JP2020153503A - Pressure vessel inspection method - Google Patents

Abstract

To provide a method for producing a pressure vessel, in which the state of the produced pressure vessel may be easily determined in a non-destructive manner.SOLUTION: There is provided an inspection method for a pressure vessel in which dome parts 12 are provided at both ends of a straight drum part 10 and the straight drum part 10 and the dome parts 12 are formed of a container main body and a fiber-reinforced resin composite material layer. In the inspection method for a pressure vessel, with respect to a group of pressure vessels V1, V2, to Vi, to Vp consisting of p number of pressure vessels (provided that p is an integer of 3 or more) produced based on the same design for a working pressure P0 (MPa), under a state where a pressure PT (MPa) of the working pressure P0 or more is applied to each of the pressure vessels Vi,, distortion in a hoop direction is measured at 3 measurement points a1 to a3 different in the axial direction of the straight drum part 10, a standard deviation Xi is obtained, and the state of each of the pressure vessels Vi, is determined based on the standard deviation Xi.SELECTED DRAWING: Figure 4

Description

The present invention relates to a method for inspecting a pressure vessel.

A pressure vessel in which the container body is reinforced with a fiber reinforced resin composite material layer is lightweight and has a high pressure resistance, so that it is used as a fuel tank for automobiles and a tank used for storing and transporting gas and the like. The fiber-reinforced resin composite material layer is formed by, for example, wrapping a reinforcing fiber composite material containing a long reinforcing fiber bundle and a curable resin around the outside of the container body and curing it. A pressure vessel using carbon fiber having a high specific strength is easy to reduce in weight and is particularly suitable for a tank for moving gas.

Examples of the method for manufacturing the pressure vessel include a filament winding method (hereinafter referred to as FW method) using a reinforcing fiber composite material in which a long reinforcing fiber bundle is impregnated with a curable resin. For example, a reinforcing fiber composite material is wound around the outside of a resin container body, and then the curable resin is cured (Patent Document 1). The FW method when a curable resin is used includes a wet method and a dry method. In the wet type FW method, an impregnation operation of impregnating a long reinforcing fiber bundle with a curable resin to form a reinforcing fiber composite material and a winding operation of winding the reinforcing fiber composite material around a container body are continuously performed. In the dry FW method, a prefabricated reinforcing fiber composite material is wound around the container body. When using a reinforcing fiber composite material in which a long reinforcing fiber bundle is impregnated with a thermoplastic resin, the reinforcing fiber composite material is heated in the process of winding the reinforcing fiber composite material to melt the thermoplastic resin, and the reinforcing fiber composite materials are integrated with each other. After that, it is cooled and solidified.

Japanese Patent No. 4714672

The manufacturing conditions of the FW method are different for each method. In order to manufacture the pressure vessel as designed, it is necessary to arrange a predetermined amount of the reinforcing fiber composite material in a predetermined direction so as to fully exhibit the characteristics of the reinforcing fiber. However, in the production of pressure vessels by the FW method, it is difficult to precisely control the production conditions, and the performance such as burst pressure becomes stable due to defects such as voids and cracks that are the starting points of fracture, and displacement of reinforcing fibers. It may not be possible to obtain it. The cause of such performance deterioration cannot be confirmed unless the pressure vessel is destroyed, such as by cutting the pressure vessel. Therefore, there is a demand for an inspection method that can easily determine the state of the manufactured pressure vessel in a non-destructive manner.

An object of the present invention is to provide a pressure vessel inspection method that can easily determine the state of a manufactured pressure vessel in a non-destructive manner.

