Page 157 - The Tribology Handbook

Belt drives 61

SERVICE FACTORS (SF) FOR VARIOUS APPLICATIONS

Design power = SF x Rated power.

DUTY EXAMPLES
1. Sound and video recorders,
electric typewriters, business
machines and computers
2. Agitators (for liquids), fans up
to 7.5 kW, uniformly loaded
conveyors
3. Agitators (semi-solids), fans
over 7.5 kW, printing machinery,
conveyors (not uniformly loaded)

1 2 I I I 4. Bucket elevators, pulverisers,
textile machinery
0.5
5. Crushers, ball mills, rubber
machinery, e.g. calenders.
Increasing application duty (severity) -

* Some design procedures include arc of contact factors in SF. This is not followed here. SF may be increased by up to O.6for
speed-up drives and if the belt layout requires reverse bending. SF also depends slightly on belt length and other factors: this
detail is not considered here.
It is not customary to include operating timelday in SF for flat belt drives. A mid-range value may be chosen for these.

Figure 1.2 Service factors for various duties

BELT SELECTION FROM DESIGN POWER RATING CHARTS
The belt section is selected on basis of the region which 100,
contains the intersection of design kW with fastest pulley
revimin. Regions can overlap -. more than one belt section
may be a possibility.
Drives may be designed with any pulley diameters >
d,,, for that section. It is usually desirable to choose the
largest diameter pulleys for which space is available,
subject to the maximum recommended belt speed not 10
being exceeded.
The labels dl X wl, d2 X w2 give indications of likely 5
combinations of smallest pulley diameter and belt width
for 180" arc of contact drives.
The design power rating charts on the following pages
are all consistent with the service factors SF above. They 1
differ from some catalogues' charts which use differently
based SF values.
I I
ni . I
.,.
too 1000 10,000
Fastest pulley revlmin
Figure 1.3 The use of power rating charts
81.3