MDLR test system and method for gas detection equipment

Abstract

According to the gas detection equipment MDLR test system and method, a gas detection equipment MDLR detection system is built, and the detection method is developed based on the system. The method belongs to a non-contact detection method, MDLR detection can be completed only through control of an upper computer and real-time observation of an inspector, the concentration of to-be-detected gas can be changed through front-end gas distribution, potential safety hazards caused by direct release of the to-be-detected gas and influences of external environment factors on a result are avoided, and the detection accuracy is improved. And the detection safety and reliability are improved. When the system is put into actual production detection, the blank in the field of gas detection equipment detection is filled, the updating iteration efficiency of gas detection equipment is improved, the industrial development is promoted, and the safety of the petrochemical industry production process is guaranteed from the technical level.

Description

Technical Field

[0001] The invention belongs to the technical field of infrared detection equipment, and in particular relates to a gas detection equipment MDLR testing system and method. Background Art

[0002] During production, petrochemical enterprises need to detect and discover the leakage and emission of various types of VOC gases in a timely manner to reduce safety hazards and environmental risks. To this end, petrochemical enterprises are required to count and analyze the parts where leakage may occur, and set up gas detection equipment to regularly monitor the sealing points of production equipment in real time, which places extremely high demands on the sensitivity and reliability of gas detection equipment. At present, the evaluation of sensitivity indicators unique to gas detection equipment is mainly divided into two categories: directly using the characteristics of the leaking gas itself, using the detection limit of the test gas leakage thermal imaging detection system for such characteristics as an intuitive evaluation indicator to describe the system detection performance, and based on the performance evaluation technology of conventional thermal imaging systems, according to the relevant characteristics of the gas target, defining two categories of laboratory measurement indicators for the performance of the gas leakage thermal imaging detection system.

[0003] Among them, the testing methods for the first type of performance indicators, namely the MDLR (minimum detectable leakage rate) of gas detection equipment, are relatively scarce and are limited to simply releasing VOC gas and detecting it. This method has the following problems: First, it is easily affected by environmental factors such as wind speed, temperature, and humidity, resulting in poor consistency in multiple measurements; second, simply releasing gas for testing cannot accurately simulate the actual user scenario; third, VOC gas is usually flammable and explosive gas, and there are certain safety hazards in directly releasing VOC gas for testing; fourth, in order to prevent safety hazards, it is usually necessary to control the concentration of released gas, which can only be achieved by replacing the standard gas cylinder, and the process is cumbersome; fifth, the frequent use of standard gas cylinders greatly increases the test cost; finally, different manufacturers will use different concentrations of gas when testing, and it is difficult to unify the results of simply judging the flow rate. Summary of the invention

[0004] In order to solve the problems that the existing testing methods have certain safety risks and are easily affected by environmental factors, resulting in poor consistency of results, etc., the present invention provides a gas detection equipment MDLR testing system and method.

[0005] A gas detection equipment MDLR test system, characterized in that it includes a host computer, a mixed gas proportioner, a vacuum meter, a flow meter and a workbench, on which a main pipeline module, a surface source black body, a gas leakage alarm, a gas detection device and a fume hood are installed, explosion-proof pressure reducing valves are respectively arranged at the bottle mouths of the nitrogen cylinder and the gas cylinder to be tested, and then connected to the mixed gas proportioner through an electrical pipeline, and a flow meter electrically connected to the host computer is arranged at the access port, the mixed gas proportioner is electrically connected to the host computer, and at the same time, the mixed gas proportioner is connected to the main pipeline module through a pipeline, and a manual baffle valve is arranged at the access port; the fume hood is arranged Above the workbench and blocking the workbench on all sides, transparent windows are set on the four walls of the exhaust cabinet, the main line module is set on the workbench and keeps left-right symmetry, a gas detection device is placed at the front end of the main line module, the gas detection device is electrically connected to the upper machine, a surface source black body is placed at the rear end of the main line module, a gas leakage alarm is installed at the edge of the workbench, a resistance gauge is installed on the main line module, and the resistance gauge is electrically connected to the vacuum gauge, the main line module includes a pipeline and a CF35 flange connecting the pipeline, an instrument panel leakage point is set on the pipeline, a flange interface leakage point is set at the CF35 flange connection, and a point leakage point is opened on the pipeline.

