Pressure-resistance inspection apparatus for valves and its inspection method, and hydrogen gas detection unit

Provided are a pressure-resistance inspection apparatus for valves and its inspection method, and hydrogen gas detection unit capable of detecting external leakage and specifying its position of occurrence even for valves with different sizes and shapes by performing pressure-resistance inspection with a simple structure quickly with high accuracy while preventing errors in test results, without requiring post-treatment for the valves, and also capable of mass processing by automation. Provided are a cover 2 in which a test valve 1 is accommodated in a state of being isolated from outside and a sensor 22 inside this cover 2 and capable of moving to a position close to an outer surface of the test valve 1 filled with a search gas. This sensor 22 is a gas sensor capable of detecting external leakage of the search gas from the test valve 1.

TECHNICAL FIELD

The present invention relates to pressure-resistance inspection apparatus for valve boxes of various valves such as, for example, ball valves and globe valves, and their inspection methods and, in particular, relates to a pressure-resistance inspection apparatus for valves and its inspection method, and hydrogen gas detection unit capable of performing pressure-resistance inspection with a simple structure quickly with high accuracy.

BACKGROUND ART

Conventionally, high pressure resistance is required for valves. As pressure tests at the time of manufacture, a valve-box pressure-resistance test (shell test) for checking strength of a pressure-resistant part and the presence or absence of a leak, a valve-seat leak test for checking the presence or absence of a leak from the valve seat (seat test), and so forth are performed. By these, valves before shipping are inspected. Among these, as a valve-box pressure-resistance test, pressure-resistance inspection is performed with, for example, a water bubble leak method, a sniffer method, a vacuum chamber method, or the like. In the water bubble leak method, a test piece with its inside pressurized by gas is immersed in water, and a leak is detected with bubbles from the inside of the test piece. In the sniffer method, a search gas is put inside a test piece, and a probe is made close to the gas flowing to the outside of the test piece to detect a leak by this probe. Also, in the vacuum chamber method, a test piece is accommodated inside a vacuum chamber, a search gas is put inside the test piece, and a gas flowing from the test piece to the vacuum chamber is detected.

On the other hand, in a leak detection apparatus for containers in PTL 1, a technique is disclosed in which a sensor wall having many gas sensors arranged in a hollow apparatus main body is provided and a leak of gas injected into a container under test accommodated in the apparatus main body is monitored by the gas sensors.

According to this technique, sensing by many gas sensors can detect, in addition to occurrence of gas leakage, a leak location of the container under test.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

However, when a valve is inspected with the valve-box pressure-resistance test through the water bubble leak method described above, skill is required because air bubbles from the inside of the valve as a test piece are checked by visual inspection. Depending on the worker, there is also a possibility of failing to find occurring bubbles. Therefore, errors may occur in the inspection results. Moreover, after inspection, post-treatment such as removal of water droplets attached to the valve is required, thereby making the structure of the test apparatus complex and also making automation difficult. In the case of the sniffer method, even when a leak occurs from the inside of the valve, measurement is difficult if the probe does not directly touch that leak position. This poses problems of taking time for inspection for the entire test piece and also requiring skill for probe operation. In the case of the vacuum chamber method, a time until a vacuum state is required at the time of inspection, and therefore efficiency of inspection is poor. Moreover, even if a leak occurs, its leak position cannot be specified. Furthermore, vacuum suction causes a flow of air, and therefore a change in temperature may occur inside the chamber to decrease sensitivity of the sensor.

On the other hand, in the case of the leak detection method for containers of PTL 1, which will be described further below, a gap between the sensor wall and the container under test is narrow. Therefore, a gas leaked from the container under test may be locally retained and may not reach the sensor, thereby disabling leak sensing. When the container under test is completely covered with the sensor wall, a flow of gas that tries to be leaked from the container under test is hindered, and thus a leak may not be able to be sensed.

In addition to these demerits, when this leak detection method is applied to valves, since each valve has a different shape and size as a product under test depending on its type, nominal pressure, nominal diameter, and so forth, a somewhat large sensor wall is required to support these differences. However, if the test piece is small compared with the sensor wall, a distance between this test piece and the sensor may be too wide to disable leak sensing.

The present invention has been developed to solve the conventional problems, and has an object of providing a pressure-resistance inspection apparatus for valves and its inspection method, and hydrogen gas detection unit capable of detecting external leakage and specifying its position of occurrence even for valves with different sizes and shapes by performing pressure-resistance inspection with a simple structure quickly with high accuracy while preventing errors in test results, without requiring post-treatment for the valves, and also capable of mass processing by automation.

Solution to Problem

To achieve the object described above, the invention according to claim1is directed to a pressure-resistance inspection apparatus for valves including a cover in which a test valve is accommodated in a state of being isolated without being sealed from outside and a sensor inside this cover and capable of moving in an approaching direction to a position close to an outer surface of the test valve filled with a search gas, this sensor being a gas sensor movable to a retention region of the search gas externally leaked from the test valve.

