JPS63121000A - Method for supplying pressure to container - Google Patents

Abstract

PURPOSE:To aim at improvement in operating efficiency by making fluid pressure in a container be under the balanced condition at the speed more then natural transition speed. CONSTITUTION:First, a fluid pressure source 1 and a container 2 are connected to each other, and an initial pressure, whose absolute value is greater then that of a set pressure, is applied into the container 2. Next, the container 2 is disconnected from the fluid pressure source 1, the pressure in the container 2 is released outward from the container 2 so that the absolute value is reduced, thereby resulting in the set pressure in the container 2. With this constitution, fluid temperature in the container 2 becomes a balanced condition with outer temperature at the speed more than natural transition speed, so that the stable set pressure can be obtained in a short time, thereby improving operating efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) This invention relates to a method for supplying a stable set pressure within a container.

(Prior Art) Generally, a leak test is performed to check whether a container has cracks or the like.

In this leak test, the inside of the container is pressurized (hereinafter referred to as the pressurization method) or depressurized (hereinafter referred to as the depressurization method).
After setting the test pressure (set pressure) inside the container, the container is closed from the fluid pressure source, and subsequent pressure fluctuations inside the container are detected with a pressure gauge or the like. In the pressurization method, if the pressure decreases, it is assumed that gas is leaking from the container.
In the depressurization method, if the pressure increases, it is determined that there is a leak.

FIG. 6 and FIG. 17 are graphs showing the pressure fluctuations in the container over time in the case of the leak test using the conventional pressurization method and the leak test using the depressurization method, respectively, and these graphs will be explained below.

In the case of the pressurization method, the test pressure pt is reached one hour after the start of pressurization. At this time, the temperature of the gas inside the container rises above the outside air temperature due to the pressurization. therefore,
When the container is closed from the fluid pressure source immediately after the above-mentioned time t1 has elapsed, that is, immediately after the test pressure Pt is reached, heat is radiated from the container to the outside air and the temperature of the gas inside the container decreases.
The pressure inside the container is approximately 60% even if there is no leakage of gas from the container.
It decreases as shown by solid line A in the figure, and stabilizes after time t1 has elapsed. Furthermore, after the pressure inside the container reaches the test pressure Pt, if the container is kept connected to the pressure source until time t2 or time t1 and the inside of the container is maintained at the test pressure pt, and then the container is closed, the amount of pressure drop will be Although it decreases, the pressure inside the container decreases as shown by solid line aB and solid line C, respectively, and stabilizes at time t1. When the container is closed after the pressure inside the container is maintained at the test pressure pt until time t4, the pressure fluctuation disappears because the gas temperature inside the container has already reached an equilibrium state with the outside temperature.

In the case of the reduced pressure method, a phenomenon opposite to that in the above-mentioned pressurized method occurs. That is, after t+' time elapses from the start of depressurization, the test pressure P
t' is reached. At this time, the temperature of the gas inside the container is lower than the outside temperature due to the reduced pressure. Therefore, if the container is closed from the fluid pressure source immediately after one hour has elapsed, i.e., immediately after the test pressure Pt' has been reached, the container will absorb heat from the outside air and the temperature of the gas inside the container will increase, resulting in an increase in the temperature of the gas inside the container. The pressure increases as shown by the solid line A' in FIG. 7, and stabilizes after t41 hours have elapsed. In addition, after the pressure inside the container reaches the test pressure Pt', the container is maintained at the above test pressure Pt' with the container as the pressure source for t21 hours or E', and then the container is closed. ,
The pressure inside the container rises as shown by solid line B' or solid line C', respectively, and stabilizes at t and 7 hours.

Then, test the pressure inside the container at t 41 hours at a pressure P
When the container is closed after being maintained at t', the gas temperature within the container has already reached an equilibrium state with the outside temperature, so there is no pressure fluctuation and the pressure remains constant.

