Astec DD4045 tackles demanding project
Drilling a 550 mm diameter hole for a 315 mm polyethylene sewer through 152 m of broken rock and clay under a 9.5 m hill at an angle of precisely 1.3 degrees is no picnic, even for a company as experienced and skilled as Brisbane’s Temcove.
To successfully complete a project such as this, a combination of electronics and old fashion surveying that give the level of precision is required.
“For a start, you’ve got to get a zero plane through the hill so you have a data point. Then you work everything off that data point or invert level,” said Temcove Director Lyle Johnson.
The project, in Brisbane’s Wacol area, couldn’t be open trenched because the height of the hill involved made it completely impractical. Johnson brought in an Astec DD4045 horizontal directional drill supplied by JB Attachments because it had the power to punch through the different soil conditions involved. Preparation alone took two weeks, including digging a starting pit 4.5 m deep for the machine so it could drill upwards to achieve the correct grade.
Mr Johnson has been buying drilling equipment from JB Attachments for more than 15 years. Peter Decker, from JB, said this particular job was extremely technically demanding, the kind that most companies won’t take on because of the risk of getting it wrong.
“Even if you get the bore through and the pipe in, if there are any dips or hollows, the whole project gets abandoned,” said Mr Decker. “Then you can get charged for the removal of the pipe you’ve just installed. And possibly there’ll be another company brought in to correct the job you’ve done. So people take on a huge risk with this style of work.
“Temcove has been in the game for many, many years, but I would say without the latest model Astec machine, they wouldn’t have attempted this job. It has the strength and the pump capacity to handle it.”
Mr Johnson described the amount of mud mix required for the job as “astronomical”.
“You’ve got to keep the heads cool, you’ve got to lubricate the bore. We ended up with a 550 mm diameter hole, so you can imagine the amount of cuttings and the amount of drill fluid needed,” he said.
“If the bore’s not clean and you don’t have mudflow, there’s no way in the world you’re going to get that pipe in. You risk frac outs or other failures if you have a pressure build-up due to a dirty bore.
“If you put that much pressure around your pipe, it’ll seize in place. Then you’ll end up having to throw the pipe away and start again.”
One of the reasons Mr Johnson keeps going back to JB Attachments is the after-sales service.
“You get the service from JB that you just don’t get elsewhere,” he said.
CDS turns to JB in New Zealand
On the other side of the Tasman, JB Attachments has established a relationship with Goodeng, a leading Chinese manufacturer of high-quality, robust HDD equipment.
“Goodeng provides good value for money, good quality, and it builds some of the largest directional drills in the world,” said Tim Balemi, Executive Director of JB Attachments.
“Goodeng offers a large range of self-contained and maxi directional drills. We can supply from a 20 tonne machine right up to the 80 tonne model, capable of laying very large diameter pipes over long distances.”
It was those bigger machines that mainly interested Graham Clough, Managing Director of CDS New Zealand, so Mr Balemi took him to China to inspect the top four manufacturers of maxi drills first-hand.
“In the end we came back to Goodeng because we felt they had the better service and they were willing to accommodate our specifications,” said
Mr Clough requested a larger operator cabin than usual, along with customised operator controls, both of which Goodeng was able to provide. Recently, he took delivery of a Goodeng MD3500 machine capable of 800,000 pounds of thrust.
“It’s capable of drilling a 2 m hole up to 3 km in length. But there’s a lot more to drilling than just buying a big drill,” said Mr Clough.
“The secret to drilling is removing the cuttings. If you don’t, they just lay in the bottom of the hole and when you go to pull your pipe in, it’s going to pressurise and eventually you’re going to have all sorts of dramas.
“With the big machines you need big mud pumps, big mud recycling systems, and the right drill fluids.
“You’re pumping through between 500 and 600 gallons a minute. And if you’re mixing up a 34,000 litre tank of drill mud, that’ll cost you somewhere in the vicinity of $A8,000-12,000. If you just pump that into the bore it’ll last probably 15 minutes. So we built a huge recycling system as well so we can recycle up to 700 gallons a minute.
“The machine is just part of the parcel. JB Attachments is also the agent for MI-Swaco drill fluids, and we feel these are by far the best drill fluids that you can buy.”
CDS recently installed a 500 mm, diameter 580 m pipe through rock under the estuary of Brigham Creek in Auckland.
“We used a mud motor turning a 220 mm diameter tricone bit for the pilot bore. Once we got through we removed the mud motor leaving the drill string in the pilot bore. A 630 mm forward reamer was then pushed through, removing the drill string as it exited the pilot bore. Once completed, a back reamer was fitted of the same size and pulled back with the 500 mm diameter pipe behind from the exit pit,” said Mr Clough.
“Going under an estuary you can’t afford to have any frac outs. The whole area was environmentally sensitive and we managed to do the job cleanly with no spillages.”
Mr Cloughs says a big factor in the success of this demanding job was the support and back up of JB Attachments.
“JB Attachments has looked after us and every issue was resolved. They want it to go right, they don’t want any glitches. They’d bend over backwards to help us get the job done.”