Abstract:
Each barge in a group of river-going tanker barges, has a double-hull construction to protect the inner hull and avoid collision-induced cargo spills. The space between hulls is partitioned to individual empty, dry compartments with a vertical, open bottomed, measuring tube fixed in each. A closed-bottom master tube is fixed in one compartment. All tubes have a quick-connect, above-deck, flange to receive an ultrasonic transducer thereon. A hand-held measuring instrument containing a computer and controls and information display contains a transducer which is selectively pulsed to periodically send ultrasonic signals down the tube, and receive echo signals, with elapsed time representing the depth of a signal reflector surface which is the master tube bottom or, for the measuring tubes, the bottom of a dry compartment or the surface of liquid in a leaking compartment. A unique bar code with each tube, distinguishes it and the barge from all others. The measuring instrument includes a code reader. In one embodiment, an individual transducer is on each tube, and connectable by an electrical cable to the measuring instrument. The apparatus is also used in cargo compartment tanks for cargo surface level measurement.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to containers for liquids, and more particularly to methods and apparatus for detection of liquid levels of liquids that have either leaked into space between the outer hull and inner hull of a double-hulled ship or barge or the like or are purposefully pumped into a tank. 
     2. Description of the Prior Art 
     Modern tanker ships and barges are being designed and built with space between the outer hull and an inner hull in an effort to avoid puncture of cargo tanks, and thereby avoid leakage of liquid contents from cargo tanks into a waterway as a result of collision damage. Instead of there being a single void space around the entire inner hull, there are partitions so as to divide the space into a plurality of compartments so that, in the event of a puncture of the outer hull, only a compartment space can be flooded while the remaining compartments remain dry. Also, in the event of a leak developing at some point in the wall of the inner hull, such leakage will only enter the compartment between hulls and not leak out into the waterway if the outer hull is not damaged at the site of that compartment. 
     In order to be sure that there is no leakage into a compartment from either the waterway or a cargo tank inside the vessel, it is desirable to be able to detect the presence of liquid in a compartment. Heretofore, that has not been easy. First of all, the compartments are usually sealed so as to avoid entry of water or other liquid from the top, as from a deck, for example. Therefore, if presence of liquid in such compartment is to be detected, it has been necessary to provide a hole in the deck and insert a pole through the hole to the bottom of the compartment, and then raise the pole to see if there is any liquid on the lower end of the pole. Considering the fact that such compartments may be as deep as twelve feet on a river barge, and much deeper on an ocean tanker, the handling of such a measuring pole is not easy. Also, it is time consuming. 
     It is an object of the present invention to facilitate determination of the presence and depth of liquid in a normally void space in a shipping vessel. 
     Furthermore, when filling tanks with expensive or dangerous compounds it is desirable to prevent overflow of the liquid. 
     Thus it is a further object of the present invention to protect against overfills in tanks by determining when a liquid has reached a predetermined critical level. 
     SUMMARY OF THE INVENTION 
     Described briefly, according to a typical embodiment of the present invention as implemented in a double-hulled, river-going barge, each of the void space compartments is provided with a permanently installed tube extending from the deck down to a point near the bottom of the compartment. The tube is adapted at its top for normally receiving a quick-connect sealing closure. The tube has an opening at or near the bottom end of it. Therefore, any liquid collecting in the compartment can rise inside the tube, particularly if a vent opening in the tube wall near the top of the compartment permits any air in the tube to escape as liquid rises in it. 
     A measuring instrument is provided with a quick-connect coupling readily receivable and mating with the coupling at the top of each tube after the tube closure has been removed. The measuring instrument includes a transceiver including a transducer selectively operable to transmit ultrasonic energy pulses down the tube, and receive reflected ultrasonic energy pulses. The elapsed time is measured and compared to a master, to calculate the depth of liquid, if any, in the compartment. The calculated depth is displayed on an indicator and, if more than a predetermined acceptable limit, will also illuminate a light or energize a sounder to indicate an alarm condition. The master time/depth information is obtained from a tube which is like those in the compartments except that it has a closed bottom end at a known distance from the transducer when mounted to it, to establish a reference dimension. 
