JPH0222323B2 - - Google Patents

Description

[Detailed Description of the Invention] <Technical Field> The present invention provides a method for detecting the amount of gas leakage;
Regarding air leakage detector.

<Prior art> One method for evaluating the airtightness of the shell wall of a box-shaped shell is the pressure-time method (pressurized gas is sealed inside the box-shaped shell, and the gas leaking from the shell wall is used to In the method for evaluating the airtightness of a shell wall from the pressure drop inside the shell, an enclosure valve is used as a sealing means to maintain the pressurized state inside the box-shaped shell that is the specimen.

In this sealed valve, it is generally acceptable for the amount of gas leaking from the valve seat to be less than a certain amount due to the nature of the valve.

<Problems to be Solved by the Invention> However, in the conventional pressure-time method, if a small amount of gas leaks from the valve seat of the enclosed valve, the pressure inside the box-shaped shell increases. The change is
Since it is no longer based solely on leakage from the shell wall, there is a problem in that the evaluation of the airtightness of the shell wall of a box-shaped shell differs from the actual situation. Therefore,
When evaluating the airtightness of the shell wall of a box-shaped shell using the above method, it is important to note that the amount of leakage from the valve seat of the enclosed valve as a sealing means affects the airtightness evaluation of the shell wall of the box-shaped shell. In order to correct for the influence of leakage from the valve seat of the sealed valve, and to avoid overlooking a situation in which the amount of leakage from the valve seat of the sealed valve exceeds a certain allowable value, the actual leakage amount is evaluated by evaluating the airtightness of the shell wall. It was desired to grasp the information in parallel with the work.

In the pressure-time method described above, when configuring a device that detects a minute amount of gas leaking from the valve seat of a sealed valve (hereinafter referred to as air leakage amount), a conventionally used flowmeter is used as an air leakage meter. Considering its application as a quantity detector, electromagnetic flowmeter, turbine flowmeter,
Float-type area flowmeters, ventilate tubes with throttle mechanisms, etc. can be listed, but these as well as others are linked to means for detecting minute amounts of air leakage and alerting the permissible limit of air leakage. I haven't found anything that has easy-to-use functions and can be easily applied. In view of these circumstances, the present invention seeks to provide a method and a leakage amount detector for easily detecting the amount of air leakage from a sealed valve.

<Means for Solving the Problems> The gist of the method of the present invention is to supply compressed gas to the inner bottom of a bottomed container that has an upwardly flared portion at the top that stores a liquid and opens the upper part to the atmosphere. The gas leaking from the valve seat of the enclosed valve sealed in the box-shaped shell (hereinafter, the gas leaking from the valve seat may simply be referred to as leakage gas) is released into the liquid to generate an upward bubble flow. The amount of leakage air is detected from the position of the float body, which floats up and down in the liquid of the upwardly expanding end portion and remains stationary in balance, corresponding to the amount of floating fluid force caused by this upward bubble flow. Then, the alarm means is activated to issue an alarm when the leakage amount is within the permissible limit.

In addition, the gist of the configuration of a leakage amount detector suitable for implementing this method is that a bottomed container with an upwardly flared portion at the top that is open to the atmosphere is arranged to store liquid, and a containment valve is closed. A leakage conduit for guiding gas leaking from the valve seat is placed in the center of the inner bottom of the bottomed container and opens upward, and a cylindrical guide member is placed in the liquid at the bottom of the bottomed container to guide the leakage gas. Forming a flow path that guides the upward bubble flow caused by air and the accompanying liquid flow,
A float structure consisting of a float body and a central axis is
It is arranged so that it can float and sink in the liquid in the upwardly expanding end, and is equipped with an air leakage indicator section that operates in conjunction with the float body, and an air leakage amount permissible limit alarm section. .

<Embodiments> (Method of the Invention, Structure of Apparatus) Hereinafter, a method for detecting the amount of air leakage and an air leakage amount detector for carrying out the present invention will be described using examples and application examples.

Embodiment FIG. 1 is a diagram showing an embodiment of the leakage amount detector according to the present invention. The leakage amount detector 1 includes a bottomed container 2 having an upwardly flared portion at the top that is open to the atmosphere, a cylindrical guide member 3, a float component 4, a guide 5, and an air leakage amount indicator 6. , an air leakage amount permissible limit alarm section 32, and an air leakage conduit 9.

