JP2001221707A - Inspection method for leakage and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a leakage inspection apparatus compact and cheaper and readily provide ease of handleability and high versatility to the apparatus. SOLUTION: Determination is made as to whether or not there are leaks, by detecting whether or not the preset condition of pressure (negative pressure) within the subject of inspection which is not higher than atmospheric pressure is maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for inspecting leaks of, for example, pipe joints made of cast iron.

[0002]

2. Description of the Related Art In a conventional leak inspection method, the inside of an inspection object is increased to a pressure higher than a predetermined atmospheric pressure, and it is detected whether or not the pressure is maintained for a predetermined time. Thus, the presence or absence of leakage was determined.

[0003]

In the conventional leak inspection method, it is required to securely close the opening of the inspection object against the internal pressure. It is necessary for the inspection device, and it is necessary to properly set the inspection object in the leak inspection device so that it can be performed,
The leak inspection device is not compact, reduces the cost, and simplifies handling. Further, the closed structure can only deal with the inspection object having the same shape and size, and the leak inspection device is not widely used. I was

[0004]

The leak inspection method of the present invention detects the presence or absence of a leak by detecting whether or not a pressure state below a preset atmospheric pressure in an inspection object is maintained. Is determined. Alternatively, the presence or absence of a leak is determined by reducing the pressure in the test object to a reference pressure equal to or lower than a preset atmospheric pressure and detecting whether the reference pressure is maintained for a predetermined determination time. I do. Alternatively, the pressure in the test object is reduced to a reference pressure equal to or lower than a preset atmospheric pressure, and a difference between the reference pressure and the pressure in the test object is determined within a predetermined determination time, within a predetermined allowable range. If there is, it is determined that there is no leakage, and if it exceeds the allowable range, it is determined that there is leakage. Then, the output value from the pressure sensor is used as a measurement value as it is until the pressure in the inspection object reaches the reference pressure, and the reference pressure is set to “0” after the reference pressure is reached. Preferably, a value is used. In addition, it is preferable to perform a preliminary determination to determine that there is a leak if the pressure in the inspection object does not reach the reference pressure during a preset evacuation time.

[0005] The leak inspection apparatus of the present invention connects a vacuum pump that sucks air in an object to be inspected whose opening is closed, a pressure sensor that measures air pressure in the object to be inspected, and a pressure sensor to connect the leak sensor. A controller for determining the presence or absence.
Alternatively, a lid for closing the opening of the inspection object, a vacuum pump for sucking air from the inspection object from a suction hole formed in one lid, and an electromagnetic wave provided in the middle of a pipe between the suction hole and the vacuum pump. A valve, a pressure sensor provided in the middle of the pipe between the suction hole and the electromagnetic valve to measure the air pressure in the object to be inspected, and a controller for connecting the electromagnetic valve and the pressure sensor to determine the presence or absence of leakage. . A packing is provided on the joint surface of the lid with the opening of the inspection object.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view of a leak inspection device, and FIG. 2 is a partially enlarged cross-sectional view of the leak inspection device.
(2) is a table for mounting an inspection object fixed on the upper surface of the machine (1), and (3) is a frame (4) above the machine (1).
A pneumatic cylinder fixedly supported via a to protrude the piston rod (3a) downward; and (5) a test object position fixed to the tip of the piston rod (3a) and provided in parallel above and opposite the table (2). The push plate for fixing, (6) is erected at right angles from the push plate (5), and the upper part is slidably supported in the vertical direction on the frame (4) so as to prevent the push plate (5) from rotating and moving up and down. A guide rod for guiding, (7) an air compressor for supplying compressed air to the air cylinder (3), and (8) provided in a pipe connecting the air compressor (7) and the air cylinder (3). An air reservoir, (9) a filter provided in the piping between the air reservoir (8) and the air cylinder (3),
An air unit including a pressure reducing valve, an oiler and the like, (10) a lid plate detachably fastened and fixed to the upper surface of the table (2) and the lower surface of the push plate (5), and (11) a lid on the table (2) side A rubber plate-shaped packing that is attached and fixed to the upper surface of the plate (10) and the lower surface of the lid plate (10) on the side of the push plate (5), and (12) is a lid that is fixed to the table (2) and its upper surface. (10) and a suction hole passing straight through the packing (11), (1)
3) a vacuum pump connected to the suction hole (12) on the lower surface side of the table (2) to suck air from the inspection object;
4) is an air reservoir provided in the middle of the pipe connecting the suction hole (12) and the vacuum pump (13), and (15) is the suction hole (1).
2) An electromagnetic valve provided in the middle of the pipe between the air reservoir (14) and (16) a pressure provided between the suction hole (12) and the electromagnetic valve (15) to measure the air pressure in the inspection object. sensor,
(17) is a controller having a microcomputer having various operation buttons, a display, and the like, and connecting a solenoid valve (15) and a pressure sensor (16) to determine the presence or absence of leakage. (18) is a controller (17). ) Is a pressure indicator for digitally displaying the measured pressure to an operator.

