1. Reasons for drift
Periodic calibration: Since the zero point interval of the belt weigher is affected by various factors, the zero point and interval of the belt weigher will drift to varying degrees, so it should be calibrated regularly. The calibration cycle should be determined according to different on-site requirements.
Causes of zero drift:
① Stones or foreign matters are stuck in the weighing bridge;
② Ash and material accumulation on weighing bridge:
③ Due to the temperature characteristics of materials, the length of the conveyor ring belt changes;
④ Sticking of conveyor belt;
⑤ The load cell is seriously overloaded;
⑥ Serious deformation of scale frame;
⑦ Electronic measuring unit or instrument failure;
⑧ Belt deviation.
Reasons for interval drift:
① The sliding of the speed measuring cylinder or the change of its diameter;
② Change of conveyor belt tension;
③ The load cell is seriously overloaded;
④ Change of belt speed;
⑤ Serious deformation of scale frame;
⑥ Electronic measuring unit or instrument failure.
2. Verification
The calibration methods of high-precision electronic belt weigher include hanging code calibration, chain code calibration and physical calibration. The electronic belt weigher of our coal handling system mainly adopts hanging code calibration. The so-called hanging weight verification is mainly to hang the weight with standard weight on the idler of the belt scale, or to simulate the weight data when the material is running on the weighing bridge.
The whole process of code hanging verification shall include zero point verification and interval verification.
① Zero calibration starts after the belt runs for 30 minutes without load. If the zero calibration error is within ± 0.05%, it is not necessary to change the zero point. At this time, continue to carry out zero calibration for a total of 3 times. If the error exceeds ± 0.05%, the zero point must be changed. Re calibrate the zero point. In a word, ensure that the number of consecutive calibrations within the error range is not less than 3.
② After the zero calibration of interval calibration is qualified, the interval calibration shall be carried out. When the belt weigher operates normally and the belt is clean without coal, slowly put the standard hanging weight down on the weighing bridge and start interval calibration. If the interval calibration error is within ± 0.5%, it is not necessary to change the interval. Proceed with interval calibration for a total of 2 times. If the error exceeds ± 0.5%, the interval must be changed. Perform interval calibration again. In a word, ensure that the number of consecutive verifications within the error range is not less than 2.
