Big Bag types A, B, C and D: how to choose the right one

When a powder falls into a Big Bag, or flows out of it, static electricity builds up. With sand or grains nothing usually happens. But with flour, sugar, powdered chemicals or fine minerals, a discharge can ignite a dust cloud; and if there are solvents or gases in the air as well, the risk is higher. That is why the industry classifies Big Bags into four types.

Type A: no protection

This is the standard polypropylene Big Bag. It has no static-control features, so it should only be used with non-flammable products in areas without flammable dust or gases. It is the most economical and the most common for coarse minerals, sand and aggregates.

Type B: prevents the most dangerous discharges

It is made from fabric with a low breakdown voltage, which prevents the highest-energy discharges. It is suitable for flammable powders as long as there are no flammable gases or vapors in the area. It does not need grounding.

Type C: conductive, always grounded

It has interwoven conductive threads forming a grid over the whole fabric. That grid must be grounded during filling and discharge, so the charge flows to earth instead of building up. It is suitable for flammable powders and also where flammable gases or vapors are present.

Note:an ungrounded Type C is more dangerous than a Type A, because the conductive grid stores the charge. If your plant cannot guarantee grounding in every operation, Type C is not the right choice.

Type D: dissipative, no grounding

It uses a special fabric that safely releases the charge into the air, without sparks, and needs no grounding. It covers the same uses as Type C, with the advantage of not depending on the operator to connect the cable.

How to choose in three questions

1. Is the powder flammable? If not, and the area is safe, a Type A is enough.
2. Are there flammable gases, vapors or solvents where you fill or discharge? If not, a Type B is usually enough.
3. If there are, can you guarantee grounding in every operation? If you can, Type C; if not, Type D.

No antistatic Big Bag works properly if its surface is wet or covered in oil. And the final decision must be validated by your plant’s safety department. At NEGASAC we manufacture Type B, suitable for flammable powders in areas without flammable gases or vapors; learn more on our page aboutantistatic Big Bags.