Enhanced vapor containment and monitoring

Abstract

An apparatus and method for ensuring effective and efficient vehicle vapor recovery performance, storage tank system integrity relative to both vapor and liquid containment and for reducing the probability that inaccurate information causes companies to undertake unnecessary, expensive and wasteful loss investigations at gasoline dispensing facilities. A fuel storage and delivery system is transformed from an “open system” communicating directly with the environment to a “closed system” which ensures capture, containment and accurate accounting of both hydrocarbon vapors and liquid phase product.

1 - 2 . (canceled)  
   
   
       3 . A method for conducting a vapor containment test, comprising: 
 identifying the start of an idle dispensing period, when no liquid is transferred from a storage tank to a receiving tank;    as long as the idle dispensing period continues, 
 measuring storage tank pressure in the ullage space to provide a storage  
   tank pressure measurement associated with a point in time (P tank, t); 
 measuring atmospheric pressure at the same point in time (P atm, t);  
 determining the variation of storage tank pressure and atmospheric pressure during the idle period by comparing measurements of storage tank pressure and atmospheric pressure for different times;  
   in response to detecting that the idle dispensing period is complete, generating a pressure versus time curve based on the monitored variations; and    determining the acceptability of vapor containment in the ullage space of the facility to test vapor containment by reference to the generated pressure versus time profile.    
   
   
       4 . The method of  claim 3 , further comprising comparing a standard deviation of storage tank pressure with a standard deviation of atmospheric pressure, (P tank−P atm), if said standard deviation is below a threshold, and the average of (P tank−P atmosphere) is below a threshold, indicating that the storage tank system is leaky.  
   
   
       5 . The method of  claim 3 , further comprising: 
 comparing a sum of atmospheric pressure and storage tank pressure (P atm+P tank) at various time intervals chosen to avoid the impact of temperature variation; and    if sums of (P atm+P tank) are not constant over the chosen time interval, indicating that the storage tank system is leaky.    
   
   
       6 . A method for directly calculating a vapor growth rate in a storage tank system, comprising: 
 identifying the ullage tank volume (Vullage0) at the beginning of a time period (t0), said period including both idle and active dispensing activity;    measuring the atmospheric pressure (P atm0);    measuring the ullage tank pressure (P tank0);    calculating a volume of vapor occupying the ullage volume (Vullage0) at the beginning of the period, (V0), by the relationship V0=(P tank0+Patm0)/P atm0×Vullage0 at t0;    identifying the ullage volume at the end of the time period (Vullage1, t1), said period including idle and active dispensing activity;    measuring the atmospheric pressure at the end of the period (P atm1, t1);    measuring the ullage tank pressure at the end of the period (P tank1, t1);    calculating a volume of vapor occupying the ullage volume at the end of the period (V1) by the relationship V1=(P tank1+Patm1)/P atm1×Vullage1 at t1; and    determining a volume growth rate (VGR) by the relationship VGR=(V1−V0)/delta t, where delta t is the difference between t1 and t0.    
   
   
       7 . A method for estimating the vapor growth rate in a storage tank system, comprising; 
 identifying the average dispensing rate within a given time interval (D);    measuring the atmospheric pressure at the beginning of the time interval (P atm0, t0);    measuring the ullage tank pressure at the beginning of the time interval (P tank0, t0);    assuming at least one or a range of ullage volume values (Vullage0) between 0 and the total storage tank system capacity;    measuring the atmospheric pressure at the end of the time interval (P atm1, t1); measuring the storage tank pressure at the end of the time interval (P tank1, t1); for each assumed initial ullage volume, calculate a ullage volume at the end of the interval by the relationship Vullage1=Vullage0+(D×delta t), where delta t is the difference between t1 and t0; and    for each pair of beginning and ending ullage volume values, calculate a vapor growth rate (VGR) according the following relationships:    V0=(P tank0+P atm0)/P atm0×V ullage0, where Vullage0 is the assumed ullage volume at time t0;    V1=(P tank1+P atm1)/P atm1×(Vullage1), where Delta V=V1−V0 and delta t=t1−t 0; and    VGR=(V1−V0)/(t1−t0).    
   
   
       8 . The method according to  claim 7 , further comprising indicating that leaks may be present when VGR is less than a predetermined threshold of expected VGR.  
   
   
       9 . The method according to  claim 7 , further comprising indicating that other anomalies may be present when VGR is greater than a predetermined threshold of expected VGR.  
   
   
       10 . The method according to  claim 7 , further comprising indicating that a change in system dynamics may have occurred when VGR is greater than a predetermined threshold of expected VGR.  
   
   
       11 . A method for monitoring the ullage space, comprising: 
 recording values of storage tank pressure versus time at regularly spaced time intervals at a facility;    determining a pressure profile signature developed for a specific gasoline dispensing facility relative to the history of storage tank pressure versus time for the facility;    observing variations from the pressure profile signature; and    indicating the presence of anomalies at the dispensing facility in response to said observed variations.    
   
   
       12 . The method of  claim 11 , further comprising identifying anomalies which trigger closer physical inspection of potential leak sources in response to said observed variations.  
   
   
       13 . The method of  claim 11 , further comprising identifying hardware operating problems in response to said observed variations;  
   
   
       14 . The method of  claim 11 , further comprising identifying anomalies which trigger predetermined safety measures if measured values fall outside of a given threshold value, thus providing an immediate response for corrective action to anomalies.  
   
   
       15 . The method of  claim 11 , further comprising identifying anomalies which trigger remote alert notification if measured values fall outside of a given threshold value, thus providing an immediate response for corrective action to anomalies.