A method for calculating the internal spring parameters of a pig with controllable pigging speed

Abstract

The present invention discloses a method for calculating the internal spring parameters of a pipe cleaner with controllable cleaning speed, including the following steps: determining the basic parameters before the force simulation of the pipe cleaner; setting the force simulation and boundary conditions of the pipe cleaner; analyzing the force state of the internal spring, calculating the key parameters of the internal spring; selecting the internal spring material, preliminarily selecting the spring size and checking it. The spring designed according to the calculation method of the internal spring parameters disclosed in the present invention can adapt to the speed fluctuation caused by multiple obstacles in the operation of the pipe cleaner, increase the adaptability of the pipe cleaner to operate under complex conditions, and effectively control the operating speed of the pipe cleaner, thereby providing a strong guarantee for the pipe cleaning operation of the oil and gas production system to achieve the purpose of high efficiency, safety and stability.

Description

Technical Field

[0001] The invention relates to the technical field of spring design, and in particular to a method for calculating spring parameters inside a pipe cleaning device with controllable pipe cleaning speed. Background Art

[0002] A pipe cleaner, also known as a pipeline cleaner, is a tool that moves in the lumen of a pipe with the help of its own power or driven by oil or airflow, and is used to clean the pipe wall and monitor the internal condition of the pipeline. Pipe cleaning is an important part of the production of long-distance pipelines such as oil and gas, and is also the most basic and effective measure to ensure the effect of pipeline transportation. The running speed of the pipe cleaner in the pipeline is referred to as the "pipe cleaning speed". Pipe cleaning speed control is of great significance for optimizing the pipe cleaning operation and enhancing the pipe cleaning effect. The pipe cleaning speed determines the pipe cleaning effect of the pipe cleaner. When the pipe cleaning speed of the pipe cleaner is maintained constant, the pipe cleaning effect is the best. Among them, the recommended operating speed of the pipe cleaner for general liquid pipelines is 1 to 5m / s, while the operating speed of the pipe cleaner for gas pipelines can be maintained at 2 to 7m / s to achieve efficient pipe cleaning. The research results of the operating speed control technology of the pipe cleaner show that it can be started from the perspective of changing the driving force, that is, when the operation of the pipe cleaner encounters obstacles and the speed gradually decreases, in order to prevent the operating speed of the pipe cleaner from being too low, the driving force at the front and rear ends of the pipe cleaner can be increased to increase the speed to the preset operating range. When the operating speed of the pipe cleaner is too high, its operating speed can be reduced by reducing the driving force of the pipe cleaner. The bypass rate of the pipe cleaner is the main factor affecting its driving force. The method of changing the driving force is generally to open a bypass jet hole inside the main shaft of the pipe cleaner, bypass part of the gas, thereby controlling the pressure difference before and after the pipe cleaner, and then changing the driving force and operating speed of the pipe cleaner. Therefore, controlling the opening size of the bypass hole to change the driving force of the pipe cleaner is an effective means to control the operating speed of the pipe cleaner.

[0003] Relevant research on changing the bypass rate to control the pigging speed shows that domestic and foreign scholars have opened a bypass hole inside the pig and added a bypass control valve and spring at the rear of the bypass hole. The real-time expansion and contraction of the spring changes the forward and backward movement of the valve, thereby realizing the opening control of the bypass hole and thus changing the running speed of the pig. The Chinese utility model patent with application number CN201320602776.1 discloses "An Anti-blocking Jet Pipe Pig". The pig disclosed in the patent can achieve a certain bypass during normal operation. When the pig encounters an obstacle, the valve is closed by the spring, thereby achieving pressure holding and restarting, thereby achieving control of the running speed of the pig. However, the patent only conceptually proposes the role of the spring, and does not provide a method for selecting or calculating the specific parameters of the spring inside the pipe cleaner, resulting in a lack of basis for the formulation of the design or manufacturing standards for the internal spring of the pipe cleaner and unclear implementation standards, which makes it inconvenient for designers or engineers to design or select the internal spring when controlling the running speed of the pipe cleaner, thereby reducing the efficiency of the running speed control of the pipe cleaner and making the pipe cleaning operation of the oil and gas production system lack of effective guarantees for efficiency, safety and stability. Summary of the invention

[0004] The object of the present invention is to provide a method for calculating the internal spring parameters of a pig with controllable pigging speed, so as to solve the problem that designers or engineers are inconvenienced in the design or selection process of the internal spring when controlling the running speed of the pig.

