Page 266 - Valve Selection Handbook

Rupture Discs 253

Figure 6-35. Explosion Vent Panel of
Composite Construction Before and After
Bursting. (Courtesy of Continental Disc
Corporation.)

Figure 6-36. Comparative Graph of
Vented and Unvented Explosion.
{Courtesy ofFike Metal Products.)

sure, P uU is the ultimate sustainable pressure of the enclosure, and P max is
the pressure level of an unvented explosion.

Explosion vent panels in combination with flame-quenching vent
system. When a dust deflagration occurs in a plant item, there is far
more dust present than there is oxidant to burn the dust completely.
When venting takes place, large amounts of unburned dust mixes with
additional air from the surrounding atmosphere. In one deflagration vent-
ing test, a fire ball extended at least 4m below the level of the vent and
about 15m horizontally. Personnel enveloped by such a fireball might not
survive 1 (See Figure 6-37 for a random dust explosion test). The protect-
ed plant item must therefore be positioned in a manner that protects the
personnel and prevents secondary explosions.

1
NFPA68 (1988), Guide for Venting of Deflagrations (7-7, Flame Clouds from
Deflagrations)