Explosion Suppression

• NFPA 69

• initially for aircraft fuel tanks (1940’s)

• industrially (1950’s)

• to protect enclosed vessels/containers

• often against dust explosions

Explosion Suppression

Detonations

• fuel that contains own oxidizer

• high explosive

• munitions etc.

• velocity of flame front > speed of sound

• explosion suppression won’t work

Explosion Suppression

Deflagrations

• fuel oxidant mix

• velocity of flame front < speed of sound

• black powder,

• dust explosions

• gas leaks

• suppression is possible

Explosion Suppression

Alternatives or Enhancements

• control oxidant concentration (inert gas)

• control fuel concentration (ventilation)

• stronger containers

• explosion relief venting

• process isolation

Explosion Suppression

How explosion suppression agents work

• agent introduce early

• absorb energy, or

• inhibit chain reactions, or

• dilute reactants

• see fig. 9-1

Explosion Suppression Components

Container

• refillable

• pressurized with N2

• mounted directly on vessel (no piping)

• usually multiple containers

Explosion Suppression Components

Detection system

• Ultra Violet (flame)

• rate of rise pressure

• Products of combustion

• Infra Red (heat)

Explosion Suppression Components

Control panel

• can handle multiple systems

• nothing unusual

Explosion Suppression

Applications

• aerosol fill rooms

• grain handling

• coal handling

• other dusts

Explosion Suppression

Sequence

1. Mixture ignites

2. Pressure rised

3. Detector senses change, notifies panel

4. Panel initiates discharge, closes isolation valves

5. Flame front halted

Explosion Suppression

6. Deflagration extinguished

7. Suppression ceases

8. Agent replaced, system back in service