A predictive maintenance method for gas tank piston

Abstract

The present invention belongs to the field of information technology and relates to soft measurement of the maximum tilt height of a gas tank piston, the height around the piston, and the offset of the piston center, as well as piston tilt angle estimation and early warning prompt functions. It is a predictive maintenance method for gas tank pistons. The present invention utilizes measurement data provided by an industrial site, first pre-processes the measurement data, estimates the tilt height using an established piston tilt estimation model, and estimates the height around the gas tank piston using a cubic spline interpolation method. The center offset model is used to estimate the offset of the piston center, and finally, a piston tilt safety warning prompt is given in combination with the set early warning boundary. The present invention solves the problem of predictive maintenance of gas tank pistons in scenarios with incomplete data, achieves good economic benefits, and has a wide range of application value in different industrial fields.

Description

Technical Field

[0001] The invention belongs to the field of information technology and relates to a predictive maintenance method for a gas tank piston. Background Art

[0002] As a crucial component of a gas tank, the piston plays a vital role in its safe and stable operation. The difference in gas flow rates entering and exiting the gas tank causes the piston to move up and down depending on the operating status. When the intake exceeds the output, the piston rises, and vice versa. This upward and downward movement of the piston can cause uneven force on its surface, disrupting its operating equilibrium and causing it to tilt, deflect, or twist. If the piston tilts beyond a certain range, it can cause the gas tank to lose pressure. In severe cases, it can also cause the rubber membrane to tear and gas to leak, resulting in significant economic losses and safety hazards.

[0003] Ensuring the smooth operation of the piston is of great significance to the safe production of gas tanks. Currently, most existing gas tank monitoring systems have monitoring functions for pressure, capacity, thermal parameters, and tank height, but rarely mention the monitoring function of piston inclination and peripheral height. At present, the inclination of gas tanks is mostly detected from the hardware aspect (Jia Wenya, Xiong Hegen (2008). Research on the online monitoring system of the piston inclination of 30,000 cubic meters of gas tanks. Mechanical and Electrical Engineering Technology, 37(004):24-25.)(Pan Li (2012). Design of the online monitoring system of the piston inclination of Wiggins dry gas tanks. Metallurgical Energy, 031(005):60-61.), and most measures to prevent and improve piston inclination are to modify the piston structure (Cao Baoping, Liu Hongjuan, Wang Juntao, Bao Ruhan, Chai Fengfei, & Yang Yong et al. (2014). Gas tank piston. CN203641865U)(Wang Liang, & Jiao Jingchun. (2012). Detection of piston inclination of flexible film sealed gas tank. Gas and Heat, 032(003), 49-50,53.). The difficulty and workload of the modification are large, the effect cannot be guaranteed, and the feasibility is poor.

[0004] Currently, piston safety operation and maintenance are primarily performed manually through regular inspections. This lacks timely response to abnormal piston conditions or trends, and makes it difficult to analyze and determine the specific causes of any abnormalities. This not only complicates gasholder safety inspections but also poses safety risks to gasholder maintenance personnel. Designing a comprehensive and feasible real-time monitoring system for piston tilt and surrounding tilt height, in response to current industrial realities, is of great practical significance. Summary of the Invention

[0005] The problem solved by the present invention is mainly the predictive maintenance of gas tank pistons in scenarios with incomplete data. It involves soft measurement of the maximum tilt height of the gas tank piston, the height around the piston, and the offset of the piston center, as well as estimation of the piston tilt angle and early warning prompt functions. It is a predictive maintenance technology for gas tank pistons driven by both data and mechanism models. In order to solve the above problems, data from a certain industrial site are analyzed. First, the measured data is preprocessed, and the tilt height is estimated using the established piston tilt estimation model. The height around the gas tank piston is estimated using the cubic spline interpolation method, and the center offset model is used to estimate the piston center offset. Finally, a piston tilt safety warning prompt is given in combination with the set warning boundary. By using this invention, the tilt height of the gas tank piston can be accurately obtained, and an early warning can be issued for the safe operation of the piston, effectively ensuring the integrity and reliability of the data required by on-site dispatchers.

