GB2024681A - Tube expanding - Google Patents

Abstract

A machine and method are disclosed for expanding tube ends in an assembly of tubes (7, 8, 9, 10) in a tube-plate of a heat-exchanger, the tube-plate being formed of two spaced apart generally parallel metal sheets (1, 2) provided with confronting bores (3, 4, 5, 6) for receiving the tube ends, annular lips (12, 13, 14, 15) being provided in the sheets in the region of the bores. The expansion machine (16) includes a radially expansible, resilient plug (32), which is introduced into the tube end once the tube has been slipped in the tube-plate bore, and expansion of the plug radially outwards deforms the tube wall and provides a tight seal between the tube wall and the annular lips, which become deformed. The machine (16) includes a double-acting ram which includes a piston (18) on the stem (30) of which is the elongate annular plug (32) which, in use of the machine, can become longitudinally compressed and radially expanded. <IMAGE>

Description

SPECIFICATION An expansion machine suitable for radially expanding a tubular member, and a method of securing a tube in a tube-plate This invention relates to an expansion machine suitable for radially expanding a tubular member, and to a method of securing a tube in a tube-plate by using the expansion machine.

More particularly, but not exclusively, the present invention is applicable to the expansion in a sealtight manner ofa tube in a tube-plate of a heat-exchanger, especially large heat-exchangers made of costly materials such as stainless steel, aluminium or bronze, which, on account of the high cost of the material used, cannot be constructed with solid tube-plates for reasons of economy.

As is known, the tube bundle of a tube bundle heat-exchanger is supported at its ends by two tube-plates which have bores in which the tubes of the tube bundle must be secured in a sealtight manner. One conventional technique for this securing involves welding each tube with respect to the tube-plate. However, this technique, in addition to involving considerable expense and requiring a long working time, suffers from the disadvantage that it cannot be applied universally as there are pairs of materials, from which the tubes and tube-plates, respectively, are formed, which cannot be welded together.

Another conventional system which requires the use of solid tube plates of considerable thickness, involves forcibly introducing the tubes into the bores of the tube-plates and relying on expansion of the tubes. However, this technique suffers from the defect that it does not always afford a satisfactory tight seal between the tube and the tube-plate. In fact, the expansion of the tube concerned against the tube-plate provides an adequate seal only when tubes having a great deal thickness and a small diameter are used, that is, tubes which are sufficiently stiff to retan the deformation caused by the expansion. In contrast, when tubes having a thin wall and a large diameter are used, an elastic contraction is always experienced after the expansion, thus making it virtually impossible to obtain a satisfactory seal.

From the foregoing, it will be appreciated that the aforementioned conventional techniques cannot practicably be used in the manufacture of a large heat-exchanger in which the tube-bundle is composed of tubes having a large diameter, especially when such tubes are made of a special material and thus are expansive, and therefore they are used with thin walls for the sake of economy.

According to one aspect of the present invention, there is provided an expansion machine suitable for radially expanding a tubular member, the machine comprising an actuatable double-acting ram having a housing in which a piston is reciprocable under fluid pressure, the piston having a rod extending through and beyond the housing; and an elongate, annular, resiliently deformable plug which is formed of rubber or another plastics material and which is idly and coaxially located on a portion of the rod extending beyond the housing, there being abutment means acting or capable of acting on opposite end regions of the elongate plug during actuation of the ram in one sense, for compressing the plug longitudinally so as to cause radial expansion of the plug.

According to a second aspect of the present invention, there is provided a method for securing in a sealtight manner by expansion in a tube in a bore of a bored tube-plate, in which the tube-plate is composed of two stampped thin metal sheets which are arranged substantially parallel to one another and have in correspondence with confronting bores generally cylindrical annular lips; which method comprises locating the tube in a pair of confronting bores; radially expanding the tube by means of an expansion machine according to the first-mentioned aspect, in regions of the tube on either side of the tube-plate and opposite the annular lips, thereby causing deformation of the annular lips; causing or permitting the plug to contract radially; and withdrawing the machine from the tube.

According to a third aspect of the present invention, there is provided a method for securing in a sealtight manner by expansion a tube in a bore of a bored tube-plate in which the tube-plate is composed of two stamped thin metal sheets which are arranged substantially parallel to one another and have in correspondence with confronting bores generally cylindrical annular lips; which method comprises locating the tube in a pair of confronting bores; and radially expanding the tube in regions of the tube on either side of the plate and opposite the annular lips, thereby causing deformation of the annular lips, to form a secure seal between the tube and the tube-plate.

The present invention makes it possible to provide an efficient sealtight anchoring of a tube in the correspoding bore ofa tube-plate both quickly and economically, to a large extent irrespective of the diameter and the thickness of the tube and irrespective of the materials used to form the tube and the tube-plate respectively.

