Method for judging abnormal change position of rigidity of rotary mechanical supporting system

Abstract

A method for judging the abnormal change position of the rigidity of a support system of a rotary machine comprises the following steps: acquiring the vibration amplitude of each measuring point through a vibration sampling analyzer, and searching the abnormal position of the rigidity of the support system, and specifically comprises the following steps: respectively mounting the measuring points at the central symmetry structure positions of a rotor in a top view of the support system to form area blocks; obtaining the vibration amplitude of each measuring point, and drawing the vibration amplitude change trend of each region block along the height direction; comparing the difference of the vibration amplitude change trend lines between the area blocks at the mirror symmetry positions; comparing the differences of the reference vibration amplitude trend lines; according to the difference between the two comparisons, the area and the height of the position where the support rigidity is weak or abnormal can be determined. According to the invention, the defect or damage position in the rotary shaft supporting system of the rotary power equipment of the thermal power plant can be accurately positioned on site.

Description

Technical Field

[0001] The present invention belongs to the technical field of vibration testing and vibration analysis of rotating machinery, and specifically relates to a method for judging the position where the rigidity of the support system of a rotating machinery changes abnormally. Background Art

[0002] There are a large number of large-scale rotating power machinery in thermal power plants, and the shaft support systems of each rotating power machinery are all structures stacked layer by layer, and the structure is relatively complex with many mating contact surfaces and fastening components. After a long period of continuous operation, defects such as loosening and deformation may occur in each mating contact surface and fastening component, resulting in a change in the support rigidity of the shaft support system, increasing the bearing vibration of the rotating power machinery, and affecting the safe and reliable operation of mechanical equipment. In this regard, relevant standards and requirement values for the vibration of the support system of rotating machinery are proposed in the national standard GB / T 6075. Because the working conditions of the rotating power machinery in thermal power plants are harsh and changeable, and the equipment is surrounded by high temperature, high pressure, corrosive gases, dust and other environments, the probability of defects such as corrosion, deformation and damage of the support system is greatly increased. Therefore, a method is needed to accurately locate the position where abnormal changes occur in the shaft support system of the rotating power equipment in thermal power plants on site, so as to provide technical guidance for the maintenance work of the rotating machinery in the power plant. Summary of the Invention

[0003] The present invention provides a method for judging the position where the rigidity of the support system of a rotating machinery changes abnormally. Through the present invention, the position where abnormal changes occur in the shaft support system of the rotating power equipment in thermal power plants can be accurately located on site, so as to provide technical support for the maintenance work of the power plant, reduce maintenance man-hours and improve maintenance efficiency.

[0004] To achieve the above object, the present invention adopts the following technical means:

[0005] A method for testing and judging the position where the rigidity of the support system of a rotating machinery in a thermal power plant changes abnormally includes the following steps:

[0006] (1) Arrange the installation test points as shown in Figure 4 and, according to the symmetry of the geometric structure of the bearing support system, form different regional blocks with the test points at different positions; arrange a rotational speed sensor beside the rotor;

[0007] (2) Start the rotating mechanical equipment, and continuously collect data for more than 15 minutes after its rotational speed and equipment operating conditions reach stability, where the sampling rate of the data acquisition analyzer is no more than one group of data per 5 seconds;

[0008] (3) Draw a trend graph of the change in vibration amplitude along the height direction within the regional block from bottom to top according to the test results;

[0009] (4) Compare the vibration amplitude trends of the regions at mirror-symmetric positions; find the trend line that is significantly different from other trend lines in terms of the change trend.

[0010] (5) Obtain the reference vibration amplitude trend line based on national standard requirements and experience summary as shown in Figure 5 the figure. At the same time, compare the vibration amplitude trend obtained from actual measurement with the trend of the reference vibration amplitude changing along the height direction; find the starting position of the significant difference.

[0011] (6) Use the vibration amplitude trend lines of each region block to determine the region blocks with abnormal increase in vibration amplitude. At the same time, compare the position where the vibration trend line of the abnormal region block starts to deviate significantly from the reference curve. According to the above two steps, it can be determined that this region is where the support rigidity changes abnormally, that is, it can be determined that there are defects near this mating contact surface region.

[0012] The beneficial effects obtained by the present invention are as follows:

[0013] 1. By comparing the vibration amplitude trends at mirror-symmetric positions and comparing the actual measured vibration amplitude trend with the reference vibration amplitude trend, the position where the rigidity of the rotating machinery support system in a thermal power plant changes abnormally is judged by comparing the starting position of the abnormal change in the trend.

