RU2180948C1 - Method of manufacture of pressure cylinder - Google Patents

Abstract

FIELD: mechanical engineering. SUBSTANCE: proposed method includes making of hermetically sealed liner, forming of load-bearing envelope made of reinforced composite material and hardening of binder. When forming load-bearing envelope, ready-made preliminarily prepared woven skeleton is made which is fitted onto liner. Edges of skeleton are secured on liner flanges. Skeleton is impregnated with polymeric binder and pressure nuts are installed on liner flanges. EFFECT: simplified method of manufacturing of pressure cylinder, reduced labor input and cost of pressure cylinder. 1 dwg

Description

 The invention relates to methods for producing products using polymer composite materials, and in particular to methods for manufacturing pressure cylinders for storing liquids and gases used in various industries, for example, in the chemical, petrochemical, automotive.

 A known method of producing a metal-plastic cylinder (A.S. 2002160, 1993, MKI F 17 C 1/06), including the manufacture of a sealed liner consisting of a metal shell and elliptical or hemispherical bottoms with flanges and a fitting, and molding on the cylindrical part of the liner power shell. The power shell is formed using the method of winding with threads or bundles impregnated with a polymer binder. Next, curing the composite. The metal-plastic container obtained in this way is not an equal strength construction, since its cylindrical part is reinforced with reinforced composite material, while the bottoms have only a metal layer.

 This design of the cylinder is not equally strong, its "weak point" at high pressures will be the bottom. The method of forming by winding is complex, time-consuming and requires special equipment. A known method of manufacturing a pressure cylinder (I.F. Obraztsov, V.V. Vasiliev, V.A. Bunakov. "Optimal reinforcement of shells of revolution from composite materials", M., "Engineering", 1977, p. 99), which is closest to the claimed. The method is as follows. First, a cylindrical liner is made of plastic or metal. On the liner, as on a mandrel, wrap a tape formed by a system of threads or bundles, impregnated with a binder. The tape is fed to a rotating liner installed in the centers of the winding machine. Ribbon winding is carried out on a special software winding machine according to a special program with the formation of spiral and annular layers. After obtaining the necessary thickness and structure of the composite material covering the cylindrical part and the bottoms of the liner, the binder is polymerized. Thus, the power shell is formed. In the case of using a plastic liner, its rigidity will not be enough for winding. Therefore, the liner is additionally reinforced from the inside so that it does not lose its shape and size from the technological loads inherent in winding. To this end, during the winding and curing, the liner is filled with a hardening compound (for example, a sand-polymer mixture, sodium chloride, etc.), which is then removed.

 The disadvantages of the method are its great complexity and the cost of forming a power shell, as well as the limited application thereof (only for cylindrical cylinders with a circular cross section, a straight longitudinal axis, with hemispherical or semi-elliptical bottoms). Layered spiral ring winding - a long process. The limited width of the tape, the small peripheral speed of rotation of the liner, the low speed of impregnation of the tape with a binder, the significant dimensions of the liner and the thickness of the power shell lead to a significant duration of the molding process of the power shell. Winding requires a special complex and expensive programmed machine. The curing mode is long, significant energy costs, special temperature furnaces are required.

 The problem to which the invention is directed is to simplify the method of manufacturing a pressure cylinder, reduce its complexity, cost, and also expand the technological capabilities of the method by using a finished or prefabricated reinforcing woven frame as a power shell.

 The problem is solved due to the fact that in the known method of manufacturing a pressure cylinder, including the manufacture of an airtight liner, molding a power shell on it from reinforced composite material, curing the binder, a finished or prefabricated reinforcing woven frame is used as a power shell, which is put on the liner and fix its ends on the flanges, after which the frame is impregnated with a polymer binder.

The difference of the proposed method from the method of the prototype is the use as a power shell of a finished reinforcing wicker frame. This will allow:
- to exclude from the method of manufacturing the balloon labor-intensive winding process;
- abandon complex and expensive equipment for winding;
- exclude the operation of reinforcing the stiffness of the plastic liner;
- to make cylinders with various cross-sectional shapes (round, rectangular, square, etc.), with a straight and curved axis of the cylinder with an arbitrary shape of the bottoms;
- to provide high-performance molding of the frame on the liner;
- provide high-performance impregnation of the frame with a binder;
- apply a binder of "cold" curing that does not require thermal furnaces and electricity.

