There will be some issues that everyone should pay attention to during the safe production of the printing workshop. Today, the plastic bag
will talk to you about some preventive measures in the printing workshop: The gravure coating workshop caught fire and exploded, and the organic solvent and oxygen caused intense chemistry. To react, three conditions must be met at the same time: 1. The VOC concentration is greater than 100% of the LEL, that is, it exceeds the lower explosive limit. 2. There is an ignition source, that is, the local temperature exceeds the ignition point of the solvent. 3. There is sufficient oxygen near the burning point. All fire accidents are the result of these three necessary conditions simultaneously. Preventive measures are nothing more than avoiding the three necessary conditions from appearing at the same time. Because oxygen in the air is generally sufficient, it is normal to avoid the occurrence of the first two conditions at the same time, and it is best not to appear at all. The places with high VOC concentration in the gravure coating workshop are: 1. Inside and top of the ink tank or glue tank. Therefore, if you use an electric ink suction pump, you must use an explosion-proof motor or an air pump. 2. Near the coating head. Due to the continuous stirring of the coating roller, the ink glue tank and the plate roller have a higher concentration around it. If there is electrostatic discharge, it is easy to catch fire. 3. Inside the oven where the printing coater is closer to the feed inlet. In particular, most of the solvents now use fast-drying solvents, and the heating temperature is relatively high. Most of the solvents evaporate in the oven closer to the feed inlet, where the concentration is the highest. If the intake and exhaust air volume is insufficient and the coating is thicker, the amount of solvent is Larger, it may exceed the lower explosive limit. Preventive measures: 1. Extinguish the fire source. The printing plant does not allow smoking and other activities with open flames in the workshop. The most prone to occur are sparks caused by static electricity and sparks caused by collision or friction. Especially in the above three places, there should be no sparks. Therefore, the ink tank or glue bucket, near the coating head, and the inside of the oven where the printing coater is closer to the feed inlet must be done to eliminate static electricity. Static elimination is to eliminate the local high voltage on the surface of the material. At present, there are methods of grounding through a conductor and elimination of static electricity. The electrostatic generator elimination method uses the generator to generate positive and negative ions to neutralize the voltage on the material, and the electrostatic generator itself is a discharge process, so it should not be too close to the place with high VOC concentration, which inherently has hidden dangers. Advocate adoption. The method of grounding through a conductor is economical and practical. Generally, copper wire, copper wire, aluminum foil is used to approach the material, or an electrostatic brush is installed and then the copper wire or electrostatic brush is grounded. The most likely problem is that the copper wire or electrostatic brush is connected to the ground wire through the frame or guide roller. The insulation may be caused by the corrosion and oil on the contact surface of the frame, or the ground wire of the machine itself may be broken or the connector may fall off and cause failure. . It is recommended to use dedicated wiring to directly connect the copper wire or electrostatic brush to the ground wire. Friction fire is caused by mutual collision or friction. There have been accidents where the metal above fell and hit the ink tank to cause sparks to ignite the solvent and fire. This should be paid attention to. When the air humidity is high, the static electricity on the film or paper is likely to leak through the air. Therefore, maintaining a proper humidity in the workshop also plays a role in eliminating static electricity. 2. A VOC concentration alarm is installed in the oven. Once the concentration is too high, the VOC concentration alarm will automatically alarm. 3. Install a carbon dioxide fire extinguishing device, once a fire occurs, it will automatically spray carbon dioxide to extinguish the fire. 4. Do not put glue, solvent and ink near the gravure printing machine. It is best to isolate it from the machine to prevent the surrounding solvent from igniting and exploding in case of fire, which may cause a major accident. It is better to keep the spare materials far away from the more dangerous places, and the quantity should not be too much. 5. Ensure that the air inlet volume of the oven cannot be lower than a minimum value, and the VOC concentration should be less than 25% of the LEL at the minimum air volume. The gravure printing machine, coating machine, and laminating machine oven will not catch fire or explode under normal circumstances due to the large amount of air intake and exhaust. Fires and explosions are often caused by insufficient oven temperature, operators closing the intake and exhaust air doors too small, or when the exhaust fan does not work due to line failure or belt breaks, and the material has a high VOC content. 6. There is a pressure relief port on the oven. Once the pressure of the oven rises to a certain degree, the pressure relief port will automatically open, making the oven unable to burst. The above preventive measures are hoped to be helpful to everyone, and to be able to make safer production better.
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