外文翻译-悬臂皮带输送机常见故障分析及处理

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外文资料与中文翻译

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Common Fault Analysis For Belt Conveyer Ir. G. Lodewijks, Delft University of Technology, The Netherlands

Belt conveyers as continuous bulk material conveying machinery have been widely used in the world, electric power plants, metallurgical industry and foodstuff industry as well as in bulk material conveying machinery such as ship loader and bucket-wheel stacker-reclaimer. In the purchase, design, manufacture, erection and operation of this kind of equipment, some of new users are not familiar with them. Common fault causes and their handling methods of this kind of equipment are analyzed and described herein as a matter of experience in the past years and from the point of view of users.

1. Handling of belt deviation of belt conveyer:The belt deviation of belt conveyer during operation is the most common fault. To handle this type of fault, emphasis should be placed on the dimensional accuracy of erection and the routine maintenance. There are several kinds of causes. The differe ntial treatment should be made according to the different causes.

1.1Adjustment of carrying roller set: If the belt of belt conveyer is deviated in the middle of the whole belt conveyer, the position of carrying roller set is adjusted. During the manufacture, the mounting holes on both sides of carrying roller set are machined to slots for the convenience of adjustment. For the specific adjusting methods, see Fig. 1. The specific method is that when the belt is deviated from the side, that side of carrying roller set should be moved forwards the direction of travel, or the other side moved backward the direction of travel. If the belt is deviated from the upper direction as shown in Fig. 1, the bottom position of carrying roller set should be moved to the left side and the upper position of carrying roller set is moved to the right side.

1.2 Installation of self-aligning carrying roller set: There are many types of self-aligning carrying roller sets such as intermediate rotating shaft type, four-link type and edging roll type. The principle is that by utilizing blocking or rotating the rollers in the direction of horizontal plane, the rollers are blocked by rotating or the lateral thrust is produce to make the belt be automatically aligned so as to attain the object of adjustment of belt deviation. It is feasible, in general, to use this method when the whole length of belt of belt conveyer is shorter or the belt conveyer is operated in the bidirection. The causes are that the shorter belt conveyer is easier to be deviated and it is not easily adjusted. Therefore, this method is not used for the longer belt conveyers because use of self-aligning carrying roller sets can have certain influence on the service life of belt.

1.3 Adjustment of positions of head roll and bend pulley: Adjustment of head roll and bend pulley is a key link of adjustment of belt deviation. Since there are at least 2 to 5 pulleys in one belt conveyer, the mounting position of all the pulleys must be perpendicular to the central line along the length of belt conveyer. If the deviation is too large, the belt deviation occurs of necessity. The adjusting method is similar to that of carrying roller set. For head pulleys, if the belt is deviated from the right side of pulley, the bearing block at the right side should be moved forward and if the belt is deviated from the left side of pulley, the bearing block at the right side should be moved forward. For corresponding pulleys, the bearing block at the left side can be also moved backward or the bearing block at the right side moved backward. The adjusting method of tail pulleys is just opposite from that of head pulleys. For the adjusting method, see

Fig. 2. The pulleys are repeatedly adjusted till the belt is adjusted to the expected position. It is preferable to make the mounting position accurate before adjustment of head rolls or bend pulleys.

1.4 Adjustment of belt tensioning device: Adjustment of belt tensioning device is a very important link of adjustment of belt deviation of belt conveyer. Two bend pulleys on the top of counterweighted tensioning device should be not only perpendicular to the direction of the belt along length but also to the gravity vertical, i.e. it is ensured that the shaft center line is horizontal. When the screw tensioning device or hydraulic tensioning device is used, two bearing blocks of tensioning pulley should be synchronously translated so as to ensure that the axial line of pulley is perpendicular to the longitudinal direction of belt. The specific adjusting method of belt deviation is similar to the adjusting method of pulleys.

1.5 Influence of material receiving position at the transfer point on the belt deviation: The material receiving position at the transfer point has a great influence on the belt deviation, especially when the projection of two belt conveyers in the horizontal plane. The relative height of the upper belt conveyer and lower belt conveyer at the transfer point should be normally taken into consideration. The lower the relative height the greater the horizontal velocity component of material and also the greater the lateral impact on the lower layer of belt. In addition, the material is difficult to center so as to make the material at the cross section of belt be skew and finally lead to belt deviation. If the material is deviated from the rig ht side, the belt will be deviated from the left side, vice versa. In the course of design, the relative height of two belt conveyers is increased as practically as possible. The form and dimension of the upper hopper and the lower hopper, chute etc. of bulk material mobile conveying machinery which are limited by space should be more carefully taken into consideration. In general, it is applicable for the width of chute being about 2/3 of that of belt. In order to reduce or avoid the belt from being deviated, the baffles can be increased to block the material and

change the falling direction and position of material. For the uncentering of material on the belt, see Fig. 3.