The present invention has the following configurations.
[1] A tubular straight body portion and dome portions provided at both ends of the straight body portion and having a shape that narrows as the distance from the straight body portion increases.
A method of inspecting a pressure vessel in which the straight body portion and the dome portion are formed of a container body and a fiber reinforced resin composite material layer provided on the outside of the container body.
Pressure vessel group V ₁ , V ₂ , ..., V consisting of p pressure vessels manufactured based on the same design as the working pressure P ₀ (MPa) (where p is an integer of 3 or more). _{For i} , ... V _p , with the pressure _PT (MPa) of the working pressure P ₀ or more being applied to each pressure container V _i , three or more different locations in the axial direction of the straight body portion are placed. q locations, including (but, q is an integer of 3 or more.) in seeking the standard deviation X _i by measuring the strain of the hoop direction, determines the status of the pressure vessel V _i using the standard deviation X _i How to inspect the pressure vessel.
[2] of the pressure vessel group, the n from the standard deviation X _i is smaller pressure vessel V _i in order (where, n is an integer from 1 to p.) And the state of the pressure vessel is good The method for inspecting a pressure vessel according to [1].
[3] For each of the pressure vessel _{V i,} wherein the standard deviation _{X i} variation coefficient of variation of distortion of the hoop direction from _Cv i (%), the pressure vessel by using the variation coefficient _Cv i (%) determining the state of V _i, the inspection method of the pressure vessel according to [1].
[4] The method for inspecting a pressure vessel according to any one of [1] to [3], wherein the pressure _PT satisfies the condition represented by the following formula (i).
1.0 x P ₀ ≤ P _T ≤ 1.5 x P ₀ ... (i)

According to the present invention, it is possible to provide a pressure vessel inspection method that can easily determine the state of a manufactured pressure vessel in a non-destructive manner.

It is a figure which showed an example of the pressure vessel of this invention, and is the sectional view cut along the axial direction of the straight body part. FIG. 5 is an enlarged cross-sectional view of the vicinity of the dome portion in the pressure vessel of FIG. It is a schematic block diagram which showed one process of the manufacturing method of a pressure vessel. It is a front view explaining the strain measurement in the straight body part of a pressure vessel. It is a front view explaining the strain measurement in the straight body part of a pressure vessel. It is a front view which showed the measurement point of the strain measurement in the straight body part of the pressure vessel in an Example. Is a diagram showing the relationship between the distortion and the pressure P _T in the respective measurement points a~e of the pressure vessel A of Example 1.

The method for inspecting a pressure vessel of the present invention includes a tubular straight body portion and a dome portion provided at both ends of the straight body portion and narrowing as the distance from the straight body portion increases. , A method for inspecting a pressure vessel formed of a container body and a fiber-reinforced resin composite material layer (hereinafter, also referred to as “composite material layer”) provided on the outside of the container body.

(Pressure vessel)
The pressure vessel to be inspected is a container in which a resin or metal container body is reinforced with a composite material layer that holds the container body against internal pressure. The pressure vessel is manufactured by the FW method. The container body has at least one opening in the dome portion for taking in and out the contents, and an openable / closable valve can be attached to the container body. The opening of the container body is provided with a metal processing part such as a mouthpiece for attaching a valve or attaching a jig at the time of manufacturing by the FW method. In particular, when the pressure vessel is large, by providing metal processing portions on both dome portions, it becomes easy to prevent the container body from being eccentric due to the tension when winding the reinforcing fiber composite material. The metal processing portion used only for attaching the jig may be provided without forming an opening in the dome portion.

As the pressure vessel to be inspected, for example, the pressure vessel 1 illustrated in FIG. 1 can be exemplified.
As shown in FIGS. 1 and 2, the pressure vessel 1 has a cylindrical straight body portion 10 and a hemispherical dome portion 12 provided at both ends of the straight body portion 10 and narrowing as the distance from the straight body portion 10 increases. And have. The straight body portion 10 and the dome portion 12 are referred to as a resin container body (liner) 2 and a fiber-reinforced resin composite material layer 3 provided on the outside of the container body 2 (hereinafter, referred to as “composite material layer 3”. ) Is formed by. A metal base 4 is provided at the tip of one of the dome portions 12 in the pressure vessel 1. The base 4 is sandwiched between the container body 2 and the composite material layer 3 at the tip of the dome portion 12 and is closely fixed.

The container body 2 is a resin container. The shape of the container body is not limited to the shape in which hemispherical dome portions are provided at both ends of the cylindrical straight body portion as in this example. The size of the container body may be appropriately set according to the use of the pressure vessel and the like. The thickness of the container body may be appropriately set according to the intended use of the pressure vessel, and can be, for example, about 1 to 30 mm. The container body can be manufactured by, for example, blow molding, rotation molding, injection molding, extrusion molding, and joining of parts formed by them.

