As we all know that road, bridge and real estate construction are in desperate need of sand, stone and cement which are produced by crusher machines. The jaw crusher and impact crusher are usually used as primary crusher more. The term "primary crusher," by definition, might including any type and size of crushing machine. The term implies that at least two stages of crushing are involved, but in many cases the machine which performs the function of initial crusher is the only crusher in the plant.The factors influencing the selection of a crusher for this service are much the same, regardless of how many crushing stages there are in the flow sheet; therefore, the term "primary crusher," by common usage, is applied to the crusher which takes up the job of reduction where the blasting operations leave off.Selecting the right type and size of primary crusher is a problem of prime importance in the designing of a crushing plant of any nature and size. Usually this machine is the largest and most expensive single item of equipment in the plant; a mistake in the choice can only be remedied fully by replacement; and, because the entire primary crusher house arrangement is generally "tailored" to fit the crusher, such replacement is almost always a costly procedure.While personal favoritism toward some particular type of crusher may safely be allowed to swing a close decision, it should never blind the engineer or operator to the merits of other types, nor to the limitations of his favorite. The following factors all have a more or less important bearing upon the choice of the primary crusher.1. The name, hardness, humidity of material;2. The size or discharging size of final production;3. The hourly, daily or yearly capacity are required;4. Method of feeding the crusher;5. Type and size of quarry equipment.shaking table: http://www.fte-china.com/pro/shaking_table.html