Dallas excavators cut through rocks with Kobelco SK480
Trenching through solid rock is all in a day’s work for Choya (RB) Barker, superintendent of an excavation crew for Moss Construction Company Inc. in Wylie, Texas.
It’s hard on equipment and it’s slow work Barker says. It took his crew five months to open a 12,000-foot trench and install a 60-inch water line between two small cities on the north side of Dallas. However, he expects to be moving on to a similar, and longer, job before 2004 ends. It’s an $8 million water project for the North Texas Municipal Water District, laying more than 30,000 feet of 42-inch pipe.
Moss Construction specializes in underground utilities --- water, sewer and storm sewer – in a 100-mile radius of the Dallas metroplex. When Hal Moss incorporated the company in 1989, the staff consisted of him and just two employees. Fifteen years later, it has pipe-laying crews (about 150 employees in total), 17 excavators and contracts for about $30,000,000 in work to do.
The utility contractor’s fleet of Kobelco excavators today includes five SK480s, two SK400s and two 135SRLC zero-swing excavators.
Moss’s biggest project in 2004 was a $4.3 million infrastructure project for the City of Greenville. It was a trunk sewer main with 36-inch and 48-inch pipe. “That was probably the deepest and most difficult job we’ve done. We were working on it for about a year,” he says.
Whether it’s trenching in rock or building a company, Moss says, “There’s no real secret to it. We just keep hammering at it.”
Barker had 13 workers and five excavators on the $3.2 million Frisco-McKinney pipeline project for the North Texas Municipal Water District. They started at both ends in April and connected in the middle in September. The big poly-wrapped steel supply line averages 15 feet deep but plunges to 30 feet at some points.
The trenching sometimes had “good going” in dirt and sand. The crew could trench 600 feet on a day like that.
Other days, they were chipping through a blue stone that underlies the district. Bluestone is a variety of flagstone that is dense, hard and fine-grained.
“It’s real hard,” Barker says. “It’s layered, but it doesn’t break off in sheets. It chips out or breaks off in pieces. Some places, we’d have to cut through 20 feet of it. You might get 100 feet in a day.”
To a layman, Barker explains, the deep trenching job “looks like a trench inside a trench.” The excavator first digs a trench wide enough for itself to move into and work inside. Then it digs a second, lower trench for placing the pipe at whatever depth is needed. The lower trench usually is nine feet wide.
It’s a technique required for laying the pipe in place safely. A steel trench box also is required for protecting crew members as they join pipe at the bottom of the trench.
Moss Construction uses twin “Tiger Teeth” on the bucket for trenching in rock. With the weight of the bucket and arm behind the two sharp points, eventually the stone gives way.
“You just keep cutting through it and cutting through it,” Barker says. “You’re just scraping it. You just keep digging and digging and it’ll keep peeling off. It starts chipping away and next thing you know, you’re at the bottom where you need to be.
“It’s pretty tough. It’ll wear your equipment down. You go through a lot of fuel when you’re digging in that hard rock, and it’s harder on the machine.”
Barker has used both Cat and Kobelco excavators for this type of work over the past 10 years. He now prefers Kobelco.
“The Kobelco SK480 cuts rock as good as anything that I have ever used,” he says. Moss Construction purchased the first Kobelco SK480 to arrive in the Dallas area in 2001. Today, they’re gradually shifting over to Kobelco excavators.
The Kobelco SK480 excavator is the largest excavator that Kobelco offers in North America. It weighs about 110,000 pounds. It’s a bit heavier than the Caterpillar 345 and 40,000 pounds lighter than Cat’s 365.
Barker says, “Weight is important when you’re digging in rock. The SK480 will cut and lift as much as a Cat 365 will. It’s amazing that the SK480 will do as much as the Cat 365.”
He had three SK480s and two Cat 345s on the Frisco-McKinney job. Two 480s had the 16-foot optional arm for deep trenching (to a maximum 30-foot depth) while the third had the standard 11-foot arm.
For lifting power and cutting speed, Barker says, there’s no contest between the SK480 and the 345. “I’ve had them on the same jobs and had them dig side by side,” he says. “You can put in two operators that are pretty equal and, in ordinary material, you can probably cut 100 feet more a day with the SK480 than with the 345.”
Lifting and placing in a trench an 8 x 10-foot concrete box culvert is a good test for lifting power. When he needs the box culvert, he used the SK480 with the short stick to put it into position.
“The 345 won’t budge it – I was real surprised when I saw that. What I was surprised at was when the 365 wouldn’t pick it up with the long stick on it and the SK480 would—but the SK480 had a short stick on it. That makes a lot of difference in lifting power.”
Reliability is a third factor that’s important to Barker. “We work those backhoes, anywhere from 40 to 60 hours a week, year-round,” he says. “Nothing goes wrong with those Kobelco machines. You don’t blow hose and an O-ring. It’s just an all-round great machine.”
Reliability of crews and equipment goes hand-in-hand with being successful as the low bidder on municipal contracts. Kobelco machines are integral to that, says Moss.
“On a daily basis, a Kobelco excavator will out-perform a Caterpillar,” says Moss. “A Kobelco just doesn’t have that many mechanical problems. Any failures, or things like that, are very, very minimal. That’s what we like.
“We want something that will dig every day. We work an average of 10 hours daily, easily five days a week and a lot of times six. We’re probably pushing 3,000 hours a year on those machines.”
Reliability from the dealership is at least as important as from the machine, and that’s where Hal Moss believes the Kobelco name really shines.
“Their customer service at the Kobelco dealership is unbelievable,” he says. “If something breaks down, whatever it is, they’re there. They respond very quickly. They don’t tell you it’s going to be noon tomorrow or something. That’s very hard to find, and that’s one of the biggest reasons I’m fading Caterpillars out.”
The Kobelco dealer responds to a call, almost always, the same day. The equipment may be fifty miles away but “they respond quicker than any other dealership I’ve ever used for construction equipment,” Moss says.