Common Faults & Solutions Of Concrete Mixing Plant Control System

The main motor of the mixer does not start

Fault phenomenon: press the concrete mixer start button on the operating table, the mixer does not start. 

Cause analysis:

1、The air compressor is not started or the pressure of the air supply system is not reached 

2、The mixer host maintenance protection switch and the host with key tight stop switch is not connected. 

3、The tight stop switch on the operating table is not reset. 

4、The power switch of the main machine is not turned on. 

5、The stop signal of the main machine must be reset. 

Processing process: 

1、Check whether the compressed air detection signal (air pressure signal greater than 0.4MPa) is sent to the PLC, that is, whether I8.0 has a signal. If I8.0 has no signal, check whether the pressure of the air compressor is greater than 0.4MPa. When the pressure reaches above 0.4MPa, I8.0 still has no signal, check whether the electric contact pressure gauge adjustment is normal or damaged until I8.0 has signal.

2、Check whether the signal is sent to the PLC for the maintenance and protection switch of the main mixing machine.

3、Check whether the tight stop switch on the operation table is reset. 

4、Check whether the power switch of the main machine is on. 

5、Check whether the host stop button is reset. 

In the automatic production process, the aggregate of the batching plant is not discharged after weighing.

Fault phenomenon: In the process of automatic production, one or more kinds of aggregates are weighed in the measuring hopper, but not unloaded, and the system stops running. 

Cause analysis:

1、The hopper to be closed is not in place. 

2、Weighing instrument does not have unloading output signal. 

3、The belt machine is not started. 

4、The fine weighing door of the aggregate weighing meter is not closed in place. 

5、Aggregate must define the unloading sequence. 

Processing process:

1、Check whether the valve of the hopper to be material is stuck or the door is not closed in place, after the door is closed in place, I6.7 has a signal.

2、Check whether the aggregate weighing meter unloads output signal, stone 1 unloads I0.4, stone 2 unloads I0.7, sand 1 unloads I1.5, sand 2 unloads I1.2. 

3、Check whether the belt machine starts. 

4、Check whether the fine weighing door of aggregate is closed in place, stone 1 fine weighing closed I8.2, stone 2 fine weighing closed I8.3, sand 1 fine weighing closed I8.5, sand 2 fine weighing closed I8.4. 

5、Check the computer interface, whether the aggregate unloading sequence is defined. 

Inclined belt start not moving

Fault phenomenon: After the mixer starts normally, press the inclined belt start button on the operation table, the inclined belt does not start. 

Cause analysis:

1、Mixer is not started. 

2、The inclined belt maintenance stop switch is not reset. 

3、The inclined belt machine power switch is not connected. 

4、The inclined belt machine stop button switch is not reset.

Digital drift when the meter is static

Fault phenomenon: In the natural state, the meter display data continuously changes. 

Reason analysis: The weighing instrument shows weight data from the current signal transmitted by the sensor junction box, the instrument shows large weight fluctuations, it means that the current fluctuations transmitted by the sensor junction box. Sensor internal bridge damage or sensor junction box junction loose will cause current fluctuations.

Process: Remove all wiring of a sensor in the junction box and see if the meter data continues to drift. If the meter data stops drifting, it can be judged that the sensor wiring is loose or the sensor is damaged. Remove all the sensor wiring re-connected to the junction box, such as the meter data to stop drifting, the cause is due to loose wiring, such as the meter data continue to drift, the sensor is damaged, replace the sensor can be solved. If you remove a sensor, the meter data continue to drift, then remove another sensor (have removed the sensor wiring first do not connect), according to similar methods.

The mixer does not unload after the mixing time is up

Fault phenomenon: in the automatic production process, after the mixing time becomes zero, the mixer does not unload. 

Analysis: Under normal circumstances, after the mixing time becomes zero, the mixer back to automatic unloading, but in the production process pressed the pause button on the operating table or click the mouse on the computer monitoring interface to prohibit the material control, the mixing time to the mixer will not unload. Another discharge door solenoid valve is damaged, the discharge door can not be opened, the mixer will not be unloaded. 

Processing process:

1、Check whether the pause button is pressed on the operating table, if pressed, reset.

2、Check whether the computer monitoring interface on the prohibition of discharging control is activated, such as the activation is canceled.

3、Check whether the discharge solenoid valve is working normally.

Mixer tripping

Fault phenomenon: In the process of feeding and mixing, the mixing machine is bored and tripped due to excessive current.

Cause analysis:

1、Too much material, causing the mixer load is too large. 

2、The gap between the mixing system blade and liner is too large, the mixing process, increasing the resistance. 

3、Triangle drive belt is too loose, so that the transmission system efficiency is low. 

4、The safety maintenance switch on the upper cover of the mixing host is vibrated loose, causing stoppage. 

