Explosion Hazard
Several different gases are used for heating in one form or another.
Examples of common flammable gases are
natural gas (methane), LPG, propane and hydrogen.
All these gases have unique flammable gas /
air mixtures.
Gas monitoring is intended to warn of
unwanted and uncontrolled emissions of these gases, which
may lead to explosion hazards.
When monitoring explosion risks concentration
is entirely on the lower limit of the flammable region.
This lower limit is referred to as follows in
different languages:
-
Swedish: UB (undre brännbarhetsgränsen)
-
English: LEL ( Lower Explosive Limit)
-
German: UEG (Untere Explosive Grenze)
In order to obtain a safety margin Sweden has
determined that a gas/air concentration exceeding 25% of the UB
value should be considered dangerous.
Consider 20% of UB as appropriate alarm
point level for explosive gases.
Methane (natural gas) for example, will burn
in gas / air mixtures between 5.0 - 14.0
volume%.
|
Lower flammability limit and
appropriate alert levels for a few gases.
|
|
Gas |
LEL |
Suitable alarm level |
|
Methan |
5,0% |
1,0% (= 10.500ppm) |
|
Propane |
2,1% |
0,4% (= 4000ppm) |
|
Hydrogen Gas |
4,0% |
0,8% ( = 8000ppm) |
You can of course set other alarm levels.
Normally two alarm levels are used, one of
which is activated at 5 or 10% of LEL and the other closer to the
LEL level (emergency alarm).
The important thing is that the alarm points
are always activated before LEL is reached.
Continuous measurement of produced gas.
Through continuous monitoring, even in sample form, we can measure
that the produced gas is kept within the limits that are set.
The need may be, for example, to control
hydrogen sulfide in natural gas or methane content in the production
of bio- or sewage gases.
Avoiding unnecessarily long production
cuts
Early leakage warning is a prerequisite for
good preventive maintenance.
Early leakage detection means that repairs
can be scheduled and not as an unpleasant surprise with production
losses and even loss of sales.
