The linear vibrating screen uses the vibration of the vibrating motor as the vibration source so that the material is thrown up on the screen and moves forward in a straight line simultaneously. It is often used in coal preparation, mineral processing, building materials, chemical industry, and other industries for dry and wet screening of medium and fine-grained waste materials. The screen box of the linear vibrating screen is the main load-bearing component of the vibrating screen. The screen box of the vibrating screen vibrates strongly during work and must bear huge impact loads. Therefore, the screen box’s strength and stiffness greatly influence the performance and life of the whole machine. Suppose the design, main parts installation, use and maintenance of the screen box are unreasonable. In that case, cracks are likely to occur, and long-term overload operation will accelerate the growth of cracks and greatly shorten the service life. So what is the reason for the cracking of the vibrating screen box? Let me analyze it for you below.
Reasons for The Cracking of The Vibrating Screen Box
Loose connection bolts
The bolts at the connection between the screen box side plate and the beam flange are loose.
The bolts that connect the cracks on the screen box’s side plate to the crossbeam’s flange are loose, which will cause excessive stress at the installation hole and produce small local cracks. There is no effective inspection and maintenance system at the site of use, coupled with the fact that the bolts were not found loose in time, and the cracks were increased.
The strength of the equipment is not enough
The strength of the equipment itself is not enough to cause the cracking of the vibrating screen box.
For some previously produced equipment, the steel plate used in the screen box is δ16mm steel plate, and only the reinforcement plate is lined near the vibrator, while the other four main stress points, that is, there are no near the four support feet. During operation, the screen box near the feet will crack several times.
Inconsistent spring compression
Inconsistent compression of support springs can also easily cause cracking of the vibrating screen box.
The vibrating screen body is damped by four rubber springs, and the compression amount of the rubber spring on the front side is inconsistent with the other three. The reason is that the four supports are not in the same plane or the error is too large during installation, and after a period of use, the rubber springs will be aging and other defects, which will cause stress on the shock-absorbing part of the screen body to be different, and the local stress concentration of the side plate will cause cracks.
Unbalanced supporting feet
After running for some time, affected by the unbalanced feeding, the deformation of the shock-absorbing springs of the supporting feet will be inconsistent, resulting in unbalance, irregular vibration tracks, deflection of the vibrating screen, and mutual pull of the screen boxes on both sides. The boxes were torn, and the beams were broken.
Effect of temperature change
In some areas, the temperature in winter is low, and the stiffness of the rubber spring is greatly affected by temperature changes. Due to the low temperature, the internal resistance of the spring increases, the shock absorption effect becomes poor, and the impact on the screen box is increased, resulting in cracks.
The force of the exciter is inconsistent
The screen box deflects due to the failure of the exciter or inconsistent force. Suppose the eccentric block of the vibrating screen exciter becomes loose and falls after the operation. In that case, the difference in the amount of refueling of a pair of bearings during the maintenance process will cause inconsistent resistance, leading to inconsistent amplitude of the vibrating screen. , out-of-sync, and other issues, resulting in irregular vibration trajectories.
Uneven stress on the material
When the feeding belt conveyor is installed and arranged, it is not installed in line with the center line of the screen machine, and the machine head is biased to the side of the cracked side plate so that the material is not evenly distributed on the screen surface. The force is unbalanced after long-term operation. Box cracks appear.
How to Deal With The Cracking of The Vibrating Screen Box?
The cracking treatment of the vibrating screen box is to repair the cracked place. The following are the repair welding steps:
- Before repairing the welding, disassemble the screen box, hang it on the platform, and place the part to be welded as horizontally as possible for welding. Use an angle grinder to polish the cracks and the surrounding mineral powder, oil, rust, and other dirt until the metallic luster is exposed. Drill holes at both ends of the crack to prevent the crack.
- Grind a V-shaped groove with a blunt edge along the center of the crack along the entire length.
- Use the welding rod to make a backing weld first.
- Because of the high rigidity of the components, heat the part to be welded to 150~250℃ with a baking gun before welding, and the preheating range is 70~100mm on both sides of the groove. It can effectively reduce welding stress.
- Segmental, staggered welding and short-arc, narrow bead, multi-layer, and multi-pass welding should be used for electrode welding.
- After welding each layer and each weld seam, hammer the weld seam to reduce welding stress. The cold weld hammering method should be used when the temperature is below 100~150°C—beating as far across the weld as possible to stretch the weld metal as transversely as possible.
- The welded seam is kept warm with glass fiber cotton and cooled slowly. Welding should be carried out continuously as much as possible. If welding must be interrupted, insulation measures must be taken. When welding again, if the weld seam temperature is lower than about 150 ℃, it must be reheated before soldering.
- After welding repair, it should be heated to 400~500℃ and kept for about 1 hour. Then cover the glass fiber wool and cool slowly to room temperature to eliminate the internal stress. After the stress relief heat treatment, the weld seam will be ground and smoothed. All vibration indicators are normal.
How to Prevent The Cracking of The Vibrating Screen Box?
- Rectify the feeding hopper of the vibrating screen and feeding conditions. Regularly measure the height of the shock-absorbing springs of the supporting feet, and check the balance of the supporting feet.
- Regularly check all parts to ensure that there is no fault in the equipment, and when lubricating, each exciter’s bearings are lubricated quantitatively. The resistance of the lubricating grease in each exciter to the exciter is roughly the same, and the vibration track is normal.
- By processing the ribbed plate, using the original bolt holes on the screen box, install the ribbed plate near the four supporting feet to strengthen the strength of the side plate of the screen box.
JXSC Reminds: To improve the service life of the vibrating screen, we must avoid the occurrence of cracks and fracture accidents from the root cause. We must strictly implement the operating procedures at ordinary times but also pay attention to the daily inspection, maintenance and deal with problems on time.