A bottomed container 2 (hereinafter sometimes simply referred to as a bottomed container 2) having an upwardly flared portion (hereinafter sometimes simply referred to as an upwardly flared portion) at the top that is open to the atmosphere has, for example, The plastic material has a circular horizontal cross section, and the part below the approximately central part of the axial length is cylindrical with a bottomed bottom, and the part above the central part is cylindrical and has an inner diameter that widens upward. The liquid 12 is stored in an enlarged shape with an opening at the upper end and a predetermined liquid level 11 in the upwardly flared portion.

The cylindrical guide member 3 is made of a plastic material, for example, and has a float body whose inner diameter expands upward from the approximate center of its axial length to form a float body 10, which will be described later. It is formed in a shape similar to and larger than the conical surface of the downward conical part 13, and the lower side from the center part is formed in a cylindrical shape, and the upper and lower ends of the cylindrical guide member 3 consisting of the above are respectively The outer shell is made smaller than the inner shell of the cylindrical portion of the bottomed container 2 in order to form a circulation path 14 for the liquid 12, which will be described later.

This cylindrical guide member 3 has a liquid 1 that circulates between the bottom of the bottomed container 2 and the lower end of the cylindrical guide member 3.
2 are arranged with a required gap so as to be able to flow, and are arranged so as to share the axis, and are fixed to the bottomed container 2 by a support member 19. By arranging the cylindrical guide member 3 described above,
A circulation path 14 for the liquid 12 that has risen on the inner side of the cylindrical guide member 3 is formed on the outer side of the cylindrical guide member 3 in the bottomed container 2 .

Note that a flow path can be provided by drilling an appropriate notch having a required cross-sectional area on the periphery of the lower end of the cylindrical guide member 3 so that the liquid 12 can circulate. There is no need to provide the above-mentioned gap with the bottom of the bottomed container 2.

Next, the float structure 4 will be described.

The float structure 4 mainly includes a float main body 10 that receives buoyant force from the liquid 12 and a buoyant fluid force from an upward bubble flow, and a leakage amount indicating means 1 to be described later.
8, as well as a central shaft 16 to which the actuator 8 can be attached.
It consists of.

The float main body 10 of this embodiment is formed in a downward conical shape with a flange-like part attached to the bottom side of the cone, which can be brought into contact with the rising bubble flow.

That is, the specific gravity of the brim portion is lighter than the specific gravity of the liquid 12. For example, a downward truncated cone is formed of foamed plastic material, and its surface is covered with a liquid-tight plastic film, thereby forming the downward truncated cone 15 as the brim-like portion of the float body. (Hereinafter, the downward truncated cone 15 as the brim-like part of the float body will be simply referred to as the downward truncated cone 15.
It is sometimes abbreviated as. ) Next, the downward conical portion 13 of the float body has a bottom diameter smaller than the diameter of the truncated surface 17 of the downward truncated cone 15 (hereinafter, the downward conical portion 13 of the float body is simply referred to as the downward conical portion). 13) is formed in the same manner as the downward truncated cone 15.

Downward truncated cone 1 formed in this way
The truncated surface 17 of No. 5 and the bottom surface of the downward conical portion 13 are joined and integrated by sharing the center of each of these surfaces, and as a result, the downward truncated cone 15 is on the upper side and the downward conical portion 13 is on the lower side. The floater main body 10 which is to be used as a side is formed, and the details of its formation procedure will be described next.

so that the outer diameter of the bottom surface of the downward truncated cone 15 can pass through the starting position of the upwardly flared part of the bottomed container 2 along the axial direction; The diameter of the bottom surface of the downward truncated cone 15 is made slightly smaller, and the truncated surface 1
7 has a diameter that can be placed on the upper end of the cylindrical guide member 3, and the diameter of the bottom of the downward conical portion 13 is as follows:
The annular portion 3 is made smaller in diameter than the inner diameter of the upper end of the cylindrical guide member 3, and has a size such that the upward bubble flow due to leakage comes into contact with it and can receive the floating fluid force as described later.
0 on the truncated surface 17, and when the truncated surface 17 rests on the upper end of the cylindrical guide member 3, the bottom surface of the downward truncated cone 15 is at the starting position of the upwardly flared portion of the bottomed container 2. The height of the downward truncated cone 15 is set so as to coincide with the horizontal cross-sectional position passing through the cone 15, and the cone 15 is formed as described above.

