Real-time Monitoring and Leak Plugging Device and Method for Pipeline Flange Tightness

Abstract

The present invention discloses a pipeline flange tightness real-time monitoring and plugging device, comprising a connecting flange, a bolt, a nut, a strain gauge and a judgment and detection module, wherein the connecting flanges are respectively arranged on the pipeline, a gap is left between the connecting flanges on the opposite pipelines, the bolts and nuts are used to fix the connecting flanges, the strain gauge is attached to the measuring part of the bolt, the measuring part is the part of the bolt located in the gap, and the judgment and detection module receives the measurement data of the strain gauge and judges whether there is a leak according to a set threshold. The present invention also discloses a pipeline flange tightness real-time monitoring and plugging method, wherein a disc spring gasket assembly with an axially pre-compressed nickel-titanium memory alloy sheet is arranged between the bolt, nut and connecting flange, and when a leak is judged, the axially pre-compressed nickel-titanium memory alloy sheet is heated by a heating assembly to supplement the pre-tightening force. The present invention is applicable to both gas and liquid delivery pipelines, and can provide leak warning and timely plugging emergency operation.

Description

Technical Field

[0001] The present invention relates to a pipeline flange detection and leak plugging device and method, in particular to a device and method for real-time monitoring of the tightness of pipeline flanges and leak plugging. Background Art

[0002] In industrial application scenarios, pipelines are the main devices for gas and liquid transportation, and the reliability of flange connection structures is the key to ensuring the long-term safe operation of pipelines. Currently, the most common method in the industry for the safe operation of pipeline flanges is manual monitoring at regular intervals. Such a method consumes a large amount of manpower and material resources, and cannot perform real-time monitoring, resulting in incomplete control of the pipeline conditions. Especially in some places with high temperature, high pressure, high altitude, etc., where manual detection is not suitable, once leakage occurs, it will not only cause economic losses, but also lead to safety accidents.

[0003] Chinese Patent with publication number CN104913204A discloses a pipeline gas leakage detection device and its detection method. This solution determines whether there is leakage by setting a leakage gas collection device between flange surfaces and measuring the pressure change of the leakage gas in the leakage gas collection device by a gas pressure sensor; Chinese Patent with publication number CN210136038U discloses an on-line detection system for pipeline flange leakage. This solution determines whether leakage occurs by setting a detection housing around the flange group and a liquid leakage sensor below the flange group in the detection housing to collect the liquid leakage of the pipeline flange. The above-mentioned prior arts all have the following problems: 1. They are only applicable to the leakage detection of liquid or gas pipelines alone; 2. They can only be detected when the pipeline actually leaks and the leakage reaches a certain degree; 3. After detecting the leakage, it is necessary to rely on manual maintenance, and it is difficult to immediately implement leak plugging measures to prevent continuous leakage from causing other problems. Summary of the Invention

[0004] Aiming at the defects of the above-mentioned prior arts, the present invention provides a device for real-time monitoring of the tightness of pipeline flanges and leak plugging, which solves the problem that existing detection devices can only detect leakage of liquids or gases, and at the same time solves the problem of difficult early warning of the occurrence of leakage. Another task of the present invention is to provide a method for real-time monitoring of the tightness of pipeline flanges and leak plugging to achieve timely leak plugging after leakage of pipeline flanges.

[0005] The technical solution of the present invention is as follows: A real-time monitoring and leak plugging device for the tightness of pipeline flanges, including connecting flanges, bolts, nuts, strain gauges and a judgment and detection module. The connecting flanges are respectively arranged on the pipeline, and there is a gap between the connecting flanges on the opposite pipelines. The bolts and nuts are cooperatively used for fixing between the connecting flanges. The strain gauges are attached to the measuring parts of the bolts, and the measuring parts are the parts of the bolts located in the gap. The judgment and detection module receives the measurement data of the strain gauges and judges whether there is a leak according to the set threshold value.

[0006] The present invention monitors the stress of the bolts through strain gauges to determine the deformation of the bolts, so as to determine whether there is a leak caused by the change of the bolt pre-tightening force.

[0007] Further, in order to avoid the problem that bolts with changed pre-tightening force are not attached with strain gauges and the leak cannot be detected in time, a plurality of bolts are provided and are equally distributed in the circumferential direction of the connecting flange. The number of strain gauges is not less than two, and the central angle corresponding to any two adjacent strain gauges does not exceed 180 degrees.

