An open-circuit crusher is easier to design and lay out than a closed-circuit design, since it has fewer equipment items and structures. Figures 13, 14, and 15 show some typical secondary crusher open circuit layouts. Figure 16 shows some typical open circuit secondary and tertiary crushers. Provisions should be made for possible future conversion of an open-circuit plant to a closed-circuit version. Cone crushers remain the choice for most secondary and tertiary operations, with some gyradisc and vertical-impact crushers also utilized on certain ore types. Water-flush cone crushers have been introduced in secondary and tertiary installation, which requires careful design of the water systems to and from the crusher. Most open-circuit secondary and tertiary crushers include scalping screens to remove fine material prior to the secondary crushers. Closed-circuit crushers use tertiary screens to control the final product size. (See Figure 17 and 18 for typical closed circuit secondary and tertiary crushers.) In some larger installations, the secondary and tertiary crushers are located in one plant area and the screens in another. (See Figure 18f.) Crushers and screens in these plants have common bins feeding to the multiple crushers or screens. Most plants now have the screen feeding the fine crusher, providing for easier access to service the screens. As with primary crushers, fine crushers must meet the design parameters listed above. Design details that are helpful to fine crusher plant layout area listed in the sections that follow. Used Hammer Mill The SEPOR Mini-jaw crusher is suitable for crushing small quantities of rock and other friable material, ranging in hardness from hard quartz to relatively soft claystone. It is available with a variety of wear surfaces: Hardened steel alloy plates for users not concerned with iron contamination and 85% Alumina (Ceramic) for those who can not tolerate iron contamination. A tungsten carbide model is also available, which is the hardest material of the three. The tungsten carbide contains 6% cobalt as a binder. The feed opening is 2' x 2' with a maximum feed partical size of -1' material. About 1/3 lb. per minute (20 pounds per hour) can be crushed to -1/8' depending on the nature of the feed material. The size of the crushed product is adjustable by turning the handwheel, which adjusts the gap at the bottom of the jaws. The jaw opening range is from 1/4' to 1/16'. However, the finer the crushed product, the lower the throughput. A stainless steel tray collects the crushed sample. If cross sample contamination is of paramount importance, each sample may be caught on separate trays. Metso Verti Mill