[0005] The present invention provides a method for calculating spring parameters inside a pipe cleaning device with controllable pipe cleaning speed, the method comprising the following steps:

[0006] Step S1: determining basic parameters of the pig before force simulation;

[0007] Step S2: pig force simulation and boundary condition setting;

[0008] Step S3: analyzing the stress state of the internal spring and calculating the key parameters of the internal spring;

[0009] Step S4: Select the internal spring material, preliminarily select the spring size and check it;

[0010] Step S5: Determine the working number of coils and actual stiffness of the internal spring;

[0011] Step S6: adjusting the internal spring pre-compression amount and the spring working stroke;

[0012] Step S7: Calculate the structural parameters of the internal spring: spring pitch p, helix angle α, total number of turns n1, free height H0 and installation height H1.

[0013] Wherein, the step S2 comprises the following steps:

[0014] The analytical equation for the running speed of the pig in the pipeline is:

[0015]

[0016] Where m is the mass of the pig, in kg; V pig is the running speed of the pig in the pipeline, in m / s; t is the running time of the pig in the pipeline, in s; A pipe is the cross-sectional area of ​​the pipe, in m 2 ; A h is the cross-sectional area of ​​the bypass hole, in m 2 ; P1 and P2 are the pressures behind and in front of the pig in the pipeline, respectively, in Pa; F hd F is the shear drag force of gas on the bypass hole wall, in N; fric It represents the friction force acting on the pig, in N; α is the inclination angle between the pig's running direction and the horizontal line;

[0017] Set the initial values ​​and boundary conditions.

[0018] Wherein, the step S3 comprises the following steps:

[0019] Step S31: Calculate the force F1 of the bypass control valve in a stable operating state and the force F2 of the bypass control valve in a dangerous operating state, which are calculated as follows:

[0020] F1=KX (1)

[0021] Where X is the pre-compression of the internal spring; K is the stiffness coefficient of the internal spring;

[0022] F2=K(X+L) (2)

[0023] Among them, X+L is the full compression of the internal spring, and L is the working stroke of the spring;

[0024] Step S32: Preliminarily obtain the pre-compression amount X and stiffness coefficient K of the internal spring

[0025] Assuming that L in the full compression amount X+L is the working stroke of the spring, the stiffness coefficient of the internal spring is recorded as K, the force F1 of the bypass control valve in the stable operating state and the force value F2 of the bypass control valve in the dangerous working state are respectively equal to the elastic force of the internal spring in the pre-compression amount X and the full compression amount X+L state;

[0026] The force balance analysis of the internal spring is carried out, and the pre-compression amount X and stiffness coefficient K of the internal spring are preliminarily obtained through equations (1) and (2).

[0027] Wherein, the step S4 comprises the following steps:

[0028] Step S41: Select the internal spring material and determine the shear modulus G and allowable shear stress [τ] of the internal spring;

[0029] Step S42: Preliminarily determine the middle diameter D2 and the winding ratio C of the internal spring according to the valve stem diameter of the bypass control valve, where C=5-8, and calculate the wire diameter d of the internal spring and the curvature coefficient N of the internal spring. The calculation expression of the wire diameter d of the internal spring is as follows:

[0030]

[0031] The calculation expression of the curvature coefficient N of the internal spring is as follows:

[0032]

[0033] Step S43: Check the wire diameter d value of the internal spring

[0034] The verification formula of the wire diameter d of the internal spring is:

[0035]

[0036] Step S44: If the wire diameter d value of the internal spring is not properly checked, it is necessary to reselect the center diameter D2 and the winding ratio C of the internal spring, and repeat steps S41 to S42 until the wire diameter d value of the internal spring is properly checked.

[0037] Wherein, the step S5 comprises the following steps:

[0038] The calculation formula for the number of working turns n of the internal spring is:

[0039]

[0040] The working number of the internal spring is rounded off, and then the actual stiffness coefficient K of the internal spring is calculated using the rounded n value. The expression is:

[0041]

[0042] Wherein, the step S6 comprises the following steps:

[0043] Substitute the actual stiffness coefficient K into equations (1) and (2) to redetermine the pre-compression X and working stroke L of the internal spring.

