More often than not, trenchless technology is leveraged for the installation of underground utilities, creating the least amount of surface disruption possible. But what happens when installed pipelines actually need to be removed? This situation occurs more than one would think and when it comes to horizontal directional drilling (HDD) projects, the pneumatic pipe rammer can be the driller’s best friend when things don’t go as planned.
Recently on a pipeline project near Houston, HDD contractor Directional Service South, LLC., of Bossier City, Louisiana, faced the prospect of having to extract and replace a sizable section of recently installed gas transmission main. Jake Gautreaux, founder and co-owner of Directional Service South explained, “For this project, we were tasked with installing several miles of 20-in. gas transmission main. After one particular 1,200-ft installation, crews noticed an issue with some damage to the pipe. It was going to need to be replaced.”
According to pipe ramming specialist Rick Melvin from trenchless equipment manufacturer TT Technologies, of Aurora, Illinois, pipe extraction is an evolution of existing ramming techniques developed over time. He said, “The extraction process is really an extension of several HDD Assist methods we developed over the years using the pneumatic pipe rammer,” Melvin said. “The things we’ve learned from salvaging stuck bores and retrieving drill stems with the help of pipe rammers has enabled full scale pipe extraction to become a reality.”
The project in Houston would put that knowledge to the test.
Directional Service South- Doing Things Better
Gautreaux has more than 23 years in the HDD industry. He first started working for an HDD contractor in high school and college, completing sewer and water work, eventually expanding into pipeline projects. Gautreaux saw an opportunity in pipeline work and after a few years went on his own and started Directional Service South.
Directional Service South was established in 2005. The company specializes in gas industry pipeline work and employs 35 to 40 people year round. According to Gautreaux, the company’s service area is broad, but most work occurs regionally. “We’ve traveled and worked in quite a few places. We’ll travel anywhere, but 90 percent of the work we do is in Texas, around the Houston area” he said.
Gautreaux takes pride in the safety program at Directional Service South. “Safety is a primary concern. We’ve partnered with Omega Alliance [Conroe, Texas] and have developed a really good safety program,” he said. “We have a very strong Jobsite Analysis (JSA) system in place where everyone can contribute to it and help make it better. We continue to grow and sharpen our skills and the way we do things. We learn every day and work to better ourselves and the industry. It’s all about doing things better, safer and more efficiently.”
Pipe Extraction- Pull Force Meets Percussive Force
Pipe rammers have been used in various ways on HDD projects for several decades. These pipe rammer HDD assist methods have been developed cooperatively between HDD contractors, engineers and trenchless equipment manufacturers. Pipe extraction has been part of this process.
“Contractors have been using pipe rammers on HDD projects to help install pipe under challenging areas like waterways for a long time,” Melvin said. “Through the pullback assist methods, percussive force from a pipe rammer on the back end of a pipe string can help prevent hydrolock and ensure a smooth installation. Now when things don’t go as planned, a drill stem breaks or a segment of pipe needs to be removed, we can do those things as well, again using the percussive power of the pipe rammer to help remove or salvage those products from the ground.
For a full pipe extraction, it’s about using the right balance of force. In this case you need pulling force, which can be an excavator or directional drill combined with the percussive force of the pipe rammer. Now these forces can be combined and applied in different ways depending on the specific jobsite situation. That’s where the complexity of the process lies. How to balance and apply the forces in a way to remove the pipe from the ground.”
Jobsite Report- Remove & Replace
The job in Houston was an infrastructure expansion included more than 30 HDD crossings of 20-in. steel gas pipe. Installation lengths ranged from 500 to 3,000 ft. Pipe welds were wrapped in ScarGuard to help protect them. One particular 1,200-ft section of pipe under a bayou raised concern.
“We installed the crossing without trouble, but couldn’t tie it in right away because we had to spin around and install the next crossing, drilling the other way. So, we were basically sitting on top of the one we just put in,” Gautreaux said. “After we installed that next pipe section and moved out of there, we were able to access that first pipe. We noticed a large scratch on it, made by an unknown underground obstruction. The scratch ran the visible length of the pipe and breached the coating. At that point, a decision regarding the future of that section needed to be made.”
After reviewing with the project owner, it was determined that because there was no way of knowing the extent of the damage to the underground portion of the line, that the pipe would need to be removed and replaced. The new pipe would be completely wrapped in ScarGuard to help prevent any possible damage.
Initial attempts to use static pull force to remove the pipe failed and the pipe rammer was brought in to assist the extraction. “The fact that the pipe had been in the ground at that point for two months, combined with the wrapping on the welds which is abrasive and creates friction, made pulling the pipe out extremely difficult. In addition, we wanted to pull in the 1,200-ft replacement section of pipe at the same time. That’s when we brought in the 24-in. diameter Taurus rammer to complete the extraction configuration,” Gautreaux said.
The pipe ramming tool was added to the back of the pipe string, completing a rather well-constructed extraction set up. “What we have during extraction is pull force on the front end of the pipe and percussive force on the back end of the pipe string,” Melvin said. “The Directional Service South crews used a 150-ton, six-part block system to channel the static pull force from a crawler track unit, that was doing the pulling, to the lead end of the pipe.
The percussive force of the pipe rammer, in this case, is used to re-activate the drilling fluid already surrounding the pipe in the bore hole and get the pipe moving so the static force can be used to extract it. You can’t pump any more bentonite, so you have to try and use what’s already down there.”
After 10 minutes of ramming on the back of the pipe string and pulling on the lead end, the pipe started to move. Crews were able to extract the pipe in two 600-ft sections. The project took approximately two 12-hour days to remove the existing 1,200-ft pipe and pull in the replacement pipe simultaneously.
“The hammer worked great in breaking the line free allowing equipment to continue movement. That’s the reason why we bought the hammer, to have it in our fleet and on the jobsite,” Gautreaux said. “It’s a huge convenience to have it with because time is of the essence when problems arise. And wrapping the entire pipe fixed the problem. There was no damage to the new pipe after installation.”