Abstract:
A smoke density monitor for mounting on a ship smokestack. The smoke density monitor provides a transmitter head and a receiver head mounted to a smokestack. The transmitter head and receiver head are optically connected with a density monitor by means of fiber-optic lines. The density monitor is electrically connected to an alarm monitor, which at pre-set smokestack smoke densities activates an alarm and/or shuts down the ship&#39;s burner(s). An optional recorder may be connected to the alarm monitor to preserve a record of smoke density. Each transmitter and recorder head has an optical head slidably attached to a head housing for ease of servicing and maintenance.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to opacity measurement devices, and in particular to a smoke or dust density monitor. 
     2. Background of the Invention 
     Ships are used extensively in the transportation of goods all over the world. During recent years the ecological impact of these vessels has come under heightened scrutiny. One of the environmental aspects of ship operation are the emissions which emerge from the ship&#39;s funnel, or smokestack. From an environmentally-friendly point of view, it is desirable to minimize smoke emissions from ship smokestacks. 
     Increasingly, regulations are being passed to encourage reduced ship smokestack emissions. For example, during the year 2000 the state of Alabama is testing a program to monitor ship boiler burner smoke emissions at the smokestack. In the year 2001, smoke emissions monitoring will be required for ships operating in Alabama waters. 
     Thus it is becoming increasingly important to provide an efficient, accurate apparatus to measure ship burner smoke emissions. Ideally, the smoke monitor should be located on the smokestack itself, and provide alarm and burner shut-down functions if smoke emissions exceed the appropriate thresholds. In addition, a means of providing a record of emissions levels would be desirable. 
     Existing Designs 
     One approach to measuring the density of smoke emanating from a ship&#39;s funnel has been to place a twelve volt incandescent light bulb on one side of the funnel, and a photovoltaic cell diametrically opposed on the opposite funnel side. Theoretically, the photo-voltaic cell then emits a voltage signal inversely proportional to the smoke density within the funnel. 
     A number of problems exist with the incandescent light bulb/photovoltaic cell approach. One problem involves ambient light pollution. Because the photovoltaic cell reacts to all visible light, during bright daylight the voltage out from the photovoltaic cell will be greater than during the night. Thus, ambient light pollution can cause smoke density measurement inaccuracies. It would be desirable to use a smoke detector whose operation is not based on measurements taken in the visible light spectrum. 
     Another problem with the incandescent light bulb/photovoltaic cell approach involves equipment reliability. A typical twelve-volt incandescent light bulb will burn only 7,000 hours, and then requires replacement. In addition, the type of photovoltaic cell used in this application is generally a selenium cell, which bums out after approximately 10,000 hours. Exacerbating this reliability problem is the physical placement of conventional funnel smoke density measurement light bulbs and photovoltaic cells: they are generally placed high on the smokestack, rendering replacement laborious and difficult. In addition, these elements are typically secured with three or more screws, making replacement quite a chore. It would be desirable to have a slide-in, slide-out installation for easier maintenance. 
     Still another problem associated with the incandescent light bulb/photovoltaic cell approach is the tendency of the incandescent light bulb to heat up during operation. A hot light bulb attracts dust, which coats the bulb, and reduces its visible light output. This reduction of light output may be interpreted by the photovoltaic cell to be increased smoke density, and lead to measurement errors. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a smoke density monitor which does not operate in the visible light spectrum. Design features allowing this object to be accomplished include a transmitter head which emits infrared light, which in turn is detected by a receiver head. Advantages associated with the accomplishment of this object include elimination of the light pollution associated with incandescent light bulb/photovoltaic cell, and consequently increased smoke density monitor accuracy. 
     It is another object of the present invention to provide a smoke density monitor which provides increased reliability. Design features allowing this object to be accomplished include a transmitter head and a receiver head connected to a density monitor via fiber-optic lines. Benefits associated with the accomplishment of this object include reduced necessity of maintenance, and hence decreased costs. 
     It is still another object of this invention to provide a smoke density monitor which is easily maintained. Design features enabling the accomplishment of this object include a transmitter head and receiver head which are easily removed from the smokestack upon which they are mounted. Advantages associated with the realization of this object include easier maintenance, less time required to access the transmitter head and receiver head, and consequently less maintenance cost. 
