JP6596210B2 - Pressure cycle test method for composite containers - Google Patents

Description

  The present invention relates to a pressure cycle test method for a composite container.

  A method described in Patent Document 1 is known as a pressure cycle test method for a composite container having a reinforcing layer on the outer peripheral side of a metal liner and capable of holding a high-pressure gas. In the pressure cycle test method described in Patent Document 1, a composite container is filled with a pressure medium, and the durability of the composite container is evaluated by repeating pressurization and depressurization (depressurization) of the pressure medium.

JP 2007-154927 A

In the conventional pressure cycle test method as described above, in consideration of safety, it is necessary to use a liquid as the pressure medium, but tap water is generally used as the pressure medium. When tap water is used for the pressure cycle test, since the metal liner comes into contact with tap water, the durability of the composite container becomes susceptible to surface reaction due to chlorine components and the like in tap water. Further, when the pressure cycle test is prolonged, a surface reaction due to H ₂ O or the like may occur. On the other hand, when the composite container is actually used, there is a fact that there is almost no influence because it holds high-pressure gas, not tap water. As described above, in the conventional pressure cycle test method, the test environment does not correspond to the actual use environment of the composite container (it is a pressure cycle test method under conditions that are harsher than the actual conditions). It is difficult to evaluate appropriate and appropriate durability.

  The present invention has been made to solve such problems, and an object of the present invention is to provide a pressure cycle test method for a composite container capable of evaluating appropriate durability corresponding to an actual use environment.

  In order to solve the above problems, a pressure cycle test method for a composite container according to the present invention is a pressure cycle test method for a composite container that has a reinforcing layer on the outer peripheral side of a metal liner and is capable of holding a high-pressure gas. A first step of filling a composite container with a solution in which a solute is added to a solvent containing a pressure medium, and a second step of repeatedly performing pressurization and decompression of the pressure medium filled in the composite container for a plurality of cycles.

  In the present invention, when the durability of the composite container is evaluated, the liquid filled in the composite container as a pressure medium is a solution in which a solute is added to a solvent containing ethylene glycol. For this reason, the surface reaction of the metal liner due to the chlorine component or the like in the liquid can be suppressed, and the surface reaction for the durability of the composite container can be suppressed. As a result, the test environment of the pressure cycle test is close to the actual use environment of the composite container that holds the high-pressure gas with almost no surface reaction. Therefore, it is possible to evaluate the proper durability corresponding to the actual use environment.

  Further, when the internal pressure of the composite container does not reach the reference pressure due to pressurization of the pressure medium in the second step, or the time until the internal pressure of the composite container reaches the reference pressure by the pressurization is equal to or longer than the reference time. If so, the second step is terminated. Thus, for example, when measuring the number of cycles, which is the number of repetitions of pressurization and decompression of the pressure medium, as an evaluation of the durability of the composite container, the number of cycles until the composite container deteriorates and leaks in the actual use environment. Cycle number close to can be measured.

Further, ethylene glycol has a conductivity lower than 2 × 10 ⁻⁴ S / cm, preferably lower than 1 × 10 ⁻⁵ S / cm, more preferably lower than 5 × 10 ⁻⁶ S / cm. Good. Further, ethylene glycol may have a dissolved oxygen content at 21 ° C. of less than 5 mg / L, more preferably less than 2 mg / L. Further, the solvent may further contain ion exchange water or the like. In the case of an organic compound, the solute may contain at least one of an amine group and an organic acid group. In the case of an inorganic compound, for example, at least one of chromate, nitrite, silicate, and polyphosphate. Any one of them may be included. Thereby, the surface reaction of the metal liner can be further suppressed.

  Moreover, 1-10 wt% may be sufficient as the addition amount of a solute. Thereby, the surface reaction of the metal liner can be sufficiently and sufficiently suppressed.

  The composite container may be a hydrogen station pressure accumulator. In this case, since the composite container is increased in size and the test time of the pressure cycle test is easily extended, the effect of suppressing the surface reaction of the metal liner is more remarkably exhibited.

  According to the present invention, it is possible to evaluate proper durability corresponding to an actual use environment.

It is a partial cross section figure which shows the composite container evaluated by the pressure cycle test method of the composite container which concerns on embodiment. It is a schematic block diagram which shows the test apparatus which enforces the pressure cycle test method of the composite container which concerns on embodiment. It is a flowchart which shows the pressure cycle test method of the composite container which concerns on embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a partial cross-sectional view showing a composite container evaluated by the pressure cycle test method for the composite container according to the embodiment. As shown in FIG. 1, the composite container 1 can hold a high-pressure gas (dry gas), and is a container for storing a fuel gas such as hydrogen or natural gas at a high pressure, for example. For example, the composite container 1 has a length of 0.2 to 6 m and a diameter of 200 to 600 mm. The normal pressure is 20 to 110 MPa, and the design pressure is 50 to 300 MPa. The composite container 1 may be a hydrogen station pressure accumulator that is used in a stationary manner, or may be a vehicle-mounted container that is mounted on a moving body and used.