As shown in FIGS. 1 and 2, a socket type (hereinafter referred to as "socket") (19) in a cast iron pipe joint, which is an example of an object to be inspected, is subjected to the above-described leak inspection apparatus to detect leakage. The case of determining the presence or absence will be described. First, the socket (19) is placed vertically on the upper surface of the table (2), and the lower open end surface of the socket (19) is placed on the lid (10) of the table (2). Packing (11) on top of
The socket (19) is set in the leak inspection apparatus in a state where the socket (19) is abutted and supported through the opening and the suction hole (12) is opened substantially at the center of the lower opening end surface of the socket (19) (FIG. 1). State).

After the socket (19) is set in the leak inspection apparatus as described above, the automatic control of the leak inspection is started by operating the start button of the controller (17). 4 and FIG. 4, first, compressed air is supplied from the air compressor (7) to the air cylinder (3), and the piston rod (3) is supplied.
a) is projected against the return spring, the pressing plate (5) is pressed down and pressed against the socket (19) from above, and the socket (1) is pressed.
9) is fixed on the table (2), and at the same time, the lower surface of the lid plate (10) on the push plate (5) side is pressed from above through the packing (11) to the upper open end surface of the socket (19). The upper and lower openings of the socket (19) are closed with the upper and lower lid plates (10) (the state shown in FIG. 2).

Next, a predetermined evacuation time (t (s)) and a reference pressure (a) below atmospheric pressure (negative pressure) are set.
(Pa)) and determination time (T (s)) and determination pressure (A
(Pa)) and the output value of the pressure sensor (16) (P (Pa) in gauge pressure), ie, the socket (1).
9) After inputting the air pressure inside (the socket (1
The air pressure in 9) is a gauge pressure of 0 Pa, that is, atmospheric pressure. ), The solenoid valve (15) is opened by exciting this solenoid, and the air in the socket (19) whose upper and lower openings are closed by the upper and lower lid plates (10) is sucked from the suction hole (12) through the vacuum pump (13). To start evacuation and start measuring the evacuation time.

Next, the output value (P) of the pressure sensor (16) is used as it is as the measured value of the air pressure in the socket (19), and the output value (P) of the pressure sensor (16) and the reference pressure (a) are calculated. When the output value (P) of the pressure sensor (16) reaches the reference pressure (a) during the evacuation time (t) (P = a), the solenoid valve (15) is demagnetized by this solenoid. Then, the evacuation is stopped, and the pressure in the socket (19) is reduced to the reference pressure (a). If the output value (P) of the pressure sensor (16) does not reach the reference pressure (a) even after the evacuation time (t) has elapsed (P <
a) Immediately judge "fail", that is, judge that there is a leak (preliminary judgment), and notify the worker with a display lamp, a buzzer, a sound generator, or the like, and then the air compressor (7). ), The supply of pressurized air to the air cylinder (3) is stopped, the piston rod (3a) is retracted by the return spring, the push plate (5) is pulled upward, and the push plate (5) is pulled upward from the socket (19) ( (Open to the atmosphere), and end the leak inspection of the socket (19).