As the material for forming the container body, a known material used for the pressure vessel can be appropriately used, and examples thereof include a material having a gas barrier property. Specific examples include, for example, polyolefin resins such as high-density polyethylene resins, crosslinked polyethylenes, polypropylene resins, and cyclic olefin resins; polyamide resins such as nylon 6, nylon 6, 6, nylon 11, and nylon 12; polyethylene terephthalates. Examples thereof include polyester resins such as polybutylene terephthalate; engineering plastics such as acrylonitrile-butadiene-styrene copolymer (ABS) resin, polyacetal resin, polycarbonate resin, polyphenylene ether resin, polyphenylene sulfide resin, polysulfone resin, and polyimide resin. .. The resin forming the container body may be one type or two or more types. The container body may have a single-layer structure or a multi-layer structure.

A resin such as ethylene-vinyl alcohol copolymer (EVOH) having a gas barrier property or a resin layer containing a flat-shaped filler may be inserted or bonded to the container body. Further, an adhesive layer for bonding the resin layers may be inserted. The outer surface of the container body is preferably smooth from the viewpoint of suppressing fatigue due to stress concentration.

The composite material layer 3 is a layer formed of a long reinforcing fiber bundle and a long reinforcing fiber composite material containing a resin. When a curable resin is used, the composite material layer 3 is made of a cured product of a reinforcing fiber composite material. In this case, the composite material layer 3 is formed by winding a long reinforcing fiber composite material in which the reinforcing fiber bundle is impregnated with the curable resin around the outside of the container body 2 and then curing the curable resin. To. In the composite material layer 3, the reinforcing fiber composite material circulates around the cavity 5 formed inside the container body 2.

By providing the composite material layer, the container body is reinforced and the burst pressure of the pressure vessel is increased. The composite material layer is provided so as to cover the entire outside of the container body. When the pressure vessel is provided with a cap, the composite material layer is provided so as to cover the entire vessel body, taking into account that the cap on the outside of the vessel body does not interfere with the locking of jigs and valves.

Examples of the reinforcing fibers forming the reinforcing fiber bundle include pitch-based, polyacrylonitrile (PAN) -based, and rayon-based carbon fibers, glass fibers, aramid fibers, and highly drawn polyethylene fibers, and carbon fibers are preferable. In particular, pitch-based carbon fibers are preferable because they have a high elastic modulus and the amount of deformation of the container body can be easily suppressed. PAN-based carbon fibers are preferable in that high strength can be easily obtained. When there is concern about electrolytic corrosion due to contact with a metal portion, it is preferable to use glass fiber, organic fiber, or the like having low conductivity for the contact portion with the metal. The reinforcing fibers forming the reinforcing fiber bundle may be one type or two or more types.
The number of filaments of the reinforcing fiber bundle per one is not particularly limited, and can be, for example, 6,000 to 60,000.

Examples of the resin forming the reinforcing fiber composite material include a curable resin and a thermoplastic resin, and a curable resin is preferable because the winding time of the FW can be shortened.
The curable resin is not particularly limited, and may be a thermosetting resin or a photocurable resin. Specific examples of the curable resin include epoxy resin, unsaturated polyester resin, urea resin, phenol resin, melamine resin, polyurethane resin, polyimide resin, vinyl ester resin and the like. As the curable resin, one type may be used alone, or two or more types may be used in combination.

The resin is blended with known additives such as a reactive diluent, a curing agent, an accelerator, a filler for preventing cracks, and a weather resistance imparting agent according to the physical properties required for the pressure vessel and the molding method. May be good.

The volume fraction of the reinforcing fibers in the composite material layer is preferably 55% by volume or more, more preferably 55 to 75% by volume. When the volume fraction of the reinforcing fibers is equal to or higher than the lower limit value, a pressure vessel having a high burst pressure can be obtained with a smaller amount of reinforcing fibers. Therefore, a lightweight pressure vessel having a high burst pressure can be manufactured at low cost. When the volume fraction of the reinforcing fiber is not more than the upper limit value, a pressure vessel having a good appearance and excellent fatigue resistance can be obtained.
For the body integration rate of the reinforcing fibers in the composite material layer, the resin in the sample was decomposed by a firing method, a melting method, etc., and the mass of the sample before and after the resin decomposition was measured with a balance to obtain the masses of the reinforcing fibers and the resin. After that, it is calculated using the densities of the reinforcing fibers and the resin.

