Knowing the accurate location of the drill tool once it’s below ground is pivotal to completing the job on target and on budget. Unfortunately, one thing often gets in the way of this accuracy and that’s interference, both passive and active. In addition, some jobsites are more prone to a certain type of interference as was the case late last year when TH Construction tackled a series of bores for Cargill Food Distribution in San Antonio, Texas.
RELATED: Directional Drilling: HDD Locating Systems Improve As-Built Data
TH Construction is headquartered in Nebraska, but its crews have traversed the United States completing HDD projects for 20 years oftentimes landing challenging projects that other contractors avoid or already failed at completing.
Through these travels, TH Construction owner Tim Huttmann knows how important speed and accuracy are to getting a job done. The more pipes installed the greater the profit and a contractor can’t be fast without being accurate, so he knows the important role the locator plays in a project.
This project had the HDD crew putting the new Falcon F5 locating system from Digital Control Inc. (DCI) through its paces, and Huttmann was pleased with the results of the prototype locating unit. The Falcon F5 brings locating to the next level of measuring and dealing with interference.
The month-long job in San Antonio brought heating under Cargill’s deep freeze cold storage building used to house meat for the state’s meat packing industry.
RELATED: ICUEE 2015 Day 1: Trenchless Technology Recap
“Cold storage warehouses are predominately troublesome areas for interference and you never know until you get to the jobsite how much interference there is,” says HDD industry veteran Brian Mattson, national accounts manager at DCI. “We’re talking both active and passive interference. The two interferences are completely different and they really cause a lot of trouble for all locating. The new Falcon is helping to eliminate a lot of that noise.”
In addition to varying soil conditions, crews also had to contend with boring under a private rail spur and a ditch before getting under the building to deliver the electric heating system. Underfloor heat is critical to the operation of cold storage warehouses because the manufactured subzero temperatures inside are not contained by the concrete slab floor and go beneath the surface.
“The cold temperature inside drives the frost down below the building and causes the floors to heave. When the floors heave, the roof almost mirrors it, so if you have a wavy roof, the floor is probably the same way,” Huttmann says. “We installed an underfloor heat to normalize the floor temperature to a normal level.”
In this instance, the heaving was not the cause for the project; rather Cargill expanded the facility, which required an update to the underground heating system. That is where TH Construction, its Vermeer D36x50 and the DCI Falcon F5 with Aurora display came into play.
“I first saw the unit in Louisville [ICUEE 2015],” Huttmann says. “Our Vermeer rep talked to us about the new Falcon system coming out and I figured we would see how it works.”
This was not Huttmann’s first foray into the DCI world. The company has 16 rigs and of its locating systems, 15 are DCI systems. He praised the new Falcon F5 for its similarity to the F5 and Eclipse models in terms of layout and controls.
Where he saw the Falcon F5 come out ahead was in terms of how it handled the interference. With cold storage building projects — the infrastructure needed to retain the below-freezing temperatures coupled with the rebar in the floors — interference is a given. According to Mattson, when working in cold storage buildings, the environment lends itself to the locating signal becoming sporadic and the contractor is never sure where the drill head is.
“It took away a lot of the interference, which allowed us to be more accurate, so we could increase our drill speed,” Huttmann says. “I felt comfortable knowing where our drill head is. With our older systems, which are all DCI units, you would get a lot of ghosts. With the Falcon system, it took a lot of that away. We still had some [ghosts], but not nearly as frequent.”
Enter the Falcon
The Falcon F5, as well as the Falcon F2, measured interference over a wide frequency spectrum – 4.5 to 45 kHz – and from there, the system gives the operator several optimal frequencies where interference is the lowest.
On this job that capability translated to Huttmann and his crew shaving about one to two hours off of their day — approximately 60 hours total — compared to similar jobs, in like conditions, using the older systems.
“You have to bundle up because it’s cold, cold, cold. Outside in San Antonio it was 50 to 70 degrees but when you go inside it’s 20 below zero,” Huttmann says. “It gets hard on a worker and you bundle up big.”
RELATED: Innovations Drive Industry Growth – New Installation
The worker may have been bundled up, but the locating equipment was not. This was a surprise for Huttmann, who notes that with older systems he would have to devise an insulation plan to keep the ball-in-the-box from becoming jelly-like. Another side effect of working inside a cold storage unit is losing the signal between the rig operator’s interface and the locator. Neither the jelly-like issues nor loss of signal occurred on this job.
“To have more of that pinpoint accuracy, getting closer and closer to a wireline system, helps you get through those difficult bores. It gives you the right tool for the job,” Huttmann says. “Some [older systems] would be a foot to 16-in. off and that makes a huge difference when you are steering. This improved technology is vital to everything that we do.”
In all, the TH Construction crews completed 44 bores at an average of five per day, pulling in 1.25-in. pipe, totaling 300 ft in mixed soil conditions. In addition to locating concerns, the crews also contended with a ditch and private rail spur outside of the building and the rig was setback 60 to 90 ft from the building to achieve the proper depth for the heating system, which is about 3 ft under the cold storage floor.