[0044] Wherein, the step S7 comprises the following steps:

[0045] The spring pitch p is calculated as:

[0046]

[0047] where δ min The minimum gap between the internal spring coils should be kept under maximum deformation, and δ min =0.1d;

[0048] The calculation formula of the helix angle α is:

[0049]

[0050] Among them, the helix angle α should be between 5 and 9°;

[0051] The calculation expression for the total number of coils n1 of the inner coil spring is:

[0052] n1=n+2 (10)

[0053] The free height H0 of the inner spring is calculated as:

[0054] H0=np+1.5d (11)

[0055] The calculation expression of the installation height H1 of the internal spring is:

[0056] H1=H0-X (12)

[0057] The beneficial effects of the present invention are:

[0058] The invention discloses a method for calculating the internal spring parameters of a pipe cleaner with controllable cleaning speed. According to the characteristics of the internal structure of the pipe cleaner with controllable cleaning speed, when the pipe cleaner overcomes obstacles and the speed increases, the pressure on the internal spring decreases, so the internal spring drives the valve to move backward, and the bypass rate of the pipe cleaner is increased, so that the pipe cleaner maintains a certain bypass forward movement, and realizes efficient pipe cleaning, so that the spring designed by the calculation method can adapt to the speed fluctuation caused by multiple obstacles in the operation of the pipe cleaner, and the adaptability of the pipe cleaner to operate under complex conditions is increased, so that the operating speed of the pipe cleaner is effectively controlled, thereby providing a strong guarantee for the pipe cleaning operation of the oil and gas production system to achieve the purpose of high efficiency, safety and stability, and further effectively ensuring the safe production of oil and gas pipelines. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 A schematic diagram of the internal structure of a cleaning pipe with a controllable cleaning speed provided in Example 1 of the present invention;

[0060] Figure 2 A schematic diagram of the spring contraction process structure provided in Example 2 of the present invention;

[0061] Figure 2 (a) is a schematic diagram of the original state of the spring without external force;

[0062] Figure 2 (b) is a schematic diagram of spring compression when subjected to external force F1;

[0063] Figure 2 (c) is a schematic diagram of spring compression when subjected to external force F2.

[0064] Explanation of the reference numerals: 1—jet nozzle; 2—support frame; 3—internal spring; 4—fixing nut; 5—bypass control valve. DETAILED DESCRIPTION

[0065] Example 1

[0066] Embodiment 1 provides a cleaning pipe with controllable cleaning speed, and its structure is described in detail below.

[0067] Reference Figure 1 The cleaning pipe with controllable cleaning speed includes a cleaning pipe body with a hollow structure, one end of the cleaning pipe body is provided with a conical hole, a jet nozzle 1 is provided on the conical hole, and two support frames 2, an internal spring 3, a fixing nut 4 and a bypass control valve 5 are provided inside the cleaning pipe body.

[0068] Among them, two support frames 2 are fixed inside the pig, and the bypass control valve 5 is a valve with a "T"-shaped cross section, including a longitudinal valve stem and a transverse valve head, and the end of the longitudinal valve stem is perpendicular to the transverse valve head and fixedly connected to the middle of the transverse valve head.

[0069] The bypass control valve 5 is connected to the pig body through two support frames 2, and the longitudinal valve stem of the bypass control valve 5 can move along the length direction of the pig body, and the transverse valve head of the bypass control valve 5 can slowly block the tapered hole as the longitudinal valve stem moves.

[0070] A fixing nut 4 is sleeved on the tail end of the longitudinal valve stem of the bypass control valve 5, and an internal spring 3 is sleeved on the longitudinal valve stem of the bypass control valve 5 between the support frame 2 and the fixing nut 4, and both ends of the internal spring 3 respectively contact the support frame 2 and the fixing nut 4 away from the lateral valve head of the bypass control valve 5.

