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 PREVENTIO N O F SULPHUR FIRES AN D  EXPLO SIO N S  17

6. DUST EXPLOSION

PREVENTION AND

PROTECTION

6.1 GENERAL

6.1.1 There are tw o basic approaches available for handling com bustible dust

safely:

(a) Explosion Prevention : D ust explosions can be prevented by ensuring

that the follow ing conditions are m et:

• Suspensions of sulphur dust in air are avoided; and

• All sources of ignition are excluded.

(b) Explosion Protecti on : If an explosion is initiated, its harm ful effects can

be avoided by:

• Containm ent of the shock w ave generated in a vessel capable of

w ithstanding the m axim um pressure produced (about 700 kPa for

sulphur) w ithout bursting.

• Venting the vessel using a bursting disc or sim ilar device so that

the pressure rise initiated by the explosion is relieved by the opening

of the vent.

• Suppression of the explosion by detection of the em bryonic

shock w ave, follow ed by the discharge of usually a halon gas w hich

both inerts and suppresses the explosion. Such a system is capable of

being fully activated w ithin 10-30 m illiseconds, w hereas a typical

explosion m ay require 100-200 m illiseconds to develop its full force.

• Plant separation: this relies on physically isolating the hazardous

process from other plant operations by the use of “chokes”or by

distance.

6.1.2 In this code of practice, explosion prevention m ethods are favoured

w herever practical as the prim ary m eans of providing a safe w orking

environm ent.

6.2 MINIMISATION OF DUST

6.2.1 To prevent dust form ation during the storage and handling of sulphur,

enclosures should be constructed w ith a m inim um num ber of horizontal

surfaces w here dust can accum ulate.