  In particular, when the composite container 1 is a vehicle-mounted container, for example, the capacity is 30 to 160 L, the diameter is 200 to 500 mm, and the length is about 200 to 1000 mm. Moreover, in the case of a hydrogen station pressure accumulator, for example, the capacity is 100 to 1500 L, the diameter is 200 to 600 mm, and the length is about 1 to 6 m. In addition, the use of the composite container 1 is not limited, and can be used for various uses.

  The composite container 1 includes a cylindrical metal liner 2 and a reinforcing layer (fiber reinforced plastic layer) 3 provided on the outer peripheral side of the metal liner 2 so as to cover the outer peripheral side of the metal liner 2. I have. At least one of the end portions 2a of the metal liner 2 is formed in a dome shape, and a base 4 is attached to the tip of the end portion 2a so as to protrude in the axial direction. Here, both end portions 2a are formed in a dome shape, and a base 4 is attached to the tip ends of the both end portions 2a. The mounting height (projection height) of the base 4 is set to a height at which the base 4 protrudes from the reinforcing layer 3, but may be equal to the thickness of the reinforcing layer 3.

  The metal liner 2 is made of, for example, an aluminum alloy, steel, or the like, and is formed by forming the shape of the base 4 into a pipe shape or plate shape formed into a container shape by spinning or the like. As an aluminum alloy, for example, 6061 material of an Al—Mg—Si based alloy can be given. Examples of steel include SUS316L.

  The reinforcing layer 3 is formed by winding a fiber bundle 10 impregnated with a thermosetting resin around the outer periphery of the metal liner 2 and heating and curing the fiber bundle 10 in a heating furnace. Types of thermosetting resins include phenolic resin, urea resin, unsaturated polyester resin, vinyl ester resin, polyimide resin, bismaleimide resin, polyimide resin, polyurethane resin, diallyl phthalate resin, epoxy resin, melamine resin or allyl resin However, it is not limited to these. The thickness of the reinforcing layer 3 is, for example, about 4 cm.

  Further, as the fiber bundle 10, for example, carbon fiber, glass fiber, aramid fiber, boron fiber, polyethylene fiber, steel fiber, Zylon fiber, or vinylon fiber can be used. Lightweight carbon fiber is used. Further, the number of fibers (filaments) of the fiber bundle 10 of the present embodiment is not particularly limited, but is in the range of 1000 to 50000 filaments, preferably 3000 to 30000 filaments, and here it is 24000 filaments.

  When the composite container 1 configured as described above is manufactured, first, a fiber bundle 10 preliminarily impregnated with a thermosetting resin is wound around the outer periphery of the metal liner 2 to form a plurality of fiber bundle layers (fiber reinforced plastics). Layer), thereby obtaining a container intermediate.

  In addition, the container intermediate is intended for the composite container 1 in the manufacturing process, and here, is intended for the state before the thermosetting resin of the fiber bundle 10 is thermoset (hereinafter the same). . Moreover, the winding method of the fiber bundle 10 is not particularly limited, but for example, an FW (filament winding) method can be adopted. Examples of the FW method include a method (a so-called Dry method) in which a fiber bundle (tow prepreg) 10 impregnated with a thermosetting resin is prepared and wound around a metal liner 2.

  And after winding the fiber bundle 10, the thermosetting resin of the fiber bundle 10 is hardened by heating a container intermediate body with a heating furnace, and, thereby, the composite container 1 provided with the reinforcement layer 3 is obtained. Alternatively, the thermosetting resin may be cured while winding the fiber bundle 10.

  A pressure cycle test method is performed on the composite container 1 manufactured as described above. Note that the pressure cycle test method may be applied to a sample test performed on some composite containers 1 as part of the method of manufacturing the composite container 1. The pressure cycle test method evaluates the durability of the composite container 1 and includes a step of filling the composite container 1 with a solution as a pressure medium, and a plurality of cycles of pressurization and decompression of the pressure medium filled in the composite container 1. Repeatedly performing the process. The pressure cycle test method of this embodiment is performed according to a predetermined standard. Examples of the predetermined standard include the following three.

(1) ASME (overseas standards)
In the pressure cycle test for the composite container 1, the minimum pressure is defined as 10% or less of the design pressure, and the maximum pressure is defined as 100% or more of the design pressure (1.1 times the normal pressure). In addition, the repetition frequency should not exceed 0.25 Hz (15 cycles / min), the outer surface temperature of the composite container 1 should not exceed 50 ° C. during the test, and the number of test cycles N determined. Is stipulated. The number of test cycles N is determined by the number of tests. Also, 10% of the minimum cycle is performed at the minimum design temperature, and the remaining cycles are performed at room temperature. If the composite container 1 can withstand N pressure cycles without causing destruction due to rupture or leakage, and does not cause destruction due to rupture in N additional pressure cycles, the composite container 1 passes.

