Patent Publication Number: US-6216719-B1

Title: Safety system for transfer of pressurized fluids

Description:
This is a continuation of Ser. No. 08/868,375 filed on Jun. 3, 1997 now U.S. Pat. No. 5,921,266. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is directed to a safety system for transfer of pressurized fluids. In particular, the present invention is directed to an automatic shutoff system for transfer of pressurized fluids from a cargo tank vehicle to a storage container through a delivery hose. 
     2. Prior Art 
     Pressurized fluids, such as compressed liquid gases, are utilized in a variety of applications. Liquified compressed gases include carbon dioxide (CO 2 ), butane (C 4 H 10 ), anhydrous ammonia (NH 3 ), and propane(C 3 H 8 ). Propane and butane (known commercially as LP gas or LPG) have an extremely wide range of domestic, industrial, and agricultural uses. Among the uses are appliance fuel, industrial and utility furnaces, industrial heating processes such as heat treating and metal cutting, and vehicle fuel. Liquified compressed gases generally are those which become liquids in containers at ordinary temperatures at pressures from 25 to 2500 psig. As an example, the pressure of liquid propane at 70° F. (21.1° C.) is approximately 110-125 psig (756.4 KiloPascal KPa). 
     Liquified compressed gases are categorized as hazardous materials. Those who transport compressed gases must comply with a variety of government safety regulations in the United States, Canada and other countries throughout the world. Liquified compressed gases are shipped under rules that limit the maximum amount that can be put into a container to allow space for liquid expansion. For example, in the United States, a cargo tank (defined as a tank permanently attached to or forming a part of a motor vehicle) selected for transporting a specific compressed gas must be a container authorized for that S product and the container must be qualified with Department of Transportation (DOT) regulations. These regulations are contained in Title 49 of the Code of Federal Regulations, Parts 100 to 199. 
     Additionally, with flammable gases, it is necessary to guard against the possibility of fire or explosion. For example, when liquid propane is released into the atmosphere, it quickly vaporizes into its normal non-pressurized gaseous form. The propane combines rapidly with air to form fuel-air mixtures which are ignitable over a range of 2.2 to 9.5% by volume. 
     In the liquified compressed gas industry, transportation between the producer and the consumer is important. In many instances, the producer and consumer are separated by considerable distances. Large quantities of compressed gas must be transported over long distances by safe and economical methods. Liquified compressed gases are often transported in special tank cars, motor trucks, boat and train facilities. 
     For example, the propane industry in the U.S. transports between 7 and 10 billion gallons annually in highway transport vehicles to storage sites. The same volume is transported again from storage sites in local delivery bobtail trucks to storage containers. 
     Cargo tank motor vehicles have been developed to transfer liquified compressed gases. Two basic types are well known. Cargo tank motor vehicles known as “highway transports” are large cargo tanks mounted on semi trailers pulled by a highway truck tractor. A typical transport may carry 9000-16000 gallons of liquid. Cargo tanks must comply with DOT Specification MC-330 or MC-331. Smaller cargo tank motor vehicles, known as “bobtails”, are cargo tanks mounted directly on a vehicle chassis. A bobtail may carry up to 5000 gallons of liquid. 
     In each type, a pump on the vehicle is powered by the vehicle engine, meaning that the engine must remain on during unloading. 
     In the case of highway transports, liquified compressed gas is transferred from the highway transport to a storage container by means of a hose. A pump is mounted on the highway transport to move the liquified gas from the cargo tank, through the hose and into the storage container. A pump valve is located on the highway transport between the cargo tank and the pump. The pump valve may be operated manually by the operator or may have an automatic feature that will close the valve in the event of a drop in the pressure. 
     In the case of bobtails, liquified compressed gas is transferred from the bobtail storage tank to a storage container by means of a hose. 
     Notwithstanding the foregoing, the existing vehicle belly valve may not be automatically activated in the event of a rupture, a severing or uncoupling of the hose. Most recently, the U.S. Department of Transportation has announced proposed rules and interim rules relating to emergency discharge control systems on cargo tanks (see, for example, 49 CFR §178). 
