API 653 Robotic Inspection: University of Washington

Seattle – The University of Washington (UW) recently reached out to Manta Robotics to help solve several issues they had with a large underground petroleum storage tank. The 2-million-gallon diesel storage tank, has a large network of cathodic protection cables mounted to the tank floor making an API-653 inspection really difficult.

UW was left with only two options.

Option 1

  • Completely drain the tank of its contents, clean the tank of any sludge it may have accumulated, then send personnel into the confined area to manually perform the inspection. With weeks of downtime, this process would have proven to be very costly. Environmentally speaking, the project would have released thousands of pounds of volatile organic compounds (VOCs) and CO2 into the atmosphere, and required the disposal of toxic sludge.


Option 2

  • Set up a contract with Manta Robotics to assess the tank floor, implement a strategy to perform the inspection, and complete the API inspection in a timely matter.

Contracting with the university, we were able to perform a robotic inspection, collecting thousands of UT data points, satisfying API requirements in just 4 days.

Using a new generation inspection ROV system, we were able to maneuver easily around many obstacles on the tank floor. Swimming the ROV into many hard to reach places we were able to visually assess features in the tank and collect tank floor thickness readings using our UT system.

Obstacles our ROV maneuvered around:

  • Cathodic Protection Cables
  • Support Beams
  • A Large Sump
  • Ladders


Below we have provided a video of our inspection showing the thick sludge. While submerged in the tank, we were able to identify that there were several inches of water, along with a blanket of algae that had begun to grow between the water and diesel.


Check out our videos of taking readings in the tank:

Video Description:  Evaluating the floor of an Above-Ground Storage Tank (AST) using ultrasonic transducers mounted on a heavily modified water based swimmer robot.  The fluid is red diesel.  There is water in the bottom of the tank as well.  The scum is floating on top of the water, but under the diesel.  After looking at the scum in daylight it is actually a dark green/black substance.  Though it gets no daylight it is somehow growing on top of the water.

Video Description: Evaluating the ceiling of an Above-Ground Storage Tank (AST).  This footage was taken with a swimmer robot modified for use in petroleum products.