DEVICE FOR SAMPLING A HIGH FLOW RATE GAS LEAK

Abstract

A device for quantitatively detecting a leak of a gas of interest including a suction pipe having an upstream suction inlet intended to be brought into the vicinity of a region within which a leak is to be detected, a ventilation apparatus generating a gas stream in the suction pipe having a flow rate greater than 300 m3/H circulating from the upstream suction inlet to the downstream of the pipe, and downstream of the ventilation apparatus, a sampling member.

Claims

1. A device for sampling a leak of a gas of interest comprising: a suction pipe having an upstream suction inlet intended to be brought into the vicinity of a region within which a leak is to be sampled, a ventilation apparatus generating a gas stream circulating in the suction pipe from the upstream suction inlet to the downstream of the suction pipe, and downstream of the ventilation apparatus, a member for sampling the gas circulating in the suction pipe, wherein the device includes a tank receiving gas sampled by the sampling member.

2. The device according to claim 1, wherein the ventilation apparatus generates a gas stream having a flow rate greater than 300 m.sup.3/H, or greater than 1,000, 2,000, or 3,000 m.sup.3/H.

3. The device according to claim 2, configured so that the speed of the gas stream is comprised between 50 and 130 m/s or between 50 and 100 m/s.

4. The device according to claim 1, wherein the device includes a detector of a concentration of the gas of interest receiving gas sampled by the sampling member.

5. The device according to claim 4, wherein the detector is a detector chosen from the list comprising: a Herriott cell infrared absorption detector, semiconductor detector, photoionization detector, flame ionization detector, Open Path Laser Spectrometer with a Quantum Cascade Laser source, electrochemical cell, catalytic filament, and katharometer.

6. The device according to claim 1, wherein the suction pipe is flared at the upstream suction inlet.

7. The device according to claim 1, comprising a gas mixer disposed in the suction pipe downstream of the upstream suction inlet and upstream of the sampling member.

8. The device according to claim 1, wherein the ventilation apparatus is a Venturi effect apparatus including an injector of a motive gas arranged in the vicinity of the upstream suction inlet of the suction pipe.

9. The device according to claim 1, wherein the ventilation apparatus includes a fan supplied with electrical energy by a battery.

10. The device according to claim 1, being a device according to one or more of the ATEX Standard and a device according to the AMCA Standard 99-0401.

11. The device according to claim 1, wherein the pipe is rigid.

12. The device according to claim 1, comprising, at the upstream suction inlet, a flange or a skirt.

13. The device according to claim 1, wherein the suction pipe has a length comprised between 20 and 200 centimeters, and a diameter comprised between 3 and 30 centimeters.

14. The device according to claim 4, comprising a calculator of a leak flow rate based on a concentration delivered by the detector.

15. The device according to claim 1, wherein the sampling member is provided with a plurality of orifices (OR′, OR″).

16. The device according to claim 1, wherein the tank is a flexible bag.

17. A method for using a device according to claim 1, wherein a leak is sampled from the surface of the ground and the device comprises a cover surrounding the upstream suction inlet, the method comprising: placing the device with the suction inlet in the vicinity of the surface of the ground, so that the cover defines a suction region of the ground, and placing a spacer structure between, on the one hand, the suction region of the ground and, on the other hand, the device and the cover, to leave free air passages between the edges of the cover and the upstream suction inlet, and between the suction region of the ground and the upstream suction inlet.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0090] Other characteristics and advantages of the present disclosure will become apparent from the description given below, with reference to the appended drawings which illustrate one exemplary embodiment without any limitation. In the figures:

[0091] FIG. 1 is a schematic representation of a device according to one example.

[0092] FIG. 2 is a schematic representation of a device similar to that of FIG. 1 with an additional gas cylinder and another form of injector.

[0093] FIG. 3 is a schematic representation of a device according to another example.

[0094] FIG. 4 is a schematic representation of a device according to another example.

[0095] FIG. 5A is a representation of an example of a sample tube.

[0096] FIG. 5B represents the sample tube of FIG. 5A in a suction pipe.

[0097] FIG. 6A is a representation of another example of a sample tube.

[0098] FIG. 6B represents the sample tube of FIG. 6A in a suction pipe.

DETAILED DESCRIPTION

[0099] Devices which allow sampling gas leaks will now be described. This sampling allows quantitatively detecting gas leaks. Two alternatives will be described: the quantitative detection by means of a detector of the device, or the subsequent detection from gas stored in a tank (these alternatives are nevertheless compatible with each other).

[0100] In the following examples, methane is the gas of interest to be detected. The disclosure is nevertheless in no way limited to the detection of methane and is also aimed at the detection of other gases.