A center shaft 16 is vertically disposed at the center position of the bottom surface of the downward truncated cone 15 as a brim-shaped portion of the float main body 10 formed as described above, sharing the axis of both, and as a result of the above, the float structure is completed. It constitutes body 4, but
In a state where the float body 10 is seated on the upper end of the cylindrical guide member 3, a leakage amount indicating means 18 (described later) is installed at a predetermined position of the portion where the upper end of the central shaft 16 protrudes above the liquid level 11. , the actuator 8, the guide tool 5, and the like can be attached to the central axis 16 in length.

The float structure 4 configured as described above includes:
Furthermore, in order to perform the following functions, physical conditions such as its own apparent specific gravity in liquid and the shape and dimensions of the float main body 10 are defined and provided. That is, when there is no rising bubble flow due to air leakage in a state in which the air leakage amount indicating means 18 and the actuator 8 are attached to the float assembly 4 as described later,
The floater structure 4 has an apparent specific gravity large enough to sink in the liquid 12, and also has a downward truncated cone 1 that absorbs a floating fluid force of a predetermined magnitude or more due to the upward bubble flow.
When the float main body 10 having a diameter of 5 is received, the apparent specific gravity to liquid is such that it floats from above the upper end of the cylindrical guide member 3 into the liquid 12 of the upwardly expanding end portion of the bottomed container 2. In addition, the downward truncated cone 15 of the float main body 10 is given a shape and dimension capable of receiving a levitation fluid force of a predetermined magnitude or more due to the upward bubble flow. As described above, when the floater structure 4 sinks, the truncated surface 17 of the floater body 10 is shaped and dimensioned so that it can temporarily rest on the upper end of the cylindrical guide member 3, and as it floats, In response to the enlargement of the gap between the bottom peripheral edge of the downward truncated cone 15 of the float body 10 and the inner shell of the upwardly flared end portion, the float body 10
The outer shape and dimensions of the float main body 10 are provided so that it can stand balancedly at a predetermined position in the liquid 12 where the float is below the liquid level 11.

Next, the float structure 4 is placed in the liquid 12 in the upwardly flared portion, and the air leakage amount is adjusted to an allowable amount from the position where the float body 10 is seated on the upper end of the cylindrical guide member 3. A guide tool 5 is provided to hold and guide the center shaft 16 so as to be able to float and sink along the axis of the upwardly expanding end until the limit is reached and the balance stops.

The guide 5 is disposed above the liquid level 11 and fixed to the bottomed container 2.

When the float main body 10 floats in the liquid 12 under the buoyant fluid force caused by the upward bubble flow, the inner shell of the upwardly flared part of the bottomed container 2 has a bottom peripheral edge of the downward truncated cone 15 and an upwardly facing edge. A gap change occurs between the float body 10 and the inner shell of the flared-end portion, and the float body 10 provides an upward slope of the flare-shaped portion so that it can balance and stand still at a predetermined position in response to the size of the leakage amount. The upwardly flared portion is sized and formed to provide the necessary range for equilibrium.

The leakage amount display section 6 is composed of a leakage amount indicating means 18 and an indicator scale section 20, and is disposed so as to be interlocked with the float structure 4.

That is, the leakage amount indicating means 18 is attached to a portion where the central shaft 16 protrudes from the liquid level 11, and the indicating scale portion 20 indicates that the float member 4 is balanced and stationary in accordance with the magnitude of the rising bubble flow. A scale is attached to the position indicated by the leakage amount indicating means 18 when the leakage amount indicating means 18 is in use. More specifically, in this embodiment, in a state where the float main body 10 is currently seated on the upper end of the cylindrical guide member 3, the air leakage amount indicating means 18 indicates the position on the indicating scale section 20 at the opposite position. , "No air leakage" is marked on the scale, and when the amount of air leakage has reached the allowable limit, "leakage amount permissible limit" is marked on the display scale section 20 indicated by the air leakage amount indicating means 18;
Further, "small air leakage amount" is calibrated at an intermediate position between the scales of "no air leakage" and "air leakage amount permissible limit", and this indicator scale portion 20 is fixed to the bottomed container 2.

The leakage amount permissible limit alarm section 32 includes an air leakage amount alarm (not shown), a switch 7 for driving the air leakage amount alarm, an actuator 8 that operates the switch 7, and the like.
It is disposed so as to be interlocked with the floating element structure 4.