[0014] 2. Through the present invention, it is possible to accurately locate the position where the defect abnormally changes in the rotating power equipment shaft support system of a thermal power plant on-site, thereby providing technical support for the maintenance work of the power plant, reducing the maintenance man-hours, and improving the maintenance efficiency.

[0015] 3. The present invention is not only applicable to the rotating power equipment shaft support system of a thermal power plant, but also applicable to the shaft support systems of other stacked structures. Through the present invention, the position of the abnormal defect in the support system can be quickly and accurately located, providing a direction for maintenance and replacement.

[0016] 4. By adopting the present invention, on-line measurement can be realized. After combining with software, it can provide effective early warnings in a timely manner and give accurate judgments, providing support for the maintenance of the rotating machinery support system. Description of the Drawings

[0017] Figure 1 It is a schematic diagram of the theoretical model of the forced vibration of the damped system of the rotating power machinery in a thermal power plant.

[0018] Figure 2 It is a schematic diagram of the common support system structure of the rotating power machinery in a thermal power plant.

[0019] Figure 3 It is the response curve of the support system rigidity and the support system displacement within one cycle.

[0020] Figure 4It is a schematic diagram of the measuring point layout and regional block division for the rigidity of the rotating power machinery support system in a thermal power plant.

[0021] Figure 5 It is the reference vibration amplitude trend line of the rotating power machinery support system in a thermal power plant.

[0022] Figure 6 It is the schematic diagram of the actual on-site measuring point layout and zoning.

[0023] Figure 7 It is the comparison chart of the vibration amplitude trends of the measured symmetric position regional blocks.

[0024] Figure 8 It is the comparison chart of the vibration amplitude trend obtained by actual measurement and the change trend of the reference vibration amplitude along the height direction.

[0025] Figure 9 It is to determine the abnormal change position of the rigidity of the rotating machinery support system in a thermal power plant by actual measurement.

[0026] Figure 10 It is a picture of the position where the tie rod bolts of the soleplate are found to be loose on-site.

[0027] Figure 11 It is the comparison chart of the vibration amplitude trends of the symmetric position regional blocks when the on-site actual measurement reaches the qualified vibration level after treatment.

[0028] In the figure, the markings are as follows: 1 is the rotating shaft of the rotating machinery, 2 is the rotation center of the rotating shaft, 3 is the mass m of the rotating shaft support system, 4 is the damping c of the support system, 5 is the rigid ground where the support system is placed, 6 is the rigidity coefficient k of the support system, 7 is the rotational angular velocity w of the rotating shaft, 8 is the rotation radius r of the residual unbalanced mass of the rotating shaft, 9 is the residual unbalanced mass m1 of the rotating shaft, 10 is the rotor, 11 is the bearing bush, 12 is the shaft sleeve, 13 is the bearing housing base, 14 is the soleplate, 15 is the cement platform, 16 is the tie rod bolt, 17 is the bearing housing base bolt, 18 is the shaft sleeve bolt, 19 is the gland bolt, 20 is the vibration sensor, 21 is the rotational speed sensor, 22 is the vibration acquisition and analyzer, 23 is the vibration signal input device, 24 is the rotational speed signal input device, 25 is the regional block A composed of vibration measuring points, 26 is the regional block B composed of vibration measuring points, 27 is the regional block C composed of vibration measuring points, 28 is the regional block D composed of vibration measuring points, 29 is the regional block E composed of vibration measuring points, 30 is the regional block F composed of vibration measuring points. Specific implementation mode

[0029] The present invention will be further described in detail below in combination with cases.

[0030] Embodiment 1

[0031] Figure 1It is a schematic diagram of the theoretical model of forced vibration of a damped system for a rotating power machine in a thermal power plant. For easy understanding, Figure 2 , Figure 2 is a schematic diagram of the common support system structure of a rotating power machine in a thermal power plant. The response curves of the support system rigidity and the displacement of the support system within one cycle are as shown in Figure 3 , where k is the rigidity coefficient of the support system.

[0032] This research process is carried out on the basis of Figure 2 , and the positions of each measuring point are as shown in Figure 4 . On both sides of the rotor 10, starting from the cement platform according to the fixed height position, tie bolts, bearing housing base bolts, bushing bolts, and gland bolts are set. Vibration sensors are grouped and set at the corresponding bolt positions of the cement platform, platen, bearing housing base, bearing mid-plane of the lower bushing, and bearing housing cover of the upper bushing. Due to the height difference at each position, there is also a height difference between the vibration sensors. The present invention uses relative height for discrimination. Specifically, the position with a relative height of zero is the cement platform, the position with a relative height of 100 is the bearing housing cover, and the relative heights of other positions refer to Table 1. Looking from the top view, when arranging the measuring points, the vibration sensors on both sides of the rotor are symmetrically distributed, and the speed sensor is set on the side of the rotor to obtain speed information.

