Concrete Mixing Plant Mechanical Parts Common Failures & Solutions

Slow feeding of powder

Fault phenomenon: The screw machine feeds material very slowly, and the feeding time is more than 2 minutes, while the normal feeding is below 20 seconds. 

Cause analysis: The influencing factors are mainly poor feeding of powder tank and damage of screw conveyor, etc. The manifestations of poor powder feeding include powder arching, material lumping at the outlet of powder tank, small opening of discharge butterfly valve, insufficient material in powder tank, etc. And the screw conveyor damage is mainly deformation of the screw blade, can not be normal conveying.

Processing process:

1、 Open the air blowing arch breaking device. 

2、 Check the opening degree of the powder tank discharge disc valve, and make the disc valve in the fully open position. 

3、 Check whether the material at the outlet of powder tank is caking. 

4、 Check whether the spiral machine blade is deformed, if deformed, remove and correct or replace. 

Belt runaway

Fault phenomenon: belt conveyor in the no-load or load running process, appear to one side of the runaway or a while and the left side of the runaway and the right side of the phenomenon, causing material leakage, abnormal wear and damage to equipment, reduce productivity, and will affect the normal work of the whole set of equipment

Cause analysis: the external force on the tape is not zero in the direction of the width of the tape or the uneven tensile stress perpendicular to the width of the tape. As a result of many factors leading to tape runout, so should be from the conveyor design, manufacturing, installation and commissioning, use and maintenance to solve the tape runout, such as the elasticity of both sides of the tape is not the same, the height of both sides of the tape is not the same, roller support and other devices are not installed with the tape running direction of the vertical cross-section will cause the belt runout.

Processing process: 

1、 Adjust the tensioning mechanism method

When the tape is running, if it runs off to the same side under no load and heavy load, it means that the elasticity of both sides of the tape is not the same; if the tape runs off left and right and no fixed direction, it means that the tape is loose and the tensioning mechanism should be adjusted.

2、 Adjust the roller method 

If the tape runs off at the drum, it means that the installation of the drum is not level, and the drum axis is tilted, or one end of the drum is in the front and one end is in the back. At this time, the level and parallelism of the roller should be corrected. 

3、 Adjust the roller support (or rack) method 

If the tape in the no-load total to one side of the runaway, the runaway side of the roller bracket should be moved forward along the tape running direction 1-50px, or the other side of the roller bracket (or rack) appropriately higher. 

4、 Clear the sticky material method 

If the material is stuck on the roller and the local part of the roller, the diameter of the place will increase, resulting in the increase of the tape tension at the place, thus producing runout. The sticky material should be cleared in time. 

5、 Adjust the gravity method 

If the tape does not run off at no load, but always run off to one side when heavy load, it means that the tape has bias load. Should adjust the position of the receiving bucket or tape machine, so that the tape is evenly loaded, in order to prevent deviation. 

6、 Adjust the tape method

If the tape edge wear is serious or the tape seam is not parallel, will make the tape on both sides of the tension is not consistent. The tape should be trimmed again or replaced.

7、 Installation of deflection roller method

If the conveyor is installed on several sets of automatic centering rollers (flat rollers or slot rollers), that can automatically correct the tape deviation phenomenon. For example: when the tape deviation and a side of the small stop roller friction, should make the side of the bracket along the running direction of the tape to move forward, the other side that is relatively backward, the tape will then move towards the backward side of the stop roller, until back to the normal position.

8、 Installation of limit roller method

If the tape always run off to one side, can be installed in the run-off side of the rack limit roller; so that, on the one hand, the tape can be forced to force reset, on the other hand, the roller can reduce the run-off side of the tape tension, so that the tape to move to the other side.

Aggregate feeding door jam material

Fault phenomenon: the pneumatic door of the batching station stone feed is stuck by the stone and cannot be opened.