[0008] Further, in order to be able to perform emergency leak plugging when a leak is detected or there is a risk of leakage, so as to buy time for manual maintenance and prevent the leakage from further expanding and causing accidents, a disc spring gasket assembly is provided between the bolt and the connecting flange or between the nut and the connecting flange. The disc spring gasket assembly includes an upper fixing piece, an upper disc spring, a spacer piece, a lower disc spring and a lower fixing piece which are stacked in sequence. Axially pre-compressed nickel-titanium memory alloy sheets are clamped on the disc inner side walls of the upper disc spring and the lower disc spring. The axially pre-compressed nickel-titanium memory alloy sheets are disc-shaped and fit on the disc inner side walls of the upper disc spring and the lower disc spring. A heating component is provided on the axially pre-compressed nickel-titanium memory alloy sheets. When the heating component heats the axially pre-compressed nickel-titanium memory alloy sheets, the axially pre-compressed nickel-titanium memory alloy sheets drive the upper disc spring and the lower disc spring to axially extend and deform.

[0009] Further, a plurality of pairs of hooks are provided on the disc inner side walls of the upper disc spring and the lower disc spring. Each pair of hooks includes an upper hook and a lower hook with opposite openings. The axially pre-compressed nickel-titanium memory alloy sheets are clamped between the upper hook and the lower hook, and a plurality of notch parts are provided on the axially pre-compressed nickel-titanium memory alloy sheets. The assembly of the disc spring gasket assembly is facilitated by the way of rotational engagement.

[0010] Further, the disc openings of the upper disc spring and the lower disc spring are arranged opposite to each other. The upper fixing piece is fixedly connected to the upper disc spring, and the lower fixing piece is fixedly connected to the lower disc spring.

[0011] Further, an axial guide sleeve is provided at the edge of the separator, and axial guide posts are provided at the edges of the upper fixing piece and the lower fixing piece. The guide posts penetrate through the guide sleeve.

[0012] A method for real-time monitoring and leakage plugging of pipeline flange tightness is carried out based on the above-mentioned device for real-time monitoring and leakage plugging of pipeline flange tightness. The judgment and detection module receives the measurement data of the strain gauge and compares it with a set threshold. When the measurement data exceeds the set threshold, it controls the heating component to heat the axially pre-compressed nickel-titanium memory alloy sheet.

[0013] Further, receiving the measurement data of the strain gauge and comparing it with the set threshold is to convert the measurement data of the strain gauge into tightness evaluation data and compare it with the set threshold of the tightness evaluation data. The tightness evaluation data is calculated by the following formula

[0014]

[0015] In the formula: A L , n l , m l , u l are regression coefficients; η x is the dynamic viscosity of the substance transported in the pipeline; S G0 is the minimum pre-tightening specific pressure of the gasket between the connecting flanges; D0 is the maximum outer diameter of the gasket between the connecting flanges; L L is the leakage rate; p is the medium pressure; S G is the pre-tightening force variable; D x is the outer diameter variable of the gasket between the connecting flanges.

[0016] The advantages of the technical solution provided by the present invention are as follows:

[0017] By using a strain gauge to measure the deformation of the bolt and indirectly detecting the leakage, it can be unrestricted by the physical state of the substance in the pipeline and is applicable to both gas and liquid transportation pipelines, with a simple structure; by heating the axially pre-compressed nickel-titanium memory alloy sheet in the disc spring gasket assembly, when a pipeline leakage or a leakage risk is detected, emergency treatment can be directly carried out to prevent the leakage from further expanding and causing accidents, and time is gained for personnel to arrive at the scene for repair. The disc spring gasket assembly with an axially pre-compressed nickel-titanium memory alloy sheet has better stability than the traditional disc gasket. When the disc spring cannot provide sufficient pre-tightening force, the shape memory effect of the nickel-titanium alloy provides additional pre-tightening force to provide additional compensation for the deformation of the bolt under the operating conditions and reduce the deformation amount of the bolt under the operating conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic structural diagram of a device for real-time monitoring and leakage plugging of pipeline flange tightness.

[0019] Figure 2 It is a three-dimensional structural schematic diagram of a conical spring gasket assembly.

