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APPENDIX F
WEIGHED LOAD TEST SUGGESTIONS - TM-5-3895-374-10_314

TM-5-3895-374-10 Paving Machine Bituminous Material: Crawler Mounted Diesel Engine Driven Manual
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TM 5-3895-374-10 ..................................................................................................................................WEIGHED LOAD TEST SUGGESTIONS The following suggestions are for belt scale calibrations although many of the ideas apply equally well to asphalt meter or other calibration procedures. Accurate  and  repeatable  calibration  runs  are  possible.    They  do  require  an  understanding  of  and  appreciation  for  the details of the test.  Basically the procedure is as follows: 1) Run the equipment until it will respond stabily and uniformly. 2) Obtain a stable zero on the totalizer. 3) Run aggregate across the belt scale and directly into a truck. 4) Weigh the truck and calculate the net weight. 5)  Compare  the  actual  truck  net  weight  and  the  indicated  scale  total  weight.    If  the  indicated  weight  is  not  in tolerance, readjust the scale span calibration value and repeat this test starting at Step 2. Sometimes it does not seem this simple.  Pitfalls to watch for include: In Step 1 -Often equipment does not stabilize until after it has been used for a while.  This may especially be true of new equipment, rusty equipment or moist materials.  Sometimes it is necessary to "waste" or disregard several truck loads of material in order to get the most stable results.   Use  material that is uniform.  For aggregates this means material, preferably dry, of uniform moisture content and gradation.  For dusts or fillers the material should be of uniform density, free flowing and free of  clumps.    For  liquids  this  means  uniform  temperature  and  density.    Liquids  often  must  be "stirred" until uniformity is assured. In Step 2 -Do not rush at this point.  If calibrating at 100 TPH a 1 TPH zero error is 1I.This 1%  is  often  a greater error than the maximum allowed.  When repeating a test, material buildup on the belt will often change the zero.  The answer may not be as simple as waiting for the belt to clear.  After all, material will again build up on the belt during the test and create an error.  The system can appear to calibrate and may even repeat, but only because the "calibration" value includes an equal and offsetting error.  The best solution is to select material that does not stick to the belt.  In the worst case, course material may need to predried and stockpiled for this calibration. page F - 111 SYSTEMS Equipment Corp.  8/31/89  Page (62)          APPENDIX G







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