[0071] The internal spring 3 is a cylindrical helical compression spring, and the internal spring 3 has a certain pre-compression amount on the longitudinal valve stem of the bypass control valve 5 between the support frame 2 and the fixing nut 4. When the internal spring 3 is fully compressed, the lateral valve head of the bypass control valve 5 contacts the jet nozzle 1 to achieve sealing. The bypass control valve 5 and the internal spring 3 move in coordination, and the two have the same displacement law.

[0072] A cleaning pipe with controllable cleaning speed is a prior art. For more information about its internal structure, please refer to the Chinese utility model patent application number CN201320602776.1 entitled "Anti-blocking jet pipe cleaning device".

[0073] Example 2

[0074] Embodiment 2 provides a method for calculating the parameters of the internal spring of a pipe cleaning device with controllable pipe cleaning speed, which is used to design or manufacture the internal spring of the pipe cleaning device with controllable pipe cleaning speed in Embodiment 1. The calculation method comprises the following steps:

[0075] Step S1: Determine the basic parameters before pig force simulation

[0076] Set the lower limit value V of the speed range of the pig in the stable operation state d =2m / s, the warning speed value V under dangerous working conditions after the pig encounters obstruction l =1m / s, measure the production gas velocity V of the pig under stable operation g and pipeline pressure P;

[0077] Set the lower limit and warning speed value of the pig running speed in the pipeline;

[0078] Step S2: pig force simulation and boundary condition setting;

[0079] The analytical equation for the running speed of the pig in the pipeline is:

[0080]

[0081] Where m is the mass of the pig, in kg; V pig is the running speed of the pig in the pipeline, in m / s; t is the running time of the pig in the pipeline, in s; A pipe is the cross-sectional area of ​​the pipe, in m 2 ; A h is the cross-sectional area of ​​the bypass hole, in m 2 ; P1 and P2 are the pressures behind and in front of the pig in the pipeline, respectively, in Pa; F hd F is the shear drag force of gas on the bypass hole wall, in N; fric It represents the friction force acting on the pig, and its unit is N; α is the inclination angle between the running direction of the pig and the horizontal line.

[0082] The geometric model of the pig moving in the pipeline is established by using Fluent / 6SigmaDC (EPC) software in the computational fluid dynamics (CFD) simulation software, and the model is imported into the solver. The boundary conditions are added, and the force simulation calculation of the bypass control valve 5 under stable operation state and dangerous working condition is performed respectively. The force value of the bypass control valve 5 under stable operation state is F1, and the force value of the bypass control valve 5 under dangerous working condition is F2.

[0083] Boundary conditions: Use Fluent software for steady-state calculation of initial conditions;

[0084] Set boundary conditions: Set the boundary condition of the stable operation state to the inlet gas velocity V g –V d , outlet pressure P, pipeline running speed is –V d The boundary condition of the dangerous working state is the inlet gas velocity V g –V l and outlet pressure P, the pipeline running speed is –V l ;

[0085] Set the termination condition: perform iterative calculations and stop the calculations when they converge. In Fluent, when the calculation residual is less than 10 -6 , and the fluid inlet and outlet mass is conserved, the calculation can be considered to have reached convergence. The Fluent calculation residual is the sum of the fluxes of each surface in the grid. When the calculation converges, theoretically there is no source term in the grid unit that causes each surface to have inflow flux.

[0086] Step S3: analyzing the stress state of the internal spring and calculating the key parameters of the internal spring;

[0087] Step S31: Calculate the force F1 of the bypass control valve 5 in a stable operating state and the force F2 of the bypass control valve 5 in a dangerous operating state.

[0088] The force F1 of the bypass control valve 5 under the stable operation state and the force F2 of the bypass control valve 5 under the dangerous working state are simulated and calculated by CFD software. The calculation is as follows:

[0089] F1=KX (1)

[0090] Wherein, X is the pre-compression amount of the internal spring 3; K is the stiffness coefficient of the internal spring 3;

[0091] F2=K(X+L) (2)

[0092] Among them, X+L is the full compression of the internal spring 3, and L is the working stroke of the spring;

[0093] Step S32: Preliminarily obtain the pre-compression amount X and stiffness coefficient K of the internal spring

[0094] Suppose that when L in the total compression amount X+L is the working stroke of the spring, the stiffness coefficient of the internal spring 3 is recorded as K,

[0095] The force F1 of the bypass control valve 5 in the stable operating state and the force F2 of the bypass control valve (5) in the dangerous operating state are respectively equal to the elastic force of the internal spring 3 in the pre-compression amount X and the full compression amount X+L state.