That is, the actuator 8 has a central axis 16 at the liquid level 1.
The air leakage alarm drive switch 7 is attached to a part protruding from the air leakage alarm 1, and the air leakage alarm drive switch 7 is located at a position where the actuator 8 operates the air leakage alarm drive switch 7 when the air leakage reaches the permissible limit. The signal transmission means 22
Connect to an air leakage alarm (not shown).

The leakage conduit 9 has one end connected to, for example, a leakage discharge port of a containment valve that seals compressed gas in a box-shaped shell, and connects the leakage conduit 9 to the liquid level 11 of the liquid 12. from a position above the bottom, through the leakage conduit introduction port 21 located at the center of the bottom of the bottomed container 2, to reach the axial center position of the lower end of the cylindrical guide member 3 located at the inner bottom of the bottomed container 2, The other tube end is opened upward.

In addition, in the above, the liquid 12, the bottomed container 2, the cylindrical guide member 3, etc. may be made transparent.

Further, the horizontal cross-sectional shapes of the bottomed container 2, the cylindrical guide member 3, the floater body 10, etc., are approximately elliptical in addition to the circular shape of this embodiment, as long as the opposing shapes are a combination of similar shapes. , other shapes, polygons, etc.

In addition, the liquid 12 is a liquid whose specific gravity is lighter than water 1,
For example, depending on the use of light oil or liquids with a specific gravity higher than 1, such as salt water, etc., materials with appropriate specific gravity are selected and used in combination as materials for the float structure 4. The size of the float body 10 may be appropriately selected to adjust the buoyancy of the float body 10 received from the liquid 12, and the magnitude of the sinking force of the float structure 4 may be set.

In addition, in this embodiment, in order to have an outer shape that allows upward bubble flow due to air leakage to be easily dissipated upward after being received by the annular portion 30 on the lower surface, the flange-shaped portion at the upper end of the float main body 10 is Although it is formed into a downward truncated cone, it is not necessarily limited to this.

Application Example FIG. 2 is an explanatory diagram of the configuration when the leakage amount detector of the present invention is applied to a device that evaluates the airtightness of the shell wall of a box-shaped shell by the pressure-time method. .

In this device, compressed gas at a predetermined pressure is supplied from a compressed gas source 23 to a first air supply valve 24, a second air supply valve 25,
Then, after feeding the compressed gas into the box-shaped shell 28 through the filling valve 26, the filling valve 26 is closed, and the feeding of the compressed gas is stopped by the first air supply valve 24, and the compressed gas in the air supply valve system is The leakage air is released into the atmosphere through the exhaust pipe 31, and then the leakage air leaking from the valve seat of the containment valve 26 is directed to the leakage amount detector 1 through the second air supply valve 25,
The leakage amount detector 1 detects the amount of air leaking from the valve seat of the sealing valve 26 during a predetermined period of time.

At this time, each of the above-mentioned valves is electrically controlled in a predetermined order by the control device 27.

Further, the enclosed compressed gas is transferred to the box-shaped shell 2
A pressure gauge 29 measures the pressure value inside the box-shaped shell 28 after a predetermined period of time, which drops due to leakage into the atmosphere from the poor airtightness of the shell wall 8 and the valve seat of the containment valve 26. The airtightness of the shell wall of the box-shaped shell body 28 is evaluated from this pressure value and the amount of air leaking from the valve seat of the enclosure valve 26.

In this case, the display scale of the leakage amount indicator 6 of the leakage amount detector 1 indicates "Leakage amount small" and "Leakage amount permissible limit".
A correction value for correcting the pressure value in the box-shaped shell body 28 corresponding to Appropriate evaluation is continued by taking maintenance measures such as replacing the sealing valve 26 before the amount of air leaking from the valve exceeds a certain allowable value.

Examples of the box-shaped shell 28 include those that require a high degree of airtightness, such as cast intake/exhaust manifolds of internal combustion engines and cast gearboxes.

<Usage mode> When compressed gas is sealed in the box-shaped shell 28 as a specimen by the sealing valve 26 and evaluation of the airtightness of the shell wall of the box-shaped shell 28 is started, the valve seat of the sealing valve 26 is sealed. The leakage air is guided into the leakage amount detector 1 by the leakage conduit 9. The leaked air discharged from the upward open end of the leakage conduit 9 becomes an upward bubble flow in the liquid 12. As a result, when a floating fluid force larger than the sinking force of the floater structure 4 acts on the floater body 10, the floater structure 4 levitates in the liquid 12, and the upwardly flared portion of the bottomed container 2 The air leakage amount is displayed on the air leakage amount display section 6 while standing still at the balance position. This will be explained in more detail below.

