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ROVs eliminate need for pipe swabbing

Utilizing remotely-operated underwater vehicles for underwater inspections provides numerous benefits

ROV post-disinfection prior to entering the pipeline.
ROV post-disinfection prior to entering the pipeline.

Robotics has become so advanced, that no longer are robots confined to the terrestrial realm. Robotics engineers have designed prototypes for “swimming” robots that mimic the graceful movements of fish, sting rays, sea snakes, turtles, and even the human breaststroke.

Remotely-operated underwater vehicles (ROVs) are commonly used in oil exploration and have been utilized in military and scientific applications, including research into the oceans and marine life. The 2004 search of the Atlantic Ocean floor that famously surfaced new images and relics from the Titanic shipwreck was done using ROVs that employed highdefinition video.

When it comes to underground construction, ROVs have their place as well, in particular for inspection work following the completion of new feedermains used in water distribution systems.

“We’re able to go in robotically, and take a look at the pipe and then let them know, okay you have a blockage here, or there’s a break in the pipe here, and then at that point they can ask, can we clean it using conventional methods, or do we need to dig up the roads to rehabilitate it?” Richard Engel, ROV project manager with ASI Group

Infrastructure inspections using ROVs

Post-construction, but before the pipes can be put into service, they often need to be cleaned or “swabbed” using “pigs”, which are bullet-shaped pieces of polyurethane. Propelled by water pressure, the pigs clean the pipes and remove any contaminants. For older pipes that need cleaning, pigs scrape heavy sediment, biofilm, tuberculation and hard-scaled debris from the inside of the pipe, improving water quality and flow.

Swabbing the pipes requires a lot of water to be drawn from fire hydrants, at an added cost to the municipality. But there is a way for engineering departments to avoid swabbing, or at least do limited swabbing, and that is through the use of ROVs.

A remotely-operated vehicle (ROV) can be placed into the new pipe after it is filled with water but before it’s commissioned. Or, into an old pipe that is showing signs of wear or loss of pressure.

The tethered ROV “flies” through the main and inspects it, sending video to an operator controlling the unit on surface. The results allow the municipality to determine what they should do next: re-swab the pipe, take measures to rehabilitate it, or in the best-case scenario, put it back into service because it’s deemed to be clean.

“We’re able to go in robotically, and take a look at the pipe and then let them know, okay you have a blockage here, or there’s a break in the pipe here, and then at that point they can ask, can we clean it using conventional methods, or do we need to dig up the roads to rehabilitate it?” said Richard Engel, ROV project manager with ASI Group.

The St. Catharine’s, Ontario-based company specializes in long-tether underwater inspections using ROVs; ASI also offers expertise in commercial diving and geophysical surveys.

Most of ASI’s ROV watermain inspection work is with pipelines 1,200-mm or less in diameter, where it’s not possible to get a worker in to check the line.

“A lot of these assets have the same old story – out of sight out of mind,” Engel says. “Everything is buried so nobody looks at it and then they start to think, we’re getting reduced flows, so we need to find out what is going on.”

With new construction, Engel said their ROVs are becoming popular among regions that want a pre-commissioning inspection.

“They’re saying instead of swabbing or in addition to swabbing, we’d like to get an eyeball to go down these pipes and show us that everything is as you say it is, clean and ready to go.”

The ROV is deployed through a manhole and is equipped with high-definition cameras and high-powered lights that enable it to see down the length of pipe. The municipality or region is looking for debris on the bottom of the pipe from construction, whether the pipes were cleaned before they were joined together, or for extruding gaskets. If the pipe has already been swabbed, there might be pieces of the swab that broke off and were left in the pipe.

Halton feedermain project

ASI recently completed an ROV inspection project in Oakville, Ontario, where the Region of Halton was looking to inspect a newly-installed feedermain that will supply water to the region, without having to swab.

The job involved inspecting 2.8 kilometres of 1,200-mm concrete pipe. ASI conducted the survey in three stages over a two-day period, due to pipe grades and limited access points.

The Halton feedermain project was challenging due to the multiple bends in the pipe, which cause friction for the ROV tether as it moves around corners. Also, pulling a tether for that length of pipe requires a powerful vehicle, and for that purpose, ASI employed its newest ROV, the model vLBV, which features new, adjustable thrusters.

“The new vehicle that we have is called a vector vehicle. It has four thrusters, but the angle can be changed on them,” Engel explained. “We can change the angle to generate more forward thrust if we need it. It’s a more powerful vehicle.”

ASI buys its ROVs “commercially off the shelf (COTS),” meaning they contain stock components that can be modified according to project needs.

The company currently has four ROVs, ranging from units the size of a carryon suitcase, to one capable of pulling a 10-kilometre-long tether. 

“That’s the longest tether in the world and that ROV is a very niche vehicle,” says Engel. “It’s not for water maintenance but is used in water conveyance tunnels. That vehicle is shipped all over the world.”

Like most sophisticated robotic equipment, commercial ROVS aren’t cheap; a stock model starts at $50,000, and with full modifications, can be valued up to $1.5 million.

At that price, it’s no wonder that ASI looks after its remotely-operated underwater vehicles. Prior to completing an inspection, an ROV is “baked” (sterilized) and chlorinated to rid the unit of any contaminants it may have picked up during the inspection, such as E. coli, zebra mussels or marine life.

If it looks like the ROV is going into an environment that risks damaging or losing the unit, ASI will stop the inspection. As a precaution, before the ROV enters the manhole, they’ll ask the client to sign a waiver, should any difficulties arise.

ROV entry portal.
Debris on the invert of the pipeline.
Pipeline reduction showing a portion of a foam swab left behind.

Company info

250 Martindale Rd.
St Catharines, ON
CA, L2R 6P9

Website:
asi-group.com

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