Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)

First Advisor

Thomas B. Lawson, Jr


This study aimed to: (1) establish a set of optimally configured guidelines for performance testing of crawfish sorting machines; (2) examine biophysical characteristics of crawfish and machine-related design parameters; and, (3) write computer programs covering the essential aspects of the crawfish sorting process. Three crawfish sorting machines were tested in the Spring of 1994 and 1995: (1) cylindrical roller sorter machine, (2) diverging vane belt sorter machine, and (3) grid shaker sorter machine. Both the cylindrical roller sorter and the diverging vane belt sorter separated crawfish into four groups: peeler, medium, large and jumbo; the grid shaker sorter, however, separated crawfish into two groups: large and small. Fortran 77 programs were written to facilitate analysis of data and to model the sorting process. In addition, prediction equations were developed for the following: total body length and carapace width, total body length and carapace depth, total body weight and carapace depth, total body weight and carapace width, angle of repose and total body weight both for PVC and aluminum surface. The following variables were considered: sorter capacity, coefficient of separability, intensity of vibration, hopper opening height, roller speed, clearance between rollers or belts, and included angle between belts. Crawfish samples were randomly drawn from harvest catches during the season and sorting runs performed at different combinations of the variables named. Treating capacity and coefficient of separability as response variables the data indicated that a curvilinear relationship existed among them. The response variables attained maximum values within a definite range of the input variables. These ranges were as follows: (1) roller rpm: 40 to 46 rpm; (2) intensity of vibration: 10 to 20 Hz for both the cylindrical roller sorter and the diverging vane belt sorter and 15 to 20 Hz for the grid shaker sorter; (3) belt included angle: 80.12 to 110$\sp\circ$; (4) hopper opening height: 8 to 11 cm; and, (5) clearance: 11.98 mm (small end) to 26.42 mm (jumbo end) for the cylindrical roller sorter, 15.08 mm (small end) to 28.58 mm (jumbo end) for the diverging vane belt sorter, and 21.4 to 23.4 mm for the grid shaker sorter. Performance ranking of the sorter machines followed the following order, highest to lowest: cylindrical roller sorter, diverging vane belt sorter and grid shaker sorter.