[0006] Technical solution of the present invention

[0007] A predictive maintenance method for a gas tank piston, comprising the following steps:

[0008] Step 1: Obtain and preprocess real-time operating data of industrial gas cabinets

[0009] The sensor fixed on the piston is used to measure the real-time height around the gas tank piston, and its change and initial state value are obtained. Then, each liquid column number is matched with the interpolation horizontal coordinate to obtain the interpolation node, that is, the height position of each liquid column {x1, x2, ..., x n+1} and interpolation function Where s(x) represents the height of each liquid column, c j represents the interpolation coefficient, p3(x) represents the polynomial function, x represents the height position of the liquid column to be calculated, and x j Indicates the height of the liquid column measured by the sensor;

[0010] Step 2: Calculate the inclination

[0011] The gas tank piston is processed by three-dimensional graphics flattening. Sensors A and B fixed on the piston are selected as reference points. Sensor A is located in the north direction of the piston, and sensor B is located in the east direction of the piston. The highest tilt point is set as H. The height changes measured by sensors A and B are Δh respectively. A , Δh B , the center of the piston is O, the size of ∠AOH is α, and the formula is:

[0012]

[0013] Assuming the piston radius is R, the inclination θ of the piston relative to the gas tank plane is obtained as follows:

[0014]

[0015] Where s = 2;

[0016] Step 3: Soft measurement of the liquid column height around the piston

[0017] The height of the liquid column around the piston is obtained by cubic spline interpolation. The specific calculation steps are as follows:

[0018] ①X represents a collection of points at the height of a liquid column {x1,x2,...,x n+1}, and 0=x1<x2<...<x n+1 =40, then the cubic spline interpolation basis function is defined as:

[0019]

[0020] ② The cubic spline interpolation function s(x) of the liquid column height around the piston is:

[0021]

[0022] ③ Take the boundary conditions as the second type of boundary conditions,

[0023]

[0024] Where m0, m1, m n-1 、m n are four constants, taken as the interpolation function at the interpolation points x1, x2, x n 、x n+1 The derivative at h0=x2-x1, h n-1 =x n+1 -x n , y0, y1, y n 、y n-1 Indicates the actual height of the liquid column around the piston, f0″, f n ″ indicates that the interpolation function is between x1 and x n+1 The second-order derivative value at the cubic spline interpolation function is:

[0025] λ k m k-1 +2m k +μ k m k+1 =g k (k=1,2,...,n) (6)

[0026] in,

[0027]

[0028]

[0029] From equations (6) and (7), we can get the following equations:

[0030]

[0031] Among them, g0,g n It is defined as follows:

[0032]

[0033] ③ Calculate the height of the liquid column around the piston s(x) in sequence to achieve soft measurement of the height of the liquid column around the piston;

[0034] Step 4: Calculate the maximum tilt height of the piston

[0035] According to the height of the liquid column around the piston obtained in step 3, the maximum tilt height of the piston is calculated:

[0036]

[0037] Compare the height of the piston with the height of the liquid column around it to obtain the maximum tilt height position of the piston; subtract the calculated height from the height of each liquid column, and the position between the two liquid columns with the smallest difference is the approximate position of the maximum tilt height;

[0038] Step 5: Piston Horizontal Offset

[0039] Select the sensor A fixed on the piston as the reference point and take ΔL A , ΔL B , ΔL C , ΔL D is the displacement of the four sensors; L is the initial position of the sensor; L A , L B , L C , L D are the horizontal displacement measurements of the four sensors; ΔL is the horizontal offset, and the maximum horizontal offset is calculated as follows:

[0040] ΔL A =LL A (11)

[0041] ΔL B =LL B (12)

[0042]

[0043] Consider only parallel offset, and take β as the horizontal offset angle:

[0044]

[0045] Step 6: Set the height measurement values H of the four sensorsA 、H B 、H C 、H D And the horizontal displacement measurement value L A 、L B 、L C 、L D As input data, the calculated piston inclination θ, maximum inclination height, surrounding liquid column height, maximum horizontal offset, and horizontal offset angle are used as output.

[0046] The effects and benefits of the present invention are as follows: the present invention performs analysis and calculations based on actual industrial site conditions, and through analysis and modeling of the actual operating conditions of the coke oven gas tank piston, a corresponding calculation model is obtained, which can better reflect the actual operating conditions of the piston; when performing soft measurement of the piston inclination and the height of the liquid column around the piston, various conditions of the actual system are taken into account, and the calculation results are more reliable; based on the actual operating conditions of the piston, a simple and feasible method for calculating the piston offset is provided, and the model establishment is simple to operate, easy to use, and highly accurate. Based on the actual on-site measurement results, the present invention proposes a set of soft measurement methods for piston inclination and offset, thereby providing effective support for predictive maintenance of pistons. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is an implementation flow chart of the present invention.

[0048] Figure 2(a) is a horizontal plane view of the piston.

[0049] Figure 2(b) is a schematic diagram of the piston inclination.

[0050] Figure 3(a) is a schematic diagram of the piston position sensor.

[0051] Figure 3(b) is a schematic diagram of the piston offset direction.