As is clear from the above explanation, if a leak test is performed with the container closed before t4 hours or t<' hours, there will be natural pressure fluctuations due to temperature changes of the gas inside the container, and pressure fluctuations due to leakage from the container. are detected at the same time, making it difficult to accurately determine the presence or absence of a leak.

Therefore, in reality, the container is closed until time t1 or time t41, that is, when the temperature inside the container is in equilibrium with the outside temperature and after the container and pressure source are communicated and the test pressure PL is maintained. to detect pressure fluctuations and ensure accuracy in leak tests.

(Problems to be solved by the invention) As mentioned above, since the leak test is performed after waiting until the temperature inside the container naturally equilibrates with the outside temperature, the leak test takes a long time and efficiency is reduced. It was bad.

(Means for Solving the Problems) This invention has been made to solve the above problems, and its gist is that first, a fluid pressure source and a container are connected,
By applying an initial pressure in the container that is greater in absolute value than the set pressure, then isolating the container from the fluid pressure source and releasing the pressure in the container to the outside of the container to reduce its absolute value,
A method of supplying pressure to a container, characterized by bringing the inside of the container to a set pressure.

(Function) First, an initial pressure that is greater in absolute value than the set pressure is applied inside the container, and then the pressure inside the container is released to the outside of the container to reduce the absolute value to reach the set pressure.
The temperature of the fluid inside the container reaches an equilibrium state with the outside temperature faster than its natural course, and the temperature inside the container becomes stable in a short period of time, making it possible to obtain a stable set pressure in a short period of time. can.

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings from FIG. 1 to FIG. 3.

FIG. 1 shows a schematic 70-G diagram when performing a leak test using the pressurization method of the present invention. A regierator 3, a pressure gauge 4, a solenoid valve S1, a pressure switch 5, and a solenoid valve S V s are arranged in the middle of a piping line 11 that connects a pressurized air source 1 (fluid pressure source) and a container 2 at both ends. has been done. These solenoid valves sv, , sv are for shutting off or opening communication between the pressurized air source 1 and the container 2. The piping line 11 has a branch piping line 12.13 between the solenoid valve S1 and the pressure switch 5, and the branch piping line 12 is provided with an exhaust solenoid valve S4, and the branch piping line 13 is a solenoid valve S for pressure relief.
V 2 and a throttle valve 6 are arranged.

Further, a pressure sensor 7 is connected to the piping line 11 between the solenoid valve SV and the container 2 via a branch piping line 14. This pressure sensor 7 is a diaphragm (not shown)
The deformation of this diaphragm is electromagnetically detected, and a port on one side of the diaphragm is connected to the branch piping line 14, and a port on the other side is open to the atmosphere.

The electromagnetic valves sv, sv, sv, svl and the pressure switch 5 are sequentially controlled. Note that before pressurization, the pressure inside the container 2 is equal to the outside air pressure.

Next, the leak test procedure will be explained in chronological order according to the time chart shown in Fig. vJ2 and the pressure transition graph shown in Fig. 3.

One cycle of the leak test consists of a pressurization process, a depressurization process, a first equilibrium process, a second equilibrium process, a detection process, and an exhaust process. The required time T2, the second equilibrium process time T1, the detection process time T4, and the exhaust process time T are set by a timer.

In the pressurizing process, the solenoid valves SV, SV3 are in the open state, and the solenoid valves sv2. sv is in a closed state.

As a result, pressurized air from the pressurized air source 1 is transferred to the piping line 1.
1, the pressure is reduced to the initial pressure Po by the regulator 3, and the pressure is supplied to the container 2. The pressure inside the container 2 gradually increases and exceeds the test pressure pt, and reaches the initial pressure PO after a time QTa has elapsed since the start of pressurization. During the remaining time Tb of the pressurization process, the pressure inside the container 2 is the initial pressure PoI:
It will be held for m.