     Each tube has a bar code identification including two components, one of them being a barge identification and the other being the compartment identification on the barge. The measuring instrument has a bar code reader on it to identify the particular barge and compartment along with the depth indication reading. Information regarding the readings at the various compartments on a barge can be stored in the measuring instrument and subsequently downloaded to a separate computer. 
     According to one method of use of the apparatus, an individual can walk the barge from end-to-end up one side and down the other. In a preferred mode, the operator will stop at the master tube first and obtain information relating to the master tube length to automatically establish a time factor for the passage of sound in atmosphere at the typical temperature of the compartments in the barge and thereby obtain a reference time useful in subsequent locations on the barge to directly compute and indicate the depth of liquid, if any, in a compartment. In this context, the term “sound” is used, but should not be construed to be limited to an energy wave frequency range that can be heard by humans. 
     Following calibration of the instrument at the master tube, the operator then moves from that tube to the first compartment measurement tube, connects the instrument, activates the instrument and notes the result. This is done in sequence from one compartment to the next. If, at any compartment, the instrument detects a liquid depth greater than a predetermined acceptable maximum, the alarm condition will be announced not only through the display, but also with some other annunciator such as light, bell, buzzer, or combination thereof. Then the operator knows that a pump is needed to pump that compartment. Once that has been done, check of the other remaining compartments can be performed. 
     As an alternative approach, the operator can move from compartment-to-compartment on one barge and then on another barge in a string of barges and, either simultaneously through a radio link, or subsequently through a direct wire download, can transmit that information including bar code identification and the depth measurement for each compartment to a computer which then applies the correct sound-velocity-in-air correction factor (UE) to the signals received for each compartment and computes the depth of liquid, if any, in each compartment and, on a printout, flags each compartment for which there is an alarm condition present, the proper UE factor for each barge being predetermined by the master tube measurement for that barge, wherever it occurs in the sequence of tubes checked. There is also provision for ascertaining or assuring that all measurements are made within a reasonable time from the time of measurement of the master tube so that all measurements are representative of essentially the same compartment temperature conditions for a given barge. 
     In a related application, the invention can be used to provide overfill protection for cargo holds in tankers, or other fluid containers such as railroad tank cars, for example. In such an application, the relative location of the critical fluid level of interest would presumably be nearer the top of the container, but the measuring device could be very similar to the one for the void space leakage detection application. After detecting that the fluid level had exceeded a predetermined level, the pump can be stopped, thereby preventing overfilling of the tank. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic top plan view of a string of barges having an apparatus therein according to the present invention. 
     FIG. 2 is a schematic side elevational view of a barge thereof. 
     FIG. 3 is a schematic vertical section through a void space compartment showing a master tube, a measuring tube, and an access port and some unwanted liquid in the compartment. 
     FIG. 4 is an enlarged fragmentary vertical section through a measurement assembly including the measuring instrument with built-in transducer and a side-mounted bar code reader, all together, mounted on the top of one of the measuring tubes. 
     FIG. 5 is an enlarged section similar to FIG. 4 but wherein a transducer is permanently mounted to the top of the measurement tube and has a lid on it for protection of the transducer, but the lid is readily removable for electrically coupling the measuring instrument to the transducer. 
     FIG. 6 is an enlarged fragmentary vertical section similar to FIG. 4 but of an alternative embodiment showing measuring tube, lid, and mounting assembly. 
     FIG. 7 is a view of the embodiment depicted in FIG. 6 with the lid lifted in preparation for coupling with the measuring instrument. 
     FIG. 8 is a view of the embodiment depicted in FIG. 7 with the measuring instrument coupled to the tube opening. 
     FIG. 9 is a view of the measuring instrument of FIG.  8 . 
     FIG. 10 is a schematic vertical sectional view through a cargo tank in a barge and showing a master tube and a measuring tube applied in an overfill protection mode. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated instrument, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates. 
