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 liquids, gases and steams in respect of the safety-relevant interpretation of plants.
It pertains to this:
- Explosion Limits (LEL und UEL),
- Limiting Oxygen Concentration,
- Flame Point, Lower Explosion Point
- Ignition Temperature,
- Minimum Ignition Energy (MIE),
- Flame speed,
- Border Die Gap,
- Maximum Explosion Pressure (Pmax)
- Maximum rate of pressure rise (KG).
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 ignition temperature is the lowest temperature of a hot surface at which the inflammation of an inflammable material as gas/air or steam/air mixture occurs. The ignition tempeature is determined under prescribed test conditions.
Lower Explosion Point (LEP)
The lower point of explosion is the temperature of a combustible liquid where the concentration of saturated steam in air is equal to the lower explosion limit.
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.
Limiting Oxygen Concentration
The limiting oxygen concentration is the maximum oxygen concentration in a mixture of a fuel with air and an inert gas , in which no explosion can occur.
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 liquids and is usually indicated in the unit pS/m.