(2) Technical standard KHKS0121 (2005) for general composite containers
As a room temperature pressure cycle test in the design confirmation test, first, the composite container 1 is filled with a liquid, and the pressure fluctuation between the atmospheric pressure and the upper limit pressure equal to or higher than the maximum filling pressure (ordinary pressure) is 10 times or less per minute. It is specified that the operation is repeated 10,000 times or more, and in this case, the holding time at a pressure of 90% or more of the maximum filling pressure exceeds 1.2 seconds. Subsequently, the pressure fluctuation between the atmospheric pressure and the upper limit pressure equal to or higher than the pressure test pressure is repeated 30 times or more at a rate of 10 times or more per minute, and in this case, at a pressure of 90% or more of the pressure test pressure. The holding time is specified to exceed 1.2 seconds. Subsequently, it is specified that a burst test is performed.

  The acceptance criteria are that the composite container 1 is not deformed or leaked due to the pressure fluctuation, that the burst pressure is 90% or more of the minimum burst pressure in the burst test, and the origin of the burst is the body in the burst test. It is supposed to satisfy all of that.

(3) JARI S001 (2004)
As a normal temperature pressure cycle test in the design confirmation test, the composite container 1 is filled with a liquid, and the pressure between 2 MPa or less and the pressure of 125% or more of the maximum filling pressure (ordinary pressure) is less than 10 times per minute and 45,000 times. It is stipulated that reciprocation is performed as described above. The acceptance criterion is that there is no leakage after 11250 times and no rupture.

  In any of the standards described above, the pressure cycle test requires the use of a liquid (atmospheric liquid) as a pressure medium. This is because, in the compressed state, gas has a larger energy than liquid, and when pressure is released due to breakage of the test object, etc., the liquid has a very small volume expansion and has little influence on the surroundings. On the other hand, the gas undergoes rapid volume expansion and has a great influence on the surroundings. The pressure cycle test method of the present embodiment may be carried out according to any standard, and is not limited to these, and can be applied to all pressure cycle tests using a liquid as a pressure medium.

  In addition, according to the container safety regulations based on the High Pressure Gas Safety Law, it is specified that the pressure cycle test does not rupture at 45,000 times or less and that there is no leakage after a predetermined number of times. The predetermined number of times is 11250 times for a hydrogen station pressure accumulator and a vehicle-mounted container such as a taxi or a truck other than a private passenger car, and 5500 times for a vehicle-mounted container of a private passenger car.

  Here, in the pressure cycle test of the present embodiment, the pressure cycle test of the composite container 1 is performed with the set number of cycles, and when the leak occurs in the composite container 1 before reaching the number of cycles. The pressure cycle test is completed and the number of cycles until leakage occurs is measured. The test apparatus and test method of the following embodiment will be described in detail.

  FIG. 2 is a schematic configuration diagram illustrating a test apparatus that performs the pressure cycle test method for the composite container according to the embodiment. As shown in FIG. 2, the test apparatus 100 is used in a pressure cycle test, and includes a tank 20, a compressor 30, a pressure sensor 40, and a controller 50. The tank 20 and the compressor 30 are connected to each other through a metal pipe L1. Further, the composite container 1 is connected to the compressor 30 through a metal pipe L2 so as to be able to communicate therewith. The pipe L <b> 2 is connected to one of the caps 4 of the composite container 1. The other cap 4 of the composite container 1 is plugged and closed. In addition, piping L1, L2 is not restricted to metal, For example, resin may be sufficient.

  The tank 20 stores a solution to which a solute has been added. The tank 20 is made of resin or metal, for example. The compressor 30 uses the solution added with the solute as a pressure medium, pressurizes the solution added with the solute from the tank 20 side to the composite container 1 side, and increases the internal pressure of the composite container 1. The pressure sensor 40 is provided in the vicinity of the compressor 30 of the pipe L2, detects the pressure in the pipe L2, and outputs the pressure information to the controller 50. Since the inside of the pipe L <b> 2 can communicate with the inside of the composite container 1, the pressure detected by the pressure sensor 40 corresponds to the internal pressure of the composite container 1. The pressure sensor 40 may be provided at a location other than this as long as it can detect a pressure corresponding to the internal pressure of the composite container 1, and may be provided inside the composite container 1, for example.

