shaft is failing at critical speed, select next standard shaft of diameter 120mm and perform the calculations for critical speed. Maximum deflection (∆) due to bending force and corresponding critical speed (Nc) is calculated as follows,Īgitator should be designed to operate at less than 70% of the critical speed. Step:5 Design of solid shaft based on critical speed Therefore, selecting shaft diameter of 100mm, the shaft is checked for critical speed. Larger of all calculated diameters is considered as the minimum required diameter of the shaft. Step:4 Design of solid shaft subjected to bending and twistingĪccording to maximum shear stress theory for ductile material, equivalent twisting moment is calculated asĪccording to maximum normal stress theory for brittle material, equivalent bending moment is calculated as 0.75 of maximum agitator radius from the axis. Maximum bending force is assumed to be acting at the point of jamming i.e. Step:3 Design of solid shaft subjected to pure bending Therefore, solid shaft diameter is calculated by Step 2: Design of shaft Design of solid shaft subjected to shear stressįor selected motor power rated torque and maximum torque is calculated as given below:

1 – Power number against Reynolds number of some turbine impellers īased on impellers selected the layout of the shaft is done as shown in Fig.2. For given type of agitation flat paddle impeller is used as given below:Īfter selection of impeller dimensionless number Reynold’s number is calculated as given belowįrom generic agitator curve, as shown in Fig.1, impeller power number is calculated based on calculated Reynold’s number.įig. Flat paddle, turbine, anchor type, pitched blade impellers are used most commonly. Selection of impeller is done based on application and type of flow. Solution: Step-1: Power calculations and selection of motorįor required power calculations, selection of the type of impeller is very important to achieve required agitation power. Here we will discuss the design of agitator vessel based on practical data inputs as given below: Type of fluid and its physical state, the degree of agitation and geometry of vessel are key factors in the design and selection of agitator components. Mixing is accomplished by the rotating action of an impeller in the continuous fluid.

It may include mixing of liquid with liquid, gas with a liquid, or solids with liquid.

In industries mixing of fluids is necessary for many chemical processes. Agitators are machines used in industries for mixing fluids.

Eeua handbook for agitator design pdf