Antistatic bulk bags, also known as conductive bulk bags, can be divided into four categories according to the degree of electrostatic ignition hazards and their internal structure. This classification method is widely used by many people in Europe. In June 2003, the European Committee for Electrotechnical Standardization CENELEC published the document CLC/TR50404 "Electrostatics-Code of Practice for the avoidance of hazards due to static electricity". This is a very comprehensive standard for electrostatic operation in various fields of industry, and one chapter points out the electrostatic safety use specifications of bulk bags in detail. The standard divides bulk bags into four categories: Type A, Type B, Type C, and Type D.
Type A antistatic bulk bags have no special electrostatic safety characteristics, so they are not recommended for handling sensitive flammable dusts and powders. In addition, they cannot be used in places where dust clouds or flammable solvent vapors are present. This type of bulk bag is usually woven with ordinary woven polypropylene cloth and is an insulator. Sometimes, depending on the requirements of use, Type A bulk bags are lined with inner bags or coated on the surface.
Type B antistatic bulk bags are similar to Type A and are also made of ordinary woven polypropylene cloth. However, the breakdown voltage of the woven cloth of Type B bags cannot be higher than 4KV. This means that Type B bulk bags will not produce propagating brush discharges. This is an important classification, that is, the few discharges that can be produced on bulk bags are low-energy brush discharges. If propagating brush discharges can be excluded and the maximum energy of brush discharges is 4mJ, it is reasonable to believe that this type of bulk bag is safe for flammable gas environments with a minimum ignition energy of no more than 4mJ. Similarly, this type of bulk bag is safe for combustible dusts with an ignition energy of no more than 4nd. However, Type B bulk bags cannot be used in flammable hydrocarbon vapor environments. It must be noted that some factory-made bulk bags meet the classification criteria for Type B and still cause accidents. For example, when tested by a testing agency, it meets the Type B standard, but in actual use, due to the coating on the liner bag and the bag surface, the breakdown voltage is higher than 4KV, which makes the Type B bag become Type A.
Type C antistatic bulk bags are designed for sensitive and flammable environments, including flammable hydrocarbon solvent vapor environments. This type of bulk bag is made of conductive cloth or woven cloth coated with conductive/anti-static coating. Conductive cloth is woven cloth with conductive fibers/flat wires interwoven. In some designs, the conductive wires are parallel and the spacing is 20mm. In other designs, the conductive wires are woven into a network with the wires intersecting vertically. The conductive wires are usually conductive flat wires or conductive metal wires.
Type D conductive bulk bags have antistatic or static dissipative properties and do not require grounding. Most Type D bulk bags on the market today are made of thin semi-conductive wires interwoven into the woven cloth. Unlike the design of Type C bulk bags, these semi-conductive wires are parallel but not cross-linked. This type of container bag may have an anti-static coating, so we usually call Type D container bags conductive container bags. Due to its complex manufacturing process, its price will be about 20% higher than the above three types.