US3274579A - Fusible plug flame detection system - Google Patents

Description

Sept. 20, 1966 F. FULLER, JR

FUSIBLE PLUG FLAME DETECTION SYSTEM 2 Sheets-Sheet 1 Filed Feb. 25, 1964 FIGZ w wrw w \J Q a INVENTOR.

FULLER, JR.

FIG

FORNEY A TTORNE Y Sept. 20, 1966 F. FULLER, JR 3,274,579

FUSIBLE PLUG FLAME DETECTION SYSTEM Filed Feb. 25, 1964 2 Sheets-Sheet 2 FIG] A ION 30 I l h FIGI B FIG. 3 A 500) INVENTOR.

FQRNEY FULLER JR BY W ATTORNEY 3,274,579 FUSIBLE PLUG FLAME DETECTION SYSTEM Forney Fuller, Jr., P.0. Box 12151, New Orleans, La. Filed Feb. 25, 1964, Ser. No. 347,157 6 Claims. (Cl. 340-227) This invention relates to furnaces and fuel burners associated therewith. More particularly, the invention relates to the detection of heat associated with the burners when burning fuels such as natural gas, oil, pulverized coal, cellulose Waste, waste combustibleliquids, as in black liquor recovery furnaces, and any combination of fuels burned simultaneously in the same furnace.

On any type of fuel fired furnace, one instance being the common household gas cooking range, it is important to detect the absence of a flame While gas is still being supplied to the burner. In private dwellings employing gas cooking ranges, the absence of a flame while gas is still being supplied is generally quite rapidly observed by the odor of the issuing gas and hence preexplosive conditions due to the accumulation of large quantities of flammable gas in a room or other installation are avoided.

In distinction to the ease with which the housewife notices the lack of a flame While gas is being supplied to a burner, industrial installations require a more positive method for detecting the absence of a flame. In industrial installations, the accumulation of large quantities of combustible gases attendant a flameout is not only dangerous to life but the large capital investments make it mandatory that a satisfactory flameout detection system be available.

Prior workers in this art have taught flame failure indicator systems, such as Atwater, U.S. Patent 2,396,146 and Thomson, U.S. Patent 2,692,962, to mention only two of a variety of such systems. The efforts of prior workers in this field have generally been satisfactory and the present invention will provide workers in this area with yet another flame failure apparatus.

It is now recognized by workers in this field that fuel fired furnaces are inherently safe if the furnace space (or envelope) is held above the kindling temperature of the fuel or fuels being fired. With most commercial fuels this is thought to be 1500 F. Heretofore most flame failure detection has been by detection of light emitted from the flame. Conditions of burning can change and frequently this changes the wave length of light emitted, thereby making limited Wave length detectors inoperable.

According to the present invention, the heat from ignited fuel burners is employed to melt fusible plugs in an endless tape. The melting of the fusible plugs is a positive indication that the gas burners are flaming. The failure of the fusible plugs in the endless belt to melt is a positive indication that there has been a flame failure within the furnace or the furnace temperature has dropped below the safe kindling temperature. Suitable means are employed to detect either the melting or non-melting of the fusible plugs, such detection being suitably coupled to the fuel supply so as to cut off the latter when there is no flame or institute other safety measures such as purging the furnace with nitrogen or steam.

Accordingly, it is an object of the present invention to provide a flame failure indicating system for a furnace or other installation employing fuel burners.

It is a further object of the present invention to provide a flame failure indication system employing a movable probe travelling past the burners of a burner installation wherein the probe includes a plurality of 3,274,579 Patented Sept. 20, 1966 fusible elements whose melting or failure to melt indicates the presence or absence of the flames in the burners.

It is a further object of the present invention to provide a flame failure indication system for a furnace or other installation employing a fuel burner wherein a movable and endless belt passes through the interior of an installation employing a fuel burner and wherein the endless belt contains a plurality of fusible elements and the melting or failure to melt of the fusible elements is an indication of the presence or absence of a flame.

These and other objects will become apparent from the following description.

In the drawings:

FIG. 1 is a partially schematic view of the flame failure indication system of the present invention, being a cross-section of a large furnace having burners therein in combination with an endless flame detection belt.

FIGS. 1A and 1B are similar to FIG. 1 and show variations in the location of the endless belt.

FIG. 2 is a partially schematic and perspective view of a portion of the endless belt of the present invention in combination with an optical means for detecting the melting or non-melting of a plurality of fusible plugs in the belt.

FIG. 3 is a partially schematic view showing the flame failure indication system of the present invention employed to detect flame failure in a plurality of banks of gas burners.

FIG. 3A is similar to FIG. 3 and shows only a single burner.

The FIGURES 1, 1A, 1B show the invention as it may be used to detect furnace temperature at a relatively remote point from the burners, to assure that furnace safety is being maintained when the furnace temperature is above the minimum kindling temperature of the fuel being fired.