The invention according to claim2is directed to the pressure-resistance inspection apparatus for valves, in which the gas sensor is a hydrogen sensor capable of detecting external leakage of hydrogen in a mixture gas of hydrogen and nitrogen formed of a gas containing hydrogen, which is the search gas with which inside of the test valve is filled.

The invention according to claim3is directed to the pressure-resistance inspection apparatus for valves, in which the cover is formed in a cylindrical shape so that flange parts formed on both sides of the test valve formed of a ball valve can be disposed at upper and lower positions, and the gas sensor is provided so as to be movable in a retention region of the search gas on a back surface of the flange part disposed at the upper position.

The invention according to claim4is directed to the pressure-resistance inspection apparatus for valves, in which a stem of the test valve formed of a globe valve is provided so as to be mountable in an upwardly-oriented state, and the gas sensor is provided so as to be movable in a retention region of the search gas near a cap part attached above the glove valve.

The invention according to claim5is directed to the pressure-resistance inspection apparatus for valves, in which the apparatus has a flange-shaped jig by which the flange parts formed on both sides of the test valve are clamped in a sealed state, and the cover is provided so as to be able to make reciprocating movements in a clamping direction so as to be able to isolate the test valve from outside or expose the test valve to outside, with a clamped state of the flange parts by the jig.

The invention according to claim6is directed to the pressure-resistance inspection apparatus for valves, in which the gas sensor has attached thereto a rotation driving device capable of making angle adjustment in a direction of approaching or departing from the test valve.

The invention according to claim7is directed to the pressure-resistance inspection apparatus for valves, in which the cover is provided with an exhaust fan which exhausts a gas inside the cover.

The invention according to claim8is directed to a pressure-resistance inspection method for valves, in which a test valve is accommodated in a cover in a state of being isolated without being sealed from outside, a gas sensor is moved in an approaching direction to a retention region of a search gas, which is a position close to an outer surface of a joint part of components serving as this test valve, and, when the test valve is filled with the search gas, external leakage of the search gas from the test valve is detected.

The invention according to claim9is directed to the pressure-resistance inspection method for valves, in which the gas sensor is a hydrogen sensor capable of detecting external leakage of hydrogen in a mixture gas of hydrogen and nitrogen formed of a gas containing hydrogen, which is the search gas with which inside of the test valve is filled.

The invention according to claim10is directed to a hydrogen gas detection unit for use in the pressure-resistance inspection apparatus for valves, in which a plurality of hydrogen sensors are connected to a digital potentiometer, and the unit has an adjustment function of adjusting reference voltages of these hydrogen sensors at a certain value via a microprocessor.

The invention according to claim11is directed to the hydrogen gas detection unit, in which the microprocessor has a function of setting a voltage for determination by, when the reference voltages of the respective hydrogen sensors are varied, adjusting each of these varied variable voltages with the digital potentiometer, and setting a voltage for sensing hydrogen for this voltage for determination.

The invention according to claim12is directed to the hydrogen gas detection unit, in which the microprocessor has a function of storing a resistance value of the test valve measured by the digital potentiometer, starting adjustment of the resistance value for a next test valve for inspection based on this resistance value, thereby reducing a time to be taken for setting the reference voltage of each of the hydrogen sensors.

Advantageous Effects of Invention

From the invention according to claim1, the apparatus has a cover in which a test valve is accommodated in a state of being isolated from outside and a sensor inside this cover and capable of moving to a position close to an outer surface of the test valve, and the sensor is a gas sensor capable of detecting external leakage of the search gas such as hydrogen from the test valve. Thus, even for valves with different sizes and shapes, with a simple structure, the gas sensor is made close to the outer surface of the joint part of components where external leakage of the test valve may occur, and pressure-resistance inspection is performed quickly with high accuracy while errors in test results are prevented, thereby allowing external leakage to be detected and also its position of occurrence to be specified by the gas sensor. Unlike pressure-resistance inspection of a water bubble leak type, post-treatment for the valve such as removal of water droplets is not required, and therefore automation can be made, and successive mass processing can also be performed.

From the invention according to claim2, the gas sensor is a hydrogen sensor capable of sensing external leakage of hydrogen in a mixture gas of hydrogen and nitrogen formed of a gas containing hydrogen, which is the search gas. Thus, hydrogen is safely retained around the test valve at the time of occurrence of external leakage and, by using this property, even subtle external leakage is accurately detected.

From the invention according to claim3, with the cover formed in a cylindrical shape, while the flange parts on both sides of the test valve are arranged at predetermined positions inside the cover as being disposed at upper and lower positions, and pressure-resistance inspection is performed on this test valve in a state in which the gas senor is moved to the retention region of the search gas on the back surface of the flange part disposed at the upper position. Thus, in particular, external leakage from the outer surface of the joint part below the upper flange part can be reliably detected.

From the invention according to claim4, the test valve formed of a globe valve is accommodated inside the cover with the stem being in an upwardly-oriented state, the leaked search gas is accumulated in the retention region of this test valve, and pressure-resistance inspection is performed by making the gas sensor close thereto to allow reliable detection of external leakage.