     Referring now to the drawings in detail, FIG. 1 is a schematic top plan view of a string of river barges  11  connected together as in a tow. Each of these has a double-walled hull with six void space compartments such as  12 ,  13 ,  14 ,  16 ,  17  and  18  on each side of the hull between the outer hull  19  and inner hull  21 . The inner hull has a plurality of cargo carrying tanks such as  22  therein. Each of the six compartments at each side of the hull has a measuring tube according to a typical embodiment of the present invention. Several of such tubes are designated by the reference numerals  23 ,  24  and  26 , for example. Also, at each end of the barge there is a master tube such as  27  at one end of the first barge in the string and  28  at the opposite end on the other side of the same barge. Each of the compartments is separated from the next adjacent compartment by a wall such as  12 W between compartments  12  and  13 . Compartment  12  has the master tube  27  therein and the measuring tube  23 . Compartment  18  has master tube  28  therein like master tube  27 , and measuring tubes  29  and  30  like measuring tubes  23 ,  24  and  26  and the others in the other void space compartments in this barge. Where the compartments are approximately twelve feet deep in a barge, the measuring tube and master tube will be approximately twelve feet long to the top of the deck  31 . 
     Referring now to FIG. 3, the bottom of the hull is shown at  32  and the master tube and measuring tubes  27  and  23 , respectively, are shown installed in compartment  12 . These tubes are welded to the deck  31  and are identical except that tube  27  has a plug  33  in the bottom of it, to keep liquid in the tank compartment  12  from entering it. Each of these tubes has a quick-connect mounting flange such as  34  above the deck and near the top  36  of the tube. There is also a bar-code display plate  37  welded to the tube immediately below the flange  34 . Although the mounting flange  34  and top and other features of the tubes are identical, the bar code plate  38  on tube  23  is different only in the respect that the bar code  39  on it is different from the bar code  41  on plate  37 . The reason for this is the fact that the bar codes must identify not only the barge on which the tubes are mounted, but also the particular compartment on which each measuring tube such as  23  is mounted. The code must also distinguish the master tube from the measuring tubes. The bar code can be embossed, molded, or engraved on the plate itself. Or it can be on stickers, decals or some other medium permanently mounted to the plate with protective coating or covering for endurance. An access hatch  42  is provided on deck  31  for access to compartment  12 . Liquid is shown in the compartment as indicated by the liquid surface indicator line  43 . Of course, it is desirable that there be no liquid in these compartments, from either the waterway in which the vessel is floating, or from any of the cargo tanks inside the vessel. 
     Referring now to FIG. 4, the measuring instrument  46  is shown mounted to the flange  34  of a measuring tube  23 . This is accomplished by a coupling  47  which, in this instance, is affixed to the bottom of the electronic box of the measuring instrument and is mounted in a quick-connect fashion on the quick-connect flange  34 . It is important that this mounting be such that, when the instrument is mounted on the tube, it be oriented correctly so that the bar code reader  48  be correctly oriented with respect to the bar code mount plate  38  to illuminate and read the code thereon. A half-turn from mounting to lock of the instrument on flange  34 , is an example. The instrument  46  has a transducer therein which, when activated by pushing one of the buttons, such as  49  for a master tube reading, or  51  for a measuring tube reading, will transmit pulses of ultrasonic frequency at an established pulse rate down the tube  23  in the direction of arrow  52  for reflection back to the transducer from either the bottom  32  of the compartment or from the surface of liquid in the tube or, in the case of the master, from the plug  33  at the bottom of the master tube. The transducer will respond to reflected energy, and appropriate calculations are made. 
     In the case of the master tube, for which button  49  is pushed, the distance from the transducer in the instrument  46  to the top of the plug  33  when the instrument is secured to flange  34 , is already known, 132 inches, for example. Therefore, the computer in the instrument  46  can respond to the elapsed time from the transmission of a pulse-by the transducer to the reception of the echo by the transducer, to compute the UE factor corresponding to the temperature of the air in the master tube in compartment  12 . This factor will be used for the depth calculations for the measurements on the measuring tube  23  in this compartment and for the measuring tubes in the rest of the compartments of this barge. This can be done because, for purposes of this invention, in a given barge, all compartments can be assumed to be at about the same temperature, and the depth of all compartments is essentially the same, and all tubes are the same. Therefore, once the master tube information is known, and the UE factor is calculated and