     It is another object of the present invention to provide a smoke density monitor which discourages dust from settling on the transmitter and receiver heads. Design features allowing this object to be accomplished include a trap chamber, and a sealing air supply communicating with a head housing exit chamber, which in turn communicates with a smokestack bore through an exit chamber mouth. Benefits associated with the accomplishment of this object include a chamber where particulate matter may be trapped, and also airflow movement away from the transmitter or receiver heads, thereby reducing dust build-up on same, and consequently reduced smoke density measurement errors. 
     It is yet another object of this invention to provide a smoke density monitor which is relatively inexpensive. Design features allowing this object to be achieved include the use of off-the-shelf components, and the use of components made of readily available materials. Benefits associated with reaching this objective include reduced cost, and hence increased availability. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention, together with the other objects, features, aspects and advantages thereof will be more clearly understood from the following in conjunction with the accompanying drawings. 
     Three sheets of drawings are provided. Sheet one contains FIG.  1 . Sheet two contains FIG.  2 . Sheet three contains FIG.  3 . 
     FIG. 1 is a schematic view of a smoke density monitor. 
     FIG. 2 is a side cross-sectional view of a transmitter head ready to be mounted on a smokestack, and a receiver head already mounted on the smokestack. 
     FIG. 3 is a side cross-sectional view of a head housing and its mating optical head. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 is a schematic view of smoke density monitor  2 . Smoke density monitor  2  comprises transmitter head  4  installed on smokestack  12  in optical alignment with receiver head  6 . Transmitter head  4  and receiver head  6  are optically connected to density monitor  22  by means of fiber-optic lines  8 . 
     In operation, density monitor  22  sends an infrared signal through fiber-optic line  8  to transmitter head  4 , which directs same to receiver head  6  through smokestack bore  16  as indicated by arrow  20 . The infrared signal emitted from transmitter head  4  is picked up by receiver head  6 , diminished in strength as dictated by the density of smoke  18  within smokestack bore  16 , and sent back to density monitor  22  through fiber-optic line  8 . Smoke density monitor  22  interprets the infrared light from receiver head  6  and converts it into an electrical signal, which is then used by alarm monitor  34  to sound an alarm  32 , shut down burner  38 , etc. 
     Alarm  32  is connected to density monitor  22  by means of line to alarm  30 . Density monitor  22  is connected to power supply  28 . In addition, an optional line  26  is connected to density monitor  22 , to which optional equipment may be connected. By virtue of this connection, when a specified density threshold of smoke  18  is reached, alarm  32  may sound. 
     Density monitor  22  is electrically connected with alarm monitor  34  by means of line to alarm monitor  24 . Alarm monitor  34  is powered by power supply  28 . Alarm  32  is electrically connected to alarm monitor  34  by means of line to alarm  30 . By virtue of this connection, when a specified smoke density threshold is reached, alarm  32  may sound. Recorder  42  is electrically connected with alarm monitor  34  by means of optional line to recorder  40 . By virtue of this connection, an on-going record of the density of smoke  18  within smokestack bore  16  may be preserved. In addition, burner  38  is electrically connected to alarm monitor  34  by means of line to burner  36 . By virtue of this connection, when a specified smoke density threshold is reached, burner  38  may be shut down. 
     FIG. 2 is a side cross-sectional view of transmitter head  4  ready to be mounted on smokestack  12 , and receiver head  6  already mounted on smokestack  12 . Transmitter head  4  and receiver head  6  are mounted to smokestack  12  by means of mounting tubes  46  having respective mounting tube bores  48 . If smokestack  12  is wrapped in smokestack insulation  14 , mounting tube extends far enough away from smokestack  12  to extend beyond insulation  14 . Each mounting tube is attached to smokestack  12  over a smokestack aperture  17 . In the preferred embodiment, mounting tubes  46  were attached to smokestack  12  at smokestack apertures  17  by means of a weld attachment, as indicated by weld symbol  47 . Referring now also to FIG. 3, each mounting tube  46  comprises a means of attachment to a head housing  60 . In the preferred embodiment, the attachment means comprised a mounting tube thread  50  sized to mate with a head housing thread  68  disposed in exit chamber mouth  83 . Thus, transmitter head  4  and receiver head  6  are in optical communication with smokestack bore  16  through their respective mounting tubes  46 . 
     FIG. 3 is a side cross-sectional view of head housing  60  and its mating optical head  90 . Transmitter head  4  and receiver head  6  are identical components; their function as transmitter or receiver is determined by their respective connection with density monitor  22 . Thus, transmitter head  4  and receiver head  6  comprise identical optical heads  90  and head housings  60 , and mount on identical mounting tubes  50 , and the following discussion applies to both equally. 
     Head housing  60  comprises head chamber  78 , trap chamber  80  and exit chamber  82 . Head chamber  78  is defined at one extreme by head chamber mouth  62 , and at an opposite extreme by second bulkhead  66 . Trap chamber  80  is defined at one extreme by second bulkhead  66 , and at an opposite extreme by first bulkhead  64 . Exit chamber  82  is defined at one extreme by first bulkhead  64  and at an opposite extreme by exit chamber mouth  83 . 
