JP4124419B2 - Valve testing / inspection method and testing / inspection equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is installed in a flow path that uses a low-temperature fluid such as LNG (liquefied natural gas) as a fluid, for example, and mainly functions to flow or seal a fluid in a wide temperature range from room temperature to -196 ° C. The present invention relates to a valve test / inspection method and a test / inspection apparatus suitable for a low-temperature valve comprising a gate valve, a ball valve, a check valve, a ball valve, a butterfly valve, and other valves.
[0002]
[Prior art]
This type of cryogenic valve is one of the functions in which the sealing performance and operability of the valve seat when the cryogenic fluid flows inside the valve and the valve is cooled are one of the important functions. Usually, inspection methods such as an immersion method and an aeration method are known. As shown in FIG. 11, the former immersion method measures the internal temperature of the valve (test valve) 2 and closes the valve diameter with a special jig 3 so that the inside of the valve 2 can be pressurized from the outside. By placing the entire valve in a large cooling tank 4 filled with a refrigerant (for example, liquid nitrogen), the valve 2 is cooled from the outside to a predetermined low temperature state, and then helium gas or the like that does not liquefy even at low temperatures is used. The pressure test is performed.
[0003]
On the other hand, in the latter ventilation method, a low-temperature fluid such as liquid nitrogen is directly flowed into the flow path of the valve, and after the valve is cooled from the inside, a predetermined pressure test or the like is performed using helium gas or the like. Specifically, liquid nitrogen is allowed to flow through the valve, and after completely cooling below the minimum operating temperature, the valve is fully closed to completely remove the liquid nitrogen on the outlet side, and pressurized with helium gas from the inlet side. The leak from the valve seat is measured.
[0004]
In this ventilation method, when the valve seat is closed in order to check the valve seat sealing performance, from that moment, the low temperature fluid stops flowing inside the valve, and the temperature of the valve starts to rise. As a result, the internal pressure of the valve rises according to Boyle-Charle's law, and this pressure rise is also observed as a valve seat leak. For example, it is impossible to measure a very small valve seat leak.
[0005]
In addition, as a refrigerant for cooling the inside of the valve, liquid nitrogen is usually used. However, in the case of the ventilation method, the liquid nitrogen remaining inside the valve is vaporized and gasified immediately after the valve seat is closed. Therefore, even if the valve seat inspection is performed, it is difficult to determine whether the bubble generated as a leak is due to the valve seat leak or the vaporized gas of the refrigerant.
Due to the above drawbacks, the cryogenic valve testing method is mainly performed by the immersion method, and the immersion method is a standard actual temperature valve seat inspection method.
[0006]
[Problems to be solved by the invention]
However, in actual use, the cryogenic valve is cooled from the inside by a cryogenic fluid, and not only can cooling from the outside by the immersion method occur, but the temperature inside and outside the valve can be reduced. It cannot be almost uniform and stable. For example, when a low-temperature valve is used as a block valve of an LNG line (end valve attached to the end of the line), it is −162 ° C. on the upstream side of the valve, but on the downstream side, a very large temperature gradient of atmospheric temperature. Therefore, it was impossible to obtain an actual measurement result by the immersion method.
[0007]
In this way, the immersion method cools the entire valve uniformly, and the cooling state when the valve body cools is different from the actual use state. When confirming the performance, it was not possible to obtain a result considering the influence of partial thermal deformation. For this reason, the quality of the valve structure can be objectively judged, such as the effect on the valve performance of the presence or absence of the riser seat in the valve box, or the proof of superiority such as valve seat sealing performance due to the difference in the valve seat structure. It was difficult to do.
[0008]
The present invention is a test / inspection method developed to solve the above-mentioned problems, and its purpose is to perform a valve test / inspection in a state close to the actual use state, thereby changing the temperature. It is a valve test / inspection method capable of obtaining a change in valve performance, and in particular, to provide a valve test / inspection method and test / inspection device suitable for a low-temperature fluid flow path requiring high accuracy. Objective.
