Patent Abstract:
A sensor system for monitoring cryogenic gas flow through a tube/pipe has at least one sensor coupled to the tube/piping. An alarm circuit is coupled to the sensor for receiving measurement signals from the at least one sensor and for sending an alarm signal when the measurement signal deviates from a predetermined level.

Full Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates generally to an alarm system and, more specifically, to a non-intrusive ammonia flow alarm system which will signal when ammonia gas is flowing through a designated pipe. 
   2. Description of the Prior Art 
   Ammonia is a hazardous material which is normally a gas at room temperature and pressure. Ammonia is often transported in pipes in a liquid phase. Ammonia is generally transported from a gas cylinder through one or more pipes to a desired location. The ammonia is maintained in a liquid form by virtue of the pumping pressure. The ammonia gas may be used in a variety of different applications. For example, the ammonia gas may be used in the production of fertilizer, in a refrigeration process, and the like. 
   On certain size ammonia canisters, a release valve is required. The release valve is necessary to relieve pressure from the ammonia canister. The release valve is generally coupled to a pipeline and further to a diffusion tank which will capture the released ammonia gas. 
   When the ammonia gas is released through the released valve, it generally indicates that there is a problem with the ammonia cannister or the release valve. Thus, one needs to check the ammonia cannister and the release valve to see if there is a potential problem. For example, the release valve may have malfunctioned and is leaking ammonia. Unfortunately, most ammonia sensors are extremely expensive to install. Furthermore, these sensors generally have to be installed when the ammonia system is being constructed. Present ammonia sensors cannot easily be retrofitted onto an existing system due to the invasive nature of the retrofit. 
   Therefore, a need existed to provide an improved ammonia flow detection system. The improved ammonia flow detection system must overcome the problems associated with prior art systems. The improved ammonia flow detection system must be inexpensive and easy to install. The improved ammonia flow detection system must further be able to be retrofitted onto existing systems preferably in a non-invasive way. 
   SUMMARY OF THE INVENTION 
   In accordance with one embodiment of the present invention, it is an object of the present invention to provide an improved ammonia flow detection system. 
   It is another object of the present invention to provide an improved ammonia flow detection system that is able to overcome the problems associated with prior art gas flow detection systems. 
   It is still another object of the present invention to provide an improved ammonia flow detection system that is inexpensive and easy to install. 
   It is yet another object of the present invention to provide an improved ammonia flow detection system that is able to be retrofitted onto existing systems preferably in a non-invasive way. 
   BRIEF DESCRIPTION OF THE EMBODIMENTS 
   In accordance with one embodiment of the present invention, a sensor system for monitoring cryogenic gas flow through a tube/pipe is disclosed. The sensor system has at least one sensor coupled to the tube/piping. An alarm circuit is coupled to the sensor for receiving measurement signals from the at least one sensor and for sending an alarm signal when the measurement signal deviates from a predetermined level. 
   In accordance with another embodiment of the present invention, a sensor system for monitoring cryogenic gas flow through a tube/pipe is disclosed. The sensor system has at least one cryogenic gas flow sensor coupled to an exterior surface of a tube/pipe where the cryogenic gas will flow. The cryogenic gas flow sensor is used for measuring a temperature of the tube/pipe where the cryogenic gas will flow. A reference sensor is coupled to an empty tube/pipe where the cryogenic gas will not flow. The reference sensor is used for measuring a temperature of the empty tube/pipe. An alarm circuit is coupled to the sensors for receiving measurement signals from the sensors and for sending an alarm signal when the measurement signal deviates from a predetermined level. The alarm circuit has a plurality of input terminals wherein at least one input terminal is coupled to the at least one cryogenic gas flow sensor and wherein a second input terminal is coupled to a reference sensor. A comparator circuit is coupled to the plurality of input terminals for comparing an input signal of the at least one cryogenic gas flow sensor and an input signal of the reference sensor and for sending an output alarm signal when the difference between the input signal of the at least one cryogenic gas flow sensor and the input signal of the reference sensor deviates from a predetermined level. 
   The foregoing and other objects, features, and advantages of the invention will be apparent from the following, more particular, description of the preferred embodiments of the invention, as illustrated in the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, as well as a preferred mode of use, and advantages thereof, will best be understood by reference to the following detailed description of illustrated embodiments when read in conjunction with the accompanying drawings. 
       FIG. 1  is a simplified block diagram of the flow alarm system of the present invention. 
       FIG. 2A  is one embodiment of the sensor used in the flow alarm system of the present invention. 
       FIG. 2B  is another embodiment of the sensor used in the flow alarm system of the present invention. 
       FIG. 2C  is another embodiment of the sensor used in the flow alarm system of the present invention. 
       FIG. 3  is a simplified functional block diagram of the alarm circuitry used in the flow alarm system of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIG. 1 , a cryogenic gas flow alarm system  10  (hereinafter system  10 ) is shown. The system  10  is used to detect the flow of cryogenic gases, such as ammonia, through piping of various sizes. The system  10  can be used to monitor the flow of different types of cryogenic gases. For example, the system  10  may be used to monitor the flow of liquid natural gas, liquid nitrogen, liquid oxygen, liquid propane, liquid ethylene, liquid propylene, liquid ammonia, and the like. The listing of the above should not be seen as to limit the scope of the present invention. The system  10  may be used to monitor the flow of any type of cryogenic gas. 