stored in the computer, it will be applied uniformly to all of the information obtained from all of the measuring tubes for that barge. With the transducer to echo reflector distance calculated from the temperature-adjusted elapsed time information, and with the barge identification information stored in the computer, the computer can calculate the depth from the vessel bottom to the surface from which the echo is reflected. The computer can be pre-programmed for each barge, with an acceptable depth limit for the particular barge stored in the measuring instrument computer along with the bar code identification for that barge. The person who specifies an acceptable depth, considers the fact that there may always be a certain amount of water in the void space compartments due to condensation, for example. During check of a compartment, the computer announces the measured depth by a digital display in the window  53 . It is further programmed to announce an alarm condition by lamp  68  and buzzer  69  if the measured depth exceeds the acceptable limit stored in the computer. It will be evident from the foregoing and following description of the invention, that the measuring instrument is intended to be hand-held, and include a variety of electronics including, but not limited to, a computer, a controller including control components and circuitry, data storage, a display and, possibly, depending on space and weight considerations, a printer. The computer to accomplish the functions, need not be a general purpose computer. It can be a special purpose computer of a rudimentary nature, considering today&#39;state of the art, and can be readily housed in the hand-held instrument  46 . Similarly, the power supplies, transducer, above-mentioned and other components in the instrument, can be conventional and are well within the skill of the art and need not be described in any detail herein. 
     Following the measurement at either the master tube or any of the measuring tubes, the instrument is removed by, for example, a half turn on the mounting flange  34 , and the protective cover and seal cap  56  is replaced on the flange  34 . 
     In the FIG. 5 embodiment, the arrangement is slightly different in that, although the instrument  46  still has its own transducer, a transducer assembly  57  is permanently mounting on the quick-connect flange  34  of each tube on a barge. It can be removed, if desired. It includes the diaphragm  58  and associated energizing wires  59  and  61  with associated pin sockets in recess  62  covered by the seal cap  63 . In this embodiment, when a measurement is to be made, the measuring instrument need not be mounted to the transducer. Instead, the cap  63  may be snapped off the top of the transducer, and a plug  65  connected by a cable  65 C to the measuring instrument  46 , is installed in socket  62  to activate the transducer diaphragm  58  when button  51  is pushed. After a predetermined time delay, the transducer responds to the echo intercepted by the transducer diaphragm. In this case, the cable can be one connected permanently to the instrument  46  to provide this option, when desired, or it can have a plug at the end opposite plug  65  and which is removably connected to the socket  66  on the instrument, as shown, so the cable can be stored elsewhere when not needed. In the use of the system of FIG. 5, it is still necessary that the code reader function be performed, so the instrument must be held where the code can be read or, the code reader  48  can be unclipped from the clip  48 A on the side of the instrument  46  and, being coupled to the instrument by the cable  48 B, the reader can be used as a wand to read the code. Another terminal socket  64  on the instrument is provided for downloading data stored in the instrument to a separate computer if, and when, desired. 
     In the embodiment depicted in FIGS. 6-9, variations on the tube installation and coupling device configuration are illustrated for a measuring tube. Instead of being directly welded to the deck, tube  23  is supported by an assembly  60  which is easily installed and adjusted, allowing the tube to be replaced if necessary. In this arrangement, collar  71 , screwed onto sleeve  73 , causes wedge ring  72  to engage the chamfered surface  74  of sleeve  73  and clamp the collar and sleeve to the tube. Sleeve  73  is threadedly attached to housing  80 . Once assembled, the tube and housing assembly can be brought to the installation site which is prepared by providing hole  101  in the deck  31  and welding the support flange  70  around hole  101 . Tube  23  is then inserted into hole  101 , and housing  80  is secured in place by fasteners, one of which is shown at bolt  84  and nut  85 . 
