3D Laser Scanning Opens Path to Optimal Oil Storage Tank Inspection

With oil storage in high demand, oil company owners and tank inspectors are rapidly maximizing tank assets, increasing the need for tank measurement and inspection using the most advanced technologies.

By Jason Hayes

A glut of crude oil—and too few places to store it—is spiking demand for storage solutions for oil, gas and other fuels, and in particular, maximizing the need for the enormous, round storage tanks that dot the landscape in heavy oil-producing regions in the United States and around the globe.

The combination of too much oil production, plummeting prices, and suppressed demand from the COVID-19 pandemic are driving a major effort to keep petroleum storage tanks and terminals in good repair, retrofit or improve old tanks so they are more efficient, and construct new tanks and tank farms.

The oil market faces a storage crisis across the world, with market forecasts suggesting that the world’s conventional oil storage of about 3.4 billion barrels will be filled to its limit within the next month, according to an April 2020 article in The Guardian. In the United States, crude storage tanks are nearly 65% full, with 503.6 million barrels of crude in commercial tanks across the U.S. and an estimated capacity of 768.8 million barrels, according to the Institute for Energy Research. With the plunge in demand, US commercial oil storage could reach complete capacity by the middle of May 2020, according to Plains All American Pipeline, one of the biggest midstream companies.

Technology Creates a Better Way to Look at Storage Assets

Under this market pressure, oil producers, tank owner/operators and tank inspectors are looking for faster, more efficient inspection and construction methods, including 3D laser scanning, which enables quick, safe and accurate creation of point clouds of tank structures to reveal any problems.

Meanwhile, tank inspectors are learning how 3D laser scanning workflows can provide more complete and actionable information for their customers, which is more critical than ever as storage capacity is pushed to the limit.

In this post/article, we answer: How can owners/operators and tank inspectors move into a different type of tank measurement and inspection practice that is safer, more thorough and saves time?

Tank measurement and calibration standards remain mostly unchanged, whether the American Petroleum Institute (API) 653 standards used in the United States or the ISO standards used internationally. But what has changed are the new inspection technologies that provide faster, safer and better coverage.

Although they may look like simple structures, storage tanks are more complicated than they appear. Large petroleum storage tanks can be more than 500 feet (120 meters) in diameter and contain more than 1.5 million barrels. They also change over time, with large fluid volumes putting enormous stress and strain on tank walls and floors, leading to deformation. In addition, weather, subsidence and corrosion can lead to tank failures and the release of hazardous or toxic materials into the environment.

Laser Scanning Increases Tank Inspection Speed and Accuracy 

API 653 standards call for measured data on the verticality of tank shells, the roundness of tank shells, flatness of the tank bottom and any subsidence. Today, measurements that used to be gathered by surveying instruments known as total stations are increasingly made with laser scanning technology. 

Laser scanning uses lidar (light detection and ranging) to capture millions of individual points on a tank’s shell, bottom and roof. Laser scanning also captures information on appurtenances such as nozzles, access points, stairs and ladders as well as nearby structures and terrain. Built-in cameras capture digital images that provide additional documentation of tank conditions. The 3D laser scanner can also be used for fitness-for-service assessments (FFS).

Laser scanners are roughly the same size as total stations and use a similar tripod and workflow in the field. To conduct a scan, the operator places the scanner at a few locations around a tank. In a few minutes, the scanner captures a point cloud consisting of closely spaced 3D points on the tank and structures. Depending on the size of the tank, the operator performs multiple scans to capture the entire site. In most situations, crews using high-speed scanners can complete the work in less than one hour. 

When visiting a jobsite, inspectors need to follow defined processes to plan and execute the field work. Prior to starting large projects, inspectors may use a Google Earth view to develop approaches to capture data. For example, tanks with pumps, those with piping close to the tank, and tanks with external floating roofs may require additional scans to capture complete information. When the field work is completed, the inspectors begin the process of inspecting the digital copy of the tank. At this point, laser scanning software is essential to process the data and analyze the tank’s condition. 