Referring now to FIG. 1 of the drawings, thenumeral 10 denotes generally a cross-sectional view taken of a large furnace. The commercial embodiments of large furnaces exhibit wide variations in design and the reader is requested to note that the illustrated furnace is but one of a large number with which the present flame failure indication system according to the present invention may be employed. Thenumeral 12 denotes an endless belt or tape formed of metal of suitable flexibility and high melting point. The endless belt is supported by four pulleys denoted by thenumeral 14 and motion in the indicated direction is afforded by amotor 16 coupled either directly to one of thepulleys 14 by raised Wheel face engaging the tape holes, or indirectly, as by friction, to themovable belt 12. Thenumerals 18 and 20 denote apertures leading, respectively, into and out of the furnace for the passage of the belt therein and thereout. Sealing ofapertures 18 and 20 is effected byblocks 19 and 21, see FIG. 2. Thenumeral 22 denotes a cooling device which may, in one form, consist of a cool air blast, cool oil bath, or water spray for cooling the endless tape after passing through the combustion zone of thefurnace 10. A fusible plug inserter denoted by thenumeral 24 is positioned adjacent a lower run of thebelt 12 and in association therewith aconventional photocell system 26 is positioned. Thephotocell arrangement 26 inspects the belt and insures that themechanism 24 is operating properly, i.e., that a fusible plug is inserted in each of the holes of thetape 12.

Thenumerals 30 and 32 denote elements of a detection system which, in one form, consist of a photocell and a light source such as Laser, Maser or incandescent.

A Laser beam can be made of different degrees on intensity. It should be just intense enough to penetrate dust atmosphere or smoke that may be present in the furnace; but not intense enough to damage its receiver or other parts that may come in contact with the beam. For ease of illustration, theelements 30 and 32 are shown as positioned exteriorly of thefurnace 10. In practice it will be observed that theelements 30 and 32 may also be placed either within the furnacelt) or the furnace walls are provided with high temperature glass or other transparent substances. Thenumeral 34 denotes an alarm suitably coupled withdetection elements 30 and 32. In practice, thealarm 34 is linked with the fuel input to the burners of the furnace so that a flame failure (to be described in detail later) results in the cessation of fuel fed to the furnace.

Thenumeral 50 denotes burners withinfurnace 10, and thenumeral 52 denotes a combustion zone adjacent these burners. It will be observed that thetape 12 passes, in the indicated direction of travel, substantially medially of thecombustion zone 52.

Referring now to FIGURE 2 of the drawings, thenumerals 36 denote apertures in theendless belt 12, the latter here being shown in three distinct sections for purposes of illustrations. Thenumerals 38 denote fusible plugs withinapertures 36, these being the fusible plugs which mechanism 24 inserts. Thenumeral 40 denotes thefusible plugs 38 at various stages of melting as thebelt 12 passes upwardly within furnace 1t) and into thecombustion zone 52. The fusible plug material when melted is removed by a combination of vaporization and by solid removal through the ash discharge system always located at the bottom of a furnace.

A description of the above-described elements will now be set forth, illustrating a preferred mode of operation of the flame failure indication system according to the present invention. Assuming the furnace to be in full operation with theburners 50 ignited and flame within thecombustion zone 52 performing the intended heating function within thefurnace 10, a portion of theendless belt 12 to the right of photocell system in FIG. 1 passes into thefurnace 10 throughaperture 18 and thence begins its upward travel. As it nears thecombustion zone 52, the heat due to the flames causes thefusible plugs 38 to melt, this progressive melting being indicated at 40 at FIG. 2. It will be observed that the lower run oftape 12 in FIG. 2 contains plugs completely intact while the upper run of thetape 12 shows the plugs as having been completely melted. Thus, with continued upward movement of thetape 12, thefusible plugs 38 become completely melted after having passed throughcombustion zone 52 and when they reach the area of theplug detection elements 30 and 32, theplugs 38 have all melted and the light from the detection system passes through theapertures 36 indicating that the furnace burners are operating as intended. After having passed through thecombustion zone 52 and the interior of thefurnace 10, thetape 12 is quite hot and for this purpose the coolingdevice 22 is employed to lower the temperature. This portion of the tape now passes around to theplug insertion mechanism 24 wherenew plugs 38 are inserted in the holes and the operation of the system is as above described. I

In the event of a flame failure within thefurnace 10, and a resultant lowering of furnace temperature the plugs do not melt or, if they do melt, they will melt incompletely so that the light fromdetection elements 30, 32 does not pass throughapertures 36 thus giving an indication, by means of thealarm 34, that there has been a flame failure. In such an instance, by suitable circuitry so well known by workers in this art as not to require description thereof at this point, the input to thefuel burners 50 is cut off, thus precluding the escape of flammable fuel vapor which otherwise would create a potentially dangerous explosive situation in the installation.

