Method and jig for inspecting leakage in low temperature valve

Abstract

To provide a method for inspecting leakage in a low temperature valve with which the amount of leakage of cryogenic fluid assuming a usage environment can be appropriately evaluated.SOLUTION: Provided is a method for inspecting the amount of leakage in a low temperature valve 100 used for controlling the flow rate of cryogenic fluid, and the method includes: a jig attachment step of covering the secondary side of the low temperature valve 100 with a secondary-side covering jig 30; a pressurization step of, with the low temperature valve 100 being closed, supplying helium gas to the secondary side through the secondary-side covering jig 30 and supplying cryogenic fluid other than helium to the primary side of the low temperature valve 100 to perform pressurization; and a measurement step of measuring the amount of leakage of the cryogenic fluid leaked to the secondary side and mixed in the helium gas in the pressurization step.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method and a tool for leak inspection of a low-temperature valve. [Background technology]

[0002] Conventionally, cryogenic valves used to control the flow rate of cryogenic fluids such as liquefied natural gas (LNG) have been subjected to leak testing by immersing them in liquefied nitrogen stored in a test tank and pressurizing them with helium gas. While this type of immersion testing method allows for stable measurements, it has the problem that it is difficult to accurately evaluate the amount of leakage of the cryogenic fluid because the valve is not actually supplied with the cryogenic fluid to be used for testing.

[0003] For this reason, Patent Document 1 discloses a valve inspection method in which liquefied nitrogen is supplied to the primary side of the valve and the temperature and pressure fluctuations on the secondary side of the valve are recorded with a recorder so that the valve can be inspected under conditions close to actual usage conditions. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2003-270076 A Summary of the Invention [Problem to be solved by the invention]

[0005] The inspection method in Patent Document 1 above checks the valve seat sealing performance by detecting pressure fluctuations on the secondary side of the valve. However, as the size of the valve increases, the pressure fluctuations on the secondary side of the valve become smaller when a leak occurs, which can make it difficult to measure the amount of leakage.

[0006] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide a method and tool for leak inspection of a cryogenic valve that can appropriately evaluate the amount of leakage of a cryogenic fluid in a simulated usage environment. [Means for solving the problem]

[0007] The object of the present invention is achieved by a leak inspection method for a cryogenic valve used for flow control of a cryogenic fluid, the method comprising: a jig attachment step of covering the secondary side of the cryogenic valve with a secondary side cover jig; a pressurization step of supplying helium gas to the secondary side via the secondary side cover jig while the cryogenic valve is closed, and supplying a cryogenic fluid other than helium to the primary side of the cryogenic valve to pressurize it; and a measurement step of measuring the leakage amount of the cryogenic fluid that has leaked to the secondary side and mixed with the helium gas by the pressurization step.

[0008] In this method for leak inspection of a cryogenic valve, the secondary-side cover jig preferably includes a gas supply port through which helium gas flows in and a gas exhaust port through which the helium gas flows out, and the measurement step preferably includes a concentration detection step of detecting a concentration of the cryogenic fluid contained in the helium gas that flows in from the gas supply port and flows out from the gas exhaust port, and a calculation step of calculating the leakage amount of the cryogenic fluid from the detected concentration of helium gas. The concentration detection step can be performed while continuously passing helium gas through the gas supply port and the gas exhaust port to the secondary side, or can be performed after blocking the outflow of helium gas from the gas exhaust port and storing the helium gas on the secondary side for a predetermined time.

[0009] The measurement process can include a temperature detection process for detecting a temperature change on the secondary side while helium gas is stored on the secondary side for a predetermined time, and a calculation process for calculating the leakage amount of the cryogenic fluid by correcting the amount of gas flowing out from the gas exhaust port for a volume change associated with the temperature change.

[0010] The jig attachment step can be performed by housing the low-temperature valve in a chamber capable of evacuating vacuum.

[0011] The object of the present invention is also achieved by a leak inspection jig for a cryogenic valve that includes the secondary cover jig used in the above-mentioned leak inspection method for a cryogenic valve, wherein the secondary cover jig is a leak inspection jig for a cryogenic valve that includes a gas supply port through which helium gas flows in and a gas exhaust port through which helium gas flows out. Effect of the Invention

[0012] According to the method and tool for leak inspection for a cryogenic valve of the present invention, the amount of leakage of the cryogenic fluid can be appropriately evaluated assuming an operating environment. [Brief description of the drawings]

[0013] [Figure 1] 1 is a schematic diagram of an inspection device used in a leak inspection method for a low-temperature valve according to an embodiment of the present invention; [Diagram 2] FIG. 13 is a schematic diagram of an inspection device used in a leak inspection method for a low-temperature valve according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] An embodiment of the present invention will be described below with reference to the accompanying drawings. Fig. 1 is a schematic diagram of an inspection device used in a method for leak inspection of a cryogenic valve according to an embodiment of the present invention. The inspection device 1 shown in Fig. 1 is a device for inspecting the amount of leakage from a cryogenic valve 100 used for flow control of a cryogenic fluid such as liquefied hydrogen. The cryogenic valve 100 of this embodiment is a butterfly valve for vacuum double piping, but may be a valve of another structure such as a globe valve, a gate valve, or a ball valve.

