GN designed GNLW363 decanter centrifuge with a two-stage planetary reducing gear box, also called differential. 
There is internal gear on the shell. Shell rotate with the drum, and then left pulley drive 1-stage sun gear on the input shaft to rotate, at this time, 1-stage sun gear gear into inner gear through 1-stage planet gear, thus 1-stage revolving arm rotational speed is formed by rotational speed of shell and input axle, and this rotational speed was outputted to 2-stage through 2-stage sun gear. The transmission principle of the two stages are the same, at last, propeller begin to rotate driven by output shaft. Differential is the most complex and most important part of decanter centrifuge.