DE2515856A1 - ELECTRICALLY INSULATING PIPE CONNECTION - Google Patents

Description

Patent Attorneys Frankfurt / M., March 17, 1975

DIPL.-INQ. H. HISSLINQ _{Ώ / τ} . _{ΛΟ ΑΛΑ}

D.PL .-. NQ. R. SCHLEE Boe / Prs 12.414 $ 3 QlESSEN, Bitmaroitttrale 43 9 ζ 1 ζ fi R R

D R. «ING. J. BOECKER ^ OIOOOO

β PRANKFURT 1, fteftenaupl. 2

Allmänna Svenska Elektriska Aktiebolaget Väster as / Sweden

Electrically insulating pipe connection

The present invention relates to an electrically insulating pipe connection according to the preamble of claim 1. Such "Connections occur mainly in large water-cooled generators and are used there in such places where you want to prevent the hydraulic connection between two machine parts at the same time being an electrical connection between represents these parts, because the cooling water pipes are always made of metal.

It is known to connect two pipe ends by means of a plastic hose to connect, which has a hose clamp at each end. Such a pipe connection is only for low fluid pressure, for example less than 1 bar, is suitable. From the American patent application 757 998 it is known on the outside of the hose to use a sleeve. Through this sleeve however, the compressive strength of the pipe joint is not essential elevated.

The present invention has for its object to develop a pipe connection of the type mentioned, which has a very high compressive strength.

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To solve this problem, a pipe connection is after The preamble of claim 1 proposed according to the invention has the features mentioned in the characterizing part of claim 1.

Advantageous refinements and further developments of the invention are mentioned in the subclaims.

The pipe connection according to the invention withstands liquid pressures of several hundred bar. Wherever a very high Security against leakage is required, such as with water-cooled generators, is the application of the Pipe connection according to the invention is also recommended for liquid pressures above 20 bar. With water-cooled generators a cooling water pressure of approx. 100 bar is normally required applied, and the centrifugal stress can be 5000 times as great as the gravitational acceleration.

Based on the embodiment shown in the figures the invention is to be explained in more detail. Show it:

Fig. 1 shows an embodiment according to the invention, the line 0-0 being the center line of the pipe connection is, the left part of Fig. 1 shows a view perpendicular to the line 0-0 and the right part shows a partial axial section j

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Pig. 2 a detail of the pig. 1 in a larger representation.

In Pig. 1, 1 and 2 designate two pipes made of stainless steel which are connected to one another by means of a plastic pipe 3. Each steel pipe 1 and 2 has an enlarged end section, the total wall thickness t .. or t ~ at least three times as large as the minimum wall thickness t of the pipe. Each widened end section contains a hollow cylindrical gap 4 and 5, each of which is delimited by two cylindrical walls, the minimum thickness of which is significantly greater than the Roh.rdj.cke t- ,. The hollow cylindrical gaps are completely filled, since they each receive one end of the plastic tube 3. The cylindrical boundary walls of the column are provided with several annular sealing grooves 6 in each Y / and. These grooves have a width mm of less than 2 and are filled at least 75 7 <> with plastic material, which at the same time part of the plastic tube. 3 The groove width is denoted by b and the groove depth by d.

In a pipe connection according to the invention, the ability depends to withstand a high liquid pressure without leakage depends to a large extent on whether the hollow cylindrical gaps 4 and 5 are tight. In particular, there must be no leakage in the bottom section of the column. If this is the case, the The pipe connection is only able to withstand fluid pressure through the sealing effect in the layer between the inside of the

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Plastic pipe 3 and the radially inner boundary surface the above-mentioned hollow cylindrical column is determined. If, on the other hand, the annular gap is very tight, it also works the radially outer boundary surface of the gap as a sealing surface, whereby in cooperation with the outside of the Plastic tube an extremely strong self-seal is achieved, which is triggered when liquid between the inside of the plastic pipe and the adjacent to this Cylindrical surface of the metal pipe penetrates. The penetrating liquid has the same high pressure as the rest of the liquid, so that the plastic pipe 3 with a pressure that is hardly from Fluid pressure in the ears deviates on the outer boundary surfaces the hollow cylindrical column acts. It is assumed that the plastic pipe 3 consists of a somewhat flexible Material consists, for example Teflon or polypropene.

