We got a call from a customer the other day who asked us to evaluate a chronic dusting problem that occurs when they fill bulk bags with their fine powder product.  Turned out that it was more a much more complex situation than it sounded like on the phone!

A site visit revealed the problems symptoms.  As soon as a bag started to fill dust begins to escape along the seams at the top of the bag where the top panel is sewn onto the sides of the bulk bag.  The product was 'sifting' through the top panel seams.

This being a very fine powder, the sifting caused a significant cleanliness issue.  However, the customer finally decided to tackle this long standing issue because of the problem's potential impact on the health of operators and it's impact on profitability - product falling on the floor was not being paid for by customers!

A quick review of the situation revealed several potential root causes of the problem:

• Faulty bag inflation.  The customer inflates every bag prior to filling.  Initial observation indicated that once product began to flow into the bag, it appeared that the bulk bag remained 'taut'.  Was the inflation system continuing to force air into the bag during filling?  If so, the excessive positive air pressure in the bag that would result from the inflation system continuing to run during filling could easily overcome any treatment of the top panel seams designed to prevent sifting.
• Inadequate dust extraction.  As a bulk bag is filled the air in the bag is displaced by the product flowing into the bag.  A means of removing this displaced air must be provided or excessive positive air pressure in the bag may occur during filling.  Per the above, this could lead to sifting through the bulk bag's sewn seams.
• Poor bulk bag construction.  In a situation where inflation and dust collection systems are operating properly, the cause of the sifting may be that the bulk bag is constructed with ineffective seam treatments that are designed to prevent sifting.

In this case the customer was interested in acquiring an 'area' type dust collection system to extract the product from around the top of the bulk bag.  In other words, they were looking at dealing with the symptom of the problem and not its root cause.

The solution they were contemplating is, in my experience, almost always ineffective.  Trying to blanket a relatively large area with a negative pressure source in hopes of vacuuming all of the fugitive dust particles either requires an enormous amount of air flow or simply does a poor job.  Further, any hope of reintroducing the collected product particles back into the packaging system so that it is not wasted is crushed because of the potential for sucking up contaminants along with the dust.

So, the proper process to deal with a situation like this is to carefully troubleshoot the system to determine the root cause.