New Holland CornMaster 9208-22, Руководство по обслуживанию

Страница: 39 / 41

INTRODUCTION
Basic instructions - Chain Wear Tables - Roller Chains
Chain wear
The individual joints in a roller chain articulate as they en-
ter and leave the sprockets. This articulation results in
wear on the pins and bushings. Material that is worn away
from these surfaces will cause the chain to gradually elon-
gate. Chains do not stretch. Material is removed from pin
and bushing.
Critical dimensions of the chain are as follows:
•
(1) 2X pitch
•
(2) Wear plus 2X pitch
•
(3) Elongation due to pin and bushing wear
96091478
1
Elongation is normal and may be minimized by proper
lubrication and drive maintenance. The rate of wear is
dependent upon: the relationship between the load and
the amount of bearing area between pin and bushing, the
material and surface condition of the bearing surfaces, the
adequacy of lubrication, and the frequency and degree
of articulation between pins and bushings. The latter is
determined by the quantity of sprockets in the drive, their
speeds, the number of teeth and the length of the chain
in pitches.
An accurate wear measurement (1) can be made by us-
ing the above illustration. Measure as closely as possi-
ble from the center of one pin to the center of another.
The more pitches (pins) contained within the measure-
ment increase the accuracy. If the measured value ex-
ceeds the nominal by more than the allowable percentage
the chain should be replaced. The maximum allowable
wear elongation is approximately
3% for most industrial
applications, based upon sprocket design. The allowable
chain wear in percent can be calculated using the rela-
tionship: 200/
(N) , where (N) is the number of teeth in the
large sprocket. This relationship is often useful since the
normal maximum allowable chain wear elongation of
3%
is valid only up to 67 teeth in the large sprocket. In drives
having fixed center distances, chains running in parallel
or where smoother operation is required, wear should be
limited to approximately
1.5% .
For example, if 12 pitches (12 pins) of a #80 chain were
measured and the result was
313.944 mm ( 12.360 in )
or greater (using 3% as the maximum allowable wear),
the chain should be replaced. Anything less than
313.944 mm ( 12.360 in ) would still be acceptable by
most industrial standards.
96091469
2
51510606 27/07/2018
34