[0052] Figure 4 This is the result diagram of the height around the piston. DETAILED DESCRIPTION

[0053] In order to better understand the technical solution of the present invention, the present invention takes the predictive maintenance of the coke oven gas tank piston as an example and describes the embodiment of the present invention in detail with reference to the accompanying drawings. The present invention simulates and analyzes the different operating conditions of the gas tank piston, establishes a gas tank piston inclination, peripheral inclination height, and offset measurement calculation model, and completes the theoretical support for the predictive maintenance of the gas tank piston. Figure 1 The method flow shown in FIG. 1 is a flow chart showing the specific implementation steps of the present invention as follows:

[0054] Step 1: Data Preprocessing

[0055] The real-time data of industrial gas tank operation is analyzed. The actual data read on site is preprocessed to obtain the corresponding change and initial state value. Then, each liquid column label is matched with the interpolation horizontal coordinate to obtain the corresponding interpolation node and interpolation basis function.

[0056] Step 2: Calculate the slope

[0057] The gas tank piston is processed by three-dimensional graphics flattening. Sensors A and B fixed on the piston are selected as reference points. Sensor A is located in the north direction of the piston, and sensor B is located in the east direction of the piston. The highest tilt point is set as H. The height changes measured by sensors A and B are Δh respectively. A , Δh B , the center of the piston is O, the size of ∠AOH is α, and α is obtained:

[0058]

[0059] Take the piston radius as R and the piston inclination as θ. The piston inclination changes very little and can be approximately regarded as doing vertical motion. The formula for the piston inclination can be obtained as:

[0060]

[0061] Step 3: Soft measurement of the liquid column height around the piston

[0062] The piston is considered as a circular surface that tilts around a certain diameter. The height of the liquid column around the piston is obtained using the cubic spline interpolation method. The specific calculation steps are as follows:

[0063] ① Let X represent the cluster of points {x1,x2,...,x n+1}, and 0=x1<x2<...<x n+1 =40, then its cubic spline interpolation basis function can be defined as:

[0064]

[0065] ② The cubic spline interpolation function s(x) of the height around the piston can be defined as:

[0066]

[0067] Where p3(x) is a cubic polynomial, n represents the number of interpolation points, and s(x) represents the surrounding height function.

[0068] Taking the boundary conditions as the second type of boundary conditions, we can get:

[0069]

[0070] Where m0, m1, mn-1 、m n are four constants, taken as the interpolation function at the interpolation points x1, x2, x n 、x n+1 The derivative at h0=x2-x1, h n-1 =x n+1 -x n , y0, y1, y n 、y n-1 Indicates the actual height of the liquid column around the piston, f0″, f n ″ indicates that the interpolation function is between x1 and x n+1 The second-order derivative value at the cubic spline interpolation function is:

[0071] λ k m k-1 +2m k +μ k m k+1 =g k (k=1,2,...,n) (3-4)

[0072] in:

[0073]

[0074] From equations (3-4) and (3-6), we can get the following equations:

[0075]

[0076] where g0,g n It is defined as follows:

[0077]

[0078] ③ According to the above formula steps, the height s(x) of the liquid column around the piston is calculated in sequence to realize the soft measurement of the height of the liquid column around the piston.

[0079] Step 4: Calculate the maximum height of the piston tilt

[0080] When the piston tilts, since the piston plane is a circular surface, there is a maximum tilt height. According to the piston circumference height obtained in step 3, the maximum tilt height can be calculated to be approximately:

[0081]

[0082] Compare the piston with the height of the liquid column around it to obtain the maximum tilt height position of the piston; subtract the calculated height from the height of each liquid column, and the position between the two liquid columns with the smallest difference is the approximate position of the maximum tilt height.

[0083] Step 5: Piston Horizontal Offset

[0084] Select the sensor A fixed on the piston as the reference point and take ΔL A , ΔL B , ΔL C , ΔL D is the displacement of the four sensors; L is the initial position of the sensor; L A , L B , L C , L D are the horizontal displacement measurements of the four sensors; ΔL is the horizontal offset, and the maximum horizontal offset is calculated as follows:

[0085] ΔL A =LL A (5-1)

[0086] ΔL B =LL B (5-2)

[0087]

[0088] Consider only parallel offset, and take β as the horizontal offset angle:

[0089]

[0090] Step 6: Measure the height of the four sensors H A 、H B 、H C 、H D And the horizontal displacement measurement value L A 、L B 、L C 、L D As input data, the calculated piston inclination θ, maximum inclination height, surrounding liquid column height, maximum horizontal offset, and horizontal offset angle are used as output.

