JPH04136589A - Structure of double tube - Google Patents

Abstract

PURPOSE:To smooth the inner surface of a tube by providing small outer diameter extension section in the end section of an outer tube, turning over this at the end section of the inner tube, and forming a sealed bead retainer at the joining section out of the end projected and a socket. CONSTITUTION:A double tube consists of an inner tube 2 of PFA thin wall and an outer tube of polybutene(PB) whose a coefficient of thermal expansion is equal to that of PFA, and the end section of the outer tube 1 is provided with a small diameter thin wall extension section 3, or a thin wall metallic ring 8, whose inner diameter is the same as that of the extension section 3, is plugged, and the PFA inner tube 2 is turned over and coated and fixed at this section. When the outer tube 1 and a socket 5 are joined by welding in heating process said section is fixed to a fixed position without being restored. In addition, since all of the beads (a) and (b) are completely contained in a sealed bead retaining chamber 6 appearing at the outer periphery of the head section of a double tube in joining process, the surface of flow passage is smoothed. As a result, the drift and break in the inner tube due to the heat cycle will not occur, and fluid retaining places on joining sections are eliminated.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to piping used primarily for transporting fluids in chemical industries, semiconductor manufacturing factories, and the like.

[Conventional technology and its problems]

The present invention will be mainly described with reference to ultrapure water piping in the semiconductor manufacturing industry, where NiM is the most important feature. The degree of integration in semiconductors is 4 megabits (same as 4M or higher)
, 16M, and 64M, paper containing metal ions and organic carbon (TOC) eluted from the piping materials into the ultrapure water that is frequently used during these manufacturing processes greatly influences the yield of the product. These a contents are currently PPM (parts per million -), prB
It seems to be on the order of (1-100,000,000-). Furthermore, fluid stagnation H1m (dcad-spot) formed at the connections between pipes and various equipment or between pipes, e.g. Fig. 6b 1. : Eliminates the bead that occurs at the joint on the inner surface of the passage during butt welding as shown, and prevents the growth of viable bacteria.
In addition, the inner surface of the tube must be smooth to reduce fluid resistance. From this point of view, the piping materials are stainless steel, vinyl chloride (CPVC), vinylidene fluoride (PVDP).
, a single plastic tube made of 1f whethyl ether ketone (PEEK) is used, but there is a problem with the elution of TOC1 metal ions in the production of ultra-high integrated circuits (LILSI) of 4M or more, and the current amount is limited. is also chemically stable and T
Tetrafluoride resin, a plastic that is ideal for semiconductor manufacturing, has almost no elution of OC1 metal ions.

[l Ethylene, (TFE), TFE and par'7 Cy (17
JL/kirhinyl ether copolymer (PFA) has low rigidity and is extremely expensive when used alone, so currently -
・It is used as a high-temperature, high-pressure, corrosion-resistant pipe in the chemical industry, where there are no substitutes, because it is a metal pipe lined and is used at a high price. However, although there is still a big demand in the semiconductor field, the current construction method can only connect lining pipes with flanges, as shown in 4-4 above, so there is a dead-spot in this area, and the coefficient of thermal expansion is lower than that of metal. Due to the expansion and contraction caused by the repeated heat cycles of cold and heat during heat sterilization, which is often performed, wrinkles occur in the lining layer, and cracks and destruction occur in areas where stress is concentrated. It has not yet been used. [Means for solving the problem] As mentioned above, in conventional double pipes (lined pipes or lined pipes), only Franz type joints are used to connect the pipes, and welding is the most suitable method for ultrapure water piping. The construction method was not practicable. In the present invention, the inner tube is made of a thin PFA tube, and the outer tube is made of 1) I
” It is made of polybutene (PR), which has the same island expansion coefficient as A, and a small-diameter, thin-walled extension is inserted into the end of the outer tube with a ring made of the same material or metal to form a tank, and the PFA inner tube is attached to this part. In addition, a notch is provided on the outer diameter of the end of the outer tube so that the outer tube and the socket are fixed at the same position without being deformed during the heating process during melt joining of the outer tube and the socket. A double pipe that can be welded and joined has a bead storage chamber that prevents beads generated during joining from entering the butting surface with other pipes and being exposed to the wetted parts, and the flow path surface is smooth. It was realized.