[0015] 1, the inspection device 1 includes a chamber 10, a primary cover jig 20, and a secondary cover jig 30. The chamber 10 is configured to be sealable with a low-temperature valve 100 housed therein, and can be vacuumed by operating a vacuum pump 11.

[0016] The primary side cover jig 20 has a cryogenic fluid supply port 21 through which the cryogenic fluid flows in and a cryogenic fluid outlet port 22 through which the cryogenic fluid flows out, and is detachably fixed to the primary side (inlet side) of the cryogenic valve 100 by flange connection or the like. The cryogenic fluid supply port 21 is connected to a cryogenic fluid supply source 24 such as a cylinder by a cryogenic fluid supply line 23, and the cryogenic fluid can be supplied to the primary side of the cryogenic valve 100 by operating an opening / closing valve 25. A cryogenic fluid outlet line 27 equipped with a pressure regulating relief valve 26 is connected to the cryogenic fluid outlet 22. The pressure regulating relief valve 26 opens when the primary side of the cryogenic valve 100 exceeds a predetermined pressure, and releases the cryogenic fluid to the atmosphere, thereby making it possible to maintain the pressure on the primary side of the cryogenic valve 100 at a predetermined pressure set based on test conditions or the like.

[0017] The secondary side cover jig 30 has a gas supply port 31 through which helium gas flows in and a gas exhaust port 32 through which helium gas flows out, and is detachably fixed to the secondary side (outlet side) of the low-temperature valve 100 by flange connection or the like. The gas supply port 31 is connected to a helium gas supply source 34 by a gas supply line 33, and helium gas can be supplied to the secondary side of the low-temperature valve 100 by operating an on-off valve 35. A gas exhaust line 37 equipped with an on-off valve 36 is connected to the gas exhaust port 32.

[0018] A heater 40, a flowmeter 41, and a concentration meter 42 are provided downstream of the on-off valve 36 of the gas discharge line 37. The heater 40 heats the gas passing through the gas discharge line 37 to near room temperature using tap water or the like. The flowmeter 41 is, for example, a mass flow meter, and measures the gas flow rate after heating by the heater 40. The concentration meter 42 measures the concentration of the low-temperature fluid that has been mixed into the helium gas by leaking to the secondary side of the low-temperature valve 100. When the low-temperature fluid is liquefied hydrogen, the concentration meter 42 can be a catalytic combustion type hydrogen concentration meter, and can measure the hydrogen concentration in real time while supplying oxygen. The concentration meter 42 may be a sensor of another type, such as a semiconductor type, and a gas sensor can be appropriately selected according to the type of low-temperature fluid.

[0019] In the method for leak testing of a cryogenic valve of this embodiment using the testing device 1 shown in Fig. 1, first, a jig attachment step is performed in which the cryogenic valve 100 is housed in the chamber 10, and the primary side and secondary side of the cryogenic valve 100 are covered with a primary side cover jig 20 and a secondary side cover jig 30, respectively, as shown in Fig. 1. Thereafter, the chamber 10 is sealed with the cryogenic valve 100 closed, and the chamber 10 is evacuated.

[0020] Next, helium gas is supplied to the secondary side of the cryogenic valve 100 via the secondary side cover jig 30. After the atmosphere on the secondary side of the cryogenic valve 100 is replaced with helium gas in this manner, a cryogenic fluid is supplied to the primary side of the cryogenic valve 100 via the primary side cover jig 20, and a pressurizing step is performed in which the primary side of the cryogenic valve 100 is pressurized to a predetermined pressure (for example, 1 to 2 MPa). The cryogenic fluid in this embodiment is liquefied hydrogen, but any cryogenic fluid other than helium may be used, for example, liquefied ammonia, liquefied nitrogen, liquefied oxygen, liquefied natural gas (LNG), liquefied petroleum gas (LPG), etc.

[0021] Next, a measurement process is performed to measure the leakage amount of the cryogenic fluid that has leaked to the secondary side of the cryogenic valve 100 and mixed with the helium gas due to the above pressurization process. This allows the leak inspection to be performed under the same usage environment as when the cryogenic valve 100 is connected to a vacuum double pipe.