[0020] Figure 3 It is a side-view structural schematic diagram of a conical spring gasket assembly.

[0021] Figure 4 It is a sectional structural schematic diagram of an upper conical spring, a lower conical spring, and an axially pre-compressed nickel-titanium shape memory alloy sheet.

[0022] Figure 5 It is a structural schematic diagram of the engagement between the upper conical spring and the axially pre-compressed nickel-titanium shape memory alloy sheet. Specific embodiments

[0023] The present invention will be further described below in conjunction with embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. After reading this description, those skilled in the art will fall within the scope defined by the appended claims of this application for various equivalent modifications of this description.

[0024] Please refer to Figure 1 As shown, the real-time monitoring and leak plugging device for the tightness of the pipeline flange in this embodiment includes a connecting flange 1, bolts 2, nuts 3, strain gauges 4, a conical spring gasket assembly 8, and a judgment and detection module. The judgment and detection module includes a signal transmission device 5, a signal receiving station, and a host computer, and the signal receiving station and the host computer are not shown in the figure. Among them, the strain gauge 4 is electrically connected to the signal transmission device 5. The signal measured by the strain gauge 4 is sent to the signal transmission device 5, and the signal transmission device 5 transmits it to the signal receiving station by using 4G technology through an antenna and then obtained by the host computer, and then processed by the host computer to judge whether there is a leak.

[0025] The strain gauge 4 is installed as follows. A connecting flange 1 is set at a certain distance from the butt joint surface 7 of the two pipes 6. A number of connecting through holes are opened on the connecting flange 1 in an axially equally divided distribution manner. In this embodiment, eight connecting through holes are provided. After the butt joint surfaces 7 of the pipes 6 are aligned, bolts 2 are inserted into the connecting through holes and fastened with nuts 3. Since the connecting flange 1 is at a certain distance from the butt joint surface 7, there is a gap between the two connecting flanges 1 after the fastening connection is completed. The circumferential cylindrical surface of the bolt 2 in the gap between the two connecting flanges 1 is wiped clean with alcohol, and a strain gauge 4 is pasted. The strain gauge 4 is used to measure the deformation of the bolt 2. Since the loosening conditions of the bolts 2 are different, in order to prevent the bolt 2 with the strain gauge 4 from deforming late and resulting in untimely detection, strain gauges are pasted on multiple bolts 2, and the central angle of the cross-section of the pipe 6 corresponding to the bolts 2 where any two adjacent strain gauges 4 are located does not exceed 180 degrees. That is to say, if at least two strain gauges 4 are set, they are set on the bolts 2 at both ends of the diameter of the cross-section of the pipe 6. For example, if the connecting flange 1 is connected by five bolts 2, at least three strain gauges 4 should be set in sequential numbering and there should be one number interval in the middle. The signal transmission device 5 is fixed on the pipe 6 near the connecting flange 1 through an annular hoop, and the data lines of the strain gauges 4 are tied together to form a data transmission line group and connected to the signal transmission device 5.

[0026] The disc spring gasket assembly 8 can be set between the nut 3 and the connecting flange 1, or can be set between the head of the bolt 2 and the connecting flange 1. In this embodiment, it is set between the head of the bolt 2 and the connecting flange 1. Please refer to Figure 2 and Figure 3As shown, the disc spring gasket assembly 8 includes an upper fixing piece 801, an upper disc spring 802, a separator 803, a lower disc spring 804, and a lower fixing piece 805 that are stacked axially in sequence. Four axial guide sleeves 811 are provided at the edge of the separator 803. Correspondingly, four axial guide posts 810 are respectively provided at the edges of the upper fixing piece 801 and the lower fixing piece 805. The guide posts 810 penetrate through the guide sleeves 811 to align the upper fixing piece 801, the separator 803, and the lower fixing piece 805. The upper disc spring 802 is disposed between the upper fixing piece 801 and the separator 803. The upper disc spring 802 is fixedly connected to the upper fixing piece 801, and the disc opening of the upper disc spring 802 faces the separator 803. Correspondingly, the lower disc spring 804 is disposed between the lower fixing piece 805 and the separator 803. The lower disc spring 804 is fixedly connected to the lower fixing piece 805, and the disc opening of the lower disc spring 804 faces the separator 803. Thus, a vertically symmetric structure is formed, and the force on the gasket assembly is more uniform. It should be noted that the setting of the opening directions of the above upper disc spring 802 and lower disc spring 804 is only a preferred embodiment, and the upper disc spring 802 and the lower disc spring 804 can be set in the same direction or with the disc openings facing away from each other.

