Full Load Efficiency
The graph shows the efficiency of a basic PIV unit,
which may be taken as typical for all sizes. It will
be seen that under full load conditions, this is 86%
at top speed, and 95% at mean speed.
With compound attachments, the efficiency is reduced
by 1.5% for each pair of spur gears and between 20%
and 30% for worm gears in the W portion.
Capacity
The power which can be transmitted at output speeds
between maximum and minimum is shown in the graph by
considering the speed concerned as a percentage of maximum
speed. The power at this speed is then read off the
graph as a percentage of the power at maximum speed.
Selection Data
Data required for selection of PIV unit:
a) Speed Ratio
b) Power or Torque at Max. or Min. speed, or Motor HP
available.
c) Operation conditions, e.g. running time per day,
frequency of starts, uniformity of loads.
Service Factor
The maximum input horsepower of basic PiV units given
in the rating tables are for units operating under uniform
load for 12 hours per day. Where operating conditions
differ, multiply the required power by the factors shown:
Rating
time per day 
Uniform
load 
Moderate
shockload 
Heavy
shockload 
06 hrs.
12 hrs.
24 hr. 
0.8
1.0
1.25 
1.0
1.25
1.50 
1.25
1.50
1.75 

