System and method for preventing blow-by of liquefied gases

Abstract

A system and method for preventing blow-by of liquefied gases is disclosed, which senses the occurrence of blow-by and shuts off the source of the liquefied gas. As one example, a system for preventing blow-by of LN2 is disclosed, which includes a temperature sensor located near an exhaust line of a heat exchanger, a shutoff valve located in an inlet line, and a controller coupled to the temperature sensor and the shutoff valve. The sensor measures the temperature of the exhaust, and provides a signal to the controller that indicates if the temperature of the exhaust approaches the temperature of LN2. If the exhaust temperature approaches the temperature of LN2, the controller sends a signal to the shutoff valve, which causes the valve to close and stops the flow of LN2 to the heat exchanger involved. The controller can also send an alarm signal to a display, which indicates to a user that the blow-by is occurring. If the exhaust temperature increases significantly above the temperature of LN2 (e.g., blow-by is no longer occurring), the controller can send a second signal to the shutoff valve, which causes the valve to open and resume the flow of LN2.

1 . A system for preventing blow-by of a liquefied gas, comprising: 
 a containment vessel including an inlet and an outlet, said containment vessel adapted to contain a quantity of a liquefied gas;    a valve coupled between said containment vessel and a portion of said inlet, said valve adapted to block a flow of said liquefied gas into said containment vessel during at least one mode of operation;    a sensor coupled to a portion of said outlet, said sensor adapted to output a signal associated with a current temperature of said portion of said outlet; and    a controller unit coupled to said valve and said sensor, said controller unit adapted to send a control signal to said valve if said current temperature is less than or equal to a predetermined temperature, said control signal associated with said at least one mode of operation.    
   
   
       2 . The system of  claim 1 , wherein said containment vessel comprises a heat exchanger.  
   
   
       3 . The system of  claim 1 , wherein said containment vessel comprises a Dewar.  
   
   
       4 . The system of  claim 1 , wherein said liquefied gas is LN2 .  
   
   
       5 . The system of  claim 1 , wherein said liquefied gas is at least one of liquefied helium and liquefied oxygen.  
   
   
       6 . The system of  claim 1 , wherein said predetermined temperature is associated with a boiling temperature of said liquefied gas.  
   
   
       7 . The system of  claim 1 , wherein said predetermined temperature is substantially 77 Kelvin.  
   
   
       8 . The system of  claim 1 , wherein said predetermined temperature is associated with a substantial decrease of said current temperature during a predetermined period of time.  
   
   
       9 . The system of  claim 1 , wherein said outlet comprises an exhaust for a heat exchanger.  
   
   
       10 . The system of  claim 1 , wherein said outlet comprises a vent.  
   
   
       11 . A system for preventing blow-by of a liquefied gas, comprising: 
 means for containing a quantity of a liquefied gas;    means for blocking a flow of said liquefied gas into said means for containing;    means for releasing said liquefied gas from said means for containing;    means for generating a signal associated with a current temperature of said means for releasing; and    means for receiving said signal and sending a control signal to said means for blocking, if said current temperature is less than or equal to a predetermined temperature.    
   
   
       12 . The system of  claim 11 , wherein said means for containing comprises a heat exchanger.  
   
   
       13 . The system of  claim 11 , wherein said means for containing comprises a Dewar.  
   
   
       14 . A method for preventing blow-by of a liquefied gas, comprising the steps of: 
 enabling a liquefied gas to enter a containment vessel;    enabling a gaseous form of said liquefied gas to exit said containment vessel;    sensing a current temperature of said gaseous form of said liquefied gas; and    blocking said liquefied gas from entering said containment vessel, if said sensed current temperature is less than or equal to a predetermined temperature.    
   
   
       15 . The method of  claim 14 , wherein the blocking step is performed with a shutoff valve.  
   
   
       16 . The method of  claim 14 , wherein the containment vessel comprises a heat exchanger.  
   
   
       17 . The method of  claim 14 , wherein the containment vessel comprises a Dewar.  
   
   
       18 . The method of  claim 14 , further comprising the step of: 
 unblocking said liquefied gas from entering said containment vessel, if said sensed current temperature is substantially higher than said predetermined temperature.    
   
   
       19 . A computer program product, comprising: 
 a computer-usable medium having computer-readable code embodied therein for configuring a computer processor, the computer program product comprising:    a first executable computer-readable code configured to cause a computer processor to enable a liquefied gas to enter a containment vessel;    a second executable computer-readable code configured to cause a computer processor to enable a gaseous form of said liquefied gas to exit said containment vessel;    a third executable computer-readable code configured to cause a computer processor to sense a current temperature of said gaseous form of said liquefied gas; and    a fourth executable computer-readable code configured to cause a computer processor to block said liquefied gas from entering said containment vessel, if said sensed current temperature is less than or equal to a predetermined temperature.    
   
   
       20 . The computer program product of  claim 19 , further comprising: 
 a fifth executable computer-readable code configured to cause a computer processor to unblock said liquefied gas from entering said containment vessel, if said sensed current temperature is substantially higher than said predetermined temperature.