Impact breakers hammer crushers

Impact breakers include heavy-duty hammer crushers and rotor impact breakers. Fine hammer mills are described in a subsequent subsection. 

Hammer Crusher (Fig. 20-27) Pivoted hammers are mounted on a horizontal shaft, and crushing takes place by impact between the hammers and breaker plates. Heavy-duty hammer crushers are frequently used in the quarrying industiy, for processing municipal solid waste, and scrap automobiles. 

In the second type of mill (Fig. 20-28), a cylindrical grating is provided beneath the rotor for product discharge. Some hammer crushers are symmetrically designed so that the direction of rotation can be reversed to distribute wear evenly on the hammer and breaker plates. When such a Pennsylvania nonreversible bammermill is used for reduction, material is broken first by impact against hammers and then by rubbing action (attrition) against screen bars. Performance data of Pennsylvania reversible hammer mills are shown in Table 20-14. 

The hammer crusher shown in Fig. 15 is a special form of construction, equipped with two rollers which rotate in the same direction, but at different speeds, and feed the material to the rotor equipped with freely movable hammers. Undersize particles already present in the feed are discharged through the gap between the rollers. The impact wall and bottom discharge grid, which encloses the rotor through an angle of about 120°, are adjustable in relation to the rotor, so that the wear of tipe hammers, breaker elements and grid bars can be compensated to some extent. 

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