Common faults in concrete mixing plants

Common faults of concrete mixing plants
The pneumatic system is the execution device of the concrete mixing plant. Its function is to timely open and close each aggregate bin, mixer discharge door, and cement scale discharge door according to the instructions issued by the industrial microcomputer, break the arch of the cement in the cement bin, blow and mix the additives, ensure accurate measurement of various aggregates, cement, and additives, and complete the loading task of finished materials. Only by using and maintaining the system correctly can the high production rate and good economy of the entire machine be guaranteed.
There are five common faults in mixing plants:
Air source malfunction
Common faults in air sources occur in air compressors, pressure reducing valves, pipelines, compressed air processing components, etc.
(1) Common faults of air compressors include damaged check valves, severe wear of piston rings, damaged intake valve plates, and clogged air filters.
After the automatic shutdown of the air compressor for more than ten seconds, turn off the power and manually rotate the large tape roller. If it can easily rotate once, it indicates that the check valve is not damaged, otherwise it is damaged; It can also be judged based on the exhaust situation of the exhaust port under the automatic pressure switch. If the air compressor continues to exhaust after automatic shutdown until it starts again, it indicates that the check valve is damaged and needs to be replaced. When the pressure of the air compressor rises slowly and accompanied by oil leakage, it indicates that the piston ring of the air compressor has been severely worn and should be replaced in a timely manner. When the intake valve plate is damaged or the air filter is clogged, it will also cause the pressure of the air compressor to rise slowly (but without oil leakage). Place your palm on the air intake of the air filter. If there is hot air blowing outwards, it indicates that the intake valve is damaged and needs to be replaced; If the suction is small, it is usually caused by a dirty air filter, and the filter should be cleaned or replaced.
(2) Pressure reducing valve malfunction. If the pressure cannot be adjusted high, it is often due to the breakage of the pressure regulating spring or the rupture of the diaphragm, which needs to be updated; The pressure rises slowly, usually due to clogged filter screens, and should be removed and cleaned.
(3) Pipeline malfunction. When there is a joint leak or hose rupture, the location of the leak can be determined by sound. If condensed water accumulates in the pipeline and easily freezes, blocking the air path, it should be promptly eliminated.
(4) Compressed air processing component malfunction. The filter element of the oil-water separator is blocked or damaged, and the moving parts of the drain valve are not flexible. Regularly clean the filter element to remove impurities such as oil stains from the drain valve. The oil mist device does not drip oil, moisture accumulates at the bottom of the oil cup, and the sealing ring of the oil cup mouth is damaged. It is necessary to check whether the air flow rate at the inlet is lower than the fogging flow rate, whether there is air leakage, and whether the oil volume adjustment needle valve is blocked.

Cylinder malfunction
(1) Leakage inside and outside the cylinder is generally caused by eccentric installation of the piston rod, insufficient supply of lubricating oil, wear or damage of the sealing ring and sealing ring, impurities in the cylinder, and scratches on the piston rod. The center position of the piston rod should be readjusted, and the reliability of the oil mist device should be checked regularly to promptly remove impurities from the cylinder; When there are scars on the piston rod, a new part should be replaced.
(2) Insufficient output force and unstable movement of the cylinder are generally caused by the piston or piston rod being stuck, poor lubrication, insufficient air supply, or condensation water and impurities in the cylinder. The center position of the piston rod should be adjusted; Check the reliability of the oil mist device operation; Whether the gas supply pipeline is blocked should be promptly cleaned of condensed water and impurities in the cylinder.
(3) The poor buffering effect of the cylinder is generally due to wear of the buffering sealing ring or damage to the adjusting screw. The sealing ring and adjusting screw should be replaced.
(4) Damage to the piston rod and cylinder head is generally caused by eccentric installation of the piston rod or ineffective buffering mechanism. The center position of the piston rod should be adjusted in a timely manner, and if necessary, the buffering sealing ring or adjusting screw should be replaced.
Directional valve
(1) Cannot reverse or reverse slowly. First, check if the oil mist device is working properly; Is the tolerance of lubricating oil appropriate. If necessary, replace the lubricating oil, clean the sliding parts of the directional valve, or replace the spring and directional valve.
(2) Wear of the valve core sealing ring, damage to the valve core and seat, gas leakage inside the valve, slow movement or inability to change direction normally, the sealing ring, valve core and seat should be replaced, and if necessary, a new directional valve should be replaced.
(3) The inlet and outlet holes of the pilot solenoid valve are blocked by debris such as oil sludge, poorly sealed, the movable valve core is stuck, and there are circuit faults, all of which can cause the directional valve to fail to change direction normally. Oil sludge and other impurities on the pilot solenoid valve and movable valve core should be cleaned in a timely manner. Before checking for circuit faults, the manual knob of the directional valve should be turned a few times to see if the directional valve can change direction normally under the rated air pressure. If it can change direction normally, it is a fault in the circuit. During inspection, an instrument can be used to measure the voltage of the electromagnetic coil to see if it has reached the rated voltage. If the voltage is too low, further inspection of the power supply and related travel switch circuits in the control circuit should be carried out. If the reversing valve cannot reverse direction normally under rated voltage, the connector (plug) of the electromagnetic coil should be checked for looseness or loose contact. The method is to unplug the plug and measure the resistance value of the coil (usually between a few hundred to several thousand ohms). If the resistance value is too high or too low, it indicates that the electromagnetic coil is damaged and should be replaced.
Auxiliary components
(1) The adjustment amount of the adjusting needle of the oil mist device is too small, and blockages in the oil circuit, leaks in the pipeline, etc. can prevent liquid oil droplets from atomizing. It is necessary to promptly deal with the blockages and leaks, adjust the oil droplet amount, and make it reach about 5 drops/min. During normal use, the oil level in the oil cup should be kept within the upper and lower limits. The water deposited at the bottom of the oil cup should be promptly removed.
(2) The oil and moisture inside the automatic drain sometimes cannot be automatically removed, and should be disassembled for inspection and cleaning.
(3) When the muffler installed on the directional valve is too dirty or blocked, it will also affect the sensitivity of the directional valve, and the muffler should be cleaned regularly.
mechanical failure
The material gate shaft driven by the cylinder often gets stuck at the discharge port on the powder measuring hopper; The flap disc valve driven by the rack type cylinder is stuck, causing it to not close properly or not open. So it is necessary to regularly remove the powder lumps on the inner wall of the flipping disc valve.