[0009]
[Means for Solving the Problems]
To achieve the above object, the invention according to claim 1, the internal pressure at normal temperature of the valve body the secondary side is fully closed by the valve body as well as measured by the pressure sensor, only the valve body primary, While supplying a low-temperature pressurized fluid consisting of liquid nitrogen and pressurizing nitrogen under pressure, the low-temperature pressurized fluid inside the valve body primary side is guided from the inside of the valve body primary side to the primary pipe connection side and released to the outside. under the state that caused the temperature gradient between the internal valve body primary cooling only valve body primary side by holding a constant pressure, and the valve body primary and the valve body secondary side while the valve body two This is a valve test / inspection method in which valve seat sealing performance is confirmed by detecting pressure fluctuations in the internal pressure on the secondary side with the pressure sensor .
[0010]
According to a second aspect of the present invention, in order to seal the valve body primary side by covering the pipe connection portion on the valve body primary side and to supply the low-temperature pressurized fluid to the valve body primary side under pressure, the fluid supply In order to discharge a low-temperature pressurized fluid from the outside through the lid to the vicinity of the valve body and discharge the low-temperature pressurized fluid in the primary side of the valve body, a fluid discharge pipe is provided on the cover body. This is a test / inspection device for a valve in which the low-temperature pressurized fluid inside the valve body primary side is discharged to the outside .
[0011]
DETAILED DESCRIPTION OF THE INVENTION
An example of an embodiment of a valve test / inspection method and test / inspection apparatus according to the present invention will be described in detail with reference to the drawings.
In FIG. 1, 10 is a test apparatus in the present invention, and 11 is a test valve. The test valve 11 in this example is a gate valve, but may be a globe valve, a check valve, a ball valve, a butterfly valve, or the like.
Liquid nitrogen is allowed to flow through the valve 11 together with pressurizing nitrogen (nitrogen gas), and the pressure is increased to a predetermined pressure described later while measuring the pressure on the primary side 11a of the valve 11. The valve 11 is in a fully closed state via the valve body 12 in advance and is in a state in which a low-temperature fluid consisting of liquid nitrogen and pressurizing nitrogen is pressurized and supplied only inside the primary side 11a of the valve 11, and the valve secondary side The valve seat sealing performance is confirmed by detecting the pressure fluctuation of 11b. In addition, 11c in the figure is a cover for a test valve.
[0012]
1 and 2, a double pipe 13 is connected to the primary side 11a of the main body of the valve 11, the inner cylinder 14 of the double pipe 13 is led to the vicinity of the valve body 12, and a low-temperature fluid is supplied to the valve primary side 11a. Supplying while measuring as a primary side pressure by the pressure sensor 15, exhausting from the valve primary side 11 a is possible by guiding the outer cylinder 16 to the valve pipe connection side and releasing it from the relief valve 17. The valve seat sealing performance can be confirmed in a state where is filled with a low-temperature fluid, and in particular, the sealing performance of the valve in a block valve state in which a large temperature gradient occurs in the valve 11 can be confirmed. In the embodiment of FIG. 2, an outer cylinder 16 having a nominal diameter of 1 / 2B is connected to a lid 11c of a size 4B valve, and an inner cylinder 14 having an outer diameter of 10 mm is inserted into the outer cylinder 16 . By using such a double pipe, the connection portion between the fluid supply pipe and the lid can be made one place, and the fluid is guided to the vicinity of the valve body 12, and the outer cylinder and the inner cylinder of the double pipe are used. By utilizing the squeezing action between the valve and the outside of the valve, the inside of the valve primary side 11a can be effectively filled with fluid. In addition, the fluid supply to the primary side of the valve leads the fluid supply pipe to the vicinity of the valve body 12 without using a double pipe, and the fluid intake is in the vicinity of the lid 11c separately from the fluid supply pipe. The discharge pipe arranged in this manner may be used, and any structure may be used as long as the inside of the valve primary side 11a can be filled with fluid.
