JPS62163946A - Airtightness inspection of capsule - Google Patents

Abstract

PURPOSE:To enable the inspection of airtightness of a capsule simply and with high accuracy, by a method wherein a capsule is housed into a pressure container, then, the internal pressure of a pressure vessel is changed sharply and changes in the internal pressure of the pressure container is detected immediately after this sharp change. CONSTITUTION:A capsule 15 is housed in a pressure container 1, a valve 6 for introducing gases is opened quickly to introduce a high pressure gas in the pressure container 1 and then, the valve 6 is closed. As a result, the internal pressure V of the pressure container 1 is changed sharply from a pressure Va to a specified pressure Vb. Under such a condition, the pressure container is allowed to stand for a fixed time T. When the airtightness is not complete because of a fine hole existing in the capsule 15, the internal pressure V of the pressure container 1 lowers gradually from said Vb. The changes in the internal pressure V of the pressure container 1 are detected with a pressure sensor 10 to be recorded on a recorder 12. Thus, depending on the recorded waveform of the recorder 12, it can be judged whether the capsule 15 is sealed completely airtight or not.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for testing the airtightness of capsules used in hot isostatic pressing and the like.

(Prior art and its problems) Hot isostatic pressing (hereinafter referred to as HIP) is a method of pressing powder in a high temperature and high pressure gas atmosphere to solidify the powder. Even if a molded body of metal powder is pressurized as it is in the high-temperature, high-pressure gas atmosphere, the gas will enter the molded body, and as a result, the gas pressure will only compress the individual powders. However, since the powders are not pressed together, the compact cannot be solidified. Therefore, an airtight container (hereinafter referred to as a capsule) is usually formed to match the shape of the molded product.
After filling the can with powder and evacuating it, the capsule is pressurized in the high temperature and high pressure gas atmosphere to perform HIP treatment.
I'm trying to harden it.

The capsule used in the HIP process needs to be completely airtight, and if the capsule has an extremely small hole during molding, for example due to poor welding, the high-pressure gas can be passed through the hole. Not only will the HIP process not be possible as described above, but also the capsule will burst due to its internal pressure when the external pressure of the capsule drops, potentially damaging the HIP process apparatus. Furthermore, HIP processing requires a large amount of cost, and a failure in HIP processing is a major mistake.

Therefore, we are inspecting whether the HIP processing power pack is completely airtight. There are various methods for testing the airtightness of capsules, but a common method is to introduce gas at several atmospheres into the capsule and check for gas leaks using soap solution or the like.

Although this airtight inspection method is simple, it is necessary to seal the gas inlet with welding, as well as the HIP processing power.
It is impossible to test the airtightness of the capsule by sealing and welding, and there is a problem in that the final airtightness test of the capsule cannot be performed.

The present invention has been made to solve the above problems,
It is an object of the present invention to provide a method for testing the airtightness of a capsule, which allows the airtightness of the capsule to be tested easily and with high precision.

(Means for Solving the Problems) In order to achieve the above object, according to the present invention, a capsule whose inside is hermetically sealed is housed in an airtight pressure vessel, and the internal pressure of the pressure vessel is suddenly changed. , a method for detecting the airtightness of a capsule in which the airtightness of the capsule is determined by detecting a change in the internal pressure of the pressure vessel immediately after the sudden change; Provided is a capsule airtightness inspection method in which the gas pressure of a gas whose molecular weight is smaller than that of air is suddenly changed to be filled into a container, and immediately after the sudden change, a change in the internal pressure of the pressure vessel is detected to determine the airtightness of the capsule. .

(Example) An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows an inspection apparatus for carrying out the method of the present invention,
The pressure vessel 1 consists of two bottomed cylindrical vessels 2.3, an upper and a lower one, and each open end of each vessel 2.3 has a flange 2a,
3a is formed, and the container 2 is placed on the flange 3a of the container 3 via the flange 2a, and each of these flanges 2a, 3a is firmly screwed at multiple locations with bolts 5 via the seal member 4. be done. Pressure vessel 1 consists of these two
The two containers 2 and 3 and the sealing member 4 form a completely airtight structure.

A gas introduction valve 6 is connected to a predetermined location on the peripheral wall 3b of the lower container 3 in a gas-tight manner and communicates with the container 3, and the valve 6 is connected to a high-pressure gas cylinder 8 via a pipe 7. Further, a gas release valve 9 is connected to the inside of the container 2 and fixed in an airtight manner approximately at the center of the upper surface 2b of the upper container 2. Further, a pressure sensor 10 is airtightly mounted at a predetermined location on the peripheral wall 3b of the lower container 3, with its detection portion facing into the container 3. High pressure gas from high pressure gas pump 8 is supplied by valve 6
It is introduced into the pressure vessel 1 through the valve 9 and released outside the pressure vessel 1 through the valve 9. This high pressure gas is
In order to easily enter the Rakugai capsule 15 through the minute holes of the capsule 1 described later, an inert gas having a molecular weight smaller than that of air is preferable, and for example, helium gas is used. Further, the pressure of the gas is set to about 4 to 5 atmospheres, for example.

The output of the pressure sensor IO is applied to an electric pressure gauge 11, and the output of the electric pressure gauge 11 is applied to a recorder 12. The pressure sensor 1o outputs an electric signal according to the pressure to be detected, the electric pressure gauge 11 indicates the pressure according to the input signal and outputs a pressure signal, and the recorder 12 records the output pressure signal. .

