Robots Can Make Tank Inspections Safer and Cheaper

With demand for oil increasing and demand for refined-product storage within the midstream sector also increasing, operational reliability and uptime have become a greater priority for the owners and users of terminals and tank farms. The industry sees value in optimizing tank turnaround schedules and extending tank in-service intervals by predicting and avoiding failures while reducing the health, safety, and environmental risks associated with waste removal and human exposure.

Robotic applications have developed to the point where they can help improve the reliability, safety, and costs of tank storage. Getting companies on board with robotics is not an issue, but finding the right in-service tank-inspection approaches for robotic applications is.

“Robotics has always been in my mind as a mechanical professional,” said Rafael Rengifo, engineering director at Phillips 66. “We know what we can achieve. The question is how.” 

Rengifo spoke at a panel discussion during the American Petroleum Institute Inspection and Mechanical Integrity Summit that focused on ways in which owners and users can incorporate robotics into their tank-integrity programs, as well as the obstacles they and other vendors face in facilitating robotics. He said that tank integrity has become a focus for operators for decades, especially following the publication of API Standard 653 which covers tank inspection, repair, and reconstruction. Several states have either referred to or incorporated that standard into their petroleum aboveground storage tank (AST) regulations, but the standard does not prescribe a specific inspection method.

Traditional AST floor inspections are performed manually, requiring storage tanks to be taken out of service, cleaned, and degassed to allow workers to enter the confined space. This can be costly on two fronts, both in prepping the tank for human occupation and in the money lost from an out-of-service tank.

Robots take the human element out of tank inspection. They allow operators to conduct inspections more frequently while keeping them in service, prioritizing tanks for turnarounds, and extending inspection intervals through risk-based inspection (RBI) concepts. RBI has been incorporated into the latest editions of API 653. Rengifo said that regulators, however, are hesitant to move forward with these concepts without the development of additional safeguards, and he pointed out a lingering skepticism among some operators about the effectiveness of robot inspections.

To combat this hesitancy, Rengifo said, robotics developers need to identify areas within the industry that might be more amenable to hearing what they have to say. For instance, he said the midstream sector is an agile sector where maximizing the run of a tank is critical.

Phillips 66 has sponsored a number of industry research projects in the robotics space. In late 2017, it partnered with the tech startup Square Robot to develop an autonomous, untethered robot to inspect petroleum product storage tank floors while the tank remains in static service. The joint venture provided Square Robot with access to a team of experts in nondestructive testing inspection, safety, procedures, and operations. Rengifo said investing in other companies creates an incentive to get involved in development.

“Our company decided not only to support and sponsor development in R&D, we decided to invest in our robotics department,” Rengifo said. “In being investors, we have a very clear interest to collaborate. That goes beyond just providing the funding. It goes back to connecting with the learning and applying the lessons we have learned in the company.”

Diakont’s energy services division has been heavily involved in the tank-inspection space. The company’s most recent release, Stingray, is an inspection system certified to operate equipped with multiple nondestructive-evaluation sensors that assess the integrity of a storage tank floor. The system is equipped with magnetic flux leakage (MFL) and ultrasonic testing (UT) sensors. MFL uses a powerful magnet to magnetize conductive material (usually steel) to detect defects (either from corrosion or material loss)—where there are defects, the magnetic field “leaks” from the steel. UT uses ultrasonic waves (usually short-pulse waves) that are transmitted into materials to detect internal flaws. Using both methodologies in an inspection can help operators obtain a higher degree of confidence in confirming a defect or a leak in a tank.

Stingray is certified for NEC Class 1, Division 1, inspections, where ignitable concentrations of flammable gas or vapors exist under normal operating conditions. Steven Trevino, a business development manager at Diakont, said it was one of the first systems certified for this class of inspections that includes both MFL and UT.

“If you are familiar with electronic certifications, [Class 1, Division 1, certification] is a huge component of the technology development process and the implementation across your business,” Trevino said.

Mark Slaughter, business development manager at Intero Integrity (formerly A.Hak Industrial Services), discussed, among other things, the functionality of robots for tank inspection, using A.Hak’s OTIS series of robots as an example. OTIS comes equipped with a patented acoustic navigation system that pinpoints its location within a tank, using onboard UT transducers to help the robot follow a predetermined digital inspection grid. The robot then collects millions of ultrasonic scans of the tank bottom in order to perform computerized data analysis. An onboard sonar system helps detect objects in the tanks, and a flushing system ensures that the steel is relatively clean and free of debris, minimizing the effects of echo loss.

Slaughter said accuracy of location within a tank and the clarity of the readings that a robot collects are critical to inspections.

“We have to drive the robot, and then we need to know where we’re at inside the tank,” Slaughter said. “We need to be able to see what we’re looking at, and we need to know where our position is. So, we have receivers around the circumference of the shell that allow us to triangulate where we’re at inside the tank. We have a sonar tool that allows us to avoid hitting or bumping up against something.” 



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