In certain cases it may be sufficient to use a pipe connection according to the invention only by means of the two metal pipes 1 and 2 and the produce intermediate plastic tube 3. Should be a If further reinforcement is required, several layers of glass tape impregnated with molded insulating material can be placed around the joint wrap or otherwise encapsulate the pipe joint in a reinforced plastic body. In Fig. 1 is such a Plastic body designated by 7. In order to be able to absorb axial forces at very high fluid pressure, according to one Another embodiment of the invention surround the pipe connection with a casing 8 made of stainless steel. The shell is on

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its one end is provided with a conical stop surface 9 and at its other end with thread 10 and with the metal tube 2 screwed.

In a method for producing a pipe connection according to the invention, each of the two metal pipes 1 and 2 made of stainless steel is provided with a flange 11, 12, the distance from the pipe end of which is at least 1/4 of the inner diameter of the pipe 1 and 2, respectively. A sealing surface 13 for an end surface of the plastic pipe 3 and a sealing surface 14 for an end surface of the sleeve 15 made of stainless steel are provided on each surface. Each sleeve 15 is welded to a corresponding sealing surface 14 with an annular and completely tight weld seam, preferably by electron beam welding. Thereafter, each end of the plastic tube 3 is pushed between a sleeve 15 and one of the metal pipes 1 and 2, after which the sleeve 15 is plastically deformed by compression with the aid of strong jaws in such a way that a radially inward pressure is created on the outside of the sleeve. This pressure is transmitted through the plastic pipe to the inside ^ underlying metal tube and is so large that a significant elastic deformation of at least 30 f °, preferably remains present over 50 fo the maximum possible, at one end 16 of the metal tube 1 or x 2, after the jaws and thus the external pressure have been removed.

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A metal tube and the sleeve 15 coaxial with it are then always in the pretensioned state, even if there is a reduction the effect of the Kunstsfoffröhres 3 take place as a spacer element should, for example, if the annular sealing grooves in the adjacent metal surfaces become more pressed in over time Take up the plastic material of the plastic tube 3 should. In order to avoid such a relaxing pressing in, the above-mentioned compression should not be sudden instead, the external pressure acting on the sleeve 15 should be at least ten, preferably more than a hundred Seconds near its highest fourth. You can then use the Plastic pipe directed annular sealing grooves achieve a degree of groove filling that is significantly greater than with a pressing time of, for example, only five seconds.

Of course, even with a very short pressing time, an almost 100% groove filling can be obtained if the groove width large enough is chosen. However, you want large groove widths Avoid, as a significantly better seal is obtained with a large number of narrow grooves than with a small one Number of wide grooves. With the plastic and rubber material, which is mostly used in this context, should the annular sealing grooves no wider than at most Be 0.8 mm.

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A pipe connection according to the invention can also be obtained by a method which differs from the above. For example you can put the plastic tube in the hollow cylindrical Glue the gap with the help of hardenable plastic. You can also use the hollow cylindrical gap - especially with the one mentioned Use of hardenable plastic - manufacture by turning only.

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Claims (5)

M.) Electrically insulating pipe connection with two metal pipes arranged axially one behind the other and one in between Tube made of plastic or similar material, each metal tube being expanded with the plastic tube connected end portion, which is provided with a hollow cylindrical, pressure-tight gap, the axial dimension of which is greater than 1/3 of the inner diameter of the metal pipe, characterized in that the walls delimiting the gap (4) outside and inside have a thickness which is substantially everywhere is greater than the wall thickness of one of the metal pipes (1, 2) and that the plastic pipe (3) with its end in the gap (4, 5) is arranged. 2. Pipe connection according to claim 1, characterized in that both an inner and an outer cylindrical boundary surface of the hollow cylindrical gap (4, 5) is provided with a plurality of annular grooves (6), and that each groove, at least 75 fo, with material , is filled, which is also part of the plastic tube (3) . 3. Pipe connection according to claim 1 or 2, characterized in that the radially outside of the plastic tube (3) lying part of the end portion of a metal tube (1, 2) consists of a metallic hollow cylinder (15) which, preferably by means of electron beam welding, with an annular , completely sealing weld seam is welded to the metal pipe (1, 2). 509846/0333 ~ ⁹ " 4. Pipe connection according to one of claims 1 ~ 3> characterized in that the plastic tube (3) and the expanded End sections of the metal pipes are enclosed by a common capsule (7) made of reinforced molded insulating material. 5. Pipe connection according to claim 4, characterized in that the capsule is surrounded by a cylindrical metal shell (8) is, which at one end with an axially acting stop surface (9) for the capsule and at its other end with Internal threads (10) are provided, by means of which the casing is mechanically connected to one of the expanded metal pipe sections is. 509846/0333 Blank page