JPH02236134A - Integrity evaluation for tube or container - Google Patents

Abstract

PURPOSE:To curtail time and expense for evaluation by comparing a change pattern of a leakage flow rate measured by varying a pressure of a pressure fluid introduced into a tube to be tested or in a container to be tested with a change pattern prepared beforehand to evaluate a pressure resistance. CONSTITUTION:A tube 1 to be tested with both ends thereof sealed, for example, a gas pipe buried underground is divided to a length of 100m and after a cutting thereof, both cut parts are sealed. A gas is forced into the pipe via a pipeline 6 from a pressure source 2 and a pressure thereof is set to a pressure set with a governor 3 to measure the pressure with a pressure detector 4. A gas pressure from the pressure source 2 is loaded gradually to detect leakage flow rates from a underground buried tube 1 at pressure points with a flowmeter 5. A change pattern of the leakage flow rate is compared with a change pattern of a leakage value prepared beforehand thereby evaluating an integrity (pressure resistance and durability).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a soundness evaluation method that is carried out to evaluate the soundness of a tube under test or a container under test, such as an underground pipe. In this specification, "integrity" refers to the pressure resistance, durability, etc. of test tubes and test containers. Currently underground pipes are
Items that have been buried for a certain period of time are dug up to evaluate their soundness. However, the state of corrosion of underground pipes varies depending on the environment in which they are buried. Therefore, this method requires digging up many healthy underground pipes, which is wasteful. Therefore, it is necessary to evaluate the soundness of underground pipes while they are still buried, and to select a repair method. Conventionally, in order to evaluate the health of underground pipes, we have installed in-tube televisions inside the underground pipes and used sensors that evaluate the health of the pipes using eddy currents generated by generating magnetic fields. However, these methods cannot be applied when the underground pipe is small in diameter, and are difficult to apply when the underground pipe is bent. In addition, these methods require measurement over the entire area to be evaluated;
Measurement requires a lot of time, effort, and expense.

The purpose of the present invention is to reliably evaluate the integrity of tubes or containers to be tested regardless of their shape or size, and to significantly reduce the time, labor, and expense for assessing the integrity of tubes. Or to provide a method for evaluating the integrity of containers. The present invention prepares in advance a change pattern of leakage flow rate corresponding to a pressure change for each shape, size, and surrounding situation of a leakage part that can be assumed in a tube under test or a container under test,
Connect a pressure fluid supply to the tube or container under test;
Measuring the leakage flow rate in the test tube or test container while changing the pressure of the pressure fluid continuously or stepwise, and the change pattern of the measured leakage flow rate and the prepared change pattern of the leakage flow rate. This is a method for evaluating the integrity of a tube or container, characterized in that the pressure resistance of the tube or container to be tested is evaluated by comparing the . Embodiments of the present invention will be described below based on the drawings. Figure 1 shows the gas pressure P inside the underground pipe 1 in the soil 40.
Figure 1 (a) is a simplified partial cross-sectional view showing the leakage location when 0 kg/m2 is applied, where a hole with a diameter of d (m) is formed in the underground pipe 1 due to corrosion or cracks. This shows corrosion leakage when the pipe pressure is reduced to POkg.
/m2, the pressure near the outside of the pipe is Plkg/m2, and the atmospheric pressure is Pc.
If Dkg/m2, the gas leakage flow rate Qm'/s is:
It is shown in the first equation. ...(1) Here, ρ0 is the gas density in the pipe kg-s2/m', and κ is the adiabatic index. Figure 1(b) shows POkg in underground pipe 1 in soil 40.
The threaded portion is shown when a gas pressure of /m2 is applied. The threaded portion shown in FIG. 1(b) can be approximated to a tube having a length of 1 (m) and a diameter d(m) shown in FIG. 1(C). The leakage flow rate Qm'/s in the case of leakage from the threaded portion, that is, leakage from the joint, is expressed by the second equation. Re indicates Reynolds number. In the first and second equations, P1-ω represents the leakage flow rate Qm'/s assuming that the underground pipe 1 is open to atmospheric pressure. To calculate the leakage flow rate Qm/s by considering the influence of the soil around the underground pipe 1, use the following third equation together with the first or second equation above. Q = (PL-PcX)) 4ff"
・(3)μ Here, μ is the viscosity of the gas in kg-s/m2, and r is the distance from the leak point in m. k represents the permeability coefficient m2 of the soil.