     For these reasons, there still remains a need for an automatic safety shutoff system in the event of a rupture, severing or uncoupling of a delivery hose between a cargo tank vehicle and a storage container. 
     It is, therefore, a principal object and purpose of the present invention to provide an automatic safety shut off system in the event of a rupture, severing, or uncoupling of a delivery hose between a cargo tank vehicle and a storage container. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to the transfer of pressurized fluid between a cargo tank vehicle and a storage container. A cargo tank vehicle includes a cargo tank to store pressurized fluids, such as liquid propane. An engine not only powers the vehicle but includes a power take off that will power a pump or compressor. A belly valve mounted on the vehicle is in fluid communication with the cargo tank and in fluid communication with the pump. The belly valve includes a normally closed moveable butterfly plate. When the valve is closed, no pressurized fluid can pass between the cargo tank and the pump. 
     Outflow from the pump is connected to a delivery hose. The delivery hose has a first end in fluid communication with the pump and its coupling. The delivery hose also has a second end in fluid communication with the storage container. Near the hose second end, a hose coupling includes an opening therethrough to which will be attached a small pressure hose in fluid communication with the pressurized fluid. The pressure hose leads back to a first pressure sensor which can detect a drop in pressure and de-energize a set of electrical contacts. The first pressure sensor is connected to a first switch. The first switch will activate or deactivate a supply solenoid and supply valve and a bleed solenoid and bleed valve. The supply and bleed valves are in line with the air pressure system of the vehicle which operates the belly valve. 
     Near the hose first end, in fluid communication with the pump, the coupling includes an opening to which will be attached a small pressure hose in fluid communication with the pressurized fluid in the delivery hose. The pressure hose leads back to a second pressure sensor which can detect a drop in pressure and de-energize a set of electrical contacts. The second sensor is, in turn, connected to a second switch. The second switch will activate or deactive the supply and bleed solenoids and valves. 
     A further, additional mechanical safety mechanism may be employed. Accompanying and attached to the delivery hose is a thin, steel cable. The cable may be attached at periodic intervals to the delivery hose or, alternatively, may be formed integrally with the delivery hose. The cable has a first end . terminating in a pin receivable in a switch receptacle on the control box. The switch receptacle is likewise wired to the supply and bleed valves. When the pin is retracted or disengaged, the belly valve will be closed. The cable has a second end which is connected to an eyelet attached to the storage container. A rupture, severing, or uncoupling of the delivery hose will cause deflection of the hose. Deflection of the delivery hose will cause the pin to retract or become disengaged from the switch receptacle. Accordingly, the supply and bleed valves will cause the belly valve to close, preventing additional pressurized fluid from escaping from the storage tank of the vehicle. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a typical bobtail cargo tank vehicle connected to a storage tank for delivery of compressed fluid prior to introduction of the present invention; 
     FIG. 2 is a diagrammatic representation of the present system for transfer of pressurized fluid from a cargo tank vehicle to a storage container in use with a highway transport vehicle; 
     FIG. 3 is an alternate embodiment of a system for transfer of pressurized fluid from a cargo tank vehicle to a storage container in use with a highway transport vehicle; 
     FIG. 4 is a further, alternate embodiment of a system for transfer of pressurized fluid from a cargo tank vehicle to a storage container in use with a bobtail cargo tank vehicle; 
     FIG. 5 is a simplified flow chart showing the various steps for transfer of pressurized fluid from a cargo tank vehicle to a storage container; and 
     FIG. 6 is a simplified circuit diagram of the electrical circuit of the present system for transfer of pressurized fluid. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention may be employed in various applications of transportation and delivery of pressurized fluids. In the present embodiments, delivery of compressed gas will be described in two particular applications. Both apply to distribution of compressed propane although the teachings of the invention may be used in many other applications. In the first application, liquid propane is transported in a highway transport vehicle and transferred from the highway transport vehicle to a storage container at a storage facility that is a distribution point. In the second application, the liquid propane is transported in a bobtail cargo vehicle and transferred from a bobtail cargo vehicle to a storage container or drum, such as found at a residential location. 
