Selecting the right size and type of screen improves the overall success of an aggregates operation.

by Leon Luadzers

The proper sizing and selection of a vibrating scalping screen is critical to the success of most aggregate and mining processing plants. In general, vibrating scalpers improve the overall performance of the entire processing plant, including crushers and other vibrating screens.

Since conducting research on this subject 21 years ago, my vibrating scalper sizing formula has been incorporated into popular aggregate-flow computer programs, making it easier to size vibrating scalper screens. However, with new vibrating screen technology and screen media it’s important for operators to take advantage of new options and choices.

The original scalper screen sizing formula was required because formulas that existed at that time only worked for small openings and finishing screen applications. The large openings used by vibrating scalpers and the uniqueness of the application required something new. Throughout the years, the formula has proven to work well and has been incorporated into modern sizing programs.

For the purpose of this article, the vibrating scalper is described as an extra heavy-duty vibrating screen designed to accept larger feed size (typically larger than 8 inches). The scalper typically screens or scalps at openings from 4 to 8 inches and larger. The scalper is normally designed with extra heavy-duty design features and is equipped with heavy-duty media such as grizzly bars, perforated plate, rubber panels, etc.

The function of the scalping screen is usually described as the separation of oversize material from a feed of finer feed; however, this is not the situation in every application.

Typical scalper applications

• Scalping after a primary crusher. In this application, the scalper will generally remove coarse material from fines. The fines may be sent to a finishing screen for final sizing and the coarse material to a secondary crusher. Here, the scalper typically improves the overall performance of the plant, increases crusher and finishing screen capacity, and reduces crusher wear.
• Production of rip rap products. Extra heavy-duty scalping screens are sometimes used to produce large product sizes called rip rap, which is often used for erosion control and other purposes. The product size may range from 6 to 30 inches.
• Overburden separation. In this application, fines such as dirt and clay may need to be removed in order to clean up coarse-sized rock or other products.

(There are many other scalper applications.)

The following information is required to size a vibrating scalping screen: Feed rates – tons per hour, feed gradation, and deck openings. It’s also important to know and understand other application criteria including specific material specifications, screen media specifications, general application requirements, and scalper service duty.