GB2156971A

GB2156971A - Temperature measurement

Info

Publication number: GB2156971A
Application number: GB08408442A
Authority: GB
Inventors: Gordon Thatcher; Barrie Grainger Ferguson; John Peter Winstanley; Reginald Dacey
Original assignee: UK Atomic Energy Authority
Current assignee: UK Atomic Energy Authority
Priority date: 1984-04-02
Filing date: 1984-04-02
Publication date: 1985-10-16
Also published as: GB2156971B; GB8408442D0

Abstract

A temperature measurement system, such as for measuring the temperature of a braze (21) between an outer tube (22) and an inner tube (23), comprises an optical fibre (13) which looks at the inclined face (20A) of a reflective plug (20). The face (20A) itself views the inner wall of the inner tube (23) in the region of the braze through viewing openings (19). Fibre (13) and plug (20) may be contained within a common capillary tube (12). <IMAGE>

Description

SPECIFICATION Temperature measurement This invention relates to the measurement of temperature. It has originated in the course of investigating problems that arise in effecting brazes especially brazes made in the course of repairing defective tube/tube plate welds. (See for example EP Pat Appl No 83306812.5).

Access for temperature measurement at a braze between two tubes, one inside the other, is limited when the inner tube is filled with an induction heating probe. However, such measurement can be effected by a quartz fibre located in the heating probe and penetrating the wall of the probe in the region of the braze so that this end of the fibre looks at the inner wall of the inner tube in the region of the braze. An optical pyrometer is coupled with the cold end of the fibre.

However the hot end of the fibre can become fogged and this can give rise to incorrect temperature readings.

In accordance with the present invention a temperature measurement system involving an optical fibre and a hot source is characterisad in that the fibre is terminated to look at the inclined reflective surface of a plug end-spaced from he end of the optical fibre and disposed so that the reflective surface observes directly the hot source.

One form of the invention will now be described with reference to the accompanying drawings, in which Figure 1 is a section through one type of induction heating probe for effecting a braze between two tubes, one inside the other; arc' Figure 2 is a section on the line il-ll of Figure 1 with the addition of the two tubes being brazed.

In Figure 1 a water-cooied induction heating probe has an outer tube 10 and an inner tube 11 eccentrically located in the tube 10 to accommodate a capillary tube 12 in which there is located an optical fibre 13. Inside the tube 11 there is a flux-generating unit comprisiny a stack of ferrite cores (not shown) supported on a spider 18. The cores have an energising winding 14 the ends of which terminate respectively at a weld 16 on an inner conducting tube 15 and a weld 17 at the bottom cup of the inner tube 11. (The flux generating unit is described in more detail - EU Pat Appl No 83306812.5). The capillary tube 12 and outer tube 10 both have viewing openings 19.

Figure 2 shows the termination i.3A of fibre 13. A gold plug 20 is also provided in the capillary tube 12 and this terminates at the inclinsd spectrally linear reflective surface 20A spaced from termination 13A. The termination 13A looks at -he reflective surface 20A and the surface 20A observes the heat source directly throuyh the opening 19, the heat source being the inner surface of an inner tube 23 in the region of a braze 21 to an outer tube 22.

Tube 23 may be a sleeve repairing the tube 22 which leaks at a joint with a tube plai-e.

The remoteness of surface 10A from the heat source reduces fogging. The termination 13A is a conventional one requiring simple techniques of preparation.

1. A temperature measurement system involving an optical fibre and a hot source characterised in that the fibre is terminated to look at the inclined reflective surface of a plug end-spaced from the end of the optical fibre and disposed so that the reflective surface directly observes the hot source.

2. A system as claimed in claim 1 in which the reflective surface is at the end of a gold plug in a capillary tube, which tube also houses the optical fibre, and a viewing opening is provided in the capillary tube through which the reflective surface observes the heat source directly, and the end of the optical film does not observe the heat source directly.

3. A system as claimed in claim 2 in which the capillary tube lies inside a water-cooled heating probe with a viewing opening in line with the viewing opening in the capillary tube.

4. A system as claimed in claim 3 in which the probe is located inside an inner tube being brazed to our outer tube with the viewing windows looking at the inner wall of the inner tube in the region of the braze.

5. A system as claimed in claim 1 substantially as hereinbefore 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 **. SPECIFICATION Temperature measurement This invention relates to the measurement of temperature. It has originated in the course of investigating problems that arise in effecting brazes especially brazes made in the course of repairing defective tube/tube plate welds. (See for example EP Pat Appl No 83306812.5). Access for temperature measurement at a braze between two tubes, one inside the other, is limited when the inner tube is filled with an induction heating probe. However, such measurement can be effected by a quartz fibre located in the heating probe and penetrating the wall of the probe in the region of the braze so that this end of the fibre looks at the inner wall of the inner tube in the region of the braze. An optical pyrometer is coupled with the cold end of the fibre. However the hot end of the fibre can become fogged and this can give rise to incorrect temperature readings. In accordance with the present invention a temperature measurement system involving an optical fibre and a hot source is characterisad in that the fibre is terminated to look at the inclined reflective surface of a plug end-spaced from he end of the optical fibre and disposed so that the reflective surface observes directly the hot source. One form of the invention will now be described with reference to the accompanying drawings, in which Figure 1 is a section through one type of induction heating probe for effecting a braze between two tubes, one inside the other; arc' Figure 2 is a section on the line il-ll of Figure 1 with the addition of the two tubes being brazed. In Figure 1 a water-cooied induction heating probe has an outer tube 10 and an inner tube 11 eccentrically located in the tube 10 to accommodate a capillary tube 12 in which there is located an optical fibre 13. Inside the tube 11 there is a flux-generating unit comprisiny a stack of ferrite cores (not shown) supported on a spider 18. The cores have an energising winding 14 the ends of which terminate respectively at a weld 16 on an inner conducting tube 15 and a weld 17 at the bottom cup of the inner tube 11. (The flux generating unit is described in more detail - EU Pat Appl No 83306812.5). The capillary tube 12 and outer tube 10 both have viewing openings 19. Figure 2 shows the termination i.3A of fibre 13. A gold plug 20 is also provided in the capillary tube 12 and this terminates at the inclinsd spectrally linear reflective surface 20A spaced from termination 13A. The termination 13A looks at -he reflective surface 20A and the surface 20A observes the heat source directly throuyh the opening 19, the heat source being the inner surface of an inner tube 23 in the region of a braze 21 to an outer tube 22. Tube 23 may be a sleeve repairing the tube 22 which leaks at a joint with a tube plai-e. The remoteness of surface 10A from the heat source reduces fogging. The termination 13A is a conventional one requiring simple techniques of preparation. CLAIMS