Wet Sprinklers in Woodworking Dust Collection?

9/13/2021

Are wet sprinklers required in a woodworking dust collection system with a spark detection and arrest?

Are there any limitations or hazards to installing wet heads in this system such as heads struck by small debris?

Do dust collection system fall under industrial exhaust?

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6 Comments

Jesse

9/13/2021 08:16:21 am

NFPA 654 is the governing standard here.

There are numerous water-based approaches, but we're not looking at a 13 type system here. There are several pre-engineered products on the market. Typically these are more mister type spray devices actuated by an interlocked optical sensor. There will also be a requirement for protecting the baghouse or cyclone, and this could be an NFPA 13 application.

jesse

9/13/2021 08:19:37 am

Sorry, hit SUBMIT too fast.

The optical sensors are downstream of the last material entry point. They "see" the explosion originating and the spray nozzles activate in mili-seconds. A standard 13 design would not be able react in time and the resultant explosive energy would likely destroy the duct and the sprinkler systems anyway.

Evan

9/13/2021 08:37:54 am

Hi Jesse,

What you are describing is an explosion suppression system that is used when traditional explosion prevention measures cannot be utilized (such as pressure venting). If the performance objective of the system is based around the extinguishment of a fire (not the suppression of a deflagration) then the discussion opens up about using standards sprinklers inside the unit and duct work. Most of the commercially available pre-engineered suppression systems marketed for dust collectors are designed for this purpose as well (fire extinguishment, not explosion suppression). There are very few suppression systems that are engineered for explosion prevention. Outside of a high speed water spray system that you brought up, Fike and IEP Technologies are the two big players for engineered explosion suppression systems.

Alex

9/13/2021 09:05:14 am

Hi Anonymous,

This question is beyond me. I look forward to reading others replies and learning myself.

While digging into the question this morning, I did come across a past Meyer question from this January. Franck outlined a lot of applicable codes.

Link: https://www.meyerfire.com/daily/sprinkler-required-in-dust-collection-ductwork

Best of luck with your design!
Alex

Franck

9/13/2021 11:31:04 am

At that time, we were speaking of metal dust. But except the fact some metals are pyrophoric (and might react violently with water), wood dust has the same behavior as any combustible / explosive dust.

Yes, you can provide a quick deluge spray system to « kill » the amber and limit an explosion / fire as indicated by Jesse, but you can also have a more traditional sprinkler system inside the duct (where dust may accumulate over the time and create a flash fire hazard) and particularly inside the dust collection system (silo/cyclone) as indicated by Evan.

I have seen some of these systems in paper mills where they were collecting paper dust.
Most of them were automatic, some manually activated.
One possible issue with the silo : vibrations, that may create issues for the sprinkler supports.
Sometimes, approved flexible connections are used between the part attached to the silo and the sprinkler pipes attached to the building structure.

Paper bags are necessary for sprinklers in ducts / silo to avoid accumulation. This also means that access need to be provided for regular maintenance (change bags, check sprinkler condition…)

Don

9/13/2021 10:29:12 am

Many questions must be answered before getting to, "Are wet sprinklers required in a woodworking dust collection system with a spark detection and arrest?" Is the collector indoors? Does a deflagration hazard exist? You must start at the Hazmat Table 307.1(1) and see footnote "q." A "report" (Dust Hazard Analysis) is required. The contents of the DHA are listed in NFPA 664-17 Chapter 4. The report will determine if you must treat the area where the collector is located as an "H" occupancy. Chapter 8 of NFPA 664-17 will specify where you can locate the collector (with exceptions) and how to protect ducts with a fire/deflagration hazard. There are more than one design of suppression system. Water is most common but I've seen CO2 as well. They are all tested and listed. I'm in Oregon and in the OSSC-2019 Chapter 919 there is an explosion control chapter that is not included in the IBC-2018. It is worth the read. There is not an easy answer to your question but I hope I've given you a sense of direction.

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