Cause analysis: The pneumatic door of batching station has big gap door and small gap door, the gap of big gap door is bigger than the general stone particle size, so there is no material jam. The gap of the small gap door is usually 5~10mm, when the stone below 10mm is stuck into the gap, it is difficult to jam the pneumatic door. After using the dosing station for a period of time, the aggregate outlet wears out, when the gap wears to 20~30mm, when the larger stones stuck into the gap at this time, in the process of opening the door, the stones are easily stuck (covenant force), so that the pneumatic door cannot be opened.

Processing process: check the pneumatic door gap and adjust to the appropriate value, if it cannot be adjusted to the appropriate value due to excessive wear, it is necessary to add welding steel plate or round steel at the material mouth to make the gap reach a reasonable value.

Powder coming out from the top of the cement tank

Fault phenomenon: In the process of pumping ash to the powder tank by bulk cement truck, there is powder coming out from the top of the cement tank.

Cause analysis: The powder is transported to the powder tank by compressed air, after the compressed air delivers the powder to the powder tank, it will be discharged to the air through the filter element of the dust remover at the top of the tank. When the pressure reaches the opening pressure of the safety valve at the top of the tank, the safety valve opens and the compressed air and powder are discharged to the atmosphere through the safety valve, resulting in the phenomenon of ash. In addition, due to the failure of the material level meter, the powder material continues to be fed after it is full, and the phenomenon of ash bubbling from the top of the tank will also occur.

Processing process:

1、 Check the condition of the dust collector cartridge on the top of the tank and clean it up. 

2、 Once the phenomenon of ash bubbling occurs, the powder around the safety valve must be cleaned to avoid the powder being wet and clumped by rainwater to block the safety valve. 

3、 If the powder is overfilled with ash, the reliability of the upper material level meter and material full alarm device must be checked.

Belt slipping in rainy day

Fault phenomenon: In rainy days, the inclined belt slips when running with load.

Cause analysis: In rainy days, the moisture in the aggregate and the exposed part of the belt is easily wet, the belt is wet, especially the inner ring is wet, which reduces the friction coefficient between the belt and the transmission drum, so that the torque transmitted by the drum to the belt is reduced, and the torque is less than the torque required for the belt material transportation, the belt will slip.

Processing process:

1、 Increase the belt tensioning device counterweight or tighten the belt adjusting screw, increase the positive pressure between the belt and the drum, so as to achieve the friction between the transmission drum and the belt. 

2、 Adjust the tensioning roller near the transmission drum, increase the belt in the transmission drum wrap angle, increase the friction. 

3、 Cut straight groove in the drive roller cladding layer to increase the friction coefficient. 

4、 If the first 3 methods can not be solved, it is necessary to replace the anti-skid roller.

Additive pump not on

Fault phenomenon: admixture pump work when the pump is not on the admixture. 

Cause analysis:

1、 There are air bubbles in the admixture pump. 

2、 Insufficient material in the admixture box. 

3、 Admixture pump impeller damage. 

Processing process:

1、 Disassemble the admixture vent screw, discharging the air bubbles in the admixture. 

2、 Add admixture to the admixture box.

3、 Check the condition of admixture impeller, and replace the spare parts according to the situation.

Belt damage

Fault phenomenon: After using one end of time, the belt surface appears degumming, cracking, scratching and other phenomena.

Cause analysis: If the metal belt cleaner is not adjusted in time, it is easy to damage the belt and cause the rubber on the belt surface to fall off. The cleaner is not installed correctly, and the relatively sharp debris stuck between the cleaner will damage the belt. The belt itself is not good quality, also easy to have the above defects.

Processing process: Once the belt has defects such as debonding, cracking and scratching, it should be repaired in time. When the belt is damaged, the first thing to do is to solve the factors causing the belt damage, such as the cleaner is damaged, then you need to adjust or replace the cleaner immediately, and then repair the belt in time. Belt damage is very small, available belt repair adhesive on-site repair. When the belt damage surface is large or serious local damage, the local damage to the belt can be removed, replace a section of the belt, with a vulcanizing machine for gluing. If the belt damage is not dealt with in a timely manner, the damage spreads to the whole belt, there is no repair value, only the whole replacement.

