On-site repair and prevention of roller body of vertical mill

Date: 2019-07-04 Views:

1. Introduction to equipment


Vertical mill is an ideal large-scale grinding equipment, which is widely used in cement, power, metallurgy, chemical industry, non-metal ore and other industries. It is composed of crushing, drying, grinding, grading and conveying in one unit, with high production efficiency, which can grind the lump, granular and powdery raw materials into the required powdery materials. It has the advantages of high grinding efficiency, low power consumption(20%~30%power saving than ball mill), large drying capacity, large granularity of materials allowed for grinding, simple grinding process, small land occupation area, low civil engineering cost, low noise, low wear, long service life and easy operation. With the birth of preheating pre-decomposition technology and large-scale dry cement production line. The vertical mill has been widely used in foreign cement industry, and its technical level has been further improved and improved. Many foreign companies have developed various types of vertical grinding, all of which have achieved success.

2. Equipment problems and cause analysis


As an important part of equipment in modern cement production system, Vertical Mill has expensive spare parts and long supply period. Once damaged, it will have the following impact on production:In the face of long-term shutdown, direct economic loss is huge;When the abrasion of the grinding roll and the lining plate of the grinding disc is excessive, the output will decrease, and the output will decrease until the energy waste is caused;The overall cost of body damage and replacement is higher.

3. The repair mode of equipment problem

(1)Advantage and feasibility analysis of traditional repair mode.


At present, the wear phenomenon of vertical grinding roller body is usually solved by adding copper skin on the spot, local welding repair or off-line surfacing welding. However, it has been proved that it is difficult to guarantee the service cycle of the equipment with copper coating and local welding repair on the spot, and the probability of damage again is very high. The reason is that the effective matching surface can not be guaranteed enough, resulting in the dispersion of the stress point and the excessive local force, and the fatigue deformation of the metal results in the re-damage. Although the accuracy of the return repair is relatively high, the period is long (usually not less than 15 days), which has a great influence on the production. And offline repair involves gas planer costs, metal flaw detection, metal composition analysis, welding. Materials and transport hoisting and other comprehensive costs are also close to hundreds of thousands of yuan, the cost is high.

(2)Advantage and feasibility analysis of field repair mode.


On-site repair is a kind of maintenance mode which has emerged in recent years. The principle is that the polymer composite material repair technology and corresponding parts are used as the repaired mating surface to repair on site without disassembling the equipment. The chemical bond force formed by curing the polymer composite material for repair has formed excellent adhesion force with the repaired metal parts.

4. Demonstration of field repair technology of polymer materials


In order to solve the problem of wear of roller body and roller surface in vertical mill, the company puts forward a corresponding repair scheme according to the situation of field equipment, that is, using the replaced new roll sheet as the grinding tool for restoring the size of the vertical mill body, and using the special material for the vertical grinding machine to restore the size of the worn vertical mill roller body, the company puts forward a corresponding repair scheme according to the situation of the field equipment. The biggest advantage of this scheme is that it does not disassemble the equipment, the repair period is short, the material has excellent adhesion, compression resistance and all kinds of comprehensive properties, the construction is simple, there is no effect of thermal stress on welding, and the repair thickness is not limited.

5. On-site repair construction process

(1) Preparation for work


The construction tools, repair materials and the positioning pins, clamping plates, bolts and the like to be replaced shall be prepared in place, and the roller body shall be fixed and controlled, so as to prevent accidents due to rotation.

(2) Surface treatment


Clean the oxide layer and foreign body on the surface of the roll body with angle mill, clean it with acetone or anhydrous ethanol, clean the inner surface and both sides of the roll surface with the pressure plate surface, and brush the 803 release agent for spare time.

(3) Harmonized materials


Strictly according to the proportion of special materials for vertical grinding, until the color is uniform and consistent, there is no color difference.

(4) Coating material


Apply a layer of material to the repair surface with a scraper on the repair surface, and then apply a layer of material to ensure the adhesion; apply the material layer by layer according to the wear condition of the roller body, so as to meet the requirements of the repair thickness, and apply the surface of the coating to a level.

(5) Installation and fastening


Position the roller skin to which the release agent is applied and tighten the bolts as specified and ensure that there is excess material to be extruded.

(6) material curing


Carry on enough time curing, the specific curing time depends on the field temperature and refer to the material technical data table.

(VII) Operation and maintenance


In strict accordance with the operation and maintenance requirements of vertical mill, fasten the bolt on time (8 / 24 / 72 hours).

6. Improvement measures


After analysis of the cause of wear, it is not difficult to find that the root cause of the wear of vertical mill rollers and accidental damage of the roller/plywood is the problem of mating surface. Because the surface roughness grade of the matching surface of vertical mill roller body is lower, the smaller the effective contact area between the mating surfaces during the fitting process, the larger the pressure, the faster the wear is. In addition, there is a large wave valley on the rough surface. They are sensitive to stress concentration like sharp corner notch and crack, thus affecting the fatigue strength of vertical grinding roller body. Therefore, the newly processed vertical mill body cannot reach 100%surface matching with the roll sheet. To reduce the vertical mill roll. The matching area between the body and the roller is affected by the matching area. It is suggested that the polymer composite material should be used for the pre-protection of the matching surface when replacing the new roller or the new vertical grinding roller body. One is that the surface fit of the two is 100%, and the other is that the concession of the special material for Fushi blue mill can absorb the impact force of the equipment and prolong the service life of the equipment as a whole.

8. Summary


Since the wear of vertical grinding roll body has initiated the field repair technology of polymer composites, it has been successfully repaired online for special vertical grinding, Shen heavy vertical grinding, Lai Xieli mill, Chengdu Yuan, Hefei Hospital and Tianjin Hospital. Through the experience accumulated in the application of vertical mill, its technology can not only be used as an effective maintenance means for the later management of enterprise equipment, but also provide technical support for the preventive management in the early stage of the enterprise, and prolong the service life of the equipment. Compared with the traditional maintenance, the field repair technology of polymer composites not only saves the maintenance time, but also has no abnormal operation after the equipment repair, and meets the requirements of the traditional repair technology, which is the value. It is necessary to popularize the important technical means of maintenance and maintenance of field equipment.

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