The average thickness of the composite material layer can be appropriately set according to the desired burst pressure. Even if the burst pressure and the internal volume are constant, if the ratio L / D of the length L to the diameter D of the pressure vessel changes, the required average thickness also changes.
The average thickness of the composite material layer is preferably 1 to 35 mm, more preferably 4 to 25 mm. When the average thickness of the composite material layer is not less than the lower limit of the above range, the required burst pressure can be easily obtained. When the average thickness of the composite material layer is not more than the upper limit of the above range, the strength development rate of the reinforcing fibers is high, the weight of the pressure vessel can be easily reduced, and it is advantageous in terms of cost.

The form of the base can be a known form used for the pressure vessel. The base 4 in the pressure vessel 1 has a substantially cylindrical shape having a through hole. The shape of the inner surface of the base is designed according to the shape of the valve or the like mounted inside the base. For example, a female screw can be formed on the inner peripheral surface of the through hole of the base near the upper end, and a valve for supplying and taking out gas can be attached by screwing. A mouthpiece provided with a flange portion protruding in the radial direction in a substantially cylindrical portion having a through hole has a high effect of resisting the internal pressure of the container by covering the flange portion with a composite material layer.

The metal constituting the base is not particularly limited, and a known metal can be used. For example, aluminum alloy, stainless steel (SUS), carbon steel, alloy steel, brass and the like can be exemplified. The metal constituting the base may be one type or two or more types.
A material other than metal may be used between the base and the container body and between the base and the composite material layer for the purpose of gas sealing, adhesion, stress buffering, prevention of electrolytic corrosion, and the like.

(Production method)
The pressure vessel can be manufactured, for example, by a method in which a long reinforcing fiber composite material is wound around the container body and cured as necessary by the FW method. Various materials and conditions are set so that the movement of the reinforcing fiber from a predetermined position during winding, after winding, and during curing of the reinforcing fiber composite material is small.

As a method for manufacturing the pressure vessel, it is preferable to adopt a wet type FW method in which the reinforcing fiber bundle is impregnated with the resin and the reinforcing fiber composite material is continuously wound. For example, a reinforcing fiber base material in which a plurality of long reinforcing fiber bundles are aligned is impregnated with a curable resin to obtain a reinforcing fiber composite material. Subsequently, the reinforcing fiber composite material is wound around the outside of the container body, and then the curable resin is cured to form a composite material layer.
The method of impregnating the carbon fiber bundle with the curable resin is not particularly limited, and a known method can be adopted.

Specific examples of the method for manufacturing the pressure vessel include the following methods.
As shown in FIG. 3, the carbon fiber bundle 20 in which a plurality of long carbon fiber bundles are aligned is guided to the resin tank 100 containing the curable resin P by the plurality of guide rollers 102. The resin-impregnated roll 104 arranged so that the outer peripheral surface is in contact with the curable resin P in the resin tank 100 is rotated, and the curable resin P adhering to the outer peripheral surface is adhered to the carbon fiber bundle 20 and impregnated with carbon. The fiber composite material 22 is used. At this time, the scraper 106 is arranged on the outer peripheral surface of the resin-attached roll 104 so as to be separated from the outer peripheral surface by a predetermined distance on the side to which the curable resin P is attached, and the excess curable resin P is scraped off. Next, the carbon fiber composite material 22 is wound around the outside of the container body 2 and the curable resin P is cured to form a composite material layer.
By adjusting the distance between the outer peripheral surface of the resin-coated roll 104 and the tip of the scraper 106, the amount of the curable resin P adhered can be adjusted, and the volume fraction of carbon fibers in the carbon fiber composite material can be adjusted.

The resin viscosity when impregnated into the reinforcing fiber bundle is preferably 10 to 1000 mPa · s. When the resin viscosity is not more than the upper limit of the above range, the resin is likely to be impregnated in the reinforcing fiber bundle at the time of impregnation. When the resin viscosity is equal to or higher than the lower limit of the above range, it is easy to prevent the resin from scattering or moving between winding and before curing. The resin viscosity can be adjusted by adjusting the type of resin and the resin temperature at the time of impregnation.

