JPS58214832A - Weld crack detection for multi-layer wrapped pressure vessel - Google Patents

Abstract

PURPOSE:To capture the position and the form of weld cracks by detecting variation in the original pressure or gas from adjacent layers when gas is forced into layers of a multi-layer wrapped pressure vessel through a gas feed hole provided communicating between layers. CONSTITUTION:In a multi-layer wrapped pressure vessel, an inverted-cone-shaped detection hole T1 is drilled so as to reach the surface of the innermost layer 3 from the outermost layer 10 and a nozzle 11 is fitted thereinto. Gas pressure feed heads 12-14 adapted to force gas in groups between layers ended in inter- layer 13, 11 and 12 arranged at invervals of 4 inter-layers starting from inter- layers 1, 2 and 3 and a detection head 15 for checking the sealing property of inter-layers are projected on the top surface of the nozzle 11. A valve 17 is opened to feed a gas to the head 12 with a fixed pressure in a high pressure vessel 23 and the sealing property of an O ring 16 with a head 15. Then, the presence, the position and the form of weld cracks are captured depending on the outflow of the gas from the heads 13 and 14 or drop in the pressure of a manometer 24.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting cracks in seam welds in a multi-layer pressure vessel having KV seam welds in each layer by a simple means, and in particular, immediately after manufacture and during use. The present invention relates to a method that can always obtain accurate detection results regardless of the situation.

Since the multilayer pressure vessel is made of thin plates, it has the advantage of being highly reliable in terms of materials, and the use of high-strength thin plates has the advantage of increased fracture resistance. Also, from the perspective of the manufacturing process, there is the advantage that the two problems (ingot-forming ability, forging press ability, mortaring ability, etc.) that occur when manufacturing a single-layer pressure vessel are not encountered. For this reason, it has attracted attention in various chemical industry fields, but because cracks in welds cannot be detected from the outside, they are exposed to temperatures of up to 400 degrees Celsius at most, and there are no changes in internal pressure. It has only been used as a container for applications where there is little temperature change, in other words, under mild conditions where there is no return load η, and it cannot be said that its reliability is sufficient. Therefore, in the development of containers that are used under conditions where repeated loads are applied, we need to develop a method to accurately and easily detect and detect cracks in welds, not only immediately after table a, but also during use. is desired, but has not yet been provided.

In other words, there are various manufacturing methods for multilayer pressure vessels, and a method has been developed in which a plate with an extremely wide area is rolled up into a coil shape and the final attachment part is welded in the axial direction according to the method of lap joints, but There are limitations in manufacturing thin sheets with a vast surface area that spreads in the lateral direction, and there are also various difficulties in the technology of winding such large-area thin sheets into coils, making it less versatile. Missing. Therefore, it is necessary to rely on the following method that involves a large number of welds, and detection of cracks in welds that cannot be observed from the outside has become a serious issue. That is, to explain the welding procedure that is currently widely used in accordance with Figs. , butt portions are welded in the axial direction to form a seam joint 2'a, 2
Form L b , 2/c. In FIG. 2, eight thin plates 3a, 3b, and 3c are attached in a curved manner around the innermost thin plate 2, and the three butt parts are welded in the axial direction to form a seam joint 3'a.

3'b and 3'c are formed. The same seam joint is shifted little by little so that it does not overlap the seam joint of the previous layer (the same applies hereafter). In Fig. 3, three thin plates 4a and 4b are added above it.
, 4c are attached respectively to seam joints 4'& 4:b.
, form A C, and in Fig. 4, eight thin plates 5 are further placed on top of it.
Seam joints 5'a, 5b and 5c are attached respectively.
5'b and 5'c are formed. Thereafter, the same procedure is repeated to form a multi-layered cylindrical body consisting of a large number of calendars, the cylindrical mold 1 is removed at the end K or at any stage along the way, and the cylindrical bodies and a suitable end plate are butt-welded and circumferentially welded. Manufacture and install multi-layer pressure vessels. However, with this method, it is necessary to weld three seam joints for each layer, so we split the laminated thin plates into two and made two seam joints for each layer, Figure 5.6. As shown in (8)
4・------) Winding is done by hand welding one seam each (3
There is also a method of stacking layers using ``, i------). Since these methods do not have the drawbacks seen in the coil winding method described above, they are becoming mainstream in the production of current multilayer pressure vessels, but the seam joint welding line of each layer is Not only is it impossible to observe from the outside as it is covered by the rolled thin plates, but even if you try to apply ultrasonic flaw detection, it is impossible to obtain highly reliable results because there are gaps between each layer. . As of now, no method has been found to accurately detect defects that occur in each welded part and are hidden inside. After assembling this multilayer cylindrical body as a pressure vessel, the high pressure gas inside the vessel leaks through the hole m111It, which reaches the surface of the innermost layer in the direction perpendicular to the center of the pressure vessel. A method has also been proposed to detect weld cracks by detecting the occurrence of cracks in the weld, but according to this method, if a crack occurs in the innermost seam joint (2' in Figures 1 to 6), , the gas inside the container passes through the crack to the innermost layer and its outer circumference J! Since the DC leakage is detected when it is dispersed into the hole mentioned above, a crack in the innermost layer weld is only discovered at the 2M and 8H.