[0022] The above measurement step can be performed by a concentration detection step of detecting the concentration of the cryogenic fluid contained in the helium gas that flows in from the gas supply port 31 and flows out from the gas exhaust port 32 by the concentration meter 42, and a calculation step of calculating the leakage amount of the cryogenic fluid from the detected concentration of helium gas. Since the secondary side of the cryogenic valve 100 is replaced with a type of gas different from the cryogenic fluid by the supply of helium gas, the leakage amount of the cryogenic fluid can be accurately obtained by detecting the concentration of the cryogenic fluid.

[0023] The above concentration detection step can be performed by constantly opening the on-off valves 35, 36 to continuously pass helium gas through the secondary side of the low-temperature valve 100 via the gas supply port 31 and the gas exhaust port 32, and detecting the concentration of the low-temperature fluid contained in the helium gas in real time with the concentration meter 42. The gas flow rate passing through the secondary side of the low-temperature valve 100 is approximately constant and can be confirmed by detection by the flow meter 41, or the gas flow rate can be obtained from the consumption of helium gas in the helium gas supply source 34.

[0024] In the above calculation process, the difference in concentration detected by the concentration meter 42 before and after the start of the supply of the low-temperature fluid is taken as the leak concentration, and the leak concentration and gas flow rate from the start of the supply of the low-temperature fluid are integrated to determine the amount of low-temperature fluid leaked within the test time. In addition, the above calculation process can determine the leak flow rate of the low-temperature fluid from the maximum value (peak value) or average value of the leak concentration within the test time. It is preferable to measure the leak concentration and gas flow rate after heating to near room temperature by the heater 40, which makes it possible to stabilize the measurement results and accurately measure the leak amount or leak flow rate.

[0025] In this way, the inspection for the leakage amount of the cryogenic fluid can be completed in a short time by performing the concentration detection step while continuously passing helium gas through the secondary side of the cryogenic valve 100. However, the concentration detection step may also be performed by closing the on-off valve 36 to block the outflow of helium gas from the gas outlet 32, storing the helium gas on the secondary side of the cryogenic valve 100 for a predetermined time, and then allowing the helium gas to flow out.

[0026] In this case, after replacing the secondary side of the low-temperature valve 100 with helium gas, the on-off valve 36 is closed and the pressure on the secondary side of the low-temperature valve 100 is made slightly higher than the pressure on the primary side (for example, 0.0 MPa on the primary side and 0.05 to 0.1 MPa on the secondary side), a pressurizing step is performed in which a low-temperature fluid is supplied to the primary side of the low-temperature valve 100 to pressurize it to a predetermined pressure (for example, 1 to 2 MPa).

[0027] Next, after maintaining this pressurized state for a predetermined time, the on-off valve 36 is opened to perform the measurement process. The calculation process included in the measurement process determines the leak concentration as the difference in concentration detected by the concentration meter 42 before and after the on-off valve 36 is opened, and integrates the leak concentration and gas flow rate after the on-off valve 36 is opened to determine the leak amount of the low-temperature fluid within the test time. In addition, the leak flow rate of the low-temperature fluid can be determined by dividing this leak amount by a predetermined time.

[0028] The measurement process of this embodiment includes a concentration detection process for detecting the concentration of the cryogenic fluid contained in the helium gas that flows into the secondary side of the cryogenic valve 100 from the gas supply port 31 and flows out from the gas exhaust port 32. However, instead of the concentration detection process, it is also possible to include a temperature detection process for detecting a temperature change on the secondary side of the cryogenic valve 100, as will be described later.

[0029] Fig. 2 is a schematic diagram of an inspection device used in a leak inspection method for a low-temperature valve according to another embodiment of the present invention. The inspection device 1' shown in Fig. 2 is the same as the inspection device 1 shown in Fig. 1 except that it has a thermometer 43 instead of the concentration meter 42. Therefore, in Fig. 2, the same components as those in Fig. 1 are denoted by the same reference numerals and repeated explanations will be omitted.

[0030] 2, the thermometer 43 is attached so as to be able to measure the temperature inside the secondary-side cover jig 30, and detects a temperature change on the secondary side of the low-temperature valve 100. A flexible storage bag 44 capable of storing helium gas is branched off and connected to the gas exhaust line 37 downstream of the flowmeter 41, and the secondary side of the low-temperature valve 100 is configured so that the communication destination between the atmosphere and the storage bag 44 can be switched by operating on-off valves 45 and 46.