The H contact (High contact) of the pressure switch 5 is set to be larger than the test pressure Pt and slightly smaller than the initial pressure PO, and when this H contact is turned ON, the pressure inside the container 2 reaches the test pressure pt. If the above conditions are confirmed and the 1000-H contact is not turned on, the leak test will not proceed to the next step.

At the same time as the above pressurization process ends, solenoid valve S■ remains open, solenoid valve S■ closes, and at the same time solenoid valve S■2
opens and moves on to the depressurization process.

The container 2 is closed off from the pressurized air source 1 by the solenoid valve SV1, the supply of pressurized air to the container 2 is stopped, and the air stored downstream of the solenoid valve S is transferred to the branch piping line 13. , and is discharged to the outside air from the solenoid valve SV2 and the throttle valve 6, and the pressure inside the container 2 gradually decreases.

When the pressure drops to the test pressure Pt*, the L contact (Low contact) of the pressure switch 5 is turned on, the solenoid valve S2 is closed, and the process shifts to the first equilibrium step.

In the first equilibrium step, only the solenoid valve S3 is open. At the end of the first equilibrium process, the solenoid valve S V 3 is also closed, and the process moves to the second equilibrium process.

In the above-mentioned first equilibrium step and second equilibrium step, the pressure inside the container 2 is stable and the test pressure Pt is maintained.

The time required to obtain the stable test pressure Pt, that is, the total time of the pressurization process time and the depressurization process time, is much shorter than the time t4 required to obtain the stable test pressure Pt in the conventional method.

The reason is presumed to be as follows.

The air temperature inside the container 2 reaches the initial pressure Po immediately after the start of pressurization.
and the initial pressure P. The time T
It goes down in b. However, since this time Tb is short, the temperature does not drop until it reaches equilibrium with the outside temperature.

In the next depressurization step, pressurized air is released, and the air temperature inside the container 2 is lowered by this release and brought into equilibrium with the outside air temperature. In this way, the temperature inside the container 2 is forcibly brought into equilibrium with the outside air temperature without waiting for natural heat dissipation, so that a stable test pressure Pt can be achieved in a short time.

After the second equilibration step, a detection step is performed. That is,
The pressure inside the container 2 is led to the pressure sensor 7 by a branch piping line 14, and is detected as a dage pressure relative to the outside air pressure. Note that the electrical signal of the detected pressure from the pressure sensor 7 is amplified and sent to the pressure gauge, and the gauge pressure is displayed on this pressure gauge. If there is no change in this gauge pressure, the sealing performance of the container 2 is confirmed, and if the gauge pressure is decreasing, air is leaking from the container 2, and poor sealing performance is confirmed. After the above detection process is completed, the process moves to the exhaust process. In the exhaust process, the solenoid valves S2, SV are opened, and the air inside the container 2 is discharged through the branch piping line 12.

This completes one cycle of the leak test, and the time required for one cycle can be reduced to about 1/3 compared to the conventional method described above.

In addition, in order to stabilize the air pressure in the container 2 immediately after the pressure reduction step in the above embodiment, the pressure difference ΔP1 between the initial pressure Po and the test pressure pt and the maintenance time Tb of the initial pressure Po are required.
must be set within a specified range.

If the differential pressure ΔP is larger than the upper limit of the predetermined range, the temperature inside the container 2 due to depressurization will decrease too much and temporarily drop below the outside temperature. The pressure will rise until the air temperature reaches equilibrium with the outside air temperature, and the detection process cannot be performed until the pressure stabilizes. Furthermore, if the differential pressure ΔP is smaller than the lower limit of the predetermined range, the temperature inside the container 2 due to depressurization will not be reduced enough to reach the outside temperature.
After the container 2 is closed, the pressure decreases until the air temperature within the container 2 reaches equilibrium with the outside temperature, and the detection step cannot be performed until the pressure stabilizes.