Processing process:

1、Check whether the batching system is over the standard and whether there is secondary feeding phenomenon. 

2、Check whether the gap between the mixer blade and the liner is 3~8mm. 

3、Check the tightness of the v-belt of the transmission system and adjust it. 

4、Check whether the safety switch on the cover of the host is loose.

Mixer unloading door closing no signal

Fault phenomenon: after the mixer unloading material, unloading the material door closed, but no door signal, causing the program to stop running. 

Analysis of the causes: mixer unloading door proximity switch and unloading door on the turn handle pointer proximity distance of not more than 5mm to sense the signal. When the unloading door because the oil pump pressure does not meet the requirements or unloading door in the closure of the mixer is stuck in the residual material, the proximity switch is not close to the handle pointer and no signal, because the proximity switch or handle pointer is loose, so that the proximity distance of more than 5mm, the proximity switch also does not sense the signal. If the proximity switch is damaged, there is also no signal output.

Processing process:

1、Check whether the working pressure of the hydraulic system of the discharge door meets the requirements 

2、Switch to manual, the mixer unloading door open, so that the residual material stuck after falling off and then close. 

3、Check whether the proximity switch and the turn handle pointer is loose. 

4、Check whether the proximity switch is damaged. 

Uneven concrete mixing

Fault phenomenon: the concrete unloaded from the mixer is not uniform, dry on one side and wet on the other.

Analysis of the reasons: mixing time is too short will not mix evenly, another mixer nozzle is not installed correctly, the spray water is not uniform, more likely to make the concrete dry on one side, wet on the other. 

Treatment process:

1、 Check whether the mixing time is too short (generally 30 seconds), such as mixing time is too short to extend the mixing time.

2、 Check whether the installation of the nozzles of the spray pipe is arranged in the correct order, the correct order of arrangement is the smallest nozzle on the side of the drainage pump, the largest nozzle on the other side, the middle of the installation in an even arrangement in the order from small to large.

Inaccurate weighing of aggregates

Fault phenomenon:

1、Aggregate weighing is always too much. 

2、Aggregate weighing is always on the low side. 

3、Aggregate weighing will be more and then less. 

Reason analysis: Aggregate weighing error is closely related to fine setting, drop and uniformity of unloading. The fine setting data must be larger than the falling difference, otherwise, the fine setting signal is not yet output, and the falling difference signal has been issued to stop unloading.

Processing process:

1、Aggregate is always too much, can be solved by adjusting the fall difference. After adjusting the difference, need to check whether the value is less than the fine setting value, such as the difference is greater than the fine setting, then the value of the fine setting should be adjusted accordingly. 

2、 Aggregate is always less, can be solved by adjusting the small drop. After the drop is adjusted smaller, the fine setting value generally does not need to be adjusted.

3、 Aggregate weighing a little more and a little less, first check the uniformity of the discharge, check whether there is debris stuck in the discharge port, and then adjust the fine setting and drop. 

Inaccurate weighing of powder

Fault phenomenon: 

1、 The powder weighing is always too much. 

2、 The powder weighing is always on the low side; 

3、 The powder weighing will be more and then less.

Reason analysis: The factors related to the powder weighing include the setting of the drop, the uniformity of the feeding of the screw machine, the influence of the negative pressure of the dust removal in the main building, etc.

Treatment process: Always more or always less can be corrected by adjusting the drop difference. When the weighing is unstable, check the uniformity of screw machine feeding (mainly see whether the powder tank is smooth) and deal with it. Also check whether the main building dust removal pipeline and dust removal machine cartridge are blocked.

Inaccurate weighing of external additive

Fault phenomenon:

1、Additives weighing is always too much. 

2、Admixture weighing is always on the low side. 

3、Admixture weighing a little more and a little less. 

Cause analysis: mainly the impact of drop and manual ball valve opening degree. 

Process: first adjust the drop, such as adjusting the drop after weighing still have problems, then the manual ball valve in the admixture pipeline to close the small, and then adjust the drop. 

Powder scale measurement accurate after weighing meter reading gradually become smaller

Fault phenomenon: in the automatic production process, the material in the powder measuring hopper weighing good gradually become smaller. 

Cause analysis: mainly caused by the unloading pneumatic butterfly valve is not closed. And the pneumatic butterfly valve off the factors are not strict: pneumatic butterfly valve assembly time limit screw position is not suitable to cause the butterfly valve itself off not in place, another butterfly valve outlet sticky material, will also cause the pneumatic butterfly valve off not in place.

Processing process:

1、First disassemble the red hose connected with the pneumatic butterfly valve, check whether there is material sticking to the butterfly valve, if there is, then in the butterfly valve open state, use the steel brush to clean off the material. 

2、Check whether the position of the limiting top wire of the butterfly valve is suitable, and limit the opening degree of the butterfly valve by adjusting the top wire.