A derrick hoisting system and a method of handling resonance in a coal conveyor trestle

Abstract

The application discloses a kind of derrick hoisting system and coal handling trestle resonance processing method, comprising: a. using optical vibration measurement method to obtain the basic frequency characteristic of derrick hoisting system or coal handling trestle, that is, string vibration natural frequency, string vibration natural frequency includes first-order natural frequency, denoted as f x1 ; b. the natural frequency of derrick hoisting system or coal handling trestle is calculated using finite element model, the natural frequency of first-order vibration, i.e. fundamental frequency is calculated;In the shutdown state of derrick hoisting system or coal handling trestle, the dynamic characteristics of building structure are tested using transient impact excitation method or natural environment excitation method, and the calculation results of the fundamental frequency of the structure are verified by experiment;And determine the natural frequency fundamental frequency interval of building structure, and c. according to =, wherein L is the length of the string, T is the tension of the string, and δ is the linear density of the string, by changing the effective length of the string in the derrick hoisting system and coal handling trestle, the natural frequency of the string is changed, so that, thus eliminating resonance.

Description

Technical Field

[0001] This invention belongs to the field of vibration control technology, specifically relating to a method for dealing with resonance in a derrick hoisting system and a coal conveying trestle. Background Technology

[0002] Material transport in coal mine construction is divided into vertical hoisting and inclined transport, which correspond to the existing headframe hoisting system 10 (see...). Figure 1 ) and existing trestle belt conveyor system 20 (see Figure 2 The working principle of the derrick hoisting system is that the cable 11 (chord vibration part) is used as a fulcrum through the top sheave 13 at the top of the derrick 12. The hoist (winch) 14 on the ground pulls the cable to lift the hopper 15 to the ground. The coal conveying trestle uses a belt 21 about 3m wide to transport coal blocks. The belt is a closed-loop flexible material. The belt conveyor is driven by the head 22 (rotating motor, supported on the trestle support 23) at the end of the trestle to move the belt and the driven wheel 24 (supported on the trestle support 23). The belt frame on the trestle is equipped with freely rotating inclined rollers 25 to support the belt for coal transport. The belt below the belt conveyor only bears tension. During normal operation, at any time, the cable between the top sheave and the ground hoist and the belt part below the coal conveying belt can be approximated as a chord structure with fixed constraints at both ends, which will generate a standing wave effect when excited. Current design codes do not consider the string vibration of such structures, causing the string vibration (lateral vibration) excited during operation to resonate with the structure's natural frequency. This results in excessive vibration amplitude, reducing the structure's fatigue life and affecting structural safety. Existing methods for mitigating vibration in such structures employ structural reinforcement to improve stiffness and strength and prevent structural failure.

[0003] For structural resonance caused by lateral (chordal) vibration, existing methods have not identified the mechanism of resonance. Simply reinforcing the structure using traditional methods can solve the vibration problem if the reinforcement changes the structure's natural frequency significantly, thus altering it considerably from the chordal vibration frequency. However, if the change is small or coincides with other natural frequencies of the chordal vibration, the effect is greatly reduced. In existing industrial building structures, due to technological limitations, the efficiency of changing the natural frequency through local reinforcement is very low. For example, replacing a 100mm channel steel with a 200mm channel steel in a trestle bridge might only result in a 10% change in natural frequency.

[0004] Therefore, new technologies and equipment are needed to at least partially address the shortcomings of existing technologies. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for handling resonance in a derrick hoisting system and a coal conveying trestle. To achieve the above objectives, the technical solution adopted by this invention includes:

[0006] A method for handling resonance in a derrick hoisting system and a coal conveying trestle, characterized by comprising:

[0007] a. Optical vibration measurement methods are used to obtain the basic frequency characteristics of the string vibration of the hoisting system or coal conveying trestle, that is, the natural frequencies of the string vibration. The natural frequencies of the string vibration include the first natural frequency, denoted as f. x1 ;

[0008] b. Calculate the natural frequencies of the hoisting system or coal conveying trestle using a finite element model, and calculate the natural frequency of the first-order vibration, i.e., the fundamental frequency f. j1 With the hoisting system or coal conveying trestle in a stopped state, the dynamic characteristics of the building structure are tested using the transient impact excitation method or the natural environment excitation method, and the first-order natural frequency f of the building structure is measured. c1 And determine the fundamental frequency range of the building structure's natural frequency. -3δ, +3δ], where δ=∣f c1 -f j1 |; and

[0009] c. According to = Where L is the chord length, T is the tension of the chord, and δ is the linear density of the chord. By changing the effective length of the chord in the hoisting system and the coal conveying trestle, the natural frequency of the chord is changed, thus... [ -3δ, +3δ], thereby eliminating resonance.

[0010] According to an embodiment of the present invention, the method for handling the resonance of the derrick hoisting system and the coal conveying trestle further includes using the following formula to verify the natural frequency of the string vibration measured in step a:

[0011] =

[0012] in: Let be the nth natural frequency, L be the string length, T be the string tension, and δ be the string linear density.