Only the socket (19) which has not been determined to have a leak by the above preliminary determination is subjected to the subsequent determination, and the output value (P) of the pressure sensor (16) during the evacuation time (t). ) Becomes the reference pressure (a) (P
= A), after closing the solenoid valve (15) by demagnetizing the solenoid, and before making the final determination, first, the reference pressure (a) is set to “0” in the final determination after the preliminary determination. The measurement value (p), that is, the difference between the reference pressure (a) and the pressure in the socket (19) is used to force the measurement value to "0" (p = P + a).

Next, measurement of the judgment time is started, and the measured value (p) of the reference pressure reference is compared with the judgment pressure (A). During the judgment time (T), the measured value (p) is determined to be equal to the judgment pressure (A). If it does not exceed (A), it is judged as "pass", that is, it is judged that there is no leak. If the measured value (p) exceeds the judgment pressure (A), it is judged as "fail", that is, it is judged that there is leak. (This judgment), the operator is notified of this by a display lamp, a buzzer, a sound generator, or the like, and then the air cylinder (3)
Supply of pressurized air to the piston rod (3a)
Is retracted by the return spring, and the push plate (5) is pulled upward and separated upward from the socket (19) (open to the atmosphere).
The leakage inspection of the socket (19) is completed.

The evacuation time (t) is set to, for example, 5 s, the reference pressure (a) equal to or lower than the atmospheric pressure is set to a gauge pressure of, for example, a negative pressure of 93 kPa (a negative pressure of 700 mmHg), and the determination time (T) is set to For example, 12 s is set, and the determination pressure (A) is, for example, 3 kPa (negative pressure 700 mmHg to negative pressure 675 mm
Hg = 25 mmHg).

The measured values (P) and (p) are digitally displayed on the pressure display (18) from the start to the end of the automatic control of the leak test. At the start of the leak test, the pressure indicator (18) displays the measured value (p) at the end of the previous leak test, and is reset immediately after the start of the leak test to return it to "0". . The reset may be performed at the end of the leak test.

As is clear from the above, the socket (1
The presence or absence of a leak is determined by detecting whether or not the pressure (reference pressure (a)) below the preset atmospheric pressure in 9) is maintained. Further, the pressure in the socket (19) is reduced to a reference pressure (a) lower than a preset atmospheric pressure,
By detecting whether the reference pressure (a) is maintained for a preset determination time (T), it is determined whether or not there is a leak. Further, the pressure in the socket (19) is reduced to a reference pressure (a) lower than a preset atmospheric pressure, and the difference (p) between the reference pressure (a) and the pressure (P) in the socket (19) is reduced.
It is determined that there is no leakage if the pressure is within the predetermined allowable range of the determination pressure (A) during the predetermined determination time (T), and if it exceeds the allowable range of the determination pressure (A), the leak is determined. It is determined that there is.

As a result, the internal pressure (P) of the socket (19) works so as to make close contact with the cover (10) closing the opening of the socket (19) and the socket (19). As described above, an actuator such as a cylinder for each opening, which holds the lid in close contact with each opening of the inspection object against the internal pressure considerably higher than the atmospheric pressure of the inspection object, becomes unnecessary, and the socket (19) The opening of (1) is a closed structure with a simple structure, that is, the lid plate (10) alone (the pneumatic cylinder (3) is only for fixing the position of the socket (19), and therefore the pneumatic cylinder is simple, compact and inexpensive. , Among which a more compact and inexpensive one for low pressure can be achieved.)

