Type A FIBC bulk bags

Plain fabric, and what that means

Woven polypropylene is a good insulator. When product slides into a bag or pours out of one, the friction leaves electric charge on the fabric and on the product, and plain fabric gives that charge nowhere to go. In a Type A bag nothing is woven in to drain it, dissipate it or keep it from building up.

For gravel or salt in an open yard that is mostly a nuisance: an operator may get a shock touching the bag. Near flammable dust, vapour or gas, a discharge from charged fabric can ignite it. That's the line the type is drawn on, and why a Type A bag belongs only where nothing around it can burn.

You can't see or smell the charge. It depends on how fast product moves, how dry the air is, how fine the particles are and what the material is made of, which is why a fill that never caused trouble through a humid summer can start zapping operators in a dry winter. A Type A bag changes none of that; choosing it only means the job never involved anything that could ignite.

It's the area too, not only the product

Buyers sometimes check the product, find it isn't flammable, and order Type A. That's half the question. If the bag is emptied into a mixer that holds solvent, or filled in a building where another process throws off combustible dust, the room is the problem even if the sand isn't. Follow your site's hazardous-area assessment, and check IEC 61340-4-4 and the bag maker's documents when anything flammable is nearby.

If the answer is unclear, don't settle it with a cheaper bag. Ask whoever owns the assessment, then order the type they name.

• Is the product itself combustible or flammable?
• Does any neighbouring process release flammable dust?
• Is solvent, fuel or gas used, stored or vented within reach?
• Do discharge points feed closed vessels that may hold vapour?
• Who signs off the answer, and where is it written down?

Every style of build

Type A describes the fabric, not the shape. You can have a Type A spout top, duffle top or open top, a flat or spout bottom, four-panel, U-panel or circular body, coated or not, with or without a liner. Its construction and testing fall under ISO 21898, the standard for FIBCs carrying non-dangerous solids. The safety factor is separate again: a 2,200 lb SWL bag at 5:1 was tested to 2,200 x 5 = 11,000 lb, and at 6:1 to 13,200 lb.

Humidity, temperature and rough handling don't change a Type A bag's category, but they do shorten its life. Keep bales indoors and out of sunlight, and check each bag for cuts, rodent damage and loose loop stitching before it goes on the frame. Users shouldn't repair a bag, and one that has sat in the sun for a long spell shouldn't be lifted.

Type A next to B, C and D

Each step up adds something to the fabric. Type B uses a low breakdown voltage fabric that stops propagating brush discharges. Type C weaves in conductive threads that must be connected to ground. Type D uses static-dissipative fabric that sheds charge without a ground. None of them is a general upgrade to buy just in case; each fits a defined set of conditions, and Type C is unsafe when its ground isn't connected.

Shipping and asking for Type A

Type A bags fold, bale and palletize like any other style, and they're the type most used bags come as, which suits aggregate and salt work after inspection. For the quote, give us the product, the area check, the top and bottom, the SWL and the delivery ZIP. We line up the pallets, the truck and a day the carrier confirms.

Multi-trip Type A bags exist for closed loops, where one plant fills, ships, recovers and refills its own bags under an inspection routine. Multi-trip standard-duty bags must reach 6 times SWL in the final destruction test and pass a 4,000 kg, 6-hour compression test. Those are the 6:1 bags. Anything labeled 5:1 is single trip, and the maker recommends it not be reused.