Rack Storage Flue Space and Beam Length
Checks the transverse gaps a bay actually provides, the beam length the nominal flue requires.
Example
You enter
- Pallet width across the bay (in) 48
- Load depth into the rack (in) 48
- Pallets per bay 2
- Transverse gaps in the bay (the two end gaps are half-flues at the uprights) 3
- Nominal flue width (in) 6
- Beam length as built (in) 108
- Rack frame depth (in) 42
- Back-to-back frame spacing (in) 12
- Deeper load being considered (in) 52
You get
- Transverse gap each bay provides 6.0 in across 3 gaps -- meets nominal
- Beam length the flue requires 108 in, 0 in within what is built
- Beam shortfall (in) 0
- Overhang at each face 3.0 in
- Longitudinal flue 6.0 in -- meets nominal
- With the deeper load 2.0 in at 5.0 in overhang -- 33% of nominal
- Deeper load flue share (%) 33.3333
Checked against published worked examples from: Apex Warehouse Systems.
Details, formula, and sources
ScopeChecks the transverse gaps a bay actually provides, the beam length the nominal flue requires, and the longitudinal flue left after pallet overhang. The end gaps are half-flues that pair with the next bay's at each upright, so two 48 in pallets need a 108 in beam, not 114; a deeper load closes the back-to-back flue to a third. NFPA 13 as adopted governs.
Formula or tableRequired beam length = pallets x pallet width + (transverse gaps - 1) x nominal flue, the two end gaps being half-flues that pair at the uprights (Apex: 6 in between loads, 3 in at each end); longitudinal flue = back-to-back spacing - 2 x overhang, with overhang = (load depth - frame depth) / 2.
Source and editionNFPA 13 Standard for the Installation of Sprinkler Systems as adopted, with the commodity classification, storage height, and arrangement.
Free accessNFPA publishes its standards for free read-only online access; the nominal 6 in transverse flue is stated there; a longitudinal flue is required in double-row racks over 25 ft.
What governsEstimate. AHJ and licensed professional govern.
API field namespallet_width_in, pallet_depth_in, pallets_per_bay, transverse_gaps, nominal_flue_in, beam_length_in, frame_depth_in, back_to_back_spacing_in, deeper_load_depth_in, transverse_gap_each_in, required_beam_length_in, beam_shortfall_in, pallet_overhang_in, longitudinal_flue_in, deeper_load_longitudinal_flue_in, deeper_load_flue_share_pct
- Nominal flue 6 in transverse and longitudinal unless the adopted edition and arrangement say otherwiseNFPA 13 as adopted
- In-rack sprinklers required when ceiling protection cannot be shown adequate; that determination is the fire protection engineer's and the AHJ'sNFPA 13 as adopted