ZGS Heavy-Duty Vibrating Screen – Principle and Structure

• operational principle

China has currently produced the ZGS series self-synchronous probabilistic screens. This type of screen operates on the principle of two vibrating motors rotating in opposite directions; the unbalanced force (inertial force) generated by the eccentric masses at both ends of the motors drives the screen machine to undergo reciprocating vibration in a specific direction. When the two vibrating motors rotate synchronously and in opposite directions, the excitation forces produced by their eccentric masses cancel each other out in the direction parallel to the motor axes, while their resultant force in the direction perpendicular to the motor axes combines to form a net force. As a result, the motion trajectory of the screen machine is a straight line. The relative surfaces of the two motor shafts are inclined at an angle in the vertical direction; under the combined action of this excitation force and the gravitational force of the material, the material is thrown upward, jumps, or moves forward in a straight line along the surface, thereby achieving the purpose of screening and grading the material.

Since the vibrating motor is directly fixed to the screen machine’s frame without any elastic connection in between, it forms a single-particle forced vibration system; as the screen machine operates outside the resonance range, it remains insensitive to load variations, ensuring smooth operation. The unbalanced forces generated add up and cancel out, causing the screen machine to undergo linear reciprocating motion, thereby defining its linear vibration trajectory. When material falls into the first layer of the screen from the inlet, large particles—whose size exceeds the aperture spacing of the first screen layer—are separated more efficiently under the vibration of the screen surface; the remaining small-and medium-sized particles are then further separated by the second and third screen layers by the same mechanism. The large particles from the first, second, and third screen layers simultaneously enter the coal crusher inlet for crushing, while the material passing through the third screen layer constitutes the qualified product, which is then fed into the next processing stage.

• design feature

The probability screening system primarily consists of two main components: a vibration damping system and a screening unit.

(1) Shock Absorption System

The ZGS series self-synchronizing probability sieve features a hanging load-reducing system: the sieve body is suspended from a support frame using a rope clamp that connects a shock-absorbing spring, a cable helical fastener, and a steel wire rope; the spring serves to dampen vibrations.

(2) Sieving Unit

The screening unit consists of a screening box, a vibrating motor, and a screening surface.

1. The screening box is the primary load-bearing and operating component of the screening machine; it consists of side panels, a top plate, reinforcing ribs, reinforcing crossbeams, and other parts, and is constructed using a welded assembly. To extend the service life of the machine, wear-resistant rubber plates (10–14 mm thick) are embedded into the side panels; the screening box is connected to the coal discharge pipe using nylon canvas and screws.
2. The vibration motors serve as the source of vibration for the screening machine. The two vibration motors must have identical characteristics; they should rotate smoothly and be securely fastened to the motor base on the screening frame.
3. The screening surface is the primary wear-prone component of the screening machine; it is typically divided into three layers and uses welded or screw-fastened screen bars fabricated from round steel bars of sizes 520 mm and F30 mm (the use of round steel bars simplifies the bar structure and facilitates maintenance). The machine’s side panels are constructed from high-quality steel plate; these side panels are securely fastened to the crossbeam and the exciter base using high-strength bolts, resulting in a rational design that ensures robustness and durability.

III. Maintenance and Adjustment

(1) Lifting of the vibration damping system

Install the vibration damping system on the support frame as specified; suspend the screening machine using steel wire ropes and rope clamps; then adjust the adjustment screw to align the machine’s inlet horizontally and ensure that the four vibration damping springs are subjected to uniform force (this can be verified by measuring the compression height of each spring). If the compression heights are identical, the force distribution is uniform. A permissible tolerance may exist in the compression heights of the springs on the front and rear vibration dampers; however, the compression heights of the two springs in each set must be adjusted to be identical. When a spring requires replacement due to damage, the entire set of springs must be replaced simultaneously.

(2) Pre-installation Instructions for Sieve Plate Installation

1. During installation, place a 5–6 mm thick rubber pad between each end of the screening surface and the crossbeam of the screening machine; when tightening the screws, insert a spring washer and secure them with double nuts to prevent loosening.
2. The length of the screening surface should be less than the distance between the two crossbeams by 1–2 mm, which facilitates the application of an appropriate preload.
3. When fabricating the screen surface, attention should be paid to its structural design. Any of A3 or Grade 20 steel may be used for the surface structure; welding electrodes of type 507 or 506 should be employed, and care must be taken regarding the welding positions during welding.
4. When using rubber elastic screen bars, in addition to tightening the preload nut, adhesive bonding should be applied to the central support beam of the screen bar. After bonding the screen bars, the screen machine should be left undisturbed for one week before use; if the operating temperature is high, it may be left undisturbed for only 3–4 days.

(1) Amplitude adjustment requirements and methods

When the machine is running under no-load conditions, set the screen’s vibration amplitude to 4–5 mm; alternatively, adjust the amplitude appropriately based on the coal quality (for example, use a higher amplitude – generally not exceeding 6 mm – when the coal is dense or the processing volume is high; use a lower amplitude when the coal is loose or the processing volume is low). This approach extends the machine’s service life and reduces noise levels.

The method for adjusting the amplitude involves changing the eccentric coincidence angle between the two motors; however, the coincidence angles of the four sets of eccentric blocks on both motors must be made identical; otherwise, oscillation will occur. After the eccentric blocks have been properly adjusted, a locking nut should be tightened to set the amplitude to the desired value, and then a locking washer should be installed and secured. The amplitude can be directly read from the scale markings on the amplitude indicator plate—the value indicated by the horizontal coordinate of the intersection point of the two lines represents the adjusted amplitude.

The article data is sourced from 360 Wenku.

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