[0101] By “quantitatively detecting”, it is meant both determining that this gas is present, and determining the intensity of the leak, for example by estimating a concentration of this gas or also by estimating a flow rate associated with the leak.

[0102] FIG. 1 represents a quantitative leak detection device 100 (that is to say a sampling device which can also perform quantitative detection).

[0103] This device includes a suction pipe 101, here a rigid pipe made for example of a plastic material made of aluminum or cardboard. The suction pipe 101 has a length included between 10 and 200 centimeters, and a diameter included between 3 and 30 centimeters. Thus, the suction pipe 101 can be easily handled by an operator.

[0104] The suction pipe 101 includes an upstream suction inlet 102 and a downstream end 103. The upstream suction inlet 102 is intended to be brought into the vicinity of a region within which it is desired to detect a leak. For example, an operator can handle the suction pipe to bring it into an area where there is a suspicion of a leak.

[0105] In the example illustrated, the leak comes from a pipe 200 and it is represented by an arrow 201 which illustrates the stream of methane which escapes from the pipe 200. The upstream suction inlet is therefore brought to a short distance from the leak, for example a distance less than 50 centimeters or even less than 10 centimeters.

[0106] The suction pipe 101 is flared at the upstream suction inlet 102 to facilitate the placement of the suction pipe in the vicinity of the leak.

[0107] The device 100 is equipped with a ventilation apparatus of the Venturi effect type, which includes an annular injector 104 formed by a pipe portion concentric with the suction pipe 101 extending into the suction pipe from the upstream suction inlet 102 to the end of the flared portion of the suction pipe. Thus, the annular injector 104 injects a gas called motive gas into a constriction of the suction pipe located between the flared portion and the rest of the suction pipe, and oriented downstream of the suction pipe.

[0108] The disclosure is nevertheless in no way limited to the annular injectors, any injector opening out into a constriction of the suction pipe, placed in the vicinity of the upstream suction inlet and oriented downstream of the suction pipe, can be used.

[0109] A stream of motive gas 105 is injected by means of the annular injector 104. The elements placed upstream in the supply chain supplying this motive gas will be described in more detail with reference to FIG. 2.

[0110] This injection of motive gas sets a large air mass in motion, which generates a depression in front of the upstream suction inlet of the pipi. In this way, a suction is obtained.

[0111] The geometry of the suction pipe, its dimensions and the flow rate of the motive gas injection are configured to cause this suction, with a flow rate greater than 300 m.sup.3. As an indication, the apparatus marketed by the French company LACAYELLE SAS under the trade name VENTU 2450 can be used.

[0112] In addition to the methane stream 201, fresh air is also suctioned into a stream represented by the arrows 202.

[0113] Although this is optional, a mixer 106 is used here downstream of the suction inlet 102 to mix the methane stream 201 with the fresh air stream 202. The mixer 106 can be a static mixer.

[0114] A mixed stream 107 which circulates downstream of the suction pipe is thus obtained.

[0115] The methane can then be detected in this mixed air stream, for example by means of a sampling member, here a tube 108 which extends into the suction pipe downstream of the mixer and which is fluidly connected to a detector 109.

[0116] Here, the detector 109 is a Herriott cell infrared absorption detector or a semiconductor detector, and it delivers a concentration of methane contained in the mixed stream 107 with an accuracy of the order of 5 PPM.

[0117] As explained above, the disclosure finds application in the detection of leaks other than methane. In the following table, examples of the type of sensors matched with the detected molecules and their sensitivity threshold can be read:

TABLE-US-00001 TABLE 1 Coupling to the Sensitivity threshold suctioning member Detector type Detected molecule (order of magnitude) Suitable for high PID COV 1 ppm dilutions FID organic compound 1 ppm Herriot-type IR cells Methane 1 ppm Semiconductor (2) Any type 10 ppm OPLS to QCL source (1) Methane 5 to 10 ppb Less suitable but Electrochemical cell Tout type 300 ppm possible if little Catalytic Filament Fuels diluted semiconductor (2) Tout type IR Detection Methane, CO2 Katharometer All types, but particularly molecules with high thermal conductivity (He, H2, etc.)

[0118] The detectors that are suitable for using a tank, such as the RES tank described below, are well suitable for little diluted mixtures.

[0119] Although this is optional, the device 100 is also equipped with a CALC calculator of a leak flow rate from the concentration delivered by the detector 109.

[0120] The mixed stream 107 is obtained by mixing the methane stream 201, the fresh air stream 202 and the motive gas stream 105. That being said, it has been observed by the inventors of the present disclosure that the contribution of the motive gas stream is negligible and that the following relation applies to determine the flow rate of the methane leak:

Q.sub.leak=Q.sub.suction[CH.sub.4].sub.detector  [Math]

[0121] With Q.sub.leak the flow rate of the methane leak, Q.sub.suction the suction flow rate, and [CH4].sub.detector the methane concentration measured by the detector.

