ess abrasive propelling Wheel that use blades or vanes require about 10% of the horsepower requires by air blast systems to throw equal volumes of abrasive at the same velocities.the power lossed in an airless system are the friction between the airless abrasive blast wheels are generally of the blade type,as shown in Fig.1,these wheels may have one or two side plates,one of which is attached to the shaft bearings,and belt drive,or the side plates,one of which

Is attached directly to the shafe of a suitable motor.the side plate holds four to twelve throwing

Bladed,depending on the size of the wheel.blade tip diameters range from 205 tp 660mm(8 to 26 in.)and blade widths range from 40 to 125mm (1.5 to 5 in.),rotational speeds range from 500 to 4000 rev/min or more.usable abrasive velocities range from 15m/s (50 ft/s) to 122m/s(400 ft/s),with 75m/s (245ft/s) the most widely used velocity.abrasive flow rates with steel shot range from 23kg/min (50lb/min) up to 1040kg/min (2300lb/min) with a 100hp motor.

Figure 1 also shows the operation of a blade-type wheel. a controlled flow of abrasive (through a valve not shown) is fed by gravity into an abrasive feed spout from which it flows into a rotating vaned impeller.the impeller rotates at the same speed as the bladed wheel,and the number of vanes is equal to the number of wheel blades.the impeller roatated in a stationary cylinder (referred to as a control cage pr impeller case).that is equipped with an opening that may be rotated and locked in a preferred postion.as the impeller forces the abrasive out of the control cage opening.each of the blades picks up a metered amount of abrasive at the end of the blade and accelerates the abrasive to produce a tent blast pattern, as shown.

Centrifugal blast wheel units are enclosed in housing to prevent the discharge of stray abrasive,the principal wearing parts of the blast wheel assembly are the impeller,control cage,wheel blades,and housing liners,these parts are most ecomomically made of high-alloy cast iron,and each can be individually replaced.unalloyed cast iron parts, although less expensive,have a very short lift under normal operating conditions.

The life of these parts is influenced primarily by the type and condition of the abrasive medium and contaminants picked up in the cleaning process,abrasive materials are discussed in depth later in this section.clean steel shot provides the longest useful l life of wheel and guard housing liners,much greater wear results from the use of nonmetallic of abrasive in various conditions on the life of the components of a caused by glass beads,nonferrous shot,or the agricultural abrasives frequently used in deburring and special finishing applications.