     The tube cover and coupling device are also varied in this embodiment as bolt  84  also secures the base  81  of lid mounting bracket  82  to the top of housing  80 . A pair of horizontally spaced rails  82 R, upstanding from base  81 , receives hinge pin  83  which passes through the horizontally-spaced, downwardly extending side guards  125  of lid  91  and connects lid  91  to housing  80 . Lid  91  includes stopper  92  and side guards  125  to prevent external liquid from entering tube  23 . Lid  91  further includes bar code plate  38  to provide information about the tube  23  as described previously. Thus to measure fluid depth, lid  91  is lifted using handle  90  as depicted in FIG.  7 . Lifting lid  91  simultaneously removes stopper  92  from the socket  110  of sleeve  73  and exposes bar code plate  38 . The quick connect coupling in this embodiment comprises plug  115  on measuring instrument  120  which fits snugly inside socket  110  atop tube  23  as depicted in FIG.  8 . The entire apparatus is arranged such that with lid  91  substantially vertical and measuring instrument  120  inserted into socket  110 , bar code reader  48  is substantially aligned with bar code  39  as illustrated by line  121  (FIG.  8 ). Measuring is performed substantially the same as described in previous embodiments and, when complete, lid  91  is lowered covering socket  110 . 
     Some additional description of the procedure and sequence is appropriate here. In either of the embodiments depicted in FIGS. 4 to  9  and, after the measuring instrument is coupled mechanically or electrically to the tube, the appropriate button is pushed. It is preferable that the master tube at either end of the barge be addressed first, to set up the instrument for immediate annunciation of an alarm condition if excessive liquid depth is detected in any of the measuring tubes on the barge. The transducer pulse rate is established so that the echo can be received by the transducer from the reflecting plug  33  during the period between the times of transmission of pulses from the transducer. The computer relates the time between a transmitted pulse and the reflected echo pulse with the known distance between the transducer and the plug top, to establish the present actual velocity of sound in the air in the tube. The computer stores the corresponding UE value and, simultaneously, using this value, presents the master tube dimension, such as 132 inches, for example, on the display  53 . All of this occurs while the “MASTER” button  49  is pressed. The same sort of function occurs when the instrument is coupled to a measuring tube and the “READ” button  51  is pressed. But in this case, instead of displaying the distance from the transducer to the liquid surface, (which could easily be done, if desired) the computer uses the stored information regarding the barge compartment depth, to directly display the depth of liquid, if any, in the compartment. 
     As examples, an ultrasonic pulse transmitter having a pulse frequency capability of 25,000 Hz (cycles per second) to 100,000 Hz may be used. A desirable frequency may be 50,000 Hz. The pulse repetition rate can be in a range from 0.02 to 6,000 cycles per minute. A desirable rate may be 600 cycles per minute. If desired, the measuring instrument can be equipped with means to enable the user to adjust the pulse frequency and the pulse repetition rate. 
     The sequence of events in the actual measurement process is summarized as follows: 
     1. Disable receiver. 
     2. Transmit pulse at time t 1 . 
     3. Enable receiver and receive echo pulse at time t 2 . 
     4. Using the known transducer to plug distance, d 1 , calculate the multiplication (UE) factor to be multiplied to the elapsed time t 2 −t 1  to equal the known distance d 1 . 
     5. Store UE. 
     6. Repeat steps 1-3 on a measuring tube. 
     7. Multiply the stored UE by the elapsed time. 
     8. Convert the result of step 7 to depth of liquid below the echo reflecting surface. 
     9. Display the depth and, if alarm condition, activate warning light and sounder. 
     It should be recognized that, by the use of the code system for identifying not only the compartments on a barge, but also the barges in a string, each compartment has a unique identification. Therefore, a person checking compartments on a string of barges could walk from one barge to another, from one end of the string to the other end, along the port side, and then back down the starboard side to the starting point, visiting the master on each barge and all the measuring tubes on all the barges. At each tube, the depth information can be stored immediately in the computer. Then all of the information can be downloaded into a separate computer at the dock or other location, and a printed record made, with bullets or other flags shown adjacent the record for any compartment that is in alarm condition. If for some reason, some measuring tubes on a barge would be addressed by the inspector before addressing the master tube on the barge, alarm conditions would not necessarily be accurately indicated until the master tube is addressed, to then correct the elapsed time (t 2 −t 1 ) by the UE factor for each tube. After the master tube is used to calibrate the measuring instrument computer processing for a given barge, and the necessary multiplication factor is stored in the instrument computer for that particular barge, depth information can be calculated and stored and printed for all void space compartments on the barge, regardless of whether the master is addressed before, somewhere between, or after the measuring tubes for the various compartments are addressed. If the desired accuracy of depth determination is not so great that correction for temperature is necessary, it would not be necessary to check the master tube each time that barge compartments are checked. But, as indicated above, good consistent practice is to address the master tube before addressing the rest of the measuring tubes on a barge. If precision is desired, the computer can be further programmed to require that all measurements for a given barge be taken within a specific period of time. 