During use of the expansion machine of the present invention, the axial compression of the plug gives rise to an elastic deformation in the radial direction of the plug, this deformation having as a result the forcing of the tube in the radially outward direction, whereby expansions are created in the tube in correspondence with the outer edges of the confronting bores of the two metal sheets which form the tube-plates and in the intermediate zone ihternally of the two sheets between the annular lips, so that the tube is locked permanently in a sealtight manner to the sheets, and an elastic deformation is induced in the annular lips which thus ensures the obtention of an efficiently tight seal.

Conveniently, the ram is actuable under the influence of air or of a hydraulic medium.

Preferably the abutment means are nondeformable rings both mounted around the rod, with one ring secured with respect to the free end region of the rod and the other ring movable with respect to the rod but restrained from movement in one direction by the housing.

Conveniently, the rings are formed of nylon.

Preferably the machine includes means for adjusting the stroke of the piston of the ram.

The stroke-adjusting means can comprise a sealing and piston-abutting adjustable member which can be adjusted in the actual direction by shims.

Preferably the opposite end regions of the plug, as viewed in longitudinal section, taper and are inserted in respective corresponding annular grooves having generally the shape of a V and formed on that face of the abutment means which confronts the plug.

The housing of the ram may be equipped with a handle having a trigger for controlling fluid feed to the ram.

Fora better understanding of the present invention and to show how the same may be carried into effect, reference will now be made, by way of exaple, to the accompanying drawings, in which: Figure 1 is a fragmentary view in a cross-section of a tube-plate, in the bores of which are tubes shown in longitudinal section, there also being shown mainly as a longitudinal section an expansion device in accordance with the present invention; and Figure 2 is a longitudinal section through the expansion device shown in Figure 1.

Referring first to Figure 1, there are shown two parallel, stamped metal sheets 1,2 of reduced thickness which together constitute a tube-plate. The sheets 1,2 of the tube-plate are provided with bores 3,4,5 and 6 which confront each other and in which tubes 7,8,9 and 10 are to be expanded to form good seals.

The sheets 1 and 2 are welded at their edge regions to the side wall 11 of the heat-exchanger so as to be parallel and spaced apart from one another, and are each provided in the region of each of the bores 3,4,5 and 6 with an annular, substantially cylindrical lip, as indicated by numerals 12, 13, 14 and 15, respectively, obtained by stamping.

The sealtight securing of the tubes 7 to 10 within the colrresponding bores 3 to 6 of the sheets 1 and 2 is achieved by means of a tube expansion machine 16.

The machine 16, which is more clearly shown in Figure 2, has a generally cylindrical body 17 which is a housing for a fluid-operated double-acting ram, and within which a piston 18, fitted with a sealing ring 19, devides an active front working chamber 20 from the active rear chamber 21; the chambers 20 and 21 are in communication with a hydraulic or pneumatic feed (not shown in the drawing) via respective ducts 22 and 23 which are supported by a gun-handle 24 integral with the cylindrical body 17, and the flexble hoses 25 and 26.

The gun-handie 24 has a trigger 27 to act upon a switch 28 of an electric or magnetic valve, a 3-way valve not shown in the drawings, for directing the fluid feed to one of the active chambers 20 and 21 of the double-acting ram, and for allowing release of fluid from the other of the chambers 20 and 21.

To a front surface 29 of the piston 18 is fastened a rod 30 which projects beyond the body 17, a seal between the body 17 and rod 30 being provided by an annular gasket 31.

The rod 30 supports coaxially, on a portion beyond the body 17, an annular plug 32 of tough rubber; the annulus of the plug 32, as seen in longitudinal section, tapers at its opposite end regions 33, with the actual ends being squared off. The tapered end regions 33 are inserted into respective annular generally V-shaped grooves 34 and 35 formed in faces, which confront each other, of two nondeformable nylon rings 36 and 37 idly mounted on the rod 30.

The nylon ring 36 rests with that face which is remote from the plug 32 and which is smooth, against a face of the body 17 and is kept in fixed position thereby, whereas a corresponding smooth face of the nylon ring 37 rests against a shoulder ring 38 which is made integral with the rod 30 by means of a latching ferrule 39 screwed onto the free end of the rod 30, the ferrule 39 pressing the shoulder ring 38 against a projection 40 of the rod 30.

The active rear chamber 21, moreover, is closed in that portion confronting the piston 18 by an end stroke abutment 41 for the piston 18; the abutment 41 is equipped with a sealing gasket 42 and a screw-threaded hub 43, with which it can be adjusted axially so as to vary the strok,e of the piston 18 and thus the degree of compression ofthetough rubber plug 32; the adjustment is assisted by annular shims 44 which, slipped onto the hub 43, are held in position by a latching ferrule 45 which is screwed into the body 17 and to which, but a nut 46, the hub 43 of the member 41 is locked.

