Bevel-helical gear boxes B2 y HCH HCM h F h F h F h B2-FV-10-D

Flender/Flender Gear Units/Bevel-helical gear boxes B2

nt) should be quickly offset by the controller in order to provide acceptable upsetrecovery time and system stability. Control Aspects 8 4.Robustness : The control system should be able to operate successfully over wide range of process conditions. In relation to process control, the variables (temperatures, moisture contents, ow rates, pressures, etc.) associated with an agricultural drying process can be generally di- vided into two groups (1,: 1.Input variables , which denote the effect of the surroundings on the drying process 2.Output or controlled variables , which denote the effect of the drying process on the surroundings The input variables can be classied as manipulated variables , which can be adjusted either manually or automatically, and disturbances or load variables , which cannot be adjusted by control system. The most important manipulated inputs to dryer are () heating rate (.., inlet air temperature for direct dryers), () airow rate (for direct dryers), and () solids feed rate. The most common dryer disturbances are 1. Ambient air humidity 2. Ambient air temperature 3. Feed moisture content 4. Feed temperature5. Feed composition The dryer output or controlled variables may be classied as measured output vari- ables andunmeasured or difcult-to-measure output variables . For instance, the product moisture content can be measured or unmeasured variable, depending on the capabilityof the moisture sensor applied. The most typical dryer output variables are 1. Exhaust air humidity 2. Exhaust air temperature3. Dried product moisture content4. Dried product temperature5. Product quality (color, avor, activity, etc.) The relationships among output, manipulated, and load variables, which also apply to the control system of the drying process, can be seen in Fig. 1. Fig. 1 Scheme of drying process variables. 8 Farkas The purpose of dryer control system is to produce desired output by adjusting the manipulated variables to compensate for changes cause