GB2207224A

GB2207224A - Plugging core holes of cast boilers

Info

Publication number: GB2207224A
Application number: GB08714777A
Authority: GB
Inventors: Graham Lund
Original assignee: Baxi Partnership Ltd
Current assignee: Baxi Partnership Ltd
Priority date: 1987-06-24
Filing date: 1987-06-24
Publication date: 1989-01-25
Also published as: GB8714777D0

Abstract

A boiler heat exchanger comprises a flueway and a waterway provided through at least one cast metal heat exchange chamber, which chamber has at least one core opening 15 closed by a plug 16 fitted other than by screwing into the core opening. The plug 16 may be fitted by first treating the plug cryogenically, and then locating the plug in position in the core opening of the heat exchange chamber so that as the plug warms up to the ambient temperature it expands and tightly closes the opening. Alternatively, the plug comprises a disc which is force-fitted into the core opening, sealing means being provided between the rim of the plug and the edge of the opening to close same. <IMAGE>

Description

HEAT EXCHANGER The present invention relates to heat exchangers for hot water boilers, and particularly to those used in central heating systems.

Heat exchangers for use in such boilers are typically made of at least one cast metal chamber which is provided with a series of fins extending normally from the chamber to increase the outer surface area of same. Hot flue products from the boiler are passed externally over the central heat exchange tube between the fins and water is passed through the chamber to be heated by the hot flue products.

It is an object of the present invention to close openings necessarily formed, during castiny, in the wall of the heat exchange tube by the use of a plug which can be fitted in a manner which is easier and quicker than plugs used hitherto.

According to a first aspect of the present invention there is provided a heat exchanger comprising a flueway and a waterway provided through at least one cast metal heat exchange tube, which tube has at least one core opening closed by a plug fitted other than by screwing into the core opening.

Preferably, in a first variation of the invention, the plug is fitted by first treating the plug cryogenically, and then locating the plug in position in the core opening of the heat exchange tube so that as the plug warms up to the ambient temperature it expands and tightly closes the opening.

Preferably also, in a second variation of the invention the plug comprises a disc which is force-fitted into the core opening, sealing means being provided between the rim of the plug and the edge of the opening to close same.

Preferably also, the sealing means comprise an 0being.

Alternatively, the sealing means comprise a sealant material which is applied around the rim of the plug.

According to a second aspect of the present invention there is provided a method of manufacturing a heat exchanger by casting a one-piece heat exchange tube and by closing at least one core opening formed in the tube by a plug which has been cryogenically treated so that it fits easily into the opening but as it warms up to the ambient temperature it expands and tightly closes the opening.

The various aspects of the present invention will now be described, by way of example, with reference to the accompanying drawing, in which: Figs. 1 to 6 are cross-sectional views of the wall of a heat exchanger tube showing different types of plugs according to the present invention.

In manufacturing a heat exchanger by casting, at least one core opening is necessarily formed in the wall of a heat exchange tube, which is hollow so as to define a waterway. This opening in the heat exchange tube wall must be plugged in a water-tight fashion. Usually, the opening is closed by tapping a screw thread and screwing in a threaded plug.

However, other methods of closing openings of this type have been found which are quicker and easier.

These method and closures will now be described with reference to Figs. 1 to 6, all of which show in cross-section a portion of a wall 14 of a heat exchange tube defining an opening 15, which is closed by a plug 16.

In Fig. 1, the plug 15 is a dished or cup-shaped metal plug 16, which is treated cryogenically before being fitted into the opening 15, so that the convex side of the plug 16 faces outwardly. As the plug 16 returns to the ambient temperature, it expands and forms a water-tight fit to close the opening 15. The convex side of the plug 16 is then flush with the outer surface of the wall 14. Typically, in this example the plug 16 would be made of brass.

In Fig. 2, the plug 16 is made of a plastics material and disc-shaped with restraining ribs 17 around its edges. Inwardly of the ribs 17 is a groove 18 into which is fitted an O-ring 19. The plug 16 is force-fitted into the opening 15 defined by the wall 14 so that the restraining ribs locate against the edges of the opening on the inner and outer surfaces of the wall 14 and the 0being 19 is forced into contact with the surface of the wall 14 to form a water-tight seal therewith.

The plug 16 shown i.n Fig. 3 is similar to that in Fig. 2 except that the restraining ribs 17 have been omitted. The plug 16 is simply force-fitted into the opening 15 defined by the wall 14 so that the O-ring 19 forms a water-tight seal against the wall 14. As the restraining ribs 17 are absent, the plug 16 in this example can be made of metal or a plastics material.

Fig. 4 shows a plug 16 which is dished or cup-shaped and which has again been force fitted into the opening 15 defined by the wall 14. The convex side 20 of the plug 16 faces outwardly of the wall 14 so that it is flush with the outer side 21 of the wall 14. In order to provide a water-tight seal with the wall 14, a groove 22 is provided in the plug 16 around the outer surface of the convex side 20. An O-ring 23 is located in the groove 22 and thereby is forced into sealing contact with the wall 14 around the outer edge of the opening 15 when the plug 16 is fitted into same.

In Fig. 5, the plug 16 simply comprises a flat disc which conforms to the shape of the opening 15 detained by the wall 14. The plug is force fitted into the opening, and the join between the plug 16 and the wall 14 made water-tight by means of a sealant material, such as an adhesive. If the plug 16 is tightly fitted into the opening 15, it may be possible to dispense with the sealant material, particularly as the plug 16 can be made of a metal with a higher coefficient of expansion than the wall 14. As the heat exchanger operates at a high temperature, the plug 16 will thus expand faster than the wall 14 and maintain a tight seal therewith when the heat exchanger is in use.

Fig. 6 shows a similar plug 16 to that described with reference to Fig. 5 except that a retaining rib or flange 24 is provided on the edge of the plug 16 inwardly of the wall 14. If necessary, a sealant material 25 can also be applied to the join between the plug 16 and the wall 14 to ensure a water-tight seal. Preferably, in this example, the sealant material 25 is applied between the wall 14 and the adjacent surface of the flange 24.

Claims

CLAIMS:

1. A heat exchanger comprising a flueway and a waterway provided through at least one cast metal heat exchange tube, which tube has at least one core opening closed by a plug fitted other than by screwing into the core opening.

2. A heat exchanger as claimed in claim 1 in which the plug is fitted by first treating the plug cryogenically, and then locating the plug in position in the core opening of the heat exchange tube so that as the plug warms up to the ambient temperature it expands and Lightly closes the opening.

3. A heat exchanger as claimed in claim 1, in which the plug comprises a disc which is force-fitted into the core opening, sealing means being provided between the rim of the plug and the edge of the opening to close same.

4. A heat exchanger as claimed in claim 3, in which the sealing means comprise an O-ring.

5. A heat exchanger as claimed in claim 3, in which the sealing means comprise a sealant material which is applied around the rim of the plug.

6. A method of manufacturing a heat exchanger by casting a one-piece heat exchange tube and by closing at least one core opening formed in the tube by a plug which has been cryogenically treated so that it fits easily into the opening but as it warms up to the ambient temperature it expands and tightly closes the opening.

7. A heat -exchanger, substantially as hereinbefore described with reference to any one of Figs. 1 to 6.

8. A method of manufacturing a heat exchanger, substantially as hereinbefore described with reference to Fig. 1 of the accompanying drawing.