I'm working on a spray booth calc that's kicking my backside. Section 22.4.2.1(3) (2016 edition) says sprinklers in stacks or ducts shall flow at least 30 gpm at a minimum pressure of 15 psi. I've got several sprinklers in an exhaust tunnel that are protecting 56 sf. At a .40 density, that works out to be 22.4 gpm @ 7.8 psi (K8.0 sprink). But no, I'm required to bump up the flow/pressure to 30/15 so that I'm really getting a .55 density. This is a change that occurred in the 2007 edition of NFPA 33. I looked at the ROC, but it gave no justification for the change. Anybody know why (or willing to postulate) why this was added? Seems to me the base requirement of Extra Hazard Group II design (a .40 density) should have been sufficient.
Ed Kramer Bamford Fire
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