Gearbox Selection for Horizontal Units
1. Select Gearbox Type
1.1 Parallel Shafts (helical) or right angle drive
(bevel/helical), foot mount, shaft mount with or without foot.
Calculate gearbox ratio = Input Speed/ Output speed
Select Gearbox Size from Mechanical Capacity
Determine type of load from table uniform,
moderate shock or heavy shock).
Determine mechanical service factor from table 1.
Calculate the required mechanical power capacity (Pm )
(Pm ) = absorbed power (kW) x mechanical service factor
Select gearbox size from rating tables.
Pm must be equal to or less than the mechanical rating of the
Thermal Rating Check
Thermal ratings are given for the following four cases :
Gearbox without additional
Gearbox fitted with fan.
Gearbox fitted with cooling water coil.
Gearbox fitted with fan and coil.
Determine the thermal service factor from table 2.
Calculate the required thermal power capacity (Pt)
(Pt ) = absorbed power (kW) ÷ thermal service factor.
3.4 Specify the type of cooling required by referring to
thermal rating tables.
Pt must be equal to or less than the thermal capacity of the
Gearbox overload capacity at start.
2.5 x mechanical rating, 5 times per day or,
2 x mechanical rating, 5 times per hour.
Higher power than catalogue mechanical
ratings can be transmitted on very intermittent operation within
the finite life of the gears. Consult us with specific application