[0006] The MDLR test method of gas detection equipment includes the steps of gas preparation, numerical detection and host computer calculation. The specific steps are as follows: S1 Gas Preparation S1-1 sets the temperature of the surface source black body to a fixed value, maintains a constant temperature difference with the ambient temperature, fills the fume hood with the black body, turns on the fume hood's exhaust system, and opens one of the three leakage points; S1-2 The host computer transmits a signal to the mixed gas proportioner, and controls the gas flow rate of the nitrogen cylinder and the gas cylinder to be tested input into the mixed gas proportioner through the flow meter, and transmits the flow data of the two gases back to the host computer. The nitrogen and the gas to be tested are mixed into the test gas of the required concentration in the mixed gas proportioner; S2 Value Detection S2-1 and open the manual baffle valve to allow the test gas to enter the pipeline of the main pipeline module; S2-2 Observe the change in the vacuum gauge pressure reading. When the pressure change stabilizes, it means that the pressure of the test gas in the main pipeline is balanced. It is judged that the test gas input is equal to the output at this time, and dynamic balance is achieved; S2-3 Observe the infrared imaging of the gas at the leakage point observed by the gas detection equipment through the host computer, adjust the flow meter and the test gas proportioner to the infrared limit imaging of the gas observation, and record the output test gas flow F and test duration T at this time; S3 The host computer calculates and inputs the measured value into the host computer for calculation S3-1 The test gas is 99.99% pure gas with a concentration of Cppm. The volume V of the test gas is calculated by formula (1): QUOTE (1) S3-2 Calculate the MDLR of the gas detection equipment using formula (2) QUOTE ×60 (2) In formula (1) and formula (2): MDLR is the minimum detectable leakage rate of the gas detection equipment, in g / h; M is the molar mass of the test gas, in g / mol; V is the volume of the test gas, in L; Vm is the molar volume of the test gas, in L / mol; F is the test gas flow rate, in L / min; T is the test time, in minutes.

[0007] S4 Open the other two leakage points respectively and repeat the above steps to complete the test of three leakage points.

[0008] Furthermore, when observing the infrared imaging of the gas in S2-3, when there is gas imaging, the flow meter and the mixed gas proportioner are adjusted to reduce the output of the test gas until it can be observed to the limit; when there is no gas imaging, the flow meter and the mixed gas proportioner are adjusted to increase the output of the test gas until it can be observed to the limit.

[0009] Furthermore, the test gas concentration is Xppm standard gas, and the volume of the gas to be tested is calculated by formula (3): QUOTE (3).

[0010] The beneficial effects of the present invention are as follows: the test system ensures that the test gas concentration is within a safe range through front-end gas distribution, and can flexibly change the gas concentration and flow rate, reducing the danger and gas cost in the process of replacing the standard gas, setting a surface source black body as the background, controlling the background temperature, and improving the consistency of the test results; the three leakage points can simulate three types of actual scenes where the refinery pipeline is prone to leakage, ensuring the reliability of the test results; the test system is placed in the workbench exhaust cabinet to ensure the overall effective exhaust of the cabinet without affecting the test, and a gas leakage alarm device is installed in the cabinet to ensure the safety of the test process. The system can complete the detection of MDLR parameters through the control, data acquisition and calculation functions of the upper computer, without the need for manual complex operations in the early stage and tedious calculations in the later stage, and improves the detection accuracy, ensuring the reliability of the results. The entire test process is non-contact detection to ensure the safety of the operator; and the entire system is simple to operate, and only needs simple training to produce detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 The figure is a flow chart of the test method.

[0012] Figure 2 Schematic diagram of the test system.

[0013] Figure 3 This is a schematic diagram of the leakage point structure of the instrument panel.

