Method and apparatus for detecting leakage in fuel storage and delivery systems

A method of detecting leakage from a liquid fuel product line through which the fuel is pumped from a storage tank to a dispenser, said method comprising the steps of:

• monitoring the pressure in the product line;
• relieving the pressure in the product line to a predetermined level whenever the pressure therein is above said level and fuel is not being pumped into the product line;
• effecting sequential pressurization cycles each including pumping fuel into the product line to raise the pressure therein above said predetermined level when the pressure in the product line drops to a lower level;
• measuring the time required during each cycle for the pressure in the product line to drop from said predetermined level to said lower level;
• and
• providing a leak indication whenever the time measured during any cycle exceeds the time measured during the immediately preceding cycle by less than a predetermined amount.

A method of detecting the presence of an amount of gas in excess of an established permissible amount in a system containing liquid which is pressurized, said method comprising the steps of:

• applying pressure to the system to raise the pressure therein to a high level;
• relieving the pressure in the system to a predetermined low level less than said high level;
• measuring the time required for the pressure relief to effect dropping of the pressure in the system from said high level to said low level;
• and
• providing an indication of an amount of gas in the system in excess of said established permissible amount if the time that is measured exceeds a preselected value.

A method of detecting the presence of air in excess of an established permissible amount in an automotive fuel product line through which fuel is pumped from a storage tank to a dispenser, said method comprising the steps of:

• pumping fuel from the tank into the product line to elevate the pressure therein above a predetermined level;
• relieving the pressure in the product line to said predetermined level;
• measuring the time required for the product line pressure to be relieved to said predetermined level;
• and
• providing an indication of air in the product line in excess of an established permissible amount when the time that is measured exceeds a preselected value.

A method of monitoring leakage of automotive fuel from an underground storage tank in a service station, said method comprising the steps of:

• providing a plurality of monitoring wells at preselected spaced apart locations in proximity to the tank;
• installing in each monitoring well a probe which is sensitive to hydrocarbon concentration and which provides an electrical signal indicative of the hydrocarbon concentration sensed by the probe;
• using said electrical signal from each probe to provide a digital display of the hydrocarbon concentration sensed by each probe;
• assigning independently to each probe a preselected hydrocarbon concentration which is indicative of leakage of gasoline from the tank and which is independent of the preselected hydrocarbon concentration assigned to other probes;
• detecting when the hydrocarbon concentration sensed by each probe exceeds the preselected concentration assigned thereto as being indicative of leakage of gasoline from the tank;
• and
• providing an alarm signal when any probe senses a hydrocarbon concentration in excess of the preselected concentration assigned thereto.

Apparatus for detecting the presence of air in excess of an established permissible amount in an automotive fuel product line through which liquid fuel is pumped by a pump from an underground storage tank to a fuel dispenser, said apparatus comprising:

• means for activating said pump to pump fuel from the tank into the product line to raise the pressure therein above a predetermined level and then deactivating the pump;
• a pressure relief valve operable to relieve the pressure in the product line to said predetermined level whenever the pressure in the product line exceeds said predetermined level;
• means for measuring the time required for the pressure in the product line to drop to said predetermined level each time the pump is deactivated following activation thereof;
• and
• means for providing an indication of air in the product line in excess of an established permissible amount whenever the time measure by said measuring means exceeds a preselected value.

Apparatus for detecting leakage from an underground automotive fuel storage tank and from a fuel product line through which fuel is pumped from the tank to a fuel dispenser by a submersible pump, said apparatus comprising:

• a plurality of hydrocarbon sensitive probes spaced around the tank, each probe providing an electrical signal indicative of the hydrocarbon concentration sensed by the probe;
• means for assigning independently to each probe a preselected threshold concentration level which is indicative of leakage from the tank and which is independent of the threshold levels assigned to other probes;
• means for sensing the pressure in the product line;
• means for using the sensed pressure in the product line to detect when there is leakage therefrom above a predetermined rate;
• an above ground display screen;
• means for displaying on said screen the sensed pressure in the product line and a numerical indication of the hydrocarbon concentration sensed by each probe;
• and
• means for generating an alarm signal if leakage from the product line above said predetermined rate is detected or if the hydrocarbon concentration sensed by any probe exceeds the preselected threshold level assigned thereto.

Apparatus for detecting leakage in a liquid delivery system having a pump for intermittently pumping liquid through a product line in which the liquid is subject to possible thermally induced contraction, said apparatus comprising:

• means for sensing the pressure in the produce line;
• pressure relief means connected with the product line for relieving the pressure therein to a first preselected level when the product line pressure is above said first preselected level and the pump is deactivated;
• means for activating the pump for a pumping cycle effective to elevate the product line pressure above said first preselected level each time the pressure therein has dropped to a second preselected level lower than said first level;
• means for measuring the time required for the product line pressure to drop from said first level to said second level following the end of each pumping cycle;
• and
• means for indicating leakage in the product line if the time measured following the end of any pumping cycle does not exceed the time measured following the end of the immediately preceding pumping cycle by a predetermined amount.

Apparatus for monitoring leakage of automotive fuel from an underground storage tank in a service station, said apparatus comprising:

• a plurality of hydrocarbon sensitive probes spaced apart from one another in proximity to the tank and each operable to sense the hydrocarbon concentration and to provide an electrical signal indicative of the hydrocarbon concentration sensed by the probe;
• an above ground display screen for displaying the hydrocarbon concentration sensed by each of said probes;
• means for processing said electrical signals from the probes and displaying on said screen an identification of each probe and the hydrocarbon concentration sensed thereby;
• means for assigning independently to each probe a threshold hydrocarbon concentration which is indicative of leakage from the tank and which is independent of the threshold concentration assigned to other probes;
• and
• means for providing an alarm signal in the event that the hydrocarbon concentration sensed by any probe exceeds the threshold concentration assigned thereto.