     It will be understood that although the invention is described in connection with transferring fluid from a cargo tank vehicle to a storage container, it will function to transfer fluid in the reverse direction. 
     Referring to the drawings in detail, FIG. 1 illustrates a prior art system of transferring compressed gas from a bobtail cargo vehicle to a storage container. A bobtail cargo tank vehicle  10  is shown with a cargo tank  12  mounted on the chassis  14  of the vehicle. The cargo tank is built to store pressurized gases such as liquid propane. The bobtail vehicle  10  includes an engine  16  that not only powers the vehicle but also a power take off (not visible in FIG. 1) that will power a pump  18  or a compressor. The engine  16  also powers an air pressure system to be described in detail herein. 
     A hose  30  has a first end in fluid communication with the outflow from the pump  18 . Controls for the pump may be located at a control station  32 . During transportation, the hose  30  is wound up and stored in the control station  32 . A normally closed belly valve  20  mounted on the vehicle is juxtaposed between the pump and cargo tank. 
     The delivery hose  30  terminates at a second end in a hose end coupling  40  that will be connected to a storage tank  42  through a tank coupling  44 . The hose end coupling  40  includes a spring loaded valve to keep the hose in a normally closed position. The tank coupling  44  has threads to attach to threads on a handle assembly  46  of the hose end coupling  40 . A lever  48  will open the normally closed coupling to allow transfer of fluid. After transfer, the pressurized fluid is stored in the storage tank  42  or drum for usage. The storage tank  42  includes various regulators and control valves (not shown), all as well known. 
     The configuration of a highway transport vehicle would be similar to the bobtail cargo tank vehicle  10  shown in FIG. 1, all of which have been in existence prior to the introduction of the present invention. 
     FIGS. 2,  3 , and  4  show three alternate embodiments of the present invention for transferring pressurized fluid. FIG. 2 illustrates one embodiment for use with a highway transport vehicle. A belly valve  50  is mounted on the semi-trailer body and in fluid communication with a tank  52  of a highway transport vehicle through opening  54 . 
     The belly valve  50  is, in turn, in fluid communication with a pump  56  or compressor. Various types of liquid pumps or compressors may be utilized. The belly valve  50  may take many forms although a typical butterfly valve is shown in the embodiments of FIGS. 2,  3 , and  4 . 
     The normally closed butterfly valve has a movable plate  58 . When the belly valve  50  is closed, no pressurized fluid can pass from the cargo tank  52  to the pump  56 . Conversely, when the belly valve  50  is open, pressurized fluid can flow from the cargo tank  52  to the pump  56 . 
     As seen by the box marked “PTO”, the pump  56  is driven by the power take off  60  from the vehicle engine (not visible). The vehicle engine must, thus, be on for the pump  56  to operate. 
     The direction of fluid flow in to the pump  56  from the belly valve  50  is indicated by arrow  62 . The direction of fluid flow out of the pump  56  is indicated by arrow  64 . 
     The outflow from the pump  56  is connected to a coupling  70  which, in turn, is connected to a delivery hose  72 . When the transport vehicle arrives at the site of a storage container  74 , the delivery hose  72  will be connected between the pump  56  and storage container  74 . The delivery hose  72  has a first end  82  in fluid communication with the pump  56  and its coupling  70 . The delivery hose  72  also has a second end  84  in fluid communication with the storage container  74 . The storage tank  74  includes a riser  76  and a threaded coupling  78 . 
     Near the hose second end  84 , a hose coupling  86  includes an opening therethrough to which will be attached a small, quarter inch pressure hose  88  that is in fluid communication with the pressurized fluid in. the delivery hose  72 . When pressurized fluid fills the delivery hose, it will also enter the pressure hose  88 . The pressure hose  88  leads back to a first pressure sensor  90  which can detect a drop in pressure and de-energize a set of electrical contacts. The first pressure sensor is configured to convert fluid pressure into an electrical signal. In the present embodiment, the pressure sensor is an electromechanical pressure transducer although other types of pressure sensors are possible within the teachings of the invention. 