   The system  10  will have one or more sensors  12 . The sensors  12  are coupled to the exterior of a pipe  14 . The sensors  12  are used to measure the temperature of one or more pipes  14 . When a cryogenic gas flows through the pipe  14 , the temperature of the pipe  14  will drop. The sensor  12  can monitor the drop in temperature. The sensors  12  may be any one of numerous types of sensors. Any sensor  12  that is able to monitor a temperature may be used. For example, the sensor  12  may be a thermocouple, resistance temperature detectors (RTDs), thermistors, infra-red sensors, IC temperature sensors, molecular temperature switches, acoustic flow sensors, vibration flow sensors, ultrasonic flow sensors, fiber optic sensors, electrochemical sensors, and the like. The listing of the above sensors  12  should in no way be seen as to limit the scope of the present invention. 
   The sensor  12  is coupled to an alarm circuitry  16 . The alarm circuitry  16  will monitor the temperature signals from the sensor  12 . When the temperature drops below a predetermined temperature, the alarm circuitry  16  will sound off an alarm. 
   In order to prevent false alarm signals, a reference sensor  18  may be used. The reference sensor  18  may measure the air temperature or may be coupled to a reference pipe  20 . The reference pipe  20  would generally be an empty pipe in which no cryogenic gas will flow. The reference sensor  18  is also coupled to the alarm circuitry  16 . The alarm circuitry  16  can compare the temperature of the reference sensor  18  to that of the sensors  12  which are directly coupled to the exterior of the pipes  14 . If the temperature difference between the reference sensor  18  and one of the sensors  12  deviates from a predetermined level, then the alarm circuitry  16  will signal an alarm. 
   Referring now to  FIG. 2A , one embodiment of the sensor  12  is shown. In this embodiment, the sensor  12  is a thermocouple sensor  12  which is coupled to the exterior of the pipe  14  with a clamping mechanism  22 . The clamping mechanism  22  is similar to a hose clamp. The clamping mechanism  22  has a circular body member  22 A. An opening is formed in the circular body member  22 A. The opening is where a top section of the sensor  12  is inserted. The sensor  12  will thus be in contact with the pipe  14  when the clamping mechanism  22  is placed around the pipe  14  and tightened. The clamping mechanism  22  will have a locking member  22 B coupled to the circular body member  22 A. The locking member  22 B will allow one to tighten the clamping mechanism  22  around the pipe  14 . 
   In the embodiment depicted in  FIG. 2A , the sensor  12  has a flexible membrane  24 . The flexible membrane  24  will allow the sensor  14  to be better coupled to the pipe  14  and to allow the sensor  14  to adapt to the different conditions. 
     FIGS. 2B–2D  show several different embodiments for the sensor  12  and the clamping mechanism  22 . As shown in  FIG. 2B , the sensor  12  may be directly coupled to the pipe  14 . Some type of adhesive may be used to directly couple the sensor  12  to the pipe  14 . Any type of adhesive ma be used as long as the adhesive does not interfere with the ability of the sensor  12  to monitor the temperature of the pipe  14 . As may be seen in  FIG. 2C , the sensor  12  may be wrapped around the pipe  14 . In the embodiment no type of clamping mechanism  22  or adhesive is required. The sensor  12  is wrapped around the pipe  14  and the wires from the sensor  12  are then coupled to the alarm circuitry  16  holding the sensor in place. It should be noted that in order to increase the accuracy of the ability of the sensor  12  to monitor the temperature of the pipe  14 , a gel may be used. The gel will help form a better connection between the sensor  12  and the pipe  14  thus leading to better readings. 
   Referring to  FIG. 3 , one embodiment of the alarm circuitry  16  is shown. The alarm circuitry  16  will have a plurality of input terminals  26 . The input terminals  26  are used to couple the one or more sensors  12  and the reference sensor  18 , if one is used) to the alarm circuitry  16 . The input signals are then sent through a differential amplifier  28 . The differential amplifier  28  will amplify the voltage difference between the input signals. The output from the differential amplifier  28  will then be sent to one or more comparators  30 . Each comparator  30  is coupled to an output terminal  32 . When the signal from the differential amplifier  28  deviates from a predetermined level, the comparator will send a signal to the output terminal  32 . Each comparator  30  is coupled to a set-point adjustment  34 . The set-point adjustment  34  will allow one to set the level at which the comparator  30  will send a signal to the output terminal  32 . The output terminals  32  may be coupled to any type of alarm mechanism. For example, the output terminal may be coupled to an audible alarm (speaker system) or a visual alarm (lights). The output terminal  32  may further be coupled to a transmitter which will send a wireless communication to a remote device to indicate that the system  10  has monitored a cryogenic gas flow. The output terminals  32  may further be coupled to a relay switch. The relay switch may be used to shut down the cryogenic gas flow from the problem cannister. 
   While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.

Technology Classification (CPC): 6