Pneumatic piercing tools offer an alternative trenchless method
for utility installations
Horizontal directional drilling (HDD) has quickly become the preferred method of the underground construction industry. Travis Fields, owner of the Mole Inc., isn’t afraid to say his favorite project doesn’t utilize HDD at all. Instead, it was when he introduced Hole Hammer pneumatic piercing tools to a client.
The client was a major power company that was almost exclusively using horizontal directional drills and trenchers. It had trouble installing a secondary electric wire to a home in North Carolina, so it called in The Mole Inc. to find a solution.
Advocating for an alternative method
The Mole Inc., crew tackled it with a pneumatic piercing tool, which is a piece of trenchless equipment propelled through the ground with compressed air. It is cost effective, easy to use and ideal when ground disruption must be minimal or even nonexistent, such as under landscaped areas or concrete.
The North Carolina job fit that criteria. The electric line ran 195 feet total, the first 100 feet was level with the road, and then it dropped straight down 30 feet. That’s where things got interesting because a large wall, decorative stones, a swimming pool and sections of concrete all stood in the way.
The crew dug into flower beds to access the pneumatic piercing tool and bored flower bed to flower bed, about five in all, until they reached the electric meter on the house. They were pulling four cables wrapped around each other, three of them three-quarters of an inch in diameter and the other a half inch.
The Mole Inc. got the job done without a hitch, and the power company executives were impressed.
“They had never seen anything like this done,” says Fields, job coordinator for The Mole Inc. “They were surprised when we got done and we were able to clean everything up so that you couldn’t really tell where we worked.”
The majority of the time, Mole Inc. selects Hole Hammer pneumatic piercing tools as its preferred method. With HDD all the rage, some may wonder why a crew would choose a piercing tool. Fields lists a couple of advantages.
For one, it’s getting more and more crowded underground with infrastructure. Fields has found there to be more maneuverability with a piercing tool to go up and down and laterally to avoid existing utilities.
“With a drill, you pretty much have to shoot under things,” he says. “Out here, everybody else has already thought about shooting under things, so chances are, if you’re going under something, you’re going to run into something else.”
Pneumatic piercing tools are powered by an air compressor. The pneumatic power drives a striker inside the tool forward at a high velocity, and the striker impacts an anvil at the front of the tool, pushing it forward and displacing soil to create the hole for the product to be installed. Many models can be placed in reverse if they become stuck or go off course.
Also, piercing tools leave less of a mess and usually have a smaller footprint than drilling. HDD jobs require managing drilling fluids. Drills also need a certain amount of setback from where the drill string enters the ground. With a piercing tool, by contrast, the operator typically steps into the entry pit to launch the missile and into the exit pit to retrieve it. McLaughlin recommends that the depth of an entry pit be approximately 10 times the piercing tool’s diameter, and all of its models are less than 4 inches in diameter. Exit pits are slightly larger.
‘Missles’ should be more popular
Fields says awareness of pneumatic piercing tools is not very high in the underground construction industry. This can be seen in bid documents, which Fields says usually have a trench price and a horizontal directional drill (HDD) price with no natural fit for a pneumatic piercing tool.
“I don’t think they’re as popular as they should be,” he says.
The piercing tools are commonly called “missiles” because of their shape. For example, the model The Mole Inc. uses the most is 2.5 inches in diameter and just over 4 feet long — and yes, those dimensions and its black color make it closely resemble a projectile.
The length of the shots are shorter compared with a horizontal directional drill. Fields says The Mole Inc. doesn’t go longer than 80 feet. But through a method known as stitch boring, a pneumatic piercing tool can be used for a series of shots to cumulatively go farther. In stitch boring, pits are spaced at intervals — every 25 to 50 feet is a common approach — that allow the tool to complete longer jobs for all kinds of products, including electric, fiber, gas, water and irrigation.
For more information about McLaughlin piercing tools and other products, visit mclaughlinunderground.com or contact your local Vermeer dealer.