     The first pressure sensor  90  is, in turn, connected to a control box  92 . The control box  92  will be wired to the electrical system of the vehicle to supply voltage through wires  80  and mounted in a location readily accessible to the operator. A first switch is activated by the first pressure sensor  90 . 
     The first switch will activate or deactivate a supply solenoid  94  and supply valve  96  and a bleed solenoid  98  and bleed valve  100 . The control box  92  and the supply solenoid  94  and bleed solenoid  98  are connected by electric lines  102  and  104 , respectively. 
     An air pressure system illustrated by box  110  is powered by the engine of the transport vehicle. Typically, the existing air pressure system of the vehicle used for the vehicle air brakes will be used. The engine fills a compressed air tank (not shown) which is in communication with a cylinder  112  through air line  118 . 
     The air pressure system  110  includes a switch (not shown) that may be activated by the operator to open the belly valve  50 . The vehicle, as presently required by regulation, also includes emergency manually operated switches in at least two vehicle locations—forward and aft—to shut down the air pressure system in an emergency. These are illustrated at boxes  114  and  116 . In the event the operator detects a problem, either emergency switch  114  or  116  may be thrown to close the belly valve  50 . These are separate from the automatic shut-off system of the present invention and can not override it. 
     When the supply solenoid  94  opens the supply valve  96  and the bleed solenoid  98  closes the bleed valve  100 , the cylinder  112  will open the plate  58  of the belly valve  50 . Accordingly, compressed fluid will flow from the cargo tank  52  through the belly valve  50 , into the pump  56  and thereafter into delivery hose  72 . While the pump will force fluid into the delivery hose, it will be understood that the compressed nature of the fluid will cause the fluid to quickly pressurize the delivery hose. 
     In the event of a drop in pressure, the first switch will close the supply valve  96  and open the bleed valve  100 , so that cylinder  112  will allow the belly valve  50  to close. 
     Near the hose first end  82 , in fluid communication with the pump  56 , the coupling  70  includes an opening to which will be attached a small, quarter inch pressure hose  120  in fluid communication with the pressurized fluid in the delivery hose  72 . The pressure hose  120  leads back to a second pressure sensor  122  which can detect a drop in pressure and de-energize a set of electrical contacts. The second pressure sensor  122  is, in turn, connected to the control box  92 . Control box  92  includes a second switch which is activated by voltage from the second pressure sensor  122 . 
     The second switch will activate or deactivate the supply solenoid  94  and supply valve  96  and bleed solenoid  98  and bleed valve  100 . It will be appreciated that either the first switch or second switch is capable of closing the belly valve  50 . 
     The embodiment in FIG. 2 includes an additional mechanical safety system. Accompanying and attached to the delivery hose  72  is a thin, steel cable  130 . The cable  130  may be attached to the delivery hose every 6 to 8 inches or, alternatively, may be formed integrally with the hose. The cable  130  has a first end  132  terminating in a pin  134  which is receivable in a switch receptacle on the control box  92 . The switch receptacle is likewise wired to the supply valve  96  and bleed valve  100 . When the pin  134  is retracted, as seen in dashed lines  136 , the belly valve will be closed. The cable  130  has a second end  140 . The cable second end  140  will be connected to an eyelet  142 . In the event of a rupture of the delivery hose, of severing of the hose  72 , or of disconnection of the delivery hose from one of the couplings, the pressurized fluid will quickly escape. It has been found that pressurized fluid escaping from the delivery hose  72  will cause deflection of the delivery hose. 
     Deflection of the delivery hose  72  will cause the pin  134  to retract or disengage from the switch receptacle. Accordingly, the supply and bleed valves  94  and  98  will cause the cylinder to move the plate  58 . The belly valve will close, preventing additional pressurized fluid from escaping from the storage tank on the vehicle. 
     FIG. 3 is an alternate embodiment of the present invention for transfer of compressed fluid from a transport cargo tank  146  to a storage container  148 . A belly valve  150  is in fluid communication with a pump  152 . The butterfly valve is normally closed with a movable plate  154 . The pump  152  or compressor is driven by power take off  144  of the vehicle engine. 
