Drainage on the Money
A GPS saves time for this drainage contractor.
Monday, February 28, 2011
By Daniel C Brown
Since 1975, the folks at Agrodrain Systems Ltd. have been installing drainage pipe in the farmland of eastern Ontario and western Quebec, in Canada. The company installs hundreds of miles of pipe each year over thousands of acres, and Agrodrain president John Wielgut wants to keep the drainage plow moving. In one pass, the plow cuts a slot and knifes drainage pipe into the ground. An average project takes one or two days; a weeklong job is a big one.
To gain production, Wielgut has discovered that using a GPS to automatically control the elevation of his drainage plow saves an estimated 10% to 20% of the time it took to do the job with laser controls. Before the firm bought the GPS, a foreman would set up a laser transmitter with a rotating beam that sent a continuous signal to a receiver onboard the drainage plow. If it was hilly ground, or trees obstructed views, a worker had to set up the transmitter many times, because the transmitter had to “see” the receiver at all times.
Now, with grade control using a PowerGrade 3D System from Leica Geosystems, the drainage plow can keep producing. There’s no stopping while the laser transmitter is moved. “On a bad job our man would spend a third of his time moving the laser transmitter around,” says Wielgut. “This GPS is far more productive.”
Design and Build
The drainage plow is a double-link plow pulled by a Caterpillar D8R tractor. The tractor carries a counterweight on the front and has been modified with 36-inch-wide track shoes. Prior to laying the pipe, a four-wheel-drive tractor and trailer with a hose reel lay out the high-density polyethylene (HDPE) pipe in paths parallel to its final burial line.
“Generally we install pipe in this area 3 to 4 feet deep and occasionally 6 or 7 feet deep,” says Wielgut. “We need to have a minimum of 2 feet of cover on the pipe to meet regulations. The pipe is corrugated plastic; laterals are 4 inches in diameter and collectors are generally from 6 inches to 12 inches in diameter.”
A power pipe feeder pushes pipe into the plow’s chute for burial. On hot days the pipe can become warm and is prone to stretch during installation, so the power feeder prevents the pipe from coming under tension as it enters the ground.
When Agrodrain approaches a new project, a surveyor uses a Leica Redline Power Antenna base station base station and a Leica Redline Power Antenna rover to survey the field. Using design software, the surveyor draws up digital plans in the office. “The plans are reviewed by the landowner, and after they are approved and any changes are made, we load it into the computer on the drainage plow,” says Wielgut.
 |
| Photo: istockPhoto/ ImageegamI |
“The GPS is designed for 3D drawings, but in a rush situation we use 2D drawings,” says Wielgut. “We calculate all of the grades in the office and make sure there are no issues with outlets or water capacities and the like. A lot of people will design it in the field, but we design in the office. That way all materials can be ordered beforehand, and we make sure we have the exact materials we need.”
Automated Depth
The Leica Power Grade 3D system automatically controls the plow depth, but does not steer the tractor. A display monitor in the tractor’s cab displays the unit’s position relative to the designed track line, so the operator steers the machine using that. “We generally can place pipe within one-quarter-inch of design grade,” says Wielgut. “We do a lot of our drainage at minimum grades, which for us is 1% or 1 foot of drop in 100 feet. That’s why vertical accuracy is very important.”
The drainage plow has two critical sensors that are connected to the plow hydraulics and improve vertical accuracy. One is a tilt angle compensator. If one track on the D8R is lower than the other one, the GPS will compensate and do an elevation correction.
The other sensor is a blade pitch sensor. “Especially in soft conditions it is possible for the leading edge of the plow to be on grade, but the back end of the plow, where the pipe comes out, can sink and put the pipe off grade,” says Wielgut. “To counter that, we have another sensor for the blade pitch. A double-linkage plow has two hydraulic cylinders. The main one is up front and controls the grade. The back cylinder is typically just put into float position, and the pipe chute follows the leading edge. But in soft conditions, we need to control that back cylinder, and that’s what the blade pitch sensor does.”
Wielgut has run the Leica Power Grade 3D system for about a year. “The overriding observation that I have is, it is so darn dependable,” he says. “We had a small issue with one cable one day last spring that we resolved, and we have not had a minute’s breakdown since then. It is a very, very dependable system and is much more efficient than a laser system.”
Wielgut says the GPS system is also more accurate than a laser. His laser system was adversely affected by the distance of the machine from the transmitter, by fog, and by the wind, because the transmitter had to be mounted high in the air.
Agrodrain also has a heavy construction business and can move the Leica PowerGrade 3D system to other earthmoving machines in the fleet. “It is very versatile for us,” Wielgut says. “I can put that system on our Caterpillar D6T, and most of the components can be used on our Hitachi ZX450 and ZX650 excavators as well. The excavators, of course, are not fully controlled by GPS. Only certain components are used, because it’s an “Indicate Only” system. We have a second D6 coming in a few days, and that will be a candidate for the GPS.”
In brief, Wielgut couldn’t be happier with his Leica PowerGrade 3D system. “It saves time, and it is dependable and accurate,” he says. “And you know that time is money for us, as well as for everyone.”
Author's Bio: Daniel C. Brown writes on safety and technology in the construction industry. |
Advertisement]