EP0343098A1 - Pressure vessel - Google Patents

Abstract

The invention relates to a method of manufacturing a pressure vessel for the storage and drawing-off of gases or gas mixtures, particularly of special gases or gas mixtures of high purity, consisting of a thin-walled inner container (7) of stainless steel and a pressure-resistant outer sleeve (1, 2) enclosing the latter, the prefabricated inner container first being pushed into the sleeve and then being brought to bear on the inner wall of the sleeve by plastic widening. In order to be able to manufacture such a pressure vessel by simple production technology and at reasonable cost, it is proposed according to the invention that the sleeve be a multi-part sleeve and that the parts forming the various regions of the sleeve be prefabricated and screwed together after the insertion of the inner container. <IMAGE>

Description

The invention relates to a method for producing a compressed gas bottle for the storage and removal of gases and gas mixtures, according to the preamble of the main claim, in particular for special gases or gas mixtures of high purity, and to a compressed gas bottle produced by the method.

Gases of high purity are required for production in the electronics industry, among others. When such gases are stored and transported in conventional steel bottles, there is contamination and the consistency of the mixture is impaired, which impair the possibility of using the gases. These conditions apply in particular to corrosive, toxic and flammable gases, which are required, for example, in semiconductor technology or in test technology.

It is known that the surface quality and the cleanliness of the inner surface of the pressure vessel have a great influence on the purity and the mixture stability of the gases. In addition, the material used is of great influence. On the other hand, for economic reasons of transport and storage, it is required that the gases can be kept partly under high pressure. This also requires a high-strength pressure vessel material. The known steel bottle made of unalloyed or low-alloy steel fulfills the strength requirements very well; according to the state of the art it is nevertheless not with regard to the purity and state of the art but nevertheless not with regard to the purity and Corrosion requirement considered suitable.

Stainless steel is highly chemically resistant to all gases and gas mixtures in question. It also has the property that it can be polished to a high gloss (electrochemical polishing), as a result of which the active surface is leveled and considerably reduced compared to the unpolished state. This greatly reduces the absorption effect of the gases on the inner wall of the container and the release of particles. In addition, after electropolishing, the inner surface is free of residual mechanical stresses that have arisen from the manufacturing process, which reduces the tendency of the container material to sorb.

It has already been recognized that the smaller the gas pollution, the lower the is the surface roughness of the pressure vessel inner wall. To solve this problem, a multi-part bottle made of stainless steel has recently become known as a low-pressure and high-pressure version (see Handelsblatt No. 77 from April 21, 1988, reports from the Hanover Fair in 1988). A disadvantage of this proposed solution is the poor efficiency, d. H. the ratio of container weight to storage volume due to the low strength properties of the material used compared to a hardenable carbon steel and secondly the costs related to the kilogram container weight due to the high proportion of expensive alloy components such as chromium, nickel and molybdenum.

Several other proposals deal with the concept of providing a pressure-resistant outer body that can be produced from an inexpensive material with a corrosion-resistant layer on the inside. For this purpose, it has become known from DE 37 23 124, a thin-walled inner container prefabricated from stainless steel into a container with only one bottom Push the pressure-bearing sleeve, the neck-side jacket area of which is still undeformed, and then form the neck area of the sleeve. However, this molding is very difficult to master in terms of production technology and, in addition, the entire pressure vessel has to be tempered after the neck has been molded in order to achieve the required strength. So that the inner container cannot scale during remuneration, it must be closed accordingly, which is not easy to achieve under the given conditions.

In another proposal (DE-PS 737 187), a shorter inner container provided with a corrugated or groove-shaped jacket part is inserted into the outer container having an open bottom and, after the bottom has been closed, the inner container is pneumatically or hydraulically stretched and attached to the inner wall of the Pressed outer container. The problem with this proposal is similar to that of the aforementioned document. The subsequent shaping of the bottom is not very easy in terms of production technology and, in addition, to achieve the required strength, the entire container must be tempered after the bottom has been formed. An additional difficulty arises from the fact that the waves or grooves to be applied in the jacket part of the inner container have to be considerable in order to achieve the required shortening. This reshaping in connection with the subsequent stretching can lead to pre-damage to the material in view of the high requirements with regard to corrosion resistance under alternating loads.

The object of the invention is to provide an improved method for producing a pressurized gas bottle for storing and withdrawing gases and gas mixtures, in particular special gases and gas mixtures of high purity for the low and high pressure range, and to provide a pressurized gas bottle manufactured thereafter with which the previously Disadvantages described avoided and the manufacturing costs can be kept low.

This object is achieved by the features of the method in claim 1. Further advantageous features are covered in the subclaims.

The main idea of the proposed solution is the idea of forming the pressure-bearing sleeve in several parts and screwing the parts representing different areas of the sleeve together after inserting the inner container and then, in a known manner, completely and without resilience to the inner wall of the sleeve by means of plastic deformation bring. It is already known (US Pat. No. 3,140,006) to provide prefabricated parts of the pressure-bearing sleeve with a single-layer or two-layer corrosion-resistant material and then to weld the parts together. However, this welded joint has the disadvantage that the heat-affected zone forms a weak point in the pressure-bearing body and, in addition, part of the outer surface of the inner container is scaled by the welding process.

