Antistatic bulk bags, also known as conductive bulk bags, can be divided into four categories according to the degree of electrostatic ignition hazard 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 specifies 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 made of ordinary woven polypropylene cloth and is an insulator. Sometimes, according to the requirements of use, Type A bulk bags will use liner bags or surface coating treatment.
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 Type B classification criteria and still cause accidents. For example, when tested by a testing agency, it complies with 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, making the Type B bag become a Type A.