From the invention according to claim5, by clamping the flange parts on both sides of the test valve by a flange-shaped jig, pressure-resistance inspection can be performed in a state in which an unnecessary leak between the flange part and the jig is prevented. In the clamped state by the jig, the test valve can be isolated from outside or exposed, thereby preventing leakage of the gas to the outside of the cover and also facilitating attachment and detachment of the test valve. This allows valves under test to be successively attached to and detached from the cover, and automation of pressure-resistance inspection can also be made.

From the invention according to claim6, the angle of the hydrogen sensor can be adjusted by a rotation driving device such as a servo motor in a direction of an approaching or departing from the test valve. Thus, even for a test valve having an outer surface in an uneven shape, the hydrogen sensor is made close to a position where external leakage may occur to detect a leak with high accuracy. On the other hand, by operating the hydrogen sensor to a direction of departing from the test valve, the test valve can be arranged at a predetermined position inside the cover or can be easily removed from the cover, without this hydrogen sensor getting out of the way.

From the invention according to claim7, hydrogen inside the cover is exhausted to outside by the exhaust fan to prevent retention of hydrogen after external leakage inspection. Even when pressure-resistance inspection is successively performed on different valves under test by using the same cover, the presence or absence of external leakage, its position of occurrence, and the amount of leakage are accurately detected.

From the invention according to claim8, a valve with a different size and shape is accommodated inside the cover, and for this valve, while errors in test results are prevented with a simple structure having a gas sensor, external leakage and its position of occurrence can be detected quickly with high accuracy. Unlike inspection of a water bubble leak type, post-treatment for the valve such as removal of water droplets is not required, and therefore automation can be made, and successive mass processing can also be performed.

From the invention according to claim9, hydrogen is safely retained around the test valve at the time of occurrence of external leakage and, by using this property, even subtle external leakage is accurately detected.

From the invention according to claim10, with the reference voltages of the plurality of hydrogen sensors being adjusted at a certain value, sensitivities of the hydrogen sensors are equalized to allow a hydrogen gas to be detected with high accuracy.

From the invention according to claim11, different reference voltages of the respective hydrogen sensors can be adjusted and, to this reference voltage, a voltage for determination for reliably detecting external leakage can be set.

From the invention according to claim12, a resistance value of the test valve is stored and, based on this resistance value, adjustment of the resistance value is started for a next test valve. Thus, processes until the value reaches near the resistance value for the next test valve are omitted, a time to be taken for setting a reference voltage of the hydrogen sensor is reduced, and efficiency of inspection when automated can be enhanced.

DESCRIPTION OF EMBODIMENTS

In the following, the pressure-resistance inspection apparatus for valves and its inspection method, and hydrogen gas detection unit in the present invention are described in detail based on embodiments.

Depicted inFIG. 1is a perspective view of the pressure-resistance inspection apparatus for valves of the present invention, andFIG. 2depicts a center longitudinal sectional view ofFIG. 1. The pressure-resistance inspection apparatus for valves of the present invention is used for a valve-box pressure-resistance test (pressure-resistance inspection) by filling a test valve as an inspected subject with a gas containing hydrogen and detecting a leak of hydrogen from this test valve to outside.

As depicted inFIG. 1andFIG. 2, a test valve1is formed of, for example, a ball valve. This ball valve1has a body part2and a cover part3, and is configured, in a state in which a stem4, a ball5, and so forth are incorporated inside, by integrating these body part2and cover part3. A gasket6is attached to a joint portion between the body part2and the cover part3, which is sealed therebetween by this gasket6. The stem4is rotatably attached via a laminated packing7by a gland member8inside a neck part9. The packing7seals the space between the body part2and the stem4, and the gland member8. On both sides of the valve1, flange parts10,10are formed, and the valve has an outer surface in an uneven shape including these flange parts10.

At the time of pressure-resistance inspection, as a gas (search gas) with which the above-described test valve1is to be filled, any of gases containing hydrogen is used, for example. Of these, a mixture gas containing 5% hydrogen as a tracer gas with diffusibility and 95% nitrogen as an inert gas is used. This mixture gas has a property of being leaked from a joint part between the body part2and the cover part3and near an attachment part of the gland member8described above, which are components forming the test valve1. when external leakage is present at the time of a pressure-resistance test. The gas with 5% hydrogen is a nonflammable high-pressure gas, and is thus usable safely. As the search gas, in addition to the gas containing hydrogen, any of various gases can be used. For example, also when a helium gas or methane gas is used, diffusibility is high, as with the hydrogen-containing mixture gas.

InFIG. 1andFIG. 2, the pressure-resistance inspection apparatus for valves of the present invention has a cover20, arc-shaped plate members21, sensors22, rotation driving devices (in the present embodiment, servo motors)23, and a jig24, and is used when a valve-box pressure resistance test on the test valve1is performed.

The cover20is formed in a cylindrical shape of, for example, a resin material such as a transparent or translucent acrylic resin, and the diameter of this cylindrical portion is provided so as to be larger than the flange parts10on both sides of the test valve1. This allows the test valve1to be accommodated inside the cover20, with the flange parts10disposed at upper and lower positions. In this case, when external leakage occurs from the joint portion between the body part2and the cover part3of the test valve1, a back surface side of the flange part10positioned above serves as a retention region R for hydrogen. Near this retention region R, hydrogen leaked from below the flange part10tends to be particularly accumulated. It is assumed that this cover20can be used also for valves with different sizes and shapes.