When the resin viscosity is low in the wet FW method, it is preferable to rotate the container body at a speed at which the resin does not scatter so that the resin does not drip or move and is unevenly distributed. After wrapping the reinforcing fiber composite material, a resin film, tape or the like may be wrapped on the reinforced fiber composite material in order to prevent leakage or scattering of the resin. In the dry FW method, after impregnating the reinforcing fiber bundle with the resin, the resin viscosity at room temperature is generally higher than that in the wet method so that the resin does not move during storage until winding. It is preferable that the resin has a viscosity characteristic that allows the resin to flow during curing to fill the space between the reinforcing fiber bundles and the overlapping reinforcing fiber composite materials, and to prevent the resin from flowing out due to excessive flow.

The amount of resin in the reinforcing fiber composite material is set in consideration of filling the gaps between the fibers in the reinforcing fiber bundle after curing, the spaces between the fiber bundles, and the overlapping reinforcing fiber composite materials with resin. .. Further, it is preferable to set a slightly larger amount for the purpose of causing the entrained gas to flow out. However, if the amount of resin is too large, the resin may be squeezed out by tightening the wound reinforcing fiber composite material, and the reinforcing fibers may be displaced from a predetermined position and angle accordingly. When the amount of resin is small, voids (voids) may occur in the reinforcing fiber bundles, between the reinforcing fiber bundles, and between the reinforcing fiber composite materials. In the absence of large voids in the composite layer, it is less likely to affect burst testing by static pressurization, which depends on fiber strength. However, if there are a large amount of voids, it will trigger resin destruction and reduce fatigue performance.

The volume fraction of the reinforcing fibers in the reinforcing fiber composite material is preferably 55 to 75% by volume. When the volume fraction is at least the lower limit of the above range, the burst pressure is high, and a lightweight and low-cost pressure vessel can be easily obtained. When the volume fraction is not more than the upper limit of the above range, it is easy to obtain a pressure vessel having a good appearance and excellent fatigue resistance.

The method for curing the curable resin may be appropriately selected according to the type of the curable resin. Specifically, when a thermosetting resin is used, it is cured by heating, and when a photocurable resin is used, it is cured by light irradiation.

In the manufacture of pressure vessels by the FW method, the form of winding the reinforcing fiber composite material does not become the desired form due to the influence of each process, voids and the like that are the starting points of fracture are generated in the composite material layer, and the burst pressure is increased. May decrease. For example, if the step becomes large at the overlapping portion of the reinforcing fiber composite material, gas is entrained and a void is generated. In the dry method, a resin having a higher viscosity than in the wet method is generally used, so that the resin does not easily flow after winding, which may cause voids. In the wet method, the shape, tension, impregnation time, resin viscosity, resin adhesion amount, etc. of the reinforcing fiber bundle are likely to fluctuate due to changes in the surrounding environment, vibration during operation, etc., and voids occur when the resin amount of the reinforcing fiber composite material decreases. Occurs.

In the wet method, there is a void countermeasure that increases the fluidity of the resin and expels the gas entrained before curing. However, in this method, since the highly fluid resin drips from the wound reinforcing fiber composite material before curing, it is necessary to set a large amount of resin in the reinforcing fiber composite material. Therefore, as the excess resin is squeezed out, the reinforcing fibers are loosened especially in the inner portion close to the container body, and the fibers are likely to meander or bend. When the reinforcing fibers meander or bend and are misaligned, the strength development rate of the reinforcing fibers decreases and the burst pressure decreases.

In this way, it is difficult to completely prevent voids and displacement of reinforcing fibers by controlling the manufacturing conditions. If the winding amount of the reinforcing fiber composite material is increased, a pressure vessel having a sufficiently high burst pressure can be obtained, but the pressure vessel becomes heavy and the cost increases. Since a pressure vessel subjected to a destructive test cannot be used, a method for inspecting the pressure vessel by a non-destructive test is particularly important in order to obtain a lightweight pressure vessel.