  The controller 50 includes a computer including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The controller 50 is electrically connected to the pressure sensor 40, inputs pressure information from the pressure sensor 40, and makes a determination on the state of the composite container 1 based on the pressure information. If the composite container 1 deteriorates and has cracks or the like, the pressure medium leaks from the composite container 1 even if the pressure medium is pressurized, so that the internal pressure of the composite container 1 cannot be increased or is difficult to rise. To do. Therefore, the controller 50 can detect leakage of the composite container 1 based on the pressure information.

  Specifically, in order to detect leakage of the composite container 1, the controller 50 determines whether or not the internal pressure of the composite container 1 reaches the reference pressure by pressurization of the pressure medium, and the internal pressure of the composite container 1 by the pressurization. It is determined whether or not the time until the pressure reaches the reference pressure is equal to or less than the reference time. The reference pressure can be, for example, the maximum pressure of the pressure cycle test. The reference pressure value and the reference time value are preset in the controller 50, respectively. If the leak can be detected, the determination by the controller 50 is not limited to this. For example, instead of determining the time until the internal pressure of the composite container 1 reaches the reference pressure due to pressurization of the pressure medium, the speed may be determined.

  The controller 50 is electrically connected to the compressor 30, controls the operation of the compressor 30, controls the internal pressure of the composite container 1, and measures the number of cycles of the pressure cycle test. The controller 50 also determines whether or not the measured number of cycles has reached the number of end cycles that is the end condition of the pressure cycle test. The number of end cycles is preset in the controller 50 for each reference. In the case of a pressure cycle test in which the number of end cycles is not set, the determination process of the controller 50 can be omitted.

  FIG. 3 is a flowchart illustrating the pressure cycle test method for the composite container according to the embodiment. Here, in order to detect leakage of the composite container 1, the controller 50 determines whether or not the internal pressure of the composite container 1 reaches the reference pressure by pressurization of the pressure medium, and the internal pressure of the composite container 1 by the pressurization. It is determined whether or not the time until the pressure reaches the reference pressure is equal to or less than the reference time. Note that only one of these may be determined. Normally, the latter judgment is easier to detect smaller leaks, but small leaks cause large leaks immediately, so it is unlikely that any judgment will cause a large difference in the number of cycles until a leak is detected. It is done.

As shown in FIG. 3, in the pressure cycle test of this embodiment, first, a solution to which a solute used as a pressure medium is added is prepared (S1). Specifically, the solution containing the solute is prepared by adding the solute to a solvent containing ethylene glycol. The solvent may be a mixed solution further containing tap water, ion-exchanged water, purified water, distilled water, an organic solvent other than ethylene glycol, and the like. Ethylene glycol has a conductivity lower than 2 × 10 ⁻⁴ S / cm, preferably lower than 1 × 10 ⁻⁵ S / cm, more preferably lower than 5 × 10 ⁻⁶ S / cm. . Further, ethylene glycol has a dissolved oxygen amount at 21 ° C. of less than 5 mg / L, more preferably less than 2 mg / L. When the metal liner 2 is made of an aluminum alloy, the solution is set to a pH of 2 to 9, preferably 4 to 8, for the purpose of preventing the surface reaction of the aluminum alloy. The use temperature is set to the melting point of the pressure medium to 40 ° C, preferably 1 to 30 ° C. If it is less than 1 ° C., the liquid viscosity becomes high, and the test may be prolonged due to clogging of piping and a decrease in cycle speed. A temperature higher than 30 ° C. promotes the surface reaction of the metal liner 2 and may reduce the number of cycles.

  The solute is an anticorrosive agent having an anticorrosive effect on each metal constituting the metal liner 2, the pipes L <b> 1 and L <b> 2 and the compressor 30 of the composite container 1. If the tank 20 is made of metal, the solute may further have an anticorrosive effect on the metal constituting the tank 20. The surface reaction of metals, particularly aluminum alloys, and the mechanism of reaction suppression by solutes will be described below.

The surface reaction of the metal by the component Cl ⁻ ion involved in the surface reaction is a reaction of O ₂ + H ₂ O + 4e ⁻ → 4OH ⁻ due to H ₂ O in the solution, dissolved oxygen, and electrons on the metal surface, and the OH ⁻ ion Al ^{3+, which} has grown and lost electrons, elutes on the metal surface, the metal surface is positively charged, and electrostatically attracted Cl ⁻ ions destroy the metal surface. There are a permeation theory that Cl ⁻ ions penetrate into the coating and promote the dissolution of the metal, and an adsorption theory that a soluble complex forms on the metal surface and destroys the surface. As an anticorrosion mechanism for this, there is a theory that a solute component is adsorbed on a metal surface to suppress a surface reaction. There is also the theory that the surface reaction is suppressed by covering the Cl ^- ions and reducing the probability of contact with the metal surface.

