Tank Cleaning Robot: Sludge Crews, SR-3 and ABB

A tank cleaning robot takes over a dangerous job at refineries and oil terminals. Crude oil storage tanks slowly collect sludge on the floor, and the usual way to get it out was to send people through a manway to remove it by hand, wearing breathing apparatus and chemical suits. This post follows storage tank cleaning from those crews to crude oil washing, then to the remote-controlled machines that desludge tanks today and the Square Robot SR-3, which inspects tanks while they are still full. It also covers TXplore, the submersible robot ABB built for oil-filled transformers, and what these robots still cannot do.

Crude oil storage tanks at the HF Sinclair refinery in Sinclair, Wyoming, July 2025. Photo: Tony Webster / Wikimedia Commons (CC BY 4.0)

Breathing sets, chemical suits and the danger inside the tank

Crude oil storage tanks accumulate sludge over time, and Gerotto, a tank cleaning company, notes that it eats into a tank's capacity, harms the quality of the stored oil and can threaten the structure. The traditional method, Gerotto wrote in 2024, is for people to enter the tank and remove the sludge by hand, a slow job that exposes them to toxic fumes and accidents. Inspection caused the same disruption. Before anyone could look at the floor, the tank had to be drained, the product moved out and the waste disposed of, and hundreds of tons of hydrocarbon vapour went into the air along the way.

A contractor inspects the inside of an emptied fuel tank on Diego Garcia during a clean, inspect and repair program, August 2022. Photo: Jan David De Luna Mercado / U.S. Navy via Wikimedia Commons (public domain)

The inside of a storage tank is a textbook confined space, entered by maintenance workers but never meant for people to occupy. A 1985 OSHA report on toxic and asphyxiating atmospheres counted 122 confined space incidents in the United States between 1974 and 1982, with 173 deaths. In the 1980s about 60 percent of confined space deaths were would-be rescuers, and more than 30 percent happened in spaces that had been tested and found safe to enter. US rules now require a written program, entry permits, attendants and a means of rescue. Even so, a 2021 profile of Re-Gen Robotics, whose founder Fintan Duffy spent years cleaning oil tanks by hand, says accidents and deaths stayed commonplace.

Navy fuels officer Lt. Adrian Tomaneng and civilian contractors inside a fuel tank on Diego Garcia for a pre-final inspection, August 2022. Photo: Jan David De Luna Mercado / U.S. Navy via Wikimedia Commons (public domain)

Tanker owners worked out their own washing methods at sea. Oil tankers first cleaned their cargo tanks with high-pressure jets of hot seawater and pumped the oily slops overboard, which the 1954 OILPOL Convention banned within 50 miles of most land. In the 1960s tankers moved to load-on-top, and from the 1970s they sprayed the crude oil itself through high-pressure nozzles, so more of the cargo could be pumped out instead of clinging to the walls. The 1978 MARPOL protocol made crude oil washing equipment mandatory for new tankers of 20,000 tons deadweight or more. In Japan, Hashimoto Technical Service has applied the same method to refinery storage tanks.

The Richfield Oil tanker David E. Day in port in the early 1950s. Photo: U.S. Navy Bureau of Ships via Wikimedia Commons (public domain)

Robots that desludge tanks and inspect them full

Cleaning robots keep the people outside. In a 2024 case study, Gerotto described a remote-controlled machine with ATEX Zone 0 certification that enters through a 600 mm side manhole. It has a bronze auger that will not strike sparks, high-pressure nozzles to loosen the sludge, and intrinsically safe lights and cameras, and a suction hose links it to a vacuum truck. In a crude tank whose floating roof had partly collapsed, leaving only 65 percent of the interior reachable, it removed 500 cubic metres of sludge in 33 days and then spent 27 days hydro jetting the walls and floor. Re-Gen Robotics started a no-entry robotic cleaning service in March 2019.