In Figure 2, which will be described later, r=0.05m. For example, k is k = 1.86 x 10 days 2 m2 for clay, and k = 2.79 x 10-'' m2 for sand. Leakage flow rate Qm in the case of corrosion leakage from underground pipe 1 in soil 40
'/s is the pressure near the outside of the pipe P l in the first and third equations.
Leakage flow rate Qm with “kg/m” as a parameter
'/s can be calculated. The leakage flow rate Qm'/s in the case of joint leakage from the underground pipe 1 in the soil 40 can be similarly calculated from the second and third equations. Based on the relationships of the above-mentioned first, second, and third equations, the pipe pressure P O kg / cm 2 as shown in Fig. 2 is calculated.
The relationship between G and leakage flow 1 (1/S) is obtained.The horizontal axis shows the pipe pressure POkg/cm2G, and the vertical axis shows the leakage flow rate Q1/S.
It shows s. Lines 8, 9, 10, and 11 indicate joint leakage when the joint gap is 0.5 mm, 1 mm, 2 mm, and 3 m + n, respectively, and these are changes when assuming that the joint is open to atmospheric pressure. It is. That is, in the case of a joint leak, for example in line 10, when the pipe internal pressure PO is less than point 50, the fluid passing through the gap pipe of the joint is a laminar flow, and in this case, the relationships of the second and third equations hold true.

At a pipe pressure PO greater than point 50, the fluid passing through the gap pipe of the joint becomes turbulent. In the case of this line 10, although it is not shown in FIG. 2, as the pipe internal pressure PO increases further, the flow velocity in the gap pipe of the joint approaches the sonic velocity, and even if the pipe internal pressure PO increases, the leakage flow rate Q will not rise much. In addition, in the case of line 10, it is a change when it is assumed that the atmospheric pressure is open as described above, and line 10a is a change when it is assumed that the underground pipe 1 is in sand. Line 10b shows the change when the underground pipe 1 is assumed to be in clay. Similar characteristics are obtained for lines 8, 9 and l1 as well.

Lines 12, 13, 14.15, 16.1718.19
The diameter of the hole is 0.5mm, 1mm, 2mm, 3mm,
4mm, 5mm. Corrosion leakage of 10 rnm and 2Q m m are shown, respectively, and both of these are changes when it is assumed that the sample is exposed to atmospheric pressure. For example, in the line 18, in the range of the pipe internal pressure PO lower than the point 51, the above-mentioned relationships of the first and third equations hold true. At a pressure PO in the pipe higher than point 51, the leaking fluid approaches the speed of sound, so even if the pressure PO in the pipe increases, the leakage flow rate Q does not increase much. This also applies to the other lines 12 to 17 and 19. line 20,
21, 22, 23, 24, 25.26 have a hole diameter of 1
mm, 2mm, 3mm, 4mm, 5mm. 10mm, 2
Each shows a corrosion leakage of 0 mm, and the changes are based on the assumption that the underground pipe 1 is located in soil with few gaps, such as clay. The change in the clay when the hole diameter is 0.5 mm almost coincides with line 12. line 2728,
29.30.31 has hole diameters of 3mm, 4mm, and 5mm.
, 10 mm, and 20 mm of corrosion A leakage, respectively, and are changes when it is assumed that the underground pipe 1 is located in soil with many gaps, such as sand.

