require less space than fixed-speed or variable-speed couplings. A belt
drive can make speed-to-torque and torque-to-speed conversions. (Torque
is the turning force of rotating equipment.) Process technicians frequently
inspect belts during rounds to ensure that safety guards are in place, that
belt tension is correct, and that the belts are still mounted on the pulleys.
Flopping, squealing, or smoking belts indicate wear, tension, or drivenequipment
problems.
Chain drives are very similar to belt drives. Instead of using pulleys, however,
a chain drive has a series of sprocket wheels that interlink with the
chain. Chain drives are designed for low speeds and high torque conversions.
In this type of system, slippage is minimal, chain replacement is
rare, and temperature variations are not a factor as long as the chain is
kept lubricated.
Gearboxes and Power Transmission
Gearboxes are often used between the driver and the driven equipment.
A gearbox takes its name from the different-sized gears (toothed
wheels) inside the casing. Inside the gearbox, the drive gear meshes
with a larger or smaller gear, the driven gear. As the drive gear rotates,
the interlocked gears in the box turn, transmitting power to the driven
equipment. Smaller gear size is associated with speed. Larger gear size
is associated with torque. Power transmission in rotating equipment is
classified as speed-to-torque conversion or torque-to-speed conversion.
Speed-to-torque conversion is accomplished with a small drive gear that
has a large driven gear. Torque-to-speed conversion uses a large drive
gear that has a small driven gear. Figure 1.4 illustrates the power transmission
principle.