Suncor Energy's crude oil storage tank farm near Guernsey, Wyoming, July 2022. Photo: Tony Webster / Wikimedia Commons (CC BY 2.0)

Inspection robots work while the tank is still full. Square Robot was founded in Westborough, Massachusetts, in 2016 and finished its first commercial tank inspection in 2019. Its SR-3 submersible enters a live, product-filled tank through a standard 24-inch manway from a pressurised launcher with a gate valve, so the tank is never drained, degassed or cleaned. On 15 September 2026 the company received the NIOSH Prevention through Design Award at the National Safety Council's congress in Indianapolis. By then it had inspected 385 tanks for almost 100 clients in 18 countries with no confined space entries, and kept more than 695 tons of volatile organic compounds out of the air.

A Tank Industry Consultants technician sends a remotely operated camera vehicle up to the top of a 200,000 gallon water tank at Camp Lemonnier, Djibouti, 2010. Photo: Robert P. Gallagher / U.S. Navy via Wikimedia Commons (public domain)

ABB has not built a tank cleaning robot, and we found no ABB project in crude oil tanks. Its closest work is TXplore, a submersible robot for oil-filled power transformers. ABB proposed the concept in late 2012, and the tetherless robot moves through the oil with propellers and buoyancy control while its cameras film the bushings, leads and core. Because the oil stays in, no tanker trucks or vacuum filling rigs are needed, and two people can finish in under a day a job that took a large team three days or more. ABB sold most of its Power Grids division to Hitachi in 2020, and our post on transformer inspection tells that story.

A top-side technician places ABB's TXplore robot into an oil-filled transformer. Photo: ABB

Where tank robots go next, and what holds them back

Cleaning robots are also reaching new markets. Unibose, a startup near Chennai founded in 2016, says its ATEX Zone 0 certified robots enter through a standard hatch and clean out sludge, fuels and chemicals while the operator stays outside, and that they cut cleaning time by up to 40 percent. Its robots have worked at IndianOil, CPCL's Manali refinery and Borouge in Abu Dhabi, and it is moving to robot-as-a-service so contractors can hire rather than buy. Offshore, Ambipar and SBM Offshore used remotely operated robots to remove heavy oily sludge from an FPSO cargo tank while the crew watched from outside, 24 hours a day.

Noah Peyer of Tank Industry Consultants steers a remotely operated vehicle inside a 200,000 gallon fresh water tank from outside, Camp Lemonnier, 2010. Photo: Robert P. Gallagher / U.S. Navy via Wikimedia Commons (public domain)

Inspection fleets are growing too. In December 2025 Marathon Petroleum, which runs the largest refining system in the United States, joined Square Robot's Series B round and agreed to help shape its next robot. In late September 2026 Square Robot brought operators from Europe and the US to Cascais, Portugal, for a seminar on robotic tank inspection. For ABB the opening is narrower. TXplore shows it can build a robot that works inside a liquid-filled tank, but we found no ABB arm with the ATEX Zone 0 rating that Gerotto and Unibose cite. An ABB arm handling hoses or nozzles from outside the manway is a possibility, and its paths would be planned first in RobotStudio.

TXplore moving through the oil inside a transformer, with no one entering the tank. Photo: ABB

Cost and time are still the hard parts. Safety+Health magazine reported nearly $170 million in savings for Square Robot's clients, and Unibose says it builds its robots at close to half the cost of comparable systems elsewhere, yet the Gerotto job took 60 days. Each robot also has limits: TXplore, for example, can only inspect transformers large enough to take it. Skills change with the machines, and Unibose says it trains workers to operate the robots that replace the most dangerous part of their work. Drinking water tanks get the same treatment. In 2010 Tank Industry Consultants inspected a 200,000 gallon fresh water tank at Camp Lemonnier, Djibouti, with a remotely operated camera vehicle.

A demonstration of a remotely driven TXplore inspection inside an oil-filled tank. Photo: ABB

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