(Inspection method)
The pressure vessel inspection method of the present invention can inspect the condition of the pressure vessel by a non-destructive test. Specifically, the pressure vessel inspection method of the present invention has the following steps (x) and (y).
(X) Pressure vessel group consisting of p pressure vessels manufactured based on the same design as the working pressure P ₀ (MPa) (where p is an integer of 3 or more) V ₁ , V ₂ , ... _·, V i, for · · · _{V p,} for each of the pressure vessel _{V i,} in a state loaded with working pressure _{P 0} or more pressure _P T (MPa), different three or more in the axial direction of the cylindrical body portion The strain in the hoop direction is measured at q points including (where q is an integer of 3 or more).
(Y) a standard deviation X _i of the distortion in the hoop direction of the q points, to determine the state of the pressure vessel V _i using standard deviation X _i.

p is an integer of 3 or more, and an integer of 3 to 200 is preferable.

The working pressure P ₀ is the maximum value of the internal pressure at the time of use set in advance for the pressure vessel to be manufactured.
The pressure _PT , that is, the test pressure, preferably satisfies the condition represented by the following formula (i) from the viewpoint of increasing the inspection accuracy.
1.0 x P ₀ ≤ P _T ≤ 1.5 x P ₀ ... (i)
The pressure _{P T} is within a range that does not cause damage to the pressure vessel, with respect to working pressure _{P 0,} preferably 1.0 times to 1.5 times or less, particularly preferably 1.5 times. If the pressure _PT is at least the lower limit value, the strain range during use can be covered, and if it is within the upper limit value, there is little possibility of increasing defects in the container. The pressure _PT can be adjusted, for example, by filling the pressure vessel with water.

In step (x), to measure the strain in the hoop direction by q positions containing more than three different in the axial direction of the straight body portion of the pressure vessel V _i.
In pressure vessels manufactured by the FW method, the reinforcing fiber composite material in the hoop direction is the most critical to the burst strength so that the vessel generally breaks in the direction perpendicular to the axial direction of the straight body and the fractured part does not scatter. Designed to be. Therefore, the strain is measured along the hoop direction in order to see the correlation between the burst pressure and the strain. Specifically, the strain in the fiber axis direction of the reinforcing fiber bundle in the hoop layer of the straight body of the pressure vessel is measured.

The strain measurement points are q points including three or more points that differ in the axial direction of the straight body portion.
In the present invention, the measurement points of q points include two points near the boundary between the dome portions on both sides in the axial direction of the straight body portion and one point in the center in the axial direction of the straight body portion, for a total of three points. Is preferable. For example, as shown in FIG. 4, two measurement points a1 and a3 in the vicinity of the boundary between the straight body portion 10 and the dome portions 12 on both sides and one measurement point a2 in the center of the straight body portion 10 in the axial direction. And are arranged in the axial direction of the straight body portion 10. As long as the positions are different in the axial direction of the straight body portion 10, the three measurement points a1 to a3 may be set to different positions in the circumferential direction as shown in FIG.

If the q measurement points include three or more measurement points that differ in the axial direction of the straight body, the axial direction of the straight body includes two or more measurement points that differ in the circumferential direction. You may. It is preferable that all q measurement points are located at different positions in the axial direction of the straight body portion in that the correlation between the strain and the burst pressure is high and the inspection accuracy of the state of the pressure vessel is high.

q is an integer of 3 or more, preferably an integer of 3 to 15, and more preferably an integer of 3 to 6. When q is equal to or higher than the lower limit of the above range, the state of the pressure vessel can be inspected with high accuracy. When q is equal to or less than the upper limit of the above range, an increase in cost and a workload can be suppressed.

The strain measuring method is not particularly limited, and examples thereof include a strain gauge method, an optical fiber method, and an image correlation method.

In step (y), a standard deviation X _i hoop direction of the distortion of the q points, to determine the state of the pressure vessel V _i using standard deviation X _i.
The standard deviation X _i is obtained from the following equations (1) and (2).

However, the above formula (1) and (2), epsilon ⁱ _j is a measure of the distortion of the j point th of the pressure vessel _{V i.} ε ⁱ _ave is the average value of the strain at q points of the pressure vessel V _i .

For example, of the pressure vessel group, n pieces from the standard deviation X _i is smaller pressure vessel V _i in order (where, n is an integer from 1 to p.) States the pressure vessel is determined to be good. n can be appropriately set according to the design of the pressure vessel, such as the working pressure P ₀ , the material of the container body and the composite material layer, and the molding conditions.

