I knew going into the project that there were more than a few rules and regs out there stipulating requirements for big DC installs, but I wasn’t very far into the process before I started getting conflicting information from people who I thought should know the right answer.
Finally, a Fire Protection Engineer made the comment to me that “when it comes to dust collection, people use fear to sell all kinds of stuff”....
Ahhhh… now things started to make more sense. So we popped the $50 charge and bought a copy of NFPA 664, Standard for the Prevention of Fires and Explosions in Wood Processing and Woodworking Facilities. Only 78 pages of “light” reading and I was getting the answer straight from the horses mouth. (but just how many horses are out there telling us what to do?).
The magic number is 5,000 cfm! If your system is >5,000 cfm you must:
1. Install the collector outside.
2. Install a spark detection and fire suppression system (SDFS) in your ductwork.
3. No duct runs can tap into the header downstream of the SDFS system.
Fortunately, we bit the bullet and purchased a GreCon system ($20K for a second hand system and installation) about 6 years ago, and our tech. rep. tells us that the sensors will function properly in the larger headers and that even though we have an older control panel (which he recommends upgrading, of course) it is good to go, with room to grow. Here’s a schematic of how they work…
One zone monitors the suction header and will use water from our sprinkler system to spray inside the header to prevent a fire in the DC itself, while another zone monitors the return air and will shut the abort gate, preventing a fire in the DC from blowing back into the building. The abort gate also closes mechanically if there is the type of rapid pressure rise associated with an explosion in the DC. Timing is the key, and with our air stream volume designed for 4,500 ft/sec we need 20 ft. between the sensor and the spray, in order to activate the spray in time.
Here’s a page from one of the presentations I gave our to the owners and affected dept. heads summarizing the rest of the NFPA requirements that affect our operation.
I’m getting tired…. class dismissed :^)
-- Pine is fine, but Oak's no joke!