On an upper end side of the cover20, an upper side plate30is fixedly attached. On the other hand, on a lower end side of the cover20, a lower side plate31is provided so as to be able to make contact with and leave from the cover20. With these side plates30and31, the inside of the cover20is covered to have a chamber function. When the test valve1is accommodated inside the cover20, this test valve1becomes in a state of being isolated from outside. Here, since the lower end of the cover20is not closely attached to the lower side plate31, the inside of the cover20communicates outside air, thereby causing a flow of air to some extent inside the cover20and preventing local retention of hydrogen. This facilitates detection of external leakage by the sensors22, which will be described further below.

In this manner, the “state of being isolated from outside” in the present invention does not mean that the inside of the cover20becomes in a hermetically-sealed state, but refers to a state in which influences such as outside wind over the test valve1are prevented and a flow of gas inside the cover20is allowable to a degree that hydrogen leaked from the test valve1reaches the sensor22within an inspection time.

The cover20is preferably provided with an exhaust fan32for exhausting gas such as the mixture gas left inside this cover20. In this case, in the drawing, the exhaust fan32is preferably attached to the upper side of the cover20and, here, hydrogen, which is lighter than air, is efficiently exhausted by the exhaust fan32.

As depicted inFIG. 4, the arc-shaped plate members21are each formed in an arc shape of a letter C with a size allowing the test valve1to be inserted to an inner peripheral side, and are positioned and fixed at two locations by rod-shaped holding members33,33mutually in a substantially parallel state at a predetermined height inside the cover20. This causes, with vertical movements of the cover20, the arc-shaped members21to also vertically move integrally with this cover20. Each arc-shaped plate member21includes the sensors22equidistantly at three locations.

The sensors22are each formed of a gas sensor of a hydrogen sensor which can detect external leakage of hydrogen, which is a search gas from the test valve1, and this hydrogen sensor22is provided so as to be movable to a position close to the outer surface of the test valve1filled with the gas containing hydrogen. This allows detection of external leakage of hydrogen in the mixture gas of hydrogen and nitrogen with which the inside of the test valve1is filled. When a helium gas is used as a search gas, a gas thermal conduction sensor is preferably used.

As depicted inFIG. 4, the hydrogen sensor22is attached to a rotation shaft23aprovided to the servo motor23fixed to the arc-shaped plate member21, and is provided, as depicted inFIG. 3(a)andFIG. 3(b), so as to be rotatable by rotating the rotation shaft23ain a direction of approaching or departing from the test valve1attached to the inner peripheral side of the arc-shaped plate members21so that the angle with respect to the test valve1is adjustable. Depicted inFIG. 3(a)is a state in an A-A cross section ofFIG. 2in which a hydrogen measuring site of each hydrogen sensor22is moved (rotated) to a position close to the outer surface of the test valve1at the time of pressure-resistance inspection, and depicted inFIG. 3(b)is a standby state of the hydrogen sensors22in the A-A cross section ofFIG. 2. Here, a space a serves as a gap between the arc-shaped plate member21having the hydrogen sensors22attached thereto and the test valve1. While a contact between the hydrogen sensors22and the test valve1is avoided, the test valve1can be attached to and detached from the cover20.

While hydrogen is known as a gas with diffusibility, as a comparison example, the hydrogen sensors22were arranged only above the inside of the cover20inFIG. 1andFIG. 2and external leakage was intentionally caused near the gland member8by using a mixture gas of 5% hydrogen and 95% nitrogen, but was not be able to be detected by the hydrogen sensors22within a predetermined inspection time. By contrast, when the hydrogen sensor22were gradually made close to the test valve1, it was found that the above-described mixture gas was retained at a portion where the external leakage occurred. That is why the hydrogen sensors22are moved to positions close to the outer surface of the test valve1, as described above.

And, as described above, in the test valve1depicted inFIG. 1andFIG. 2, the back surface side of the flange part10positioned above provides a so-called umbrella function, and leaked hydrogen tends to be accumulated. Therefore, it is suitable that the hydrogen sensors22are rotationally adjusted by the servo motors23and are then made close to the outer periphery of the test valve1near this retention region R.

In the present embodiment, in this retention region R, three hydrogen sensor22are arranged at intervals of substantially 120 degrees and three more hydrogen sensors22are arranged at intervals of substantially 120 degrees above the flange part10positioned below and at a height close to the gland part8, and thus six hydrogen sensors22in total are used.

Here, the above-described hydrogen sensors22are described in detail. The hydrogen sensors22in the present embodiment are each formed of a module which outputs, with application of a predetermined voltage, a voltage in accordance with the concentration of externally-leaked hydrogen. Before pressure-resistance inspection, it required to perform fine sensitivity adjustment by changing the output voltage by a control for resistance adjustment, in accordance with a warm-up state of the hydrogen sensors22and a change in atmospheric concentration of hydrogen. When this sensitivity adjustment is manually performed, the adjustment is cumbersome and also hinders automation.