In the present invention, from the viewpoint of easily compared with other containers, for each of the pressure vessel V _i, determined from the standard deviation X _i of variations in the hoop direction of the strain variation coefficient Cv i _(%), the variation coefficient Cv _i (%) it is preferable to determine the state of the pressure vessel V _i with.
Variation coefficient Cv _i is determined from the following equation (3).

The coefficient of variation Cv _i correlates with the burst pressure of the pressure vessel, and the lower the coefficient of variation Cvi _i , the higher the burst pressure of the pressure vessel. Therefore, by setting the threshold value of the variation coefficient Cv _i depending on the design of the pressure vessel, within the pressure vessel group produced can be variation coefficient Cv _i is less of a pressure vessel threshold condition is determined to be good ..
The threshold value of the coefficient of variation Cv _i can be appropriately set according to the design of the pressure vessel, and can be set to 10%, for example, in the case of the material, laminated structure, shape, and manufacturing conditions as in the manufacturing example described later.

As described above, in the present invention, strain in the hoop direction is applied to each of the p pressure vessels at q points including three or more different points in the axial direction of the straight body portion in a state where the pressure _PT is applied. measured, to determine the state of the pressure vessel V _i using the standard deviation X _i. Standard deviation X _i, and the variation coefficient Cv _i obtained from the standard deviation X _i, since it is correlated with the burst pressure of the pressure vessel, it is possible to determine the state of the pressure vessel in a non-destructive. As described above, according to the pressure vessel inspection method of the present invention, it is possible to non-destructively determine whether or not the burst pressure is reduced due to the generation of voids, meandering or bending of the reinforcing fiber bundle, etc., so that the pressure vessel having a high burst pressure can be used. It can be secured stably.
Further, since the pressure vessel having a high burst pressure can be secured without excessively increasing the winding amount of the reinforcing fiber composite material, the weight of the pressure vessel can be reduced, which is advantageous in terms of cost.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to the following description. In this example, a plurality of pressure vessels were manufactured by changing the amount of resin attached to the carbon fiber bundle, and the state was confirmed.
[material]
The raw materials used in this example are shown below.
(Carbon fiber bundle)
Carbon fiber bundle (A-1): Trade name "Grafil 37-800WD" manufactured by Mitsubishi Chemical Carbon fiber and Companies (number of filaments: 30,000, fiber fineness: 1.675 g / m).

(Curable resin composition)
Curable resin composition (B-1): Bisphenol A type epoxy resin (manufactured by Huntsman, trade name "Araldite LY 564/1564") with respect to 100 parts by mass of a curing agent (manufactured by Huntsman, trade name "Aradur 917"). A composition containing 98 parts by mass of ") and 3 parts by mass of an accelerator (manufactured by Huntsman Corporation, trade name" Accelerator 960-1 ").

(Resin for container body)
Container body resin (C-1): Polyethylene resin (manufactured by Japan Polyethylene Corporation, trade name "Novatec HB111R").

(Cap)
From the block obtained by subjecting the aluminum alloy 6061 to the heat treatment T6, a joining screw to the container body and a threaded mouthpiece for attaching the shaft of the FW device and the pressure nozzle were obtained by cutting.

[Manufacturing Example 1]
The container body 2 illustrated in FIG. 1 was produced by blow molding using the container body resin (C-1). An aluminum adhesive was applied to the threaded portion of the base joint at the tip of the dome portion of the container body 2, and the base 4 was screwed and fixed.
Set the target burst pressure sufficiently larger than the working pressure P ₀ (MPa) as shown in Table 1, adjust the resin attachment amount and winding amount of the carbon fiber composite material so as to satisfy it, and apply the pressure by the FW method. Containers A to I were manufactured.
Specifically, a curable resin composition (B-1) is attached to a long carbon fiber bundle (A-1) using a resin-impregnated roll 104, wound around the outside of the container body 2, and then cured. The mixture was heated at 95 ° C. and cured to obtain a pressure vessel. The heating time (curing time) in the curing furnace was determined in the range of 2 to 12 hours depending on the winding amount of the carbon fiber composite material. During production, the distance between the outer peripheral surface of the resin-coated roll 104 and the tip of the scraper 106 is adjusted, and the thickness of the curable resin composition (B-1) on the outer peripheral surface of the resin-coated roll 104 is adjusted. The amount of the curable resin composition (B-1) attached to the carbon fiber bundle (A-1) was adjusted.

