Tecnetics Industries Tecweigh 20, Руководство по эксплуатации, Страница: 64 / 79

- 63 -
9.03 Operation Troubleshooting
If the system is electrically functional, but it does not seem to be calculating the correct RATE or
TOTAL, first verify that all the Parameters are correct. Leaving Weigh Spn = 0 or Belt Len = 0
(Section 6.02.7 & 8), for example, will cause an erroneous calibration and the displayed RATE
will be incorrect. The following are some other problems that might exist and possible solutions:
RATE is unsteady…
If there are large swings in the RATE during relatively constant material flow, several causes are
possible. First, check the belt SPEED and make sure that it is constant, or at least does not
deviate by more than about 1%. If the belt SPEED is not constant, consult Section 9.02 for speed
sensor options. Second, turn off the belt and look at the Load Count Parameter (Section 6.02.57).
Assure that the load counts are higher with the calibration weight down than with the cal weight
up. Additionally, the load counts should not be negative and should remain relatively steady with
the belt not running and no vibration. Replace the load cell(s) (Section 9.05) if the load counts
are inconsistent. If the SPEED and load counts are steady, the RATE should also be steady
unless the AUTO ZERO and AUTO SPAN procedures were not successful. Try doing an AUTO
ZERO and AUTO SPAN again and be sure to do the AUTO ZERO first (Section 7.04). Other
things to consider are the AZT setting and RATE damping. First try disabling the AZT function
(Section 6.02.10), and then try increasing the Rate Damp Parameter (Section 6.02.14).
Ultimately the MS20 should calculate the Rate as follows:
Rate(TPH) = (Cal Factor) x (Scale Load (lbs)) x (Belt Speed (fpm)) / (Weigh Span (in))
Since the Cal Factor and Weigh Span do not change, the only possible problems with RATE will
originate from the scale load and belt SPEED. By using the calibration weight to load the scale
and by simulating the belt speed, the RATE should be steady. If the rate is still unsteady, it is
most likely caused by vibration or excessive electrical “noise” (See Section 9.03, paragraph
“other electrical problems”). Consult the
Tecweigh Service Department (Section 2.01) if
problems persist.
Scale is inaccurate…
It is important to understand that no conveyor scale is 100% accurate. Every detail from
installation through calibration contributes to overall accuracy. A very good installation on a new
conveyor in a noise and vibration free environment can attain an accuracy of +/- 0.5%. A poor
installation on an older and much used portable conveyor might only /- 3% accuracy.
Based on that range of accuracy, estimate a realistic potential accuracy for the weighing system
and then proceed with searching for sources of error. Try to eliminate as many undesirable
conditions as possible. If it can be verified that the RATE is consistently high or low, for finer
tuning adjust the ASC Parameter (Section 6.02.55) up or down accordingly.
The following are a number of potential problems that can contribute to scale inaccuracy:
•
The scale and weigh idler(s) are not aligned properly (Chapter 3).
•
The weigh idler rollers do not spin freely.
•
The speed sensor does not spin freely.
•
The scale is subject to high vibration near a crusher or screen.
•
The scale is incline mounted causing material to roll back and be weighed twice.
•
The load cells or LVDTs are damaged (Section 9.05-06).
•
The conveyor belt has many splices, repairs and irregularities.
•
High temperature fluctuations are causing scale, conveyor, and belt deformation.
•
High winds are causing fluctuations in weighing.