When the contact time between the aluminum alloy and the pressure medium is prolonged, a surface reaction due to H ₂ O may also occur. Surface reaction of the metal according to component _{H 2} O which is involved in the surface reaction, _H 2 O in solution, dissolved oxygen, an electron of the metal _{surface, O 2 + H 2 O +} 4e - → 4OH - the following reaction occurs, OH ^- ions Al ³⁺ that has lost its electrons as it proliferates elutes on the metal surface, and a precipitate is formed by the reaction of Al ³⁺ + 3OH ⁻ → Al (OH) ₃ . As an anticorrosion mechanism for this, there is a theory that a solute component adsorbs on a metal surface to suppress a surface reaction. There is also a theory that the solute component covers OH ⁻ ions and H ⁺ ions, and the surface reaction is suppressed by reducing the probability of contact with the metal surface.

Note that the surface reaction mechanism described above is described in the following references.
References: Japan Society of Materials Corrosion and Corrosion Prevention Committee, “Theory and Application of Corrosion and Corrosion Learned through Experiments”, Koyo Shobo, September 1999

Solutes are, for example, amine-based and organic acid-based. Examples of amines include diethanolamine. Moreover, as an organic acid type | system | group, hydroxy acid, carboxylic acid, and aminopolycarboxylic acid are mentioned, for example. Others include ethylene glycol, sodium metasilicate, potassium metasilicate, phenol, phosphate ester, amide compound, sodium polyphosphate, sodium metaphosphate, sodium phosphate, and certain organosilane compounds. A water-soluble lubricant composition etc. are mentioned. Among these solutes, amino acid-based or organic acid-based ones are particularly preferable from the viewpoint of suppressing the influence on durability as compared with, for example, ethylene glycol (addition amount: 50 wt%). Cl ^- ions, with respect to the suppression of the surface reactions of the Al alloy by H 2 _O, it is effective particularly amine and organic acid.

  From the viewpoint of suppressing the influence on durability, those containing at least one of amine-based and organic acid-based solutes are preferable. The amount of the solute added is, for example, 0.1 to 10 wt%, preferably 1 to 10 wt%. When the amount of solute added is less than 1 wt%, the effect of suppressing the influence of chlorine components and the like is relatively small. If it is more than 10 wt%, the solution has a pH outside the range of 4-8, which may accelerate the metal surface reaction. Alternatively, the compression rate of the pressure medium is increased by the solute component, and the test may be prolonged by reducing the speed of the cycle test.

  Subsequently, the composite container 1 is filled to a full capacity with the solution added with the solute as a pressure medium (S2), and the solution added with the solute is introduced into the tank 20 (S3). Subsequently, the tank 20 and the compressor 30 are connected so as to be able to communicate with each other through the pipe L1, and the compressor 30 and the composite container 1 are connected so as to be able to communicate with each other through the pipe L2 (S4). As a result, the composite container 1 and the tank 20 storing the solution to which the solute has been added are connected so as to communicate with each other. Subsequently, pressurization of the solution to which the solute charged in the composite container 1 is added is started (S5). Specifically, the compressor 30 is operated to pressurize the solution to which the solute has been added by feeding the solution to which the solute has been added from the tank 20 side to the composite container 1 side.

  Subsequently, it is determined whether or not the pressure detected by the pressure sensor 40 has increased (S6). If the pressure does not increase despite the pressure applied to the solution to which the solute has been added, the composite container 1 is not in a completely sealed state but deteriorates and has cracks, etc. It can be seen that there is a leak. Therefore, in the case of NO in S6, it is determined that the composite container 1 has a leak, and the pressure cycle test is terminated. In the determination of S6, if the pressure detected by the pressure sensor 40 is not increased, it is clear that the pressure does not reach the maximum pressure of the pressure cycle test. Is determining whether or not the maximum pressure is reached.

  In the case of YES in S6, it is determined whether or not the pressure detected by the pressure sensor 40 has reached the maximum pressure (reference pressure) of the pressure cycle test (S7). The maximum pressure is, for example, not less than the design pressure of the composite container 1 and is 50 to 140 MPa. The maximum pressure is not limited to this. If NO in S7, the process proceeds to S6. On the other hand, in the case of YES in S7, it is determined whether or not the time until the pressure detected by the pressure sensor 40 reaches the maximum pressure of the pressure cycle test is equal to or longer than the reference time (S8).

  If the time is equal to or longer than the reference time, it can be seen that the composite container 1 is not in a completely sealed state, but is in a state where there is a leak due to deterioration and cracks. Therefore, in the case of YES in S8, it is determined that the composite container 1 has a leak, and the pressure cycle test is terminated. In the case of NO in S8, the pressure cycle test is continued, and pressure reduction for the solution to which the solute inside the composite container 1 is added is started (S9). Specifically, the compressor 30 stops operating. Thereby, the internal pressure of the composite container 1 is reduced.