The changes in the sand when the hole diameters are 0.5 mm, 1 mm, and 2 mm, respectively, approximately correspond to line 12.1314. With reference to FIG. 2, lines 8 to 11 indicating joint leakage,
The change pattern of the leakage flow rate is different from lines 12 to 31 indicating corrosion leakage.In the case of joint leakage, there is a proportional relationship between the pipe internal pressure and the leakage flow rate, and the leakage flow rate is a change in the pipe internal pressure. Although it increases as the pressure increases, in the case of corrosion leakage, the leakage flow rate becomes almost constant and does not increase from around a certain pressure. Therefore, it is possible to determine whether the leak in the underground pipe 1 is a joint leak or a corrosion leak based on the difference in the change pattern of the leakage flow rate. Even if both joint leakage and corrosion leakage occur, it is possible to determine which is the main cause of the leakage. The change pattern of the leakage flow rate also differs depending on the size of the leakage part, and especially in this case, the state of corrosion can be determined by considering the magnitude of the pipe pressure and leakage flow rate in the change pattern of the leakage flow rate. Furthermore, by considering the influence of soil, the health of underground pipes can be evaluated more reliably. FIG. 3 is a diagram showing the ellipse of one embodiment of the present invention. A test tube 1 with both ends sealed, such as a gas main or branch pipe buried underground, is divided into sections of approximately 100 m in length, and the underground is excavated at the location where the division is to be performed. After cutting the branch pipe, gas, for example, is injected from the pressure source 2 through the pipe line 6 into the both cut portions of which are sealed. As this conduit 6, for example, an IM station of a customer service lead-in pipe, that is, a supply pipe formed in the underground pipe 1 may be used. The pressure from the pressure source 2 is adjusted to the pressure set by the governor 3. A pressure detector 4 is provided in a pipe line 7 branched from a pipe line 6 between the governor 3 and the underground pipe 1. The pipe line 6 between the governor 3 and the underground pipe 1 includes
A flow meter 5 is provided. The gas pressure from the pressure source 2 is, for example, 0.1 to 10 kg/c.
The load is applied stepwise at several pressure points over m2G, and the leakage flow rate from the underground pipe 1 at each pressure point is detected by the flow meter 5. The reason why the gas pressure is changed stepwise at this time is to detect the leakage flow rate in a stable state at each pressure point. By comparing the change pattern of the leakage flow rate obtained in this way with the change pattern of the leakage flow rate prepared in advance as shown in FIG. 2, the shape of the leakage part can be determined.
In other words, it is possible to determine whether it is a corrosion leak or a joint leak, as well as the condition of the leak location, ie, the size of the leak. FIG. 4 is a diagram showing the configuration of another embodiment of the present invention. A fluid such as gas is pressurized from a pressure source 2 through a pipe line 6 into a tube to be tested, such as an underground pipe 1 similar to the above embodiment, which is sealed at both ends, in the same manner as in the above embodiment. The gas pressure from the pressure source 2 is adjusted to a set pressure by a governor 3 provided in the conduit 6. A valve 32 is provided downstream of the governor 3 in the gas pumping direction. Governor 3 and valve 32
A pipe line 34 branches from the pipe line 6 between
4, a valve 33, a pressure detector 4, a branch pipe 7 for the pressure detector 4, a comparison tank 35, and a differential pressure gauge 36 are sequentially installed downstream in the gas pumping direction. The pipe line 34 is connected to the pipe line 6 between the valve 32 and the underground pipe 1. First, open valves 32 and 33 and apply a predetermined pressure PO.
Next, when the valves 32 and 33 are closed and the amount of pressure drop after time t, that is, the differential pressure between the comparison tank 35 and the tube under test 1 is ΔP, if the internal volume of the underground pipe 1 is VO, then The leakage flow rate Q can be calculated using the following formula. The leakage flow rate was measured at several pressure points that were changed in stages, and the measured leakage flow rate change pattern was compared with the previously prepared leakage flow rate change pattern shown in Figure 2. Evaluate the soundness of 1. This embodiment is effective when the leakage flow rate is relatively small compared to the previous embodiment. Figure 5 is a diagram showing the relationship between the measured pipe pressure and the leakage flow pattern. This figure shows changes in pipe pressure and leakage flow rate measured based on the configuration shown in Figure 3 or Figure 4 above. For example, the soundness of an underground pipe is evaluated based on the change pattern of leakage flow rate shown in Figure 5 and the change pattern of leakage flow rate prepared in advance as shown in Figure 2 above. Depending on the severity, repair methods are selected as follows. In the line 41 of FIG. 5(a), the leakage flow rate increases at a constant rate as the pressure inside the pipe increases.