[0096] The CFD software simulates the force balance analysis of the internal spring 3, and the pre-compression amount X and stiffness coefficient K of the internal spring are preliminarily obtained through equations (1) and (2).

[0097] Step S4: Select the internal spring material, preliminarily select the spring size and check it;

[0098] Step S41: Select the internal spring material and determine the shear modulus G and allowable shear stress [τ] of the internal spring 3;

[0099] Step S42: Preliminarily determine the middle diameter D2 and the winding ratio C of the internal spring according to the valve stem diameter of the bypass control valve 5, where C=5-8, and calculate the wire diameter d of the internal spring and the curvature coefficient N of the internal spring. The calculation expression of the wire diameter d of the internal spring is as follows:

[0100]

[0101] The calculation expression of the curvature coefficient N of the internal spring is as follows:

[0102]

[0103] Step S43: Check the wire diameter d value of the internal spring

[0104] The wire diameter d value of the internal spring is selected according to the national standard "GB / T 1358-2009 Cylindrical Helical Spring Dimension Series" and checked according to the following formula:

[0105]

[0106] Step S44: If the wire diameter d value of the internal spring is not properly checked, it is necessary to reselect the center diameter D2 and the winding ratio C of the internal spring, and repeat steps S41 to S42 until the wire diameter d value of the internal spring is properly checked.

[0107] Step S5: Determine the working number of coils and actual stiffness of the internal spring;

[0108] The calculation formula for the number of working turns n of the internal spring 3 is:

[0109]

[0110] The working number n of the internal spring 3 is rounded, and then the actual stiffness coefficient K of the internal spring 3 is calculated using the rounded n value, and the expression is:

[0111]

[0112] Step S6: adjusting the internal spring pre-compression amount and the spring working stroke;

[0113] Substitute the actual stiffness coefficient K into equations (1) and (2) to redetermine the pre-compression X and working stroke L of the internal spring.

[0114] Step S7: Calculate the spring pitch, helical angle, total number of turns, free height, installation height and other structural parameters of the spring inside the spring;

[0115] refer to Figure 2 Other structural parameters of the internal spring include spring pitch p, helix angle α, total number of turns n1, free height H0, installation height H1, etc.

[0116] Among them, the calculation formula of spring pitch p is:

[0117]

[0118] where δ min The minimum gap between the three coils of the inner spring under maximum deformation, where δ≥0.1d, take δ min =0.1d;

[0119] The calculation formula of the helix angle α is:

[0120]

[0121] Among them, the helix angle α should be between 5 and 9°;

[0122] Take the support circle as 2 circles, and the calculation expression of the total number of circles n1 of the inner spring is:

[0123] n1=n+2 (10)

[0124] The two ends are tightly ground and the calculation expression of the internal spring free height H0 is:

[0125] H0=np+1.5d (11)

[0126] The calculation expression of the installation height H1 of the internal spring is:

[0127] H1=H0-X (12)

[0128] After completing the design of the key parameters of the spring through the above steps, the spring can be used to achieve real-time control of the bypass rate of the pig according to the operating state of the pig, thereby changing the driving force of the pig and completing the control of the pig speed.

[0129] The internal spring is adaptive and can adapt to the obstacles to the pig caused by the complex and changeable conditions of the pipeline terrain. When the speed of the pig is lower than the warning speed, the valve will close quickly, thereby quickly establishing a pressure difference before and after the pig, allowing the pig to overcome the obstacles and move forward. At the same time, the rapid action of the spring also avoids the pig from holding pressure for too long, causing excessive pressure accumulation behind the pig and excessive acceleration of the pig.