4-It is impossible to discover the bath contact cracks.

The present invention has been made with attention to such a situation, and is based on the following: When a detection hole reaching the surface of the innermost layer is drilled in a direction perpendicular to the fine details of a multi-layered pressure vessel, and fluid is injected between certain layers. The present invention provides a method capable of detecting cracks in a seam weld temporarily formed between the layers by detecting fluctuations in the source pressure of the fluid or the fluid from adjacent layers. Therefore, it is now possible to conduct non-destructive inspections of the inside of a multilayer pressure vessel, not only immediately after manufacturing, but also during actual use. It has become possible to use it for various purposes.

FIG. 7 is an explanatory cross-sectional view showing the principle of detecting weld cracks according to the present invention). In order to make it easier to understand, the interlayers of each thin plate are exaggerated and are represented by ■1■ and ■, respectively.

Detection holes T1 and T2 reaching the surface of the innermost tube 20 are formed, and nozzle members 8 and 9 each having a fluid passage hole are inserted therein. Further, M indicates weld metal of seam welding formed in a direction penetrating the plane of the paper, and in the figure, a weld crack Wl has occurred at the interface with the base metal. There are two ways to discover weld cracks Wl. In either method, pressurized fluid (hereinafter typically referred to as pressurized gas) is supplied from the direction of the arrow, and the nozzle V member 8 is closed. Inject into the interlayer ■. The injected gas passes through the interlayer ■, weld crack = r1, and interlayer ■, reaches the nozzle member 9, and is recovered in the direction of arrow B. Therefore, the source pressure decreases on the pressurized gas supply side, or the beating pressure An increase in gas pressure or the presence of gas (in the case of a special gas) in the concave joint 1 can be detected, and if either of these is detected, the existence of a weld crack wl can be inferred. For example, there is W2 shown in the 8th ward, and in this case, the interlayer ■ and the interlayer ■
, and the interlayers ■ and the interlayers ■ are not communicated (the interlayers ■ and the interlayers ■ are communicated. Therefore, for example, the pressurizing force "is pressed into the interlayer ■ from the full arrow A, and from the interlayer ■ through the nozzle member 9. By passing it in the direction of arrow B, welding
I can infer the existence of 2. Figure 9.10 shows another pattern of weld cracking.
Since the interlayer ■ force S is in communication with each other, it can be detected as a weld crack W3 by applying the means shown in Fig. 7. In Fig. 10, the interlayer ■, ■, and ■ are in communication with each other, so the interlayer ■
By applying the means in Figure 7 between the layer ■ and the layer ■ and between the layer ■ and W115■, or applying the means in Figure 8 between the layer ■ and the darkness ■, by these means. If the presence of all lj cracks is detected, it can be determined that there is a bath v: crack W4.