For the proposed screwing of the prefabricated parts according to the invention, threaded sections are made at the opposite ends, which are designed as a pin and a sleeve element and can be screwed together. The thread can be designed simply because it only has to transmit the forces resulting from the internal pressure, since the inner container then forms the gas-tight interior. The advantage of screwing compared to welding can be seen in the fact that the tempering of the prefabricated parts can be completed and the inserted inner container is not thermally stressed in any way.

In the proposal to use an inner container, the choice of material for the pressure-bearing sleeve is of secondary importance, since such a combination can be implemented both with a sleeve made from plastic material and from a metallic material. The sleeve only has to be designed in such a way that it can absorb the tensions and forces resulting from the internal pressure with the appropriate safety supplements. In order to keep the wall thickness and thus the weight of the sleeve low, it is further proposed that the materials used by embedding fibers in the case of plastics, eg. B. glass or carbon fiber or by externally applied to the metallic sleeve fiber windings.

When using a previously manufactured inner container, a division of the sleeve is essential, since the inner container cannot be pressed into a finished molded pressure container with a tapering neck area. The problem of a subsequent shaping of the bottom or neck area after inserting the inner container has already been pointed out in the introduction to the description.

Treatment of the inner surface of the parts of the sleeve before connection is only necessary depending on the choice of material and the type of prefabrication. In the case of already smooth inner surfaces, as in the case of plastics, such treatment can be dispensed with in most cases. Pretreatment is not essential in the case of heat-treated parts that have a corresponding scale layer. Furthermore, a treatment is required if the inner contour dimensions of the sleeve have to be adapted to the outer dimensions of the inner container due to production. The treatment of the parts can be mechanical, e.g. B. by Blasting, sleeping or polishing or in a known manner by chemical methods such as pickling or electropolishing or in a combination of both methods.

The division of the sleeve can be done in a variety of ways and is guided more by practical considerations. The division plane for a two-part sleeve can be in the bottom area or in the neck area or in the middle of the jacket area and in the case of a three-piece sleeve in the bottom and neck area.

The inner container abuts the inner wall of the pressure-bearing sleeve in an advantageous manner during the pressing-off required for a component test. The thin-walled inner container inserted with play is plastically deformed and lies completely against the inner wall without springing back. In the connection area, the protruding neck of the inner container is cold flanged and the collar formed in this way is pressed firmly onto the end face of the neck of the sleeve. For the design of the connection area, a not yet published state of the art has become known, which is characterized by a large neck opening and an adapter designed for the special requirements. If necessary, the inner surface of the inner container can be electropolished separately as a prefabricated part or alternatively after being connected to the pressure-bearing parts. Since the inner surface is already fairly smooth by itself, a short-term treatment will suffice in most cases, which in turn has a favorable effect on the manufacturing costs.

• Figur 1 eine zweiteilige Hülse mit einem eingeschobenen Innenbehälter, deren vorgefertigte Teile in bekannter Weise durch Schweißen miteinander verbunden werden,
• Figur 2 eine verschraubbare zweiteilige Hülse, deren Trennebene im Halsbereich liegt,
• Figur 3 eine verschraubbare zweiteilige Hülse mit einem vom Boden nur bis zur Trennebene sich erstreckenden Innenbehälter

The method according to the invention is explained in more detail in the drawing. Show it:

• FIG. 1 shows a two-part sleeve with an inserted inner container, the prefabricated parts of which are connected to one another in a known manner by welding,
• FIG. 2 shows a screwable two-part sleeve, the parting plane of which lies in the neck area,
• 3 shows a screwable two-part sleeve with an inner container which only extends from the bottom to the parting plane

1 shows the essential steps of the method according to the invention with the exception of the already known welded connection. Partial image a shows two prefabricated pressure-bearing parts, one of which is part 1 which represents the neck region and the other which represents part 2 which represents the jacket region, including the base region. Depending on the material, the respective inner surface of the two parts 1, 2 is treated mechanically or chemically or by a combined process in the course of the prefabrication. It may also be necessary to machine the inner contour of the two parts 1, 2 with regard to dimensional accuracy. The respective end face 5, 6 of the two parts 1, 2 is machined for the subsequent already known welded joint. Sub-picture b shows the prefabricated thin-walled inner container 7, which was produced in this example in a seamless version. It could just as well be a container welded together from several parts. In partial image c, the inner container 7 has been inserted into the lower pressure-bearing part 2 and the part 1 representing the neck area has been placed on it. The neck 8 of the inner container 7 extends over the end face 9 of the upper pressure-bearing part 1. Between the outer surface of the inner container 7 and the inner wall 3, 4 of the pressure-bearing parts 1, 2, there is play 10 at this stage (shown here in a greatly exaggerated manner) . After assembly, the two pressure-bearing parts 1, 2 are a weld seam connected positively and positively.

