Protective steel membrane system and method of rapid installation of secondary containment for an above ground storage tank

Abstract

An efficient, cost-saving system and method of designing, installing, testing, and monitoring a secondary containment system for new and existing Above Ground Storage Tanks (ASTs) that is comprised of a protective steel membrane for the floor of the tank, including the floor-to-wall juncture, and the lower portion of the tank shell such that the steel membrane creates one or more interstitial zones between the steel membrane and the tank shell. The steel membrane may be installed zone by zone such that the secondary containment system can encapsulate existing tank features by molding itself around the existing contours, such as repair plates, corners, sumps, etc. Furthermore, a unique testing method using a simple electronic device is provided for on-site testing of the integrity of the weld seams that may be efficiently used after each zone is installed without requiring that the entire tank be evacuated during the construction of other zones.

We claim: 
     
         1 . A method of rapidly installing a secondary containment structure for a fluid containment vessel, comprising:
 sealingly attaching a plurality of plates directly to the interior surface of the fluid containment vessel such that one or more sealed interstitial spaces are formed between the plurality of plates and the interior surface;   wherein the placement and dimensions of each plate are determined prior to attaching the plates to the interior surface;   testing the integrity of the sealed attachments after each sealed interstitial space is formed; and   repairing any defects detected in the sealed attachments.   
     
     
         2 . The method of  claim 1  wherein the plurality of plates are comprised of steel. 
     
     
         3 . The method of  claim 2  wherein the plurality of plates is sealingly attached using one or more seal welds. 
     
     
         4 . The method of  claim 1  wherein the fluid containment vessel is an above ground storage tank. 
     
     
         5 . The method of  claim 3  wherein a refractory material is introduced into the interstitial space prior to creating any seal welds. 
     
     
         6 . The method of  claim 5  wherein the refractory material is removed from the interstitial space once the seal welding has been completed. 
     
     
         7 . The method of  claim 1  wherein the interstitial space is divided into one or more sealed zones by overlapping one or more of the plates. 
     
     
         8 . The method of  claim 1  wherein testing the integrity of the sealed attachments further comprises:
 introducing a small molecule trace gas into the interstitial space of the sealed zone wherein the trace gas permeates through any defects in the sealed attachments; 
 dragging an electronic detection device in contact with each sealed attachment wherein the electronic detection device outputs a signal upon detecting the trace gas. 
 
     
     
         9 . The method of  claim 8  further comprising providing immediate feedback to the user that is used to improve the quality of the user's techniques that will be used to create subsequent sealed attachments. 
     
     
         10 . The method of  claim 9  wherein the electronic detection device is comprised of a discrete sensor removably encapsulated inside a shroud. 
     
     
         11 . The method of  claim 9  wherein the small molecule trace gas is comprised of hydrogen. 
     
     
         12 . The method of  claim 11  wherein the sensor is a hydrocarbon gas or liquid sensor. 
     
     
         13 . The method of  claim 10  wherein the shroud is of suitable dimension for accumulating the minimum concentration or volume of the trace gas that is needed for the sensor to detect the gas. 
     
     
         14 . The method of  claim 13  wherein the shroud contains a volume between 0.525 and 0.600 cubic inches. 
     
     
         15 . The method of  claim 14  wherein a defect in the sealed attachment of less than 1 micron in diameter can be detected. 
     
     
         16 . The method of  claim 1  further comprising purging the interstitial space with an inert gas to prevent corrosion. 
     
     
         17 . The method of  claim 16  wherein the inert gas is nitrogen. 
     
     
         18 . The method of  claim 1  wherein the repair of any defects detected in the sealed attachments further comprises:
 relaxing the pressure inside the interstitial space; and 
 introducing an air-curing liquid sealant into the interstitial space. 
 
     
     
         19 . A method of rapidly installing a secondary containment structure for a fluid containment vessel, comprising:
 welding a plurality of steel plates directly to the interior surface of the fluid containment vessel such that an interstitial space is formed between the plurality of plates and the interior surface;   dividing the interstitial space into one or more sealed zones by welding one or more of the plates in overlapping contact with an adjacent plate:
 wherein each plate is pre-cut prior to attaching the plates to the interior surface based upon a pre-determination of the placement and dimensions of each plate; 
 testing the integrity of the weld seams after each of the one or more zones is created; 
 repairing any defects detected in the weld seams; and 
 purging the interstitial space with an inert gas to prevent corrosion. 
   
     
     
         20 . The method of  claim 19  wherein a refractory material is introduced into the interstitial space prior to creating any welds and is thereafter removed from the interstitial space once the welding has been completed.