Gas Main Repair Robot: CISBOT, Keyholes and ABB

Under many old city streets, gas still flows through cast iron mains whose joints were packed with yarn and lead. When a joint starts to leak, the usual answer has been to close the road and dig. A gas main repair robot works from the inside: it enters a live main through one small pit and seals joint after joint while customers keep their gas. This post covers trench and keyhole repairs, ULC's CISBOT and SGN's roadworks robot, this autumn's fight over pipe costs in Massachusetts, ABB's part in finding leaks, and where robotic repair could go next.

Gas main works in Walnut Tree Close, with the road fenced off and spoil heaped beside the trench, 2024. Photo: Mr Ignavy / Wikimedia Commons (CC BY-SA 2.0)

How crews dug up streets to fix leaking gas mains

Gas networks go back more than two centuries. The Gas Light and Coke Company, founded by Frederick Albert Winsor, received its royal charter in London on 30 April 1812 and ran the world's first public gas works; by 1819 it had laid nearly 290 miles of pipes feeding 51,000 burners. Cast iron was long used for water, gas and sewage pipes. In its bell and spigot joints the gap was stuffed with oakum or yarn to hold molten lead, while mechanical joints were made by bolting a follower ring against the bell. Lead and jute joints and bolted joints are the ones that leak in old mains today.

Watson House in London, a former food factory that the Gas Light and Coke Company turned into stores and laboratories in 1926, photographed in 1933. Photo: Willem van de Poll / Nationaal Archief via Wikimedia Commons (CC0)

Britain's answer was to replace the iron. The Health and Safety Executive says iron mains replacement programmes have run for 43 years, and since 2002 they have aimed to decommission every "at risk" iron main, meaning one within 30 metres of a building, within 30 years. Its enforcement policy for 2026 to 2031 expects all Tier 1 pipes, the first of three size tiers, to be gone by the end of 2032. Another way to cut disruption is a smaller hole. SGN's keyhole excavations let crews work from above ground with specialist tools through a small cut, then put the cut piece of road back.

Contractors replacing the gas mains at a road junction in 2006; the work along the street was expected to take about four months. Photo: Martin Addison / Wikimedia Commons (CC BY-SA 2.0)

ULC Technologies, a robotics firm from New York, took the repair inside the pipe. Its Cast Iron Joint Sealing Robot, CISBOT, fixes leaking lead and jute joints and bolted joints in live gas mains. Crews launch the remotely controlled robot from a single hole, and it crawls along the inside of the main, sealing each joint with a special sealant, up to 450 metres from that launch pit. ULC says CISBOT has sealed more than 66,000 cast iron joints in the US and UK since 2010, up to 110 of them from one excavation, and it has worked with the British networks SGN and Cadent since 2013.

Sections of old gas main lifted out of a street in Southsea, 2025. Photo: Tim Sheerman-Chase / Wikimedia Commons (CC BY 4.0)

CISBOT and roadworks robots under city streets in 2026

In the United States, the cost of digging has become a political fight. On 13 September 2026 the Boston Globe reported that Massachusetts gas customers paid roughly $800 million in 2024 for GSEP, a program created in 2014 to replace old, leaky pipes. A Future of Heat Initiative report found the extra spending had not measurably improved safety, and State Senator Michael Barrett said phasing the program out could save customers up to $1.46 billion over ten years. The group's executive director, Michael Bloomberg, pointed to excavation damage as a leading cause of incidents on gas mains: "When you're doing a lot of digging, that itself comes with risk."

A gas main fire at Melvindale, Michigan, seen from about a mile away in 2016. Photo: Rmhermen / Wikimedia Commons (CC BY-SA 4.0)

Utilities reply that the old pipe still has to be dealt with, and in London robots already do part of that work. Around Sloane Square in 2020, Cadent used CISBOT to remediate more than 1,300 joints from almost 20 pits in 44 weeks, which it says took 80 percent less time than traditional works would have. Its first emergency repair with the robot was in Whitehall, near Trafalgar Square, where CISBOT sealed 105 joints along 359 metres of 30 inch main. SGN and ULC also built RRES, a roadworks robot unveiled on 28 April 2022: an all-electric arm on a tracked base that maps buried pipes with AI, cuts the road with a chainsaw that senses surface hardness, and clears soil with air jets and vacuum.

A Cadent gas network van in north London, 2017. Photo: Philafrenzy / Wikimedia Commons (CC BY-SA 4.0)

ABB does not build in-pipe robots, and we found no ABB arm working on a gas main. Its part comes earlier, in finding the leak. ABB's MobileGuard is a laser analyzer carried in a car that measures methane and ethane at driving speeds up to 55 mph (88 km/h), so it can tell gas escaping from a buried pipe apart from methane given off by livestock or landfills. Surveyors then carry the MicroGuard on foot and use MobileGuard's maps to pinpoint the leak. In March 2026 ABB added EmissionVision, software that follows each leak from the first reading to its exact location and that ABB says enables faster repairs.

A surveyor uses ABB's hand-held MicroGuard beside above-ground gas pipework, with a MobileGuard car parked behind him. Photo: ABB

Where gas main repair robots go next

The next few years will decide how much old pipe is repaired, replaced or retired. In Britain, the HSE policy gives network operators room to use newer methods such as pipe lining, which can extend a pipe's life. Some US states are asking whether a street's gas main should be kept at all. CleanTechnica reported on 21 October 2026 that California has named 151 priority neighbourhood zones where switching homes to electric heating may cost less than keeping the gas system, and that National Grid has proposed moving about 118 homes in Winthrop and Leominster, Massachusetts, to electric equipment so leak-prone pipe can be retired.

A new gas main with branch connections laid in a trench in Southsea, 2025. Photo: Tim Sheerman-Chase / Wikimedia Commons (CC BY 4.0)

Where mains stay in service, the next step looks like robots that dig as well as seal. SGN said RRES takes accurate robot arms, which normally work inside protected and controlled environments, out into the field, and that it could cut a typical gas repair job from days to hours. ABB arms have worked on tracks before. ETH Zurich's In situ Fabricator, first built in 2014, carried an ABB IRB 4600 arm with a 2.55 m reach and a 40 kg payload on a tracked base, with the ABB controller electronics fitted into the base. No ABB street robot has been announced, so this remains a possibility.

ETH Zurich's In situ Fabricator, a tracked robot built around an ABB IRB 4600 arm, beside a curved steel mesh wall, 2017. Photo: Gramazio Kohler Research, ETH Zurich / Wikimedia Commons (CC BY-SA 4.0)

Street work is wet and dirty. ABB sells its IRB 1300 in IP67 and Foundry Plus 2 versions that seal all electrical components, so the robot can work where there are high levels of liquids and dust, and the Foundry Plus 2 version adds stainless steel on the end effector to stop rust. A field cell built around an arm like that would be planned and tested first in RobotStudio, long before it reached a road. Our post on sewer inspection robots covers a related job under the street.

An ABB IRB 1300 with Foundry Plus 2 protection, built to handle water and dust. Photo: ABB

Cost, safety and skills are still open. Massachusetts lawmakers are already questioning what customers pay for pipe work, so a new machine has to save money as well as time. Excavation damage is a leading cause of incidents, and RRES is designed to scan the ground before digging and uses sensors in its tool head to avoid hitting buried pipes and cables. SGN said RRES would give its engineers new equipment and new skills. ABB's GoFa cobot shows one way to make training easier: ABB says its Easy Teach Device lets users program the robot by hand, without hours of training.

Teaching a weld by hand with ABB's Easy Teach Device on a GoFa cobot. Photo: ABB

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