JPS626134A - Leak detector for vessel - Google Patents

Abstract

PURPOSE:To inspect a leak of a vessel from far away under noncontact state by sealing tracer gas between an inner shell and an outer shell and scanning the surface of the inner shell by laser beams with wavelength absorbed and wavelength not absorbed with the tracer gas. CONSTITUTION:A mount 14 storing a scanning mechanism and a laser beams transmitting and receiving part 13 are provided at the central position of the bottom face 11 in the vessel 1 to be measured. Then, a compressor 8 is fitted to a gas introduction port 6 of the vessel 1 via a valve 7, and the valves 9 and 7 are opened to put the freon gas 5 into a clearance 4 between the outer shell 2 and the inner shell 3 with the pressure higher than the outside atmospheric pressure. Then, the laser beams 12 with wavelength absorbed and wavelength not absorbed with the gas 5 are scanned and irradiated along a welded zone of the inner shell 3 from the transmitting and receiving part 13 and the difference of the photodetecting strength between the laser beams with two wavelengths is taken, by which the gas leak is inspected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a container leakage detection device using a differential absorption type radar gas detection device.

[Conventional technology] Oil tank installed at petrochemical complex 1-.

Large containers such as gas tanks and large pressure vessels installed in factories are manufactured by welding many steel plates together.

In addition, in order to ensure the safety of the container, it is often constructed with a double structure consisting of an outer shell and an inner shell.

Then, the welded parts of the outer shell and inner shell of these double-structured containers are not completely welded, and cracks occur due to insufficient entrainment, etc., and the contents inside the container leak to the outside. In order to prevent this from happening, we conduct leakage tests on containers in advance.

An ammonia leak test is one of the leak test methods. In this test, a paint that develops or changes color by reacting with ammonia is applied to, for example, the welded portion of the outer surface of the container to be measured, and ammonia gas at a higher pressure than the outside air is sealed inside. If ammonia gas leaks out to the outer surface due to cracks or the like in the weld, the paint develops or changes color, making it possible to identify the leakage location.

There is also another leak testing method, the halogen detector method.

In this halogen detector method, the inside of the container to be measured is filled with a gas of halogen or a compound containing halogen, and a detection probe is sequentially guided to the welded portion on the outer surface of the container to be measured. When leaked halogen is detected, the anode and cathode open currents increase. Helium detectors also operate on almost the same principle.

[Problems to be Solved by the Invention] However, each of the leakage detection methods described above has the following problems. In other words, with the ammonia leak method, if the container to be measured is large, such as an oil tank or a gas tank, it is necessary to build a sunny foothold in order to apply paint to detect ammonia on the welded parts. Furthermore, once the inspection is completed, it is necessary to remove the paint. Therefore, there is a problem in that the efficiency of leakage detection work is significantly reduced.

In addition, in the leak detection method using a halogen detector,
Since it is necessary to stroke the welded part etc. with a detection probe, it is necessary to build a stable foothold as in the ammonia leak method described above. Furthermore, in this halogen detector, it is necessary to heat the anode disposed within the detection probe to, for example, 300 to 800°C. Therefore, it is inconvenient for safety to use this halogen detector in work sites where special precautions against fire are required, such as in gas tanks.

The present invention was made based on these circumstances, and its purpose is to detect even large containers from a distance without building a foothold by using a differential absorption radar gas detection device. To provide a container leakage detection device that can easily perform a leakage test without contact.

[Means for Solving the Problems] The container leak detection device of the present invention detects the inner shell and outer shell of the container to be measured, which is formed into an eight-layered structure consisting of an inner shell and an outer shell by a tracer gas supply device. A tracer gas is sealed at a pressure higher than the outside pressure in the gap between the radar beam and the tracer. A differential absorption radar gas detection device is provided that detects the presence of 1-racer gas using a radar beam with a normal wavelength that is not absorbed by gas, and a scanning mechanism is used to detect the direction of the radar beam irradiation of the differential absorption radar gas detection device. is scanned on the inner shell surface.

