JPH03199938A - Inspecting method for leakage of liquid - Google Patents

Abstract

PURPOSE:To make it possible to detect leakage of liquid easily by adding a minute amount of a fluorescent material into the liquid, and applying light to it. CONSTITUTION:Lipophilic fluorescent coloring matter as a fluorescent material which can be dissolved or decomposed is added into engine oil in an object (engine) 1 under inspection, and a driving test is performed. The object 1 under inspection is put into a dark room 2, and external light is shielded. When a light source 3 is lit, the fluorescent coloring matter is excited. When leakage of liquid is present, only the wave length of fluorescence from the fluorescent coloring matter is detected by the use of an image sensing device 4 through a filter, and the image is formed and displayed on a monitoring TV 5 as a luminescent spot 6. When there is no luminescent spot 6, there is no leakage of liquid. Therefore, an expensive large apparatus is not required, and the inspection accuracy is high. When the fluorescent coloring matter leaks out of the leaking part, the fluorescence is generated at the first time. As long as the leakage is not stopped, the fluorescent coloring matter continues to leak, and the intensity of the fluorescence increases with time, and the leakage of liquid can be easily identified.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a method for inspecting liquid leaks from automobile fuel tanks, engines, liquid delivery pipes, and the like.

"Prior Art" Conventionally, there have been the following methods for this type of liquid leakage test.

(1) A method in which the test object, a tank, is sealed and submerged in a water tank, and the presence or absence of bubbles is visually checked.

(2) A method in which high-pressure air is injected into a tank, which is the object to be inspected, and the tank is sealed, and leaks are detected from pressure changes over a unit time.

(3) A tank as an object to be inspected is placed in an inspection chamber, and Freon gas and Yariram gas are filled from outside the chamber into the tank to be inspected via a port, and then the inside of the chamber is evacuated. A method of detecting tank leaks by measuring the concentration of gas leaking from inside the tank to be inspected into the chamber in this state.

"Problems to be Solved by the Invention" The method (1) described above had poor detection accuracy, such as overlooking small bubbles and limitations in visual inspection.

Although the method (2) has higher accuracy than the method (1), there is a problem in that the pressure change to be measured is influenced by the temperature and humidity during the work and varies. The method (3) has a measurement accuracy about 100 times higher than the method (1) using a water tank, and is not affected by working temperature and humidity like the method (2) that measures pressure changes. It also has the characteristic of short inspection time. However, this method (3) has the disadvantage that it requires a large inspection chamber, a vacuum device, a gas sealing device, etc., making the entire device large and extremely expensive.

An object of the present invention is to obtain an inspection method that allows accurate measurement in a short time using simple equipment.

[Means for Solving the Problems] The present invention includes a liquid contained in an object to be inspected, in which a fluorescent substance that can be dissolved or dispersed is added to the liquid, and the liquid of the object to be inspected is 3- This is a liquid leakage inspection method characterized in that the inspection site is irradiated with light capable of exciting the fluorescent substance and fluorescence is measured.

"Operation" When a gasoline engine oil is contained in an oil tank as an object to be inspected, a lipophilic fluorescent substance is added to the gasoline engine oil. The amount added should be extremely small (for example, 0.1% or less) so as not to have any adverse effect on the properties of gasoline engine oil.

In this state, light that can excite fluorescent molecules is irradiated to the area where leakage in the tank is to be detected. The presence or absence of fluorescence is detected visually or by using various photodetectors with filters interposed.

"Example" Hereinafter, one embodiment of the present invention will be described based on the drawings.

There are no restrictions on the volume, shape, material, etc. of the object to be inspected as long as it does not transmit the light irradiated to detect fluorescence.

Specifically, it may be a fuel tank, oil tank, or engine of a car or motorcycle, or a heater,
Kerosene cans, drums, etc. of fuel equipment may also be used.

Furthermore, it may be an oil pipe for sending liquid, a pipe for sending cooling water, or the like. Further, the liquid to be accommodated may be any liquid such as gasoline (hydrocarbon), engine oil, or water.

The fluorescent substance added to the liquid is selected to be suitable for the liquid contained therein. Particularly important in this selection is the solubility or dispersion of the fluorescent substance in the liquid. That is, the fluorescent substance does not necessarily need to be completely dissolved, and may be in a uniformly dispersed state. Therefore, it is necessary to have excellent lipophilicity to detect leaks of gasoline or engine oil, and it is necessary to have excellent hydrophilicity to detect leaks of water. In addition, it is also required that it not affect the properties of the liquid and be inexpensive. The amount added may be extremely small (for example, 0.1% or less). This is because the detection of fluorescent substances is currently extremely sensitive due to advances in ultratrace analysis technology. The effect of the fluorescent substance on the liquid can be ignored due to the addition of an extremely small amount.

Liquid leakage from a test object is often caused by the weight of the liquid or capillary action, but in order to detect leaks in a shorter time, it is desirable to apply diffused air pressure to the liquid as external pressure.