     Head chamber  78  is separated from trap chamber  80  by second bulkhead  66 , and communicates with trap chamber  80  through second bulkhead aperture  67  in second bulkhead  66 . Trap chamber  80  is separated from exit chamber  82  by first bulkhead  64 , and communicates with exit chamber  82  through first bulkhead aperture  65  in first bulkhead  66 . 
     Optical head  90  comprises optical lens  92  and optical head bore  94 . Optical head bore  94  is sized to admit an extreme of head housing  60  at which head chamber mouth  62  is disposed. Head chamber mouth  62  is sized to admit optical head lens  92 . A sealing means is disposed around an outer surface of head housing  60  at an extreme of head housing  60  at which head chamber mouth  62  is disposed. 
     In the preferred embodiment, the sealing means comprised at least one O-ring  70  disposed around an outer surface of head housing  60  adjacent head chamber mouth  62 , and optical head bore  94  was sized to frictionally admit the at least one O-ring  70 . In the preferred embodiment, head housing  60  comprised pin  96  disposed on an outer surface of head housing  60 , and optical head  90  comprised slot  98  sized to admit pin  96 , whereby an angular orientation of optical head  90  may be fixed relative to head housing  60 . 
     Exit chamber  82  communicates with an exterior of head housing  60  by mean of tester aperture  86  and sealing air fitting bore  72 . Unless a tester  52  is being used to calibrate smoke density monitor  2 , tester aperture  86  is hermicatally blocked by plug  88 . 
     Referring now also to FIGS. 1 and 2, sealing air from sealing air supply  10  is supplied to exit chamber  82  through check valve  9 , sealing air lines  11 , and sealing air fitting  71 . In the preferred embodiment, sealing air fitting  71  was attached to head housing  60  by means of sealing air fitting thread  74  which mates with sealing air fitting bore thread  73  disposed in sealing air fitting bore  72 . In addition, sealing air fitting  71  comprises sealing air fitting valve  76 , by means of which the rate of sealing air flowing into exit chamber  82  may be regulated. Check valve  9  is a one-way valve which permits the flow of sealing air from sealing air supply  10  to sealing air fitting  71 , but not the reverse. 
     An important advance embodied in the instant invention is the provision for preventing dust from settling upon, and impairing the effectiveness of, optical head lenses  92 . Two features embodied in the instant invention join to accomplish this objective. 
     First, sealing air flows from scaling air supply  10  through sealing air lines  11 , check valve  9  and sealing air fitting  71  into exit chamber  82 . Due to the hermetic nature of the fit between optical head  90  and head housing  60 , and between plug  88  and tester aperture  86  (or, when tester  52  is being used, between tester  52  and tester aperture  86 ) the only escape path for sealing air from exit chamber  82  is through exit chamber mouth  83 , mounting tube  46 , and smokestack aperture  17  into smokestack bore  16 , as depicted by mows  44  in FIG.  2  and arrows  15  in FIG.  1 . This constant flow of sealing air out of exit chamber  82  into smokestack bore  16  prevents dust and particulates from entering head housing  60 . 
     Second, trap chamber  80  is disposed between head chamber  78  (wherein optical head lens  92  is disposed) and exit chamber  82 . Any dust or particulate matter which somehow crosses the sealing air barrier in exit chamber  82  and mounting tube  46  will find itself in the still air of trap chamber  80 , and fall to the floor of trap chamber  80  as urged by gravity. 
     Thus the combined effects of sealing air and trap chamber  80  minimize the dust and particulate matter which can settle on optical head lens  92 , thus maximizing the accuracy of the instant smoke density monitor  2 . 
     As may be observed in FIG. 2, smoke density monitor  2  may be calibrated by inserting the tester lens  54  of tester  52  in the optical path between optical head senses  92 , with no smoke  18  or other particulate matter in smokestack bore  16 . Tester  52  is typically equipped with a sealing means such as an O-ring to render its fit with head housing  60  hermetic. 
     Smoke density monitor  2  is installed by attaching mounting tubes  46  to smokestack  12 , attaching transmitter head  4  and receiver head  6  to respective mounting tubes  46 , optically connecting transmitter head  4  and receiver head  6  to density monitor  22 , attaching sealing air supply  10  to sealing air fittings  71  through check valve  9 , and electrically connecting the remaining components. Mounting tubes  46  must be attached to smokestack  12  such that all first bulkhead apertures  65  and second bulkhead apertures  67  are aligned. One way of easily accomplishing this is to insert a close-fitting pipe through the pair of opposing mounting tube bores  48  prior to finalizing the attachment. Sealing air supply  10  may be a stand-alone blower, or simply a take-off from the boiler forced draft fan. 
     Optical heads  90  may be quickly and easily slid off their respective head housings  60  for maintenance, and as easily slid back on again. In the preferred embodiment, optical head lenses  92 , fiber-optic line  8 , density monitor  22 , alarm monitor  34 , alarms  30  and recorder  42  were commercially available components. 
     While a preferred embodiment of the invention has been illustrated herein, it is to be understood that changes and variations may be made by those skilled in the art without departing from the spirit of the appending claims. 
     
