[0039] figure 1 Describes bulkhead 1, the average temperature of the bulkhead is TM. As indicated by arrow 2, at pressure P, the gas begins to contact the bulkhead 1. If the condensing temperature TC of the gas is higher than the temperature TM, the gas will condense into a liquid or solid precipitate 3 form. According to this mode, the gas releases latent heat after condensation and is transferred to the bulkhead 1. This heat transfer is as indicated by arrow 4, therefore, the local temperature T of the bulkhead 1 will be higher than TM. When the temperature TM, pressure P and the nature of the gas are controllable, the condensation at this time is called forced condensation.
[0040] Such gas may be:
[0041] A single gas whose inherent physical properties match the ideal condensation temperature.
[0042] A mixture composed of non-condensable gas and condensable gas whose concentration can be adjusted to suit the condensation temperature. Specifically, such as figure 2 As shown, a single gas has a condensation temperature of TP. Once it is diluted to a concentration of X% in a non-condensable gas, the gas condensation temperature TC will be lower than TP.
[0043] A mixture of several condensable gases, once combined, an ideal condensation temperature TC is obtained.
[0044] Refer now Figure 3-5 As shown, the principle of using the forced condensation method to detect the cracks of the sub-layer film in the multi-film cabin is explained in detail.
[0045] The cabin body 5 includes a load-bearing structure 6 that provides mechanical rigidity, a main layer film 8 for containing products in the cabin body 5, and a secondary layer film 7 between the main layer film 8 and the load-bearing structure 6, which is located between the main layer film 8 and The space between the secondary film 7 is called the main space 10, and the space between the secondary film 7 and the load-bearing structure 6 is called the secondary space 9.
[0046] The manufacture of the cabin 5 will not be described in detail, because there are many known options for those skilled in the art. For example, the cabin can be a liquefied natural gas cabin manufactured using existing technology. If so, The insulation materials in the main space 10 and the secondary space 9 are existing.
[0047] The cabin 5 also includes an ejector 11 connected to the main space 10 through a pipe 12, an ejector 13 connected to the secondary space 14 through a pipe 14, a cooling device 15 connected to the inside of the cabin 5 through a pipe 16, and a pipe 17 respectively. The inside of the body, the main space 10 and the secondary space 9 are connected to a gas discharge and pressure management device. The following will describe how the above components detect and locate the cracks 18 in the sub-layer film 7.
[0048] According to an embodiment of the present invention, the leak detection method correspondingly includes the following steps: cabin debugging before detection, actual testing, and restoration of the cabin to its original state.
[0049] The cabin debugging before inspection includes:
[0050] The temperature of the main film is adjusted to reach the desired temperature, which can be achieved by using a temperature control device or injecting a liquid coolant into the cabin 5. For example, liquid nitrogen is injected into the cabin 5 through the cooling device 15. In an ideal state, after this step, the temperature of the main layer film is uniform, but due to the difference in temperature stress, the temperature of the main layer film may be slightly different. Therefore, the following refers to the average temperature of the main film TM.
[0051] A neutral gas is injected into the main space 10, the so-called neutral gas refers to a gas that does not condense at the temperature TM, either the gas itself is non-condensable, or the condensation temperature of the gas is lower than TM. This can be done by injecting gas through the ejector 11, or directly connecting the main space with air under air conditions.
[0052] Inject an active gas into the subspace 9. The active gas refers to a gas that can be condensed when the temperature is higher than TM. As explained above, this gas may be a single gas or a mixture. This can be achieved by using The ejector 13 is implemented.
[0053] The three steps can be carried out simultaneously or continuously in any order.
[0054] The detection step also includes: it is convenient to increase the pressure of the active gas in the secondary space 9 inside the cabin, and to detect any hot spots that may appear on the primary membrane 8 inside the cabin.
[0055] Specifically, such as image 3 As shown in detail, if the secondary film 7 has cracks 18, due to the pressure difference between the secondary space 9 and the main space 10, active gas will be injected into the main space 10, as shown by the cloud diagram 19 and the arrow 20.