That is, when there is almost no leakage or an extremely small amount of air leakage, and the floating fluid force due to the upward bubble flow applied to the float body 10 is smaller than the sinking force of the float structure 4, the float body 10 becomes cylindrical. The air leak amount indicating means 18, which is located on the upper end of the shaped guide member 3, indicates the "no air leak" scale on the indicator scale section 20. The amount of leakage gradually increases, and the float body 1
When the floating fluid force acting on the float body 10 becomes larger than the sinking force of the float structure 4, the float body 10
2, but at this time, the downward truncated cone 1
Due to the increase in the gap between the bottom periphery of No. 5 and the upwardly flared portion of the bottomed container 2, a portion of the rising bubble flow rises through the gap, thereby increasing the levitation fluid force applied to the float body 10 and the float structure. It comes to rest at a position where the sinking force of 4 is balanced. As a result, the air leakage amount indicating means 18 indicates the degree of air leakage on the display scale section 20, for example, as "air leakage amount small."

If the amount of air leakage becomes larger, the float body 10
floats higher and remains balanced, but when it finally reaches the allowable air leakage limit, it floats even higher, and the air leakage indicating means 18 indicates the "allowable air leakage limit" on the display scale section 20. At the same time, the alarm drive switch 7 of the leakage amount permissible limit alarm section 32 is actuated by the actuator 8 to drive an alarm (not shown),
Issue an alarm.

The rising bubble flow of the leaked air applies a floating fluid force to the float body 10, and then flows out into the atmosphere through the liquid level 11.

When the liquid 12 accompanying this upward bubble flow leaves the upper end of the cylindrical guide member 3, the accompanying action of the upward bubble flow becomes rough in the bottomed container 2 having a wide cross-sectional area, and the upward force decreases. At the same time, the bubbles are driven to the outer periphery of the bottomed container 2 due to the subsequent rising bubble flow, lose their upward force, and descend, passing through the circulation path 14, reaching the lower end of the cylindrical guide member 3, and returning to the cylindrical guide member. The ring flows into the inner shell side of No.3.

<Effects of the Invention> The method for detecting the amount of air leakage and the amount of air leakage detector according to the present invention are as described above, and exhibit the following effects.

(1) Since the main parts of the float structure, including the float body, float and sink in the liquid contained in it, a. Regarding the structure of the float structure, there are As such, there is little demand for extreme weight reduction, therefore there are no strict weight constraints on the structure, and there is flexibility in selecting component materials.

b. Therefore, it is easy to configure the connection mechanism with the leakage amount display section, the leakage amount permissible limit alarm section, and the like.

c. By configuring the float member with a material with a specific gravity close to the specific gravity of the stored liquid, or by configuring the float member with an apparent specific gravity close to the specific gravity of the stored liquid, it can be made sensitive to minute amounts of air leakage. Correspondingly, a floating movement of the float structure can be performed.

d Rising bubble flow near the area where leakage air is released,
The accompanying liquid flow is guided upward by a cylindrical guide member, and then the liquid flow is separated from the upward bubble flow and circulated through the reflux path.
The descending liquid flow does not interfere with the upward bubble flow, the floating fluid force of the upward bubble flow is efficiently transmitted to the float body, and the float structure stably floats and sinks.

e If the bottomed container is made of a transparent material and a transparent liquid is stored therein, the position of the float body in the liquid can be visually observed, so the amount of air leakage can be generally determined quantitatively.

(2) Because the structure has fewer mechanical parts that are prone to wear and clogging, it is less likely to deteriorate in functionality over time.

(3) Since the float body is formed and arranged so as to have a flange-like part at the upper end that can be brought into contact with the rising bubble flow, the floating movement of the float member due to the rising bubble flow of leakage air is prevented. It is done stably.

(4) Since the float body is configured to sit on the upper end of the cylindrical guide member, the amount of air leaking from the valve seat of the sealed valve is extremely small, so the float body is placed on the upper end of the cylindrical guide member. Even if the float does not float, if air bubbles accumulate on the lower side of the brim of the float body on the inner side of the cylindrical guide member, the float structure will be intermittently pushed up slightly, causing larger air bubbles to accumulate. It can also be confirmed that the amount of air leaking from the sealing valve is extremely small because it floats to the surface.

