DK142735B

DK142735B - Detector for indicating burning or glowing particles.

Info

Publication number: DK142735B
Application number: DK217873AA
Authority: DK
Inventors: Kurt Eskil Tibbling
Original assignee: Pak Construction Ab
Priority date: 1972-04-24
Filing date: 1973-04-18
Publication date: 1981-01-05
Also published as: FI60615B; DE2319033A1; NO131525B; US3824392A; DE2319033C3; FR2182486A5; DE2319033B2; SE364588B; DK142735C; NO131525C; GB1397158A; FI60615C

Description

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Opfindelsen angår en detektor til anbringelse i en rørledning og bestemt til at detektere hurtigt forbipasserende, varme partikler, hvilken detektor indeholder mindst to varme- eller lysfølsomme elementer, f.eks.The invention relates to a detector for placement in a pipeline and intended to detect rapidly passing hot particles, which detector contains at least two heat or light sensitive elements, e.g.

5 fotoceller, hvis med indbyrdes afstand i strømningsretningen beliggende synsfelter er bestemt af åbninger i en rasterblænde, og som frembringer en impulsrække, hvormed en brandbeskyttelsesindretning kan betjenes over en forstærker.5 photocells whose field of view located in the flow direction are determined by apertures in a raster aperture and which produce a series of impulses by which a fire protection device can be operated over an amplifier.

10 Som et eksempel på et område, hvor opfindelsen kan anvendes, kan nævnes pneumatisk transport af brændbare partikler, f.eks. cellulosefibre, i rørledninger i forbindelse med bearbejdning eller tørring af materialet. I sådanne tilfælde kan partikler opvarmes i en sådan grad, 15 at de danner gnister eller brændende flager inden for en farezone, eller af bæregassen transporteres gennem en sådan zone. Sådanne glødende partikler kan, hvis de indeholder en tilstrækkelig energimængde, forårsage brand eller eksplosion, som kan medføre store skader med på-20 følgende driftsafbrydelse. På den anden side skal udløsningen af en alarm med ufarlige lys- eller varmepåvirkninger, der f.eks. kan fremkomme ved tænding af lamper eller åbning af skodder for dagslys, så vidt muligt undgås.As an example of an area in which the invention may be applied, mention may be made of pneumatic transport of combustible particles, e.g. cellulose fibers, in pipelines for working or drying the material. In such cases, particles may be heated to such an extent that they form sparks or burning flakes within a hazard zone, or are carried by the carrier gas through such a zone. Such incandescent particles, if they contain a sufficient amount of energy, can cause a fire or explosion which can cause major damage with subsequent interruption of operation. On the other hand, an alarm must be triggered with harmless light or heat effects, such as may be caused by switching on lamps or opening shutters for daylight, as far as possible avoided.

25 Opfindelsen tager sigte på at tilvejebringe en detektor af den indledningsvis nævnte art, der, selv om den er af enkel og kompakt opbygning, opfylder de nævnte krav og desuden påvirker strømmen af partikler i rørledningen mindst muligt.The invention aims to provide a detector of the type mentioned in the introduction, which, although of simple and compact construction, meets the said requirements and furthermore affects the flow of particles in the pipeline as little as possible.

30 Dette opnås ifølge opfindelsen ved, at rasterblæn den udgøres af en for lys og/eller varme uigennemtrængelig, halvkugleformet kappe, der har flere, vinkelret på halvkuglens grundflade forløbende, tilnærmelsesvis halvcirkulære, parallelle slidser, der hver i sit centrum 35 har et af de varme- eller lysfølsomme elementer, og at den halvkugleformede kappe mod ledningens indre er dækket af en anden, ligeledes halvkugleformet kappe af lyseller varmegennemtrængeligt materiale.This is achieved according to the invention in that the screen aperture is constituted by a too light and / or heat impervious, hemispherical sheath having a plurality, extending perpendicular to the base of the hemisphere, approximately semi-circular, parallel slits, each having one of its centers 35 heat or light sensitive elements, and that the hemispherical sheath against the interior of the conduit is covered by another, likewise hemispherical sheath of light or heat-permeable material.