[Container expression rate]
The burst pressure of each pressure vessel was measured with a hydraulic pressure tester. The ratio of the measured value of the burst pressure to the target burst pressure was calculated as the container expression rate.

[Example 1]
The condition of the pressure vessels A to I was inspected by the following three inspection methods.
(Inspection method I)
In the straight body of the pressure vessel with a pressure _PT (MPa) 1.5 times the design working pressure P ₀ , the vicinity of the boundary with the dome on both sides in the axial direction and three points in the center. The strain in the hoop direction at the measurement points a to c in FIG. 6 was measured using a strain gauge, and the coefficient of variation Cv _i of the strain in the hoop direction was obtained from the equations (1) to (3).

(Inspection method II)
In addition to the three points of the inspection method I, the strains in the hoop direction at two points 90 ° in the circumferential direction from the measurement point b in the inspection method I were similarly measured at the center of the straight body in the axial direction, for a total of 5 points. It was determined variation coefficient Cv _i from the point with the hoop direction of the strain (measurement point a~e 6) equation (1) to (3).
Figure 7 shows the relationship between the distortion and the pressure P _T in the respective measurement points a~e of the pressure vessel A.

(Inspection method III)
Equations (1) to (3) using the strain in the hoop direction at three points in the circumferential direction (measurement points b, d, and e in FIG. 6) in the center of the axial direction of the straight body measured by the inspection methods I and II. to determine the coefficient of variation Cv _i from.
Standard deviation _{X i} and coefficient of variation Cv _i by each test method are shown in Table 1.

As shown in Table 1 and Figure 7, the inspection method I, II using a strain of the hoop direction of the axis directions of three different places of the straight body portion is found a correlation between the variation coefficient Cv _i and the container incidence, variation The lower the coefficient Cvi, the higher the container expression rate. In particular testing method I only was used strain hoop direction of the axis directions of three different places of the straight body portion was higher correlation with the variation coefficient Cv _i and the container incidence.
On the other hand, in the inspection method III using the strains in the hoop direction at three points different in the circumferential direction of the straight body portion, the correlation between the coefficient of variation Cvi and the container expression rate was low.

1 ... Pressure vessel, 2 ... Container body, 3 ... Fiber reinforced resin composite material layer, 4 ... Base, 10 ... Straight body, 12 ... Dome.

Claims (4)

It is provided with a tubular straight body portion and dome portions provided at both ends of the straight body portion and having a shape that narrows as the distance from the straight body portion increases.
A method of inspecting a pressure vessel in which the straight body portion and the dome portion are formed of a container body and a fiber reinforced resin composite material layer provided on the outside of the container body.
Pressure vessel group V ₁ , V ₂ , ..., V consisting of p pressure vessels manufactured based on the same design as the working pressure P ₀ (MPa) (where p is an integer of 3 or more). _{For i} , ... V _p , with the pressure _PT (MPa) of the working pressure P ₀ or more being applied to each pressure container V _i , three or more different locations in the axial direction of the straight body portion are placed. q locations, including (but, q is an integer of 3 or more.) in seeking the standard deviation X _i by measuring the strain of the hoop direction, determines the status of the pressure vessel V _i using the standard deviation X _i How to inspect the pressure vessel. Among the pressure vessel group, the n from the standard deviation X _i is smaller pressure vessel V _i in order (where, n is an integer from 1 to p.) States the pressure vessel is determined to be good, The method for inspecting a pressure vessel according to claim 1. For each of the pressure vessel _{V i,} wherein the standard deviation _{X i} of the distortion of the hoop direction determined coefficient of variation of the variation _Cv i (%), of the pressure vessel _{V i} using the coefficient of variation _Cv i (%) The method for inspecting a pressure vessel according to claim 1, wherein the state is determined. The method for inspecting a pressure vessel according to any one of claims 1 to 3, wherein the pressure _PT satisfies the condition represented by the following formula (i).
1.0 x P ₀ ≤ P _T ≤ 1.5 x P ₀ ... (i)

Images