     The direction of fluid flow from the belly valve  150  in to the pump  152  is illustrated by arrow  166 . The direction of fluid flow out of the pump is indicated by arrow  168 . 
     The outflow from the pump  152  is connected to a coupling  156  which is, in turn, connected to a delivery hose  158 . The delivery hose  158  has a first end  160  in fluid communication with the pump and its coupling  156 . The delivery hose  158  also has a second end  162  in fluid communication with the storage container  148 . Near the hose second end  162 , a coupling  164  includes an opening therethrough in which is inserted a first pressure sensor (not visible in FIG. 3) which can detect a drop in pressure and de-energize a set of electrical contacts. 
     The first pressure sensor is, in turn, connected to a radio transmitter  170  which generates a radio signal. The radio signal is received by a radio receiver (illustrated by antenna  172 ) which will receive the radio signal. It is believed that a low level, close range transmittable radio frequency would be suitable. The radio receiver must recognize an identifiable signal from the transmitter. It is contemplated that the pressure switch will not transmit until the pressure sensor gives it a voltage signal. The radio receiver generates a voltage which is wired to a first switch in a control box  168  which will activate or deactivate a supply solenoid  174  and supply valve  176  along with a bleed solenoid  178  and bleed valve  180 . The control box is wired to the supply and bleed solenoids through wires  207  and  209 . 
     An air pressure system, as illustrated at box  182 , is powered by the engine of the transport vehicle. Existing manually operated shut-down switches  184  and  186  will shut off air pressure in the system  182  and return the belly valve  152  to the normally closed position. These are separate from the automatic shut-off system and can not override it. 
     The supply and bleed valves will work together with a cylinder  188  to open the plate  154  of the belly valve. Accordingly, once the belly valve  152  is open, compressed fluid will flow from the tank  146  through the belly valve  150 , through the pump  152  and into the delivery hose  158 . 
     Near the hose first end  160 , in fluid communication with the pump  152 , the coupling  156  includes an opening to which is attached a small, quarter inch pressure hose  190  in fluid communication with the pressurized fluid in the delivery hose. Pressure hose  190  leads back to a second pressure sensor  192  which can detect a drop in pressure and de-energize a set of electrical contacts. The second pressure sensor  192  is, in turn, wired to the control box  168 . A second switch is activated by the second pressure sensor  192 . The second switch will activate or deactivate the supply solenoid  174  and bleed solenoid  178 . Wires  207  and  209  connect the supply and bleed solenoids to the control box. 
     It will be appreciated that either the first switch or the second switch is capable of closing the belly valve  150  so that a drop in pressure at either location will prevent additional flow of fluid. 
     The embodiment in FIG. 3 also includes the additional mechanical safety system. Accompanying and attached to the delivery hose  158  is a thin, steel cable  196 . The cable  196  may be attached to the delivery hose every 6 to 8 inches or, alternatively, may be formed integrally with the hose. The cable  196  has a first end  198  terminating in a pin  200  which is receivable in a switch receptacle on the control box  168 . The switch receptacle is likewise wired to the supply and bleed valves  176  and  180  through the supply solenoid  174  and bleed solenoid  178 . 
     Thus, when the pin  200  is retracted or disengaged, as seen in dashed lines  202 , the belly valve  150  will be caused to close. Cable  196  also has a second end  204  which will be hooked to an eyelet  206  on a riser  208  of the storage tank  148 . In the event of a rupture of the delivery hose, a severing of the hose, or disconnection of the delivery hose from one of the couplings, pressurized fluid will quickly escape and cause deflection of the delivery hose. Deflection of the delivery hose  158  will cause the pin  200  to retract or become disengaged from the switch receptacle. The switch receptacle is likewise wired to the supply solenoid  176  and the bleed solenoid  178 . Thereafter, the supply and bleed valves will cause the cylinder to move and the belly valve to close, preventing any additional pressurized fluid from escaping from the cargo tank on the vehicle. 
     FIG. 4 is a third, alternate embodiment of the present invention. The FIG. 4 embodiment would be used in conjunction with a bobtail cargo tank vehicle  10  shown in the FIG. 1 prior art rendering. 