Similarly, if the above-mentioned maintenance time Tb is longer than the upper limit of the predetermined range, the temperature of the air inside the container 2 decreases so much during this maintenance time Tb that it approaches the outside temperature, so that the temperature inside the container 2 decreases in the next pressure reduction step. The temperature drops below the outside temperature. For this reason, after the end of depressurization, that is, after the container 2 is closed, the pressure increases until the air temperature inside the container 2 reaches equilibrium with the outside temperature.
The detection process cannot be performed until the pressure stabilizes. In addition, if the maintenance time Tb is shorter than the lower limit of the predetermined range, the temperature drop inside the container 2 during this maintenance time Tb is very small, and the temperature inside the container 2 due to the next pressure reduction will not drop to the outside temperature. , after the completion of decompression, that is, after closing the container 2.
The pressure will drop until the internal air temperature reaches equilibrium with the outside temperature, and the detection process cannot be performed until the pressure stabilizes.

The differential pressure ΔP and the maintenance time Tb have a mutual relationship.

That is, if the differential pressure ΔP is increased, the opening time Tb during maintenance is shortened, and if the differential pressure ΔP is small, the maintenance time Tb must be lengthened. Increase the initial pressure Po and increase the differential pressure ΔP
It is preferable to shorten the test time by increasing Po.

ΔP is determined depending on the strength of the container 2, etc.

Note that the P9m duration time Tb described above may deviate from the above range to some extent (although in this case, the test time will still be longer than the ideal case (although it can be shorter than the conventional method).

In addition, Figure @4 shows a 70-Giagram of another example, and parts that are the same as those of the first example are given the same reference numerals and explanations are omitted, and points that are different from the first example are noted. This will be explained below.

Downstream from the pressure switch 5, the piping line 11 is divided into two piping lines lla and 11b, and each piping line lla and llb is provided with a solenoid valve S3. These two solenoid valves SV are both opened and closed in the same manner as the solenoid valve S■ of the first embodiment. Container 2 is connected to one piping line lla as a container, and the capacity piping line flb is connected to a container of the same size and material as the above-mentioned container, which has been confirmed in advance to be leak-free. A reference container 2' is connected. Further, the downstream side of the solenoid valve S■ of each piping line lla, llb is connected to both the cover of the pressure sensor 7 via the branch piping lines 14a, 14b, and this pressure sensor 7 is connected to the differential amplifier 8. It is connected to the differential pressure gauge 9 via.

The time chart and pressure transition graph in the second embodiment are the same as those in the first embodiment. However, in the detection process, the pressure in the container 2 and the piping lines 11a, 14a is detected by the pressure sensor 7 as a differential pressure with the pressure in the reference container 2' and the piping lines llb, 14b, and is displayed by the differential pressure gauge 9. Since differential pressure detection is used as described above, detection can be performed with high sensitivity. Note that the reference container 2' has the same dimensions as the container 2, and can offset pressure fluctuations caused by external factors; however, when this external factor is small, the reference container 2' has the same dimensions as the container 2.
' can be omitted.

FIG. 5 shows a third embodiment of the invention. In this example,
A two-way solenoid valve S<b>5 for exhaust is provided in the piping line 11 on the downstream side of the pressure switch 5 . This solenoid valve S
The piping line 11 between V 5 and the pressure switch 5 includes:
An orifice 16 is provided, and this orifice 16
The pressure difference on both sides is detected by a sensor 7 via branch piping lines 17a and 17b, and the output of the sensor 7 is amplified by a differential amplifier 8 and displayed by a differential pressure gauge 9.

Further, a bypass line 18 is connected to the piping line 11 in parallel with the orifice 16, and this bypass line 18 is provided with a solenoid valve S6.

In the third embodiment, with the container 2 connected to the connection port at one end of the piping line 11, the exhaust electromagnetic valve S V s is brought into communication between the container 2 and the pressurized air source 1. In this state, pressurization and depressurization steps are performed in the same manner as in the previous embodiment, and the inside of the container 2 is brought to a stable test pressure Pt in a short time.

