Explosion relief on the roof is necessary when exterior wall space/area is (a) insufficient [internal rooms], (b) where external walls are obstructed either from inside or the outside of the room (c) facing a public area and (d) proximity to roads, parking lots, property lines or other on site facilities preventing use of wall mounted explosion relief panels. Haz-safe Building’s Roof Relief Polygonal Housing have the following advantages:
(1) The housing can be oriented on the roof so that when there is an explosion the blast effects are thrown up and out in a direction away from other objects on the roof like HVAC equipment, air intake and exhaust systems, louvers, skylights, upper level walls with windows and doors, etc.
(2) Polygonal Housings are constructed with continuously welded tubular steel frames and clad with 10 gauge steel plate providing 216 lbs.sq.ft. blast rating (higher strengths available). This is the same minimum construction as seen on the Blast Resistance Ratings page on this web site.
(3) Sandwiched between the steel plate is R-8.7 insulation.
(4) Installed on the vertical face of the housing is an all aluminum bottom hinged, R-9 insulated explosion relief panel with a single adjustable release setting and resettable magnetic release (for more information click to its own attached Haz-Safe Explosion Relief Panel’s webpage).
(5) All metal non-combustible construction of the Roof relief Polygonal Housing is superior to those constructed of plastics, polymers, etc. combustible materials.
(6) Multiple Polygonal housings can be ganged together forming an assembly of Roof Polygonal Housings.
(7) Standard with crane lifting lugs. Options include galvanized steel construction, heat tape to prevent explosion relief from being frozen shut, snow hoods, custom paint colors and base height extensions.
(8) Special separated base with rebar for concrete building manufacturer’s roof applications. Base is shipped ahead so any concrete building manufacture can pour the concrete around the Roof Relief Polygonal Housing’s base making it an integral part of their concrete roof.
What not to do…
Situation #1: The caption under this photo said, “Roof-mounted explosion relief – FM Standard 1-44 and NFPA 68”. But BOCA paragraph 4220.127.116.11-7. Says, “Reliving devices shall be so located that the discharge shall not be less than 10 feet vertically and 20 feet horizontally from window openings or exits in the same or adjoining buildings or structures.” Then NFPA 68 paragraph 5.6.4 that says, “…A major blast pressure can be caused by the ignition of unburned gases or dust outside the enclosure.” This is referring to a secondary explosion occurring on the roof which could occur after the original explosion blows out the above relief roof vents. Haz-safe’s Roof Relief Polygonal Housings can directed all blast effects harmlessly away.
Example of what not to do…
Situation #2: Original captions said “… Four 8’ x 8’ roof mounted explosion relief panels…” (Two panels can be spotted in the front corners of the roof). NFPA 68 paragraph 5.6.7 warns, “Interconnections between separate pieces of equipment present a special problem…” Meaning blast effects can get onto and burst the ducts (unless roof penetrations are protected with blast valves). NFPA 68 paragraph says, “A major blast pressure can be caused by the ignition of unburned gases outside the enclosure.” Meaning a secondary explosion could happen on the roof amongst all the congested equipment. Haz-safe’s Roof Relief Polygonal Housings can directed all blast effects away from congested equipment on roofs.
Roof Explosion Relief Polygonal Housings shall:
Prevent un-burnt combustion products (left over from the initial explosion) from collecting on the roof by installing Roof Explosion Relief Polygonal Housings near the roof edge and reduce the possibility of secondary explosion rolling across the roof.
Multi-directional used to direct blast effects away from other objects on the roof.
Make up for walls not having enough space for wall explosion relief panels.
Put all the relief on the roof with multiple Polygonal Housings.