Next, I will explain the method of the present invention a little more concretely (but in principle).
The explanation is shown in FIG. 11. Although the number of layers of the multi-layer pressure vessel varies depending on the design pressure, it is assumed to be 14 degrees for convenience of explanation below. Further, each button hole is divided into three groups, and the gas holes 25 of the nozzle member are made to face every second layer in each group. That is, in the first group, the interlayer ○゛, <1
．．・J, Q+l+, ○, 2nd chicken group, interlayer ■, ■, ■, ■, 3rd group) 1, make Ganosu hole 25 face each of the tatami volume ■, ■, ■, 0. ing. The left side of the commercial diagram shows the arrangement of the gas holes mentioned above,
On the right side, detectable defects (W1 to W4 above have the same meanings as above) are shown in a corresponding manner. Now, pressurize gas for one group again, and interlayer σ) from each gas hole 25 of the nozzle member, ■
Suppose that gas is injected into , ■, ■, and ■. At this time, if there is a weld crack Wl shown in [phase], gas leakage from the outermost layer or a drop in the source pressure will be observed (the description of the drop in the source pressure will be omitted in the following explanation) ). Also, if the weld crack shown by ■ is 9, the interlayer ■
Gas leakage from the detection port O is observed because the gas from the layer enters the interlayer ■. Furthermore, if there is a weld crack W4 indicated by ■, the interlayer ■ communicates with both the interlayers ■ and ■, so gas leakage is observed from both the detection ports ■ and ■. If there is a weld crack W2 as shown in the figure below, gas leakage from the detection port 0 is detected because the interlayers ■ and interlayers ■ are communicated with each other. The remaining weld cracks not shown with drawing numbers are detected in the same way, and once the detection is completed, the second weld crack is detected.
A similar detection operation is performed by pressurizing gas into the group, and then switching to gas injection into a third group to complete the detection operation. In each of the above explanations, we have described the gas leakage situation at each detection port when there is a weld crack, but the position and type of weld crack (first to
It is extremely difficult to determine all of the problems shown in Figure 4, considering that the number of weld cracks may increase and most of the layers may be in communication. Therefore, if you perform detection operations regularly and frequently not only immediately after manufacture, but also during use, and strive to detect bath weld cracks early, you will be able to accurately detect the location and type of weld cracks one by one. I can do it. However, as the number of weld cracks increases, the distribution of detection ports where gas leaks are observed expands, so a correlation table of 0 gas leaks corresponding to each weld crack is prepared in advance. It is recommended that efforts be made to discover new weld cracks based on
Based on this, the first method for detecting weld cracks will be explained. FIG. 12 is a plan view of a nozzle member (hereinafter referred to as nozzle A/) used in the apparatus of the present invention, and FIG. 13 is a broken-down field view of the main parts showing the state in which the nozzle is installed in the detection hole. A detection hole T1 in the shape of an inverted truncated cone is drilled in the multilayer pressure vessel, reaching from the outermost layer 1O to the surface of the innermost layer 2, and a nozzle 11 S is fitted into the detection hole T1. On the top surface of the nozzle 11, there are gas injection heads 12, 18, 14 (!:, detection heads 15 for checking the sealing properties between each layer) that can pressurize gas into each of the above-mentioned 1st to 8th groups. The head 12, which is projected and projected onto the first group, has interlayers shown in FIG.
Gas inlet holes 25 (5 not included) are drilled that lead to ■, ■, 0υ, and ○, and four gas inlet holes are drilled in each of the other heads 18 and 14 that lead to the other layers. . In each layer, two wires are provided between the inner peripheral surface of the detection hole and the outer peripheral surface of the nozzle 11. - When the ring 16 is installed, it prevents the press-fit gas from leaking from between the inner peripheral surface of the detection hole and the outer peripheral surface of the nozzle. Gas is discharged through the O-ring 1, which is sealed at that position, and the seal failure is detected.
6 should be replaced. After confirming that there is no leakage in this way, pulps 17 to 19 are processed according to the first part of Figure 11.
is activated to detect communication between layers based on weld cracks. If the sealing characteristics of each O-ring have sufficient reliability and reliability, the detection head 1 only for detecting gas leaks can be used.
5 and all of the gas vent holes 20 following this, and the first
~ 3 groups of heads 12.13゜14 and the gas inlet holes provided there are used to apply lateral pressure (see Section 14.16), and O-rings for sealing are attached to each layer of lateral pressure material. All you need to do is place them one by one.

