DE3312073A1 - Pressure build-up mandrel for the pressure-tight fixing of a tube - Google Patents

Abstract

In a pressure build-up mandrel (5) for the pressure-tight fixing of a tube (2) in a tube plate (1), with two clamping tapers (11, 12) arranged at an axial distance from one another, adjustable in the axial direction relative to one another and bounding an expansion zone (10), with a spacer sleeve (13) arranged between the clamping tapers (11, 12) in the expansion zone (10), and with a centrally beginning and radially ending pressure-medium feed line (14) emerging in the expansion zone (13), in which the oblique surfaces of the clamping tapers (11, 12) face the spacer sleeve (13) and, with the two end faces of the spacer sleeve (13), form two encircling seal-accommodating grooves (16), and in which an encircling seal (17) is provided in each of the seal-accommodating grooves (16), it being possible to expand the seals (17) radially by adjusting the clamping tapers (11, 12), the occurrence of leakage losses even while the hydraulic pressures are still low is almost completely avoided and the wear of the seals (17) is nevertheless kept low if each seal (17) comprises two essentially annular sealing elements (18, 19) arranged axially in series and if the two sealing elements (18, 19) are composed of materials of different (Shore) hardness. <IMAGE>

Description

"Pressure build-up mandrel for pressure-tight fastening of a pipe"

The invention relates to a high pressure seal for a pressure build-up mandrel for pressure-tight fastening of a tube in a tube sheet or the like, with two axially at a distance from one another, adjustable in relation to one another in the axial direction, clamping cones limiting an expansion area, one between the clamping cones in the expansion area arranged spacer sleeve and a preferably centrally starting and preferably radially tapering pressure medium supply opening into the expansion area, the Inclined surfaces of the clamping cones of the spacer sleeve are facing and with the two The end faces of the spacer sleeve form two circumferential seal receiving grooves, with A circumferential rubber-elastic seal is provided in each of the seal receiving grooves is and whereby the seals can be expanded radially by adjusting the clamping cones are.

The pressure-tight fastening of pipes in pipe sheets or the like. B.

the heat exchanger tubes in the tube sheets of heat exchangers an enormous economic importance. for several decades is as Process for this "mechanical rolling in" has been used, but this is very expensive and does not lead to results that can be calculated with sufficient accuracy (cf. M. Podhorsky and H. Krips "Hydraulic expansion of pipes" in VGB KRAFTWERKSTECHNIK, booklet 1/1979, pages 81 to 87). Compared to "mechanical rolling" is a "hydraulic" Expand "associated with a multitude of advantages (cf. M. Podhorsky and H. Krips "Hydraulic expansion of pipes", op. Cit.). A particular problem with the the practical implementation of "hydraulic expansion" consists in sealing of the cavity between the pipe end of the pipe to be fastened and the pressure build-up mandrel. To this extent, various devices, that is to say the pressure build-up mandrel, are relevant Known solutions.

The well-known pressure build-up mandrel with the high-pressure seal, from which the Invention proceeds (cf. DE-OS 19 39 105), is used for "hydraulic expansion" initially with play in one pipe end of a pipe to be fastened Pipe brought in. Only after the pressure build-up mandrel has been inserted into the end of the pipe to be fastened pipe is the cavity between the pipe end of the pipe to be fastened Sealed pipe and the pressure build-up mandrel. The seals are after Insertion of the pressure build-up mandrel into the pipe end mechanically, namely via the clamping cones widened in the radial direction until it is full on the inner wall of the pipe end come to the plant, so that there is the wanted and required sealing of the Cavity comes. Mechanically, by means of the clamping cones, there is a certain pre-sealing achieved, with relatively large distances due to the mechanical expansion of the seals be bridged between the pressure build-up mandrel and the inner wall of the pipe end can. In other words, the known pressure build-up mandrel can also be used with relatively use large tolerances of the pipes to be fastened.

