Change of face
July 1, 2007 By: Rodney E. Garrett Pit & QuarryA New York producer looks to increase production by changing the main loading vehicle to a large-capacity wheel loader.
Different types of equipment can be used to remove shotrock at the quarry face. Generally, the digging and loading of the blasted rock is carried out by wheel loaders, front shovels or hydraulic excavators. Wheel loaders are the most popular type in use. Methods typically used to transport the blasted rock from the face to the primary crusher are conveyors or rigid-frame, off-highway trucks. That said, some stationary primary crushers or portable crushing plants are close enough to the quarry face and rock pile that wheel loaders are used to feed the crusher directly.
Occasionally, a quarry will change the type of loading equipment used to handle the blasted rock at the face for improving cost-effectiveness and production efficiency. Such are the circumstances at the Carver Stone Products quarry, part of Carver Sand & Gravel LLC. The Carver Stone Products quarry, Middleburg, N.Y., is one of the company's three quarries and four sand and gravel pit facilities that serve a 3,600-square-mile area in eastern New York.
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At Carver Stone Products, 12 calcitic limestone products are produced, including some NYSDOT-specified crushed stone sizes. Additionally, it supplies farmers with spreadable fine-mesh limestone for raising the pH in soils used for growing agronomic crops.
Excavator was used
Until recently, the tool of choice for loading rock at the face has been a hydraulic excavator. It loaded the rock onto two 50-ton-capacity rigid-frame Euclid and Terex off-highway trucks. The main reason for using an excavator at the face was to sort out the oversize rocks from the rest of the fragmented rock. Later, at another part of the quarry, either the oversize rocks are reduced in size by using a breaker mounted on a hydraulic excavator or they are sold as-is to be used as riprap or for other large-stone applications. "We do a nice business in selling large rock. In fact, last year we had a high demand for the rock," says Carver Laraway, president of the company.
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Here is an overview of the quarry operation to gain a perspective on how the blasted rock is handled from the face to the crushing/screening plant, and finally how the finished rock products are loaded onto delivery trucks:
The site has two bench levels with the top bench having an 80-ft. high face and the bottom bench having a 40-ft. high face. Drilling and blasting activities are carried out by a third party. The blasting is done every two weeks (10 working days), and the blast patterns are designed so each blast creates 50,000 to 55,000 tons of fragmented rock.
That quantity of rock coincides closely with the primary jaw crusher's throughput of 5,000 tons per 9 1/2-hour day. Usual crushing-time starts at 7 a.m. and stops at 4:30 p.m., as does the loading of the fragmented rock onto the trucks at the face. However, since the end of May, both the daily crushing and loading times have been increased by one hour in order to meet increased customer orders.
 From left: Matthew H. Mattison, Mine Safety and Health inspector; Blake Sowards, quarry superintendent; and MSHA inspector Ronald D. Ward. |
New wheel loader
While the excavator's production capacities are sufficient in sorting the rock sizes and loading the trucks, the process is problematic because the large rocks have to be piled within the limited dumping reach of the excavator's bucket. Another downside is that it takes eight to nine passes to load a truck compared with only four passes needed with a newly purchased Kawasaki 115ZV-2 wheel loader.
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