BELT INSTALLATION AND ADJUSTMENT

SECTION VII OPTIONAL EQUIPMENT AND ACCESSORIES

TM-5-3895-374-24-2 M081 Asphalt Mixing Plant Manual
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TM 5-3895-374-24-2 BELT INSTALLATION AND ADJUSTMENT When installing new belts. do not pry the belts over the pulley grooves. The proper method of removing and installing new belts is to loosen the anchor screws and the belt tightener screw, Figure 6-2, and push the motor toward the compressor. Use the tightener screw to adjust belt tension on new belts. Figure 6-2. Belt Adjustments. It is important that the belts be properly adjusted. A belt that is too loose will slip and cause heating and wear, and a belt that is too tight may overload the bearings. A quick check to determine if belt adjustment is proper may be made by observing the slack side of the belt for a slight bow when the unit is in operation. See Figure 6-3. If a slight bow is evident, belts are usually adjusted satisfactorily. However, the recommended method of checking belt tension is by the more accurate spring scale measurement method that follows: Figure 6-3. Visual Method. A. Measure the belt span (t) as shown In Figure 6-4. B. At the center of the span (t), apply a force (perpendicular to the span, by attaching a spring scale to the two outside belts The force applied to the spring scale should be sufficient to deflect the belts 1/64" (.396 mm) for every inch of span length (t). For example: The deflection of 100" (2540 mm) span would be 100/64" or 1 9/16" (39.6 mm), thus the force applied to the spring scale should deflect the belts to 1 9/16" (39.6 mm) Figure 6-4. Spring Scale Method. C. When the belts are deflected the necessary distance. compare the spring scale reading (in lbs. force) with the value given in the following table. STANDARD BELT TENSION Belt Normal 150% Normal Type Tension Tension B 2 3/4 Ibs. (1.25 kg) 4 lbs. (1.81 kg) C 5 1/2 lbs. (2.5 kg) 8 1/4 lbs. (3.74 kg) If the reading is between the value for normal tension and 150% normal tension, the belt tension should be satisfactory. A reading below the value for normal tension indicates the belt slack should be reduced, and conversely, a reading exceeding the value for 150% normal tension indicates the belt slack should be increased. Experienced has shown that a new drive can be tightened initially to two times normal tension to allow for any drop in tension during run in. page 3 - 842

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