AU607329B2 - Flame monitoring - Google Patents

Description

AUSTRALIA

PATENTS ACT 1952 COMPLETE SPECIFICAT 607Form Form

(ORIGINAL)

FOR OFFICE USE Short Title: Int. Cl: Application Number: Lodged: Complete Specification-Lodged: Accepted: Lapsed: Published:

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r 1 fc Priority: Related Art: TO BE COMPLETED BY APPLICANT Name of Applicant: Address of Applicant: e-I SPECTUS LIMI'ED 56 SUTTONS PARK AVENUE SUTTONS INDUSTRIAL PARK READING, BERKSHIRE RG 6 1AZ

ENGLAND

GRIFFITH HACK CO., 601 St. Kilda Road, Melbourne, Victoria 3004, Australia.

Actual Inventor: SAddress for Service: es Complete Specification for the invention entitl,.d: FLAME MONITORING.

The following statement is a full description of this invention including the best method of performing it known to me:- ~_iL .Il*^l.l~i~ili -ii~~~181 1A- FLAME MONITORING

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B SO Br S BS0 This invention relates to flame monitoring.

The use of flame monitors in industry is widespread. A common requirement of most of them is the need to maintain the flame sight tube in a clean condition to prevent obscuration of the monitored flame. Another requirement is the need to check periodically that the flame monitor system responds correctly to a "flame-out" often termed a "dark check" The first of these is usually achieved by allowing air to flow down the sight tube, either continuously or in periodic bursts. The second can only be achieved by temporarily blocking the radiation from the flame and then checking that the flame monitor "flame on" indication reverts to "flame off". This is often achieved by means of an electrically operated shutter.

According to the invention there is provided a flame monitor comprising a means positionable between a sight tube and a flame detector and which is responsive to the pressure of a supply of pressurized gaseous fluid to inhibit the passage of flame radiation from the sight tube to i-k I -i J 1 2 the flame detector and to cause the gaseous fluid to flow along the sight tube thereby to purge the sight tube of dust.

In order that the invention may be well understood there will now be described an embodiment thereof, given by way of example, with reference to the accompanying drawing of which the single figure is a schematic side view, partly sectioned, of a flame monitor.

The flame monitor, generally referenced 1, as Is normal employs some means of detecting the presence of the flame, i.e. a flame detector, .o mounted at one end of a sight tube 2. The sight tube, where the flame monitor has an industrial furnace application, is inserted into the furnace in VoI such a way that the field of view encompasses the n d flame to be monitored.

o i An air chamber 3 of rectangular croswsection is mounted between a coupling tube end 4 of the flame detector and the furnace end of the sight tube 2.

s i The air chamber 3 is defined within a boxlike enclosure 5 to which is fitted an inlet port 6 for a supply of compressed air and within which is positioned a thin flap 7 of springy material such as phosphor bronze which is anchored at one end by a :0o0:screw 8 to the enclosure wall. The flap 7 is desigled and positioned so that, when compressed air is applied, the flap bends about its anchored end to an extent shown by its broken line position so that it provides a transverse barrier across the air chamber 3 to prevent flame radiation from reaching the flame detector. At the same time the f lap 7 diverts the air stream away from the flame detector and down the sight tube 2 towards the furnace, thus

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yr"i ;I:rr~lir-L~L~L~L~L~L~YI~ ii C- 3 purging the sight tube of any accumulated dust.

When the air supply is shut off, the flap 7 springs back to its original, full line position allowing the passage of flame radiation through the air chamber 3 from the sight tube 2 to the flame detector.

In practice, the timing and duration of the flow of air will be controlled by the flame monitor system itself, or by an independent controller.

Whilst the flap 7 as described is of springy material, it will be appreciated that a resilient or spring means independent of the flap (which, thus, need not be springy) could be utilized to bias the flap back to its original position upon closure of the air supply.

S* Accordingly, both functional requirements as set out hereinbefore of the flame monitor can be o provided by using only a compressed air supply.

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Claims (7)

1. A flame monitor comprising a means positionable between a sight tube and a flame detector and which is responsive to the pressure of a supply of pressurized gaseous fluid to inhibit the passage of flame radiation from the sight tube to the flame detector and to cause the gaseous fluid to flow along the sight tube to purge the sight tube of dust.

2. A flame monitor as claimed in claim 1, wherein said means comprises a chamber having an inlet port connected to a supply of pressurized gaseous fluid and a barrier member in the chamber which is responsive to the pressure of gaseous fluid when supplied to the inlet port to extend across the chamber to a position such as to interrupt the passage of flame radiation from the sight tube to the flame detector and to divert the gaseous fluid entering the chamber away from the flame detector and along the sight tube. si p

3. A flame monitor as claimed in claim 2, wherein the barrier member is a flap secured at one •end to a wall of the chamber and of a resiliently S deformable material so as to bend to its said interrupt and divert position under the pressure of said gaseous fluid and to return, when said gaseous fluid supply to the inlet port is terminated, to another position adjacent the wall of the chamber at which to allow the passage of flame radiation through the chamber from the sight tube to the flame detector, 1.

4. A flame monitor as claimed in claim 2 or claim 3, wherein the pressurized gaseous fluid is compressed air.

A flame monitor as claimed in any of claims 2 to 4, wherein the chamber is mounted between the sight tube and the flame detector.

6. A flame monitor as claimed in any of claims 2 to 5, wherein the chamber is of rectangular cross- section. <e

7. A flame monitor substantially as herein described with reference to the accompanying drawing. .4 DATED THIS 17TH DAY OF MAY 1989 1 *o SPECTUS LIMITED By its Patent Attorneys: *4 GRIFFITH HACK CO. Fellows Institute of Patent Attorneys of Australia. A