HomeMy WebLinkAboutLETTER-DUST HAZARD ANALYSISDUST HAZARD ANAYLSIS REVIEW SUMMARY
11/14/2016
We recently received the results of the dust test of Ventilation Solutions fiberglass dust performed by
Exponent. Please find the attached testing results for MEC, Pmax, and MIE.
The other results are very similar to the initial results of the original dust test. While this dust can bean
explosion hazard if it is under specific conditions only, these conditions are addressed in the test results.
The dust control booth is designed as a dilution system. The booth region where grinding and trim
operations are producing material concentrations suspended in the air does not impose a deflagration
hazard as part of the booth ventilation design. [8.2.5]
1. There is no potential ignition source in the booth.
2. The booth has a bonding and grounding system.
3. The MEC of the dust will not be met if proper housekeeping procedures are followed in
accordance with NFPA 652 Sec. 8.4. This includes vacuum cleaning [8.4.2.2] and compressed air
blow down methods of cleaning. [8.4.2.6] The Facility must establish and maintain housekeeping
procedures where the fugitive emissions do not approach the MEC and the housekeeping
schedule does not allow settled dust accumulations to exceed the threshold housekeeping dust
accumulation limits.
Per NFPA 652 Sec A.5.2—A Dust Explosion requires the following five conditions:
1. A combustible dust sufficiently small enough to burn rapidly and propagate flame.
2. A suspended cloud at a concentration greater than the minimum explosion concentration.
3. Confinement of the dust cloud by an enclosure or partial enclosure.
4. The atmosphere to support combustion.
5. An ignition source of adequate energy or temperature to ignite the dust cloud.
According to the test results from the second test with the lower Kst, the MEC of the sample was
55g/m3. So if you take the dimension of the filter areas of each booth the calculations would be as
follows:
Deck Booth:
Filter Area -
3'4"x10Hx65'8"=2,188.68 ft3=61.97 m3
According to test results the Minimum Explosive Concentration is 55g/m3 so to reach that concentration
in the filter area we would need to be
55 g/m3 x 61.97 m3= 3,408.35g of dust required to meet Minimum Explosive Concentration.
3,408.35 g = 7.514 Ibs of dust that would need to be suspended in cloud form to be ignited by the 2.5 W
ignition sources or a 450" C temperature that were used in the laboratory test.
Hull Booth:
Filter Area -
2'8"x12'Hx65'8"=2,103.97ft3=59.58m3
According to test results the Minimum Explosive Concentration is 55g/m3 so to reach that concentration
in the filter area we would need to be
55 g/max 59.58 m3= 3,276.9 g of dust required to meet Minimum Explosive Concentration.
3,276.9 g = 7.22 Ibs of dust that would need to be suspended in cloud form to be ignited by the 2.5 W
ignition sources or a 450" C temperature that were used in the laboratory test.
These concentrations will be impossible to reach under proper operation and housekeeping of the
booth. Scheduled Housekeeping effectively with auditing and documentation in accordance with
frequency and accumulation goals established in [8.4.6.1].
NFPA promotes awareness of the three following fundamental principles:
1. Controlling the fuel (Dust is diluted and kept below MEC)
2. Controlling the ignition sources (None Present) [8.5]
3. Limiting the spread of any combustion event. (Booth contains dust from migrating into
other areas of the plant.)
This means ensuring that you are reducing the number of factors from the dust explosion pentagon and
installing the proper equipment to reduce the effects of an explosion, if one should happen.
Attached:
NFPA 652
Dust explosion pentagon
Exponent Test Results