When to Use Explosion Suppression
The following list consists of SOME examples where explosion venting may be impractical and explosion suppression would be the preferred solution.
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| THE EQUIPMENT IS LOCATED INDOORS |
Vent ducts should be used if equipment is located
indoors (NFPA 68-2007, Section 4.8), which results in much higher Pred
values and/or additional vent area (NFPA 68-2007, Sections 7.4, 8.5)(VDI 3673, Section 10). |
| THE EXPLOSIVE MATERIAL HAS A HIGH Kst OR IS A HYBRID |
As the Kst
value increases, the explosion vent area increases, and the cost increases. The cost of
explosion suppression systems is not effected by the Kst value. |
| THERE IS NOT ENOUGH AVAILABLE AREA ON THE VESSEL FOR VENTS |
Somewhat related to the point immediately above, when factors such as Kst
require large vent areas or there physically just is not enough space on the vessel,
explosion suppression systems require minimal interface area (4" and 2" connections). |
| MATERIAL IS TOXIC AND CAN'T BE DISCHARGED TO THE ATMOSPHERE |
The EPA will continue to restrict emissions of toxic materials. Indications in the European community are that there will eventually be no emissions allowed. |
| THERE IS NO SAFE PLACE IN WHICH TO VENT |
NFPA 68-2007, Sections 7.6.4 and 8.8 lists equations to estimate flame distance from
explosion vents. For example: a 10 m3 vessel with one vent, could have a flame travel 56 feet (17 m) out of the explosion vent. |
| FLAME PROPAGATION THROUGH INTERCONNECTIONS |
NFPA 69-2007, Section 1.3.1.3 states the need for for prevention or control equipment to
prevent propagation of the deflagration from one piece of equipment through
the interconnection to other equipment. The cost of explosion vents
and explosion isolation (valves) may be higher than an explosion
suppression system, which utilizes chemical isolation as standard design. |
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