Next, a specific procedure for inspecting weld cracks using the apparatus shown in FIG. 13 will be described. First, pulp 22.1
7 and set the pressure inside the high-pressure container 23 to, for example, Pl, and at the same time, the respective accumulated amounts ■, ■, ■ are sent from each gas inlet of the first group.
, [phase], DK is filled with pressurized gas, and the above pressure is 21
After confirming that V is set at , the pulp 22 is closed. After detecting gas leakage from the gas leak detection head 15 and confirming that the sealing performance by the O-ring is reliable, the second group of heads 13 and the third group are outflow of gas from the collective head 14;
Alternatively, the presence or absence of weld cracking can be determined by checking the pressure drop in the high-pressure vessel 23 measured by the pressure gauge 24.

When detecting the outflow of gas from the head 18.14, either apply soapy water to the air outlet of the gas inlet hole and check for bubbles, or use a special gas (such as Freon gas or H
If gas (e.g. gas, etc.) is used, check using a gas detector designed specifically for the husband. Further, when confirming the presence of weld cracks using the pressure gauge 24, if there is only a temporary pressure drop and the pressure remains constant thereafter, it is better to determine that there is no weld crack.

If there is a weld crack, it can be easily identified because the pointer of the pressure gauge 24 decreases as K 111 iR over time.

In the example shown in FIG. 13, a system in which a common tatami pressure container 23 is connected to each head 12, 18.14, K as shown in FIG.
, it is also possible to connect a separate high-pressure vessel to each head. In the figure, each symbol with suffixes a, b, and c has the same meaning as in FIG. 12.18. That is, the heads 12, 18, and 14 of each of the first to third groups are provided with independent high-pressure vessels 28a, 23b, and 28cfK, respectively, and p1. p2. A gas body having a pressure of p3 is introduced (PL>P2>P3'). Then, after a certain period of time has passed and the pointers of the pressure gauges 24a, 24b, 24c reach a stable state (3), the pulps 22a, 22b.

22Q is closed and the pressure fluctuations inside each high pressure container 2aa, 2ab, 2ac are observed. If no weld cracks occur, the pressure P l * P 2 s P 3 will hardly change, but if there is an IM crack Wl, a two-layer crack W4. If a bath contact center crack W2 had occurred, a pressure change 1 as shown in FIG. 15 would be observed. That is, in the case of (mu), Pl and P
The direction in which the pressure difference of 2 is equalized, (for b+, tiP1.
P2. Pressure fluctuations occur in the direction in which the pressure difference at P3 is smoothed out, and in the case of (C), in the direction in which the pressure difference between Pl and P2 is smoothed out. For example, changes such as the one shown at 111m1K on the right in No. 15 Acknowledgment 1 f) s observation be done. However, the absolute amount of pressure change and welding damage
There is no direct causal relationship between this and the other paddles, and no paddles have been found that suffered from weld cracks. However, since it is easy to measure, it can be used for continuous observation. ShoPl
= One of P2 + P3 (specifically P3) may be measured at atmospheric pressure, but if the first group described above is continued to P3, even if a weld crack occurs in the innermost layer, it will be detected. Therefore, a system in which the outer circumferential surface of the innermost layer (interlayer ■ in FIG. 11) is communicated with atmospheric pressure should be avoided.

FIG. 16 is a sectional view showing another embodiment of the device, and FIG. 17 is a plan view thereof. The nozzle has gas inlet holes 25 (14 holes) corresponding to the number between the layers, and 12 O holes.
- A ring 16 is attached to surround the nozzle.

Therefore, each inlet hole 25 is completely independent and opens with its tip facing between the layers. Fig. 18 is an explanatory diagram for detecting weld cracks. In detecting weld cracks, gas is first injected in the direction of the arrow ■' from the gas inlet hole 25 communicating with the interlayer ■. ■Describe the gas leaking from. Next, gas is injected under pressure in the direction of arrow {circle around (2)} from the gas inlet hole 25 communicating with interlayer {circle around (2)}, and the outflow of gas from interlayers 0 and {circle around (2)} is examined. In this way, the same operation is repeated while shifting the gas introduction toward the surface one by one, and as a result, weld cracks are sequentially detected. For example, if there is a weld crack Wl in the second laminated material from the innermost layer, the gas injected along the arrow O' will be transmitted from the interlayer @ to the interlayer O, and the gas will come out in the opposite direction to the arrow O' ( Further, if there is a weld crack W4 on the outer layer side, the gas injected into any one of the interlayers ■, ■, ■ will communicate with each other, and the arrow ■' , ■', 0' in the opposite direction, so this can also be detected correctly.Furthermore, if there is a weld crack W2 on the outer layer side, the interlayer ■ or ■ The gas injected into either side is communicated with each other, and the arrow ■′ or ■′
This can also be easily detected as it flows out in the opposite direction along one of the two directions.

