GB1601951A

GB1601951A - Tube to tube plate joint

Info

Publication number: GB1601951A
Application number: GB526277A
Authority: GB
Original assignee: Covrad Ltd
Current assignee: Covrad Ltd
Priority date: 1978-05-02
Filing date: 1978-05-02
Publication date: 1981-11-04

Description

(54) TUBE TO TUBE PLATE JOINT (71) We, COVRAD LIMITED, a British Company, of Sir Henry Parkes Road, Canley, Coventry do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be described in and by the following statement: This invention relates to a method of forming a tube to tube plate joint, such as are used, for example, in heat exchangers to join a plurality of parallel tubes into an end plate known as a tube plate, and to a tube and tube plate assembly.

In order to ensure that a tube to tube plate joint has adequate strength and is leak-tight in service. it is current practice to use thick tube plates. For example, in heat exchangers having circular-section tubes of 3/4 inch (19 mm) diameter, a tube plate of 3/4 inch (19 mm) thickness is typically used. the tube being inserted into a circular hole in the tube plate and roller expanded into contact with it. Grooves may be formed in the circular hole as described for example in British Patent No. 849,640.

In order to reduce weight and the cost of metal, it is desirable to use much thinner tube plates: however there are problems in making strong, leak-tight joints. As a solution to such problems the use of separate bushes welded into each hole in the tube plate is possible, but expensive. It has also been proposed to pierce the tube plate and press out collars surrounding the resultant holes, which collars have portions adjacent the plane of the tube plate which are cylindrical and normal to the plane of the tube plate. It has been found that this cannot be achieved by conventional means over sufficient length of tube and in the plane of the tube plate to give the desirable strength and intimate contact area between the tube and tube plate, even with holes of over 3/4 inch diameter.

According to one aspect of the present invention, a method of manufacturing a tube to tube plate joint comprises the steps of flow drilling a metal plate to form a hole having a flange upstanding from the plane of the plate, inserting a metal tube into the hole, and expanding the tube into contact with the internal wall of the flange to form a metal to metal seal between the tube and the flange.

The technique of-flow drilling is that in which a piercing tool forms a hole in a metal plate by pressure and friction-generated heat which hole is of predetermined shape and is surrounded by a wall of which its axial length is greater than the thickness of the plate.

According to another aspect of the invention a method of manufacturing a tube to tube plate joint comprises the steps of forming a hole in a plate so that a flange integral with the plate is formed around the hole, the flange extending to both sides of the plate, inserting a metal tube into the hole, and expanding the tube into contact with the internal wall of the flange to form a metal to metal seal between the tube and the flange.

According to a further aspect of the invention, a tube and tube plate assembly comprises a metal plate having a hole surrounded by a flange extending to both sides of the plate and integral with the plate, and a metal tube received within the hole and in contact with the internal wall of the flange to form a metal to metal seal between the tube and the flange.

An embodiment of the invention will now be described by way of example only and with reference to the accompanying drawings, in which: Figure 1 is a section through part of a tube plate and adjacent part of two tubes of a heat exchanger before expansion of the tube into contact with the sides of the holes, and Figure 2 is a perspective view of part of the tube plate and the adjacent part of a number of tubes.

Referring to Figure 1. a metal tube plate 10 is formed with a number of holes 11, to receive a number of parallel tubes 13 to be joined to the tube plate, by the flow drilling technique.

One suitable form of flow drilling technique is described in, for example, British Patent Specification No. 1,455,276.

The flow drilling technique is employed to form a circular hole 11 having a flange around the hole which is integral with tube plate 10 and which extends for a substantial distance to both sides of the tube plate. In this way a flange 12 or bush with an accurately-formed internal, cylindrical wall of the required internal diameter, for example, 3/4 inch (19 mm) and of similar length, may be formed.

A metal tube 13 is inserted into each hole, so as to extend through the entire length of the flange 12, and the tube 13 is then expanded into intimate metal to metal contact with the flange 12 to seal the flange against the tube and make a joint by use of a roller expander, by passing a mandrel through the tube, or by other suitable means.

The joint between the tube 13 and tube plate 10 may be made at the end of the tube, as shown, or between its ends; moreover the tube may be provided with secondary heat exchange surfaces (not shown) of any convenient known form.

It will be appreciated that the length of the flange 12 will vary with the thickness of the plate 10 and the size of hole 11 formed by the flow drilling process.

