Concrete mixing plants are often used in large and medium-sized water conservancy, electric power, bridge and other projects with large quantities of concrete, long construction periods, and concentrated construction sites. However, with its wide application, some failures will inevitably occur. Today, the editor introduces the common faults and treatment methods of concrete mixing plants.
1. Gas source failure
(1) The failure of the air compressor includes: damage to the check valve, severe wear of the piston ring, damage to the intake valve plate and blockage of the air filter.
To determine whether the check valve is damaged, just turn off the power after the air compressor automatically shuts down for more than ten seconds, and turn the large tape wheel with the hand wheel. If it can turn around easily, it means that the check valve is not damaged. ; On the contrary, the check valve is damaged; in addition, it can also be judged from the exhaust situation of the exhaust port below the automatic pressure switch, generally after the air compressor automatically shuts down, the exhaust should be stopped after about ten seconds. If the exhaust continues until the air compressor starts again, then the check valve is damaged and must be replaced.
When the pressure of the air compressor rises slowly and is accompanied by a string of oil, it indicates that the piston ring of the air compressor has been seriously worn and should be replaced in time.
When the intake valve is damaged or the air filter is clogged, it will also make the pressure of the air compressor rise slowly (but there is no oil stringing phenomenon). During the inspection, you can put your palm on the air inlet of the air filter. If there is hot air, it means that the air intake valve is damaged and must be replaced. If the suction power is small, it is generally caused by the dirty air filter. The filter should be cleaned or replaced.
(2) The failure of the pressure reducing valve includes: the pressure is not adjusted high, or the pressure rises slowly.
If the pressure is not adjusted high, it is often caused by a broken pressure spring or a ruptured diaphragm, and it must be replaced with a new one. The pressure rises slowly, which is generally caused by the clogged filter, and it should be removed and cleaned.
(3) Pipeline faults include: leakage at the pipe joint, rupture of the hose, accumulation of condensed water, etc.
If the pipeline joint leaks and the hose ruptures, the leak location can be judged from the sound, and it should be repaired or replaced in a timely manner; if condensate accumulates in the pipeline, it should be drained in time. The feature is that the condensate in the north is easy to condense The air path is blocked by ice.
(4) The failures of the compressed air treatment assembly (triple) are: failure of the oil-water separator, failure of the pressure regulating valve and the lubricator.
The failure of the oil-water separator is divided into the following situations: the filter element is clogged or damaged, and the moving parts of the sewage valve are not flexible. During the work, the filter element must be cleaned frequently to remove the oil and impurities in the drain.
The failure of the pressure regulating valve is the same as the above "(2) Failure of the pressure reducing valve".
The failure phenomena of the lubricator are: no oil dripping, water deposited on the bottom of the oil cup, and the sealing ring at the mouth of the oil cup is damaged. When the lubricator does not drip oil, it should be checked whether the air flow rate of the air inlet is lower than the fogging flow rate, whether there is air leakage, whether the oil quantity adjustment needle valve is blocked, etc.; When the sealing ring is damaged, it should be replaced in time.
Second, the cylinder failure
Due to improper assembly of the cylinder and long-term use, the pneumatic actuator (cylinder) is prone to internal and external leakage, insufficient output force and unstable movement, poor cushioning effect, damaged piston rod and cylinder head and other fault phenomena.
(1) The internal and external leakage of the cylinder is generally caused by the eccentric installation of the piston rod, the insufficient supply of lubricating oil, the wear or damage of the sealing ring and the sealing ring, the impurities in the cylinder and the scratches on the piston rod. Therefore, when the internal and external leakage of the cylinder occurs, the center of the piston rod should be readjusted to ensure the coaxiality of the piston rod and the cylinder; the reliability of the lubricator must be checked frequently to ensure that the actuator is well lubricated; when sealed When the ring and seal ring are worn or damaged, they must be replaced in time; if there are impurities in the cylinder, they should be removed in time; if there are scratches on the piston rod, they should be replaced with new ones.
(2) The insufficient output force and unstable movement of the cylinder are generally caused by the stuck piston or piston rod, poor lubrication, insufficient air supply, or condensate and impurities in the cylinder. In this regard, the center of the piston rod should be adjusted; check whether the operation of the lubricator is reliable; whether the air supply line is blocked. When there is condensate and impurities in the cylinder, it should be removed in time.
(3) The cushioning effect of the cylinder is not good, usually due to wear of the cushion seal or damage of the adjusting screw. At this time, the sealing ring and adjusting screw should be replaced.
(4) The damage of the piston rod and cylinder head of the cylinder is generally caused by the eccentric installation of the piston rod or the failure of the buffer mechanism. For this, the center position of the piston rod should be adjusted; replace the buffer seal or adjustment screw.
3. Failure of the directional valve
The faults of the reversing valve are: the valve cannot be reversing or the reversing action is slow, the gas leaks, the electromagnetic pilot valve is faulty, etc.
(1) The reversing valve cannot be reversed or the reversing action is slow, which is generally caused by poor lubrication, the spring being stuck or damaged, or oil or dirt stuck to the sliding part. In this regard, you should first check whether the operation of the lubricator is normal; whether the viscosity of the lubricating oil is appropriate. If necessary, replace the lubricant, clean the sliding part of the directional valve, or replace the spring and directional valve.
(2) After a long period of use, the directional valve is prone to wear of the spool seal ring, damage to the valve stem and valve seat, resulting in gas leakage in the valve, slow movement of the valve, or failure to switch normally. At this time, the sealing ring, valve stem and valve seat should be replaced, or the directional valve should be replaced with a new one.
(3) If the inlet and exhaust holes of the electromagnetic pilot valve are blocked by sludge and other debris, the sealing is not tight, the movable iron core is stuck, and the circuit is faulty, etc., which can cause the directional valve to not change normally. For the first three cases, the sludge and impurities on the pilot valve and movable iron core should be cleaned. Circuit faults are generally divided into control circuit faults and electromagnetic coil faults. Before checking the circuit failure, the manual knob of the reversing valve should be turned a few times to see if the reversing valve can be reversed normally under the rated air pressure. If it can be reversed normally, the circuit is faulty. During the inspection, the voltage of the electromagnetic coil can be measured with a meter to see if the rated voltage is reached. If the voltage is too low, the power supply in the control circuit and the associated stroke switch circuit should be further checked. If the directional valve does not switch normally at the rated voltage, you should check the solenoid coil connector (plug) for looseness or improper contact. The method is to pull out the plug and measure the resistance of the coil (generally should be between several hundred ohms and several thousand ohms). If the resistance is too large or too small, it means that the electromagnetic coil is damaged and should be replaced.
4. Component failure
The failures of pneumatic transmission components mainly include: oil mister failure, automatic sewage drain failure, muffler failure, etc.
(1) The failure of the oil mist device is: the adjustment amount of the adjustment needle is too small, the oil path is blocked, and the air leakage of the pipeline will make the liquid oil droplets unable to atomize. In this regard, the clogged and leaked areas should be dealt with in time, and the amount of dripping oil should be adjusted to 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 removed in time.
