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
method for extracting material.
Welch is a family-owned operation serving the Cincinnati area.
There are four operations all together and none are dependent
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.”
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
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-x 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– x 20-foot polyurethane dewatering
screen that was built by Metso Minerals. Dried material is
discharged into a conveyor for transport to shore. The undersize
falls through and into a smaller “possum belly” hopper that is
actually submerged. A 6– x 48-inch Gallagher 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 monitor 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.
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 of seven of their best employees.
This plant, from the perspective of the control tower, begins at the feed hopper, a 6– x 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
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
The crushers 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.
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.
The undersize is transferred to an 8– x 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 material for various construction projects. much of the material is now being used for commercial developments.