FI60615B - I ENDING REQUIREMENT DETECTOR WITH MIND TVA LJUSKAENSLIGA ELEMENT FOER INDIKERING AV HETA PARTIKLAR - Google Patents

Description

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Wa M (^ UTLÄGGNINCSSKRIFT 6061 5 C Pater, lii my.innötty 10 02 1932 r $ i ~ V ^ Patent raeddelat (51) Ky.ik.Va.3 G 01 J 5/06 // G 08 B 17/12 ENGLISH I —FI N LAN D (21) PM * n «lh» k «mut —pw« ntwek »* lr. * 1257/73 (22) HakemlsplM - AfwtUcnlngtdag l8.0U.73 ^ ^ (23) Alkuptlvt — GlWghttidig l8 .0U.73 (41) Interpreters Publications - Btlvlt offuntllg 25.10.73

National Board of Patents and Registration., .. .........

_. (44) Date of dispatch and the date of entry into service. -

Patent- och registrstyrelsen Antöktn utligd och utl. $ Krlft «n published 30.10.81 (32) (33) (31) Pyydetty etuoikeus — Begird priority 2U. 0U. 72

Sweden-Sweden (SE) 5380/72 (71) Pak Construction AB, Bergsvägen U9, lUl 05 Huddinge, Sweden-Sweden (SE) (72) Kurt Eskil Tibbling, Solna, Sweden-Sweden (SE) (7U) Oy Kolster Ab The present invention relates to at least two photosensitive elements, such as at least two photosensitive elements, such as at least two photosensitive elements. , the hot so - called to detect flammable or incandescent particles rapidly passing in the longitudinal direction of the tube through successive detection zones belonging to the respective element, formed by corresponding adjacent openings in the raster, the signals from the elements forming a pulse train used to amplify the particles via an amplifier. Examples of areas in which the invention can be applied include the pneumatic conveying of combustible particles and the pneumatic conveying of cellulosic fibers in pipelines in connection with the handling or drying of material. In this case, the particles can be heated so that they generate sparks in the danger zone, or they can be transported through such a zone by means of a carrier gas. Such incandescent particles, if they contain a sufficient amount of energy, can cause a fire or explosion that will cause great damage with subsequent outages.

The object of the invention is that glowing particles can be reliably detected, even at high speeds, and that measures can be taken in a very short time, 2,60615, such as milliseconds, to isolate the danger zone and / or to use extinguishing or suppression means before a fire or explosion occurs. .

This is achieved by a detector according to the invention, characterized in that each aperture is dimensioned so that each of the zones inside the detector detection area covers the entire cross-section of the wire, and that the part of the device facing the wire is limited by a single light and / or heat a cover layer that is substantially co-shaped within the conduit. Due to the fact that the glowing particle acts on at least two zones in a very short period of time, the alarm is prevented in the event of harmless changes in light or heat in the field of view, eg when lighting lamps, opening doors to daylight, etc. blocked. By using separate lenses for each aperture and / or a different design for the portion facing the detector lead, there is a substantially higher risk of such particle-induced blockage.

The invention will now be described in more detail with reference to the embodiments shown by way of example in the accompanying drawings.

Figure 1 shows an embodiment of a detector with a sensor attached to a pipeline.

Figures 2-4 show sections on a larger scale of three embodiments of the sensor.

In Fig. 1, reference numeral 10 denotes a tube through which a material is conveyed in particulate form, such as cellulosic fibers, by means of a mixture of a gaseous substance such as air and a flue gas. Attached to the tube is a sensor, generally indicated by reference numeral 12, which may be formed according to one of Figures 2-4. In the embodiment according to Figure 2, a housing 16 is attached to the plate 14 with a plurality, in this case six cells 18, separated by partitions 20 and covered from above by a raster-shaped roof 22. The roof 22 is provided with parallel straight slits or openings 24, one for each for cell 10. The roof is covered with a light or heat permeable layer 25 which prevents foreign particles from penetrating the cells 18. The slits 24 extend perpendicular to the longitudinal direction of the tube 10. The different cells 18 are separated from each other and apart from the slots 24 also from the environment. At the bottom of each cell, suitably like the slits 24, in the middle of the elongate cells 10 there is a photosensitive element 26 as a photocell which can capture the thermal or light radiation transmitted from inside the tube at a small space angle delimited by planes 20, JO. Each detection area thus forms a gap perpendicular to the drawing plane bounded by the planes 28,30. According to Figure 2, the different areas are separated from each other, and if the glowing particle 32 thus passes through the tube along the line 33, it will be located in the field of view of the photosensitive element of the first detection area from position 32 to position 32 '. Its residue ceases to be affected by the particle on the sensor 12 until it reaches the boundary line 28 of the next detection region, whereupon the next photosensitive element 26 receives heat radiation while the particle passes this detection region at position 32 ', and so on.