1.6 Adjustment of belt deviation of bi-directional belt conveyer: Adjustment of belt deviation of bi-directional belt conveyer is relatively more difficult than that of belt deviation of one-way belt conveyer. During the specific adjustment, the adjustment should be done from one direction, and then from the other. During adjusting, it must be carefully observed to the relationship between the travel direction of belt and the tendency of belt deviation. The adjustment should be done one by one. Firstly emphasis should be placed on adjustment of head rolls and bend pulleys. Secondly emphasis is placed on adjustment of the carrying rollers and the material receiving point. In addition, it should be noted that the load is uniformly distributed at the section of the belt along the length when the belt is at the vulcanized joints. When the leading chain is used for traction, the load at both sides should be distributed as equally as possible.

2. Material spillage on belt conveyer: Material spillage on the belt conveyer is a general character. The causes are embodied in several aspects. Therefore, emphasis is placed on strengthening the routine maintenance.

2.1 Material spillage at transfer point: Material spillage occurs mainly at the transfer points such as material receiving hopper and chute. If serious overload occurs on the belt conveyer, the rubber skirt plate of chute of belt conveyer can be damaged. Since the steel plate of chute is far from the rubber skirt plate in the design, the material will be flown out of the chute. The problem can be solved by controlling the conveying capacity and strengthening the routine maintenance.

2.2 Material spillage at the concave section of belt during hanging: The belt at the concave section is floated when the radius of curvature is smaller. At this tome the belt in the form of trough has been changed because the belt has been deviated from the trough carrying roller set. In that case, the angle of trough becomes small so as to make part of the material be split out. Therefore, the bigger radius of curvature at the concave section is used as practically as possible in the design in order to avoid the material spillage. If the concave section is designed according to the section of transition without arc in the mechanical traveling ship loader or stacker-reclaimer in order to shorten its tail car, the material spillage may easily occur when there is less room for selection of belt width.

2.3 Material spillage during the belt deviation: The material spillage occurs during the belt deviation because two edges of belt have changed in height during operation, i.e. one edge is higher and the other is lower. The material is split out from the lower edge. The handling method is to adjust the belt deviation.

3. Abnormal noise: When the belt conveyer is operated, it could sound abnormally from its drive, head roll, bend pulley or carrying roller set. The failure of equipment can be determined according to the abnormal noise.

3.1 Noise occurs when the carrying roller being seriously deviated: When the belt conveyer is operated, the abnormal noise could be produced and accompanied by periodic vibration, especially in the return rolls. The longer the roll and the heavier the deadweight, the higher the noise. There are mainly two causes for noise: one is that the wall thickness of seamless pipe made of carrying roller is non-uniform so as to produce the greater centrifugal force and the other is that during machining, the center of holes of bearing at both ends is greatly deviated from the center of top circle so as to produce the greater centrifugal force. The rolls can continue to use in case the bearings have not been damaged and the noise is allowed to exist.

3.2 Noise occurs when two shafts of coupling being not coaxial: The abnormal noise is produced from the coupling between the high-speed shaft of motor in the drive and that of reducer or from the coupling with brake wheel, it is also accompanied by the vibration that is identical with the rotational frequency of motor. If the noise is produced, the position of motor or reducer is adjusted in time in order to avoid the rupture of input shaft of reducer.

3.3 Abnormal noise of bend pulley and head roll: When the bend pulleys and head rolls are operated normally, the noise is very low. If the abnormal noise is produced, the bearing, in general, may be damaged. If the cackle is produced from the bearing block, the bearing must be replaced.

4. Rupture of shaft of reducer: The rupture of shaft of reducer generally occurs at the high-speed shaft of reducer. The usual fault is that the first-stage shaft of reducer is used as the high-speed shaft of vertical bevel gear shaft. There are mainly two causes for shaft rupture as follows.

4.1 Inadequate design strength of high-speed shaft of reducer: This fault, in general, occurs at the shaft shoulder. Because the transient round angle exists at this place, it is subjected to fatigue damage. If the round angle is too small, the rupture of shaft of reducer can occur in the short time. After shaft rupture, the fracture is generally flush. If this fault is found out, the reducer should be replaced or the design of reducer should be modified.