The relative dimensions of the flange length, hole diameter and plate thickness may be as follows: dit in the range 3 to 5, typically less than 4, 1/tin the range 22 to 5, typically less than 4.

and lid in the range 21 to 1 typically - where d is the hole diameter, l is the flange length t is the plate thickness.

It will be understood that although the invention is concerned with forming a flange in a metal plate, the flange extending to both sides of the plate, this flange can be formed by means other than flow drilling, for example a two-stage press tooling operation can produce a flange of the same general form as that illustrated.

WHAT WE CLAIM IS: 1. A method of manufacturing a tube to tube plate joint comprising the steps of flow drilling a metal plate to form a hole having a flange upstanding from the plane of the plate, inserting a metal tube into the hole, and expanding the tube into contact with the internal wall of the flange to form a metal to metal seal between the tube and the flange.

2. A method of manufacturing a tube to tube plate joint comprising the steps of forming a hole in a plate so that a flange integral with the plate is formed around the hole, the flange extending to both sides of the plate, inserting a metal tube into the hole, and expanding the tube into contact with the internal wall of the flange to form a metal to metal seal between the tube and the flange.

3. A method according to claim 2 wherein the hole is made by flow drilling which also produces said flange.

4. A method according to claim 1, 2 or 3 wherein the tube is expanded by the operation of a roller expander.

5. A tube and tube plate assembly comprising a metal plate having a hole surrounded by a flange extending to both sides of the plate and integral with the plate, and a metal tube received within the hole and in contact with the internal wall of the flange to form a metal to metal seal between the tube and the flange.

6. An assembly according to claim 5 comprising a plurality of flanged holes in each of which is received a metal tube, the tubes extending parallel to one another.

7. An assembly according to claim 5 or 6 wherein the ratio of the hole diameter to the plate thickness lies in the range 3 to 5.

8. An assembly according to any one of claims 5, 6 or 7 wherein the ratio of the length of the flange axially of the tube to the plate thickness lies in the range 22 to 5.

9. An assembly according to any one of claims 5 to 8 wherein the ratio of the length of the flange axially of the tube to the hole diameter lies in the range 21 to 1.

10. A tube and tube plate assembly substantially as described with reference to the drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. the tube plate and the adjacent part of a number of tubes. Referring to Figure 1. a metal tube plate 10 is formed with a number of holes 11, to receive a number of parallel tubes 13 to be joined to the tube plate, by the flow drilling technique. One suitable form of flow drilling technique is described in, for example, British Patent Specification No. 1,455,276. The flow drilling technique is employed to form a circular hole 11 having a flange around the hole which is integral with tube plate 10 and which extends for a substantial distance to both sides of the tube plate. In this way a flange 12 or bush with an accurately-formed internal, cylindrical wall of the required internal diameter, for example, 3/4 inch (19 mm) and of similar length, may be formed. A metal tube 13 is inserted into each hole, so as to extend through the entire length of the flange 12, and the tube 13 is then expanded into intimate metal to metal contact with the flange 12 to seal the flange against the tube and make a joint by use of a roller expander, by passing a mandrel through the tube, or by other suitable means. The joint between the tube 13 and tube plate 10 may be made at the end of the tube, as shown, or between its ends; moreover the tube may be provided with secondary heat exchange surfaces (not shown) of any convenient known form. It will be appreciated that the length of the flange 12 will vary with the thickness of the plate 10 and the size of hole 11 formed by the flow drilling process. The relative dimensions of the flange length, hole diameter and plate thickness may be as follows: dit in the range 3 to 5, typically less than 4, 1/tin the range 22 to 5, typically less than 4. and lid in the range 21 to 1 typically - where d is the hole diameter, l is the flange length t is the plate thickness. It will be understood that although the invention is concerned with forming a flange in a metal plate, the flange extending to both sides of the plate, this flange can be formed by means other than flow drilling, for example a two-stage press tooling operation can produce a flange of the same general form as that illustrated. WHAT WE CLAIM IS:

1. A method of manufacturing a tube to tube plate joint comprising the steps of flow drilling a metal plate to form a hole having a flange upstanding from the plane of the plate, inserting a metal tube into the hole, and expanding the tube into contact with the internal wall of the flange to form a metal to metal seal between the tube and the flange.