One-Pass HDD Installation
In January, a 720-ft, 24-in., DIPS HDPE sanitary sewer line was installedusing horizontal directional drilling in Corunna, Ontario, Canada. The entireproject took about five days to complete.
However, this was more thanjust a run-of-the-mill HDD installation. The project served as a pilot projectfor an innovative drilling method that involves the elimination of multiplereaming passes and a creative, yet functional, way to utilize drilling fluids tomaintain the bore’s stability and keep the pipe on grade.
How many times haveyou thought in your job, “There has to be a better way to dothis?”
Rodger Laking, president of Ontario Trenchless Construction,Vittoria, Ontario, Canada, was someone who asked himself just that. Now aftertwo years, Laking is ready to market his method that involves one-passinstallation for any size of product pipe. He applied for the method’s patent 18months ago and is currently in licensing negotiations with a leading HDD toolingmanufacturer to make and distribute his Rotary Flow Through Pullhead Reamer,which is attached directly behind a conventional reamer to make his drillingmethod work.
Although Laking is a relative newcomer to the HDDmarketplace, he is no stranger to utility construction. His background adds upto 40 years of installing water and sewer lines via open-cut methods.
“When I got involved with the directional drilling business, I wasn’t adriller so I didn’t understand why they had to do all these things they weredoing,” Laking said. “Where everyone in the drilling business is taught to do itbecause that’s the way it’s always been done, I just kind of looked at it andthought there’s got to be another way.”
What Laking was looking for was abetter way to do on-grade HDD work. “The problem with directional drilling andtrying to do on grade work is the multiple passes of the reamers,” he said. “Youdrill out with the new locating equipment, such as the DigiTraks and theEclipses, and you can locate the drill rod on the drill out very precisely. Theproblem comes when you pull the reamers back.”
Laking explained that it’sbecause of the weight of the reamer and rods that, after several passes, thehole is cut out mainly at the bottom. “Chances of getting that pipe on gradewith the original method are very slight,” he said. “If you have high-gradienton your pipe, then you have a chance of getting somewhere close… because yourpipe is going to float when you pull it in.”
Also, depending on yoursoil, you could have a collapse of your hole if it hasn’t been properly workedwith the drilling fluids or you could lose flow and have frac-outs, Laking said.“We can determine the path of the drill rod exactly but because of thepre-reaming and everything that happens in the hole, we couldn’t determine wherethe pipe was going to be in relation to the drill rod and drill out.”
“The theory was to make theinstalled pipe follow the drill rod. The only way to do that was to make it aone-pass installation,” Laking said. “The only way to do that was to have a hugedrill that could pull this pipe in and pull a 36-in. reamer, for example, all atonce. But even then, you had a 24-inch pipe floating around a 36-inch hole. Soyou still couldn’t control your grade exactly. So we had to reduce the annulusaround the outside of the pipe to 1-inch larger than the pipe. Now we cancontrol where that pipe’s going to be. It developed from there.”
Withoutthe large annulus around the outside of the pipe, where does the drilling fluidmaterials go? “I thought, ‘wait a minute… We’re installing a 24-inch or whateversize pipe. We’ve got lots of room to get rid of the material,’” Laking said. “Icouldn’t figure out why someone hadn’t thought about this before. We’reinstalling pipe, why can’t we put the fluid into the pipe?”
Simply put,the drilling fluids are run through a 6-in. carrier pipe inside the product pipeas its being pulled back. The material is taken through the pipe to the back ofthe hole at the surface where it’s loaded into bins or vacuum trucks to disposeof it.
So how does it work? Normally with HDD, the hole you pull theproduct pipe through is approximately 1.5 times the outside diameter of thatpipe. In the case of the pilot project, 24-in. pipe was being installed,necessitating a 36-in. hole, which would require at least three reaming passes.With conventional HDD methods, after the pilot bore was drilled and the drillrod was verified as being on grade, a 12-in. reamer would be attached to thedrill rig to begin enlarging the hole. This reaming pass would be followed by an18-in. one and then a 24-in. one and so on until the hole reached its finalsize.
In order to accomplish Laking’s one-pass installation, hedeveloped a Rotary Flow Through Pullhead Reamer, which cuts a hole 2 in. largerthan the outside diameter of the product pipe. “We drill out, verify our gradeand we hook onto our pullhead reamer,” Laking explained. “We have a reamer infront of our pullhead that cuts a hole 2-inches smaller than the outside of ourpullhead reamer. As we pull it through, all the slurry goes into the rotarypullhead. We have the product pipe attached to the back of the rotarypullhead.”
Laking notes theimportance of the drilling fluids in making his method work. “It is importantthat we use the proper slurry mix because that determines the speed of thepullback,” he said. “By putting it inside, we have a direct path from thepullhead and reamer for the mud and soil to travel to the surface. The carrierpipe goes to the surface so you have a continuous outlet to the surface,preventing built-up of in-hole pressure.”
He added that he worked withBaroid Industrial Drilling Products throughout the design of the method, inparticular with Frank Canon and Peter Armstrong. During the pilot project, therewas a Baroid representative onsite to monitor the project.
The Pilot Project
The pilot project usedto officially test Laking’s method occurred Jan. 25-26 in Corunna, Ontario. Thetest project involved installing a 720-lf, 24-in., DIPS HDPE sanitary sewer line(with a 26-in. OD) on grade in blue clay soils, which required a 4 to 1 ratio ofbentonite/slurry to soil. The installation was for St. Clair Township, which issituated along the St. Clair River just across from Port Huron,Mich.
R.B. Somerville, King City, Ontario, provided Laking use of itsAmerican Augers DD10 for the job. The crew drilled out on grade and then theRotary Flow Through Pullhead was connected to the drill rod. A Melfred BorzallTerminator reamer was attached to the front of the pullhead. Pullback started atnoon on Jan. 25 and was successfully completed by 8 a.m. Jan. 26. Laking said hehad bid the project to take 10 days but when he was finished, he had installedthe 24-in. pipe in 20 hours of work. The pilot bore had taken about four daysdue to the flatness of the grade (.015 percent) involved.
Laking cites three primarybenefits of using his new drilling method: 1) you can now install pipeaccurately on grade; 2) you can install larger diameter pipe up to 50 percentfaster and also reduce your costs; and 3) elimination of frac-outs, which is amajor environmental concern for project owners.