(5) Since the permissible limit of the amount of leakage is "indicated" and a "warning" is issued, there is no risk of overlooking the state in which the amount of leakage from the valve seat of the sealed valve exceeds the permissible value.

It goes without saying that this invention is not limited to the embodiments and drawings described above, and design changes are allowed within the scope of the creativity of the technical idea.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram of an embodiment of the leakage amount detector according to the present invention, and FIG. 2 is a schematic explanatory diagram of an application example of the leakage amount detector. 2... A bottomed container having an upwardly flared part at the top that is open to the atmosphere, 3... Cylindrical guide member, 4... Floater structure, 6... Leakage amount indicator,
8... Actuator, 9... Air leak conduit, 10... Floater body, 12... Liquid, 14... Circulation path, 15...
A downward truncated cone as a brim-like part of the float body, 16... central axis, 18... leakage amount indicating means,
32...Leakage amount permissible limit alarm section.

Claims (1)

[Scope of Claims] 1. A bottomed container having an upwardly flared portion at the top that is open to the atmosphere is filled with liquid up to a predetermined liquid level, and leaked gas is introduced into the inner bottom of the bottomed container. A rising bubble flow generated in the liquid by discharging it upward into the liquid and an accompanying liquid flow are directed upward on the inner side of a cylindrical guide member disposed at the inner bottom of the bottomed container. After that, the rising bubble flow passes through the upwardly flared part and floats above the liquid level, and the liquid flow passes through the circulation path on the outer side of the cylindrical guide member and reaches the bottom of the bottomed container. The flange-like part of the float main body, which has a flange-like part that can be brought into contact with the rising bubble flow, is brought into contact with the upper end of the cylindrical guide member, and from this position, the float main body is The upwardly flared portion is levitated in the liquid by the floating fluid force of the rising bubble flow, and the floating portion is caused to float in accordance with the size of the upwardly flared portion and the slope shape of the upwardly flared portion. Detecting the amount of air leakage, characterized in that the child body is balanced and stationary, the size of the leakage amount of the leaked gas is detected and displayed in conjunction with the floater main body, and the leakage amount permissible limit is alerted. Method. 2. A bottomed container having an upwardly flared part at the top that is open to the atmosphere is arranged, a liquid is stored in the bottomed container up to a predetermined liquid level, and a leakage conduit for guiding leakage gas is connected to the top of the liquid. A cylindrical guide member with the pipe end of the leakage conduit facing upward, reaching the center of the inner bottom of the bottomed container through a position higher than the liquid level, and having both upper and lower ends open; An upward bubble flow of the leaked gas and an accompanying liquid flow disposed in the liquid at the lower part of the bottomed container so as to share the axis of the bottomed container, and discharged from the pipe end opening of the leakage conduit. A flow path is formed for guiding the liquid on the inner side of the cylindrical guide member, and a gap is provided between the outer casing of the cylindrical guide member and the inner casing of the bottomed container to guide the accompanying liquid flow. forms a circulation path to allow circulation, and is seatable on the upper end of the cylindrical guide member;
A float body is formed which has a flange-like portion at its upper end that has a shape and size that can receive a floating field fluid force of a predetermined magnitude or more when the rising bubble flow comes into contact with it, and A center axis is vertically disposed at the center of the upper surface to constitute a float structure consisting of the float body and the center axis, and when the floating fluid force due to the upward bubble flow does not act on the float body, the liquid When the floater body sinks and a floating fluid force of the predetermined magnitude or more is applied to the floater body, the floater body is given a specific gravity to the liquid that is large enough to float in the liquid, and the floater body The body is placed in the liquid so that its central axis and the upwardly flared part share an axis, and the float body is placed on the upper end of the cylindrical guide member as required. A guiding tool is disposed to hold and guide the float structure so that it can float and sink along the axis up to a height position, and when the float main body makes the float and sink motion, Due to the change in the gap between the peripheral edge of the flange-shaped part and the inner shell of the upwardly flared part, the float body is balanced and stationary at a predetermined position in the liquid. A slope and a slope length of the diverging portion corresponding to a required distance for the float body to make the floating motion are given to the upward flared portion, and the floating motion of the float body is caused through the central axis. 1. A leakage amount detector comprising: an air leakage amount display section for the leaked gas that operates in conjunction with the leakage amount; and an air leakage amount permissible limit alarm section.