While in the known pressure build-up mandrel, the previously explained pre-seal takes place mechanically via the clamping cones, the operational sealing of the Cavity between the pipe end of the pipe to be fastened and the one in this pipe end introduced DruckaufLaudorn compared to the increasing up to a few thousand bar Expanding by the pressure medium itself. After the mechanical pre-sealing is for this purpose abruptly in the known pressure build-up mandrel via the pressure medium supply Pressure medium supplied with very high pressure.

This pressure medium initially finds leaks in the seals before. However, the pressure drop across the seals is very high, so that the hydraulic Pressure of the pressure medium itself leads to the seals on the inclined surfaces the clamping cones are driven further outwards, which in turn reduces the resulting Sealing forces are increased. The result is a kind of self-sealing the cavity between the pipe end of the pipe to be fastened and the pressure build-up mandrel.

In the known high-pressure seal for a pressure build-up mandrel, from based on the invention, the seals are a single circumferential rubber-elastic Sealing rings educated. In order to cope with the high expansion pressures of up to several To be able to withstand a thousand bar, these seals have to be made of a material of great magnitude Shore hardness exist. This in turn means that these seals in the mechanical Pre-sealing and only one at low hydraulic pressures of the pressure medium show poor sealing effect. Especially when the inner wall of the pipe end and / or the inclined surfaces of the clamping cones have unevenness, the sealing effect leaves of these seals at relatively low pressures (up to a few hundred bar) to be desired. This leads to the fact that when using the known pressure build-up mandrel promoted relatively large volumes of pressure medium at the beginning of an expansion process have to be, since relatively high leakage losses occur.

To solve this problem, in the known pressure build-up mandrel then worked with a very high rate of pressure increase, so it is with In other words, suddenly a very high pressure in the cavity between generated the pipe end of the pipe to be fastened and the pressure build-up mandrel, so that the seals are suddenly loaded with such a high pressure that they a show good sealing effect.

The large volumes of pressure medium to be conveyed at the beginning of an expansion process and the very high pressure rise rates to be achieved lead to the known pressure build-up mandrel to the fact that the pressure generating units are very powerful and therefore have to be technically and economically complex.

In addition, there is a different type of high-pressure seal for a pressure build-up mandrel for the hydraulic expansion "known (see. DE-OS 24 00 148), in which the From the outset, seals have an outside diameter that is slightly larger than the inside diameter of the pipe end of the pipe to be fastened. Here takes place so no mechanical expansion of the seals by adjusting the clamping cones, rather, the maximum outside diameter of the seals is to a certain extent specified in advance. On the one hand, with this pressure build-up mandrel, there is the introduction of the pressure build-up mandrel in the pipe end of a pipe to be fastened is associated with a considerable amount of force, on the other hand, only very tight tolerances of the pipes to be fastened can be accepted will.

There is also a pressure build-up mandrel for hydraulic expansion State of the art (see. DE-OS 31 05 736), in which, although a preliminary seal by The seals are expanded, but this pre-sealing is not mechanical, but is also done hydraulically, namely by applying to the seals a Radially outward force is exerted from the hydraulic pressure of the pressure medium is derived. Here, too, there are only small tolerances to be fastened Pipes acceptable.

It is also known per se (cf. DE-PS 9 23 964), seals Made of elastic material over wedge rings sliding on inclined surfaces of clamping cones to support, so that it is prevented that these seals in an otherwise occurring Be pressed into the annular gap. These wedge rings, known per se, are in the longitudinal direction slotted to allow multiple use.

Finally, high-pressure seals are known per se (cf. the literature reference "Rev. machine parts, pipelines, fittings", 195 # page 1310, and the brochure 5705 G ~ Parker O-rings "from PARKER-HANNIFEN N.V., pages 66 to 70), the of two essentially ring-shaped, arranged one behind the other in the axial direction # There are sealing elements, the inner sealing elements made of a material less Shore hardness and the outer sealing elements made of a material of great Shore hardness exist.

The invention is based on the prior art explained above now the task is based on the known, initially explained high pressure seal for to design and develop a pressure build-up mandrel with adjustable clamping cones, that only very low leakage losses occur.

