With several large natural gas transmission pipeline projects underway, industry leading pipeline construction contractor Pumpco, Inc., Giddings, TX, has been busy installing gas pipeline throughout the United States. The multi-facetted pipe contractor is well versed in a wide range of pipeline installation methods. On a recent section of pipe in Southern Texas, near Big Bend State Park, the contractor employed pneumatic pipe ramming to install a section of 42-inch pipe under a roadway, through extremely difficult soils.
Pumpco Project Manager Hunter Hill said, “The material we were in was best suited for the ramming application. Some of the cobble was as big as 18 to 20 inches. That’s half the size of the product pipe. We wouldn’t have been able to utilize other methods for this installation. It is really the kind of ground that pipe ramming is the method of choice for.”
The 215-foot ramming project was part of a larger natural gas pipeline installation. This particular section of 42-inch steel product pipe proved to be very challenging. To install the pipe, Pumpco crews used a 32-inch diameter Grundoram Apollo pneumatic pipe rammer from trenchless equipment manufacturer TT Technologies, Aurora, Ill.
TT Technologies pipe ramming specialist Rick Melvin said, “This project was full of challenges, but Hunter [Hill] and his Pumpco crew know what they’re doing with their modified pipe ramming version of slick bore. Plus, having the most powerful pipe rammer in the world on the job, helped as well.”
Pumpco, Inc. is a leading pipeline construction company providing a range of pipeline construction services including new construction, maintenance, and rehabilitation work on existing pipelines, as well as repair, retirement, and removal services. The company and its employees have years of experience in the construction, fabrication, upgrading, and maintenance of all types of pipelines throughout Texas and the United States.
With a workforce of approximately 1,800 people, and 500 people being employed for over 10 years with Pumpco, the company leads the pipeline industry in experience, quality and safety.
Hill said, “Our employees share a common goal of working safely and protecting the environment, which is reinforced every day on every job. All employees are empowered to report unsafe conditions or environmental concerns. The company has a real commitment to safety and makes an extensive amount of training available from first aid and CPR to confined space entry, excavation safety and more.”
Pipe Ramming Impact
Pneumatic pipe ramming has made a significant impact in several industries over the years, especially in the oil and gas industry. Melvin said, “Pipe ramming is a major force in the natural gas and oil pipeline installation industry. Any time you need to cross a road or railway with a large diameter pipe, pneumatic pipe ramming is part of the conversation. The method is extremely capable in all kinds of soil conditions. It can be used as the primary installation method or it can assist other methods like directional drilling or pilot tube boring machines.”
Ramming tools, in general, are capable of installing 4- through 147-inch diameter pipe and steel casings. Ramming can be used for horizontal, vertical and even angled applications. It is often used under roads, like the Pumpco project, and rail lines because it displaces the soil without creating voids or slumps.
Melvin said, “Some installation methods can jeopardize the integrity of roads or rail lines because they remove soil from underneath to allow for the new pipe installation. Pipe ramming’s ability to install various sized casings without putting the topside structures in danger makes it a very attractive option. Pipe ramming works in difficult soil conditions. Boulders and rocks, as large as the casing itself, can be swallowed up as the casing moves through the soil and can be removed after the installation is complete.”
Soil conditions in rugged South Texas required a ramming solution for the installation of the 42-inch diameter pipeline.
On The Job
While the process has different names depending on the region of the country, the slick-bore or dummy-bore process is simple in concept. Crews complete the installation using a “dummy” casing or bore pipe. They clean it out completely, then weld the actual product pipe to that casing. A winch, excavator or even a directional drill can be used to pull the casing out or a rammer can be used to push it out via the product pipe. As the bore pipe is removed the product pipe is pulled into place. The bore pipe does all the difficult work and allows the product pipe to be installed as stress free as possible.
Pumpco crews began by digging a 160-foot trench leading up to the crossing to accommodate the new product pipe on the north side of the road. According to Hill, the cobble filled soil was fairly easy to dig through. An oversized trench was completed on the south side of the road to facilitate pipe ramming operations. Once prep work was complete, crews welded a cutting shoe on the lead end of the first section of .600 wall dummy pipe.
Melvin said, “The cutting shoe really strengthens the leading edge of the pipe for maximum penetration through difficult soil and rocks. Because of its oversized cut, the shoe reduces both external and internal friction on the pipe. The cutting shoe also helps protect the pipe’s coating or insulation. Now on the Pumpco project, they were not able to utilize bentonite, but in other configurations the cutting shoes also create a channel for the flow of a bentonite/polymer mixture. Their conical internal surface reduces soil displacement and influences the bore’s accuracy.”
Once the pipe and cutting show were in place, Pumpco crews positioned the 32-inch diameter pipe rammer and made the connection to the 42-inch diameter pipe with standard segmented ram cones. Pumpco crews cradled the casing and pipe rammer with straps and side booms. Three 1600 CFM compressors were used to power the rammer.
Ramming proceeded without incident for several casing sections until progress slowed dramatically. Hill said, “The entire crossing was approximately 215 feet from entry to exist. We made it 155 feet and ran into, what I’d describe as, a naturally occurring coble concrete that completely halted the progress. We advanced 4 feet one day and then maybe a foot the next day. So we decided to stop, figuring that the pipe might actually be collapsing, and try to dig it up and see what we encountered.
“We had to use a hammer hoe to break through the material and expose the pipe in the easement. If we didn’t have that big hammer, we wouldn’t have made it to the other side, we would have been stuck under the road.”
Once the pipe was free, Pumpco crews rammed another section of bore pipe in and cut off the now deformed cutting shoe. After backfilling back to the road, crews began cleaning out the casing.
Hill said, “We used an HDD rig to clean the spoil out of the carrier pipe. First we used a mud motor, going in and out for the first 20 feet or so. Then we ran some cross over subs and used a 24-inch rock motor backwards to clean out the rest. We yo-yoed through it pulling out a little bit at a time until we only had a little bit of debris in the bottom. Then we pushed a pig through the pipe and that squeegeed it right out.”
After the spoil was clear, crews welded the new product pipe to the end of the installed casing and then moved the Grundoram to the north side of the road. There, crews welded a small section of .500 wall casing, a sacrificial pipe, to the back of the product pipe to facilitate the rammer. With the spoil cleaned from the bore pipe, crews were able to ram the product pipe in slowly without incident. Pumpco crews simply cradled the product pipe during the process with side booms and straps until it was completely installed. Once the installation was complete, Hill’s crew removed the bore pipe and the sacrificial pipe section and turned the project over to another Pumpco division to continue tying the line into the rest of the pipeline. The entire project took two weeks for set up and one week for ramming and welding.
Melvin said, “This was a difficult ram for sure, but the crews at Pumpco tackle this stuff everyday. They know what they’re doing and are prepared to face just about anything on these tough pipeline projects.”