[0056] Therefore, at the crack 18, the active gas will enter the main space and encounter the main layer film 8 to form condensate 21. In this way, as described above, the active gas transfers heat to the main layer film 8, so the local temperature of the main layer film 8 is higher than TM. By detecting this hot spot 22, it is possible to find the crack 18, for example, by using The internal temperature sensor or the sensor used to detect emissive infrared can detect hot spots 22
[0057] The cabin restoration procedures include:
[0058] Removal of the gas in the main space 10, which can be achieved by using the pipe 17, either by evacuating the space gas and then filling it if necessary, or by filling it with gas to be filled during normal operation of the cabin to clean the space;
[0059] Removal of the active gas in the secondary space 9 can also be achieved by using the pipe 17, either by evacuating the space gas and then filling it if necessary, or by filling it with gas that needs to be filled during normal operation to clean the space;
[0060] Increase the temperature of the main film, which can be achieved by using a temperature control device or by air convection at room temperature.
[0061] The three steps can be carried out simultaneously or continuously in any order.
[0062] A typical embodiment of the present invention is that the neutral gas is nitrogen, and the active gas is a mixture composed of nitrogen and pentane each occupying 50% by volume. Pentane is liquid at normal temperature and pressure, and its vaporization temperature is 36°C, but in the above-mentioned mixture state, its condensation temperature when it condenses to a liquid state drops to about 18°C.
[0063] For example, the cabin body 5 tested is a storage cabin body that carries methane. The main layer membrane 8 of the cabin body is at a normal temperature of 25°C. The interior of the storage cabin body is cooled so that the main layer membrane is at an average temperature of 10°C. , The temperature in the secondary space 9 is higher than 20°C, so the nitrogen/pentane mixture can be injected into the secondary space 9 without the danger of condensation. Next, a pressure difference of a few millibars is generated by pressurizing, and the nitrogen/pentane mixture enters the main space 10 from the crack 18 and condenses after encountering the main layer film 8 to form a hot spot.
[0064] In addition, the required condensation temperature of nitrogen can be adjusted by changing the degree to which nitrogen is diluted in pentane. Therefore, if the room temperature is, for example, 35°C or 10°C, it is possible to detect by adjusting the temperature TM and the degree of nitrogen being diluted .
[0065] In order to do this, the preferred method is that the injector 13 can generate a compound in a desired ratio, for example, Figure 5 As shown, the ejector 13 is equipped with a container 23 for storing carrier gas (nitrogen as described above) and a container 24 for storing compressed gas in liquid form (pentane as described above). The two containers are connected to the distiller 30 through a pipe 25 and a pipe 26 respectively, so that a mixture of the two will be generated in the distiller 30, and the distiller 30 is connected to the secondary space 9 through a pipe 14. The controller 29 controls the concentration of nitrogen to be diluted by adjusting the distiller 30 and the flowmeter 27 and the flowmeter 28 respectively arranged on the pipe 25 and the pipe 26. According to the different condensation temperature you want to achieve, many gases are available. For example, dodecafluoropentane can replace the nitrogen in the previous embodiment at least to some extent, and it is safer to use due to its low flammability.
[0066] An embodiment of the present invention is that the temperature of the main layer of the film is higher than 0°C, and the infrared camera is used to detect hot spots. Preferably, the inside of the film is covered with small water droplets (for example, water vapor is used to sweep the film during the cabin debugging stage) Surface), so that a diffusion layer can be formed, which can greatly reduce the specular reflectivity of the surface. When using an infrared camera to locate hot spots, such a diffusion layer or emulsion coating can improve the local emissivity of the film surface, thereby promoting the measurement effect. .
[0067] Although the present invention is described in conjunction with specific embodiments, it is not limited thereto. The equivalent changes and combinations of the technical solutions of the present invention fall within the protection scope of the present invention.