[0013] According to an embodiment of the invention, in step c, the string is divided by providing at least one set of guide wheels in the string, thereby changing the natural frequency of the string vibration.

[0014] According to an embodiment of the present invention, the guide wheel is a double-wheel guide wheel, a single-wheel guide wheel, or a wheel system combination.

[0015] According to an embodiment of the present invention, the guide wheel is in rigid contact with the string in the derrick hoisting system or coal conveying trestle, or in contact with the string through a vibration isolator.

[0016] According to an embodiment of the present invention, the guide wheel provides lateral constraint on the string.

[0017] According to an embodiment of the present invention, in step a, the optical vibration measurement method includes measuring vibration using a laser vibrometer or a high-speed camera. Attached Figure Description

[0018] The following description, with reference to the accompanying drawings, will detail some specific embodiments of the invention by way of example and not limitation. The same reference numerals in the drawings denote the same or similar parts or portions. Those skilled in the art will understand that these drawings are not necessarily drawn to scale. The objectives and features of the invention will become more apparent from the following description taken in conjunction with the accompanying drawings, in which:

[0019] Figure 1 This is a schematic diagram of the structure of a derrick hoisting system in the prior art;

[0020] Figure 2 This is a schematic diagram of the structure of a conventional coal conveyor belt system.

[0021] Figure 3 A schematic diagram illustrating how adding guide wheels to the derrick hoisting system to change the effective length of the transverse chord vibration is a method for handling resonance in the derrick hoisting system and coal conveying trestle according to an embodiment of the present invention.

[0022] Figure 4 A schematic diagram illustrating the method for handling resonance in the derrick hoisting system and coal conveying trestle according to an embodiment of the present invention, showing how adding guide wheels to the coal conveying belt changes the effective length of the transverse chord vibration;

[0023] Figure 5 A schematic diagram of a double-wheel guide wheel structure for a method of handling resonance in a derrick hoisting system and a coal conveying trestle according to an embodiment of the present invention; and

[0024] Figure 6 This is a schematic diagram of a single-wheel guide wheel structure for a method of handling resonance between a derrick hoisting system and a coal conveying trestle according to an embodiment of the present invention. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The content shown is intended to fully illustrate the content of the present invention, but is not intended to limit the present invention.

[0026] Studies have shown that string vibration is the root cause of resonance. This invention starts from the mechanism of string vibration (lateral) and, without changing the original building structure, adopts a method of significantly increasing the natural frequency of string vibration to move it away from the natural frequency of the building structure, thereby eliminating and avoiding the occurrence of resonance.

[0027] More specifically, the method for handling resonance of the derrick hoisting system and coal conveying trestle in the implementation scheme may include using optical vibration testing methods such as laser vibrometers or high-speed cameras to obtain the chords (11, 21) (belts or cables, see appendix) of the derrick hoisting system or coal conveying trestle. Figure 3-6 The fundamental frequency characteristics of a string vibration, namely: the natural frequencies of the string vibration, mainly the first order, denoted as: The natural frequency of the string vibration can be verified by theoretical calculation.

[0028] For example, according to the theory of string vibration, the natural frequency of the transverse vibration of a string with fixed constraints at both ends can be expressed by the following equation (1):

[0029] = Formula (1)

[0030] in: Let L be the nth natural frequency, L be the string length, T be the string tension, and δ be the string linear density. The vibration frequency of the first natural frequency is... = The natural frequency of transverse string vibration can be theoretically verified using the above formula.

[0031] Then, the natural frequencies of the building structure (the hoisting system and the coal conveying trestle) are measured. Specifically, the natural frequencies of the structure can be calculated by establishing a finite element model, including calculating the natural frequency of the first-order vibration, i.e., the fundamental frequency. The finite element model is well-known in this field, and its establishment and operation will not be elaborated upon here. Subsequently, with the building equipment in a shutdown state, the dynamic characteristics of the building structure were tested using either transient impact excitation or natural environmental excitation methods, and the first-order natural frequency of the structure was measured. Based on the above calculations and tests, the fundamental frequency range of the building structure's natural frequency was determined. -3δ, +3δ], where δ=Ⅰ - I.

[0032] When the string resonates with the structure Falling within the aforementioned inherent frequency fundamental frequency range, that is To prevent or eliminate resonance, the natural frequency of the string vibration can be changed. This ensures that it does not fall within the aforementioned inherent frequency range.

[0033] According to the above string vibration theory = This formula contains three variables: L, T, and δ. Since T is related to the weight of the transported material and involves process requirements, it generally cannot be changed. δ is the physical property of the belt, which can be changed, but requires process modification, thus incurring significant time and economic costs. The variable L is the chord length. When L decreases, the natural frequency of the transverse chord vibration can be effectively increased, thereby avoiding the natural frequency range of the building structure. This approach has advantages such as simple construction, low cost, and good results. Therefore, in this invention, the natural frequency is changed by altering the chord length.

