Rock Products January Issue 2008-by Adam Madison

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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

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 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.