[0031] In the method of leak inspection for the cryogenic valve using the inspection device 1' shown in FIG. 2, the on-off valves 35 and 36 are opened to supply helium gas to the secondary side of the cryogenic valve 100 and the storage bag 44 while the on-off valve 45 is open and the on-off valve 46 is closed, and then the measurement step is performed while the on-off valves 35 and 45 are closed and the on-off valve 46 is opened to block the supply of helium gas from the helium gas supply source 34 and the storage bag 44. The measurement step includes a temperature detection step of detecting a temperature change on the secondary side while the helium gas is stored on the secondary side of the cryogenic valve 100 for a predetermined time, using a thermometer 43. When the temperature of the stored gas on the secondary side of the cryogenic valve 100 increases over time, the gas expands in volume and flows out to the gas exhaust line 37. If it is assumed that a constant pressure change occurs on the secondary side of the cryogenic valve 100, the volume expansion of the stored gas due to the temperature change is proportional to the temperature increase according to Boyle's law, and therefore can be calculated. Therefore, in the calculation process, the amount of gas actually flowing out from the gas exhaust port 37 is obtained by detection of the flow meter 41 provided in the gas exhaust line 37, and this gas amount is corrected by subtracting the amount of volume change due to the temperature change, thereby making it possible to calculate the leakage amount of the cryogenic fluid that has leaked to the secondary side of the cryogenic valve 100 and mixed with the helium gas.

[0032] The above temperature detection step can be performed with the on-off valve 36 closed, but it may take a long time for the discharge flow rate from the secondary side of the low-temperature valve 100 to stabilize after the on-off valve 36 is opened, and there is also a risk that the pressure will not change to a constant level if the on-off valve 36 is opened after the temperature on the secondary side of the low-temperature valve 100 has increased, so it is preferable to keep the on-off valve 36 open at all times. When the secondary side of the low-temperature valve 100 becomes negative pressure due to a temperature drop, the on-off valve 46 can be closed and the on-off valve 45 can be opened to supply helium gas from the storage bag 44, thereby preventing air from being sucked into the secondary side of the low-temperature valve 100. [Explanation of symbols]

[0033] 1. Inspection equipment 10. Chamber 20 Primary side cover jig 30 Secondary cover jig 31 Gas supply port 32 Gas exhaust port 35,36 On-off valve 40 Heater 41 Flow meter 42 Densitometer 43 Thermometer 100 Low temperature valve

Claims

1. 1. A method for inspecting a leakage amount of a cryogenic valve used for controlling a flow rate of a cryogenic fluid, comprising the steps of: a jig attachment step of covering the secondary side of the low-temperature valve with a secondary-side cover jig; a pressurizing step of supplying helium gas to the secondary side through the secondary side cover jig while the low-temperature valve is closed, and supplying a low-temperature fluid other than helium to the primary side of the low-temperature valve to pressurize it; and a measuring step of measuring the leakage amount of the cryogenic fluid that leaks to the secondary side and mixes with the helium gas due to the pressurizing step.

2. the secondary-side cover jig includes a gas supply port through which helium gas flows in and a gas exhaust port through which the helium gas flows out, The measuring step includes a concentration detecting step of detecting a concentration of a cryogenic fluid contained in the helium gas flowing in from the gas supply port and flowing out from the gas exhaust port; 2. The method for leak inspection of a cryogenic valve according to claim 1, further comprising a calculation step of calculating an amount of leakage of the cryogenic fluid from the detected concentration of helium gas.

3. 3. The leak inspection method for a cryogenic valve according to claim 2, wherein the concentration detection step is performed while continuously passing helium gas through the gas supply port and the gas exhaust port to the secondary side.

4. 3. The leak inspection method for a cryogenic valve according to claim 2, wherein the concentration detection step is performed after blocking the outflow of helium gas from the gas exhaust port and storing the helium gas on the secondary side for a predetermined period of time.

5. The measuring step includes a temperature detection step of detecting a temperature change on the secondary side while storing helium gas on the secondary side for a predetermined time; 2. The method for leak inspection of a cryogenic valve according to claim 1, further comprising a calculation step of calculating a leakage amount of the cryogenic fluid by correcting a volume change caused by a temperature change for the amount of gas flowing out from the gas outlet.

6. 2. The method for leak inspection of a cryogenic valve according to claim 1, wherein the jig mounting step is performed by housing the cryogenic valve in a chamber capable of vacuum suction.

7. A leak inspection jig including the secondary cover jig used in the method for leak inspection of a low-temperature valve according to claim 1, The secondary side cover jig is a leak inspection jig for a cryogenic valve that has a gas supply port through which helium gas flows in and a gas exhaust port through which helium gas flows out.

Images