Even if the set position of the socket (19) changes slightly, the internal pressure (P) of the socket (19) acts uniformly on the cover plate (10), so that the opening of the socket (19) is closed. There is almost no effect, and unlike the conventional leak inspection device, the lid cannot be pressed against the opening with a uniform force just by slightly shifting the set position of the inspection object. Since no trouble is caused, the socket (19) can be easily set in the leak inspection device.

Therefore, it is possible to easily make the leak inspection apparatus compact, reduce the cost, and simplify the handling.

Further, a lid which requires an actuator such as a cylinder for each opening of the inspection object as in the conventional leak inspection apparatus is not required, and one kind of simple closing structure, that is, a simple lid plate (10) is required. This makes it possible to deal with inspection objects having different shapes and sizes only by itself, and to make the leak inspection apparatus highly versatile.

The operation and effect of the above-described method of inspecting leakage using negative pressure will be further clarified by an example in which an object to be inspected other than the socket (19) is applied to the above-described leakage inspection apparatus as shown in FIGS. Fig. 5 shows an example in which a cheese-shaped cast iron pipe joint (hereinafter referred to as a cheese) (20) is applied to the above-mentioned leak inspection apparatus, and the cheese (20) is formed into a vertical shape similarly to the socket (19). By placing the cheese (20) on the upper surface of the table (2), the upper and lower openings of the cheese (20) can be closed by the upper and lower lid plates (10). Then, as shown in FIGS. 7A and 7B, a plug-shaped lid plate (10a) fitted to an opening in the tube wall of the cheese (20) is provided, and the lid plate (10a) is attached to the lid plate (10a). Ring packing made of rubber (1
1a) is fitted and provided, and as shown in FIGS. 6 (a) and 6 (b), the lid plate (10a) is attached to the opening in the tube wall of the cheese (20) via the packing (11a). Just by fitting, the presence or absence of leakage can be determined in the same manner as the socket (19). That is, the internal pressure (P) of the cheese (20) also makes the cheese (20) adhere to the lid (10) closing the upper and lower openings and the lid plate (10a) closing the opening in the tube wall. Therefore, there is no need to press the lid plate (10a) closing the opening in the tube wall of the cheese (20) with an actuator such as a cylinder. The pin (21) passed through the edge of the lid plate (10a) is a pin for confirming that the cheese (20) has been left unborted.

The cross-shaped and Y-shaped cast iron pipe fittings also include a packing (11) fixed to the table (2) and the pressing plate (5), similarly to the above-mentioned cheese (20). By closing the opening other than the lid with the lid plate (10) with the plug-shaped lid plate (10a) with the annular packing (11a), the apparatus can be used for the above-mentioned leak inspection apparatus. still,
A plug-shaped lid plate (10a) with an annular packing (11a)
Is effective because it is not necessary to hold it by hand until the evacuation is started. However, a plate-like lid with a plate-like packing (11) fixed to the table (2) and the pressing plate (5) is effective. Board (1
0).

FIG. 8 shows an example in which an elbow-shaped cast iron pipe joint (hereinafter referred to as an elbow) (22) is subjected to the above-mentioned leak inspection apparatus.
As in the case of a 45 ° elbow, a table adapter (23) for the elbow comprising a pair of tables (2a) having the same relative angle as the bending angle of the elbow (22) to be applied to the leak inspection device is provided. A lid plate (10) with a plate-shaped packing (11) is detachably fastened and fixed to the inner surface side of each table (2a) of the adapter (23), and fixed to either one of the tables (2a) and the inner surface thereof. A suction hole (12a) penetrating the cover plate (10) and the packing (11) in a straight line is provided, and the table adapter (23) is attached to the cover plate (1) with the packing (11).
0) is attached to the upper surface of the original table (2) from which the original suction holes (1) are removed on the lower surface side of the original table (2).
By connecting the elbow (22) to the table adapter (23) with the air suction pipe connected to 2) connected to the suction hole (12a) of the table adapter (23), both elbows (22) are placed. Can be closed by a cover plate (10) with a plate-like packing (11) fixed to each table (2a), and a suction hole ( 12a) can be opened, and the presence or absence of leakage can be determined similarly to the socket (19). That is, since the internal pressure (P) of the elbow (22) works so as to adhere to the lid (10) closing both openings, the elbow (22) also closes both openings having different opening directions. It is not necessary to press each of the lid plates (10) with an actuator such as a cylinder. At the time of inspection, similarly to the socket (19), the push plate (5) is pressed down and pressed against the elbow (22) from above, and the elbow (22) is fixed in position on the table adapter (23).

