Attempting to install sewer laterals, deep water lines or gas lines in urban areas may not be possible with a traditional surface horizontal directional drill (HDD) rig. The setback space required for the drill to reach the target depth may not exist. Applications where you need to install product under an existing roadway often face the same space constraints.
“There are cases where you do not have the setback or the easement to set up a small utility-sized HDD rig, such as the Vermeer D8x12 HDD,” said Dave Gasmovic, business development manager at Vermeer MV Solutions.
A productive alternative comes in the form of the pit launch drill. These niche HDD rigs are lowered into a pit and can drill from point to point without the setback necessary to achieve the target grade.
“The pit launch drill is designed to go where you cannot set up a surface drill,” says Gasmovic.
This type of drill can also be efficient in specific applications, like drilling across a road. By setting the drill in a pit and drilling point to point across the road, you reduce the drilling distance.
“It can be efficient from a standpoint that you are not putting a lot of extra pipe in the ground, and you don’t have to find a space to put the drill,” said Gasmovic.
Sewer, water and gas line return installations are natural applications for a pit launch drill. You can dig down 6 or 7 ft and drop the drill into the pit. Of course, you must also consider the proper shoring equipment when working in these holes. The pit launch drill is typically used to install a 4-in. pipe, but it can handle larger diameter products.
The pit launch drill is designed with a cutout in the front plate that will allow it to pull a 12-in. reamer back into the machine. With a 12-in. reamer, a 10-in. pipe is the largest diameter product pit launch drills are usually designed to install.
Pit launch drills have many similarities to surface HDD rigs. They use a standard locator-transmitter beacon, horizontal directional drill head and HDD tooling.
“You can use many of the same tooling with a pit launch operation that you use on a surface drill job. You’ve got a slanted face drill head. You have a mud pump system. You’re using a drilling fluid,” said Gasmovic.
It takes longer to install a service with a pit launch drill than with a surface HDD rig. This increased time is due to the required preparation, including digging the pit.
The performance of the pit launch drill is tailored to its close-quarter mission; 200 ft is the maximum distance for a practical pit launch application. This can be attributed to the shorter drill rod lengths.
“A pit launch drill either uses a 4-ft rod or a 28-in. rod,” said Gasmovic. “It takes just as long to makeup and break out a 4-ft rod as it does a 10-ft rod. These drill rods need to be hand loaded on the pit launch drill. So, if you can use a surface drill to go farther, you want to do that.”
Slurry management also requires a different approach for a pit launch drill than a surface HDD drill rig. While both types of drills require slurry management, the pit drill is sitting in the same hole where the slurry is returning. It’s ideal to have a trash pump or vac system on hand.
Versatile Set-up Options
A hydraulic power source provides power for a pit drill. The source can be a mini excavator, a mini skid steer, a loader backhoe or a hydraulic power pack as long as it can deliver 18 to 20 gpm of hydraulic flow at a maximum of 2,500 psi of pressure. However, the best power source for the job depends on your approach. Crews can position these power sources where there’s space on the jobsite. Then, the hydraulic lines run down into the pit to power the drill.
“Using a mini excavator may be more economical because you are not buying a dedicated hydraulic power pack,” explained Gasmovic. “But, some contractors prefer keeping the mini excavators busy doing other work instead of powering the drill.”
You also have flexibility on where you place the mud system when working with a pit launch drill.
“The mud system has a pump on it because most pit launch drills do not have a pressure pump like a surface drill,” said Gasmovic. “They are designed without a pump so they can be as compact as possible.”
Another Tool in the Box
Even though it is a niche product, the pit launch drill continues to gain popularity.
“We are seeing more pit launch drills used in the field today than in the past,” said Gasmovic. “Contractors who perform sewer, water and gas line installation in crowded urban environments or cross roadways with limited access may want to investigate the benefits of the pit launch drill. It just adds another tool to the toolbox. You can have something to do your laterals efficiently and pairs well with the rest of your equipment.”