[Function] With the container leak detection device configured in this way, if a leak hole occurs due to a crack or the like in the inner shell of the container to be measured, which is formed in a double structure, the tracer gas supply device can detect the leakage hole. The supplied tracer gas leaks through the leak hole.

When tracer gas leaks to the inner shell surface, this tracer gas is detected at some point by a differential absorption radar gas detection device in which the direction of radar beam irradiation is scanned over the inner shell surface by a scanning mechanism.

[Example] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic cross-sectional view showing a container leakage detection device according to an embodiment. In the figure, 1 is a container to be measured, such as a large tank formed by welding a large number of steel plates. The container 1 has a double structure of an outer shell 2 and an inner shell 3 to ensure safety. Then, this container to be measured 1
The gap 4 between the outer shell 2 and the inner shell 3 is
A gas inlet 6 for injecting 7 Leon gas 5 as a tracer gas is provided at the lower part of the side wall. A compressor 8 is connected to the gas inlet 6 via a valve 7, and a gas cylinder 10 filled with Freon gas 5 is further connected to the compressor 8 via a valve 9.

Freon gas (Freon 12) is used as a tracer gas.
The reason why Freon gas (CCl2F2) is used is that Freon gas has excellent properties such as nonflammability, nonexplosion, and nontoxicity.

A radar beam transmitter/receiver 13 for transmitting and receiving radar light $112 of the differential absorption type radar gas detection device is arranged at the center position of the bottom surface 11 of the inner shell 3 in the container 1 to be measured. A scanning mechanism housed in the stand 14 scans the irradiation direction of the radar beam 12 on the surface of the inner shell 3.

Note that 15 in the figure indicates a leakage hole formed in a welded portion of the inner shell 3, for example. During a leakage test, the gap 4 between the outer shell 2 and the inner shell 3 is filled with freon gas 5 at a pressure higher than the outside pressure using the compressor 8, so that the freon gas 5 enters the container 1 to be measured from the leak hole 15. leak. In addition, when the leakage detection work is completed, the 7 Leon gas 5 in the gap 4 is recovered,
Gas inlet 6 is closed. Roughly speaking, the radar beam transmitting/receiving unit 13 and the mounting table 14 are carried out through an entrance/exit which is not shown.

FIG. 2 is a block diagram showing a control section that drives and controls the differential absorption type radar gas detection device and the scanning mechanism. 2 in the diagram
Reference numeral 1 denotes a CPU (central processing unit) that executes arithmetic processing, etc. on various data input from the radar beam transmitter/receiver 13, etc.;
A storage section 23 formed of a RAM (Random Access Memory) or the like that stores variable data such as scanning information inputted from the outside. It controls an interface 25 for sending display data to a display section 24 formed by a CRT display tube, and an interface 27 for inputting data from a teletype 26 into which scanning information is input.

In addition, the CPLJ 21 drives the scanning mechanism 28 housed in the stand 14 via the output interface 29 to attach the radar beam transmitting/receiving section 13, and also connects the laser beam emitting section 30 of the radar beam transmitting/receiving section 13 via the output interface 31. and sends out a laser emission command. Also, CPU
21 is connected to an input interface 32 into which data from the radar beam transmitter/receiver 13 is input.

In the radar beam transmitting/receiving section 13, a laser emitting section 3
0 is composed of two sets of semiconductor laser emitting devices that emit a laser beam having a wavelength λa and a laser beam having a wavelength λb when a laser emission command is input from the output interface 31. The two sets of emitted radar beams 12 are output to the outside via the optical mechanism 33. The particles with the wavelength λa are tracer gas molecules.