[0023] In the above-described leak inspection method utilizing negative pressure,
Until the pressure in the test objects (19), (20) and (22) reaches the reference pressure (a), the output value (P) from the pressure sensor (16) is used as it is as a measured value, and is used as the reference pressure (a). From this point onward, by using the measured value (p) of the reference pressure reference that sets the reference pressure (a) to “0”, the pressure condition at the time of making this determination is determined by the inspection object (19) (20).
(22) It can be unified regardless of the shape and size, and it is possible to judge the presence or absence of leakage under certain conditions, eliminate the dispersion of the judgment accuracy, stabilize the judgment accuracy and improve the reliability. It can be improved.

Also, a preset evacuation time (t)
If the pressure (P) in the inspection objects (19), (20), and (22) does not reach the reference pressure (a), a preliminary determination is made to determine that there is a leak during the inspection.
9) The pressure (P) in (20) and (22) is changed to the reference pressure (a).
When a test object with a large leak that cannot be decompressed is applied to a leak tester, it is possible to immediately proceed to the leak test of the next test object without performing unnecessary evacuation. Thus, the work efficiency can be improved.

In this embodiment, a cast iron pipe joint is shown as an example of an object to be inspected. However, the present invention is applicable to leak inspection of various products such as metal pipes as well as other cast products such as an integrated valve box. You can do it.

[0026]

As described above, according to the leak inspection method of the present invention,
The presence or absence of a leak is determined by detecting whether or not the state of the pressure (a) below the preset atmospheric pressure in the inspection objects (19), (20), and (22) is maintained. Alternatively, the inside of the inspection objects (19), (20), and (22) is reduced to a reference pressure (a) that is equal to or less than a predetermined atmospheric pressure, and the reference pressure (a) is maintained for a predetermined determination time (T). , The presence or absence of a leak is determined by detecting whether or not it is maintained. Alternatively, the pressure in the inspection objects (19), (20), and (22) is reduced to a reference pressure (a) equal to or lower than a preset atmospheric pressure, and the reference pressure (a) is reduced.
(P) between the pressure and the pressure (P) in the inspection objects (19), (20), and (22) is within a predetermined allowable range (A) for a predetermined determination time (T). If it is determined that there is no leak, it is determined that there is a leak if it exceeds the allowable range (A).
As a result, the internal pressure (P) of the inspection objects (19), (20), and (22) is applied to the lids (10) and (10a) closing the openings of the inspection objects (19), (20), and (22). Thing (19)
(20) Since it works so as to be in close contact with (22), the openings of the inspection objects (19), (20), and (22) can be reliably closed with a simple closed structure. The objects (19), (20), and (22) can be easily set in the leak inspection device, and the leak inspection device can be easily made compact, reduced in cost and simplified in handling. With a simple type of closed structure, it is possible to cope with inspected objects (19), (20), and (22) having different shapes and sizes, and it is possible to provide the leak inspection apparatus with high versatility. .

The inspection object (19) (20) (22)
Until the internal pressure (P) reaches the reference pressure (a), the output value (P) from the pressure sensor (16) is used as a measured value as it is, and after the reference pressure (a) is reached, the reference pressure (P) is used. By using the measured value (p) of the reference pressure standard in which a) is set to “0”, it is possible to determine whether or not there is a leak under a certain condition, and to eliminate the variation in the determination accuracy.
There are effects such as stabilization of determination accuracy and improvement of reliability.

