Mobile Offshore Drilling Rig (MODU) are dirty and noisy places to work. One of the worst places is below decks where the drilling mud is mixed. This is because dust in the sack cutting operations makes it hard to see and breath.
THE PROBLEM
The sack cutting operation is typically done within an enclosed, below deck space that is either in or adjacent to the sack storage area. During certain points of operation, the process may require manual filling where a man stands at a waist high cutting table, runs a sack full of dry powder over a cutting knife, and then physically empties the sack contents into an opening at the back of the cutting table that dumps the dry power into the hoppers.
During manual filling, the process produces a lot of dust in the work area. Not only is this dust a nuisance from a maintenance and cleanliness point of view, it is also an environmental health issue for the people who work in this area. 
Sometimes the dust produced from this operation gets so bad that personal respirators are issued to prevent workers from breathing in and ingesting this light but irritating airborne powder. While a respirator is a solution to the human health problem, they are hot and bulky and not very conducive to carrying out this heavy and time-consuming labor. Plus, the dust contamination in the immediate workspace can potentially migrate into other machinery spaces, causing similar hazards in these areas. A more precise and efficient solution is required to mitigate all these problems.
From Eldridge’s experience, the best method for controlling dust contamination within a sack cutting machinery space is containment and collection.
SOLUTION: CONTAINMENT & COLLECTION
Containment starts at the sack cutting table with a containment hood. A properly engineered and designed hood with three enclosed sides and one open side works best. The open side must be sized with an appropriate capture rate for the dust particles. Then we size the ducting for a minimum of 3,500 fpm conveying velocity.
The containment hood prevents the dust from coming back toward the worker as well as from spreading within the machinery space. Clean air is drawn over the worker and into the containment hood and all the dust generated from the sack cutting process is pulled into the extraction system.
Collection is what to do with the dust as it is contained. A compact, pleated filter cartridge style dust collector works best for this job. It is small enough to fit into the confined deck-to-overhead space but large enough to handle the collection of dust from multiple sack cutting tables operating simultaneously.
The pleated cartridges are self-cleaning using a compressed air reverse pulse, which allows for extended filter life. The dust residue is collected into a collection tray or barrel drum, which allows for easy disposal and/or recycling of the collected and concentrated particles.
An axial flow or centrifugal fan is sized to draw air from the machinery workspace through the containment/collection system. The fan is located on the clean air side of the collector and thus eliminates the build-up of dust and maintenance problems. Locating the fan on the discharge of the collector also allows the clean filtered air to be recirculated back into the sack cutting room.
There is no “cookie cutter” or “one-size-fits-all” system; each sack cutting operation is set up differently and involves its own set of challenges for containing and collecting the dust.
Eldridge has been engineering and providing sack cutting dust collection systems to the MODU industry for over 50 years. While you may be dealing with this problem, please be assured that the solution is no more than a phone call or email away. The overall cost of a properly engineered and installed system is much less than the long-term health issue liabilities.
If your rig is experiencing issues with dust in sack cutting operations, Eldridge is available to specifically provide you with a solution guaranteed to eliminate such issues.