Conductive bags need special consideration before using them.
When filling and emptying, some products create a static charge which can arc or spark and cause an explosion. This is likely to be located in potentially combustible dust atmospheres.
A lot of the products that generate static electricity are chemicals that are highly flammable but more common products, such flour (in large quantities), also produce static electricity.
Many companies are unsure of what bag to use to ensure they are covering their risk. Here are the basics on what each bag type offers.
Type A – this bag offers no conductive properties.
Type B – this is considered to be the standard bulk bag that is most commonly used in general packaging. The fabric is polypropylene and has a breakdown voltage of less than 4 Kv. It has no earthing incorporated within the bag but may conduct small amounts of static when on the ground.
Type C – this is the most commonly used ‘anti-static’ bag. When the fabric is woven, conductive threads are incorporated to inter-connect across the seams. This style of bag would generally have earthing lugs at the top and bottom of the bag to enable earthing equipment to be attached. This bag requires earthing.
Type D – this bag is considered to have conductive threads that do not require earthing. However, The Swiss Institute of Safety and Security carried out a gas ignition test with a metal drum filled with flammable liquid and a bulk bag made to Type D requirements. They found that a spark discharge from the bag ignited the gas, concluding that the bag was not suitable for flammable products without earthing being present. The type D bag is still promoted as a safe bag but does need careful consideration before using it.
The last type of Anti-static bag is CROHMIQTM . This bag is considered to be the best anti-static bag on the market. The fabric is resistant to the build-up of static electricity. A CROHMIQTM bag is easily the most recognised brand for non-grounded static resistant bags.
With all anti-static bags, we recommend that machinery and staff are all grounded to reduce the risk of electrostatic sparks but there is also a range of equipment available that will assist with the discharge of static.
If you are unsure which type of bag is best suited for your process, give us a call and one of our Team will be happy to help.