The top face of the cylindrical body 17 is provided with a supporting ring 47 which, with the aid of a counterweight cable (not shown), makes it possible to balance the weight of the expansion machine 16 to make its use more convenient.

The operation of the machine 16 will now be described.

With the two stamped sheet metal sheets 1 and 2 which make up the tube-plate correctly positioned, there is inserted in each of the bores 3 to 6 having the confronting anular lips 12 to 15, the end of a tube 7,8,9 or 10 (see the tube 10 in Figure 1), to be secured in a sealtight manner, whereafter into the tube end the gun-like expansion machine 16 is introduced (see tube 9 in Figure 1).

At this stage, by pressing and keeping pressed the trigger 27 of the expansion machine 10, oil under pressure is fed via hose 25 and duct 22 to the front working chamber 20 so that the piston 18 and therewith the rod 30 are urged rapidly towards the left (as shown in the drawings).

The result is that the tough rubber plug 32 is compressed between the nylon rings 36 and 37, which causes the plug 32 to expand radially, which is turn causes tue tube (see tube 8 in Figure 1) to expand and abutthe annular lips 12 to 15,whereby expanded areas 48,49 and 50 are formed in the tube (best seen in tube 8 or 9 in Figure 1); the tube is permanently locked in the tube-plate as the elastic deformation of the annular lips, such as 12 or 13, provides an efficiently tight seal.

Then, upon releasing the trigger 27, which is biased by a spring 51 (shown in Figure 2), the trigger is brought back to the idle position, to allow the other active chamber 21 to receive the oil feed to cause the rod 30 to shift to the right, thus enabling the plug 32 to take up its starting position.

The expansion device 16 can then be removed from the tube, with the latter left locked rigidly in a seal-tight manner in the corresponding bore of the stamped metal sheets 1,2 (see the tube 7 in Figure 1).

Claims (14)

1. An expansion machine suitable for radially expanding a tubular member, the machine comprising an actuatable doub-eacting ram having a housing in which a piston is reciprocable under fluid pressure, the piston having a rod extending through and beyond the housing; and an elongate, annular, resiliently deformable plug which is formed of rubber or another plastics material and which is idly and coaxially located on a portion of the rod extending beyond the housing, there being abutment means acting or capable of acting on opposite end regions of the elongate plug during actuation of the ram in one sense, for compressing the plug longitudinally so as to cause radial expansion of the plug.

2. An expansion machine according to claim 1, wherein the ram is actuatable under the influence of air or of a hydraulic medium.

3. An expansion machine according to claim 1 or 2, wherein the abutment means are non-deformable rings both mounted around the rod, with one ring secured with respect to the free end region of the rod and the other ring movable with respect to the rod but restrained from movement in one direction by the housing.

4. An expansion machine according to claim 3, wherein the rings are formed of a nylon.

5. An expansion machine according to any preceding claim, which includes means for adjusting the stroke of the piston of the ram.

6. An expansion machine according to claim 5, wherein the means for adjusting the stroke of the piston comprises a sealing and piston-abutting adjustable member which can be adjusted in the axial direction by shims.

7. An expansion member according to claim 6, wherein the shims are annular and are held in position by a lockable ferrule.

8. An expansion machine according to any pre ceding clam, wherein the opposite end regions of the plug, as viewed in longitudinal section, taper and are inserted in respective corresponding annular grooves having generally the shape of a V and formed on that face of the abutment means which confronts the plug.

9. An expansion machine according to any pre ceding claim, wherein the housing of the ram is equipped with a handle having a trigger for controll ing fluid feed to the ram.

10. An expansion machine substantially as hereinbefore described with reference to, and as shown in, Figure 2 of the accompanying drawings.

11. A method for securing in a sealtight manner by expansion a tube in a bore of a bored tube-plate, in which the tube-plate is composed of two stamped thin metal sheets which are arranged substantially parallel to one another and have in correspondence with confronting bores generally cylindrical annular lips; which method comprises locating the tube in a pair of confronting bores; radially expanding the tube by means of an expansion machine according to any preceding claim, in regions of the tube on either side of the tube-plate and opposite the annular lips, thereby causing deformation of the annular lips; causing or permitting the plug to contract radially; and withdrawing the machine from the tube.

12. A method for securing in a sealtight manner by expansion a tube in a bore of a bored tube-plate in which the tube-plate is composed of two stamped thin metal sheets which are arranged substantially parallel to one another and have in correspondence with confronting bores generally cylindrical annular lips; which method comprises locating the tube in a pair of confronting bores; and radially expanding the tube in regions of the tube on either side of the plate and opposite the annular lips, thereby causing deformation of the annular lips, to form a secure seal between the tube and the tube-plate.

13. A method according to claim 11, substantially as hereinbefore described with reference to Figure 1 of the accompanying drawings.

14. A tube-bundle heat-exchanger in which the tubes are secured to the tube-plates by a method according to claim 11, 12 or 13.