[0034] More specifically, see reference Figure 3-6 , Figure 3 and 4 Schematic diagrams of the derrick hoisting system 10' and the coal conveying trestle 20' according to embodiments of the present invention are shown respectively. As shown, at least one set of guide wheels (16, 26) can be added in the middle of the chord. The guide wheel shafts can be fixedly constrained to the structure through the support structure (17, 27) to achieve the purpose of dividing the chord: if the guide wheels can be located in the middle of the chord, the natural frequency of the chord vibration will double; if three sets of guide wheels are set, the positions will divide the original chord length into four equal parts, and the natural frequency of the chord vibration will increase to four times the original, thus avoiding resonance between the chord and the structure.

[0035] The guide wheel ensures that it provides an equivalent fixed constraint to the string in the lateral direction. A double-wheel structure can be used, with the string passing between the two wheels, and both wheels exerting pressure on the string. (See...) Figure 5 If process conditions permit, a single-wheel guide wheel can also be used to divide the chord length, see [reference needed]. Figure 6 .

[0036] If multiple chords are working simultaneously, such as elevator cables or hoists driving multiple ropes, multiple sets of guide wheels can be used to divide the chord length.

[0037] Example:

[0038] A steel-structured trestle bridge in a coal mine has a span of 20m. When unloaded or transporting a small amount of coal, the trestle bridge exhibits no significant vibration. However, when transporting raw coal to the design load, the steel structure of the trestle bridge vibrates violently, far exceeding the process design value. During shutdown, transient impact excitation was used for testing, and the vibration frequency of the trestle bridge was found to be 5Hz. Then, the modal analysis of the steel structure trestle bridge was performed using the finite element method, and its first natural frequency was found to be 5.01Hz. A laser vibration meter was used to detect the transverse chord vibration frequency of the conveyor belt, which was found to be 5Hz. Therefore, it was determined that the conveyor belt and the steel structure resonated.

[0039] In practice, by adding a guide wheel in the middle of the belt, the natural frequency of the belt's transverse chord vibration was increased to 9.5Hz (obtained using a laser vibration meter), which is much higher than the natural frequency of the trestle structure, and the severe vibration of the trestle eventually disappeared.

[0040] This invention allows for the increase of the natural frequency of string vibration by altering the effective length of the string, thus preventing resonance between the string and the structure. This method reduces the amplitude of structural vibration, improves structural safety, and is both low-cost and highly efficient.

[0041] The design and safety assessment of industrial building structures often rely solely on static load calculations, neglecting the dynamic characteristics of the structural system. This can lead to safety hazards in actual production. This invention provides a new method for the design and safety assessment of industrial building structures, offering strong support for the safety production and renovation design of various industrial and mining enterprises. This invention is also applicable to similar truss structures, such as elevators and cranes.

[0042] Specific implementation methods have been provided above, but the present invention is not limited to the implementation methods described above. The basic idea of ​​the present invention lies in the above basic scheme. For those skilled in the art, designing various modified models, formulas, and parameters based on the teachings of the present invention does not require creative effort. Changes, modifications, substitutions, and variations made to the implementation methods without departing from the principles and spirit of the present invention still fall within the protection scope of the present invention.

Claims

1. A method of handling resonance of a derrick hoist system and a coal conveyor trestle, characterized by Comprising: a. The optical vibration measurement method is used to obtain the basic frequency characteristics of the string vibration of the derrick hoisting system or the coal conveying trestle, that is, the string vibration natural frequency, which includes the first-order natural frequency, denoted as f x1 ; b. Calculate the inherent frequency of the derrick hoisting system or coal conveying trestle by using the finite element model, and calculate the inherent frequency of the first order vibration, i.e. the fundamental frequency f j1 ; In the shutdown state of the derrick hoisting system or coal conveying trestle, the dynamic characteristics of the building structure are tested by using the transient impact excitation method or the natural environment excitation method, and the first order inherent frequency f c1 of the building structure is measured; and determining the natural frequency fundamental frequency interval of the building structure where δ = |f c1 - f j1 |; And c. According to , where L is the length of the string, T is the tension of the string, and p is the linear density of the string, the natural frequency of the string is changed by changing the effective length of the string in the derrick hoist system and the coal trestle, such that resonance is eliminated. Wherein in step c, the string is divided by setting at least one set of guide wheels in the string, thereby changing the natural frequency of the string vibration.

2. The method of claim 1, wherein the method further comprises: Further comprising verifying the measured natural frequency of the string vibration in step a by calculating using the following formula: where: is the nth natural frequency, L is the length of the string, T is the tension in the string, and p is the linear density of the string.

3. The method of claim 2, wherein the method further comprises: The guide wheels are double-wheel guide wheels, single-wheel guide wheels or wheel combination.

4. The method of claim 1, wherein the method further comprises: The guide wheels are in rigid contact with the string in the derrick hoisting system or coal conveying trestle or are in contact with the string through a vibration isolator.

5. The method of claim 1, wherein the method further comprises: The guide wheels constrain the lateral direction of the string.

6. The method of derrick hoist system and coal trestle resonance handling of claim 1, wherein, In step a, the optical vibration measurement method includes using a laser vibration meter or a high-speed camera to measure the vibration.

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