The capsule 15 is, for example, a cylindrical, airtight container filled with a powder to be solidified, such as the powdered powder 2o.

A method for testing the airtightness of the capsule 15 will be described below.

First, the capsule 15 is housed in the pressure vessel 1, each bolt 15 is tightened, and the gas release valve 9 is closed.
The pressure vessel 1 is hermetically sealed.

Next, the gas introduction valve 6 is rapidly opened to rapidly introduce high pressure gas into the pressure vessel 1, and then the valve 6 is closed. As a result, the internal pressure V of the pressure vessel 1 rapidly changes (increases) from the pressure Va (approximately atmospheric pressure) before the introduction of the high-pressure gas to a predetermined pressure Vb (>Va), as shown in FIG.

The device is kept in this state for a certain period of time T. If the capsule 15 is completely hermetically sealed, the high pressure gas introduced into the pressure vessel 1 will not enter the capsule 15, and therefore the internal pressure of the pressure vessel 1 will be equal to the pressure Vb.
(Fig. 2).

If there are minute holes in the capsule 15 and the airtightness is incomplete, high-pressure gas will enter the capsule 15 through the hole, and as a result, as shown in FIG. 2(b), Then, the internal pressure (2) of the pressure vessel 1 gradually decreases from the value vb.

After the predetermined time T has elapsed, the gas release valve 9 is rapidly opened, and the high pressure gas in the pressure vessel 1 is released from the pressure vessel 1.
The pressure inside the pressure vessel 1 is rapidly lowered to the pressure Va, and then the valve 9 is closed. When the capsule 15 is completely hermetically sealed, the internal pressure V of the pressure vessel 1 is maintained at the pressure Va after the drop, as shown in FIG. 2(a). However,
If the capsule 15 is not airtight as described above, the high-pressure gas that has entered the capsule 15 leaks out of the capsule 15 due to a drop in the external pressure of the capsule 15, that is, the internal pressure of the pressure vessel 1, and Along with this, pressure vessel 1
The internal pressure (2) gradually increases from Va as shown in FIG. 2(b).

Changes in the internal pressure V of the pressure vessel 1 are detected by a pressure sensor 10 and displayed by a pressure gauge 11, as well as by a recorder 1.
2 is recorded as a waveform change as shown in FIG. 2(a) or (b). Therefore, from the waveform recorded by the recorder 12, it can be determined whether the capsule 15 is completely hermetically sealed. That is, when the recorded waveform of the recorder 12 is as shown in FIG. 2(a), it is determined that the capsule 15 is completely hermetically sealed, and when it is as shown in FIG. 2(b), it is determined that the hermetic seal is incomplete.

Note that by reducing the difference in internal volume between the pressure vessel 1 and the capsule 15, it becomes possible to increase the internal pressure change of the pressure vessel 1 shown in FIG. 2(b), and the above-mentioned discrimination becomes easy.

Furthermore, although the present embodiment describes the case where helium gas is used, the present invention is not limited to this, and other gases such as hydrogen gas may also be used.

(Effects of the Invention) As explained above, according to the present invention, a capsule whose inside is hermetically sealed is stored in an airtight pressure vessel, the internal pressure of the pressure vessel is suddenly changed, and immediately after the sudden change, the pressure is Since the airtightness of the capsule is determined by detecting changes in the internal pressure of the container, it is possible to simply and easily test the airtightness of the capsule. Furthermore, a capsule whose inside is hermetically sealed is stored in an airtight pressure vessel, and the gas pressure of a gas whose molecular weight is smaller than that of air is filled into the pressure vessel, and immediately after the sudden change, the pressure of the gas is filled into the pressure vessel. The airtightness of the capsule is determined by detecting changes in the internal pressure of the capsule.
This method has an excellent effect in that it is possible to determine the presence or absence of extremely minute holes in the capsule, and the airtightness of the capsule can be determined with extremely high precision.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of an inspection device for carrying out the capsule airtightness inspection method according to the present invention, and FIG. 2 is a graph showing an example of internal pressure changes in a pressure vessel in the inspection device of FIG. 1. It is. DESCRIPTION OF SYMBOLS 1... Pressure vessel, 6, 9... Valve, 8... High pressure gas pump, 10... Pressure sensor, 11... Electric pressure gauge, 12... Recorder.

Claims (1)

[Claims] 1. A capsule whose inside is hermetically sealed is stored in an airtight pressure vessel, the internal pressure of the pressure vessel is suddenly changed, and the change in the internal pressure of the pressure vessel is detected immediately after the sudden change. A method for testing the airtightness of a capsule, the method comprising determining the airtightness of the capsule. 2. The sudden change in the internal pressure of the pressure vessel is detected by rapidly introducing high-pressure gas into the pressure vessel, and detecting the change in the internal pressure of the pressure vessel immediately after the introduction of the high-pressure gas is completed. A method for testing the airtightness of a capsule according to scope 1. 3. A capsule whose inside is hermetically sealed is stored in an airtight pressure vessel, and the pressure of a gas whose molecular weight is smaller than that of air is filled into the pressure vessel, and the pressure of the gas is suddenly changed, and immediately after the sudden change, the pressure vessel is 1. A method for testing the airtightness of a capsule, the method comprising determining the airtightness of the capsule by detecting changes in the internal pressure of the capsule.