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How to maintain large scale slag mill

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How to maintain large scale slag mill

Release date:2018-08-31 The author: Click:

In recent years, many cement and iron and steel enterprises have introduced large-scale slag vertical grinding micro-powder, and the comprehensive utilization of slag has been completed. But because the wear condition of wear-resistant parts in vertical mill is difficult to control, its severe wear is easy to cause severe shutdown, and bring unnecessary economic loss to the enterprise, so the protection of wear-resistant parts in the mill is the key point of overhaul. After years of research and application of large slag vertical mill in our company, it is found that the wear condition in the mill is directly related to the output value and product quality of the system. The key wear-resistant parts in the mill are the moving and stationary blades of the separator, the grinding roller and the grinding disc, and the louver ring of the air distribution outlet. If these three parts can be preventive protection and repair, not only can improve the operating rate of equipment and product quality, but also can prevent the occurrence of many serious equipment defects.

1 operation principle of large slag vertical mill

The motor drives the mill plate to roll through the reducer, and the hot stove supplies the heat source, enters the inlet below the mill plate from the air inlet, and then enters the mill through the air ring (air distribution outlet) around the mill plate. The material falls from the inlet to the center of the rolling mill, and is dried by hot air. Under the effect of centrifugal force, the material moves to the edge of the mill and is destroyed by being bitten into the bottom of the mill roll. After pulverization, the material continues to move around the edge of the grinding plate, and is carried up by high-speed upward air flow (6-12 m/s) at the wind ring. The large particles are folded back to the grinding plate. The qualified fine powder enters the collector with the air flow through the separator. The whole process is summarized as follows: feeding, drying - grinding - selecting four processes.

2 primary wear parts and protection methods in mill

2.1 determination of fixed time

After feeding, drying, grinding and powder selection, the materials in the mill are worn away by hot air. The longer the time is, the larger the air volume is, and the worse the wear is. Especially in the production, the important parts are air ring (air distribution outlet), grinding roll, grinding plate and separator. These are the most important parts of drying, grinding and collecting. The more timely the abrasion condition is mastered, the more convenient it is to be corrected, and many man-hours can be saved in maintenance. The operation rate of the equipment can be improved and the output value can be added. Taking our LOESCHE vertical mill as an example, at first, in addition to the emergent shortcomings halfway, but also monthly repair as the primary repair and repair cycle. Because in the work, the output value is not only affected by air volume, temperature and wear, but also by other factors. In order to facilitate timely cleaning up the danger, the monthly schedule is revised to the semi-monthly schedule. In this way, no matter whether there are other faults halfway, they are mainly fixed, in the fixed repair vigorously check the danger of faults and key wear parts, timely correction, to ensure that the equipment in the 15-day fixed repair cycle to complete zero fault work.

2.2 check and repair of vane ring

The air distribution orifice louver (Fig. 1) uniformly guides the gas from the annular pipe into the grinding chamber. The angle of the louver blade has an effect on the grinding material circulation in the grinding chamber. Check the air distribution orifice shutter close to the grinding disk, the upper edge and the gap between the grinding disk should be about 15 mm, such as severe wear, need to weld round steel to narrow the gap; together, check the thickness of the side plate, the inner plate is 12 mm, the outer plate is 20 mm, when wear 50%, need to use wear-resistant plate welding patch; key points to check the roller under the shutter, if found air distribution. All the wearing rings are worn out and replaced when they are overhauled.

Because the lower part of the air distribution orifice shutter ring is the primary space to replace the blade, and the blade is wear-resistant, not only heavy, and the number of up to 20 pieces, in the lower part of the wind ring replacement, need to weld the slideway, and need hoisting equipment to help complete. Therefore, timely welding and repairing the wearing parts of the air distribution outlet and adjusting the view of the blade can effectively reduce the number of replacing blades. According to the whole wear condition, replace it once every six months.

2.3 grinding roller and millstone inspection and repair

The slag vertical mill is usually made up of main roller and auxiliary roller. The main roller has the effect of grinding, and the auxiliary roller plays the cloth effect. Our company has three main rollers and three auxiliary rollers. Because it is possible to present dense wear and tear in the roll sleeve or part of the grinding disc, it is necessary to weld on-line from scratch. The welding operation is finished by moving welding machine inside the mill, and there is no need to remove the grinding plate. According to the manufacturer's experience, the worn notch should be welded at 10 mm deep. If the roll sleeve presents cracks, the roller sleeve must be replaced in time.

Once the wear-resistant layer of the roller sleeve is damaged and dropped, the grinding power of the product will be directly affected, and the output value and quality will be reduced. Each roll sleeve needs to be replaced after it is damaged. The working time for replacing the new roll sleeve depends on the operator's experience and proficiency as well as the preparedness of the material. It is 12 hours fast, 24 hours slow or longer. For enterprises, the economy is missing, including the loss of new roller sets and the loss of production. Therefore, taking half a month as the fixed repair cycle, the roll sleeve and grinding disc were inspected in time, and it was found that the thickness of the wear-resistant layer decreased by 10 mm, so the relevant correction units should be organized immediately to conduct on-site welding. Generally, the repairing of grinding disc and roll sleeve can be carried out in three working days, and the whole production line can be checked and repaired systematically. Because of the strong planning, it can effectively ensure the assembly of related operations.

In addition, in the process of inspecting the grinding rolls and discs, we should also carefully inspect other attachments of the grinding rolls, such as connecting bolts, fan-shaped plates and so on, in order to prevent the serious wear and tear of the connecting bolts and other poor connection and fall off in the equipment operation, and then lead to severe grinding rolls, discs wear-resistant layer stuck.

2.4 check and repair of moving and stationary blades of the separator.

LOESCHE double-head bolted basket separator is an air-flow separator. After grinding and drying, the material enters the separator along with the air flow from the lower part. The collected material enters the upper collecting passage through the blade gap, and the unqualified material is blocked by the blade, or falls back to the lower grinding area by its own gravity. The inner part of the separator is mainly a large squirrel cage structure (Fig. 3) of the inversion bin, the outer baffle has a stop blade, and the rolling squirrel cage blades constitute a reverse flow, collect powder. If the dynamic and static blades are not soldered, under the effect of wind and reverse force, it is easy to fall into the mill disc, and the rolling equipment in the mill is jammed, thus constituting a large shutdown. Therefore, the inspection of the dynamic and static blades is one of the key points of the mill internal maintenance.

In the squirrel cage reversing bin of the selector, there are three blades with 200 blades on each floor. When fixing, the blades need to be vibrated one by one with a hand hammer to see if there is any movement. If so, they need to be tightened, marked and welded together. If the blade is found to be severely worn and deformed, the need to withdraw, and according to the requirements of the drawings, the installation of a new scale of the same moving blade, and the need to weigh before the installation, in order to prevent loss of balance.

To view the static blades, remove five moving blades from each layer of the squirrel cage to allow space for investigation of the connection and wear of the static blades.

This article URL:http://en.tsjidongjixie.com/news/385.html

Key words:大型矿渣立磨维护,大型矿渣立磨保养,大型矿渣立磨维护方法

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