     A belly valve  20  is in fluid communication with a cargo tank  12  of a bobtail vehicle through opening  210 . The belly valve  20  is, in turn, in fluid communication with an inlet of a pump  18 . The butterfly valve  20  is normally closed with a moveable plate  212 . When the belly valve  20  is closed, no pressurized fluid can pass from the cargo tank  12  to the pump  18 . As seen by the box marked “PTO”, the pump  18  is driven by a power take off  214  from the vehicle engine. 
     The direction of fluid flow from the belly valve  20  to the pump is illustrated by arrow  266 . The direction of fluid flow out of the pump is illustrated by arrows  268 . 
     The outflow or discharge from the pump  18  is connected to a coupling  216  which is, in turn, connected to a delivery hose  218 . When the bobtail cargo vehicle arrives at the site of a storage container  42 , a delivery hose  218  will be connected between the pump  18  and the storage container  42 . 
     The delivery hose  218  has a first end  220  in fluid communication with the pump  18  and its coupling  216 . The delivery hose  218  also has a second end  222  in fluid communication with the storage container  42  through coupling  40 . 
     Near the hose second end  222 , hose coupling  224  includes an opening therethrough to which will be attached a pressure sensor (not visible) which can detect a drop in pressure and activate a transmitter. The pressure sensor is wired to a radio transmitter  226  which generates a radio signal. The radio signal is received by a radio receiver (illustrated by antenna  228 ). The radio receiver converts the acceptable signal to operate a control circuit in a control box  230 . The control box  230  is wired to a supply solenoid  232  and supply valve  234  along with a bleed solenoid  236  and bleed valve  238  by wires  240  and  242 . 
     As in the previously described embodiments, near the hose first end  220 , the coupling  216  includes an opening to which will be attached a small, quarter inch pressure hose  260  in fluid communication with the pressurized fluid in the delivery hose  218 . The pressure hose leads back to a second pressure sensor  262  which can detect a drop in pressure and de-energize a set of electrical contacts. 
     FIG. 5 is a flow chart illustrating the steps used in the safety system of the present invention. The actual unloading operation may vary slightly depending on the design of the particular cargo tank vehicle. The flow chart is particularly applicable to the embodiment shown in FIG. 2 with a highway transport although its general teachings will apply to the other embodiments as well. 
     With the vehicle engine running and the air pressure system of the vehicle in operation, the vehicle air brakes are set as shown at box  244 . The delivery hose will be attached between the pump  56  and the storage container  74  as depicted by box  246 . Thereafter, the cable  130  will be attached at both ends, the one end secured to the eyelet  142  on the riser  76  and the other end, which terminates in a pin  134 , will be inserted into the receptacle in the control box  92 , as shown by box  248 . Unless the pin assembly is fully seated, the control box will not be powered. 
     The control box itself may have an on-off switch to supply voltage to the circuit from the vehicle electrical system (not shown). This step is illustrated at box  250 . 
     The operator will manually push a start button on the control box (shown in FIG. 3 as button  230 ) which will permit voltage to flow to the control box, as depicted by box  252 . 
     This will energize the supply and bleed solenoids  94  and  98  to close the bleed valve and open the supply valve in the air pressure system  110 . The start button  230  is connected to a six (6) second timer to energize the first and second switches (as shown at box  254 ). By doing so, the belly valve will open (as shown at box  256 ), allowing compressed fluid to pass through the belly valve and through the pump into the delivery hose. As long as both pressure sensors verify pressure in the delivery hose at both ends (see boxes  258  and  260 ), the pump will be permitted to operate and the belly valve will remain open. 
     In the event either of the pressure sensors detects a drop in pressure, the control circuit causes the solenoids to automatically close the belly valve. 
     FIG. 6 is a simplified electrical circuit diagram showing the first and second switches and their relationship with the solenoids for the embodiment shown in FIG.  2 . 
     Whereas, the present invention has been described in relation to the drawings attached hereto, it should be understood that other and further modifications, apart from those shown or suggested herein, may be made within the spirit and scope of this invention.