Belt conveying uneven aggregate

Fault phenomenon: the aggregate weighs the material unloaded to the belt with accumulation, causing the belt to loose material, or the aggregate conveyed on the belt has vacancies, causing the pebbles to loose material. 

Cause analysis: The order and time interval of unloading a variety of aggregates from batching station to belt can be adjusted at any time. The general unloading order requires the last unloaded aggregate to be sand, and the unloading time interval requires the tail of the former aggregate falling on the belt just coincides with the head of the latter aggregate falling on the belt. If the time interval is too short, there will be overlapping piles of the former kind of aggregate and the latter kind of aggregate, and too many piles will cause loose material, if the time interval is too large, there will be empty space between the two kinds of aggregate, and the former kind of material, if it is pebble, will roll on the belt and fall down.

Processing process: 

1、 Adjust the discharging order of the aggregates to ensure that the sand is the last to be discharged.

2、 Adjust the discharging time interval of various aggregates according to the distribution of aggregates on the belt to ensure continuous and even distribution of materials on the belt. Time interval generally needs to be adjusted several times.

3、 Concrete mixing plant troubleshooting method

The pressure of the pressure reducing valve in the air source triplex cannot be adjusted.

Fault phenomenon: rotate the pressure reducing valve adjusting hand wheel, but the pressure cannot be adjusted.

Cause analysis:

1、 The direction of import and export of pressure reducing valve is reversed.

2、 The spool embedded in foreign objects or the spool on the sliding parts of foreign objects stuck.

3、 Regulating spring, reset spring, diaphragm, rubber gasket on the spool, etc. damaged. 

Processing process:

1、 Check whether the installation direction of import and export of pressure reducing valve is correct. 

2、 Disassemble and check the spool and related parts, and clean the debris on the parts.

3、 If damaged by the parts, replace the pressure reducing valve.

The oil mister in the air source triplet does not drip oil or the amount of oil dripping is too small

Fault phenomenon: compressed air flow, but the oil misters do not drip oil or drip oil is very small. 

Cause analysis:

1、 The oil atomizer import and export direction installed in reverse.

2、 Oil channel blockage.

3、 Oil injection plug gasket damage or oil cup sealing gasket damage, so that the upper cavity of the oil cup can not be pressurized.

4、 The gas channel is blocked, the upper chamber of the oil cup is not pressurized.

5、 The throttle valve is not opened or not open enough.

6、 The viscosity of oil is too large. 

Processing process:

1、 Check the installation direction of the import and export of oil misters. 

2、 Stop the gas, disassemble and clean the oil channel; replace the gasket and seal; clean the gas channel. 

3、 Adjust the opening degree of throttle valve. 

4、 Replace the lubricant with less viscosity.

Air compressor starts frequently

Fault phenomenon: In the process of work, the air compressor starts frequently. 

Cause analysis:

1、 The pressure difference of the air compressor is too small. 

2、 Serious air leakage of the air circuit system. 

Processing process:

1、 Check the differential pressure of the air compressor and adjust it, generally 0.2MPa. 

2、 Check whether the air tightness of the air circuit system meets the requirements, and deal with the air leakage parts.

The magnetic switch on the cylinder cannot be closed or sometimes cannot be closed

Fault phenomenon: When the cylinder is closed or opened in place, the magnet is close to the resignation switch, but the word switch does not close or sometimes can not close. 

Cause analysis: 

1、 Power supply failure; 

2、 Poor wiring; 

3、 Magnetic switch installation position offset; 

4、 Strong magnetic field around the cylinder; 

5、 The cylinder temperature is too high or magnetic switch parts temperature higher than 70 degrees; 

6、 Magnetic switch by the impact, sensitivity reduced; 

7、 Magnetic switch instantaneous through a large current and disconnected.

Processing process: 

1、 Check whether the power supply is normal; 

2、 Check whether the wiring parts are loose; 

3、 Adjust the magnetic light installation position; 

4、 Add magnetic plate; 

5、 Cool down; 

6、 Replace the magnetic switch.