Girth Gears for Drum Drives

A girth gear can be single or double pinion driven. Pinions are manufactured as a single part with an integrated shaft; however, the pinion can be separated and mounted on a separate shaft, supported by bearings, or, on the output shaft of the main gear unit.

The rotation speed of a drum normally varies between 0.5–20 rpm corresponding to the peripheral velocity from 0.3 to 10 m/s of the girth gear. The nominal power of a standard Kumera girth gear is up to 8 MW per mesh, i.e., 16 MW when double pinion driven.

Typical geometry of a girth gear

	Min.	Max.	Standard
Module	20	40	27
Pressure angle, [°]			24
Helix angle, [°]	0	45	0
Number of teeth:
• Girth Gear	100	300
• Pinion	18	30
Face Width, [mm]	100	500
Reference diameter, [mm]	2000	no limitation

Quality	ISO	AGMA
Girth Gear	8-10	9-7
Pinion	7	10

Calculation of tooth load carrying capacity is according to the following standards:

ANSI/AGMA 6004-F88 Gear power rating for cylindrical grinding mills, kilns, coolers and dryers
ISO 6336 Calculation of load capacity of spur and helical gears
DIN 3990 Calculation of load capacity of cylindrical gears