[0014] Figure 4 This is a schematic diagram of the point leakage point structure.

[0015] Figure 5 This is a schematic diagram of the leakage point structure at the interface.

[0016] Figure 6 This is a schematic diagram of the exhaust cabinet structure.

[0017] Among them: 1-host computer, 2-mixed gas proportioner, 3-vacuum meter, 4-flow meter, 5-workbench, 6-main line module, 7-surface source blackbody, 8-resistance gauge, 9-gas leakage alarm, 10-manual baffle valve, 11-leakage point at the instrument panel, 12-point leakage point, 13-leakage point at the flange interface, 14-nitrogen cylinder, 15-gas cylinder to be tested, 16-explosion-proof pressure reducing valve, 17-CF35 flange, 18-gas detection equipment, 19-exhaust plate, 20-exhaust cabinet. DETAILED DESCRIPTION

[0018] Example 1: MDLR parameters of a foreign brand of gas detection equipment are tested using a gas detection equipment MDLR test system, including a host computer 1, a mixed gas proportioner 2, a vacuum meter 3, a flow meter 4 and a workbench 5, on which a main line module 6, a surface source blackbody 7, a gas leak alarm 9, a gas detection device 18 and a fume hood 20 are installed.

[0019] Explosion-proof pressure reducing valves 16 are respectively arranged at the mouths of the nitrogen cylinder 14 and the gas cylinder 15 to be tested, and then connected to the mixed gas proportioner 2 through electrical pipelines, and a flow meter 4 electrically connected to the host computer 1 is arranged at the access port, the mixed gas proportioner 2 is electrically connected to the host computer 1, and the mixed gas proportioner 2 is connected to the main pipeline module 6 through pipelines, and a manual baffle valve 10 is arranged at the access port. The host computer 1 is a computer with a Camerlink interface, equipped with a VCE-CLEX02 Camerlink acquisition card, a dedicated cable and MDLR calculation software.

[0020] The fume hood 20 is arranged above the workbench 5 and blocks the workbench 5 on all sides. Transparent windows are arranged on the four walls of the fume hood 20. An exhaust plate 19 that moves up and down is arranged in the fume hood 20. A plurality of holes are provided on the exhaust plate 19. When the exhaust plate 19 moves downward, the gas in the fume hood 20 is discharged upward from the holes to the outside of the fume hood 20 and the test gas is ensured to be emptied without affecting the observation. The main pipeline module 6 is arranged on the workbench and keeps left-right symmetry. A gas detection device 18 is placed at the front end of the main pipeline module 6. The gas detection device 18 is electrically connected to the host computer 1. A surface source black body 7 is placed at the rear end of the main pipeline module 6. A gas leakage alarm 9 is installed at the edge of the workbench to prevent the gas concentration from being too high during the test and causing safety hazards. A resistance gauge 8 is installed on the main pipeline module 6, and the resistance gauge 8 is electrically connected to the vacuum gauge 3 to monitor the pressure change in the pipeline, so as to judge whether the gas input and output are balanced. The flow rate of the test gas injected into the main pipeline module 6 is the sum of the flow meter 4 statistically injected into the mixed gas proportioner, and the concentration of the test gas is jointly adjusted by the flow meter 4 and the mixed gas proportioner 2.

[0021] The main pipeline module 6 includes a pipeline and a CF35 flange 17 connecting the pipeline, wherein the pipeline is made of 304 stainless steel, and there are three pipelines in total. A leakage point 11 is set at the instrument panel on the first pipeline, a leakage point 13 is set at the flange interface at the connection of the CF35 flange 17, and a point leakage point 12 is opened on the third pipeline, for a total of three leakage points. The CF35 flange 17 adopts a blind flange seal.

[0022] The MDLR test method of gas detection equipment includes the steps of gas preparation, numerical detection and host computer calculation. The specific steps are as follows: S1 Gas preparation.