Referring now to FIG. 3 'of the drawings, the practice of the present invention on a furnace employing a single burner or a plurality of banks of burners is illustrated.

FIGURES 3 and 3A show the invention used adjacent to a burner or group of burners where the flame may actually impinge against the tape and fusible plugs. In

this case a higher melting temperature plug is used and detection of flame out on one burner or group of burners can be detected. In FIGURES 3 and 3A with the ex ception of the fusible plug detection elements, the numerals correspond to those of FIGURES 1 and 2 with a zero added. Thus, the numeral 120 in FIGURE 3 corresponds to theelement 12 of FIGURES 1 and 2. Referring to the detection arrangement of the embodiment of FIGURE 3, with a plurality oftapes 120 for the purpose of detecting a flame failure in any one of a plurality of burner banks 590 infurnace 100, the numeral denotes a source of light (also Maser and Laser source) whilenumerals 62, 64 and 66 denote light-sensitive elements such as photocells which are mounted, respectively, on pivoted elements 68, 70 and 72. In operation, where it is desired to detect the presence or absence of fusible plugs in theupper belt 120, gate 68 is placed in the illustrated position andlight source 60 cooperates withphotocell element 62 to make the determination. Assuming that theupper burner bank 500 is operating properly, the flames therefrom will have melted all of the plugs in theupper belt 120 and now gate 68 which carriesphotocell 62 is swung clockwise and the beam fromsource 60 may now be used to detect the presence or absence of fusible plugs in themiddle belt 120. Thus, in the arrangement illustrated in FIGURE 3, onelight source 60 may be employed to test a plurality ofbelts 120.

It will be observed that in the embodiment of FIG- URE 1, the fusibleplug detection elements 30 and 32 are placed quite near thecombustion zone 52, thus necessitating the use of high temperatureresistant elements 30 and 32 or the use of transparent materials in the walls of thefurnace 10. This is in distinction to the arrangement of FIGURE 3 wherein the fusible plug detection mechanism is located eXteriorly of the furnace. Either arrangement may be employed, and it will be observed that the greater cost necessitated by the arrangement of FIGURE 1 yields the desired result of detecting the absence of a melted plug more rapidly. In FIGURES 1A and 1B, the detection tape passes horizontally through the furnace, through the kindling temperature zone thereof. This arrangement may be employed when the width of afurnace 12 permits the tape to traverse the furnace in sufficient time to assure safe detection exteriorly of the furnace. This permits the use ofconventionalphotocell detection elements 30 and 32 in lieu of Laser and Maser.

What is claimed is:

1. A flame failure detection system including a static installation having a fuel burner therein, a probe provided with a plurality of longitudinally spaced apertures adapted to contain fusible elements, said probe positioned at least partially within said static installation and adjacent said fuel burner, and means to detect the condition of the said fusible elements, whereby detection of melting of the fusible elements indicates an ignition condition of the fuel burner and detection of the fusible elements as not melting indicates a non-ignition condition.

2. A flame failure indication system comprising a static installation having a fuel burner mounted therein, an endless belt having at least one portion therein passing through said static installation and adjacent said burner, said belt having a plurality of apertures therein, means for placing a fusible plug within each of said apertures, and means for detecting the melting of said fusible plugs to thereby determine the presence of a flame in the fuel burner.

3. The system of claim 2 wherein said detection means includes a source of radiation adapted to shine against a portion of said endless belt.

4. The flame detection system of claim 2 including means to insert fusible plugs in said tape and means for moving said belt into and out of said static installation.

5. The flame failure indication system of claim 2 including alarm means coupled to said fusible plug melting detection means, said alarm means being coupled to the fuel input to said burner to thereby cut off said fuel input when a fusible plug has not melted.

5 6 6. The method of detecting flame failure in a static References Cited by the Examiner installation having a tuel burner therein including the UNITED STATES PATENTS steps of contlnuously msertmg and Withdrawing from a combustion area within said static installation a probe 1,953,072 4/1934 Casper 340339 X having a plurality of spaced fusible elements thereon, 5 335L876 9/1962 Brown 34O 2'27 detecting the melting or non-melting of fusible elements and continuously providing said probe with new fusible NEIL READ lmary Exammer' elements. R. M. ANGUS, Assistant Examiner.

Claims (1)

1. 6. THE METHOD OF DETECTING FLAME FAILURE IN A STATIC INSTALLATION HAVING A FUEL BURNER THEREIN INCLUDING THE STEPS OF CONTINUOUSLY INSERTING AND WITHDRAWING FROM A COMBUSTION AREA WITHIN SAID STATIC INSTALLATION A PROBE HAVING A PLURALITY OF SPACED FUSIBLE ELEMENTS THEREON, DETECTING THE MELTING OR NON-MELTING OF FUSIBLE ELEMENTS AND CONTINUOUSLY PROVIDING SAID PROBE WITH NEW FUSIBLE ELEMENTS.

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