Robot Applications in Tank Integrity Inspections

George Williamson and Steven Trevino from Integrity & Emission Reduction Partners (IERP) and Shell discussed tank inspection robots at the Energy Drone & Robotics Summit. 

Trevino set the stage by discussing what types of tanks they use drones to inspect:

• API 650 atmospheric above-ground storage tanks

• Typically filled with gasoline, diesel, kerosene, jet fuel, fuel oil, or crude oil

• Huge tanks, some the size of a sports stadium

API 653 is a standard that outlines maintenance, inspection, alteration, and repairs for these tanks, and drone inspections have to follow its requirements. Established in 1992, API 653 does allow for inspection while the tank is filled and in service. 

From Integrity & Emission Reduction Partners

Normally a tank inspection involves a multi-month, very expensive process. Trevino said, “It’s a big process to de-inventory this tank, prepare it for human entry, and then acquire that data because we're establishing that corrosion rate.”

So how do you inspect a tank, especially the tank bottom, while in service? 

Robots. 

Robots aren’t an all-encompassing way to inspect tanks, but they do play a role in keeping tanks in service and extending time between inspections. 

Trevino said, “When we inspect a tank in service, we're aiming to get enough information on the tank bottom to update this corrosion rate based on damage that's detected. Then you can plan any maintenance that may need to happen.”

One system Trevino showed has a deployment tripod, aka a launch and retrieval system (LARS) since it’s going inside the tank. The system also has an umbilical, which provides power and communication to the robot to allow it to go into the fluid, to the bottom of the tank, to scan while the tank is in service. Many state-of-the-art robots like this are equipped with non-destructive testing (NDT) sensors that can scan for corrosion or other issues. 

Scanning a tank while it’s in service saves a lot of time. Trevino said, “First you have to de-inventory the tank, you have to drain it, you have to clean it. All this time, people are inside. Once people are inside, they inspect the bottom. And then you get the report maybe a week or two, depending on the diameter of the tank. Once you have the report, you need to interpret it, send your repairs to engineering, and have those repairs signed off. You're looking at potentially months before this tank is buttoned back up, reinspected and put back in service.”

He continued, “So advantages here are scanning it while it's in service, doing all your engineering repairs, signed offs, equipment staging. As soon as that tank comes down, you're ready to go with your turnaround, with your scope, planned maybe a year in advance.”

Case Studies

Trevino shared a case study where traditional tank cleaning and inspection was about $1 million per and lasted seven to 12 weeks. Using drones, they performed a tank bottom inspection while the tank was in service. It was completed in six days and internal inspection was deferred for 15 years. 

With additional time in service, time saved on the inspection, and internal inspection deferment, the net benefit of this inspection was $1.1 million. 

Williamson then shared a case study where the robotic inspection was beneficial but could have been even more effective with proper pre-planning. It was a crude oil tank that was 96 meters in diameter and 20 meters high. Sludge ranged from one to three feet deep, which posed a challenge for getting coverage along the bottom of the tank. The inspection lasted 25 days, most of which were not active inspection days because of rain, permits, and other project planning issues. 

This inspection was targeted to high-risk areas, so only about 36 square meters needed to be covered. Because of the small coverage area and other project issues, full inspection was pushed out just 24 months. However, that wasn’t a bad outcome thanks to low corrosion rate on the area that was inspected by drones.  

Inspection Drone Systems

Williamson and Trevino then jumped into the types of systems they use for tank inspection. 

First was the Sonomatic Nautilus, which is currently commercialized and undergoing certification. According to Trevino, it’s “the holy grail of in-service tank bottom inspections right now.”

Then there’s the Square Robot, which is also commercialized. It’s an ROV style swimming robot that can map the environment using sonar. It had buoyancy for diesel, but the buoyancy can be changed depending on the type of product in the tank. 

To end the presentation, Williamson and Trevino pointed out that drones and robots are one tool in the inspection toolbox and that success depends on having the right system for the right application.  Trevino concluded by saying, “You really need to cherry pick the right application for these technologies.”

Want more drone and robotic inspection & maintenance case studies and technology? Mark your calendars for June 10-12, 2024 for the 8th annual Energy Drone & Robotics Summit.