[0130] Although the present invention has been described in detail above by general description and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made on the basis of the present invention. Therefore, these modifications or improvements made on the basis of not departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A method for calculating the internal spring parameters of a pipe cleaning device with controllable cleaning speed, characterized in that: The calculation method comprises the following steps: Step S1: determining basic parameters of the pig before force simulation; Step S2: Pig force simulation and boundary condition setting, including the following steps: Establish the analytical equation expression of the running speed of the pig in the pipeline: Where m is the mass of the pig, in kg; V pig is the running speed of the pig in the pipeline, in m / s; t is the running time of the pig in the pipeline, in s; A pipe is the cross-sectional area of ​​the pipe, in m 2 ; A h is the cross-sectional area of ​​the bypass hole, in m 2 ; P1 and P2 are the pressures behind and in front of the pig in the pipeline, respectively, in Pa; F hd F is the shear drag force of gas on the bypass hole wall, in N; fric It represents the friction force acting on the pig, in N; α is the inclination angle between the pig's running direction and the horizontal line; Set initial values ​​and boundary conditions; Step S3: analyzing the stress state of the internal spring and calculating the key parameters of the internal spring; Step S4: Select the internal spring material, preliminarily select the spring size and check it, including the following steps: Step S41: Select the internal spring material and determine the shear modulus G and allowable shear stress [τ] of the internal spring; Step S42: Preliminarily determine the middle diameter D2 and the winding ratio C of the internal spring according to the valve stem diameter of the bypass control valve, where C=5-8, and calculate the wire diameter d of the internal spring and the curvature coefficient N of the internal spring. The calculation expression of the wire diameter d of the internal spring is as follows: The calculation expression of the curvature coefficient N of the internal spring is as follows: Step S43: Check the wire diameter d value of the internal spring The verification formula of the wire diameter d of the internal spring is: Step S44: If the wire diameter d value of the internal spring is not properly checked, it is necessary to reselect the middle diameter D2 and the winding ratio C of the internal spring, and repeat steps S41 to S42 until the wire diameter d value of the internal spring is properly checked; Step S5: Determine the working number of coils and actual stiffness of the internal spring; Step S6: adjusting the internal spring pre-compression amount and the spring working stroke; Step S7: Calculate the structural parameters of the internal spring: spring pitch p, helix angle α, total number of turns n1, free height H0 and installation height H1, including the following steps: The spring pitch p is calculated as: where δ min The minimum gap between the internal spring coils should be kept under maximum deformation, and δ min =0.1d; The calculation formula of the helix angle α is: Among them, the helix angle α should be between 5 and 9°; The calculation expression for the total number of coils n1 of the inner coil spring is: n1=n+2 (10) The free height H0 of the inner spring is calculated as: H0=np+1.5d (11) The calculation expression of the installation height H1 of the internal spring is: H1=H0-X (12).

2. The method for calculating the spring parameters inside the pig with controllable pigging speed according to claim 1, characterized in that: The step S3 comprises the following steps: Step S31: Calculate the force F1 of the bypass control valve in a stable operating state and the force F2 of the bypass control valve in a dangerous operating state, which are calculated as follows: F1=KX (1) Where X is the pre-compression of the internal spring; K is the stiffness coefficient of the internal spring; F2=K(X+L) (2) Among them, X+L is the full compression of the internal spring, and L is the working stroke of the spring; Step S32: Preliminarily obtain the pre-compression amount X and stiffness coefficient K of the internal spring Assuming that L in the full compression amount X+L is the working stroke of the spring, the stiffness coefficient of the internal spring is recorded as K, the force F1 of the bypass control valve in the stable operating state and the force value F2 of the bypass control valve in the dangerous working state are respectively equal to the elastic force of the internal spring in the pre-compression amount X and the full compression amount X+L state; The force balance analysis of the internal spring is carried out, and the pre-compression amount X and stiffness coefficient K of the internal spring are preliminarily obtained through equations (1) and (2).

3. The method for calculating the spring parameters inside the pig with controllable pigging speed according to claim 1, characterized in that: The step S5 comprises the following steps: The calculation formula for the number of working turns n of the internal spring is: The working number of the internal spring is rounded off, and then the actual stiffness coefficient K of the internal spring is calculated using the rounded n value. The expression is:

4. The method for calculating the spring parameters inside the pig with controllable pigging speed according to claim 2, characterized in that: The step S6 comprises the following steps: Substitute the actual stiffness coefficient K into equations (1) and (2) to redetermine the pre-compression X and working stroke L of the internal spring.

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