[0033] As shown in the appendix Figure 6 is the actual measuring point layout of the support system rigidity of a rotating power machine in a thermal power plant on-site by the method of this invention patent. Area blocks A and D are a group of symmetric area blocks, area blocks B and E are another group of symmetric area blocks, and area blocks C and F are another group of symmetric area blocks. The actual measurement results of each area block are shown in Table 1.

[0034] Table 1 Actual measurement result table

[0035]

[0036] The information of the acquisition equipment used on-site is as follows: the speed sensor is the American Monado ROS-P optoelectronic speed sensor; the velocity sensor is the Bently bently velocity sensor 9200; the vibration acquisition analyzer is the Shanghai Shuke SK4432 type vibration analyzer, with the sampling frequency set at 2500 Hz and the storage time interval of 3 seconds.

[0037] As shown in the appendix Figure 7 is the trend diagram of the measured vibration amplitude within the area block from bottom to top. According to the comparison of the trend changes, it can be seen that the growth of area blocks A, B, and C is relatively large, and the increase degree of the vibration amplitude at the contact surface between the cement foundation and the platen is abnormally high. According to the analysis of the relationship between the vibration amplitude and the support rigidity, it can be inferred that the support rigidity in this area has abnormal changes.

[0038] As shown in the appendixFigure 8 The measured vibration amplitude trend is compared with the trend of the reference vibration amplitude along the height direction. It can be seen from the comparison that: The regional blocks A, B, and C deviate significantly from the qualified curve, and the abnormal deviation points are the vibration measurement points on the platen; The regional block D deviates from the qualified curve, and the abnormal deviation point is also the vibration measurement point on the platen; The growth rates of the regional blocks E and F are basically smaller than that of the qualified curve, and the increase rate of the vibration amplitude is normal.

[0039] Through Figure 7 and Figure 8 , it can be judged that the trend curves of the regional blocks A, B, and C deviate significantly from the reference vibration amplitude trend curve and are also significantly different from those of the regional blocks E and F. At the same time, it is found that the measurement points with abnormal growth of the trend line are the vibration measurement points on the platen, indicating that the platen support rigidity of the regional blocks A, B, and C has changed abnormally, that is, the connection between the cement platform and the platen has become loose. Therefore, it is judged that the position with abnormal change in support rigidity is as shown in the appendix Figure 9 . After on-site inspection, it is found that 4 tie bolts near the regional blocks A, B, and C of the platen have become loose, as shown in the appendix Figure 10 . After the maintenance personnel stopped the machine to replace the new tie bolts and tighten them, the vibration trend of each point of the bearing support system is as shown in the appendix Figure 11 , and the vibration of each point of the support system reaches the qualified value.

[0040] The basic principle of the present invention is as follows:

[0041] As Figure 1 shown, the differential equation of motion can be derived from the force balance, and the meaning of the derivation formula in the following text is shown in Figure 1 .

[0042] mx(t)″ + cx(t)′ + kx(t) = P0cos(wt) (a)

[0043] P0 = m1×r×w 2 (b)

[0044] According to formula (a), it can be seen that it is a second-order non-homogeneous differential equation with constant coefficients. Therefore, according to the characteristics of the equation, it can be assumed that its particular solution is:

[0045] x(t) = Acos(wt) + Bsin(wt) (c)

[0046] Substitute formula (c) into formula (a), and we get

[0047] [(k - mw 2 )A + cwB]cos(wt) + [(k - mw 2 )B - cwA]sin(wt) = P0cos(wt) (d) In order to make equation (d) hold, the coefficients must be made equal. Therefore, there is

[0048] (k - mw 2 )A + cwB = P0 (e)

[0049] (k - mw 2 )B - cwA = 0 (f)

[0050] According to equations (e) and (f), we can obtain

[0051]

[0052] Substitute equations (g) and (h) into equation (c) to get

[0053]

[0054] Equation (i) can be simplified to the particular solution in general form as equation (j)

[0055] Particular solution in general form: x(t) = Xcos(wt - ρ) (j)

[0056] The amplitude term in equation (j) is:[[]]

