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Author of adjustment of dynamic imbalance of drying drum in asphalt mixing equipment: Shi Xinma Wenhui, Tai'an Municipal Highway Bureau Abstract: In asphalt mixing equipment, the drying drum often experiences displacement along the longitudinal axis of the cylinder. After several years of practical experience, the author has summarized the adjustment method. This article focuses on the analysis of many factors that cause the displacement of the drying drum along the longitudinal axis of the cylinder, and how to adjust the two aspects. I would like to dedicate this to the readers for reference. Keywords Dynamic equilibrium state, continuous surface friction drive, instantaneous point (line) surface friction drive, impact force 1. Many factors causing the displacement of the drying drum. Regardless of the form of asphalt mixture mixing equipment, the drying drum is an indispensable and important component. A normally rotating drying drum is a balanced system in motion. The drum rotates the drying drum through the drive ring gear between the two roller rings. Under ideal conditions, the roller ring and the four tugs (or support rollers) are in complete surface-to-surface contact. This contact generates continuous friction drive, so that the drum is in a state of dynamic balance during movement. Once external factors break this balance, the drum will move up and down along the longitudinal axis of the drum during movement, which may rub the feeding box and exhaust box, or wear the cooling cover of the drum. Such external factors mainly include the following. The first is the inner cavity factor of the drying drum. The inner cavity of the drying drum is divided into three structural areas, namely the material receiving area, the lifting and throwing area and the discharge area. The spiral blades in the receiving area have a lifting angle of 45° to 60° relative to the longitudinal axis of the drum. The lifting and scattering area is installed parallel to the axis of the dry drum. The discharge area is equipped with planar blades that are 20° to 30° to the axis of the cylinder. During the production process, due to the collision and friction between the aggregates in the cylinder and the blades, the blades in the cylinder are damaged or fall off for a long time, so that the aggregates in the rotating cylinder produce uneven impact on the drying cylinder. This uneven impact force destroys the complete surface-to-surface contact between the roller ring and the tug wheel, forming instantaneous point-to-surface friction. The friction drive generated by continuous face-to-face contact is transformed into the friction drive generated by discontinuous face-to-face contact. This discontinuous friction drive causes the drum to move along the longitudinal axis of the cylinder. Therefore, the dynamic balance of the drum is also broken. Therefore, the blades in the drying cylinder should be inspected regularly. If the wear is serious, replace it with a new one immediately, and if it is open, weld it. In short, the integrity of the blades in the cylinder must be maintained. The second is caused by deformation due to different temperatures. There are mainly the following situations. One is caused by improper operation. Generally speaking, when the temperature of the drying drum reaches 100℃, the material can be fed for production. If the temperature reaches 100℃ without feeding the material for production, the drying drum will be deformed. The second is that after production was stopped, the drying cylinder was deformed due to shutdown when the drum temperature did not drop to 40° to 50°. The third is a sudden power outage during the production process. The above factors can cause local deformation of the drying drum, and this local deformation can also destroy the continuous surface contact between the rolling ring and the tug. The discontinuous surface friction drive breaks the dynamic equilibrium state of the drying drum, so correct operation is crucial. Those who use grid power must cooperate closely with the power department to promptly and accurately communicate the power outage time to the mixing station. Those who use generators must maintain the generator set to ensure normal power supply needs. The third is that the wear of the drying roller was not checked during the maintenance period. For example, the drying drum of the LB3000 mixing equipment produced by Xizhu is equipped with expansion and contraction parts to compensate for temperature deformation between the cylinder and the cylinder hoop. This elastic tangential expansion and contraction part is fixed on the cylinder with bolts. Over time, this bolt will loosen, causing the rolling ring to move, resulting in discontinuous friction drive between the rolling ring and the tug, thus breaking the dynamic balance of the drying drum. In addition, one situation is that the drying drum has not been displaced along the longitudinal axis of the cylinder for a long time, that is to say, neither the abnormal friction sound is heard nor the obvious friction between the thrust positioning roller and the rolling ring of the drying drum is found. We must also be prepared for this situation. It may be that the rolling ring and the tug wheel temporarily maintain the friction drive between the surfaces. Once this temporary maintenance is destroyed, the dynamic imbalance of the drying drum will also occur. Therefore regular inspections are also crucial. In addition, if the foundation is not leveled during the installation process and the drum chassis is not on the same level, it can also destroy the dynamic balance of the drying drum. The dynamic imbalance between the tug wheel and the rolling circle is caused by whatever factors. 