The method for detecting weld cracks has been clarified through the above explanations, but as can be easily understood from the above explanations, the number of nozzles to be installed in a multi-layer pressure vessel is the same as the number of two-volume contact points in one layer. Must. In addition, the preliminary drawings so far have shown cases where the back bead melts into the surface of the inner layer side thin plate and the interlayer is interrupted, as shown in Figures 7 to 10, for example, but when the back bead is shallow If so, the living room will be continuous in that part. For example, in Fig. 19, the interlayers ■, ■', ■
If the gas is injected only from the nozzle ■ when the two layers are fully connected, the gas will flow from the interlayer ■' to the other interlayers ■, ■.
′ may lead to measurement errors. I recommend injecting gas at the same pressure from other nozzles ■' just in case.

Figure 20 is a piping and wiring diagram suitable for detecting weld cracks using the device shown in Figure 12.18.
Reference numerals 02 and 204 to 216 each indicate a three-way solenoid valve, which is configured to operate according to instructions from a control unit 230 and is connected to a high pressure vessel P (c). Reference numerals 217 to 229 are pressure transducers.

Since they are connected to the three-way solenoid valves 204 to 216, respectively,
For example, when the pressure medium is introduced between the layers of the first group, ■, ■, ■, ■, ■, between the layers of the second and third groups, ■, ■,
Gas leakage from ■, ■, ■, ■, ■, ■ is transmitted through the respective pressure transducers 222-229 to a comparator group 281 (representatively shown by 288 and 233') and compared with a reference voltage 234. . As a result, when the reference voltage is exceeded, the LED indicated by 232 lights up, and the position of the weld crack can be determined from the distribution. Reference numeral 201 is a pressure gauge, and the output voltage of the pressure transducer 235 is compared with a reference voltage 237 (2(6)), and if it is lower than the reference voltage, an LED 238 is turned on. Weld cracks (0 in Figure 11) leading to can be detected.

As described above, the present invention provides a gas inlet hole that communicates between each layer of a multilayer pressure vessel, injects gas under pressure, and detects the presence of weld cracks by detecting changes in the source pressure or gas from other layers. Therefore, it is possible to grasp the location and form of weld cracks, understand the physical property situation of multilayer pressure vessels,
Moreover, it has become possible to make predictions about its safety.

Therefore, the field of application of multi-layer pressure vessels can now be greatly expanded.

[Brief explanation of drawings]

Figures 1 to 6 are cross-sectional explanatory views showing the manufacturing procedure of a multi-layer pressure vessel, Figures 7 and 8 are detailed explanations of the present invention, Figures 9 and 10 are cross-sectional views of main parts showing the situation of weld cracking, and Figure 11. 12 is a plan view of the gas injection nozzle used in the present invention, FIG. 13 is a sectional explanatory view showing the usage condition, and FIG. 14 is the usage condition according to another embodiment. Fig. 15 is a pressure fluctuation graph when there is a weld crack, Fig. 16 is a plan view of
The figure is a cross-sectional view of usage form (■) according to another embodiment, FIG. 17 is a plan view thereof, FIG. 18 is an explanatory diagram for detecting weld cracks,
FIG. 9 is a side view of the nozzle arrangement when there are many welding points, and FIG. 20 is a side view of specific piping and wiring for detecting weld cracks. "l * W2 e w31 w4...Welding crack ■~
O...Interlayers 17-19...Pulp 23...High pressure vessel Figure 12 Figure 14 Figure 19 Furnace 1 convex

Claims (1)

[Claims] 141 A method for detecting weld cracks in a multilayer pressure vessel in which a large number of cylindrical bodies formed by bending thin plates and welding them in a longitudinal direction are laminated in a U-shape, the method comprising:
A detection hole reaching the surface of the innermost layer is drilled in a direction perpendicular to the axis of the pressure vessel, and the fluid is injected between a certain layer and the source pressure changes or the fluid is detected from adjacent layers. A method for detecting weld cracks in a multilayer pressure vessel, characterized by determining the presence or absence of cracks in a seam weld temporarily formed between layers.