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Detektoren ifølge opfindelsen udmærker sig ved den halvkugleformede ydre kappe, der sammen med den kompakte opbygning giver lille strømningsmodstand over for luft-og partikelstrømmen i rørledningen, hvortil kommer, at 5 de halvcirkulære slidser i den indre kappe og de i slidserne centralt anbragt varme- eller lysfølsomme elementer sikrer detektering over hele ledningstværsnittet på kun et kort stykke af ledningslængden, hvorved der fås en sikker detektering af farlige varme partikler.The detector according to the invention is characterized by the hemispherical outer sheath, which together with the compact structure provides little flow resistance to the air and particle flow in the pipeline, in addition to which the semicircular slots in the inner sheath and the centrally arranged heat or slits photosensitive elements ensure detection across the entire cross-section of only a short distance of the conductor length, thereby providing a safe detection of hazardous hot particles.

10 Den enkle og kompakte opbygning gør det endvidere let at anbringe og udskifte detektoren, der f.eks. kan indskru-es i et gevind i rørvæggen.10 The simple and compact structure also makes it easy to place and replace the detector, which e.g. can be screwed into a thread in the pipe wall.

Opfindelsen forklares nærmere nedenfor under henvisning til den skematiske tegninge, hvor 15 fig. 1 viser princippet i en detektor med en i en rørledning anbragt signalgenerator, og fig. 2 en udførelsesform for detektoren ifølge opfindelsen.The invention is further explained below with reference to the schematic drawings, in which FIG. 1 shows the principle of a detector with a signal generator arranged in a pipeline; and FIG. 2 is an embodiment of the detector according to the invention.

I fig. 1 er vist et rør 10, hvorigennem der 20 transporteres et materiale i partikelform, f.eks. cellulosefibre, ved hjælp af et gasformigt medium, f.eks. en blanding af luft og forbrændingsgasser. På røret er anbragt en signalgenerator, der generelt er betegnet med 12, og som kan være udformet i overensstemmelse med det, 25 der fremgår af fig. 2.In FIG. 1, a tube 10 is shown through which a particulate material is transported, e.g. cellulose fibers, by means of a gaseous medium, e.g. a mixture of air and combustion gases. On the tube is a signal generator, generally designated 12, which may be designed in accordance with that shown in FIG. 2nd

Når en glødende partikel 32, der bevæger sig parallelt med aksen 33 i røret 10 i fig. 1, passerer signalgeneratoren 12's synsfelt, frembringes der et signal, der tilføres en forstærker 34 i en kontrol-30 udrustning 36. De som et impulstog fra flere lysfølsomme elementer i signalgeneratoren 12 udsendte signaler passerer derefter en filterenhed 38, som er således indrettet, at den kun accepterer impulser, hvis stejlhed, dvs. impulsens front, overskrider en indstil-35 let værdi, hvilket bidrager til at gøre detektoren ufølsom over for uvedkommende forstyrrelser. Impulstoget passerer derefter en impulsdanner 40, en tælleenhed 42 og en alarmenhed 44, hvorfra der udgår alarmsig- 3 142735 naler. For at der skal kunne udløses en alarm, må flere lysfølsomme elementer successivt udsættes for strålingen fra den glødende partikel. Hensigten hermed er at eliminere indkommende lyseffekter, som er ufarlige, men 5 som alligevel påvirker de lysfølsomme elementer og ikke udsorteres af filterenheden 38. Antallet af accepterede impulser tælles i tælleenheden 42, som automatisk nulstiller detektoren, hvis der ikke er indkommet det indstillede antal impulser i det normale tidsrum, hvor-10 ved falsk alarm forhindres.When a glowing particle 32 moving parallel to the axis 33 of the tube 10 of FIG. 1, passing through the field of view of the signal generator 12, a signal is generated which is applied to an amplifier 34 in a control equipment 36. The signals transmitted as a pulse train from several light-sensitive elements in the signal generator 12 then pass a filter unit 38 which is arranged so that it only accepts impulses whose steepness, ie. the front of the pulse exceeds a set value, which helps to make the detector insensitive to unauthorized interference. The impulse train then passes an impulse generator 40, a counting unit 42, and an alarm unit 44 from which alarm signals are emitted. In order for an alarm to be triggered, several light-sensitive elements must be successively exposed to the radiation from the glowing particle. The intention is to eliminate incoming light effects which are harmless but 5 which nevertheless affect the photosensitive elements and are not sorted by the filter unit 38. The number of accepted pulses is counted in the counter unit 42 which automatically resets the detector if the set number of pulses is not received. in the normal time period, where -10 by false alarm is prevented.

