Jupiter, FL (PRWEB) February 15, 2008
Within the context of industrial dust explosions there has always been an appreciation for the hazard posed by fugitive dust. That can be defined as dust that escapes from process equipment and accumulates in layers on the floor or other horizontal surfaces and worst of all up in the rafters. The insurance industry reports the largest losses in dust explosion accidents often come from secondary explosions fueled by layers of fugitive dust.
To CV Technology, an International leader in dust explosion prevention and mitigation, this on-going problem is well understood and nothing new. However a new OSHA mandate has given the topic of combating fugitive dust a new challenge. What is new is that the amount of dust that can pose a hazard is much less than was appreciated until very recently.
According to the OSHA Directive on Combustible Dust promulgated in October, 2007, the maximum allowable dust layer is only 1/32nd of an inch. That is so little dust that it is debatable that it can be accurately measured. Upon learning of so strict a requirement it is not uncommon for industrialists to simply throw their hands up in despair.
At a recent meeting of task force members from the NFPA 654 Technical Committee as well as interested parties from related ASTM Committees, the dilemma was framed by a visiting executive from a major American manufacturing company. He reported that in one 100' x 300' high bay facility, his company has been using dedicated cleaning crews equipped with special platforms and rigging to safely clean the roof truss system where dust collects at the rate of approximately 1/16th of an inch per six months. This amount of dust is the suggested limit in NFPA 654. The cost for this twice yearly effort is $500,000.00 per cleaning, or $1,000,000.00 per annum. This company is now faced with doubling that expenditure unless other measures can be found to reduce the dust loading on the facility.
Why is such a small amount of dust considered dangerous? At that same meeting it was reported that testing a layer of dust 1/32nd of an inch deep, covering only a small fraction of the total horizontal area, roughly equivalent to the surface area of support trusses and beams in a typical general occupancy commercial building, upon being lifted into a dust cloud, proved more than sufficient to destroy said building after ignition. Thus, the small amount of dust necessary to pose a significant hazard, placed in counter-point to the high cost for clean up, clearly defines the dilemma faced by industry.
Bill Stevenson Vice President of engineering for CV Technology states, "The options for dealing with this dilemma are still not clear and there is much thought and discussion being expended to find remediation." Stevenson continues, "In the meantime even though it is doubtful if housekeeping is enough, it is a start. A common question we get is 'Is it safe to use compressed air blow down? '" To address this CV Technology offers the following set of guidelines.
Housekeeping using blow down:
This method should be used in circumstances where the use of a vacuum system has proven to be either impractical or ineffective. It is better to use vacuum systems of course, but blow down should not be ruled out as it is far better to blow down than to allow dust accumulations to exceed safe levels. Generally follow these guidelines when blow down is necessary:
1. Clean frequently enough to avoid hazardous dust accumulations. The latest OSHA Directive mandates 1/32nd of an inch.
2. Limit the blow down to one small area at a time using both low volume and low air pressure to avoid dangerous dust concentrations.
3. Shutdown any electrical equipment not suitable for Class II, Division 2 hazardous locations.
4. Prohibit hot work, open flames, or hot surfaces in the area where blow down is to be used.
5. Assign responsibility to work crews for specific areas or systems who are capable not only of performing the cleaning task, but are qualified to identify dust leaks.
Pay particular attention to areas above floor level such as the tops of equipment, roof trusses and so forth. Accumulations in these high spots should be considered more dangerous because they are harder to reach, harder to clean, and if disturbed become suspended over a longer duration and range.
If an HVAC system is used to remove dust during blow down, inspect the ducting and any plenums carefully to make sure there is no accumulation of dust in them. If there is any accumulation, this dust must be cleaned out. Consider increasing air velocities in HVAC ducting to prevent further accumulations inside these systems.
In addition to housekeeping it is very important to find ways and means to reduce dust emissions in facilities handling combustible dusts and powders. The elimination of leaks should be given high priority. Aspiration systems need focus. Are they adequate or can they be improved? Are there better ways to handle powders without creating fugitive dust? These and other questions need answers and since every situation is different these answers should be derived from a qualified risk analysis.
Stevenson concludes with a practical example: "Anyone who has ever baked a cake or a loaf of bread can attest that simply transferring 3 cups of flour from the canister to the mixer bowl results in a layer of dust on the kitchen counter. If that simple task results in fugitive dust, how much more difficult will it prove for industry to meet this new challenge? This is going to be a very tough nut to crack and it will require innovation, effort, and flexibility to effectively address it."
CV Technology provides strategic consulting to examine the needs of each client and assess the risk of dust explosion. In addition, CV Technology manufactures products that are designed to prevent or mitigate dust explosions. Isolation Valves, Rupture Discs and Panels, and Flameless Vents are custom tailored to minimize (and in some cases prevent) any damage or other interruptions to the process if an explosion were to happen. More information and detail is available on the corporate website: http://www.cvtechnology.com
CV Technology, Inc
15852 Mercantile Court
Jupiter, FL 33478
Phone (561) 694-9588