How to cut it in drainage and sewer rehabilitation

Using the sewer as a high voltage cable duct might have seemed like a good idea at the time.

The contractors working at a power station had smashed through the side of the sewer pipe, then fed the 3.5-inch diameter cable through the hole they created, down the sewer, then out through another hole on the other side.

A CCTV drainage survey carried out as part of planned maintenance identified the not-so-smart bit of ducting DIY. Then, a plan was needed to solve the problem.

Fortunately, the cables were no longer live. But what could be done about the cable that could contribute to blockages in the sewer, several metres underground?

The answer was to send a robotic cutter along the sewer, and chop the copper core cable at both ends, from inside the pipe. The 40m-long section of cable could then be winched out. The pipe was lined, again remotely, and it was as if the cable had never been there.

Making no-dig systems viable

Remote access robotic cutting technology of this sort has been available for quite some time, and is always developing, says Jon Close, a Senior Project Manager in the lining division of Lanes Group plc.

But its usefulness is much less well known than many of the technologies that depend on it to be effective, such as no-dig pipe rehabilitation.

He says: “When we’re scoping pipe lining projects we’ll often be asked, ‘Yes, but how are you going to get around that steel bar protruding into the pipe 50 meters from the access point?’ And when we say we’ll cut it out, we get blank faced. Clients don’t realise always that this sort of thing can be done.”

In fact, remote-controlled cutting is essential to most no-dig pipe rehabilitation projects, which usually involve inserting a resin-impregnated liner into a pipe, which then hardens to create a new inner pipe wall.

This is because inserting a liner, which may be up to 200 metres long, into a pipe can often involve blocking lateral pipe connections. These then have to be reopened somehow. The somehow is through using robotic cutters.

Cutting out blockage problems

One of the most common sewer blockage problems that require the deployment of remote controlled cutting technology is root ingress. Tree roots, especially, can cause significant damage to pipes, while blocking water flows.

One of the latest examples of cutting technology Lanes Group has at its disposal for these tasks is the Hachler Climb, which can be operated in pipes with diameters of 85mm to 225mm.

The Hachler Climb has a clever pneumatic drive system, with three inflatable packers, that allows it to tackle steeper inclines and negotiate tighter bends within lateral pipe systems. Think of a caterpillar that travels along a twig by alternately moving its front end and back end.

This means there are fewer places off-limits for root cutting and lateral connection cutting, if used on lining projects.

Jon Close said: “Like other so-called robotic cutters, the Hachler Climb is actually a milling machine. It does not cut, it grinds the object that needs to be removed. This is not least because a grinding process is more compact and energy efficient so can impart more cutting power in the confined space within a pipe.”

I need more cutting power Scotty!

The Hachler Climb is powered by compressed air. As with other pneumatic cutting equipment, this does limit their power. It means that, when the going gets tough, hydraulic robotic cutters come into their own.

Lanes Group drainage engineers use hydraulic remote-controlled grinding systems, like the KA-TE cutter, to tackle some of the most challenging pipe repair and rehabilitation projects in the UK.

It is deployed in pipes ranging in diameter from 300mm to 900mm, and can be fitted with a special carriage to operate in egg-shaped sewers. As with the Hachler Climb, the KA-TE can be fitted with a range of milling heads for different cutting functions.

Because its hydraulic drive uses more than 100 litres of oil, under considerable pressure, full pollution control measures need to be deployed when using a KA-TE cutter, with all outlets bunged and spill kits at the ready.

Many, many times Lanes Group has used KA-TE cutters to save the blushes of construction contractors who have unwittingly come into contact with drains, sewers and ducts while doing their work.

“One of the most common mistakes is for earthing rods to be driven straight through pipes,” said Jon Close. “Then there are steel fence posts, steel reinforcing bars, concrete posts, and steel piles. We’ve had them all. Without these robotic cutters, the asset would have had to be excavated and replaced, at considerable cost.”

Robotic cutters are also used to tackle many other materials and obstructions that must be removed from pipes. These can include hardened concrete, lateral pipes that jut into sewers, shell-fish, scale, and calcium deposits. In these cases, cutters are often used alongside high pressure water jetting.

It is not fair to say, though, that the diamond-tipped and tungsten milling heads – the two most common types – make short work of all cutting tasks. Some can take many hours of patient and skilled grinding, with the equipment repositioned multiple times, to complete the task.

With the Hachler Climb and the KA-TE, the worksite is monitored through a built-in camera system. This can be augmented with a CCTV drainage camera, often positioned at the other side of the cutting object to give the operator an all-round view.

Hybrid pipe cutting technology

Lanes Group is also turning to making use of the very latest hybrid cutting systems that use electric power combined with hydraulic systems, without compromising on power.

“Advances in compact milling technology have led to the development of robotic cutters that can use electric power, with a much smaller hydraulic component for controlling the cutting head,” said Jon Close.

“This reduces the pollution risk, especially as we can use biodegradable oils, and extends the distances we can operate at from around 100 metres with the KA-TE to 150 metres and beyond with a hybrid cutter.

“It’s opening up new possibilities for delivering smart pipe maintenance and rehabilitation solutions, both in the utility and the manufacturing sectors, where before clients would have been facing huge and costly problems.”

Cutting equipment like this is now essential to no-dig pipe rehabilitation services. It can be combined with other remote-controlled cleaning and cutting systems, such as high pressure and ultra high pressure water jetting.

Lanes Group uses all these technologies, so clients can always be sure that the most effective methods are being used to maintain their pipe systems safely, effectively, and quickly.