[0013]
As a test execution procedure, first, when the valve body 12 is closed and the valve 11 is fully closed, and the low temperature fluid is applied to the valve primary side 11a, the internal pressure of the valve primary side 11a is 1.0 MPa, and the temperature drop is reduced. The flow rate of liquid nitrogen and nitrogen is controlled so as to be as constant as possible (a rate of decrease of 1 to 3 ° C./min), and the temperature and pressure fluctuations on the valve primary side 11a and secondary side 11b are recorded by the recorder 21 in this state. When the valve seat leakage occurs and the pressure on the valve secondary side 11b suddenly rises, the test is terminated. If the valve secondary pressure continues to decrease monotonically, the test is terminated even when the temperature of the valve primary side 11a does not drop even if the flow rate of liquid nitrogen is maximized.
[0014]
Therefore, even if the valve seat 18 is sealed, the low-temperature fluid reliably hits the valve seat 18 inside the valve 11 and is then exhausted to the outside of the valve 11. By using nitrogen for pressurization (nitrogen gas) as the applied pressure (inspection pressure), a constant pressure is always applied to the valve seat 18 during the cooling process. The presence or absence of valve seat leakage from the start to the end of cooling is measured and recorded by a pressure sensor 19 that measures the internal pressure downstream of the valve.
[0015]
Then, an example of the measurement result which measured the valve seat sealing performance at the time of low temperature by the said test method is shown in FIG. In the graph of the figure, the horizontal axis represents the outer surface temperature of the test valve primary side 11a, and the vertical axis represents the internal pressure of the valve secondary side 11b. The valve is a class 150 stainless steel gate valve size 2B. The test is performed with two samples A and B, and in order to clarify the measurement results, in this test, sample B is sealed from room temperature to low temperature. A valve with good stopping performance, Sample A, was a valve with a valve seat sealing property inferior to that of Sample B.
[0016]
As in the case of Sample B, when the valve seat sealability is good from room temperature to low temperature, the secondary side 11b cools as the valve primary side 11a cools, so the internal pressure on the valve secondary side 11b is The monotonous decline is based on Boyle-Charles' law. On the other hand, as in the case of sample A, when valve seat leakage occurs in the process of cooling the valve primary side 11a (in the figure, the valve primary side body temperature is around 136 ° C.), the valve secondary side pressure is A sudden rise.
[0017]
The amount of leakage during the test needs to be calculated by calculation. Actually, the constant of the calculation formula varies depending on the valve temperature during the test, but the temperature of the valve secondary side 11b is set to normal temperature to −50 ° C. It can be calculated by the following calculation formula under the condition that the secondary side pressure does not decrease at all even though the temperature of the side 11b drops by T ° C./min. Leakage amount L (ml / min) = 0.004VT Here, V (cm3) is the volume (including the volume in the pipe) of the valve secondary side 11b.
[0018]
As described above, the valve test method of the present invention can clarify the difference in valve seat sealing performance due to the difference in the product design structure that could not be found at all by the valve seat inspection by the conventional immersion method. Therefore, it is possible to easily determine whether or not the block valve is used under a certain situation.
[0019]
Next, the influence of the presence or absence of the casting pouring seat on the performance of the cryogenic valve is confirmed by the test of the valve of the present invention. In general, the body of the valve is not limited to a low-temperature valve, and there are few internal defects, and a cast product with high soundness is required as a pressure vessel for enclosing the internal pressure. In particular, when the shape of the body is complex, it is usual to set a large number of hot water during casting to enhance the soundness. There is almost a push-down seat. When the press seat mark remains in the body body, the shape of the valve body exhibits an asymmetric shape with respect to the fluid flow direction as shown in FIG.