Scanning Software Reveals More Tank Detail

Early lidar data-processing software was focused on managing point clouds and offered only limited functionality for analysis or modelling. With advances in software technology, the additional data from laser scanning offers a more detailed look at a tank, and the analysis process itself is far less cumbersome.

Today, software is used to take data from an inspection and automatically merge multiple point clouds into a single cohesive dataset. With the software enabling basic clean-up and organization, and the resulting point cloud provides a comprehensive and precise picture of the tank. 

The software also provides built-in functions for tank analysis that is then used to produce inspection reports. Results also can be transferred into an inspector’s in-house software for additional evaluation. 

Manually analyzing data and producing reports from total station data typically requires many hours, but with today’s laser scanning data and software, API and ISO standard reports and more information can be ready in half the time.

Once the scanning data is imported and processed, the software can be used to examine the entire tank, leading to recommendations and approaches for any required maintenance and repairs. On out-of-service tanks, where the interior is scanned, inspectors can get detailed maps of the tank bottom, using color-coding to indicate bends or depressions. Similarly, software can compare the tank shell to true vertical reference and automatically identify bulges or deformations that exceed a specified amount. This is where the benefits of laser scanning are really seen as the data shows the entirety of the tank surfaces, not just a sampling of areas that are documented with traditional methods.

The software also helps manage the area around a tank. With only a marginal increase in time on site, field operators can extend the scans to capture the surrounding ground and features. Customized analysis routines in the software enable technicians to efficiently isolate the structure or earthen berms that make up a secondary confinement. From there, the software can identify low areas or spill points in the containment berms, and then compute the capacity of the containment. This value is compared to the measured capacity of the tank to determine the efficacy of the secondary containment. The analysis can even account for an expected rainfall and adjust the containment capacity as needed.

Throughout the processing, analysis and reporting phases, the software provides a 3D visualization of a tank. Users can easily create virtual views from anywhere in the project, including viewpoints from inside or above the tank. Viewing software, provided at no charge, enables clients to view the project and make basic measurements while preserving the integrity of the original data.

Clients also can use the visualization tools to explain any issues to stakeholders. For municipal agencies, as an example, aspects such as budget authorization must be reviewed before making repairs or improvements. The graphics and extra reporting provided by the software help justify the needed expenditures.

Scanning also enables a virtual revisit at any time. When a client requests additional information or questions a report, technicians can quickly access actual measurements and field data to address the issue.

Trimble Provides Total Solution for Fast, Thorough Tank Inspection

Trimble’s complete solutions for applying laser scanning technology for storage tank inspections and calibrations:

• save money;
• increase field worker safety; and,
• produce superior results over traditional methods.

Here are some surveying and scanning solutions to consider:

The Trimble TX8 3D Laser Scanner enables users to complete 3D laser scanning projects faster than ever, with:

• high-end performance with ultra high speed scanning with consistent accuracy over the full scan range
• integrated HDR camera for fast image capture to colorize scans with minimal impact on field productivity
• integrated WLAN to enable wireless remote operation from Windows, Apple and Android mobile devices

The Trimble SX10 Scanning Total Station combines surveying, imaging and high speed 3D scanning in one instrument, with these features:

• Trimble’s high accuracy Lightning 3DM technology providing scanning range up to 600 meters and the smallest spot size in the industry—a mere 14 millimeters at 100 meters
• Improved Trimble VISION technology allows for fast and easy capture of high resolution site imagery

Trimble RealWorks Advanced Tank Edition software features highly automated, efficient workflows to thoroughly analyze complex datasets, reducing the time required to create inspection reports and volume filling tables from 3D laser scan data. It enables users to:

• create high-density 3D digital representations of storage tanks
• analyze the data following API 653 Standard guidelines
• automatically detect out-of-tolerance areas

To learn more visit https://geospatial.trimble.com/storage-tank.