Spray drying tower system for testing of redispersible powders. The system was introduced from Denmark, produced by the company, model Production minor/12.5, drying tower by high-speed atomizer, hair dryer, flash dryer, cyclone separator, heating box, feeding system, packing pusher, air intake system , explosion-proof doors and control cabinets.
1. Sudden smoke and alarm during operation of the equipment
The reason for smoking and alarm is that the system inlet air filter burns. Immediately power off the site and extinguish the fire source. The inspection found that the inlet filter burned a large amount of ash; the control cabinet inlet air temperature display showed normal; the electric heater was damaged; and the receiving bucket contained a large amount of bulk material.
The system is in a dusty environment for a long time, and a large amount of dust adheres to the air filter element (paper), which causes the air inlet speed to be much lower than the process design requirement (2m3/s).
The temperature inside the heating box rises. When the temperature reaches the auto-ignition temperature of the filter element, the filter element will spontaneously ignite.
The signal feedback circuit is installed at the bottom of the heating box. After overheating, the temperature tester wire is damaged, the temperature feedback signal cannot be returned, the heating regulator is disconnected, and the automatic adjustment cannot be realized; the heater cannot be powered off in time, and a group of high-power heaters are burned; When the operator is powered off, some of the atomized material in the drying tower cannot be dried and condensed to form a block.
Bring the heater inlet pipe out of the production workshop to prevent the heating box filter from being stuck by dust adhesion to ensure the inlet speed of the heating box.
The installation method of the heating box temperature tester is modified, and only the probe is placed in the heating box, and the signal feedback line is insulated and flame-retardant protected, and is attached to the outside of the heating box.
The heater thermostat control loop is connected in series to the main control loop of the device. When the heater temperature is higher than the set temperature, the system can be powered off in time to avoid accidents.
2. High-speed atomizer violently vibrates to generate noise
High-speed atomizer, consisting of high-speed motor, material distributor, flash dryer, atomizing wheel, motor type VFS31.09- 24, speed 10000~30000r/min, running current 0.47A, made in Germany. During operation, the high-speed atomizer vibrates violently, giving a “click” sound, and the motor running current reaches 0.55A. After disintegration, it was found that the atomizer wheel and the material distributor were all intact, and the rear bearing seat of the motor showed cracks, which was about 8 mm long. The inner ring raceway of the rear bearing had a wear mark of 0.5 mm deep, and there was a burning blue phenomenon, and the cage was broken. At the same time, it was found that there was a slight rubbing trace between the rotor and the stator. The preliminary judgment is caused by poor lubrication during high-speed operation of the motor.
Detect the coaxiality of the motor rotor and do the dynamic balance test, in line with technical requirements. Repair the rear bearing housing of the motor with argon arc welding and perform correction processing. Replace the front and rear bearings of the motor (models HSS7002, HSS7004, FAG). During the test run, when the speed is at 20000r/min, there is a strong vibration and a “beep” sound, and the motor running current reaches 0.5A.
On-site inspection with the STEC CMS2977 service system. The measuring points are set at the front and rear bearings of the motor. Each point is taken in three directions: radial horizontal (H), radial vertical (V) and axial (A).
When the motor is unloaded and loaded, the vibration value of each point does not change significantly, indicating that the vibration is independent of the atomizing wheel and also independent of the material distributor.
The radial horizontal vibration and axial vibration of each measuring point of the motor are large, and the vibration at the rear bearing seat is significantly larger than that of the front bearing seat. It shows that there is obvious imbalance of the couple, which has a lot to do with the bearing.
Since the end face of the rear bearing housing of the motor is machined after welding, it is difficult to achieve the original bearing position accuracy requirement after machining. This will cause the clearance to increase and the severe vibration during operation.
The centrifugal force generated when the atomizing wheel rotates at a high speed is the unbalanced force of the rotor of the motor. Due to the radial play of the bearing, the balls in the unloaded area are unbalanced and abnormal sound and vibration will occur.
A corrugated spring (thickness 0.5mm, outer diameter 32mm, inner diameter 28mm) is attached to the rear bearing housing of the motor. After installation, the spring has a pre-tightening compression of 1.5mm, which compensates for the axial displacement of the bearing. When the rotor of the motor is changed by heat, the inner ring of the bearing moves with it, eliminating excess clearance of the bearing.
After the treatment, the motor has been running until now, and the vibration values of each measuring point are in a good range.
