal wind classification method.

15. How to adjust the gradation index of the gradation index of mechanical sand particles?

Answer: Grain gradation of machine sand can be achieved by adjusting the feed gradation, feed volume, crusher speed, screen size, etc.

16. What factors affect the grain shape of the mechanism?

Answer: The factors that affect the shape of the sand grains of the mechanism are:

1) The lithology of the source rock, such as the development of joints, is not conducive to obtaining a good grain shape;

2) The type of crushing equipment, the impact crusher has a better forming effect;

3) Screen type, for example, square hole controls grain shape better;

17. Why "replace the grinding with breaking, and break more with less"?

Answer: Because the energy utilization rate of crushing is higher than that of grinding, more crushing and less grinding is conducive to saving energy, but it cannot be completely replaced by crushing, because the energy utilization of the two changes inversely as the material size decreases.

18. What are the characteristics of impact breaking "stone hitting stone" and "stone hitting iron"?

Answer: "Stone hitting stone" is suitable for materials with high abrasiveness above medium hardness, such as basalt. The finished product has a better grain type and a slightly higher powder content under the condition of "stone hitting stone". "Stone for iron" is suitable for materials with low abrasiveness below medium hard, such as limestone. Under the condition of "stone hitting iron", the crushing efficiency is high, the wear cost of the surrounding guard plate is high, and the finished product has a slightly worse shape. The most serious wear of "stone hitting iron" is the anvil, so its structural design and casting process are also important factors affecting the efficiency of the sand making machine. In addition, "stone hitting stone" is suitable for shaping, and "stone hitting iron" is suitable for making sand.

19. Why does the impact crusher (sand making machine) use dual motors?

Answer: The use of dual motors has two main functions:

1) Dual motors ensure balanced force on the spindle;

2) Guarantee the speed, energy will be lost during the transmission process. The dual motors ensure high power and ensure the speed;

20. How to solve the difference between the two working currents?

Answer: In dual-drive equipment, the phenomenon that one motor has a lower current than the other is called an inert reaction, and the deviation requirement should not be greater than 10%. Generally, the tension of the transmission belt is adjusted and equalized, the cleanliness of the terminal is checked, and the soft start Problems and other solutions.

21. Why does the impeller rotor need to be statically balanced?

Answer: The impeller rotor does not perform proper static balance correction. The rotor imbalance is large. The centrifugal force generated during operation will cause abnormal vibration and failure of the equipment, abnormal wear of the rotor, and excessive noise. According to industry standards, the impeller rotor balance of the impact sand maker is G16.

22. What are the basic steps of sand machine calibration?

Answer: After replacing the wear parts of the impeller rotor of the impact sand maker, the basic steps of correcting the static balance of the impeller rotor are:

1) Clean the sand and gravel, old worn parts, sundries, etc. on the rotor and accessories, and confirm that they can continue to be used;

2) Reinstall the wear parts and install the rotor on the balance tool;

3) Determine the unbalanced weight and position;

4) Review the balance of the rotor that has been balanced.

23. Factors affecting the efficiency of impact sand making machines?

Answer: 1) Characteristics of raw materials. Material hardness, strength is low, crushability is good, sand making efficiency is high;

2) Influence of water content of crushed materials. Higher water content will reduce sand production;

3) the amount of feed. Generally speaking, the larger the feed amount, the better the crushing effect, but there are extreme points;

4) The speed of the impeller. Generally, the higher the speed, the better the crushing efficiency.

24. Why is the vibration of the impact sand making machine large when it starts?

A: Because the uniform material lining is not formed in the rotor at the beginning of the operation, it is generally caused by a few squares of fine material at the beginning. If you start with the coarse material, it will continue to vibrate for several hours until the rotor is formed Even material lining.

25. What type of gravel screening is used for vibrating screen?

A: The screening equipment mainly used for sand and gravel production are: stick screen, cylindrical screen, circular vibrating screen, linear vibrating screen, high frequency screen and probability screen. The stick screen is mainly used in the soil removal process. It is more common to use a circular vibrating screen and a linear vibrating screen.

26. What factors can cause screen holes?

Answer: 1) The sand and gravel contains a large number of sand and gravel particles with critical separation points;

2) There are many flakes in the sand and gravel; due to the broken rock or the sand and gravel itself, there are more flakes in the sand and gravel.

3) There is more mud in the sand and gravel;

4) The water content in sand and gravel is high.

27. What is the main reason for the screen to break easily?

Answer: The main reasons why the screen is easy to break are:

1) Screen quality or material is unqualified;

2) The tension of the screen is not sufficient enough to cause the screen to vibrate, and it is usually broken or damaged along the edge of the screen or the edge bead;

3) The vibration amplitude of the sieve is too small, which causes the sand particles to accumulate on the screen and quickly damage the screen.

28. What is the relationship between fineness modulus and screen size?

Answer: At present, the general requirements for fineness modulus of machine sand are 2.6-3.0, and it is generally recommended to use a screen size of 3.0mm or 3.5mm. If the stone powder content is large, you can consider using a 2.8mm screen; if it reaches about 2.3, you can consider a long screen, such as 1.7X5 or 1.9X5. As for the type of screen, square hole screen is generally used as much as possible, which is very beneficial for grain shape control; round hole screen or long screen is used as little as possible; it is also necessary to constantly monitor whether the screen is damaged and affect the fineness modulus.

29. What are the wearing parts of impact sand making machine?

A: The standard wearing parts are: cylindrical roller bearings, deep groove ball bearings, thrust ball bearings, expansion sleeves, conveyor belts, oil seals, O-rings.

Non-standard wearing parts are: upper shaft sleeve, lower shaft sleeve (feeding hopper lifting part), shock-absorbing rubber, caster ring guard, upper and lower runner plate, impact block, material cone, wear plate, throwing Material head, blanking lining ring, feeding tube, upper and lower impact guards, hopper liners, divider tray, bulk tray (bulk cone), and peripheral shield.

30. Why is a wheel sand washer generally used in wet production?

Answer: The structure of the wheel type sand washer is simple, the failure rate is much lower than that of the spiral sand washer, and during the washing process, the fine-grained sand and stone powder are less lost, and the output mechanism of the sand is better, and the fineness modulus Easy to control and stable quality.

31. What are the requirements for the apparent bulk density and bulk density of machine sand?

Answer: The apparent density of the machine sand is not less than 2500kg / m3; the loose bulk density is not less than 1400kg / m3; the porosity is not more than 44%.

32. What are the types of rocks in nature?

Answer: There are three types of rocks in nature, namely:

The first type is magmatic rock (igneous rock), which is formed by magma eruption and is generally hard and uniform in texture;

The second type is sedimentary rock (sedimentary rock), which is formed by a series of geological processes such as weathering, handling, sedimentation and diagenesis. It is generally characterized by a layered distribution structure and similar properties in the same period;

The third type is metamorphic rock, which is formed after metamorphic mixing on the basis of existing rocks, and has characteristics of both the above-mentioned rock and itself.

33. Which rocks can be used for the production of machined gravel?

Answer: The raw materials for making sand with machined sand (crushed stone) are usually granite, basalt, river pebble, cobblestone, andesite, rhyolite, diabase, diorite, sandstone, limestone and other varieties. The machined sand made of it is distinguished by rock type, and there are also differences in strength and use.

Shanghai Jianye Heavy Industry Machinery Co., Ltd. Address: No. 1389 Jinqiao Road, Pudong New District, Shanghai , Shanghai ICP No. 08511074 Shanghai Public Network Security No. 31011502002728

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