The high pressure seal according to the invention for a pressure build-up mandrel, in which the above-mentioned object is achieved, is characterized in that each seal consists of two essentially annular, one behind the other in the axial direction arranged sealing elements made of elastic material - O-rings - and the inner sealing elements of the seals as seen from the expansion area from one Material with a low Shore hardness and the outer sealing elements made of a material with a large size Shore hardness exist.

Taking into account the problems explained at the beginning with the Pressure build-up mandrel known from the prior art, one could get the idea to improve the sealing effect of the high-pressure seal known there for this to choose a material with a lower Shore hardness. Because of the extremely high expansion pressures but such a "soft" seal would wear out extremely quickly. According to the invention has now been recognized that for all phases of an expansion process with a Pressure build-up mandrel of the type in question can achieve optimal conditions if the seals of the high pressure seal made of two O-rings of different Shore hardness exist. During mechanical pre-sealing by adjusting the clamping cones and if the hydraulic pressure of the pressure medium is still low, only the Sealing elements with the lower Shore hardness in function. Will the cavity between the pipe end of the pipe to be fastened and the pressure build-up mandrel supplied with pressure medium, so the inner sealing elements take over first, as this is the case with the "soft" sealing elements are, the full sealing function. The pressure medium acts on these inner sealing elements exerted a force outward in the axial direction, so that these sealing elements applied pressure is also transmitted to the outer sealing elements.

The sealing function of the inner sealing elements remains so long Meaning until the outer sealing elements are under a sufficiently high pressure, thus ensure a sufficient sealing effect despite their great Shore hardness. In spite of the excellent sealing effect of the inner "soft" sealing elements a leak of pressure fluid not bypassing these sealing elements to prevent completely. This pressure medium leaking past the inner sealing elements At the beginning of the good sealing effect, the outer sealing elements accumulate in front of them.

Pressure medium accumulates between the sealing elements of the seals, the pressure of which ultimately corresponds to the pressure inside the cavity.

But now the inner "soft" sealing elements are completely pressure-compensated, d. H. the pressure of the pressure medium acts on these "soft" sealing elements of all Sides evenly. Even extremely high expansion pressures can now only result in one Compression of the "soft" sealing elements lead, but not to their destruction. Only the outer "hard" ones have to withstand the extremely high expansion pressures on one side. Sealing elements that are designed precisely for this purpose in terms of material. in the The result is the wear of the seals in the high-pressure seal according to the invention minimized.

The high-pressure seal proposed according to the invention allows its use simpler and less complex pressure generating units, since on the one hand the leakage losses are very low and on the other hand, related to leakage losses, no particularly high rate of pressure rise realized for the pressure medium must become. Despite the low rate of pressure increase possible according to the invention the required pretensioning force of the seals or those affected Sealing elements to achieve the necessary sealing effect to a certain extent by itself.

What the materials to be used for the sealing elements of the seals is concerned, the material used for the "hard" sealing elements is, for example, Perbunan 90 Shore in question. For the "soft" sealing elements of the seals one could use Think Perbunan with Shore hardnesses between 60 and 70.

It is known to use two O-rings for a seal (See the reference "DICHTUNGSPRAKTIKUM" by Ing. F. W. # Ernst Seiffert, Verlag Der Industriemeister / Hamburg, pages 153/154, in particular Fig. 72 C). However, this is an O-ring seal against rotation at pressures up to 60 kp / cm2, with a soft O-ring cushioning a relative hard O-ring is used. The use of different hardness O-rings in a keyway as a high-pressure seal for pressures in the range of a few thousand bar can result from it cannot be derived.

There are now various possibilities for the high-pressure seal according to the invention to design and develop, which are explained in the following only by way of example target.

First of all, because of the inclined surfaces of the clamping cones, it is recommended to design the high-pressure seal according to the invention so that the inner sealing elements the seals have a smaller inner diameter and a larger cord diameter than have the outer sealing elements.

In order to initially achieve a good sealing effect, the "soft" Sealing elements have an outside diameter of at least the same size in the idle state, like the "hard" sealing elements. It is particularly advantageous if the sealing elements from the material with a low Shore hardness, a slightly larger one at rest Have outer diameter than the sealing elements made of the material of great Shore hardness.