This value is determined by the fact that an atom has a property of absorbing light (electromagnetic waves) that is unique to that molecule or atom. In the example in which Freon gas 5 is used as the tracer gas, the wavelength λa is 10.86-10.86 cm in the infrared region. is set to . Therefore, when the laser beam 12 with the wavelength λa collides with the 7 Leon gas 5, it is absorbed by the 7 Leon gas 5, and the intensity of the light beam decreases. On the other hand, the value of the wavelength λb is set to a value that is not affected by the molecules and atoms of the Freon gas 5, and is set to a value that is slightly shifted from the absorbed wavelength λa. Then, the radar beam 12 with the wavelength λb is used as a reference laser beam for the radar beam 12 with the wavelength λa to be absorbed.

Radar light I output from the optical mechanism 33 of the radar beam transmitter/receiver 13! 12 is reflected on the surface of the inner shell 3 of the container 1 to be measured and is again input to the optical mechanism 33 of the radar beam transmitting/receiving section 13. Radar beam 12 input to this optical mechanism 33
is converted into an electrical signal by a photoelectric conversion element 35 made of, for example, a phototransistor via an optical filter 34 that allows wavelength λa to pass. This electrical signal is then input to one signal input terminal of the divider 37 via the amplifier 36.

Also, radar light 1!1l12 input to optical t11M33
is converted into an electrical signal by a charging conversion element 39 having the same configuration as the photoelectric conversion element 35 via an optical filter 38 that passes the wavelength λb, and is inputted to the other signal input terminal of the divider 37 via an amplifier 40. Ru. - Each electric signal corresponding to wavelength λa and wavelength λb inputted to the divider 37 is converted into digital data DA and Do by an A/D converter, respectively.
is converted to Then, DA/DolI is determined.

This divided value D A / D s is inputted to the CPU 21 via the input ink face 32 as a gas detection data value and displayed on the display section 24 .

Next, the operation of the container leak detection device configured as described above will be explained.

First, the scanning mechanism 28 is housed in the center of the bottom surface 11 of the container 1 to be measured, and the stand 14 and the radar beam transmitting/receiving section 13 are installed as shown in FIG. Then, as shown in the figure, a compressor 8 is attached to the gas inlet 6 of the container 1 to be measured via a valve 7. Then valves 9, 7
, start the compressor 8 and compress the outer shell 2 and inner shell 3.
Freon gas 5 is injected into the gap 4 between the two until a predetermined pressure higher than the outside pressure is reached. When the injection is completed, valve 7 is closed.

Next, the scanning information punched in advance on the tape is transferred to the teletype 2.
6, this scan information is temporarily stored in the storage unit 23. Note that this scanning information is transmitted to the radar beam transmitting/receiving section 13.
This is data for sequentially moving the irradiation direction of the radar beam 12 outputted from, for example, along the welded part formed in the inner shell 3, and is usually created on a computer at the time of designing the vessel 1 to be measured. .

Then, a differential absorption type laser gas detection device and a scanning mechanism 28
When a start command is input to the radar beam transmitter/receiver 13, two types of radar beams 12 with wavelengths λa and λb are irradiated onto the three surfaces of the inner shell, and the scanning mechanism is activated according to the scanning information stored in the storage unit 23. 28 is driven. As a result, the irradiation position of the radar light 1i112 on the inner shell 3 surface sequentially moves along the welded portion. At the same time, position data indicating the laser irradiation position is sequentially displayed on the display unit 24.

If the leakage hole 15 does not exist at the irradiation position of the radar beam 12 on the inner shell 3 surface, the wavelength λ of the radar beam 12
Since the light beam a is not absorbed, the intensity of each laser beam irradiated to each photoelectric conversion element 35, 36 in the radar beam transmitting/receiving section 13 becomes approximately equal. Therefore, each intensity data l1 input to the divider 37 and A/D converted
D.A.

Since Do is also approximately equal, the division value DA/DB input from the divider 37 to the CPtJ 21 via the input interface 32 is approximately 1. Then, it is displayed on the display unit 24 together with the position data of the welded part.