[0091] Step 7: Compare the calculated heights of each liquid column with the actual sensor measured heights, and calculate their MAPE and RMSE. The calculation method is as follows:

[0092]

[0093] Where n represents the total number of data, y i Indicates the actual liquid column height, It represents that the height of the liquid column is calculated by the present invention.

[0094] Table 1 shows the height around the piston calculated by the invention in a factory. The piston radius was selected as 30 meters. The method was used to determine the location and offset of the maximum tilt height, which was located between liquid columns 21 and 22 and offset from the horizontal by an angle of 0.7131. The maximum offset was 97.92 mm. The table shows that the invention can accurately calculate the height of the liquid column around the gas tank piston and accurately reflect the tilt direction of the gas tank piston.

[0095] Table 1 Calculation results of liquid column height and offset around the piston

[0096]

Claims

1. A method for predictive maintenance of a gas tank piston, characterized in that: The specific steps are as follows: Step 1: Obtain and pre-process the real-time operation data of the industrial gas cabinet; Step 2: Calculate the inclination The gas tank piston is processed by three-dimensional graphics flattening. Sensors A and B fixed on the piston are selected as reference points. Sensor A is located in the north direction of the piston, and sensor B is located in the east direction of the piston. The highest tilt point is set as H. The height changes measured by sensors A and B are Δh respectively. A , Δh B , the center of the piston is O, the size of ∠AOH is α, and the formula is: Assuming the piston radius is R, the inclination θ of the piston relative to the gas tank plane is obtained as follows: Where s = 2; Step 3: Soft measurement of the liquid column height around the piston The height of the liquid column around the piston is obtained by cubic spline interpolation; Step 4: Calculate the maximum tilt height of the piston According to the height of the liquid column around the piston obtained in step 3, the maximum tilt height of the piston is calculated: Compare the height of the piston with the height of the liquid column around it to obtain the maximum tilt height position of the piston; subtract the calculated height from the height of each liquid column, and the position between the two liquid columns with the smallest difference is the approximate position of the maximum tilt height; Step 5: Piston Horizontal Offset Select the sensor A fixed on the piston as the reference point and take ΔL A , ΔL B , ΔL C , ΔL D is the displacement of the four sensors; L is the initial position of the sensor; L A , L B , L C , L D are the horizontal displacement measurements of the four sensors; ΔL is the horizontal offset, and the maximum horizontal offset is calculated as follows: Consider only parallel offset, and take β as the horizontal offset angle: Step 6: Set the height measurement values H of the four sensors A 、H B 、H C 、H D And the horizontal displacement measurement value L A 、L B 、L C 、L D As input data, the calculated piston inclination θ, maximum inclination height, surrounding liquid column height, maximum horizontal offset, and horizontal offset angle are used as output.

2. A gas tank piston predictive maintenance method according to claim 1, characterized in that: The specific steps of step 1 are as follows: The sensor fixed on the piston is used to measure the real-time height around the gas tank piston, and its change and initial state value are obtained. Then, each liquid column number is matched with the interpolation horizontal coordinate to obtain the interpolation node, that is, the height position of each liquid column {x1, x2, ..., x n+1 } and interpolation function Where s(x) represents the height of each liquid column, c j represents the interpolation coefficient, p3(x) represents the polynomial function, x represents the height position of the liquid column to be calculated, and x j Indicates the height of the liquid column measured by the sensor.

3. The method for predictive maintenance of a gas tank piston according to claim 1, characterized in that: The specific steps of step three are as follows: ①X represents a collection of points at the height of a liquid column {x1,x2,..x n.+1 ,}, and satisfy 0=x1<x2<...<x n+1 =40, then the cubic spline interpolation basis function is defined as: ② The cubic spline interpolation function s(x) of the liquid column height around the piston is: ③ Take the boundary conditions as the second type of boundary conditions, Where m0, m1, m n-1 、m n are four constants, taken as the interpolation function at the interpolation points x1, x2, x n 、x n+1 The derivative at h0=x2-x1, h n-1 =x n+1 -x n , y0, y1, y n 、y n-1 Indicates the actual height of the liquid column around the piston, f0″, f n ″ indicates that the interpolation function is between x1 and x n+1 The second-order derivative value at the cubic spline interpolation function is: λ k m k-1 +2m k +μ k m k+1 =g k (k=1,2,...,n) (6) in, From equations (6) and (7), we can get the following equations: Among them, g0,g n It is defined as follows: ③ Calculate the height s(x) of the liquid column around the piston in sequence to achieve soft measurement of the height of the liquid column around the piston.

Images