  Subsequently, it is determined whether or not the pressure detected by the pressure sensor 40 has reached the minimum pressure of the pressure cycle test (S10). The minimum pressure is, for example, 10% or less of the design pressure of the composite container 1 and is 0 to 14 MPa. The minimum pressure is not limited to this. In the case of NO in S10, the internal pressure of the composite container 1 is continuously reduced, and the determination process in S9 is repeated. On the other hand, in the case of YES in S10, the number of executions of one pressure cycle process including the series of processes of S5 to S10 is measured (counted up) as the number of cycles (S11).

  Subsequently, it is determined whether or not the number of cycles measured in S11 has reached a preset number of end cycles (S12). If NO in S12, the process proceeds to S5. On the other hand, if YES in S12, the pressure cycle test is terminated.

  As described above, according to the present embodiment, in S <b> 2, the composite container 1 is filled as a pressure medium with a solution obtained by adding a solute to a solvent containing ethylene glycol (first step). Subsequently, in S <b> 5 to S <b> 12, a pressure cycle process is performed in which pressurization and decompression of the pressure medium filled in the composite container 1 are repeatedly performed (second process). In S6, when the internal pressure of the composite container 1 does not reach the maximum pressure due to the pressurization of the pressure medium in the second step, or the time until the internal pressure of the composite container 1 reaches the maximum pressure due to the pressurization. Is equal to or longer than the reference time, the second step is terminated (third step).

  Thus, when evaluating the durability of the composite container 1 by the pressure cycle test, the liquid filled in the composite container 1 as a pressure medium is a solution in which a solute is added to a solvent containing ethylene glycol. For this reason, the surface reaction of the metal liner 2 due to contact with a chlorine component in the liquid is suppressed, and the pressure cycle test is performed in the actual use environment of the composite container 1 in which a high-pressure gas that hardly generates a surface reaction is retained. The environment is close. As a result, a decrease in the number of cycles measured until the composite container 1 deteriorates and leaks is suppressed. This makes it possible to bring the measured number of cycles closer to the number of cycles in the actual usage environment (increase it to correspond to the actual number of cycles), and evaluate the appropriate durability corresponding to the actual usage environment. be able to. In addition, it is possible to prolong the service life of the devices and components used, such as the compressor 30, the pipes L1 and L2, and the tank 20.

Ethylene glycol has a conductivity lower than 2 × 10 ⁻⁴ S / cm, preferably lower than 1 × 10 ⁻⁵ S / cm, more preferably lower than 5 × 10 ⁻⁶ S / cm. Is done. Further, ethylene glycol has a dissolved oxygen amount at 21 ° C. of less than 5 mg / L, more preferably less than 2 mg / L. As described above, ethylene glycol has less impurities such as chlorine ions, nitrate ions, sulfate ions, etc., has a low conductivity, and has a low dissolved oxygen content, thereby further suppressing the surface reaction of the metal liner. . The solute is more preferably a solute containing at least one of amine-based and organic acid-based from the viewpoint of suppressing the influence on durability. Thereby, the surface reaction of the metal liner can be further suppressed. Moreover, the addition amount of a solute is 1-10 wt%. Thereby, the surface reaction of the metal liner can be sufficiently and sufficiently suppressed.

  Here, the above effect of being able to evaluate appropriate durability corresponding to the actual use environment will be specifically described with reference to Examples and Comparative Examples.

  In the examples, according to the pressure cycle test method of the composite container of the present embodiment, when a pressure cycle test is performed using a solution prepared by adding a solute to ethylene glycol water as a pressure medium, the number of cycles until leakage occurs is calculated. Obtained by simulation. Here, the ethylene glycol water is a mixed solution of ethylene glycol 80 wt% and ion exchange water 20 wt%. When ethylene glycol is used at a concentration higher than 80 wt% without being diluted, it must be handled as a dangerous substance. The number of cycles was obtained for each of the composite container A which is a vehicle-mounted container and the composite container B which is a hydrogen station pressure accumulator. The composite container A has a capacity of 150 L and a design pressure of 90 MPa. The composite container B has a capacity of 300 L and a design pressure of 90 MPa.

  Here, the maximum pressure σmax of the pressure cycle test is 90 MPa, the minimum pressure σmin is 8 MPa, the amplitude pressure ((σmax−σmin) / 2) is 41 MPa, and the test speed (repetition frequency of pressurization and decompression) is the composite container A Was 10 cycles / min, and the composite container B was 4 cycles / min. Further, as a solute, Megahibitor # 23 (trade name) manufactured by Nippon Mechachemical Co., Ltd. containing both amine-based and organic acid-based components was used, and the amount of the solute added was 3 wt%.

  In the comparative example, according to the pressure cycle test method of the conventional composite container, the cycle number was obtained by simulation in the same manner as in the example except that tap water was used instead of the solution in which the solute was added to ethylene glycol.

