Safety Technical Indices
In the context of this purely informal overview a set of safety-relevant characteristics are to be introduced which should be known for the characterisation of inflammable solids and dusts in respect of the safety-relevant interpretation of plants.
It pertains to this:
- Burning behaviour (Combustibility Indey, Burn-up Rate, Smoldering Point,......),
- Autoignition (Warm storage, Glow temperature,......),
- Explosion Limits (Explosibility, LEL und UEL),
- Electostatic Technical Indices (Resistance, Conductivity......),
- Minimum Ignition Energy (MIE),
- Minimum Ignition Temperature,
- Maximum Explosion Pressure (Pmax)
- Maximum rate of Pressure rise (KSt).
- Limiting Oxygen Concentration.
- In detail the characteristics are defined briefly, the appropriate testing methods are presented and a description of the safety-relevant meaning of characteristic numbers are given.
The smoldering point is the lowest temperature, at which a solid substance delivers carbonization gases, so that developing carbonization gas/air mixtures can be inflamed by spark ignition.
Maximum explosion pressure and maximum rate of pressure rise
The explosion overpressure pm and the rate of pressure rise dp/dt describe the violence of reaction of dust/air mixtures of random concentration after ignition in a closed vessel. The maximum explosion pressure pmax and the maximum rate of pressure rise (dp/dt)max of combustible dusts are determined in closed standard equipment by means of tests over a wide range of concentration.
Lower and Upper Dust Explosion Limit
Dust Explosion Limits describe the range of concentration of airborne dust in which explosions are possible.
Limiting Oxygen Concentration
The limiting oxygen concentration is the maximum oxygen concentration in a mixture of an inflammable material with air and inert gas which does not explode in combination with arbitrary fuel concentrations. The limiting oxygen concentration is determinded under fixed test conditions.
Minimunm Ignition Energy (MIE)
The minimum ignition energy (MZE) is the smallest electrical power stored in a condenser, which sufficiently ignites an ignitable mixture of a combustible atmosphere by an electrical discharge. The MIE is determined under prescribed test conditions.
The electrical conductivity is a measure for the electrostatic rechargeableness of dusts and is usually indicated in the unit pS/m.