Also, to sense a subtle leak, detection requires time if one hydrogen sensor22is used.

From these factors, as described above, six hydrogen sensors22are controlled respectively by the servo motors23. Here, resistance adjustment of six hydrogen sensors22is approximately simultaneously performed by microprocessor control. As a rotation driving device, another device other than a servo motor may be used, such as a stepping motor not depicted.

Depicted inFIG. 6is a block diagram of a hydrogen gas detection unit (hereinafter referred to a unit main body40). The unit main body40has the hydrogen sensors22, a constant voltage power supply41, a digital potentiometer42, a microprocessor43, and a digital display unit44. As depicted in the drawing, specifically, the digital potentiometer42on a substrate which controls six hydrogen sensors22is wired, and while an output voltage is read by the microprocessor43, a resistance value of each channel is slid to be adjusted to a voltage as a reference.

As the hydrogen sensor22for use, a commercially-available semiconductor sensor capable of outputting an analog signal (0-5 V) is used and, for example, a hot-wire semiconductor hydrogen sensor is used. This hydrogen sensor22is a sensor which uses a change of electric conductivity by absorption of a hydrogen gas on the surface of a metal-oxide semiconductor such as tin dioxide (SnO2). In this case, the output voltage becomes logarithmical to the gas concentration to allow high-sensitivity outputs even with low concentration, and therefore this is suitable as a pressure-resistance inspection apparatus. Each hydrogen sensor22is connected to the commercially-available digital potentiometer42for each channel. The digital potentiometer42in the present embodiment is provided with six channels.

Each channel of the digital potentiometer42includes a fixed resistor having a wiper contact (not depicted), adjusting a resistance value between an A terminal and a wiper and one between a B terminal and the wiper while the output voltage is read by the microprocessor43, thereby adjusting the reference voltage of each hydrogen sensor22.

As in the present embodiment, when the plurality of hydrogen sensors22are used, having an adjustment function of adjusting their reference voltages at a certain value via the microprocessor43is preferable. This allows equalization of sensitivities of the respective hydrogen sensors22and highly-accurate detection of the leaked hydrogen gas.

As means for adjusting the reference voltages at a certain value, according to the above-described unit main body40, by using the digital potentiometer42, adjustment of the resistance values can be finely and automatically performed at256positions or the like. Compared with the case of using an analog variable resistor, hydrogen leakage can be sensed accurately and early.

Note that the fixed resistance value between the A-B terminals in the present embodiment is set at any value in a range of 0 to 50 kΩ, and the reference voltage is set at 2 V.

In this case, due to the performance of the resolution of the digital potentiometer42, there is a possibility that it becomes difficult to adjust the reference voltages of six hydrogen sensors22at 2 V and a difference occurs among the reference voltages of the respective hydrogen sensors22. By contrast, when the reference voltages of the respective hydrogen sensors22are varied, the microprocessor43of the unit main body40has a function of adjusting these varied reference voltages each at a voltage for determination and setting a voltage for detecting hydrogen to this voltage for determination.

Specifically, one acquired by the microprocessor43increasing the reference voltage of each hydrogen sensor22by a predetermined ratio is used as a voltage for determination. In the present example, a voltage value acquired by increasing the reference voltage of each hydrogen sensor22by, for example, 5% (a voltage value of 105% of the reference voltage), is taken as a voltage for determination. In this manner, when a voltage for determination for each hydrogen sensor22is set and when hydrogen is sensed, a voltage increase from the reference voltage can be sensed by each hydrogen sensor22as an increase of the voltage value by a predetermined amount, and therefore it is possible to reliably determine the presence or absence of hydrogen leakage. With this, for example, even when the reference voltage of a specific hydrogen sensor22is lower than 2 V and the voltage for determination is also lower than those of the other hydrogen sensors22, a voltage acquired by increasing at a predetermined ratio is sensed, thereby allowing prevention of erroneous sensing.

While adjustment is performed in the present example by taking one acquired by increasing the reference voltage at a certain ratio (for example, 5%) by each hydrogen sensor22as a voltage for determination of each hydrogen sensor22, adjustment can also be performed so that a common voltage for determination is defined for all hydrogen sensors22. In this case, in consideration of variations in reference voltage for each hydrogen sensor22described above, it is required to reliably prevent erroneous sensing by strictly setting a voltage for determination.

Also, the microprocessor43has a function of storing a resistance value measured by the digital potentiometer42in the test valve1and starting adjustment of the resistance value for the test valve1for next inspection based on this resistance value, thereby reducing the time required for setting a reference voltage of each hydrogen sensor22.

In this manner, by adjusting the resistance value for the next test valve1by using the resistance value of the previous test valve1, processes until the value reaches near the resistance value can be omitted, and a time to be taken for setting a reference voltage of the hydrogen sensor22can be reduced, compared with a case in which the measured resistance value is once reset and then a next resistance value is measured. Thus, efficiency of inspection when automated can be enhanced.