  The target value is a value corresponding to the actual number of cycles. That is, the target value is a value that is assumed as the number of cycles when hydrogen gas is used as the atmospheric gas and the pressure cycle test is performed in the same manner as in the example with the maximum pressure, the minimum pressure, and the amplitude pressure. The target value was calculated and calculated based on the fatigue test result of the aluminum alloy in a dry atmosphere.

The results of Examples and Comparative Examples are shown in Table 1. The number of cycles is shown as a relative ratio when the comparative example of the composite container A is 200.

The simulation here was performed based on the surface reaction test of a 6061-T6 material, which is a typical aluminum alloy material used for a metal liner, and the test result of a fatigue test in the corresponding solution. That is, the number of cycles was calculated from the time until the surface reaction of the aluminum alloy material occurred in the surface reaction test and the time until the aluminum alloy material broke in the fatigue test in the corresponding solution. Table 2 shows the composition of 6061 material. Note that T6 is a processing method, and shows an artificial aging treatment without actively cold working after the solution treatment.

  As shown in Table 1, with respect to the composite container A, in the example, it is possible to confirm the effect of evaluating the appropriate durability corresponding to the actual use environment. Specifically, the number of cycles in the example was five times that of the comparative example, and reached 91% of the target value.

  As described above, in the comparative example, it is considered that the number of cycles is reduced due to the surface reaction of the metal liner caused by the chlorine component of tap water. On the other hand, in the examples, since a solution in which a solute is added to a solvent containing ethylene glycol is used, it is considered that the reduction in the number of cycles due to the surface reaction of the metal liner is suppressed.

  Moreover, as shown in Table 1, about the composite container B, in an Example, the effect of evaluating the appropriate durability corresponding to an actual use environment can be confirmed. Specifically, the number of cycles in the example exceeded 10 times that of the comparative example and reached 95% of the target value.

  As in the case of the composite container A, in the comparative example of the composite container B, it is considered that the number of cycles is reduced due to the surface reaction of the metal liner caused by the chlorine component of tap water. On the other hand, in the examples, since a solution in which a solute is added to a solvent containing ethylene glycol is used, it is considered that the reduction in the number of cycles due to the surface reaction of the metal liner is suppressed. Further, in the case of the composite container B, the difference in the test time of the pressure cycle test can be considered as the cause of the difference in the number of cycles between the example and the comparative example compared to the case of the composite container A. That is, in the composite container B, since the test time of the pressure cycle test is prolonged, the fact that tap water is more likely to cause a surface reaction of the metal liner than a solution in which a solute is added to a solvent containing ethylene glycol is remarkable. It is thought that it became.

Moreover, the electrical conductivity of ethylene glycol, which is the main component of the solvent of the example, was determined as follows. First, a conductivity cell including a pair of energizing electrodes was immersed in ethylene glycol (100%). Subsequently, a constant voltage was applied between the electrodes, and the specific resistance (electrical resistivity) was measured using a conductivity meter. The cell constant was determined using potassium hydroxide as a standard solution for calibration. When the resistance between the electrodes is R (Ω), the distance is L (cm), the cross-sectional area is A (cm ² ), and the specific resistance is ρ (Ω · cm),
R = ρ (L / A)
This relationship holds. The conductivity K is the reciprocal of ρ,
K = 1 / ρ = L / (A × R)
It is represented by Using this equation, the conductivity of ethylene glycol (100%) was determined. The conductivity was 3.7 × 10 ⁻⁶ S / cm. Thus, ethylene glycol (100%) had a conductivity lower than 2 × 10 ⁻⁴ S / cm. The reason why the conductivity is low is that the content of chlorine ions, nitrate ions, sulfate ions, etc. involved in the reaction on the metal surface is low. In addition, the electrical conductivity of the ethylene glycol water which is a solvent of an Example was 3.2 * 10 < ^-6 > S / cm. The conductivity of the ion exchange water was 1.4 × 10 ⁻⁶ S / cm.

  Moreover, the dissolved oxygen amount of ethylene glycol which is the main component of the solvent of the example was measured with a galvanic oxygen sensor. The galvanic oxygen sensor uses lead for the anode and gold or platinum for the cathode. In the galvanic oxygen sensor, oxygen that has passed through the gas-permeable diaphragm is reduced at the cathode, so that a reduction current proportional to the amount of oxygen flows between the two electrodes. Here, the oxygen battery tank was constituted with ethylene glycol (100%), the reduction current was measured, and the amount of dissolved oxygen was calculated. The amount of dissolved oxygen at 21 ° C. was 1.5 mg / L. Thus, ethylene glycol (100%) had a dissolved oxygen content at 21 ° C. of less than 5 mg / L and less than 2 mg / L. Since oxygen is involved in the reaction on the metal surface, a pressure medium with a small amount of dissolved oxygen can be said to be suitable for the pressure cycle test. In addition, the dissolved oxygen amount of the ethylene glycol water which is a solvent of an Example was 2.1 mg / L. Moreover, the dissolved oxygen amount of ion-exchange water was 4.3 mg / L.