[0027] Axial pre-compressed nickel-titanium memory alloy sheets 808 are respectively provided on the inner disc walls of the upper disc spring 802 and the lower disc spring 804. Taking the upper disc spring 802 as an example, as Figure 4 、 Figure 5As shown in the figure, on the inner disc-shaped wall of the upper disc spring 802, there are multiple pairs of hooks. Each pair of hooks includes an upper hook 806 and a lower hook 807 with opposite openings, and there is enough space between the upper hook 806 and the lower hook 807. The grooves of the upper hook 806 and the lower hook 807 are equivalent to the thickness of the axially pre-compressed nickel-titanium shape memory alloy sheet 808. The axially pre-compressed nickel-titanium shape memory alloy sheet 808 is disc-shaped and annular to adapt to the shape of the upper disc spring 802, so that it can fit on the inner disc-shaped wall of the upper disc spring 802. The ring width of the axially pre-compressed nickel-titanium shape memory alloy sheet 808 is equivalent to the bottom spacing of the grooves of the upper hook 806 and the lower hook 807. On the axially pre-compressed nickel-titanium shape memory alloy sheet 808, there are notch parts 808a with the same number as the number of pairs of hooks. The ring width of the axially pre-compressed nickel-titanium shape memory alloy sheet 808 at the notch parts 808a is equivalent to the space between the upper hook 806 and the lower hook 807. A heating component 809 is arranged on the axially pre-compressed nickel-titanium shape memory alloy sheet 808. The heating component 809 can be an electric heating wire. In this embodiment, the electric heating wire is arranged on the side of the axially pre-compressed nickel-titanium shape memory alloy sheet 808 facing the disc spring. During installation, after aligning the notch parts 808a with the hook positions, rotate the axially pre-compressed nickel-titanium shape memory alloy sheet 808 to make it snap into the upper hook 806 and the lower hook 807. The above describes the connection structure between the upper disc spring 802 and the axially pre-compressed nickel-titanium shape memory alloy sheet 808. The connection structure between the lower disc spring 804 and the axially pre-compressed nickel-titanium shape memory alloy sheet 808 is the same and will not be elaborated here. When it is necessary to increase the pre-tightening force, heat the axially pre-compressed nickel-titanium shape memory alloy sheet 808 through the heating component 809, so that the axially pre-compressed nickel-titanium shape memory alloy sheet 808 reaches a temperature to generate a recovery deformation, forming an axial expansion, thereby promoting further deformation of the upper disc spring 802 and the lower disc spring 804.

[0028] When installing the leak plugging device for real-time monitoring of the tightness of the pipeline flange, first perform the pre-tightening force calculation:

[0029] Axial strain is composed of two types of strain. The first type of axial strain is caused by the medium pressure in the pipeline, and the second type of axial strain is caused by external loads generated by the displacement of the pipeline and equipment and its own thermal deformation, etc.

[0030] The initial calculated length of the bolt is:

[0031]

[0032] In the formula: l0 is the initial length of the bolt, in mm; t f is the thickness of the flange ring, in mm; t g is the thickness of the gasket, in mm; d b is the nominal diameter of the bolt, in mm.

[0033] The length at which the bolt deforms only under its own load, without the influence of medium pressure, temperature, and external bending moment, is:

[0034] l b1 = l0 + q b W1

[0035] Where: lb1 is the initial deformation of the bolt only under its own load, in mm; qb is the elastic coefficient of the bolt in the initial situation, q b = l0 / (E b A b ), E b is the elastic modulus of the bolt at normal temperature, in MPa, A b is the total cross-sectional area of the bolt, in mm2; W1 is the initial bolt load, W1 = A g S K , Ag is the total area of the gasket, in mm2, Sk is the initial gasket stress, in MPa.

[0036] The amount of thermal deformation of the bolt:

[0037]

[0038] Where: is the amount of thermal deformation of the bolt, in mm; T1, T2 are the initial and operating temperatures, in K; α b , are the linear expansion coefficients of the bolt material at the initial and working temperatures, in °C -1 .