 The essence of the method is as follows. At the first stage, the inner part of the pressure cylinder, the liner, is made. It is a thin-walled sealed vessel with bottoms of arbitrary shape, with flanges and a nozzle for filling. The material of such a liner can be a polymer or light metal (aluminum, titanium). The manufacture of the liner is carried out by known technologies. In the plastic version, it is made by blow molding or rotational molding of high pressure polyethylene. The metal liner can be obtained by stamping, extracting the cylindrical part and bottoms and subsequent welding.

 The next step is the formation of the power shell. As a power sheath, a ready-made reinforcing braided frame is used or it is made in a known manner (RF patent 2135659, August 1998). The frame has unique properties - flexibility and deformability, it can be easily stretched in axial or circumferential directions. In this case, the cellular structure is transformed, and the integrity of the frame is preserved. For each type and size of cylinder, the corresponding type and size of the frame is required. This is achieved by experimental selection of technological parameters of the weaving of the frame. The frame-blank is put on the liner. In this case, the frame is initially stretched in a circumferential direction to a size 10 ... 30 mm larger than the liner diameter, and freely put on, then axial stretching is done to ensure a snug fit. The edges of the frame are located in the areas of the bottoms on the flanges and may have some excess around the perimeter, therefore, if necessary, they are compacted, pressing against the bottoms. Fasten the edges of the frame by winding threads or ribbons on them. It should be noted that the frame does not exert pressure on the liner and, in the case of using a plastic liner, its own rigidity is enough.

Next, the framework is impregnated with a low viscosity polymer binder. You can use one of the high-performance methods of impregnation:
- complete immersion of the product in the bath with a binder;
- partial immersion of the product in the bath with a binder and subsequent slow rotation;
- application of a binder by spraying.

 The quality of the impregnation depends on the density of the structure of the frame, on the viscosity and type of binder, on additional conditions (evacuation, vibration, ultrasound, etc.). Next, clamping nuts are installed on the flanges, which tightly press and fasten the edges of the frame. Then follows the curing step. When using a “cold cure” binder, room temperature is sufficient; for a “hot cure” binder, the temperature regime in a thermal furnace is required. At the final stage of the technology, quality control of the cylinder is carried out with a mandatory hydrostatic pressure test.

 The drawing shows a pressure cylinder. The cylinder contains a liner 1, consisting of a cylindrical part 3 and the bottoms 4 of an elliptical or hemispherical shape. The liner has flanges 6 and a nozzle 7 for filling. On top of the liner is a power shell 2 of reinforced composite material. The power shell is a braided frame 8, impregnated with a binder and cured. On the flanges 6 are installed clamping nuts 5, fixing the edges of the frame.

 An example of a specific implementation of the method of manufacturing an automobile pressure cylinder for liquefied natural gas in the following sizes: diameter 200 mm; length 800 mm; thickness of the power shell 3 mm; ultimate pressure 4.8 MPa.

 A ready-made plastic container was used as a liner.

Using the well-known method for producing a tubular wicker product (patent 2135659), a frame blank was prepared from integrated twisted glass fiber of the VMPS brand. The weaving time of the blank frame was about 10 minutes. After that, the frame blank was put on the liner, the ends were fixed on the flanges by winding with glass fiber, and the frame was impregnated with an EDX epoxy binder. The binder was applied manually with a brush. Curing was carried out in a thermal furnace at 120 ^o C. The total time of forming the power shell according to the proposed method was about 20 minutes, which is 3 times less compared to the method of the prototype (the time of forming the shell according to the prototype was about 60 minutes). Approximately in the same ratio are the complexity and cost of the compared methods.

 Thus, a significant simplification of the method of manufacturing a pressure cylinder, reducing its complexity, cost, and also expanding its technological capabilities are achieved. The method allows to produce a wide range of pressure cylinders, namely with different section shapes (round, rectangular, square, etc.), with a straight and curved axis of the cylinder, an arbitrary shape of the bottoms. This is especially true for mass production, for example, for the production of cylinders for automobiles operating on liquefied natural gas. The method can also be used for the manufacture of other products, for example, vessels, bends, pipes.

Claims (1)

 A method of manufacturing a pressure cylinder, including obtaining a sealed liner, forming a power shell on it from reinforced composite material, curing the binder, characterized in that when forming the power shell using a finished or pre-made reinforcing woven frame, which is put on the liner, after which the edges of the frame are fixed on the flanges of the liner, impregnate the frame with a polymer binder and install clamping nuts on the flanges of the liner.