Process and device for monitoring leakage from a radiant tube fired by a gas burner

Abstract

A process and a device for monitoring the imperviousness of a radiant tube fired by a gas burner is disclosed. From a burner control a burner signal is derived that may have at least the states BURNER OFF when the burner is switched off and BURNER ON when the burner is switched on. In addition, the exhaust gas flow of the burner is monitored and an exhaust gas signal is derived there from which may at least have the states EXHAUST GAS OFF when there is no sufficient volume flow of exhaust gas flowing out of the radiant tube, and EXHAUST GAS ON when there is a correctly flowing exhaust gas. The burner signal and the exhaust gas signal are linked with each other for outputting a failure signal in case the combination BURNER ON and EXHAUST GAS OFF results.

What is claimed is:  
     
         1 . A process for monitoring leakage from a radiant tube fired by a gas burner, comprising the steps of: 
 controlling an on/off state of the burner for generating a burner signal comprising at least the states BURNER OFF and BURNER ON, the state BURNER ON being indicative for a switched on burner and the state BURNER OFF being indicative for a switched off burner;    monitoring an exhaust gas flow exiting from the burner and generating an exhaust gas signal comprising at least the states EXHAUST GAS OFF and EXHAUST GAS ON, the state EXHAUST GAS OFF being indicative for an exhaust volume gas flow falling below a certain threshold, the state EXHAUST GAS ON being indicative for an exhaust gas volume exceeding said threshold, said monitoring being performed by monitoring a pressure differential occurring between an input and, an output side of a flow constriction arranged within the flow to be monitored;    comparing each detected combination of said burner and said exhaust gas signals to a set of allowed combinations; and    generating a failure signal, if any of said detected combinations of said burner and said exhaust gas signals deviates from said set of allowed combinations.    
     
     
         2 . A process for monitoring leakage from a radiant tube fired by a gas burner, comprising the steps of: 
 controlling an on/off state of the burner for generating a burner signal comprising at least the states BURNER OFF and BURNER ON, the state BURNER ON being indicative for a switched on burner and the state BURNER OFF being indicative for a switched off burner;    monitoring an exhaust gas flow exiting from the burner and generating an exhaust gas signal comprising at least the states EXHAUST GAS OFF and EXHAUST GAS ON, the state EXHAUST GAS OFF being indicative for an exhaust volume gas flow falling below a certain threshold, the state EXHAUST GAS ON being indicative for an exhaust gas volume exceeding said threshold;    comparing each detected combination of said burner and said exhaust gas signals to a set of allowed combinations; and    generating a failure signal, if any of said detected combinations of said burner and said exhaust gas signals deviates from said set of allowed combinations.    
     
     
         3 . The process of  claim 2 , wherein said burner signal is derived from a control controlling an operation of said burner.  
     
     
         4 . The process of  claim 2 , wherein a failure signal is generated, if the signals BURNER ON and EXHAUST GAS OFF are detected.  
     
     
         5 . The process of  claim 2 , further comprising a feeding of a certain flow of coolant air to said radiant tube for cooling a furnace room heated by said radiant tube, wherein said process further comprises the following steps: 
 monitoring said flow of said coolant air for generating a coolant air signal, said coolant air signal comprising at least the states COOLANT AIR ON and COOLANT AIR OFF, the state COOLANT AIR ON being indicative for a flow of coolant air being above a certain threshold value, the state COOLANT AIR OFF being indicative for a coolant air flow being below a certain threshold value;    comparing each combination of said coolant air signal and said burner signal with a set of allowed combinations; and    generating a failure signal, if any of said combinations of said burner and said exhaust gas signals deviates from said set of allowed combinations.    
     
     
         6 . The process of  claim 5 , wherein additional coolant air for cooling said furnace room is fed to said radiant tube, wherein said process further comprises the following steps: 
 monitoring said flow of additional coolant air for generating an additional coolant air signal, said additional coolant air signal comprising at least the states ADDITIONAL COOLANT AIR ON and ADDITIONAL COOLANT AIR OFF, the state ADDITIONAL COOLANT AIR ON being indicative for a flow of additional coolant air being above a certain threshold value, the state ADDITIONAL COOLANT AIR OFF being indicative for an additional coolant air flow being below a certain threshold value;    comparing each combination of said coolant air signal, said additional coolant air signal, and said burner signal with a set of allowed combinations; and    generating a failure signal, if any of said combinations of said coolant air signal, said additional coolant air signal, and said burner signal deviates from said set of allowed combinations.    
     
     
         7 . The process of  claim 2 , wherein said monitoring of said flow is performed by a method selected from the group formed by volumetric measuring, pressure measuring, differential pressure measuring and flow velocity measuring.  
     
     
         8 . The process of  claim 2 , wherein a failure signal is generated in case a combination BURNER OFF and EXHAUST GAS ON is detected.  
     
     
         9 . A device for monitoring leakage from a radiant tube fired by a gas burner, said device comprising: 
 a burner control device generating a burner signal comprising at least the states BURNER OFF and BURNER ON, the state BURNER ON being indicative for a switched on burner and the state BURNER OFF being indicative for a switched off burner;    a flow monitoring device for monitoring an exhaust gas flow emerging from said burner and for generating an exhaust gas signal, said exhaust gas signal comprising at least the states EXHAUST GAS ON and EXHAUST GAS OFF, the state EXHAUST GAS OFF being indicative for said exhaust gas flow falling below a certain threshold, the state EXHAUST GAS ON being indicative for said exhaust gas flow exceeding said threshold; and    a monitoring circuitry connected to said burner control device and said flow monitoring device for receiving said burner signal and said exhaust gas signal, said monitoring circuitry being configured for comparing each detected combination of said exhaust gas and said burner signals with a set of allowable combinations and for generating a failure signal, if any of said detected combinations deviates from said set of allowable combinations.    
     
     
         10 . The device of  claim 9 , wherein said flow monitoring device is selected from the group formed by a volumetric measuring device, a pressure measuring device, a differential pressure measuring device and a flow velocity measuring device.  
     
     
         11 . The device of  claim 10 , wherein said radiant tube comprises an outlet through which said exhaust gas emerges, and wherein a flow restriction having an input side and an output side is connected with its input side to said outlet, wherein said monitoring device further comprises a differential pressure detector for measuring the pressure differential between said input and said output sides of said flow restriction.  
     
     
         12 . The device of  claim 10 , wherein said monitoring circuitry is configured for generating a failure signal upon detecting a combination of said burner and exhaust gas signals comprising the states BURNER ON and EXHAUST GAS OFF.