A method and system for in-situ detection of piston-type volumetric tube seal wear

Abstract

The application discloses a piston volumetric tube sealing element wear in-situ detection method and system. The application firstly measures the inlet temperature, pressure, outlet temperature, pressure and fluid dynamic viscosity of the piston volumetric tube during working, and obtains the flow output of the piston volumetric tube; secondly, the total pressure drop is calculated based on the inlet pressure and the outlet pressure; then, the fluid flow pressure loss is calculated according to the flow, the fluid dynamic viscosity and the volumetric tube structure; finally, the friction of the piston sealing element is calculated, and the current wear state of the piston sealing element is characterized by the friction. The application can detect the wear of the piston sealing element in-situ without disassembling the piston volumetric tube, ensures that the volumetric tube works under reliable sealing conditions, and further ensures the measurement accuracy. The application can realize the alarm prompt of the abnormal wear of the sealing element, and avoid the loss caused by the scratch of the measurement cylinder caused by excessive wear.

Description

Technical Field

[0001] This invention belongs to the field of instrumentation, specifically relating to a method and system for in-situ detection of wear on piston-type volume tube seals. Background Technology

[0002] Calibration of flow meters is crucial for the accuracy of flow measurement. Piston-type volumetric tubes, as dynamic volumetric flow standard devices, have many advantages such as simple structure, convenient use, and on-site verification. Therefore, piston-type volumetric tubes are widely used in the petrochemical and metrology calibration industries.

[0003] The reciprocating dynamic seal inside the piston-type volumetric tube is a key component of the piston system, playing a crucial role in ensuring the accuracy of flowmeter calibration. However, in actual use, the seal wears down during the reciprocating motion, potentially leading to seal failure and internal leakage, thus reducing the volumetric tube's metering accuracy. Furthermore, abnormal wear of the dynamic seal, which includes a metal spring, can cause the metal spring to directly contact the inner wall of the volumetric tube, resulting in scratches and damage to the metering section, and in severe cases, rendering the equipment unusable.

[0004] The wear process of the reciprocating dynamic seal in the volumetric tube mechanical system is quite complex, and the wear of the seal is difficult to measure in situ. The seal can only be disassembled, maintained and replaced periodically according to the operating cycle. This process is not only cumbersome, but also requires calibration of the standard volume of the piston-type volumetric tube flow standard device after assembly. Moreover, this method cannot detect abnormal wear in time, making it difficult to guarantee the accuracy of the volumetric tube in long-term service. Summary of the Invention

[0005] To address the aforementioned issues, this invention proposes an in-situ detection method and system for wear of piston-type volume tube seals, enabling the detection of the wear condition of the piston dynamic seal assembly without disassembling the device, thereby accurately determining the wear condition of the volume tube piston dynamic seal.

[0006] In a first aspect, the present invention provides a method for in-situ detection of wear on a piston-type volume tube seal, comprising the following steps:

[0007] The inlet temperature and pressure, outlet temperature and pressure, and fluid dynamic viscosity of the piston-type volumetric tube are measured during operation to obtain the output flow rate of the piston-type volumetric tube.

[0008] Calculate the total pressure drop based on import and export pressures;

[0009] Calculate the pressure loss of fluid flow based on flow rate, fluid dynamic viscosity, and volumetric tube structure;

[0010] Calculate the frictional force of the piston seal, which characterizes the current wear state of the piston seal.

[0011] A second aspect of the present invention provides an in-situ wear detection system for piston-type volume tube seals, comprising:

[0012] The flow acquisition unit is used to measure the inlet temperature and pressure, outlet temperature and pressure, and fluid dynamic viscosity of the piston-type volumetric tube during operation, in order to obtain the flow rate output by the piston-type volumetric tube.

[0013] The total pressure drop calculation unit is used to calculate the total pressure drop based on the inlet and outlet pressures.

[0014] The flow pressure loss calculation unit is used to calculate the fluid flow pressure loss based on flow rate, fluid dynamic viscosity, and volumetric tube structure.

[0015] The wear condition assessment unit is used to calculate the friction force of the piston seal, which characterizes the current wear condition of the piston seal.

[0016] A third aspect of the present invention provides an in-situ wear detection device for piston-type volume tube seals, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the above-described in-situ wear detection method for piston-type volume tube seals.

[0017] In a fourth aspect, the present invention provides a computer-readable storage medium storing a computer program for performing the above-described in-situ detection method for wear of piston-type volume tube seals.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] This invention is based on pressure sensors installed at the inlet and outlet and tribological analysis, without requiring any modification to the original mechanical structure of the volume tube, making the method simple and efficient.

[0020] This invention enables in-situ detection of piston seal wear without disassembling the piston-type volume tube, ensuring that the volume tube operates under reliable sealing conditions and thus guaranteeing measurement accuracy.

[0021] This invention can provide an alarm for abnormal wear of the seal, thus avoiding losses caused by scratches on the metering cylinder due to excessive wear.

[0022] This invention enables accurate determination of the maintenance cycle of volume tubes operating under different conditions. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the working principle of a piston-type volume tube.