From this, it can be determined that it is a joint leak, and a method of spraying a sealant on the joint can be applied. Line 42 in FIG. 5(b) shows that when the pressure inside the pipe is high, the rate of increase in the leakage flow rate decreases. Furthermore, by considering the magnitude of the pipe pressure and leakage flow rate, it can be seen that joint leakage and small corrosion leakage with a diameter of 2 mm or less occur. Fifth
Line 43 in figure (c) has an internal pressure of 1 kg/c.
Even if the pressure increases from around m2G, the leakage flow rate remains almost constant and does not increase. Furthermore, by considering the values of the pipe internal pressure and leakage flow rate, it can be seen that small corrosion leaks with a diameter of 2 mm or less occur. In the case of FIGS. 5(b) and 5(C), a method of lining the inner surface of the tube with resin or the like may be applied. The line 44 in FIG. 5(d) is
Even if the pressure increases from around 1kg/cm2G in the pipe, the leakage flow rate remains almost constant and does not increase. Furthermore, the value of the leakage flow rate is larger than that of line 43 in FIG. 5(c). This indicates that a large corrosion leak with a diameter of about 5 mm has occurred. Line 45 in Fig. 5(e) shows that the leakage flow rate increases rapidly from a certain pressure, has no pressure resistance, and has a pressure of 10 kg.
It can be seen that a crack occurred at /cm2G. Figure 5(d)
In the case of Figure 5(e), the pipe body must be dug up and replaced. FIG. 6 is a diagram for explaining the pressure resistance of a tube body according to an embodiment of the present invention. Figure 6 (1) shows that the tube surface has a diameter cross section of 2a.
The model shows a case where partial corrosion occurs over the period of time, and the residual corrosion thickness becomes h. The relationship between the size 2a of the corroded part, the corroded residual wall thickness h, and the pipe internal pressure P is given by the following equation 5. Here, σ is the tensile strength of the tube. FIG. 6(2) is a diagram showing the relationship between the size of the corroded part, 2 amm, and the corroded residual wall thickness, hmm, when the pipe internal pressure P=10 kg/cm'G. For example, with reference to Figure 6 (2), the diameter cross section is 20 m.
In case of corrosion thinning over m, 10kg/cm”G
At the pressure inside the pipe, cracks occur when the remaining wall thickness is 0.5 mm. 1 0 in the case of corrosion thinning over a diameter cross section of 80 mm
At an internal pressure of kg/cmG, cracks occur even with a remaining wall thickness of 2 mm. Furthermore, if no cracks occur under the internal pressure of 10 kg/cm2G, the cracks will be in the shaded area in Figure 6 (2). In this way, from the relationship between the size of the corroded area and the thickness of the corroded remaining wall, it is possible to evaluate the pressure resistance if no cracks occur at a certain pressure level. That is, as shown in FIG. 5 (2), the pressure at which the leakage flow rate suddenly changes when the pipe internal pressure is changed is measured, and the sixth Looking at the graph in Figure (2), we can judge that the underground pipe is located in a wide area not shaded in Figure 6 (2), and evaluate its pressure resistance. If the leak becomes large, the pipe will need to be repaired. When the pressure inside the pipe is changed, if there is no sudden change in the leakage flow rate, it is judged that the area is in the shaded area in the graph similar to Figure 6 (2) prepared for each pressure inside the pipe, and the withstand pressure is determined. It is possible to evaluate gender. This also applies to Figure 7, which will be described next. 6th
The graph in Figure (2) is prepared in advance for each pipe pressure. In addition, when the pressure inside the pipe is changed, the leakage flow rate may be zero, and when the pressure inside the pipe is increased, the leakage flow rate may suddenly increase.In such cases, as well as the above, the pressure resistance Evaluation can be performed. Figure 7 is a diagram for explaining the pressure resistance of the joint thread. Figure 7 (1) shows a model in which the joint thread has been reduced from the initial wall thickness dO to the remaining wall thickness d. Required remaining thickness d
The relationship between , the inner diameter D of the tube, and the pressure D inside the tube is given by the following equation 6.