[0039] The amount of deformation of the bolt caused by creep:

[0040]

[0041] Where: is the creep amount of the bolt, in mm; is the creep strain of the bolt, dimensionless; σ is the bolt stress, in MPa; t is the time, in h; a1, b1, m, a2, and b2 are the creep constants of the bolt material.

[0042] The amount of deformation of the bolt under the action of an external bending moment:

[0043]

[0044] Where: is the amount of deformation caused by the external bending moment of the bolt, in mm; D b is the diameter of the bolt hole center circle, in mm; ρ is the centroid radius of the flange ring, in mm; θ f1 is the flange deflection angle caused by the external bending moment, in rad; α is the circumferential angle of the flange, in rad.

[0045] Under operating conditions, the deformation of the bolt is caused by the combined action of its own load, medium pressure, temperature, creep, and external bending moment.

[0046]

[0047] Where: l b2 is the deformation of the bolt under operating conditions, in mm; is the elastic coefficient of the bolt at the operating temperature is the elastic modulus of the bolt at the operating temperature, in MPa, A b is the total cross-sectional area of the bolt, in mm 2 ; W2 is the bolt load during operation, A g is the total area of the gasket, in mm 2 , D g is the average diameter of the gasket, in mm, P is the operating medium pressure, in MPa; S P is the gasket stress during operation, in MPa.

[0048] Axial strain of the bolt:

[0049]

[0050] Where: ε is the axial strain, dimensionless.

[0051] Required pre-tightening force:

[0052] F0 = F + Esε

[0053] Where: F0 is the pre-tightening force, in N; F is the initially applied force, in N; E is the elastic modulus of the bolt material, in MPa; ε is the axial strain, dimensionless; s is the cross-sectional area of the bolt, in mm 2 .

[0054] Apply the pre-tightening force to the bolt for installation according to the value of the pre-tightening force calculated theoretically. After the installation is completed, the magnitude of the pre-tightening force at the flange connection is mastered by reading the voltage change of the strain gauge 4 pasted at bolt 2. When the pre-tightening force at the connecting flange of the pipeline changes due to external factors, the pre-tightening force of bolt 2 used to connect flange 1 will change, causing bolt 2 to deform. The strain gauge 4 pasted on bolt 2 will also deform accordingly, and the collected voltage value will change correspondingly. The signal transmission device 5 will monitor the change of the strain gauge voltage value and transmit the numerical change data over a long distance to the host computer using the 4G network method, and the host computer processes it into tightness evaluation data. The tightness evaluation data is calculated by the following formula

[0055]

[0056] Where: A L , nl , m l , u l is the regression coefficient; η x is the dynamic viscosity of the pipeline-transported substance; S G0 is the minimum pre-tightening specific pressure of the gasket between the connecting flanges; D0 is the maximum outer diameter of the gasket between the connecting flanges; L L is the leakage rate; p is the medium pressure; S G is the pre-tightening force variable; D x is the outer diameter variable of the gasket between the connecting flanges.

[0057] When the tightness evaluation data exceeds a critical value, it is considered that leakage has occurred. At this time, it is difficult for the upper and lower conical springs 804 to ensure the pre-tightening force of the bolts under their own elastic forces. The upper computer will issue a warning of pipeline leakage risk and activate the conical spring gasket assembly 8. Specifically, the heating assembly 809 located between the axially pre-compressed nickel-titanium memory alloy sheet 808 and the upper conical spring 802 and between the axially pre-compressed nickel-titanium memory alloy sheet 808 and the lower conical spring 804 is controlled to heat the axially pre-compressed nickel-titanium memory alloy sheet 808. When the axially pre-compressed nickel-titanium memory alloy sheet 808 reaches a certain temperature, the memory effect of the nickel-titanium memory alloy sheet 808 forces it to return to its original state, that is, during the axial recovery process, an axial force is generated at the upper and lower conical springs to supplement the pre-tightening force lost by the flange bolt structure for emergency leak stoppage. According to the characteristics of the nickel-titanium memory alloy, it can be deformed arbitrarily at 0 - 40°C and it will restore its pre-deformed shape at 35 - 400°C. During this process, the axially pre-compressed nickel-titanium memory alloy sheet 808 gradually restores its original shape, applying a force to the upper and lower hooks 806 and 807 on the upper and lower conical springs. The hooks then apply a force to the upper and lower conical springs, causing further deformation of the upper and lower conical springs, increasing the distance between the upper fixing piece 801 and the lower fixing piece 805, thereby providing a pre-tightening force for the bolts, reducing the distance between the flanges, and achieving emergency leak stoppage.

