I have an exhaust system serving a welding and metal fabrication lab at a school. They will utilize 70% ferrous metal and the remaining will be a mixture of stainless steel, coated steel and aluminum.
The largest duct diameter at the building exit is 30" round. The dust collector will be located on the exterior of the building and in a freezing environment. Will I need to provide fire suppression within the ductwork both inside and outside as well as within the dust collector? Sent in anonymously for discussion. Discuss This | Submit Your Question | Subscribe
5 Comments
Mike Ruck
1/29/2021 09:24:36 am
Fire suppression would be located on ductwork inside building.
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Franck
1/29/2021 10:37:48 am
The possible issue is related to pyrophoric metal, such as aluminum, especially when divided in small particulates (dust).
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CJ Bonczyk
1/29/2021 11:34:20 am
I would see if you can get all the cutsheet data and design for the exhaust system & dust collector itself. Many times these have particular standards (NFPA 45, 91, 68, 69, 652 & 654, 484), that are required for the fire protection and safety guidelines. Additionally ensure the materials are not UN Class 4.3 solid as tested using UN Class 4.3 water reactivity test methods. Specific detection i.e. smoke, spark detector, and any heat detectors may be required. Premanufactured nozzle/sprinkler locations may be required on the units/ duct themselves. The detection and system unit design will also help dictate which type of applicable extinguishing agent will be required as well. Make sure the project does not have to comply with FM Global as they have particular data sheet requirements on various dust collection systems. Check the life safety code documents for information regarding the occupancy and additional code requirements. Lastly ensure the local AHJ does not have any additional requirements. We have made the mistake in the of simply complying with code for our submittal and the AHJ required additional protection of the system to assist with their fire fighting operations. An example of this of this is we had to add a preaction system for a single sprinkler for two dust collectors located on the exterior of a building. This was not required by code and the design of the system, however a hydrant was within 50 feet and they did not want to expose the responding team to an exploding dust collection unit.
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Jesse
2/1/2021 07:50:10 am
Great question. You'll need listed detection and protection downstream of the last material entry point for sure, and the comment about pyrophoric metals is very good.
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9/10/2021 01:00:56 pm
If you met NFPA requirements, and designed the internal duct system velocities to keep the particulate in suspension, you will not need any kind of suppression in the duct itself. The concept of applying low speed duct, and applying sprinklers for 'fires' is not only compliant with NFPA.
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