The University of Washington located in Seattle, Washington has a difficult-to-assess tank floor in their standby generator fuel tank.  This AST (above-ground storage tank) style vessel is under a parking lot.  It also has a cathodic protection system mounted to the floor of the tank making robotic floor crawler type inspections next to impossible.  The inspection option available to the University was to completely empty the tank, clean out the sludge, and steam clean the tank to safely allow a human to enter the confined space.  This would have proven to be very costly to the University as they have nowhere to put the fuel available, and it would require over 50 tanker semi trucks loads to remove the fuel.  Then there is the emissions problems when cleaning the tank.  This would have required releasing thousands of pounds of caustics and CO2 into the atmosphere as well as disposal of toxic sludge.  In reality this could have cost hundreds of thousands of dollars, if not a million.

We, Manta Robotics, were contacted to determine if we could analyze the floor of this difficult tank.  Our company specializes in robotic inspections as defined in API 653.  We have an NFPA (National Fire Protection Association) certified model of a floor crawler inspection robot.  However, after reviewing the constraints we determined it would not be suitable and could possibly get stuck in the tank.  We proposed using our swimmer inspection robot.  We have a swimmer inspection robot that is currently going through certification to NFPA requirements.  It is designed using a similar safety strategy as the floor crawler robot, using the same safety systems.  The tank contains diesel so the risk is minimal.  The swimming robot is actually a Video Ray Pro 4 robot we heavily modified for the purpose of fuel tank inspections.

Our swimmer allowed us to enter the tank and maneuver around the obstacles that included: support beams, a sump, ladders, and the cathodic protection cables.  We can drop down into any portion of the tank and take thickness readings on the floor with relative ease.  In the course of the inspection we collected more than 2000 data points.  In a few days and we were able to satisfy the requirements of an API 653 floor inspection.  We had confidence in our robot before the inspection, but this application really showed how our swimmer robot can be used in very difficult tanks.