When hydrogen leakage occurs from the test valve1, an output is provided via a signal processing unit (not depicted) in a control unit such as the microprocessor43to the digital display unit44as a voltage in accordance with the concentration of the hydrogen gas. The digital display unit44has an LCD (liquid-crystal display), and the output voltage of each hydrogen sensor22is displayed on this LCD as indicator display. Even when the output voltage exceeds the voltage for determination, display is made on the digital display unit44as leak sensing. Depicted inFIG. 6is a state in which the output voltages of the hydrogen sensors22of No. 1 to No. 3, No. 5, and No. 6 fall below the voltage for determination, the output voltage of the hydrogen sensor22of No. 4 exceeds the voltage for determination, and an occurrence of hydrogen leakage from the test valve1is detected at a position where this hydrogen sensor22of No. 4 is arranged.

In this manner, while six hydrogen sensors22are controlled, external leakage is detected, thereby improving detection capability and also leading to reduction of the detection time and automation.

Note that the digital display unit44is any component and it is only required to provide the unit main body40directly or indirectly with a function of taking out and displaying the output value of each hydrogen sensor22.

On the other hand, the jig24depicted inFIG. 1andFIG. 2is provided for fixing the test valve1inside the cover20. This jig24has a clamp member50and a plate member51capable of clamping, with the flange part10of the test valve1being in a sealed state.

The plate member51is formed in a disk shape where the flange part10of the test valve1can be mounted, and is integrally fixed to the lower side plate31. On this plate member51, one flange part10of the test valve1is provided so as to be mountable. The plate member51and the lower side plate31are provided with a through hole52depicted inFIG. 5, which can communicate the test valve1attached to the inside of the cover20.

InFIG. 1andFIG. 2, the clamp member50has a disk-shaped plate board53and rod-shaped operation bars54. The plate board53is formed in a disk shape mountable on the flange part10of the test valve1. In this plate board53and the upper side plate30, a communication hole55depicted inFIG. 5is provided, which can communicate the test valve1inserted inside the cover20. As depicted inFIG. 1andFIG. 2, the operation bars54are integrally attached to the plate board53, and are provided so as to be vertically slidable with respect to the upper side plate30. When the operation bars54are vertically moved, the plate board53also integrally operates. When the operation bars54are caused to descend, the upper flange part10is pressed from above, thereby causing the test valve1to be fixed and retained in a space formed by the plate member51. The number of operation bars54is preferably two as depicted inFIG. 1, but three may be provided as depicted inFIG. 7. In this case, with the plate board53supported at three points, the upper flange part can be pressed with substantially equal forces while the horizontal state of this plate board is maintained.

The clamp member50and the plate member51are preferably provided so as to be able to make contact with an end face of the flange part10in parallel. Furthermore, on each contact side of the clamp member50and the plate member51with the flange part10, an annular seal member not depicted is preferably inserted. In this case, at the time of clamping of the test valve1by the jig24, a leak from a gap is prevented, and an error at the time of pressure-resistance inspection is reduced to be subtle.

Also in a clamped state of the upper and lower flange parts10,10by the jig24, the cover20can be moved to a clamping direction in a reciprocating manner. The cover20is provided so that the test valve1in the clamped state can be isolated from outside or can be exposed by moving the cover20in a reciprocating manner. That is, when the cover20is caused to ascend, the test valve1is exposed to outside and, in this state, the plate board53is caused to ascend via the operation bars54to allow the test valve1to be removed. On the other hand, when the cover20is caused to descend, the test valve1is isolated from outside, allowing pressure-resistance inspection to be performed.

In the above-described pressure-resistance inspection apparatus, when the test valve1is accommodated inside the cover20in a state of being isolated and when each hydrogen sensor22is moved to a position close to the outer surface of the joint part between the body part2and the cover part3as components forming the test valve1and the inside of the test valve1is filled with the mixture gas of 5% hydrogen and 95% nitrogen, hydrogen leakage from the test valve1is detected by any hydrogen sensor22to allow pressure-resistance inspection.

Depicted inFIG. 5is one example of a pressure-resistance inspection facility using the above-described pressure-resistance inspection apparatus for valves as a block diagram. In this pressure-resistance inspection facility60, with an inspection-side flow path61connected to a communication hole55side of the pressure-resistance inspection apparatus and a ventilation-side flow path62connected to a through hole52side thereof, pressure-resistance inspection is performed on the test valve1.

The inspection-side flow path61is branched into a pressurization flow path63and an exhaust flow path64. The pressurization flow path63is provided with a hydrogen gas pressure source65for pressure-resistance inspection, a regulator66for pressure adjustment, a pressurization valve67for opening and closing the flow path, and a pressure sensor68. The exhaust flow path64is provided with an exhaust valve69for opening and closing the flow path. On the other hand, the ventilation-side flow path62is provided with an air pressure source70for ventilation of the inside of the valve, the regulator66for pressure adjustment, and a ventilation valve71for opening and closing the flow path.

Next, the procedure when pressure-resistance inspection is performed by the pressure-resistance inspection apparatus using the above-described pressure-resistance inspection facility60is described by usingFIG. 7. InFIG. 7, for simplification of the drawing, depiction of the communication hole55, the through hole52, and plumbing connected thereto is omitted.