Claims

1. A real-time monitoring and leak plugging device for the tightness of pipeline flanges, characterized in that, It includes a connecting flange, bolts, nuts, strain gauges and a judgment and detection module. The connecting flanges are respectively arranged on the pipelines, and there is a gap between the connecting flanges on the butt-jointed pipelines. The bolts and nuts are used in combination for fixing between the connecting flanges. The strain gauges are attached to the measuring parts of the bolts, and the measuring parts are the parts of the bolts located in the gap. The judgment and detection module receives the measurement data of the strain gauges and judges whether there is leakage according to the set threshold. A disc spring gasket assembly is provided between the bolts and the connecting flanges or between the nuts and the connecting flanges. The disc spring gasket assembly includes an upper fixing piece, an upper disc spring, a spacer, a lower disc spring and a lower fixing piece stacked in sequence. Axially pre-compressed nickel-titanium memory alloy sheets are clamped on the disc inner side walls of the upper disc spring and the lower disc spring. The axially pre-compressed nickel-titanium memory alloy sheets are disc-shaped and fit on the disc inner side walls of the upper disc spring and the lower disc spring. Heating components are provided on the axially pre-compressed nickel-titanium memory alloy sheets. When the heating components heat the axially pre-compressed nickel-titanium memory alloy sheets, the upper disc spring and the lower disc spring are driven by the axially pre-compressed nickel-titanium memory alloy sheets to axially extend and deform.

2. The leak plugging device for real-time monitoring of the tightness of a pipeline flange according to claim 1, characterized in that, A plurality of the bolts are provided and are equally distributed circumferentially on the connecting flange. At least two strain gauges are provided, and the central angles corresponding to any two adjacent strain gauges do not exceed 180 degrees.

3. The real-time leakage monitoring and plugging device for pipeline flange tightness according to claim 1, characterized in that A number of pairs of hooks are provided on the disc inner side walls of the upper disc spring and the lower disc spring. Each pair of hooks includes an upper hook and a lower hook with opposite openings. The axially pre-compressed nickel-titanium memory alloy sheet is clamped between the upper hook and the lower hook, and a number of notch parts are provided on the axially pre-compressed nickel-titanium memory alloy sheet.

4. The leak plugging device for real-time monitoring of the tightness of pipeline flanges according to claim 1, characterized in that, The disc openings of the upper disc spring and the lower disc spring are arranged oppositely. The upper fixing piece is fixedly connected to the upper disc spring, and the lower fixing piece is fixedly connected to the lower disc spring.

5. The leak plugging device for real-time monitoring of the tightness of a pipeline flange according to claim 1, wherein, Axial guide sleeves are provided at the edges of the spacer, and axial guide posts are provided at the edges of the upper fixing piece and the lower fixing piece. The guide posts penetrate through the guide sleeves.

6. A real-time monitoring and leak plugging method for the tightness of pipeline flanges, characterized in that, Based on the pipeline flange tightness real-time monitoring and leak plugging device according to claim 1 or 3, the judgment and detection module receives the measurement data of the strain gauges and compares it with the set threshold. When the measurement data exceeds the set threshold, the heating component is controlled to heat the axially pre-compressed nickel-titanium memory alloy sheet.

7. The real-time monitoring and leakage plugging method for the tightness of pipeline flanges according to claim 6, characterized in that, The receiving the measurement data of the strain gauges and comparing it with the set threshold is to convert the measurement data of the strain gauges into tightness evaluation data and compare it with the set threshold of the tightness evaluation data. The tightness evaluation data is calculated by the following formula , where: A L , n l , m l , u l are regression coefficients; η x is the dynamic viscosity of the pipeline transported substance; S G0 is the minimum pre-tightening specific pressure of the gasket between the connecting flanges; D 0 is the maximum outer diameter of the gasket between the connecting flanges; L L is the leakage rate; p is the medium pressure; S G is the pre-tightening force variable; D x is the outer diameter variable of the gasket between the connecting flanges.

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