[0024] Figure 2A schematic diagram illustrating the pressure drop and seal friction analysis of a piston-type volumetric tube.

[0025] Figure 3 Flowchart of in-situ detection method for wear of volume tube seals;

[0026] Figure 4 This is an in-situ detection device for wear of piston-type volumetric tube seals. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] This invention detects the wear condition of the seal by monitoring pressure changes upstream and downstream of the volume tube and actual operating conditions. Seal wear causes changes in contact stress and friction coefficient at the sealing interface, which in turn alters the friction between the seal and the piston cylinder wall, ultimately leading to changes in inlet and outlet pressure drops. According to tribological principles, there is a corresponding relationship between pressure drop changes and seal wear.

[0029] This invention detects the fluid pressure upstream and downstream of the piston by symmetrically installing pressure sensors at the inlet and outlet of the piston-type volume tube, and the total pressure drop ΔP of the device is represented by the difference between the two sensors. The pressure drop is mainly composed of friction generated by the reciprocating motion of the seal and pressure loss of the fluid flow, as shown in equation (1).

[0030] ΔP=P1-P2, (1)

[0031] In the formula: P1 is the pressure at the inlet of the volumetric tube; P2 is the pressure at the outlet of the volumetric tube.

[0032] Force analysis of the piston in the volume tube shows that the pressure drop can be expressed by equation (2).

[0033] ΔP=P L +ΔP FL -(P R -ΔP FR (2)

[0034] P L AP R A = F f1 +F f2 +F f3 (3)

[0035]

[0036] In the formula: P R P represents the pressure on the right side of the piston. L The pressure on the left side of the piston; ΔP FR The pressure loss during flow from the inlet of the volumetric tube to the right side of the piston; ΔP FLThe flow pressure loss from the outlet to the left side of the piston is represented by A; the piston cross-sectional area is represented by F. f1 F f2 and F f3 F represents the frictional forces of the rod seal and piston seal, respectively; f σ is the frictional force; f is the coefficient of friction; d is the rod diameter or inner diameter; b is the contact width; σ is the contact stress.

[0037] The method for calculating pressure loss caused by fluid flow is as follows:

[0038]

[0039] In the formula: η is the fluid dynamic viscosity; L is the flow length; Q is the volumetric flow rate; R is the piston cylinder radius.

[0040]

[0041] In the formula: d3 is the inner diameter of the cylinder; b3 is the contact width between the piston seal and the piston cylinder; d1 is the outer diameter of the piston rod; b1 is the contact width between the upstream and downstream sealing assemblies and the piston rod; σ1 is the contact stress between the piston seal and the cylinder wall; σ2 is the contact stress between the piston rod and the upstream and downstream sealing assemblies; L R The distance between the right-side pressure sensor and the piston; L L This represents the distance between the pressure sensor on the left and the piston.

[0042] Based on this relationship, the wear condition of the piston seal in a piston-type volume tube can be detected by measuring the pressure drop.

[0043] This invention provides a method for in-situ detection of wear on piston-type volume tube seals, enabling wear detection of piston seals without disassembling the piston-type volume tube.

[0044] Example of the in-situ wear detection method for piston-type volume tube seal of the present invention:

[0045] like Figure 1 As shown, the piston-type volumetric tube flow standard device measures flow based on the principle of volume displacement. The piston moving from the position in the upper diagram to the position in the lower diagram represents the piston rod 3 pushing the piston 7 from the start of the detection photoelectric switch 1 to the end of the detection photoelectric switch 2. During this process, the fluid volume displaced by the piston 7 represents the standard volume V in the detection process (fluid enters from the inlet 6 and exits from the outlet 8). The detection time is Δt, thus obtaining the instantaneous flow rate.

[0046]

[0047] The parameters measured by the inlet temperature sensor 4, inlet pressure sensor 5, outlet pressure sensor 9, and outlet pressure sensor 10 during this process are used by the device control system 11 to correct the volume and calculate the flow rate.

[0048] like Figure 2 As shown, the piston-type volume tube seal mainly consists of an upstream sealing assembly 12, a piston-type sealing element 13, and a downstream sealing assembly 14, thus corresponding to three frictional forces F. f1 F f2 F f3 .

[0049] Wear condition detection is performed simultaneously with the normal operation of the volume tube; that is, each calibration of the volume tube also includes a seal wear condition detection. After the calibration preparation is completed, the volume tube starts working, and the piston moves downstream synchronously with the fluid, passing through the start detection photoelectric switch 1 and the end detection photoelectric switch 2 in sequence, and outputting the calibration time Δt and the inlet and outlet temperatures and pressures during this process.

[0050] The temperature and pressure during the detection process are measured and the fluid dynamic viscosity is obtained using the built-in calculation program; the total pressure drop is measured using Equation (1); and the flow rate is output using the calculation program obtained using Equation (7).

[0051] The flow rate, viscosity, and volumetric tube structure parameters are input into the calculation program obtained by equation (5) and the fluid flow pressure loss under the current working condition is output. Then, the friction force of the piston seal is output by the calculation program obtained by equation (6).

