Common Fault Aanalysis of Electrical Control System in Concrete Mixing Plant

HZS series concrete mixing station adopts the form of computer, PLC and batching control instrument in the electrical control. The electrical control system is the command center of measurement, operation and management of concrete mixing station. According to the control mode, the structure is mainly composed of programmable controller, electronic scale measurement system, relay contactor control part and computer system. In the process of using concrete mixing station, in order to give full play to the performance of the electrical control system of concrete mixing plant, reduce the failure and improve the working efficiency, the paper discusses eight common faults of the electrical system.

1. The actual material value is not consistent with the set value

1) The target ingredient component of fault phenomenon is consistent with the displayed ingredient component, but the actual material is far greater than or less than the setting

2) Cause of failure

① The weighing system is affected by external force; ② The drift error of sensor causes the zero position or the weighing distance of the scale to change (i.e. inaccurate weighing); ③ If the sensor is damaged, the scale of multiple sensors should consider the situation of bias load. If the load is biased, it may be damaged, the cable is loose or damaged.

3) The method of elimination ① elimination of external force; ② Re scale; ③ Replace the sensor and check the cable.

2. Instrument display is not correct

1) The fault phenomenon instrument shows that the ingredient component is not in accordance with the set target quantity, which has exceeded the batching accuracy.

2) The reason for the fault ① the setting of fast and slow batching components is not suitable; ② The target value is low, and the impulse value is close to the coarse measurement value on the instrument, and the coarse measurement value is equal to 1 / 2 of the target quantity; ③ The fluctuation of feed flow leads to the change of overshoot; ④ The uniformity and humidity of materials change greatly; ⑤ The tolerance range setting value is too large; ⑥ The delay time setting of the over tolerance check is too small; ⑦ The automatic compensation of instrument parameters and the setting of over tolerance are not suitable; ⑧ Digital filtering and prohibition of comparison time setting are too large.

3) The exclusion method ① the initial set overshoot should be as close as possible to the actual value; ② Appropriate mixing capacity is adopted; ③ Reduce the flow of ingredients; ④ Ensure the material is uniform and the humidity changes little; ⑤ The tolerance range of correction is less than the accuracy of batching; ⑥ The delay time shall not be less than 2.5s; ⑦ Check that the deviation is not set to zero, and the automatic compensation is set to "1"; ⑧ Set the appropriate digital filter and prohibit the comparison of time parameter values.

3. No material ingredients

3.1 fault phenomenon

Phenomenon 1: when the material is not batched under the automatic working state, the indicator light of the ingredient is on, but the motor or solenoid valve does not act.

Phenomenon 2: under the automatic working state, no ingredients are added, the indicator light of ingredients is not on, and the instrument displays "set" does not move.

3.2 causes of failure

3.2.1 fault phenomenon I

1) The corresponding indicator light of ingredients on the instrument and operation panel is on, indicating that cb9200x and PLC are normal, and the failure may be caused by insufficient air pressure (aggregate scale).

2) If AC contactor of corresponding circuit is closed or solenoid valve has AC220V power supply, it may exist: ① corresponding ingredient actuator (motor or solenoid valve) is damaged; ② The wiring between AC contactor and motor may be loose and connected in virtual way.

3) If AC contactor does not engage or solenoid valve is not available

AC220V power supply, may exist: ① the relay in the middle of the corresponding circuit is damaged; ② Damage of AC contactor; ③ The corresponding wiring is not normal.

3.2.2 fault phenomenon 2

1) Cb920 meter is damaged or AC 220V power supply is abnormal.

2) The setting of ingredient component does not meet the setting conditions.

3) Target quantity > coarse measurement > overshoot.

3.3 exclusion method

For the first problem, the troubleshooting method is as follows: ① check whether it is empty

Press, air connection, etc; ② Check the motor and solenoid valve with Multimeter; ③ Check the line; ④ Replace the intermediate relay; ⑤ Replace AC contactor; ⑥ Check the wiring.

For the second problem, the troubleshooting methods are as follows: ① check the power supply or replace the instrument; ② Set the ingredients of the corresponding instruments and power on the instrument again.

4. Ingredients are kept on

1) If the computer instruction has stopped, continue the batching production.

2) The reason for the fault ① the instrument parameters are disordered; ② There are foreign objects in the sensor, the sensor is changed in the state of force, and the instrument does not get the correct feeding information; ③ The batching port is stuck (aggregate scale).

3) The exclusion method ① terminate the ingredients according to mode, tower and zero at the same time on the corresponding batching instrument panel, and check the correction parameters; ② Check the sensor to make the scale in a free state; ③ The aggregate bin is added with a barrier to separate the super diameter aggregate.

5. No discharging of the aggregate bin

5.1 fault phenomenon

Under the automatic working state, the bin will not unload.

5.2 causes of failure

1) Observe that the discharge indicator light of the aggregate bin on the operation panel is not on, the indicator light of discharging of aggregate scale is off, which may exist: ① the discharge door of mixer has been fully closed, the relay in the limit control circuit fails, and the closing signal is not fed back to PLC; ② The full closing limit switch of the discharging door of mixer is damaged or displaced; ③ No starting of ingredients for a material;

2) Observe that the discharge indicator light of the collecting bin on the operation panel is on, which may exist: ① insufficient air pressure and serious leakage in the discharge cylinder; ② If the solenoid valve is not supplied with AC 220V, there are burning of coil of intermediate relay, damaged contact and poor wiring of power supply line of solenoid valve; ③ If the solenoid valve is supplied with AC 220V, there are coil burning, valve core clamping and valve body seal damage.

5.3 exclusion method

1) Check the limit control feedback circuit.

2) Check the switch for replacement or adjustment and fixing.

3) Start the "batching tool" for replenishment, and complete the current batch production in semi-automatic mode.

4) Check the air circuit and replace the wear parts.

5) Check the wiring and replace the relay.

6) Replace the solenoid.

6 the instrument is not online with the computer

1) The failure phenomenon turns on the computer, cb9200x instrument is not online with the computer, and the prompt box appears on the display.

2) The reason for the fault ① the power supply key switch on the operating platform is not opened; ② Communication card is damaged and there is no display on the computer; ③ Communication card is not equipped with driver; ④ The instrument itself is damaged; ⑤ There is a problem in the communication between the instrument and the computer.

3) The elimination method ① turn on the key switch; ② Replace communication card; ③ The driver in device manager has backup on the "F" disk, which can start "moxa setup" for port design or install the driver by adding hardware; ④ Replace the instrument; ⑤ Check whether the communication line is loose, broken, short connected or touched with shell, etc. 7 data not recorded

1) In the process of concrete mixing plant production, the computer can not record data in time, which leads to information loss.

2) The reason for the fault is: the online mode is converted to manual mode; ② Computer virus; ③ Incomplete data filling; ④ Interference; ⑤ Mandatory exit procedure; ⑥ The operating system version is incorrect. If you execute [create desktop icon] in F disk, the shortcut of desktop program will be pointed to f disk. Since the data files are stored in disk D, no data is found in the [data report] when executing the program.

3) The correct operation is to change the control mode from [Online] to [manual], and the correct operation is from [full automatic] to [semi-automatic]; ② Effective antivirus software for killing; ③ The data in the production order shall be filled in completely; ④ Check the instrument and signal line to eliminate interference; ⑤ No exit from the procedure is allowed in production; ⑥ The operating system requires the use of windosxp professional edition.

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