  In the pressure cycle test, considering the influence on the durability of the composite container such as the surface reaction of the metal liner, it is desirable to increase the test speed to the maximum value within the range defined by the standard and shorten the test time. . As described above, the maximum value of the test speed is (1) ASME (overseas standard) is 15 times / minute (once every 4 seconds), and (2) the technical standard KHKS0121 (2005) for general composite containers and (3) In JARI S001 (2004), it is 10 times / minute (once every 6 seconds).

  However, in the case of a large composite container such as the composite container B, it is difficult to perform a pressure cycle test at such a high test speed due to the lack of pump capacity and power, and the normal test speed is 4 times / minute. (Once every 15 seconds). Furthermore, the pressure cycle test of the large composite container has a larger number of cycles than the pressure cycle test of the small composite container, and therefore the test time becomes enormous. Under such circumstances, the pressure cycle test method of the present embodiment in which a solution in which a solute is added to a solvent containing ethylene glycol is used as a pressure medium is used for, for example, a pressure cycle test of a large composite container such as an accumulator for a hydrogen station. It is more effective against this.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, It changed within the range which does not change the summary described in each claim, or was applied to another thing. May be.

  For example, in the above-described embodiment, the composite container 1 is filled with the solution added with the solute (S2), and the solution added with the solute is introduced into the tank 20 (S3), and then the tank 20, the compressor 30 and the composite container are introduced. 1 is connected by pipes L1 and L2 (S4), but is not limited thereto. For example, the process of S2 and the process of S3 may be performed simultaneously, or the process of S2 may be performed after the process of S3 is performed first. For example, the process of S3 may be performed after the process of S4. Moreover, you may perform the process of said S2 after the process of said S4. That is, the solution containing the solute added from the tank 20 to the composite container 1 is pumped by the compressor 30 to fill the composite container 1. In this case, in the process of S3, it is necessary to introduce a solution in which a solute having an inner volume or more of the composite container 1 is added to the tank 20.

  Further, the preparation of the solution to which the solute has been added may be performed in the tank 20 or the composite container 1. That is, a solution in which a solvent and a solute are separately introduced into the tank 20 or the composite container 1 and the solute is added may be used. Moreover, the process of said S1 may be abbreviate | omitted and the solution which added the solute prepared beforehand may be used.

  DESCRIPTION OF SYMBOLS 1 ... Composite container, 2 ... Metal liner, 3 ... Reinforcement layer.

Claims (9)

A pressure cycle test method for a composite container having a reinforcing layer on the outer peripheral side of a metal liner and capable of holding a high-pressure gas,
A first step of filling the composite container as a pressure medium with a solution in which a solute is added to a solvent containing ethylene glycol;
A second step of communicatively connecting the composite container filled with the solution and a tank storing the solution, and repeatedly performing pressurization and depressurization of the pressure medium filled in the composite container for a plurality of cycles; only including,
The internal pressure of the composite container increases due to the pressurization of the pressure medium in the second step , and the internal pressure of the composite container is increased by the pressurization even when the reference pressure is not reached and when the reference pressure is reached. elevated and if the time to reach the reference pressure is equal to or greater than the reference time, and ends the second step, the pressure cycle test method of the composite container. The pressure cycle test method for a composite container according to claim 1 , wherein the ethylene glycol has a conductivity lower than 2 × 10 ⁻⁴ S / cm. The pressure cycle test method for a composite container according to claim 1 , wherein the ethylene glycol has a conductivity lower than 1 × 10 ⁻⁵ S / cm. The pressure cycle test method for a composite container according to claim 1 , wherein the ethylene glycol has a conductivity lower than 5 × 10 ⁻⁶ S / cm. The said ethylene glycol is a pressure cycle test method of the composite container as described in any one of Claims 1-4 whose amount of dissolved oxygen in 21 degreeC is less than 5 mg / L. The said ethylene glycol is a pressure cycle test method of the composite container as described in any one of Claims 1-4 whose amount of dissolved oxygen in 21 degreeC is less than 2 mg / L. The said solute is a pressure cycle test method of the composite container as described in any one of Claims 1-6 containing at least any one of an amine type and an organic acid type. The pressure cycle test method for a composite container according to any one of claims 1 to 7 , wherein an amount of the solute added is 1 to 10 wt%. The pressure cycle test method for a composite container according to any one of claims 1 to 8 , wherein the composite container is a hydrogen station pressure accumulator.

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