TM 5-3895-382-24Problem: Noisy vibratory mechanism.Probable Cause:1.Low oil level in the drum.2.Failure of the vibratory drive shaft or componentsleading up to the vibratory drive shaft.3.Loose retaining bolts for the vibratory motor.Problem: Hydraulic circuit oil overheats.Probable Cause:1.Incorrect type of oil used in the hydraulic system.2.Hydraulic oil cooler is restricted.3.Excessive internal leakage in the closed loop circuit.4.Low charge pressure.5.Cooling relief valve pressure setting higher than pumpcharge relief valve pressure setting.6.Failure of vibratory shaft bearings which causesextended periods of time over the vibratory pump highpressure reliefs.Problem: Maximum VPM is too high.Probable Cause:1.Faulty VPM gauge.2.Engine RPM is too high.3.Incorrect internal displacement stops were supplied.System Tests and AdjustmentsPump Efficiency CheckFor any pump test at a given rpm, the pump flow at 690 kPa(100 psi) will be larger than the pump flow at 6900 kPa (1000psi). The difference between the pump flow of the twooperating pressures is the flow loss.Method of finding flow loss:Pump flow at 100 psi ................................... 57.5 gpm (liter/min) *Pump flow at 1000 psi ................................-52.0gpm(liter/min)*Flow loss .......................................................... 5.5 gpm (liter/min) *Flow loss when expressed as a percent of pump flow is usedas a measure of pump performance.Example of finding percent of flow loss:gpm flow lossPump flow @ 100 psiX 100 =Percent offlow loss*5.5or*57.5X 100 = 9.5%If the percent of flow loss is more than 10%, pumpperformance is not good enough.* The numbers in the examples are for illustration and are notvalues for any specific pump or pump condition. SeeSpecifications for pump flow of a new pump at 690 kPa (100psi) and 6900 kPa (1000 psi).Machine TestInstall a Flow Meter. For Formula I, measure pump flow at 690kPa (100 psi) and at 6900 kPa (1000 psi) with the engine athigh idle rpm.Formula Igpm @ 100 psi - gpm @ 1000 psigpm @ 100 psiX 100 =Percent offlow lossBench TestIf the bench test can be run at 6900 kPa (1000 psi) and at fullpump rpm, find the percent of flow loss using Formula I.If the bench test cannot be run at 6900 kPa (1000 psi) and atfull pump rpm, run the pump shaft at 1000 rpm. Measure thepump flow at 690 kPa (100 psi) and at 6900 kPa (1000 psi).Use these values in the top part of Formula II. For the bottompart of the formula, run the pump shaft at 2000 rpm. Measurethe pump flow at 690 kPa (100 psi).Formula IIgpm @ 100 psi - gpm @ 1000 psigpm @ 100 psi @ 2000 rpmX 100 =Percent offlow loss13-32

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