Further, if the pressure (P) in the inspection object (19), (20), (22) does not reach the reference pressure (a) during the preset evacuation time (t), there is a leak. By performing a preliminary determination of determining that
9) The pressure (P) in (20) and (22) is changed to the reference pressure (a).
When a test object with a large leak that cannot be decompressed is applied to a leak tester, it is possible to immediately proceed to the leak test of the next test object without performing unnecessary evacuation. This has the effect of improving work efficiency.

[Brief description of the drawings]

FIG. 1 is a schematic view of a leakage inspection device in a state of inspecting a socket for leakage.

FIG. 2 is a partially enlarged sectional view of FIG. 1;

FIG. 3 is a flowchart of automatic control of leak inspection.

FIG. 4 is a diagram showing measured values at the time of leak inspection;

FIG. 5 is a schematic view of a leak inspection device in a state of inspecting a cheese for leakage.

FIG. 6 is an explanatory view showing a method of closing an opening of a tube wall of cheese.

FIG. 7 is an explanatory view of a lid plate for closing an opening of a tube wall of cheese.

FIG. 8 is a schematic view of a leak inspection apparatus in a state where an elbow is inspected for leakage.

[Explanation of symbols]

 (1) Machine stand (2) Table (3) Air cylinder (5) Push plate (7) Air compressor (10) Cover plate (10a) Cover plate (11) Packing (11a) Packing (12) Suction hole (13) ) Vacuum pump (15) Solenoid valve (16) Pressure sensor (17) Controller (18) Pressure indicator (19) Socket (test object) (20) Cheese (test object) (22) Elbow (test object)

Claims (8)

[Claims] 1. A leak inspection method comprising: determining whether a leak is detected by detecting whether a pressure state equal to or lower than a preset atmospheric pressure in an inspection object is maintained. 2. The method according to claim 1, further comprising reducing a pressure inside the inspection object to a reference pressure equal to or lower than a predetermined atmospheric pressure, and detecting whether the reference pressure is maintained for a predetermined determination time. A leak inspection method characterized by determining the presence or absence of a leak. 3. The pressure in the test object is reduced to a reference pressure equal to or lower than a preset atmospheric pressure, and a difference between the reference pressure and the pressure in the test object is set for a predetermined judgment time. A leak inspection method, wherein it is determined that there is no leak if the value is within the allowable range, and it is determined that there is leak if the value exceeds the allowable range. 4. The output value from the pressure sensor is used as it is as a measured value until the pressure in the inspection object reaches the reference pressure, and the reference pressure is set to “0” after the reference pressure is reached.
4. The leak inspection method according to claim 3, wherein a measured value of a reference pressure reference is used. 5. A preliminary judgment for judging that there is a leak if the pressure in the inspection object does not reach a reference pressure during a preset evacuation time. Leak inspection method. 6. A vacuum pump for sucking air in an object to be inspected whose opening is closed, a pressure sensor for measuring air pressure in the object to be inspected, and a controller for connecting the pressure sensor to determine whether there is a leak. 2. The method according to claim 1, further comprising:
Or the leak inspection device according to 2 or 3 or 4 or 5. 7. A lid for closing an opening of the inspection object, a vacuum pump for sucking air in the inspection object from a suction hole formed in one lid, and a pipe between the suction hole and the vacuum pump. A solenoid valve provided in the middle, a pressure sensor provided in the piping between the suction hole and the solenoid valve to measure the air pressure in the object to be inspected, and a controller for connecting the solenoid valve and the pressure sensor to determine the presence or absence of leakage The leak inspection apparatus according to claim 1, wherein the leak inspection apparatus comprises: 8. The leak inspection apparatus according to claim 7, wherein a packing is provided on a joint surface of the lid with the opening of the inspection object.