[0122] Possibly, a calibration step can allow verifying this relation.

[0123] The suction flow rate can be either known because it is provided by the manufacturer of the suction apparatus, or calculated from the dimensions of the suction pipe and the flow rate associated with the additional gas stream, or measured by a flow rate sensor.

[0124] Alternatively, the value of the suction flow rate can be deduced from a calibration curve obtained by observing different known leak flow rates.

[0125] Optionally, the computer CALC is equipped with a display allowing the calculated value of the leak flow rate to be displayed.

[0126] FIG. 2 represents a device similar to that of FIG. 1 with the elements necessary for the operation of the Venturi effect ventilation apparatus. The device of FIG. 2 differs from that of FIG. 1 in that it is provided with an injector 104′ which opens out in the center of the suction pipe.

[0127] In this figure, it can be seen that the injector 104′ is connected to a first low-pressure valve 110 which allows monitoring the operation of the suction apparatus. Upstream of this low-pressure valve, a cylinder 111 containing pressurized motive gas (for example air, carbon dioxide, or dinitrogen) has been connected. This cylinder is connected to the low-pressure valve by means of a tube 112, a regulator 113 adapted for the lower pressure at which it is desired to release the additional gas and a high-pressure valve 114.

[0128] It is noted that these elements are pneumatic and therefore easily compatible with the ATEX standard. Furthermore, the elements 110 to 114 may or may not be included in the device 100.

[0129] FIG. 3 represents a device 100′ which differs from that of FIGS. 1 and 2 in that it does not include a Venturi effect ventilation apparatus.

[0130] The elements represented in FIG. 3 and which bear the same references as those of FIGS. 1 and 2 are identical.

[0131] The ventilation apparatus of the device 100′ includes an axial fan 120. It can be noted that it is also possible to use a radial fan.

[0132] The axial fan is here an electric machine capable of driving in rotation a paddle wheel configured to cause, during its rotation, a suction with a flow rate greater than 300 m.sup.3/H.

[0133] This axial fan is supplied with electrical energy by a battery 121 of the device 100′. The battery 121 and the turbine 100 are preferably compatible with the ATEX standard.

[0134] Furthermore, the device of FIG. 3 is not equipped with a detector but with a tank RES receiving gas from the sample tube 108. This tank can be initially empty and be filled when the apparatus is used. The device 100′ is therefore a sampling device which allows implementing a quantitative detection.

[0135] The tank RES can be provided with a valve to be transported and allow the analysis of the gas it contains subsequently, for example in a laboratory. This embodiment allows implementing analyzes by chromatograph, for example.

[0136] Obtaining a flow rate for the leak will also depend on how long the tank has received gas.

[0137] FIG. 4 shows the device 100 of FIG. 1 in a configuration where it is further equipped with a skirt 130 having a diameter greater than that of the suction pipe, connected to the upstream suction inlet of the pipe, and flexible. This skirt allows surrounding a region in which a leak is located to limit the influence of external parameters such as the wind.

[0138] A flange can also be used instead of the skirt. The flange and the skirt further have the advantage of reinforcing the suction in front of the upstream suction inlet.

[0139] FIG. 5A represents a sample tube 108′ that can be mounted inside the suction pipe 101, as represented in FIG. 5B.

[0140] The sample tube 108′ can recover part of the mixed stream 107 described above to supply a detector such as the detector 109.

[0141] Here, the sample tube has the shape of a ring equipped, on its face facing the upstream suction inlet of the suction pipe 101, with a plurality of orifices OR′ evenly distributed and in which the mixed stream can penetrate.

[0142] The use of a plurality of orifices allows compensating for any lack of homogeneity of the mixed stream 107.

[0143] FIG. 6A represents another example of a sample tube, here a trident-shaped sample tube with tips configured to be arranged in the general direction of the suction pipe 101 (FIG. 6B), with orifices OR″ at the ends of the tips that face the upstream suction inlet of the suction pipe 101.

[0144] This configuration also allows compensating for a lack of homogeneity of the mixed stream 107.

[0145] The devices described above allow speeding up 10 to 50 times the leak detection and gas leak quantification operations.

[0146] Also, apparatuses using the Venturi effect have been made and have presented suction flow rates of the order of 2,450 m.sup.3/H, with good linearity observed with respect to the suction flow rate, and a characteristic measurement time of 20 seconds. In fact, the measurements are well repeatable with a coefficient of variation of less than 10% over a wide range of flow rates.

[0147] Furthermore, Venturi effect devices have been made with a mass of the order of 17 kilograms, including cylinders of compressed air. The devices according to the disclosure can therefore be completely handled.