Wilhelm Jost Institut Förderverein e.V.

Safety Technical Indices

General 

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.

Smoldering Point

Definition:

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.

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Maximum explosion pressure and maximum rate of pressure rise

Definition:

 

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.

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Lower and Upper Dust Explosion Limit

Definition:

Dust Explosion Limits describe the range of concentration of airborne dust in which explosions are possible.

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Limiting Oxygen Concentration

Definition:

 

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.

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Minimunm Ignition Energy (MIE)

Definition:

 

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.

 

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Conductivity

Definition:

 

The electrical conductivity is a measure for the electrostatic rechargeableness of dusts and is usually indicated in the unit pS/m.

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