Preliminary Analysis of Linear Vibrating Screen Failures

Abstract:
This paper analyzes the causes of screen plate damage in domestic linear vibrating screens and beam failure in imported models. By comparing the advantages and disadvantages of both types, improvement measures are proposed by integrating their strengths. Due to the self-vibration characteristics of linear vibrating screens, component damage is frequent, making up a significant portion of maintenance costs in coal preparation plants. Reducing failure frequency and extending component service life is crucial for minimizing production downtime and lowering operational costs.

At Tunlan Mine Coal Preparation Plant, the main washing system includes 18 linear vibrating screens. After over two years of operation, many issues have arisen, notably:

Frequent screen plate damage in 12 domestic vibrating screens.
A total of 280 stainless steel screen plates (1220mm × 590mm) were replaced over two years, costing about RMB 280,000.

Frequent beam failure in 6 imported vibrating screens.
A total of 43 beams (φ245mm × 10mm) were replaced within the same period, costing approximately RMB 150,000.

These frequent replacements significantly increased labor intensity and time consumption, directly affecting production.

1. Cause Analysis
1.1 Reasons for Damage in Domestic Linear Vibrating Screens
The domestic screens used at Tunlan Mine include 2ZKX and ZKS models, both using 1220mm × 590mm stainless steel screen plates. Each full replacement requires 145 plates. Over two years, each screen had its plates fully replaced about twice. In contrast, no screen plates were replaced on the imported USL3.0×6.0 screens during the same period.

The main causes of damage to domestic screen plates are not normal wear but:

(1) Unreasonable structural design:
Domestic screen plates have weak structures, using only φ10mm steel bars for the frame. The size is long and narrow (1220mm × 590mm), resulting in good elasticity but poor rigidity. During vibration, excessive amplitude causes fatigue failure in the screen bars and frame.

(2) Poor clamping method:
Domestic screens use simple bolts, angle iron, and rubber strips to clamp the plates, without accounting for displacement due to vibration. The screen frame's large gaps, weak rigidity, and plastic deformation during clamping make it prone to shifting and bending. The short bolt-angle iron contact length and loose fit contribute to early loosening, causing extra vibration and fatigue failure.

(3) Poor manufacturing quality:
Large dimensional tolerances and poor welding quality are also contributing factors.

1.2 Causes of Beam Failure in Imported Linear Vibrating Screens
The imported USL3.0×6.0 models have 9 main beams per unit, totaling 54 beams across 6 units. Over two years, 43 beams were replaced—averaging 0.8 replacements per beam, with the most frequently damaged beam replaced twice. In contrast, none of the beams on the 12 domestic screens required replacement.

After discussions with the manufacturer, it was acknowledged that this failure rate was abnormal. Analysis of removed beams showed fatigue fractures. Compared with the domestic design, the root cause was that the 9 beams in imported models were not interconnected. In domestic designs, the beams are joined longitudinally with square and angle steel, enhancing overall strength and resistance to fatigue.

In the imported design, each beam resists bending individually, lacking structural integrity. This leads to larger additional vibrations and fatigue damage. Material selection issues may also contribute.

2. Improvement Measures
Based on the above analysis, each type of vibrating screen has pros and cons. Combining the strengths of both can lead to effective improvements.

2.1 Improvement Measures for Domestic Linear Vibrating Screens
(1) Redesign screen plate and clamping structure based on imported models.
Use 6mm steel plates to weld the frame; adjust plate size to 592mm × 598mm, reducing length and improving rigidity. Use steel-rubber clamping strips for better bolt fit.

(2) Weld channel steel above the 9 beams and pre-drill bolt holes for screen plate fixation.

(3) Fix the screen plate rails onto the channel steel, enabling plate installation.

2.2 Improvement Measures for Imported Linear Vibrating Screen Beams
(1) Accurately measure beam diameter and spacing.

(2) Fabricate auxiliary beams:
Use 8mm thick steel plates for the middle part, welded with φ25mm round steel on both edges. The ends are elliptical plates (8mm thick), curved to a 125mm radius to minimize stress on the main beams.

(3) Remove the center row of screen plates longitudinally to access the beam centers.
Spot weld the auxiliary beams between adjacent beams, then fully weld after alignment. Care must be taken not to damage the original beams. The total added weight is about 80 kg, with negligible impact on performance. One or two rows of auxiliary beams can be added as needed.