[0057] The lag angle term of the particular solution is:[[]]

[0058]

[0059] Where: x(t) is the displacement equation of the support system, which is a function of time;

[0060] x(t)' is the first derivative of the displacement equation of the support system with respect to time t;

[0061] x(t)'' is the second derivative of the displacement equation of the support system with respect to time t;

[0062] t is time;

[0063] m is the mass of the support system;

[0064] c is the damping of the support system;

[0065] k is the stiffness coefficient of the support system;

[0066] P0 is the amplitude of the exciting force of the rotating shaft;

[0067] w is the rotational angular velocity of the rotating shaft;

[0068] m1 is the residual unbalanced mass of the rotating shaft;

[0069] r is the radius of rotation of the residual unbalanced mass of the rotating shaft;

[0070] w n is the natural frequency;

[0071] ζ is the damping ratio.

[0072] As can be seen from equations (j) and (k), the stiffness coefficient k of the support system affects the vibration amplitude term X. That is, when the stiffness of the support system changes, it will affect the change of the vibration amplitude. If other conditions are basically the same and the vibration amplitude changes violently, it can be inferred that the stiffness coefficient k in this area has changed abnormally. Therefore, it is possible to inversely infer whether the support stiffness has changed abnormally by testing the change of the vibration amplitude. According to theoretical calculations, under the conditions that the exciting force (residual unbalanced mass, residual unbalanced position, and rotational speed), the mass of the support system, and the system damping remain unchanged, the response curve of the support system stiffness and the displacement of the support system within one cycle is as Figure 3 shown. It can also be seen from the figure that as the stiffness of the support system changes, the vibration amplitude changes significantly.

[0073] The support system of the rotating power machinery in a thermal power plant has a structure of stacked layers, and has a basically symmetric structure in both the horizontal and vertical directions. Therefore, for the boundary conditions where the exciting force, the mass of the support system, and the system damping are basically the same within the symmetric structure area block, it can be inferred that if there is an obvious difference in vibration, it means that the support stiffness in this area has changed significantly. As Figure 2 shown. According to the theory of elasticity, as the number of support members increases layer by layer, the stiffness of the entire system will decrease. Therefore, when gradually increasing the support members upward from the cement support platform, the support stiffness of the system will gradually decrease. Therefore, it is possible to infer whether the support system stiffness has changed abnormally by simultaneously testing the vibration amplitudes at various positions of the support system, analyzing the change trend of the vibration amplitude along the height direction, and comparing the vibration amplitude differences at the mirror positions of the symmetric structure.

Claims

1. A method for judging the position where the rigidity of the support system of a rotating machine undergoes abnormal changes, characterized in that, The steps include the following: (1) Locate the rotor position in the top view of the rotating machinery. With the axis of the rotor as the center, arrange vibration measurement points at the positions of each symmetric contact surface and form a regional block with each vibration measurement point. Arrange a rotational speed sensor beside the rotor; (2) Start the rotating machinery equipment. After its rotational speed and equipment operating conditions reach stability, continuously collect data for more than 15 minutes to obtain the vibration amplitudes of each measurement point; (3) Draw a graph showing the change trend of the vibration amplitude in the height direction within the regional block from bottom to top according to the test results; (4) Compare the vibration amplitude trends between the regional blocks at mirror-symmetric positions, and find out the trend line that is significantly different from other trend lines; (5) Compare the curve with abnormal change trend with a preset reference vibration amplitude trend graph to find out the starting position of the obvious difference; (6) Find out the area where the vibration amplitude within the regional block deviates from the reference vibration amplitude trend graph and determine the height of the starting position of the abnormal change, so as to determine the position where the rigidity of the rotating machinery support system has an abnormal change.

2. The method according to claim 1, wherein The vibration amplitudes obtained in step (2) are realized by a vibration sampling analyzer, which is connected to a speed sensor and a vibration sensor, and the vibration sensor is arranged at the measurement point.

3. The method according to claim 1, characterized in that, The comparison of the vibration amplitude trends between the regional blocks at mirror-symmetric positions in step (4) is realized by calculating the deviation of the vibration amplitude change trend lines between the regional blocks at mirror-symmetric positions.

4. The method according to claim 1, wherein The comparison of the differences from the reference vibration amplitude trend line in step (4) is realized by comparing with a preset reference vibration amplitude trend line.

5. The method according to claim 1, wherein The comparison of the differences from the reference vibration amplitude trend line in step (5) is realized by comparing with a preset reference vibration amplitude trend line.

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