Depicted inFIG. 7(a)is an initial state of the pressure-resistance apparatus and a state in which the cover20ascends from the lower side plate31. In this state, as depicted in the drawing, the test valve1is set while one flange part10is mounted at a predetermined position of the plate member51.

As depicted inFIG. 7(b), with the lower side plate31caused to ascend to bring the upper flange part10into contact with the clamp member50, the test valve1is clamped by the jig24. In this case, inFIG. 5, only the exhaust valve69is in an open state, and the pressurization valve67and the ventilation valve71are in a closed state.

InFIG. 7(c), the cover (chamber)20is caused to descend to bring its lower end into contact with the upper surface of the lower side plate31to cause the test valve1to be accommodated inside the inspection apparatus in a state of being isolated from outside. Here, the inside of the cover20partially communicates outside air as being in a state of being less subjected to influences of outside air, and is therefore in a state of being not completely hermetically sealed. After the descent of the chamber20, the exhaust valve69ofFIG. 5is set in a closed state, and the exhaust fan32is operated, thereby discharging a gas such as the mixture gas that may be left from the inside of the chamber20. Then, the exhaust fan32is stopped, and zero adjustment of the six hydrogen sensor22is performed by the unit main body40ofFIG. 6as described above for sensitivity equalization.

Next, in the state inFIG. 7(c), the servo motors23ofFIG. 3are operated to make the hydrogen sensors22close to the outer surface of the test valve1depicted inFIG. 1andFIG. 2. In this state, the pressurization valve67is set in an open state while the closed state of the exhaust valve69ofFIG. 5is maintained, the inside of the test valve1is filled with the mixture gas from the communication hole55through the inspection-side flow path61and is pressurized, and external leakage of hydrogen is detected by the hydrogen sensors22within a predetermined inspection time. Here, the rotation angle of each servo motor23is adjusted in accordance with the shape and size of the test valve1, and the hydrogen sensor22is made close to a portion where there is a high possibility of occurrence of external leakage of the test valve1. For example, although not depicted, for a small-sized test valve, the rotation angle of the servo motor23is increased to make the hydrogen sensor22close to the test valve1. In this case, with a target range to be detected being narrow, it is not required to use three hydrogen sensors22attached to the arc-shaped member21on the upper stage side, and the inspection procedure is abridged.

In this state, the output voltage of each hydrogen sensor22is read by the unit main body40depicted inFIG. 6to determine whether the presence or absence of external leakage of hydrogen from the test valve1to complete the pressure-resistance inspection. After completion of the pressure-resistance inspection, the exhaust fan32is operated, and also the servo motors23are rotated in reverse to cause the hydrogen sensors22to be retracted to their original positions before the pressure-resistance inspection in a departing direction of the test valve1. Furthermore, the pressurization valve67inFIG. 5is operated to be in a closed state and the exhaust valve69is operated to be in an open state, thereby exhausting the mixture gas from the inside of the test valve1via the exhaust flow path64from the communication hole55.

Subsequently to this, inFIG. 5, the ventilation valve71is caused to be in an open state, thereby blowing air from the air pressure source70for ventilation of the inside of the valve via the ventilation-side flow path62from the through hole52to remove the mixture gas left inside the test valve1. This prevents the inside of a chamber20from being filled with the gas left inside the test valve1when the clamp member50is removed from the test valve1inFIG. 7.

As these described above, after inspection, the mixture gas left inside the chamber20is forcibly exhausted by the exhaust fan32and the mixture gas left inside the test valve1is forcibly exhausted by the exhaust flow path64. This can discharge this hydrogen gas with diffusibility quickly from the inside of the test valve1and the inside of the chamber20even when the mixture gas containing hydrogen gas is taken as a search gas as in the present embodiment. Thus, an automation of the pressure-resistance inspection can be made by which the mixture gases are successively supplied to and discharged from inside the different test valves1, and accurate pressure-resistance inspection results can also be acquired.

After ventilation inside the test valve1, while the open state of the exhaust valve69ofFIG. 5is maintained, the ventilation valve71is operated to be in a closed state to cause the inside of the flow path of the pressure-resistance inspection facility60to be in an atmospheric pressure state, and then the chamber20is caused to ascend as depicted inFIG. 7(b).

Finally, inFIG. 7(a), the clamp member50is caused to ascend to release the contact with the upper flange part10, thereby allowing the test valve1to be removed. After removal of the test valve1, the pressure-resistance inspection apparatus becomes in an initial state, thereby allowing pressure-resistance inspection for another test valve1successively as described above. Here, the exhaust fan32may be stopped, or the exhaust fan32may be continuously operated successively to inspection on another test valve1.

The valve pressure-resistance inspection in the present embodiment complies with, for example, an air-pressure test in valve-box pressure-resistance inspection defined in JIS B 2003 (General rules for inspection of valves). In the test valve1made of cast iron with a nominal pressure of 10 K and a nominal diameter equal to or smaller than 50 A, the test valve1in a valve-open state is filled with the above-described mixture gas at a test pressure of 0.6 MPa, and this test pressure is kept for fifteen seconds as a test time to sense the presence or absence of external leakage from the test valve1by the hydrogen sensors22.