This embodiment has the particular advantage that with relatively little Pressing can be biased to achieve the desired pre-seal. on in this way it can be prevented that the seals or

Sealing elements squeezed between the clamping cones and the pipe end will. The outer sealing elements at risk in this regard need here namely only easy to be brought to bear on the inner wall of the pipe end.

In order to keep the wear of the outer sealing elements as low as possible, the use of sliding ones that serve as abutments is recommended Wedge rings, through which the otherwise existing annular gap between the inner wall of the pipe end and the pressure build-up mandrel can be bridged and closed. Accordingly recommends an embodiment of the high pressure seal according to the invention, which thereby is characterized in that the seals seen from the expansion area outside of the outer sealing elements each one on the inclined surface of the corresponding Have clamping cone sliding wedge ring. The wedge rings should, as in themselves known, each have an expansion slot, which, however, is inclined to the axial Should run in the direction of the pressure build-up mandrel. An oblique to the axial direction extending expansion slot in such a wedge ring has the advantage that the Sealing elements not very far into the expansion slot, even under very high pressures can be pushed in. This is another source of wear on the seals or sealing elements removed.

In the following the invention is based on only one embodiment illustrative drawing explained in more detail; it shows Fig. 1 in section a tube sheet with a pressure build-up mandrel inserted therein, FIG. 2 shows a wedge ring for a high pressure seal in the pressure build-up mandrel according to FIG. 1 in side view, FIG. 3 shows a high-pressure seal according to the invention in a representation corresponding to FIG. 1, but after the adjustment has taken place the clamping cones for expanding the seals, and FIG. 4 shows the object according to FIG. 3 during the actual expansion process.

Fig. 1 shows a section through the tube sheet 1, in which a tube 2 is to be fastened pressure-tight. The pipe end 3 of the pipe 2 is with game inserted into a bore 4 of the tube sheet 1. In the pipe end 3 of the to be fastened A pressure build-up mandrel 5 is introduced into the tube 2, the outside diameter of which is at rest is smaller than the inner diameter of the pipe end 3, with a relative great tolerance.

The pressure build-up mandrel 5 has an elongated, cylindrical core 6, which is completed by a hammer head-shaped end 7. On the core 6 a thread 8 is provided, with the aid of which a clamping sleeve 9 is attached to the core 6 is screwed on. The pressure build-up mandrel 5 has two axially spaced apart arranged, mutually adjustable in the axial direction and an expansion area 10 limiting clamping cones 11, 12. The clamping cone 11 is part of the hammer head-like End 7, while the clamping cone 12 is part of the clamping sleeve 9. Between the clamping cones 11, 12, a spacer sleeve 13 is arranged in the expansion area 10. Otherwise points the pressure build-up mandrel 5, specifically in its cylindrical core 6, a centrally starting one and radially tapering pressure medium supply 14 opening in the expansion area 10. The pressure medium supply 14 also penetrates the spacer sleeve 13.

The inclined surfaces 15 of the clamping cones 11, 12 are the spacer sleeve 13 facing and form with the two end faces of the spacer sleeve 13 two circumferential Seal receiving grooves 16. In each of the seal receiving grooves 16 is a circumferential Seal 17 is provided. By adjusting the clamping cones 11, 12, d. H. by screwing in the clamping sleeve 9 in the direction of the hammer head-like end 7 of the pressure build-up mandrel 5, the seals 17 are radially expandable. So, in a mechanical way, is over the clamping cones 11, 12, a preliminary seal between the pipe end 3 on the one hand and the pressure build-up mandrel 5 and the seals 17 on the other hand formed cavity possible.

As can be clearly seen from FIG. 1, each seal 17 consists of two essentially ring-shaped, arranged one behind the other in the axial direction Sealing elements 18 and 19 made of rubber-elastic material, namely O-rings. The two Sealing elements 18, 19 of each seal 17 are made of different materials Shore hardness.

The inner sealing elements 18 of the seen from the expansion area 10 Seals 17 are made of the material of low Shore hardness, while the outer Sealing elements 19 consist of the material of great Shore hardness.

