Cathodic protection system for underground storage tank

Abstract

There is provided a method for implementing a cathodic protection system for an underground storage tank. A DC voltage source provides a test current between the installed anode and storage tank resulting in the flow of electrical current. If the output is above a defined value, an automatic control DC power supply has sufficient voltage capacity to deliver the required current. If the anode test currents fall below the required minimum current, additional anode(s) are installed as set forth in a pre-engineered table. The method allows for the installation of a cathodic protection system by technicians and other non-experts.

1 . A system for impressing current for cathodic protection of a metallic structure comprising: 
 a constant current DC power supply having a positive and a negative terminal, wherein said constant current DC power supply contains means for receiving AC current;    at least one anode, wherein said anode is electronically connected to the positive terminal of the DC power supply;    an associated metallic structure, wherein said associated metallic structure is electronically connected to the negative terminal of the DC power supply; and    a current output monitoring system.    
   
   
       2 . The system of  claim 1 , further comprising a sensor indicating when current output is at target amperes and a meter or recorder for displaying the time the system has operated at the correct current.  
   
   
       3 . The system of  claim 1 , further comprising an anode wire junction box configured to allow interruptions of the current output to facilitate the taking of instant potential measurements in accordance with established national guidelines.  
   
   
       4 . The system of  claim 1 , further comprising a cathodic protection monitoring tube disposed a fixed distance from the metallic structure.  
   
   
       5 . The system of  claim 1 , wherein the power supply is energized by wind, solar, fuel cell or oil power.  
   
   
       6 . A method for providing cathodic protection to an associated metallic structure comprising: 
 providing a power supply with a positive terminal and a negative terminal;    installing at least a first anode a first specified distance from the structure;    electrically connecting the positive terminal of the power supply to the first anode;    electrically connecting the negative terminal of the power supply to the associated metallic structure;    measuring the current (A 1 ) flowing between the metallic structure and the negative terminal of said power supply;    determining the appropriate number of additional anodes needed to provide adequate cathodic protection to said metallic structure via reference to a standardized system.    
   
   
       7 . The method of  claim 6 , wherein the power supply is a DC voltage source.  
   
   
       8 . The method of  claim 7 , wherein the DC voltage source is a 12 V battery.  
   
   
       9 . The method of  claim 7 , wherein the power supply provides a constant current at a level which is at least twice the maximum current required to cathodically protect the associated metallic structure.  
   
   
       10 . The method of  claim 6 , further comprising the step of first confirming the metallic structure is not leaking.  
   
   
       11 . The method of  claim 6 , further comprising the step of providing the power supply with a current output monitoring system.  
   
   
       12 . The method of  claim 11 , wherein the current output monitoring system further comprises an element recording or displaying the time of operation at the target current output.  
   
   
       13 . The method of  claim 6 , wherein the first specified distance between the anode and the metallic structure is from 5 to 8 feet.  
   
   
       14 . The method of  claim 6 , wherein the power supply is energized by wind, solar, fuel cell or oil power.  
   
   
       15 . The method of  claim 6 , further comprising the step of providing an anode wire junction box configured to allow interruptions of the current output to facilitate the taking of instant-off potential measurements in accordance with established national guidelines.  
   
   
       16 . The method of  claim 6 , wherein said standardized system is a chart or other reference correlating the number of anodes required based on the current measured.  
   
   
       17 . The method of  claim 16 , wherein the number of additional anodes needed for a 500-550 gallon underground storage tank is determined by reference to the following chart:  
     
       
         
               
               
               
             
                   
                   
               
                   
                   
               
                   
                 A 1   
                 # additional Anodes Needed 
               
                   
                   
               
                   
                 >0.100 amperes 
                 1 
               
                   
                 0.060 < A 1  < 0.100 
                 2 
               
                   
                 0.040 < A 1  < 0.060 
                 3 
               
                   
                 <0.040 
                 Additional cathodic protection needed 
               
                   
                   
               
                   
                   
               
           
              
              
              
              
             
             
              
              
              
              
              
              
             
          
         
       
     
   
   
       18 . The method of  claim 16 , wherein the number of additional anodes needed for a 1000-1100 gallon underground storage tank is determined by reference to the following chart:  
     
       
         
               
               
               
             
                   
                   
               
                   
                   
               
                   
                 A 1   
                 # Anodes Needed 
               
                   
                   
               
                   
                 >0.160 amperes 
                 2 
               
                   
                 0.120 < A 1  < 0.160 
                 3 
               
                   
                 0.090 < A 1  < 0.120 
                 4 
               
                   
                 <0.090 
                 Additional cathodic protection needed 
               
                   
                   
               
                   
                   
               
           
              
              
              
              
             
             
              
              
              
              
              
              
             
          
         
       
     
   
   
       19 . The method of  claim 6 , further comprising forming a cathodic protection monitoring tube adjacent said metallic structure.  
   
   
       20 . The method of  claim 6 , wherein the power supply further comprises a rectifier to automatically increase or decrease a voltage of said power supply based on differences in circuit resistance.