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News
Aggregates Manager 2001
Luffing Jib Bucket Dredge Fits Small Ohio Operator
Oscar Brugmann Sand & Gravel Co., Mantua, Ohio, has been a family affair for 93 years. Owner Roy Brugmann is the son of founder Oscar, and Roy's son, Alan Brugmann is foreman at the company's main sand and gravel site in Mantua. Of the 13 employees working at three sites - all within five miles of each other - nine employees are members of the Brugmann family.
The Mantua, Ohio, operation is located between Cleveland and Akron, Ohio (about 35 miles from each), and about 12 miles west of Kent State University.
"We do most of our business toward Cleveland," said Alan Brugmann. "Our biggest customer is Medina Supply, which is a concrete contractor we sell bulk sand to."
In the past few years, Oscar Brugmann has also moved into specialty sands, most notably golf course greens sand - a higher margin product for utilization of finer sands.
The company started a mile up the road from its current site, mining with a dragline for about 25 years. The company purchased an 8-in. diameter suction dredge it used at its original site, and then moved to the current site. The suction dredge, however, didn't make for a good fit for the sand and gravel deposit, which has a lot of larger-sized rocks and boulders.
"You could only get 6-in. rock through the pipes, and it was constantly plugging," said Alan Brugmann. "It was too much pump upkeep, so we sold it about 15 years ago."
The company since that time had been extracting with a dragline equipped with a 7-cu. yd. bucket.
As the operation expanded, and the remaining deposit fell below the water table, the small dragline could no longer keep up with demand. The rocky deposit was also tough on the machine, making it difficult to bring up a full bucket, and at worst case, the bucket would hit a boulder, flip and bring up nothing.
As the deposit went deeper and production demands grew, the company decided to invest in a clamshell bucket dredge, which began operating in March 2000.
The dredge uses a luffing jib design equipped with 6.5 cu. yd. bucket - the largest sized bucket you can use on this type jib. Brugmann went with the design for two main reasons: the dredge is small and easier to disassemble than gantry-style dredges (the company will eventually move it to one of its nearby sites) and comparable gantry-style dredges cost about a third more.
The dredge will dig as deep as 150 ft., but according to Alan Brugmann, the deposit goes only about 100 ft. deep. Brugmann expects to operate the dredge at the site for about 10 more years.
Still the deposit is a challenge to extract due to the oversize. Brugmann did not opt for an on-board crusher, but it is an investment it may make down the road, according to Alan Brugmann.
Oversized material (plus 8 in.) dumped from the bucket over an 18-ton capacity hopper, is pushed off the grizzly screen by a rake assembly. A chute guides the material into a barge capable of carrying about 20 tons of rock. A small tugboat equipped with a 130-hp motor moves the rock barge to the shore, where an excavator removes the material, which is crushed to 6 in. and sold as base. Boulders that are granite-like are sold for landscaping.
"Some days I'll get 40 tons, some days I'll get over 100 tons of oversize. Right now, I average about 60 tons a day in an eight hour shift," said Alan Brugmann.
The dredge can produce up to 325 tph, but given the challenge of the deposit, the dredge's production tops at about 275 tph, according to Alan Brugmann.
The dredge hopper feeds a 6-ft. x 6-ft. double deck dewatering screen. Passing through the screen is 1-1/2-in. material, and passing through the bottom deck is minus 1/4-in. material.
Fine sand can drop through the screen and be funneled back into the lake, but Brugmann installed a fine sand receiving system. Sludge is pumped to a small Krebs 15-in. diameter cyclone with a 4-in. diameter outlet, which feeds the material onto a 1,700 rpm high frequency dewatering screen, which outlets to the conveyor.
The fine sand through to the 8-in. stone is transported to shore by a system of three 100-ft. Rohr Series II floating conveyors, equipped with 30-in. wide belts. As the lake gets bigger, Brugmann may need to buy additional floating conveyor.
An hydraulic pump controls the jib, which moves back and forth from the hole where the bucket submerges to the hopper. Another hydraulic pump controls the doors beneath the hopper.
The variable speed hoist uses a DC drive system (equipped with a WEG motor). The whole plant is powered by a Caterpillar 3412 generator set, which more than meets its 500 hp needs. If Brugmann decides to add a floating crushing system to the dredge, the plant will still be able to run off the Cat unit.
To steal a line from Oldsmobile: this is not your father's clamshell dredge. (For Alan Brugmann, though, it is.) Computer diagnostics on-board and a patented bucket monitoring and diagnostics system improve efficiency, guard against major downtime and help increase the operation life of components.
Strategically placed proximity switches control the jib movements. As the jib passes by the "proc" switches, they trigger it to slow down, move 2 ft. back from the hopper and stop in the position ready for digging. Proc switches are on conveyors and other key components, which feed signals to a PLC equipped with a Windows 98 compatible custom program developed by Rohr.
The proc switches provide logic control of the dredge. For instance, when the bucket opens above the hopper, the sensors tell the computer to shut the gates beneath the hopper. The gates can be programmed in 0.10 second increments to tailor its automatic mode, which shuts the gates for one second and opens the gates for 2.6 seconds, to better fit the type of material being handled.
The monitoring system, which consists mainly of Allen-Bradley and Siemens components, also check oil temperatures in the bucket and engines, motor temperature, of if water seeps into components of the bucket, for instance. The system not only preserves equipment life, but it also makes for a safer operating dredge.
Perhaps, the most useful monitoring system for Brugmann given the tough deposit it digs, is the bucket monitoring system. Bucket sensors provide a computer image of the bucket when it is submerged. From the screen view, the operator can see if the bucket is opened or closed and see, from the position of the bucket, how best to maneuver it.
The bucket monitoring system was one of the first installed on Rohr dredges in the United States.
"The monitoring system is a great thing," said Alan Brugmann, who works just one operator on the dredge (usually himself or his cousin). "It does everything I expected it to do."
Another notable quality of the dredge is that it operates quietly. "The only noise you hear from the dredge is a hum when the bucket opens and shuts, and our generator is on shore, about 300 ft. away, depending on our position on the lake," he said.
Material for the main processing plant is hauled from two nearby sites in addition to the dredging operation. In all, Alan Brugmann says the main plant produces about 500,000 to 600,000 tons per year. With the clamshell bucket dredge, the company is able to go deeper into its deposit to significantly extend their lives.
The bottom line...
Oscar Brugmann Sand & Gravel, in Mantua, Ohio, acquired a Rohr 6.5-cu. yd. luffing jib design clamshell bucket dredge to excavate deeper into its reserves below the water table. The smaller dredge was more economical and will allow for easier transport to a new site. Also, a patented Rohr bucket monitoring system assists in providing feedback on underwater bucket position and movement to improve dredging performance in this challenging deposit.
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Rohr Corporation
http://www.rohrcorp.com
ROHR Corporation, 6295 Dry Fork Road, Cleves, OH 45002
Tel: 513-202-0800 Fax: 513-202-0888 Email: info@rohrcorp.com