2. How to adjust the drying drum. Use a micrometer to measure the distance between the two edges of the rolling ring and the corresponding edge of the supporting roller. Compare the 8 sets of measured data and adjust the gap between them to be as close or the same as possible. First loosen the fastening bolts of the tug bearing seat and adjust it by adjusting the screw. This adjustment method is an adjustment under ideal conditions. Due to the particularity of the mixing equipment and special operations, this method has too many force majeure factors and is relatively time-consuming to adjust. As analyzed previously, the dynamic balance state of the drying drum is destroyed when the continuous surface friction drive between the tug (support roller) and the rolling ring is transformed into a line-surface or point-surface friction drive between the two. Therefore, in actual adjustment, this point-surface or line-surface friction drive can be transformed into a continuous surface-surface friction drive to prevent the drum from being displaced along the longitudinal axis of the cylinder, thereby maintaining the dynamic balance state of the drying drum. In order to facilitate a concise explanation of the adjustment method, first mark each tug of the drying drum and each adjusting screw and draw a concise schematic diagram. Figure 1 is the name of some of the components of the drying drum mentioned in this article. Figure 2 is a simplified front view of the tug and the drive shaft bearing seat connected to the tug. Figure 3 is a simplified top view of the drive shaft and bearing seat connected to the tugboat. First mark the four tugs (support rollers) and the connected drive shaft bearing seats as shown in Figure 3. Facing the burner, the left side of the two tugs at the cold material entry end is No. 1 and the right side is No. 2; the left side of the two tugs at the end where the hot aggregate enters the elevator is No. 3 No. 4, No. 4 is on the right side, where No. 4 is the tug where hot aggregate enters the elevator and the connected drive shaft bearing seat. The adjustment rod on the left side of each tug is marked a, a1, c, c1, e, e 1, g and g1 from the hot aggregate entry end to the hot lift and the cold aggregate entry end. The right side is b, b1, d, d1, f, f1, h and h1. The corresponding bearing seat fastening bolts are A, A1, C, C1, E, E1, G and G1 on the left side, and B, B1, D, D1, F, F 1, H, H1 on the right side. Figure 1 Figure 2 1—Cylinder 2, 3—Rolling ring 4—Tug (support roller) 5—Thrust and positioning rollers 1. Drive shaft bearing box 2. Bearing box base fastening bolts 3.4 Adjustment (section) screw 5. Connector between bearing box and drying drum bottom frame If the drying drum moves upward in the direction of the longitudinal axis of the drum (that is, toward the cold aggregate entry section) Practice shows that the No. 3 and No. 4 tugs and the rolling ring are driven by non-connected surface friction, that is, instant point-to-surface or line-to-surface contact. The adjustment method for this situation is: No. 3 and No. 4 tug wheel bearing seat fastening bolts A, B, C, and D do not move. Loosen A1 and B. 1. C1 and D1 bolts, and the adjustment screws a, b, c, and d of tugs No. 3 and 4 do not move. Loosen the b1 and c1 adjustment screws of tugs No. 3 and 4 (mark the number of threads of each loosened screw), then tighten the adjustment screws a1 and d1 by the corresponding number of threads, and then tighten the loose fastening bolts A, B, C, and D. If the drying drum moves downward in the direction of the longitudinal axis of the cylinder, the adjustment method is exactly opposite to the upward movement, that is, loosen the bolts A1, B1, C1, and D1, keep the adjustment screws a, b, c, and d stationary, loosen the adjustment screws a and d (mark the number of threads of each loosened screw), and then tighten b and c by the corresponding number of threads. There is another situation, that is, the No. 4 tug is close to the hot aggregate elevator and the place where the hot aggregate of the drying drum enters the hot lift. Therefore, the wear of the No. 4 tug is relatively severe, and the No. 4 tug can be adjusted separately to achieve the purpose. If the drying drum moves upward along the longitudinal axis of the cylinder, the adjustment method is: No. 1, 2 and 3 do not move, loosen the fastening bolts D and C of No. 4, while the D1 and C1 bolts do not move, the c 1 and d1 adjustment screws do not move, loosen the c adjustment screw (mark the number of threads of each loosened screw), then tighten the d screw by the corresponding number, and then tighten the bolts D and C. If the drying drum moves downward along the longitudinal axis of the cylinder, the adjustment method is exactly the opposite to that when it moves upward. No. 1, 2 and 3 do not move. Loosen the fastening bolts D and C of No. 4, while the D 1 and C1 bolts do not move. The c1 and d 1 adjusting screws do not move. Loosen the adjusting screw d (mark the number of threads for each loosening screw), then tighten the c screw by the corresponding number, and then tighten the bolts D and C. The above adjustment method is used until the drum runs smoothly, the upper and lower thrusts are pushed, and the positioning roller does not rotate, the drying drum makes no friction sound, and the target is reached. Normally, No. 1 and No. 2 do not need to be adjusted. If after adjusting No. 3 or No. 4, the drying drum has not reached a dynamic equilibrium state, that is, there is displacement along the longitudinal axis, then No. 1, No. 2, No. 3 and No. 4 must be adjusted respectively. Then use a micrometer to measure 8 sets of data on the edge of each tug wheel and rolling ring, and then adjust according to the displacement direction to make these 8 sets of data basically the same or similar as possible. In short, which adjustment method can make the drying drum reach a dynamic equilibrium state in a short time, because before adjustment, the roller ring and the tug are not in continuous surface-to-surface contact. After adjustment, they may temporarily reach continuous surface-to-surface friction drive, and then wear for a long time. This continuous surface-to-surface friction drive may be damaged at all times. Therefore, it is necessary to observe frequently and make timely adjustments if any abnormalities are found. Due to the limited level of the author, there must be omissions and deficiencies in the article, and readers are kindly requested to criticize and correct them.