On the other hand, if a leakage hole 15 exists at the irradiation position of the radar beam 12 on the surface of the inner shell 3, the Freon gas 5 sealed in the gap 4 will flow out from the leakage hole 15.
Of these, a light beam with wavelength λa is absorbed by this Freon gas 5. Therefore, the laser beam intensity of the wavelength λa input to the photoelectric conversion element 35 in the radar beam transmitter/receiver 13 is
The intensity is smaller than the laser beam intensity of wavelength λb input to the photoelectric conversion element 36. As a result, from the divider 37 to the CPU 21
The input Salel ratio viI11 [DA/D day is significantly smaller than 1. Therefore, 1 indicates the existence of this leakage hole 15.
The smaller division 1i1DA/Do is displayed on the display unit 23 together with the position data where the leak hole 15 exists.

When the scanning of the welded parts on all surfaces of the inner shell 3 by the radar light 112 is completed, the radar beam transmitting/receiving section 13 and the mounting base 14 are removed, and the 7 Leon gas 5 in the gap 4 is exhausted.

With the container leak detection device configured in this way, leakage holes can be detected by simply scanning the radar beam 12 sequentially over the three surfaces of the inner shell using the radar beam transmitter/receiver 13 disposed on the bottom surface 11 of the container to be measured 1. 15 can be detected. Therefore, unlike conventional detection methods, there is no need to apply tracer gas-reactive paint to the weld or build scaffolding, so leak inspection work can be carried out quickly and easily, greatly improving work efficiency. can.

Note that the differential absorption type laser gas detection device used in the example was also able to detect 0.11 ppb 11 degrees Freon gas.

Furthermore, since Freon gas is used as the tracer gas in the embodiment, work safety can be improved as described above.

Note that the present invention is not limited to the embodiments described above. In the examples, Freon gas was used as the tracer gas, but the tracer gas is not particularly limited to Freon gas, and other tracer gases may be used. In this case, it is necessary to set the wavelength λa corresponding to the molecules and atoms of the tracer gas used.

In addition, in the embodiment, the laser is applied along the welded part of the inner shell 3.
Although the dead light beam 12 is scanned in the above example, it may be scanned over the entire surface of the inner shell 3.

Furthermore, by applying the present invention, leakage tests on the outer surface of the outer shell 2 of the container 1 to be measured can be easily carried out.

[Effects of the Invention] As explained above, according to the present invention, a differential absorption type radar gas detection device scanned by a scanning mechanism is used. Therefore, even if the container is large, a leak test can be easily performed from a distance without contact, without building a scaffold, and the efficiency of the leak test work can be improved.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing a container leakage detection device according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a schematic configuration of the main parts of the same embodiment. 1... Container to be measured, 2... Outer shell, 3... Inner shell, 4
... Gap, 5... Freon gas (tracer gas)
, 6... Gas inlet, 7.9... Valve, 8...
Compressor, 10...Gas cylinder, 11...Bottom surface, 12...Radar beam, 13...Radar beam transmitter/receiver, 14...Mounting stand, 15...Leak hole, 21...
...CPLI, 22...Data bus, 23...Storage unit, 24...Display unit, 25°27...Interface, 26...Teletype, 28...Scanning mechanism,
29.31... Output interface, 30... Laser emission section, 32... Input interface, 33.
...Optical mechanism, 34.38... Optical filter, 35.
39... Photoelectric conversion element, 36.40... Amplifier, 3
7... Divider.

Claims (1)

[Claims] a tracer gas supply device that seals tracer gas at a pressure higher than the external pressure into a gap between the inner shell and the outer shell of a test container formed in a double structure consisting of an inner shell and an outer shell;
A radar beam having a specific wavelength that is absorbed by the tracer gas disposed in the vessel to be measured and flowing out from a leakage portion present in the inner shell, and a radar beam having a normal wavelength that is not absorbed by the tracer gas. A differential absorption type radar gas detection device that detects the presence of the tracer gas using a radar beam, and a scanning mechanism that scans the radar beam irradiation direction of the differential absorption type radar gas detection device on the inner shell surface. Characteristic container leakage detection device.