Jan 1, 2008 12:00 PM
BY ADAM MADISON

Rick Goessling and Virgil Cooley

Rock Products-January issue

At Welch Sand & Gravel, draglines are rusting away in small equipment graveyards and are threatened by extinction as new technology prevails. Decades ago, these mechanical beasts were a common necessity. But today five hibernate, slowly being overcome by weeds, on the yards of Welch Sand & Gravel, as the company moves to more efficient and less burdensome methods for extracting material.

Welch is a family-owned operation serving the Cincinnati area. There are four operations all together and none are dependant on draglines any longer. Today, Welch's Bucyrus, Manitowoc and Northwest draglines just sit on the sidelines as their clamshells scoop out material from the bottom of the ponds.

Production Superintendent Rick Goessling says draglines still can be an important component of a small operation producing around 50,000 tpy. But they are no longer cost efficient for an operation of Welch's caliber. The company consistently ranks as one of the largest sellers of sand and gravel in the state of Ohio. Their Ross Plant alone produces 750,000 tpy. The amazing thing is that this is done with only two operators from the dredge to the stockpile.

Four of the five draglines are still in good working order. The company continues to perform annual maintenance on them just to keep them running with hopes of selling them off. But potential buyers just shake their heads at the sight of them.

“You can hardly give them away now. Nobody wants to use them,” Goessling says. “You can't find anybody to work on them and nobody wants to run them.”

Welch Sand & Gravel uses a Rohr clamshell dredge, which greatly enhances the operation and yields up to 700 tph.

DREDGING

Dredging has proven to be a much more efficient method of production for three Welch operations. They now utilize a 13-cubic-yard Rohr clamshell, a 7-cubic-yard Rohr clamshell and a 8-cubic-yard luffing jib dredge.

The 13-cubic-yard clamshell is the foundation of the company's Ross facility, serving the Cincinnati market. Virgil Cooley, Ross plant foreman, says this mammoth machine weighs in at 600,000 pounds. It can produce as much as 700 tph and can reach 200 feet below the surface.

New Life for an Old Operation

Virgil Cooley has more than 25 years of experience working for the aggregates industry. He started at Welch Sand & Gravel four years ago when he joined the team to operate the 13-cubic-yard Rohr clamshell dredge. He was later promoted to plant foreman of the Ross Plant. Prior to Welch, he worked for the black-top industry and as a dragline operator for another sand and gravel company.

Rohr continues making machines bigger and bigger. It has produced clamshells with buckets as large as 20 cubic yards, and in some instances they have actually bolted machines together in order to run tandem and double production.

For Welch, this dredge was a $3.5 million investment, and each floating conveyor was $150,000, Cooley says. But it is paying off both in production output and fuel costs. The entire machine is electric, unlike its dragline ancestors, so it is more environmentally friendly. Cooley says there are 36,000 volts coming in off the street, which is reduced to 12,460 volts at a step-down transformer. And another step-down transformer onboard reduces it to 480 volts.

The clamshell takes large bites from 100 feet every 90 seconds and dumps into a hopper. Above the hopper is a 6- × 8-inch horizontal grizzly. As material sticks to the grizzly, it is raised by a hydraulic lift to dump the oversize. Often there is a barge waiting below to collect the material and take it to a waste pile on shore. Other times it just goes back to the lake.

Below the hopper is an 8- × 20-foot polyurethane dewatering screen that was built by Metso Minerals. Dried material is discharged onto a conveyor for transport to shore. The undersize falls through and into a smaller “possum belly” hopper that is actually submerged. A 6- × 48-inch Galligher pump inside moves this material to a 20-inch Krebs cyclone to remove the fines. The dried material is then blended onto the conveyor and heads to shore. Welch has the option of shutting this pump down, allowing the fines to wash back into the lake. It just depends on what gradation the customer wants, Cooley says.

The floating conveyors connect to an onshore stacker, which also is controlled by the dredge operator, to supply the feed hopper to the plant. The stacker also can be repositioned to create a stockpile. This way the dredge can continue producing material while maintenance is performed on the plant. Or if the dredge is in need of maintenance, the plant can be fed stockpiled material by wheel loaders. Occasionally, the company is lucky enough to sell bank run that also is sold from this point, Goessling says.

The hopper also marks a break in responsibility. Goessling says everything before the hopper is controlled by the dredge operator and everything thereafter is controlled by the plant operator in the control tower.