Here, σ represents the tensile strength of the tube, and α represents the stress concentration factor. In Fig. 7 (2), the pressure inside the pipe is 10 kg.
FIG. 3 is a diagram showing the relationship between the inner diameter D mm of the pipe and the corrosion remaining wall thickness d mm when /cm2G.

Referring to FIG. 7 (2), for example, the nominal inner diameter of the pipe is Okg.
Cracks occur at an internal pressure of /cm2G. If the nominal inner diameter of the pipe is 3B and the remaining wall thickness is 0.19mm, the weight will be 10kg/
Cracks occur at an internal pressure of cm2G. Also 10kg/
If no cracks occur under the pressure in the pipe of cm"G, Fig. 7《2
] in the shaded area. Therefore, if no cracks occur at a certain pressure level, the pressure resistance can be evaluated.

In the above embodiment, the leakage flow rate was measured by changing the gas pressure applied to the underground pipe 1 in stages, but in another embodiment of the present invention, the leakage flow rate was measured by continuously changing the gas pressure. The pressure resistance may be determined by measuring the leakage flow rate and comparing it with the change pattern of the leakage flow rate prepared by rough caulking. Although gas was used as the fluid in the embodiments described above, other embodiments of the present invention may use liquid instead of gas. As described above, according to the present invention, a pressure fluid supply source is connected to a test tube or a test container, and the leakage flow rate is measured while changing the pressure continuously or stepwise, and the measured leakage flow rate is The integrity of the tube or container under test can be determined by comparing the change pattern with the change pattern of leakage flow rate prepared in advance in response to changes in pressure depending on the shape, size, and surrounding conditions of the leakage part. Since this is done, pressure resistance can be evaluated by checking whether the leakage flow rate changes with changes in pressure, or by checking whether there is no leakage. In addition, the evaluation of test tubes or containers under test can be performed all at once for each test section of the test tube or test container, so unlike the prior art, the number of measurement points does not increase, and the evaluation It is possible to significantly reduce time, labor, and expenses, and it is also possible to evaluate the integrity of test tubes and test containers regardless of their shape or size.

[Brief explanation of drawings]

FIG. 1 is a simplified partial cross-sectional view showing the leakage location, FIG. 2 is a diagram showing the relationship between the pressure inside the pipe and the leakage flow rate, and FIG. 3 is a diagram showing the configuration of an embodiment of the present invention. Fig. 4 is a diagram showing the configuration of another embodiment of the present invention, Fig. 5 is a diagram showing the relationship between the measured pressure inside the pipe and the leakage flow rate, and Fig. 6 is a diagram showing the pipe body of one embodiment of the present invention. FIG. 7 is a diagram for explaining the pressure resistance of a joint thread according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Underground pipe, 2... Pressure source, 4... Pressure detection meter, 5... Flow meter, 35... Comparison tank, PO・
...Pipe pressure, Q...Leakage flow rate agent Patent attorney Keiichiro Saikyo Figure 6 Figure 8 of Corrosion IP:! 2a (mm)

Claims (1)

[Claims] Prepare in advance a leakage flow rate change pattern that corresponds to pressure changes for each shape, size, and surrounding situation of the leakage part that can be assumed in the tube or container under test, and supply pressure fluid to the tube or container under test. Connect the source and measure the leakage flow rate in the test tube or test container while changing the pressure of the pressure fluid continuously or stepwise, and compare the change pattern of the measured leakage flow rate and the prepared leakage flow rate. A method for evaluating the integrity of a tube or container, characterized in that the pressure resistance of the tube or container to be tested is evaluated by comparing the variation pattern of .