[0023] S1-1 Place the gas detection device 18 in front of the main line module 6, 2 meters away from the main line module 6, so that the leakage point on the main line module 6 is located at the center of the field of view of the gas detection device 18; set the temperature of the surface source blackbody 7 to 5K, maintain a constant temperature difference with the ambient temperature, and make the blackbody fill the exhaust cabinet; turn on the exhaust system of the exhaust cabinet 20, open the leakage point 11 at the instrument panel, and close the other two leakage points.

[0024] S1-2 The upper computer 1 transmits a signal to the mixed gas proportioner 2, and controls the flow rates of the nitrogen cylinder 14 and the test gas cylinder 15 through the flow meter 4 and transmits the flow rate data of the two gases back to the upper computer 1. The nitrogen and the test gas are mixed into the test gas of the required concentration in the mixed gas proportioner 2; in this embodiment, the test gas is methane, which is introduced at a flow rate of 1L / min; nitrogen is introduced at a flow rate of 9L / min, and a methane gas with a concentration of 100000ppm is prepared by the mixed gas proportioner 2; in this process, the explosion-proof pressure reducing valve 16 can ensure the safety of the gas output process.

[0025] S2 Value Detection S2-1 Open the manual flapper valve 10 to allow the test gas to enter the pipeline of the main pipeline module 6; S2-2 Observe the change in the pressure reading of vacuum gauge 3. When the pressure change stabilizes, it means that the methane gas output and input in the main pipeline are balanced. The reading of this vacuum machine is 10L / min and the leakage concentration is 100000ppm.

[0026] S2-3 Observe the infrared imaging of the leaked gas at the leak point detected by the gas detection device 9 through the host computer 1, keep the methane gas concentration unchanged, and slowly reduce the output methane gas flow. When the methane flow is reduced to 0.4L / min and the nitrogen flow is 3.6L / min, observe the image of the gas detection device. A plume of airflow is faintly visible for 3 consecutive minutes. It is determined that the detection capability limit of the device is reached at this time, and the gas flow at this time is recorded; S3 The host computer calculates and inputs the measured value into the host computer for calculation S3-1 Since methane gas is 99.99% pure gas with a concentration of Cppm, the volume V of the test gas is calculated by formula (1): V = F × T (1) S3-2 Calculate the MDLR of the gas detection equipment using formula (2) MDLR=(M×V) / (T×V_m)×60 (2) In formula (1) and formula (2): MDLR is the minimum detectable leakage rate of the gas detection equipment, in g / h; M is the molar mass of the test gas, in g / mol; V is the volume of the test gas, in L; Vm is the molar volume of the test gas, in L / mol; F is the test gas flow rate, in L / min; T is the test time, in minutes.

[0027] The final calculated MDLR value of this brand of gas detection equipment is 17.14g / h.

[0028] S4 Replace the point leak 12 and the leak 13 at the flange interface and repeat the above steps. The MDLR results obtained are consistent.

[0029] Example 2: This example is consistent with Example 1 in black body temperature, gas detection equipment and steps. The gas to be tested is replaced with methane standard gas with a concentration of 20000ppm. The volume is calculated by formula (3): QUOTE (3).

[0030] Where X is 20000.

[0031] The MDLR test procedure is the same as that in Example 1. Only the methane standard gas in the gas cylinder 15 to be tested needs to be input separately, and nitrogen gas distribution is not required. The output flow rate of the methane standard gas is adjusted to 10 L / min. The image of the gas detection device is observed. If the gas to be tested cannot be observed, the input gas flow rate is slowly increased. When the methane standard gas flow rate is increased to 20.1 L / min, a feather-like airflow can be vaguely seen in the image for 3 consecutive minutes. It can be determined that this is the limit of its detection capability, and the gas flow rate at this time is recorded. The observed methane limit flow rate, concentration, and gas release time were input into the host computer, and the MDLR value of the gas detection equipment was calculated to be 17.23 g / h.

[0032] Replace the point leak and the leak at the flange interface and repeat the above steps. The MDLR results are consistent.

