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.
Border Die Gap
The transmission of an explosion of a plant component into another can be prevented, if both are separated by a sufficiently narrow gap.
The flash point is the lowest temperature, at which a liquid delivers an inflammable gas or steam under prescribed test conditions in appropriate quantity that a flame develops immediately at a contact of the vapor phase with an ignition source.
The laminar flame speed is the speed, where fresh gas with flame formations of movements flows under laminar conditions towards the flame front. The flame front of laminar flames on burners is stationary, with turbulent flames, as they occur in most technical burn procedures, the flame front fluctuates around a middle situation. The flame speed of the turbulent flame amounts to a multiple of the speed of the laminar flame.
Explosion Limits - Lower and Upper Explosion Limit
In mixtures of combustible gases or steams with air an independent burn can reproduce itself only within a certain concentration range.
The border concentrations, where a explosion is just no longer possible, are called lower and upper explosion limit.
With a concentration below the lower explosion limit the mixture is too "lean" (it contains too little fuel). With a concentration above the upper explosion limit the mixture is too "fat" (it contains too much fuel, i.e. too little oxygen), in order to continue the burn after ignition.