[0020]
The valve provided for general industrial use has been used while leaving this asymmetrical shape as it is. First, the valve seat surface of the valve used on the higher temperature side than the normal temperature, Normally, oils and fats are applied to prevent the occurrence of scratches during sliding, but this oil and fat effect dramatically improves the valve seat sealing performance. Second, under operating conditions higher than normal temperature, the entire valve may become hot, but there is almost no extreme temperature gradient in the valve body on a daily and continuous basis, unlike a low-temperature block valve. . Thirdly, the man-hour for finishing the asymmetrical casting into a symmetrical shape by a grinder operation or the like can be omitted, and the casting production cost can be kept low. On the other hand, even when this asymmetrical shape is adopted for the low-temperature valve, it is considered that in the test by the immersion method in which the inside and outside of the valve are uniformly cooled, even if the asymmetrical shape remains in the valve body, it is considered to occur during actual use. The temperature gradient cannot be reproduced. Moreover, even if the adverse effect due to the asymmetric shape could be estimated, the magnitude of the effect was not quantified at all. For these reasons, it is impossible to quantitatively determine whether or not a symmetrical body that causes an increase in valve manufacturing cost should be adopted for the cryogenic valve, and the asymmetrical valve with the push-down seat left is used as it is. It was safe.
[0021]
In order to deal with this problem, first, thermal deformation analysis was performed by a finite element method (FEM) assuming a state in which a low-temperature fluid was flown as a block valve. When considering a gate valve, it is the flatness change of the valve seat that has a dominant influence on the sealing performance of the valve. Therefore, this flatness is measured by thermal deformation analysis using the finite element method. As a form of, an asymmetric shape shown in FIG. 4A and a symmetric shape shown in FIG. 4B were modeled. As a condition for analysis, a gate valve having a valve diameter of 4 inches is assumed, the valve is closed, and the cooling inside the valve primary side is set to −162 ° C. assuming LNG (liquefied natural gas) inflow, Further, the outside of the valve was opened to the atmosphere at 20 ° C. An example of the analysis result is shown as a deformation analysis result of the valve seat surface in FIG. FIG. 7 schematically shows the valve body, and the angle (°) of the horizontal axis in FIG. 5 corresponds to the angle along the edge of the valve seat surface 18a of the body, and the valve seat surface 18a at this time The X-direction displacement is shown on the vertical axis. The displacement difference in the case of FIG. 4A was 2.5 μm, whereas the displacement difference in the case of FIG. 4B was 2.0 μm.
[0022]
In FIG. 5, the following was found quantitatively. The valve seat surface of the asymmetrical body 19 of (a) is 25% from 2.5 (μm) /2.0 (μm) = 1.25 compared to the symmetric valve seat surface of (b). Flatness deteriorated. In addition, the presence of the abutment seat 19a which is an asymmetrical shape portion prevents similar deformation of the valve seat surface when a temperature gradient is generated in the valve, and the valve body valve seat surface is difficult to follow.
[0023]
Next, in order to verify the above analysis results, a test according to the present invention was performed for each of the bodies 19 and 20, and the results are shown in FIG. From the figure, in the valve seat sealability under severe use conditions that cause a temperature gradient in the valve body, the body 20 with the finished casting push seat clearly symmetrically superior to the body 19, The results of thermal deformation analysis by the finite element method can be reproduced as the difference of actual valve seat sealing performance. In addition, the valve seat sealability at low temperature by the conventional immersion method of the test valve was zero for 2 minutes in both cases, and no performance difference was observed.
[0024]
As a result of repeating the confirmation process by the finite element method and the low-temperature block valve test, in order to ensure the valve seat sealing performance of the valve used as the block valve, the valve body shape is the X-axis and Y-axis in FIG. It was confirmed quantitatively that it was a symmetric shape with respect to both axes, and that the necessary difference was that the thickness difference of this symmetrical portion did not exceed 25% of the thickness.
[0025]
As described above, according to the thermal deformation analysis by the finite element method, it can be quantitatively confirmed that the flatness of the valve seat surface of the body 19 having the push seat 19a is affected. It is assumed that there will be an impact. In the conventional immersion method, it was not possible to confirm the difference in sealing performance of the valve seat depending on the presence or absence of the push seat, but the valve test method of the present invention measured the secondary side pressure and The difference of the valve seat sealing property by presence or absence was able to be clarified as shown in FIG.