Thereafter, the solenoid valve S5 is switched from open to closed to close the bypass line 18 and start the detection process. If there are no cracks or the like in the container 2 and there is no leakage of pressurized air, no air will flow through the orifice 16 and no pressure difference will occur between its ends, so the differential pressure gauge 9 will display zero. If there is a leak from the container 2, air will flow through the orifice 16, creating a pressure difference between both ends equal to the pressure loss at the orifice 16.

This is displayed on the differential pressure gauge 9 to notify the user of a leak. In addition, if the leakage is large, the tank 19 connected to the piping line 11
Supplement with pressurized air.

After the above detection, the solenoid valve Svs is switched to discharge the pressurized air inside the container to the outside.

Although the first, second, and third embodiments described above are explained using a leak test using a pressurization method, a leak test using a depressurization method can also be performed based on the same idea. In the case of the reduced pressure method, a negative pressure air source is used in place of the pressurized air source 1 in FIGS. 1, 4, and 5, but other configurations and operations are the same as in the pressurized method. In detail, the container is connected to a negative pressure air source, the inside of the container is set to below the test pressure, and after this state is maintained for a certain period of time, the container is cut off from the negative pressure air source and outside air is introduced into the container. It is sufficient to increase the pressure to a test pressure, and after a certain period of time has elapsed, detect whether or not fluid has flowed into the negative pressure container. In this method, the temperature of the fluid in the container rises during the pressure increase and reaches equilibrium with the outside temperature in a short time, resulting in a stable test pressure. The change in pressure due to this pressure reduction method can be expressed by making the vertical pongee a negative pressure in FIG.

Also, as shown by the imaginary lines in Figures 1, 4, and 5,
A cylinder 21 having a built-in piston 20 may be connected to the piping line 11 instead of the solenoid valve S2. In the case of the pressurization method, the rod 22 connected to the piston 20 is pulled in the pressure reduction step (in the case of the pressure reduction method, the rod 20 is pushed in the pressure increase step).

This invention is not limited to the above-mentioned embodiments, and various embodiments are possible. For example, the fluid is not limited to air, but may also be nitrogen gas or a liquid such as water or oil.

In addition, the present invention can be used in leak test ponds when it is required to stabilize the pressure supplied into the container in a short time.
Can be applied.

(Effects of the Invention) As explained above, according to the present invention, the pressure of the fluid in the container reaches an equilibrium state faster than the natural transition, and it is possible to achieve a stable set pressure in a short time. is possible,
Work efficiency improves.

[Brief explanation of the drawing]

The drawings from FIG. 1 to FIG. 3 show an embodiment of the leak test method according to the present invention, and FIG.
0-diagram, FIG. 12 is a time chart, and FIG. 3 is a pressure transition graph. Further, FIGS. 4 and 5 schematically show 7r:1-7g of other embodiments that are different from each other. Furthermore, FIGS. 6 and 7 are graphs of pressure changes in the conventional pressurization method and the conventional leak test method using the depressurization method.

Claims (3)

[Claims] (1) First, connect the fluid pressure source and the container to apply an initial pressure larger in absolute value than the set pressure in the container, and then,
A method for supplying pressure to a container, characterized in that the pressure inside the container is brought to a set pressure by isolating the container from a fluid pressure source and releasing the pressure inside the container to the outside of the container to reduce its absolute value. (2) The set pressure mentioned above is positive pressure, and the inside of the container is first pressurized to an initial pressure higher than the set pressure, and by releasing a part of the pressurized fluid from the container, the inside of the container is changed from the initial pressure to the set pressure. A method for supplying pressure to a container according to claim 1. (3) The set pressure is a negative pressure, and the pressure inside the container is first reduced to an initial pressure lower than the set pressure, and by introducing fluid into the container, the pressure inside the container is changed from the initial pressure to the set pressure. A method for supplying pressure to a container according to scope 1.