Claims

1. A gas detection equipment MDLR test system, characterized in that: It includes a host computer, a mixed gas proportioner, a vacuum meter, a flow meter and a workbench. The workbench is installed with a main pipeline module, a surface source black body, a gas leakage alarm, a gas detection device and a fume hood. Explosion-proof pressure reducing valves are respectively set at the bottle mouths of the nitrogen cylinder and the gas cylinder to be tested, and then connected to the mixed gas proportioner through an electrical pipeline, and a flow meter electrically connected to the host computer is set at the access port. The mixed gas proportioner is electrically connected to the host computer. At the same time, the mixed gas proportioner is connected to the main pipeline module through a pipeline, and a manual baffle valve is set at the access port; the fume hood is set above the workbench and the four sides of the workbench are connected. The surroundings are blocked, transparent windows are set on the four walls of the exhaust cabinet, the main line module is set on the workbench and keeps left-right symmetry, a gas detection device is placed at the front end of the main line module, the gas detection device is electrically connected to the upper machine, a surface source black body is placed at the rear end of the main line module, and a gas leakage alarm is installed at the edge of the workbench. A resistance gauge is installed on the main line module, and the resistance gauge is electrically connected to the vacuum gauge. The main line module includes a pipeline and a CF35 flange connecting the pipeline, an instrument panel leakage point is set on the pipeline, a flange interface leakage point is set at the CF35 flange connection, and a point leakage point is opened on the pipeline.

2. The MDLR test method of gas detection equipment includes the steps of gas preparation, numerical detection and host computer calculation. The specific steps are as follows: S1 Gas Preparation S1-1 sets the temperature of the surface source black body to a fixed value, maintains a constant temperature difference with the ambient temperature, fills the fume hood with the black body, turns on the fume hood's exhaust system, and opens one of the three leakage points; S1-2 The host computer transmits a signal to the mixed gas proportioner, and controls the gas flow rate of the nitrogen cylinder and the gas cylinder to be tested input into the mixed gas proportioner through the flow meter, and transmits the flow data of the two gases back to the host computer. The nitrogen and the gas to be tested are mixed into the test gas of the required concentration in the mixed gas proportioner; S2 Value Detection S2-1 and open the manual baffle valve to allow the test gas to enter the pipeline of the main pipeline module; S2-2 Observe the change in the vacuum gauge pressure reading. When the pressure change stabilizes, it means that the pressure of the test gas in the main pipeline is balanced. It is judged that the test gas input is equal to the output at this time, and dynamic balance is achieved; S2-3 Observe the infrared imaging of the gas at the leakage point observed by the gas detection equipment through the host computer, adjust the flow meter and the test gas proportioner to the infrared limit imaging of the gas observation, and record the output test gas flow F and test duration T at this time; S3 The host computer calculates and inputs the measured value into the host computer for calculation S3-1 The test gas is 99.99% pure gas with a concentration of Cppm. The volume V of the test gas is calculated by formula (1): （1） S3-2 Calculate the MDLR of the gas detection equipment using formula (2) ×60 （2） In formula (1) and formula (2): MDLR is the minimum detectable leakage rate of the gas detection equipment, in g / h; M is the molar mass of the test gas, in g / mol; V is the volume of the test gas, in L; Vm is the molar volume of the test gas, in L / mol; F is the test gas flow rate, in L / min; T is the test time, in minutes. 3.S4 Open the other two leakage points respectively and repeat the above steps to complete the test of three leakage points.

4. The MDLR test method of the gas detection equipment according to claim 1, characterized in that When observing the infrared imaging of gas in S2-3, when there is gas imaging, the flow meter and the mixed gas proportioner are adjusted to reduce the output of the test gas until the limit observation can be achieved; when there is no gas imaging, the flow meter and the mixed gas proportioner are adjusted to increase the output of the test gas until the limit observation can be achieved.

5. The MDLR test method of the gas detection equipment according to claim 1, characterized in that The test gas concentration is Xppm standard gas, then the volume of the gas to be tested is calculated by formula (3): （3）。

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