Sub-picture d shows the finished compressed gas bottle without connection parts, such as valve and protective cap. The last area of the neck 8 of the inner container 7 has been flanged onto the end face 9 of the upper pressure-bearing part 1 by means of cold forming. In the subsequent pressing in the course of the component test, the inner container 7 is plastically widened and the inner container 7 comes into complete contact with the inner wall 3, 4 of the pressure-bearing parts 1, 2 and no longer has any play 10.

Figure 2 shows like Figure 1, a sleeve made of two prefabricated parts 19, 20. In this exemplary embodiment, both parts 19, 20 each have a threaded section 21, 22 at the mutually facing ends, which can be screwed together. As an example, the threaded section 21, 22 is designed as a cylindrical thread. It could just as well be a tapered thread. One threaded section 21 is designed as a pin element and the other 22 is designed as a socket element, the threaded section in the part 19 representing the neck area, in reverse, also being able to be designed as a pin element. After inserting the inner container 7 according to FIG. 1b into the lower pressure-bearing part 20, the upper pressure-bearing part 19 is firmly screwed on. Comparable as in FIG. 1c, a play 10 remains between the outer surface of the inner container 7 and the inner walls of the two pressure-bearing parts 19, 20. The inner container 7 is in contact with the inner walls of the two pressure-bearing parts 19, 20 by hydraulic pressing in the course of the component test as in Fig. 1 d.

FIG. 3 shows a further exemplary embodiment, which is the same in terms of the separation point as that shown in FIG. 1, but in the form of Inner container is different. In the prefabrication, the inner container 24 is designed here as a cylindrical body which has a bottom and has no neck. After the inner container 24 has been inserted into the representative part 25, which pre-fabricates the shell including the base region, the inner container 24, which extends over the end face 26 of the part 25, is cold flanged on this end face. The part 27 representing the neck area is made of solid stainless steel and is screwed to the other pressure-bearing part 25. The variant shown in Fig. 6 should be of advantage if the manufacture of the neck portion of the inner container 24, especially when the wall is very thin, should pose difficulties, so that it is generally less expensive to buy the higher material costs of the part 27 representing the neck to take.

Claims (14)

1.Procedure for the production of a compressed gas bottle for the storage and removal of gases or gas mixtures, in particular special gases or gas mixtures of high purity, consisting of a thin-walled inner container made of stainless steel and an outer pressure-resistant sleeve surrounding it, the prefabricated inner container being first inserted into the sleeve and is then brought into contact with the inner wall of the sleeve by plastic widening,
characterized,
that the sleeve is in several parts and the parts representing different areas of the sleeve are prefabricated and screwed together after the inner container has been inserted. 2. The method according to claim 1,
characterized,
that the parts are made of a fiber-reinforced plastic material. 3. The method according to claim 1,
characterized,
that the parts are made of a metallic material. 4. The method according to claim 3,
characterized,
that the parts are subjected to heat treatment in the course of prefabrication. 5. The method according to claims 3 or 4,
characterized,
that the inner surface of the parts is mechanically treated before joining. 6. The method according to claims 3 or 4,
characterized,
that the inner surface of the parts is chemically treated before joining. 7. The method according to claims 5 and 6,
characterized,
that the inner surface of the parts is combined mechanically and chemically treated before joining. 8. The method according to claims 3 to 7,
characterized,
that the parts are wrapped outside with a fiber for reinforcement for reinforcement. 9. The method according to claim 1,
characterized,
that the inner container is plastically expanded by hydraulic pressing carried out in the course of the component test. 10. Pressurized gas bottle for the storage and removal of gases or gas mixtures, in particular special gases or gas mixtures of high purity, produced according to claims 1 to 9, consisting of a thin-walled inner container made of stainless steel and a surrounding outer pressure-resistant sleeve and with one arranged in the neck area for Inclusion of a valve and a suitable protective cap,
characterized,
that the sleeve has at least two prefabricated parts which are screwed together after the inner container (7, 24) has been pushed in, the inner container (7, 24) being fully connected to the inner wall (3, 4, 28) after the connection and the hydraulic pressing of the pressure-bearing parts. 11. compressed gas cylinder according to claim 10,
characterized,
that the parts (19, 20) have a threaded section (21, 22) at the facing end. 12. Pressurized gas bottle according to claim 11,
characterized,
that the threaded sections (21, 22) are designed as a pin (21) and once as a sleeve element (22) and can be screwed together. 13. compressed gas cylinder according to claim 10,
characterized,
that the parts made of a metallic material have a fiber winding on the outside after connecting. 14. compressed gas cylinder according to claim 10,
characterized,
that the inner container (24) covers the inner surface (28) of the part including the bottom region (25) and a region of the open end of the inner container (24) on the end face (26) of this part (25) is flanged and that Part (27) representing the neck area is made of solid stainless steel.

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