       
         
               
             
               
               
             
           
               
                   
               
               
                 DRAWING ITEM INDEX 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 2 
                 smoke density monitor 
               
               
                 4 
                 transmitter head 
               
               
                 6 
                 receiver head 
               
               
                 8 
                 fiber-optic line 
               
               
                 9 
                 check valve 
               
               
                 10 
                 sealing air supply 
               
               
                 11 
                 sealing air line 
               
               
                 12 
                 smokestack 
               
               
                 14 
                 insulation 
               
               
                 15 
                 arrow 
               
               
                 16 
                 smokestack bore 
               
               
                 17 
                 smokestack aperture 
               
               
                 18 
                 smoke 
               
               
                 20 
                 arrow 
               
               
                 22 
                 density monitor 
               
               
                 24 
                 line to alarm monitor 
               
               
                 26 
                 optional line 
               
               
                 28 
                 power supply 
               
               
                 30 
                 line to alarm 
               
               
                 32 
                 alarm 
               
               
                 34 
                 alarm monitor 
               
               
                 36 
                 line to burner 
               
               
                 38 
                 burner 
               
               
                 40 
                 optional line to recorder 
               
               
                 42 
                 recorder 
               
               
                 44 
                 arrow 
               
               
                 46 
                 mounting tube 
               
               
                 47 
                 weld symbol 
               
               
                 48 
                 mounting tube bore 
               
               
                 50 
                 mounting tube thread 
               
               
                 52 
                 tester 
               
               
                 54 
                 tester lens 
               
               
                 60 
                 head housing 
               
               
                 62 
                 head chamber mouth 
               
               
                 64 
                 first bulkhead 
               
               
                 65 
                 first bulkhead aperture 
               
               
                 66 
                 second bulkhead 
               
               
                 67 
                 second bulkhead aperture 
               
               
                 68 
                 head housing thread 
               
               
                 70 
                 O-ring 
               
               
                 71 
                 sealing air fitting 
               
               
                 72 
                 sealing air fitting bore 
               
               
                 73 
                 sealing air fitting bore thread 
               
               
                 74 
                 sealing air fitting thread 
               
               
                 76 
                 sealing air fitting valve 
               
               
                 78 
                 head chamber 
               
               
                 80 
                 trap chamber 
               
               
                 82 
                 exit chamber 
               
               
                 83 
                 exit chamber mouth 
               
               
                 86 
                 tester aperture 
               
               
                 88 
                 plug 
               
               
                 90 
                 optical head 
               
               
                 92 
                 optical head lens 
               
               
                 94 
                 optical head bore 
               
               
                 96 
                 pin 
               
               
                 98 
                 slot