Screening at Carmeuse operations

Operating 24/7 at peak performance, season after season, requires dedicated teamwork, top-notch maintenance strategies, and tough, heavy-duty processing equipment, especially when dealing with abrasive mining applications.

“Safety and reliability is our biggest focus,” says Richard Gray, a veteran project manager for the Kentucky-based Black River and Maysville mining operations of Carmeuse Lime & Stone. With more than 150 years in business and a total of 28 production facilities, Carmeuse produces high calcium and dolomitic lime, chemical grade limestone and crushed aggregate products.

The Carmeuse Black River and Maysville facilities are underground limestone mines with lime calcining and hydrating plants on the surface. Both are located near the Ohio River, where processed lime is loaded daily on barges. The Maysville operation is the larger of the two mines, and at 3 million tpy, it produces more than any other Carmeuse lime plant in the United States.

From the cavernous room-and-pillar mine at Maysville (located 250 ft. below sea level), raw limestone is fed into the crushing circuits. The crushed material is transported up through the mine shaft and conveyed to a surge pile before being fed to surface scalping and screening circuits that size and/or wash kiln feed and crushed stone products.

It takes two tons of kiln feed to produce one ton of lime, which is calcinated in five massive kilns (at temperatures up to 900 degrees) to produce quicklime, a high-purity product manufactured for steel making, flue gas treatment, water treatment and construction.

From the crusher feed, to surface scalping, sizing and washing, the processing circuits at the Black River and Maysville mines feature vibrating screens and feeders manufactured by Deister Machine Co. From the beginning – when the mines were initially developed in the early 1970s – Deister equipment was in place, with some units operating for decades.

Gray likes that he can easily alter the speed and stroke of the Deister screens for greater g-force.

“Unlike conventional screens I’ve operated, the Deister units allow us to safely maintain optimum operating conditions at higher g-forces for a far longer period,” he says.

Specifying for efficiency

Over the last four years, Carmeuse has upgraded its Kentucky operations with the addition of three new vibrating grizzly feeders and six new vibrating screens.

When specifying and servicing screening and feeding circuits, Gray and his team work closely with Process Machinery Inc., a full-service dealer headquartered in Shelbyville, Kentucky.

“We assist the Carmeuse operations with engineering services and a dedicated service team that focuses on a broad range of processing equipment,” says Dawson Horn, Process Machinery senior sales manager.

Horn explains that each of the mines operate a variety of screens, which include heavy-duty 6-ft. x 16-ft. double-deck, inclined washing and rinsing screens that remove fines from the limestone; 6-ft. x 16-ft. double-deck screens that size asphalt aggregate and dewater manufactured sand; and extra-heavy-duty 8-ft. x 20-ft. double-deck and triple-deck units.

“The 8-ft. x 20-ft. screens are scalping and sizing screens that efficiently process the kiln feed. The oversize is circulated back to the crushers, and then material is sized to a large and small kiln feed, and a 1/2-in. aggregate product,” Gray says.

Each of the Deister screens specified for the mines features a vibrating mechanism located between the decks. This mechanism is designed to produce a uniform, true circle movement of the vibrating frame and screening surface. The two shafts of the dual mechanism are individually motor-driven, and the timing belts prevent any non-synchronous motion.

Horn stresses that each Deister screen is designed with an “exclusive Slingermist lubricating system” that allows the units to operate at higher speeds and at lower operating temperatures.

Additionally, Horn says that each is plumbed to access the Deister System Saver component, which reportedly extends the life of the antifriction bearings in the Slingermist system.

“The System Saver filters out the contaminants in the lubricating oil, so that operations can prevent costly bearing replacements and reduce downtime,” Horn says. “It extends oil change-out intervals by filtering the used oil – without exposing the oil to the open environment.”

Controlling crusher feed

Two Deister 56-in. x 24-ft. vibrating grizzly feeders are located at the Maysville operation, and one is installed at the Black River mine. According to Deister engineers, the underground vibrating grizzly feeders at the mines combine scalping and feeding in one operation. The feeders provide a continuous, controlled flow of material to the crushers.

Larger material is scalped into the crusher, while undersized material passes through the grizzly bars, bypassing the crusher. This relieves the load to the crusher, and ultimately increases crusher capacity and efficiency, says the manufacturer.

Engineered with heavy H-beam cross members, a heavy-duty vibrating frame and specially designed coil springs, the grizzly feeders are designed to absorb impacts and loading stress. Manganese steel grizzly bars are individually mounted for adjustability and ease of replacement. As the bars are bolted on, changes in product size can be handled by simply respacing the bars.

“Installing the underground feeders at the mines is one of the most interesting and challenging aspects of the upgrades,” Horn says.

He explains that Deister assembles the feeders and tests them at the factory. Then they are taken apart and shipped in smaller pieces of componentry, so they can be secured and transported down the mineshaft on a slope-car rail system before being reassembled underground for operation.

Horn also notes that the specified feeders are identical in size. Each is engineered with the same bearings, springs, motors and drives.

“This is a huge advantage,” he says, “as it minimizes the volume of parts inventory required.”

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Carol Wasson is a veteran freelance writer for the aggregate and construction equipment industries.