【Example】

The present invention will be explained based on the drawings. FIG. 1 is a cross-sectional view when the present invention is implemented. First, in Fig. 2, which is an enlarged view of the main parts of the present invention, ■ is a thick-walled outer tube made of PR, and 2 is a PFA tube. XI thin wall inner tube,
2-■ is the turning part of 2, and 3 is a thin ring made of stainless steel (preferably a corrosion-resistant rigid material with no Ri specified). As shown in drawing 1, a thin-walled extension part 1 is formed at the end of 1, and an enlarged diameter part 1-.2 is bored into which the inner diameter 3 is fitted. 2 is turned over in a shape that covers 3 with this extension, and fixes 2. The space indicated by the dotted line is a space 6 that should become a bead reservoir, which will be described later. Figure 2 is a modification of Figure 2, which uses the fixing method of 2.
1-■J, without providing ① and 3: 2 is directly coated by rolling, and 2 is fixed with the ring 3-■. This is used when [ is a thick-walled pipe, and in this case it is extremely difficult to turn 2 into this shape. This goal can be easily achieved by making multiple cuts in a single shape from the top of the head onwards. However, this method is also effective when 2 is thick. Let me explain again by going back to Figure 1. As shown in the second or third figure, one side (temporarily the left side) of the two pieces has been processed.
Insert it into B socket 4 using a normal welding machine and weld it. The bead that always occurs at this time is a on the outer diameter side of the heavy weight and b on the inner diameter side.
becomes. In normal piping, this will be a and b as shown in Figures 4 and 5, but it does not matter how many. However, in the case of the double pipe of the present invention used for ultrapure water, if even a small amount is exposed to the liquid passage, the T
OC etc. will be eluted. Therefore, in the present invention, the beads generated in the bead pool shown in 6 of FIG. Next, the outer diameter of PFA is almost equal to the inner diameter of 4, and the inner diameter is 2.
A sealing sleeve 5 having a convex cross section and having an outer diameter equal to the outer diameter of is inserted into the pipe from the right side. The convex portion on the inner diameter side is formed to fit into the radius of the top of the head of 2-2, and sealing is performed at this portion. Furthermore, the bead storage chamber 6 appears between the outer diameter end of 5 and the end face of 1, and the generated beads are stored here.
ing. Next, insert the other double pipe from the right side under strong pressure in the same manner as above, and complete the welding and joining process.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view when the present invention is implemented. Figures 2 and 3 are partially enlarged views of the end of the double pipe. Figures 4 and 5 are partial cross-sectional views of the conventional socket welding method. The figure is a partial cross-sectional view of a conventional butt welding method.

【Effect of the invention】

As described above, the present invention is directed to PF8, 'I', which will be essential in future high-tech fields such as electronics and biotechnology.
In the line vibrator with F E as the inner pipe, conventional non-O
With its simple structure, the inner tube does not shift or break due to thermal cycles, and there are no fluid stagnation points on the joint surface, making it a low-cost product that allows conventional welding methods to be applied as is. This has the effect of being able to provide plastic double pipes. However, the present invention is not limited to the above-mentioned constituent materials, but can exhibit performance in fields that are suitable for each by combining various materials. 1... Outer tube 2... Inner tube 3... Ring 4... Socket 5... Seal ring 6... Bead reservoir a, Outer bead b, Inner bead February 19th

Claims (1)

[Claims] In a double pipe consisting of a thick-walled outer pipe and a thin-walled inner pipe, both of which are made of plastic, an extension with a small outer diameter is provided at the end of the outer pipe, or an extension part with a small outer diameter is provided at the end of the inner wall of the outer pipe. A thin-walled ring with an inner diameter equal to the inner diameter of the outer tube is fitted so that the head extends beyond the end surface of the outer tube, and these extensions are either covered with the end of the inner tube or wrapped around the outer periphery of this covering. Insert the ring to fix the inner tube inside the outer tube, and also insert a notch (
A double-pipe structure for welded joints that features a bead reservoir.