The automation system on the dredge is highly sophisticated, and the PLC monitors every activity taking place. The conveyor knows if a conveyor stalls, if a screen motor stops running, and where the trolley is on the overhead gantry at all times. All of this information is used to ensure that all parts are working in proper sequence, and if something was to fail, everything else would shut down accordingly.

The Plant

There is no PLC (programmable logic controller) on the plant, but all wiring is interlocked. And a particular startup sequence must be followed. So, before the crusher starts, the conveyor before it has to be running; and vice versa. Although this is less sophisticated, the system works well.

Most of the plant consists of equipment taken out of an older plant on site that was moved to reach reserves. Heavy maintenance also was required, as were some modifications to better accommodate the slurry from the dredge. This included the addition of pleated belts on a couple of the incline conveyors to help move material up to the feed boxes.

“Everything was reworked,” Goessling says. This included dismantling the old plant, preparing the new location, transporting it and re-engineering it. Most of the fabrication was done in house and so was a lot of the electrical work. Overall it was an eight-month process that required the help of six or seven of their best employees.

This plant, from the perspective of the control tower, begins at the feed hopper, a 6- × 16-foot Allis Chalmers. It is a triple deck, but typically only one screen is used. The oversize feeds a APK-30 Hazemag rotary impact crusher. This crusher handles about 50 tph of material.

This and much of the other equipment on the plant is more than 20 years old. And much of it will likely live to see another operation as reserves are exhausted in about 15 years. It's all about good maintenance.

For the crusher, blow bars are rotated every 200 hours. Typically, four rotations are achieved before replacements are needed. Wear aprons generally last one season and are replaced during the off season.

The crusher's feed conveyor is equipped with a metal detector to remove tramp iron. When metal is present, a brake motor automatically stops the material flow, reverses and dumps the metal onto the ground. Goessling says old dragline teeth, nuts and bolts, as well as angle iron are common.

Moving Material

Crushed material is conveyed to a different screen; oversize is rejected. The crusher is on a closed circuit and produces a state-spec 304, which is provided to road and paving contractors. Goessling says this compactible material also is good for gravel roads.

Rick Goessling began his career in diesel mechanics with the U.S. Marine Corps. His first civilian job was working as a mechanic for Cummins in Cincinnati. In 1981, he was hired by Welch Sand & Gravel as a diesel-engine mechanic. Over the course of 26 years, he has climbed the ranks of the company to his current position, production superintendent.

The undersize is transferred to an 8- × 20-foot triple-deck wet screen, which separates 57s and 8s. Material is washed with 2,600 gpm from the lake. The grits, a small pea gravel blended with a coarse sand, and the concrete sand is the undersize that is discharged into a twin 44-inch Greystone dewatering screw. A slurry pump for the weir water takes material to a 20-inch Krebs cyclone, which is where the fine brick sand is removed.

“Material is untouched by any equipment other than the land conveyors,” Goessling says. “And it is falling onto the ground as finished product.”

This was a big step in the right direction, as the last plant relied heavily on haul trucks to move material. It also eliminated load cranes and at least two wheel loaders from the process. This means considerable savings have been made — cutting costs in fuel, tires and manpower. Also, the entire property has already been stripped of its overburden, further degrading the need for draglines and scrapers.

The stockpiles are the first point where mobile equipment enters the process. All material is loaded with wheel loaders. And trucks follow a simple loop in and out of the plant. Goessling says this also was a marked improvement over the old plant. Before the new design, trucks had to drive clear across to the other end of the property and return to the Thurman scale by the same road.

Welch owns and operates its own dump trucks but also contracts out to other trucking companies. All dispatching is done over the phone from a central office, and a scale operator waits with a ticket as truckers exit. Welch services the entire Cincinnati area, spilling into portions of Indiana and Kentucky. This includes natural concrete and mason sand, and base materials for various construction projects. Much of the material is now being used for commercial developments.

Welch and all other sand and gravel operations in the area continue to suffer from a deflated housing market. Some of Welch's competition has shut down operations to wait out the storm. Goessling says the company has been able to keep its gates open because it has no stockholders to answer to. “So when a hard time like this hits, we can just ride the storm out,” he says. “We know it's going to pick back up.”

“When we bought the first clamshell dredge, they gave me the responsibility to erect it and learn how to work on it,” Goessling says. “Then I inherited the gravel plants and we fixed bottlenecks to increase production.”