Hazardous factors in production
Dangerous and harmful factors in textile factories include: static electricity and dust, production The process is prone to multiple sources of ignition. The specific manifestations are:
1 Friction and impact sparks within the equipment
Due to mechanical operating parts inside the equipment Lack of lubrication causes friction and heat; materials, hard impurities or fallen parts collide with the inner wall of the equipment to create sparks. When hard objects with rough surfaces violently collide or rub against each other, high-temperature solid particles are generated by the impact or friction of Mars and fall off. If the particle diameter of Mars is 0.1~1mm, the energy it carries can reach 1.76~1760mJ, which is enough to ignite combustible dust. According to statistics, only 57% of explosion accidents caused by friction and impact in crushing and grinding equipment
2 Electric Sparks and Static Electric Sparks
Electric sparks caused by electrical equipment failures are a common source of ignition, and there are many accident cases. During the mixing and conveying of materials, crushing and grinding, the friction and impact between the powder and the pipe wall, equipment wall, and between the particles of the powder will generate static electricity. The electric charge on some dust surfaces can reach 10.6~10.7C/cm2. Under appropriate conditions, its electrostatic voltage can be as high as thousands to tens of thousands of volts.
3 Smoldering and spontaneous combustion of deposited dust
Deposited on heated surfaces such as lighting devices and motors Dust on the hot surface of mechanical equipment will smolder after being heated for a period of time, and may eventually turn into an open flame and become the ignition source of dust explosions. The layer thickness of dust that is most susceptible to smoldering ranges from 10 to 20 mm. Combustible dust also has a tendency to spontaneously ignite in the deposited state, because the dust particles contact the air and undergo an oxidation and exothermic reaction. Under certain conditions, the heat cannot be fully dissipated, and the temperature in the powder layer will rise, causing spontaneous combustion. Dust accumulated in equipment cracks and pipeline corners for a long time is prone to spontaneous combustion. This is why local fire accidents often occur in many textile factories.
Processes prone to dust explosions
1 Crushing process
Crushing process The processes include: extrusion, impact, grinding, splitting, bending, tearing and other methods. In general, crushing and grinding operations require the simultaneous use of multiple forces. The crushing operation will raise a large amount of dust due to mechanical force, and the dust suspended in the equipment is often within the explosive concentration range. And the action of various forces is more likely to produce friction, impact sparks, static electricity and other ignition sources, leading to the occurrence of dust explosions. This type of equipment, such as jaw crushers, roller crushers, ball mills, colloid mills, etc., are all dangerous equipment with dust explosions.
2 Separation process
A typical separation device is a cyclone separator. Like other similar devices, the main principle of separation is to use the centrifugal force acting on the materials during the rotation of the air flow to separate the materials according to their weight. Under the action of wind, the dust in the separator is in a suspended state. At this time, if there is an ignition source with sufficient energy, an explosion accident will inevitably occur.
3 Dust removal process
The principle of dust filter equipment is usually to use filter materials to remove gases from the gas flow. The particles are blocked, and the dust is in a suspended state before dust removal. Not only that, when the filter material is cleaned, the dust adhering to the filter material is in a suspended state again. If there happens to be an ignition source with sufficient energy, dust will also occur. Explosion accident.
4 Conveying process
In order to achieve continuity and automation of production, factory production usually uses automatic conveying , and dust is transported by pneumatic conveying pipelines due to its characteristics. During the conveying process, industrial dust is in a fluffy suspended state, which has the main conditions for dust explosion. It is extremely dangerous as long as there is a suitable ignition source, and the conveying pipeline is not related to separation and dust removal. The equipment is connected and can easily cause explosions, causing greater casualties and losses. Especially when fiber dust and mud dust pass through the pipeline quickly, friction occurs between the fiber dust and static electricity is generated. When the electrostatic load value reaches a certain level, it is very easy to produce sparks, burn or explode. In the early 1980s, an explosion occurred in the Harbin Flax Factory. The incident is an iron lesson.
5 Cleaning and purging process Dust will inevitably escape from the equipment during the production process. This dust accumulates in the factory and If the surface of the equipment is not cleared in time, it is easy to cause an explosion accident after reaching a certain concentration and flying up. During the operation of the blowing and suction device, it is also easy for dust to fly, forming a suspended explosion condition. This situation generally rarely occurs in textile factories, but it is common in some metal processing companies. The explosion that occurred at Kunshan Zhongrong Metal in July 2014 was mainly an explosion accident that occurred after dust accumulated to a certain critical point.
Safety technology to prevent fire and dust explosion
1 Controlling dust concentration
Equipment in each production process It should be sealed and the operation room should have good ventilation equipment to reduce the dust content in the air. When supplying equipment with powder, the amount of air in the equipment and pneumatic conveying devices must not exceed 30% under normal operating conditions, and the maximum oxygen content must be 6% to 8%. For equipment operating within the explosive limit of dust concentration, the dust concentration can be increased by reducing the volume of the container to exceed the upper explosion limit to prevent dust explosion and also weaken the power of the explosion.
2 Reduce dust deposition
Equipment in each section should be isolated in a separate room; Floor, wall:p>
Aiming at the dangerous and harmful factors static electricity and dust in domestic cotton spinning mills, as long as on-site management is strengthened, equipment maintenance is strengthened, and targeted measures are taken in key parts, good application effects will be achieved.
Reduce motor friction, lower the electrostatic charge value, reduce sparks caused by mutual friction, and increase grounding in the air-conditioning part, and for dust filter devices that are exposed to more dust and those with higher friction frequencies. Parts, increase the conductivity to prevent accumulation of static electricity, use anti-static filter material with better conductivity to avoid static electricity generated when the filter material and suction nozzle rub, which can greatly reduce the incidence of fire.
Achieve high-precision dust removal of dust filter equipment, reduce the dust concentration in the workshop, and effectively control the occurrence of dangerous and harmful factors at low cost, while achieving high dust filtering efficiency of dust filter equipment and improving the current situation. With the sealing performance of the equipment and the high density of the filter material, it will be the best choice.
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