Articles & Case Studies

High-tensile Steel Pipe Removed from Clay Drain

Posted: Monday 24th November 2008

Remote cutting system successful despite restricted access.

A large-bore clay drain pipe, five metres below the floor of a shopping centre in Bristol, UK, was substantially obstructed by a cylindrical high-tensile steel support pile that had been driven down through its side inadvertently. The client needed the drain’s integrity restored with a liner, but first the intrusion - which was eight metres from the nearest point of access - had to be removed.

Problem

Investigations conducted by Dyno-Rod into the cause of a severely blocked 300mm i/d clay drain pipe on the site of newly-constructed shopping centre in Bristol, UK, revealed that a 178mm diameter, 12mm wall thickness, high-tensile steel tubular support pile had been driven down through the side of the pipe, which was 5 metres below ground. As a result, foul waste flow through the drain was severely restricted and solid matter was backing up. Access to the drain was limited to a 600mm manhole opening, which led into an 1800mm chamber, but there was only 1 metre of clearance from the open end of the drain to the chamber wall. The pile was also some 8 metres away down the drain, so any removal solution would have to be operated remotely. To make the working environment even more difficult, the drains were still active and could only be blocked for a limited period each day.

Solution

Tube Tech’s R&D engineer, Graham May, examined the problem in depth and fabricated a full-scale site mock up in order to test possible solutions. The chosen solution was a remote-controlled, semi-automatic, bespoke hydro-cutting head, which used a combination of super high-pressure water and an abrasive medium to cut through the solid steel wall of the pile. The cutting head was mounted on a modified gear box, designed to rotate around the internal circumference of the drain so that it could cut an arc through the obstruction.

The chief operational difficulty would be cutting the thick steel wall of the front and back of the pile simultaneously, without damaging the clay drain pipe and possibly causing the surrounding ground to collapse. Once on site, Tube Tech’s operatives were able to monitor and maintain progress via a remote camera housed in a protective shroud and mounted just behind the cutting head (click the video button at the top of the page to see the cutting underway). A compressed air ram kept the rig locked in place against the drain wall, so that the cutting head could keep the jet precisely on target.

Benefits

With the pile intrusion removed, the client was able to have the drain repaired by lining it. Tube Tech knew it was important that enough of the steel pile was cut away to ensure that the liner itself was not fouled or damaged on insertion. Thanks to the ability of the rig to get the cutting head to within just 25mm of the drain wall, this was successfully achieved. Mike Watson, Tube Tech’s technical director, commented: “This job presented just the kind of challenge we relish. With our extensive experience of designing systems to work in all kinds of pipelines, we were able to make some key modifications to a tried and trusted rig so that it could carry a high-pressure, rotating, hydro-cutting head and a video camera.

Working remotely in tough conditions five metres underground and eight metres away from the pile we were cutting, and achieving success where previous companies had failed, is the reason why we can say with justification that we ‘clean - or cut, in this case - the impossible’.”

Dyno-Rod was called in to tackle the problem after several other companies had said it was beyond them. Local Dyno-Rod franchisee Reg Illingworth said: “Once I knew this was bigger than even the toughest drain cleaning job Dyno-Rod normally tackles quite happily, I contacted Tube Tech, the specialist working partner we regard as our last line of defence. As I expected, they didn’t let me down and once the pile section was removed it was possible to line the drain and restore it to normal operation.”




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