The glowing particle will thus gradually and at different times emit heat radiation to the photosensitive elements arranged in series 26.

The elements 26 are connected to one or more amplifiers 34 in the monitoring device 36. The signals output from the different photosensitive element in a pulse train then pass through a filter unit 3fl x, which is such that it only accepts pulses whose steepness (pulse front) exceeds the set value. insensitive to minor disturbances. The pulse train then passes through a pulse generator 40, a counter unit 42 and an alarm unit 44 from which alarm signals are output. In order for an alarm to occur in the embodiment of Figure 2, six photosensitive elements must be exposed in succession to the radiation of the glowing particle. In this case, the purpose is to eliminate incoming light powers, which are harmless but nevertheless affect the light-sensitive elements and which are not sorted out by the filter unit 38. The number of accepted pulses is counted in the counting device 42, which automatically resets the detector if the set number of pulses has not arrived in the normal time, thus preventing an erroneous alarm.

The radiation from normally glowing particles is in the infrared range. By selecting a photosensitive element, the sensor can be rendered insensitive to normal daylight and, for example, to light from light tubes. Furthermore, the filter unit ensures, by accepting only incoming pulses with a steep front character, that insignificant interference does not cause an alarm. The detector is thus configured in several respects to prevent an error alarm. In contrast, the detector responds to glowing particles even when the flow rate in a field of view such as tube 10 is very high, and thus the monitoring device 36 has time to quickly interrupt the process before a fire or explosion occurs in the system.

Figure 3 shows a sensor with three light-sensitive elements 46 mounted in a space 48, the roof 22 of which is formed as a grid.

The roof 22 is formed as a hemisphere and provided with parallel slits 50 which cut down the hemisphere into the plane of the photosensitive elements. Above the roof is a layer of glass 57. Using a hemisphere, the slits 50 obtain different lengths in the transverse direction of the particle path. The middle slit 50 thus becomes lower than the slots on the sides. The particle 32 passing centrally through the conduit will bypass the gaps in the detection region three times. Each time the photosensitive element 46 is exposed to radiation from the particle 32, one pulse is applied to the monitoring device 36 of Fig. 1 as described above. The embodiment according to Figure 3 is independent of the direction of transport of the particle.

In the embodiment according to Fig. 4, the sensor 12 is divided by means of a partition wall 52 into two separate detection areas, 4,60615 each of which extend into the area of a relatively large space angle ν '. Each area has a photosensitive element 54. The sensor is connected to a dome-shaped transparent sheath 56. In this case, the sensor is acted upon twice as the glowing particle passes the grid, the interruption being determined by the distance defined by the partition 52.

An area in which the invention can be advantageously used is the drying of cellulosic fibers produced by one or more milling processes.

Wet fibers are allowed to pass through a dryer to which hot gases are introduced from the burner. The dried fibers are then passed through a gas stream and through suitable fans to a cyclone where the dried fibers are separated from the gas and much of the water content is separated. The detector according to the invention is then installed in the line between the dryer and the cyclone in order to prevent the fibrous particles heated to glow in the dryer from accompanying the cyclone or a dust filter subsequently attached thereto, respectively. This eliminates the otherwise high risk of fire and explosion due to the fact that the detector virtually interrupts the drying process in the blink of an eye or, accordingly, introduces fire-retardant means into the system.

The invention is, of course, not limited to the embodiments shown, but can be modified as far as possible within the framework of the underlying idea. By selecting different types of photosensitive elements or by using different types of filters, the sensor can be made to sense radiation with the desired frequency.