[0052] The calculated change in friction force reflects the current wear condition of the seal. When the friction force exceeds a set threshold range, it indicates abnormal seal wear, requiring replacement of the seal. See [link to relevant documentation]. Figure 3 .

[0053] This invention also discloses an in-situ wear detection system for piston-type volume tube seals, comprising:

[0054] The flow acquisition unit is used to measure the inlet temperature and pressure, outlet temperature and pressure, and fluid dynamic viscosity of the piston-type volumetric tube during operation, in order to obtain the flow rate output by the piston-type volumetric tube.

[0055] The total pressure drop calculation unit is used to calculate the total pressure drop based on the inlet and outlet pressures.

[0056] The flow pressure loss calculation unit is used to calculate the fluid flow pressure loss based on flow rate, fluid dynamic viscosity, and volumetric tube structure.

[0057] The wear condition assessment unit is used to calculate the friction force of the piston seal, which characterizes the current wear condition of the piston seal.

[0058] like Figure 4 As shown in the illustration, this invention also discloses an in-situ wear detection device for piston-type volume tube seals, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of an in-situ wear detection method for piston-type volume tube seals. The memory may include main memory, such as high-speed random access memory, or it may also include non-volatile memory, such as at least one disk storage device. The processor, network interface, and memory are interconnected via an internal bus, which may be an industry-standard architecture bus, a peripheral component interconnection standard bus, an extended industry-standard architecture bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. The memory stores the program; specifically, the program may include program code, which includes computer operation instructions. The memory may include main memory and non-volatile memory, and provides instructions and data to the processor.

[0059] This invention also discloses a computer-readable storage medium storing a computer program. When executed by a processor, the computer program implements the steps of a method for in-situ detection of wear on piston-type volume tube seals. Specifically, the computer-readable storage medium includes, but is not limited to, volatile memory and / or non-volatile memory. The volatile memory may include random access memory (RAM) and / or cache memory, etc. The non-volatile memory may include read-only memory (ROM), hard disk, flash memory, optical disk, magnetic disk, etc.

[0060] The specific embodiments of the present invention have been described above with reference to the accompanying drawings. However, these descriptions should not be construed as limiting the scope of the present invention. The scope of protection of the present invention is defined by the appended claims. Any modifications based on the claims of the present invention are within the scope of protection of the present invention.

Claims

1. A method for in-situ detection of wear on piston-type volume tube seals, characterized in that... The method includes the following steps: The inlet temperature and pressure, outlet temperature and pressure, and fluid dynamic viscosity of the piston-type volumetric tube are measured during operation to obtain the output flow rate of the piston-type volumetric tube. Calculate the total pressure drop based on import and export pressures; Calculate the pressure loss of fluid flow based on flow rate, fluid dynamic viscosity, and volumetric tube structure; Calculate the frictional force of the piston seal, which characterizes the current wear state of the piston seal; Let the friction forces of the upstream sealing assembly, the piston seal, and the downstream sealing assembly be respectively... F f1 , F f2 and F f3 ;but: in P R This refers to the pressure on the right side of the piston. P L The pressure on the left side of the piston. A This represents the piston's cross-sectional area. The fluid flow pressure loss includes the flow pressure loss from the volumetric tube inlet to the right side of the piston. ΔP FR and the flow pressure loss from the outlet to the left side of the piston. ΔP FL The following relationship must be satisfied: in ΔP Total pressure drop; Calculate the frictional force of the piston seal based on the following relationship: in L R The distance between the right-side pressure sensor and the piston, L L The distance between the left pressure sensor and the piston, Q For traffic, R For piston cylinder radius, η This refers to the fluid dynamic viscosity.

2. The method for in-situ detection of wear on piston-type volume tube seals according to claim 1, characterized in that: The total pressure drop is mainly composed of friction generated by the reciprocating motion of the seal and pressure loss due to fluid flow.

3. A piston-type volume tube seal wear in-situ detection system, used to implement the method of claim 1, characterized in that, include: The flow acquisition unit is used to measure the inlet temperature and pressure of the piston-type volumetric tube during operation. The outlet temperature, pressure, and fluid dynamic viscosity are used to obtain the flow rate output of the piston-type volumetric tube; The total pressure drop calculation unit is used to calculate the total pressure drop based on the inlet and outlet pressures. The flow pressure loss calculation unit is used to calculate the fluid flow pressure loss based on flow rate, fluid dynamic viscosity, and volumetric tube structure. The wear condition assessment unit is used to calculate the friction force of the piston seal, which characterizes the current wear condition of the piston seal.

4. A piston-type volume tube seal wear in-situ detection device, characterized in that, include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the program, implements the in-situ detection method for wear of a piston-type volume tube seal as described in claim 1 or 2.

5. A computer-readable storage medium, characterized in that, The storage medium stores a computer program, which is used to execute the in-situ detection method for wear of piston-type volume tube seals as described in claim 1 or 2.

Images