Normalt ligger strålingen fra glødende partikler inden for det infrarøde område. Ved valg af de lysfølsomme elementer kan signalgeneratoren gøres ufølsom for normalt dagslys og lys f.eks. fra lysstofrør. Endvidere 15 sikrer filterenheden ved kun at acceptere indkommende impulser, hvis front har en stejl karakter, at uvedkommende forstyrrelser ikke udløser alarm. Detektoren er altså i flere henseender udformet til at forebygge fejludløsning. Derimod reagerer detektoren over for gløden-20 de partikler, selv om strømningshastigheden i synsfeltet, f.eks. i røret 10, er meget stor, og kontroludrustningen 36 kan altså hurtigt nå at afbryde processen, inden der opstår brand eller eksplosion i systemet.Usually, the radiation from glowing particles is within the infrared range. When selecting the photosensitive elements, the signal generator can be rendered insensitive to normal daylight and light e.g. from fluorescent lamps. Furthermore, by accepting incoming pulses whose front is steep in nature, the filter unit ensures that unauthorized interference does not trigger an alarm. Thus, the detector is designed in several respects to prevent malfunction. In contrast, the detector responds to glowing particles, although the flow rate in the field of view, e.g. in the pipe 10, is very large, and the control equipment 36 can thus quickly interrupt the process before a fire or explosion occurs in the system.

I fig. 2 er vist en signalgenerator, som har tre 25 lysfølsomme elementer 46 anbragt i et rum 48, hvis låg 22 er udformet som et raster. Låget 22 er udformet som en halvkugle og er forsynet med parallelt forløbende spalter 50, som skærer sig ned i halvkuglen til de lysfølsomme elementers niveau. Over låget findes 30 et glaslag 57. Ved anvendelse af en halvkugle får spalterne 50 forskellige længder i retningen på tværs af partikelbanen. Den midterste spalte 50 bliver derfor længere end de ved siderne beliggende spalter. En centralt i ledningen passerende partikel 32 vil tre 35 gange passere detekteringszonens spalter. Hver gang et lysfølsomt element 46 udsættes for strålingen fra partiklen 32, går der en impuls til kontroludrustningen 36 i fig. 1. Udførelsesformen ifølge fig. 2 er uafhæn-In FIG. 2 is a signal generator having three light-sensitive elements 46 arranged in a space 48, the lid 22 of which is formed as a screen. The lid 22 is formed as a hemisphere and is provided with parallel extending slots 50 which cut into the hemisphere to the level of the photosensitive elements. Above the lid, there is a glass layer 57. Using a hemisphere, the slots 50 have different lengths in the direction across the particle path. The middle slot 50 therefore becomes longer than the lateral slots. A particle 32 passing centrally in the conduit will pass three times 35 times the detection zone slots. Each time a photosensitive element 46 is exposed to the radiation from the particle 32, an impulse goes to the control equipment 36 of FIG. 1. The embodiment of FIG. 2 is independent

Claims

142735 gig of particle transport direction. One area in which the invention can be used advantageously is in the drying of cellulosic fibers produced by one or more milling processes. The damp 5 fibers pass through a dryer, in which hot gases are introduced from a burner. The dried fibers are then fed by the gas stream and by appropriate blowers to a cyclone where the dried fibers are separated from the gas and a large part of the water content. The detector of the invention is then inserted into the line between the dryer and the cyclone to prevent fiber particles heated in the dryer from being fed to the cyclone or to a dust filter disposed thereon. This eliminates the otherwise great fire and explosion hazard, with the detector almost immediately interrupting the drying process or introducing fire retardants into the system. By choosing different types of light sensitive elements or by using different types of 20 filters, the signal generator can be made sensitive to radiation of a desired frequency. Detector for placement in a pipeline (10) and 25 for detecting rapidly passing hot particles (32), which detector comprises at least two heat or light sensitive elements (46), e.g. photocells whose fields of view located in the flow direction are determined by openings in a raster aperture (22) and which produce a series of impulses by which a fire protection device can be operated over an amplifier (34), characterized in that the raster aperture is constituted by a for light and / or heat impervious, hemispherical sheath (22) having several, approximately perpendicular to the base of the hemisphere, approximately semicircular, parallel slits (50), each having at its center one of the heat or light sensitive elements (46 ) and that the hemispherical sheath (22)