Next, the object to be inspected is placed in a dark room and irradiated with a light source. Basically, this light source may be any light that can excite the fluorescent substance to be added. In other words, beam light is suitable for inspecting a specific part of the object to be inspected, such as a small container or a welded part, and light that spreads over a large area is suitable for inspecting a large part of a large container. . For visual inspection, an invisible ultraviolet light source, such as an inexpensive germicidal lamp, is preferred.

The following methods can be considered to examine all parts of the object to be inspected.

The first method is to fix the light source and rotate the object to be inspected.The second method is to fix the object to be inspected and rotate the light source.The third method is to fix the object to be inspected and rotate the object. This method involves installing multiple light sources in a fixed manner. Which one to choose?
This is determined by considering the shape and size of the object to be measured, the part to be inspected, etc.

The simplest method for detecting fluorescence is to visually detect visible fluorescence generated by irradiation with ultraviolet light. However, as a more accurate detection method, by using a filter that has a transmission characteristic that allows only the generated fluorescence to pass through without passing the excitation irradiation light, various photodetectors, specifically photomultiplier tubes, can be used. , image intensifier, infrared sensor,
One-dimensional sensors, two-dimensional sensors, etc. can be used.

Next, an example of inspecting oil leakage of an engine (1) as an object to be inspected will be explained with reference to FIG.

Dimethy/L/ as a lipophilic fluorescent dye in engine oil
adding P OP OP, i.e. 1,4-di-2-(4-methyl-5-phenyloxazoyl)benzene;
Put this into engine (1) and perform a driving test.

This engine (1) is placed in a dark room (2) to block external light, and a light source (3) that excites the fluorescent dye is turned on.

If there is a fluid leak in the engine (1), only the fluorescence wavelength from the fluorescent dye will be detected by the imaging device (4) through a filter and converted into an image, and the bright spot (6) will be displayed on the monitor TV (5).
). If there is no bright spot (6), there is no leakage.

It is assumed that the excitation light from the light source (3) has a peak at 365 nm as shown in FIG. 2(A). When the liquid is gasoline engine oil, the luminescence intensity is low as shown in CB in Figure 2 unless a fluorescent dye is added.

Therefore, when 0.05 wt% of dimethyl popop is added, a peak with a high fluorescence intensity several times or more is obtained at about 470 nm, as shown in FIG. 2(C).

In addition, in the case of diesel engine oil, the luminescence intensity is extremely low as shown in Figure 3 (D) if no fluorescent dye is added, but when 0.05 wt% of dimethyl popop is added, the luminescence intensity is about 480 nm as shown in Figure 3 (E). A peak with a fluorescence intensity of 10 times or more can be obtained. Therefore, dimethyl popop as a fluorescent dye is effective in detecting liquid leakage.

Note that, as is clear from FIG. 2 (B) and FIG. 3 (D), a slight peak of luminescence is observed in response to specific light even without adding a fluorescent dye. This is because engine oil contains organic or inorganic luminescent substances such as antioxidants, anti-wear agents, viscosity index improvers, detergent dispersants, and rust preventive agents as additives. Therefore, among these additives, those that have properties as fluorescent dyes,
The light intensity can also be increased by containing a large amount within a range that does not adversely affect the original characteristics.

"Effects of the Invention" As described above, according to the present invention, liquid leakage can be detected very easily by adding a trace amount of a fluorescent substance to a liquid and irradiating the liquid with light.

Moreover, not only does it not require expensive and large equipment, but also the inspection accuracy is extremely high. This is because the present invention skillfully utilizes the characteristics of leakage itself. That is,
Fluorescence occurs for the first time when a fluorescent substance leaks from a leakage site in a test object such as a container.Furthermore, unless the leakage stops, the fluorescent substance will continue to leak, so if there is a leak, the fluorescence intensity will increase over time. Increased fluorescence is very easily distinguished from background fluorescence due to causes other than leakage.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an apparatus for implementing the liquid leakage inspection method according to the present invention, FIG. 2 is a characteristic diagram of gasoline engine oil, and FIGS. 3 and 3 are characteristic diagrams of diesel engine oil. (1)...Engine, (2)...Darkroom, (3)...
・Light source, (4)...imaging device, (5)...monitor T
V, (6)... Bright spot.

Claims (4)

[Claims] (1) In an object to be inspected containing a liquid, a soluble or dispersible fluorescent substance is added to the liquid, and the fluorescent substance is applied to the leakage inspection site of the object to be inspected. A liquid leakage inspection method characterized by measuring fluorescence by irradiating light that can excite a substance. (2) The liquid leakage inspection method according to claim (1), wherein a lipophilic fluorescent substance is added to engine oil or fuel as the liquid contained in the object to be inspected. (3) Cooling water as a liquid contained in the inspected object,
2. The liquid leakage testing method according to claim 1, wherein a hydrophilic fluorescent substance is added. (4) Claims (1) and (2) in which fluorescence is detected by visual observation or by an optical sensor such as a photomultiplier tube, an image intensifier tube, an infrared sensor, a one-dimensional sensor, or a two-dimensional sensor.
Or the liquid leakage inspection method described in (3).