     Until now embodiments adapted to detect the presence of liquid in void space compartments of vessels have been particularly discussed. Another embodiment of the invention relates to overfill protection for cargo compartments/tanks. In overfill protection applications, as shown in FIG. 10 for a typical cargo tank  22  in the barge, both master tube  27 F and measuring tube  23 F are shorter to detect a critical liquid level that is near the top of the tank. In this case, plug  33 F sealed in the bottom of tube  27 F has its top surface at the level of the desired maximum or critical level  45 T for liquid  45  in the tank. This level can be as near the top of the tank as desired, and the master tube plugged accordingly. In the illustration, there is expansion space allowed over the top of the liquid. The measurement tube is open at the bottom as are the measurement tubes in the other embodiments. The measurement tube extends down to a level below the level of the top of the plug in the master tube. Optimally it extends to a level enough below the plug level to be certain to provide overfill protection. Actual use of the overfill protection aspect of the invention is similar to the usage in detecting the presence of unwanted liquid in void space compartments. Additional features can be employed such as activating an alarm in either application of the invention, or automatically shutting off a fill pump in the overfill protection application once a critical liquid level is detected. By using the bar code identification for the material contained in the tank, and an appropriate data base in the computer with expansion coefficients in it for the contained material, and with the master tube plug  33 F at the optimum location to accommodate the variety of materials which may be contained in the cargo tank, activation of the alarm, or pump shutoff, may be adapted by the computer to the material contained, so that adequate expansion space will be assured. In some instances, due to environmental protection requirements, governmental regulations do not permit discharge to atmosphere of the air or vapors above the liquid surface in a tank. Where the Contents of the tank are of a nature such that discharge of vapor is prohibited, an open-bottom measuring tube may not be permitted. In those cases, a measuring tube with closed bottom, external float and internal float follower and signal reflector, may be used. Such construction is disclosed in my co-pending application executed on Jul. 23, 1997 and filed Jul. 24, 1997 and entitled “Liquid Level Indicator for Storage Tank (later issued May 26, 1999, U.S. Pat. No. 5,900,546). The disclosure of that application is hereby incorporated herein by reference. It will be recognized that the present invention in its various forms may be useful in void space compartments or cargo compartments in vessels for transportation on land or water. It may also be used for stationary vessels. 
     Three examples of identification (ID) numbers (#) of a container, such as a barge, ship, railroad tank car or tank in a tank farm, are: 
     Examples of Container ID # 
     ACBL1034 
     IB1099 
     IB970 
     Examples of three tanks within a barge are: 
     Examples of Tank # 
     1P 
     2S 
     6P 
     Examples of Master Indicator 
     0 Not a mastering location 
     1 Mastering location 
     Examples of Master Depth in Inches: 
     008 
     084 
     144 
     156 
     Examples of Tank Depth in Inches: 
     020 
     120 
     142 
     An example of the barcode convention is as follows: 
     
       
         
               
             
               
               
               
               
               
               
             
           
               
                   
               
               
                 20 Characters Total 
               
             
          
           
               
                 Container 
                   
                 Master 
                 Master 
                 Tank 
                 Not 
               
               
                 ID # 
                 Tank 
                 Ind. 
                 Depth MD 
                 Depth 
                 Used 
               
               
                   
               
               
                 XXXXXXXX 
                 XX 
                 X 
                 XXX 
                 XXX 
                 XXX 
               
               
                 (8 characters) 
                 (2 
                 (1 
                 (3 
                 (3 
                 (3 
               
               
                   
                 chtrs.) 
                 chtrs.) 
                 characters) 
                 chrts.) 
                 chrts.) 
               
               
                   
               
             
          
         
       
     
     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.