[0026]
Next, the influence on the performance of the cryogenic valve when the main body valve seat type is different is confirmed by the valve testing and inspection method of the present invention. Assuming a gate valve, the type of valve seat installed on the valve body is the case where the valve seat is made by hardening and processing stellite or the like directly on the body casting shown in FIG. There are two types of cases (referred to as the seat ring type hereinafter) when a separate part called a seat ring pre-cured and hardened as shown in FIG. To do.
[0027]
For low temperature gate valves and check valves, the seat ring type is usually adopted. The reason for this is that the seat ring type has better valve seat sealing performance. This is based on qualitative estimation that the deformation of the valve body due to pressure fluctuations inside the valve is difficult to propagate to the seat ring valve seat surface, which is a separate part, and it is difficult to make a quantitative judgment. It was.
[0028]
In order to deal with this problem, first, the change of the main valve seat surface before and after the valve was cooled in the state of use as a block valve was analyzed by thermal deformation analysis by the finite element method. As a condition for the analysis, thermal deformation analysis of the valve seat surface was carried out under exactly the same conditions as the above-mentioned analysis for the integral type and seat ring type lengths of 11 mm and 15 mm of the gate valve size of 4 inches. The result is shown in FIG.
[0029]
In FIG. 9, the following was found quantitatively. Compared with the seat ring type valve seat surface of FIG. 8B, the flatness of the integral type valve seat surface of FIG. Further, considering only the thermal deformation due to cooling in the block valve state, it has been found that the flatness of the valve seat surface decreases as the length of the seat ring increases.
[0030]
Next, in order to verify this result, tests according to the present invention were carried out for the integral type and the seat ring type, and the results are shown in FIG. The figure shows the test results of the integral type and seat ring type with a length of 11 mm. The seat ring type clearly has better valve seat sealing, and the thermal deformation analysis result by the finite element method is the actual valve. Reproduced as a difference in seat sealing. Although not shown in the figure, the same confirmation process was carried out for the 2 inch and 8 inch valve gates. As a result, it was confirmed that the seat ring type was superior. It was confirmed that the results were universal in scope. In addition, the valve seat sealability at low temperature by the conventional immersion method of the test valve was not leaked for 2 minutes, and no performance difference was observed.
[0031]
As for the length of the seat ring, 10 to 25% of the valve diameter is appropriate. If the seat ring is shorter than 10%, the superiority of the above-described seat ring type inherent valve seat sealability is diminished. In addition, when the seat ring is sealed and welded to the valve body, deformation and heat effects may reach the valve seat surface, which is not desirable. On the other hand, when the seat ring is made longer than 25% of the valve diameter, the valve seat sealing performance is improved, but the thickness of the valve main body at the portion where the seat ring is fitted becomes thin, and a thickening is required. At the same time, unnecessarily long seat rings increase valve manufacturing costs and are uneconomical in terms of cost. From the above, it is desirable that the body valve seat type of the low temperature gate valve and check valve is a seat ring type, and its length is suitably 10 to 25% of the valve diameter.
[0032]
As described above, according to the thermal deformation analysis by the finite element method, it can be confirmed that the integral type in FIG. 8A has a greater influence on the flatness of the valve seat surface. In the seat ring type, as shown in Fig. 9, it can be quantitatively confirmed that the difference in length affects the flatness of the valve seat surface, and this difference in valve seat type affects the valve seat sealing performance. It is confirmed that Although the conventional immersion method could not confirm the difference in valve seat sealing performance due to the difference in the valve seat type, the valve test method of the present invention measured the secondary side pressure and The valve seat sealing performance due to the difference can be clarified as shown in FIG.