As can be clearly seen in FIG. 1, the inner sealing elements have 18 of the seals 17 have a smaller inner diameter and a larger cord diameter than the outer sealing elements 19. In the resting state, moreover, the inner ones Sealing elements 18 have a very slightly larger outer diameter than the outer ones Sealing elements 19 of the seals 17.

Otherwise, the seals 17 point from the expansion area 10 outside of the outer sealing elements 19, one each on the inclined surface 15 of the corresponding clamping cone 11 or 12 sliding wedge ring 20. The wedge rings 20 are, which can be seen more clearly in FIG. 2, each with an oblique to the axial The expansion slot 21 extending in the direction of the pressure build-up mandrel 5 is provided.

3 and 4 of the drawing show the pressure build-up mandrel 5 in the Position after the mechanical adjustment of the clamping cones or pretensioning the seals 17 is reached or in the position during the expansion process as such.

In Fig. 3 it can be clearly seen that the inner sealing elements 18 of the seals 17 come to rest on the inner wall of the pipe end 3 in a sealing manner are, The wedge rings 20 are so far on the inclined surfaces 15 of the clamping cones 11, 12 have been pushed up that they are on the inner wall of the pipe end 3 to Plant come.

Fig. 4 shows, exaggerated, but therefore particularly clearly, the states during the actual expansion process. It can be clearly seen that now the outer sealing elements 19 of the seals 17 assumed the full sealing function to have. The inner sealing elements 18 made of "soft" material are on all sides pressure compensated, "swim" so, so to speak, in the pressure medium. You have, clearly recognizable in Fig. 4, on their minimum possible inner diameter drawn together. Since the sealing elements 18 of the seals 17 from all sides to the are exposed to the same pressure, there is only compression on all sides, however no damage to the sealing elements 18 despite the extremely high expansion pressures of a few thousand cash.

Fig. 4 also makes it clear how the outer sealing elements 19 against the wedge rings 20 are pressed. The expansion pressure is so high that despite the large Shore hardness of the outer sealing elements 19 of the seals 17 a considerable Deformation of the sealing elements 19 takes place.

This in turn underscores the importance of the oblique to the axial direction extending expansion slot 21 in each of the wedge rings 20.

Claims (5)

Claims: High pressure seal for a pressure build-up mandrel for pressure-tight fastening of a tube in a tube sheet or the like, with two axially with Spaced from each other, adjustable in the axial direction against each other, clamping cones delimiting an expansion area, one between the clamping cones in the expansion area arranged spacer sleeve and a preferably centrally starting and preferably radially tapering, in the expansion area opening pressure medium supply, wherein the Inclined surfaces of the clamping cones of the spacer sleeve are facing and with the two The end faces of the spacer sleeve form two circumferential seal receiving grooves, with A circumferential rubber-elastic seal is provided in each of the seal receiving grooves is and whereby the seals can be expanded radially by adjusting the clamping cones are, d a d u r c h characterized in that each seal (17) consists of two essentially ring-shaped sealing elements (18, 19) consists of rubber-elastic material - 0-rings - and the one from the expansion area (10) as seen from the inner sealing elements (18) of the seals (17) made of a material low Shore hardness and the outer sealing elements (19) made of a large material Shore hardness exist. 2. High pressure seal according to claim 1, characterized in that the inner sealing elements (18) of the seals (17) have a smaller inner diameter and have a larger cord diameter than the outer sealing elements (19). 3. High pressure seal according to claim 1 or 2, characterized in that that the sealing elements made of the material of low Shore hardness one in the idle state slightly larger outer diameter than the sealing elements made of the larger material Shore hardness. 4. High pressure seal according to one of claims 1 to 3, characterized in that that the seals (17) seen from the expansion area (10) outside the outer Sealing elements (19) each one on the inclined surface (15) of the corresponding Clamping cone (11 or 12) have sliding wedge ring (20) as a further support ring. 5. High pressure seal according to claim 4, characterized in that the wedge rings (20) each have an expansion slot running obliquely to the axial direction (21) have.