Next, the mechanism in the above-described embodiment of the pressure-resistance inspection apparatus for valves of the present invention is described.

The pressure-resistance inspection apparatus for valves of the present invention has the cover20which accommodates the test valve1in a state of being isolated and hydrogen sensors22capable of moving to a position close to the outer surface of the test valve1inside this cover20, and detects external leakage of hydrogen from the test valve1by this hydrogen sensors22. Therefore, at the time of pressure-resistance inspection, even when the type, the nominal pressure, the nominal diameter, and so forth of the valve serving as the test valve1are varied to vary the shape and the size, the hydrogen sensors22can be reliably made close to a portion where external leakage tends to occur and the occurrence of leakage and its position of occurrence can be quickly detected. In this case, by adjusting the angle of each servo motor23to make the hydrogen sensor22close to the outer surface of the test valve1to the utmost, detection accuracy is improved, and also the detection time is reduced. Since external leakage is checked by mechanical automatic detection including the hydrogen sensors22, pressure-resistance inspection can be performed with a simple structure by the pressure-resistance inspection facility60using the pressure-resistance inspection apparatus without requiring skills, while reducing errors. Also without requiring post-treatment, automation of pressure-resistance inspection achieves efficiency, thereby allowing mass processing and also improving inspection accuracy.

Furthermore, the mixture gas of 5% hydrogen and 95% nitrogen is used as a mixture gas. Thus, when externally leaked, this mixture gas tends to be retained in the retention region R near the joint portion between the body part2and the cover part3near the flange parts10,10disposed at upper and lower positions and near the attachment portion of the gland member8. Since three hydrogen sensors22are provided to each arc-shaped plate member21so as to surround this retention region R, inspection is performed while these six hydrogen sensors22in total are controlled, thereby allowing an improvement in capability of detecting leaked hydrogen and also reduction in detection time.

To automate pressure-resistance inspection, for example, while vertical movements of the cover (chamber)20having the upper side plate30attached thereto and the clamp member50are controlled, the plate member51(lower side plate31) having the test valve1mounted thereon is successively supplied by a conveyor not depicted to a pressure-resistance inspection performing position provided with these chamber20and clamp member50. This allows mass pressure-resistance inspection in a short time while the pressure-resistance inspection facility is simplified.

Depicted inFIG. 8andFIG. 9is a globe valve80, which is another test valve for the pressure-resistance inspection apparatus for valves of the present invention. In the drawings, the glove valve80has a body part81and a bonnet part82. This bonnet part82is inserted into the body part81, while a stem84having a disk83is screwed into the bonnet part82. Above the bonnet part82, a cap part85is screwed. This cap part85seals the inside of the bonnet part82.

In the case of the above-described globe valve80, there is a high possibility that hydrogen leakage occurs from each of screw parts between the body part81and the bonnet part82and between the bonnet part82and the cap part85. Thus, when the globe valve80is a test valve, it is only required as follows. As depicted inFIG. 8, the valve is mounted on the plate member51ofFIG. 1as the stem84is in an upwardly-oriented state and, as depicted inFIG. 9(a)andFIG. 9(b), the hydrogen sensor22is provided at each of four locations on the periphery of the body part81and the bonnet part82and at one location on an upper side of the bonnet part82and the cap part85. Each of these hydrogen sensors22is made close to an inspection position on the outer surface of the test valve80by rotation of the servo motor23.

In this case, a portion near the screw portion of the cap part85is covered with an annular member86from above to form the retention region R near a bottom surface side of this annular member86. With the inner peripheral side of the annular member86being provided so as to have a diameter substantially equal to the outer diameter of the cap part85, hydrogen leaked out mainly from the screw part between the body part81and the bonnet part82of the globe valve80is easily retained in the retention region R, and this hydrogen is sensed by the hydrogen sensors22at four locations on a bottom surface side of the annular member86. Furthermore, by the hydrogen sensor22at one location on an upper side from the cap part85, hydrogen leaked out from mainly from the screw part between the bonnet part82and the cap part85is sensed.

With this, as with the case of the above-described ball valve1, pressure-resistance inspection is possible in a state in which the test valve80is accommodated inside the cover20ofFIG. 1. In the present embodiment, the hydrogen sensors22are each attached to the servo motor23fixed to the annular plate member86. Note that the stem84allows valve opening/closing operation by a nut runner (not depicted) or the like via a center hole of the annulare plate member86.

In this manner, the number, the mount position, and the height of the hydrogen sensors22can be changed as appropriate in accordance with the test valve as a target, thereby allowing pressure-resistance inspection to be appropriately performed in accordance with the test valve of different specifications.

While the embodiments of the present invention have been described in detail in the foregoing, the present invention is not limited to the description of the above embodiments, and can be variously modified in a range not deviating from the spirit of the invention described in claims of the present invention. For example, the present invention can be applied to pressure-resistance inspection for a valve box of any of various valves such as a ball valve, globe valve, gate valve, and check valve, and may also be applied to pressure-resistance inspection for plumbing equipment such as a strainer or any of various pressure vessels.

REFERENCE SIGNS LIST