[0033]
As described above, as a result of performing the test using the valve test method of the present invention, the basic design structure of a valve having sufficient valve seat sealing performance can be determined after quantitatively confirming its rationality. it can. In addition, after designing a cryogenic valve based on this test result, further, for example, by implementing the quality standard at 1.5 to 2.5 times the normal temperature valve inspection standard, a higher quality cryogenic valve is used. And can provide a low-temperature valve with almost no leakage during the test.
[0034]
The main application of the valve test method of the present invention is a low-temperature valve, and an inspection method suitable for a valve in which a temperature gradient of 50 ° C. or more is generated on the primary and secondary sides of the valve under the condition that a temperature gradient is generated in the valve. It can be applied to all valves that require high valve seat sealing performance at low temperatures, such as gate valves, globe valves, check valves, ball valves, and butterfly valves.
[0035]
【The invention's effect】
As is clear from the above, according to the invention according to claim 1, the valve seat sealing performance can be measured in a state where a temperature gradient is generated in the valve body, and the evaluation is performed in a state close to the actual use situation. Can be performed. This measurement result is consistent with the result of analysis by the finite element method, and the change in valve performance due to temperature change can be quantitatively confirmed.
[0036]
According to the invention according to claim 2 or claim 3, the valve seat sealing performance can be confirmed in a state where the inside of the valve primary side is filled with the low-temperature fluid, and the evaluation can be performed in a state close to the actual use situation. it can.
[0037]
In addition, it is possible to provide a valve with a confirmed valve seat sealing performance that can be used under severe conditions in which a temperature gradient occurs in the valve body. It is possible to provide a valve test / inspection apparatus that can be used.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a valve testing apparatus according to the present invention.
2 is an enlarged cross-sectional view showing a fluid supply structure to the valve primary side in FIG. 1;
FIG. 3 is a graph showing test results of a valve test method according to the present invention.
FIG. 4A is a perspective view showing an asymmetric body. (B) is the perspective view which showed the body of a symmetrical shape.
FIG. 5 is a graph showing an example of a deformation analysis result of a valve seat surface by a finite element method.
FIG. 6 is a graph showing a difference in valve seat sealing performance depending on the presence or absence of a casting pouring seat.
FIG. 7 is a perspective view schematically showing the vicinity of the body valve seat of the gate valve.
FIG. 8A is a schematic sectional view showing an integral type valve seat type. (B) is the schematic sectional drawing which showed the seat ring type valve seat format.
FIG. 9 is a graph showing an example of a valve seat surface deformation analysis result by a finite element method.
FIG. 10 is a graph showing a difference in valve seat sealing performance due to a difference in valve seat type.
FIG. 11 is an explanatory view showing a valve testing method by an immersion method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Test apparatus main body 11 Valve 11a Valve primary side 11b Valve secondary side 13 Double pipe 14 Inner cylinder 16 Outer cylinder

Claims (2)

The internal pressure at room temperature of the valve body the secondary side is fully closed by the valve body as well as measured by the pressure sensor, only the valve body primary, pressurized supply cold pressurized fluid consisting of liquid nitrogen and pressurizing nitrogen However, the valve body primary side inside is kept at a constant pressure while the low temperature pressurized fluid inside the valve body primary side is led from the inside of the valve body primary side to the piping connection side of the primary side and released to the outside. only the cooling body primary and under conditions that caused the temperature gradient between the valve body primary and the valve body secondary side, to detect the pressure fluctuations inside pressure of the valve body the secondary side by the pressure sensor A valve test / inspection method characterized in that the valve seat sealing performance is confirmed by The valve test / inspection method according to claim 1, wherein the valve body primary side is sealed with a lid on the valve body primary side piping connection, and the low-temperature pressurized fluid is pressurized and supplied to the valve body primary side. Is arranged to guide the fluid supply pipe from the outside to the vicinity of the valve body through the lid body, and to discharge the low temperature pressurized fluid in the primary side of the valve body, the fluid discharge pipe is disposed on the lid body, A valve testing / inspecting apparatus characterized in that a low-temperature pressurized fluid inside the primary side of the valve body is discharged to the outside by the fluid discharge pipe .

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