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In the case of a leak which has not caught fire :
- close the gas inlet
- do not use any flame or electrical device in the area where the
leaking gas could have spread.
In a case of asphyxia :
- take the victim out into the open air
- start artificial respiration and call the fire department
a) PROPANE
This is a fuel gas, and mixtures of propane and air and propane and
oxygen are explosive within a range of 2.4 to 9.5 % in air.
There is a risk of explosion in the event of a :
- leak of propane in ambient air
- introduction of propane in an enclosed space filled with air
- entry of air in a propane line
- the mixtures thus formed can be ignited by a spark, a flame or a
cigarette.
Propane is heavier than air. There is thus the risk of an accumulation
in low points.
b) ACETYLENE
Acetylene is a fuel : mixtures of acetylene and air and acetylene and
oxygen are explosive in ranges of 2.3 % to 80 % in air. The most
dangerous are those with a low concentration of acetylene.
Acetylene can be smelled starting with a proportion of one per
thousand in air. If you smell acetylene, ventilate well.
Acetylene reacts with copper and silver to give highly unstable
acetylides. The decomposition of these acetylides can start an
explosive decomposition of acetylene.
- Prohibit lines made of copper, materials with a copper content greater
than 70 % and hard solder with more than 50 % silver.
-MAXIMUM OPERATING PRESSURE = 1.5 bars
It is compulsory not to tighter the hose nozzles and gas connects more than 3 mdaN
DANGER WHEN CUTTING
ALUMINIUM WITH PLASMA
There is a potential risk of explosion
because of an accumulation of hydrogen
under the sheet when cutting aluminium and
its alloys on a water cutting table, even when
cutting under or above the water..
This risk mainly occurs if :
* slags are allowed to accumulate at the bottom of the water tank
* the metal sheet is left on the cutting area overnight or during a week-
end
ent))
In some situations (ex: breakdown), there may be possible residual voltage
of more than 100 V on the torch. Before working on it, make sure that the
generator is switched off
SAFETY
3.3-
ADDITIONAL INSTRUCTIONS FOR SOME GASES
IMPORTANT
CONNECTIONS
(even in case of leakage)
(risk of cracks later
En In the case of a leak which has caught fire:
- close the gas inlet if the valve can be reached
- Use CO² (carbon dioxide snow) extinguishers (5 kg or
more) with nozzles.
- if the leak can not be stopped, let the fire burn while
cooling the cylinders and the surrounding installations.
.
c) OXYGEN
With 23 % oxygen in air (normal concentration 21 %), combustion
becomes brighter and even explosive.
Oxygen enrichment of the air in a room is therefore dangerous.
Most compounds, and especially organic substances, such as oils,
greases, fabrics, paper and plastics catch fire in the presence of
oxygen due to the smallest spark or even an ignited spot.
Fats can even catch fire on simple contact with oxygen.
Consequently, the following precautions are necessary :
BEFORE INSTALLATION, remove all traces of rust and scale in piping.
2 purgings with nitrogen :
1 with great force (10 bars) to detach dust
the other to blow the dust out of lines
Before being fitted to a pipe, any device must be CLEANED and
DEGREASED.
Use fluorated-chlorofluorated lubricants or molybdenum disulfide FREE
OF FATTY SUBSTANCES.
)
The hydrogen is formed in the waste accumulating at the bottom of the
tank. It is released by a chemical reaction between this waste ant the
water. When it rises to the surface in bubbles, the hydrogen is trapped
under the metal sheet placed on the water table and is ignited by the
plasma arc.
PRECAUTIONS :
* most important is to empty the water tank frequently and remove all
waste (especially fine particles) from the bottom ;
* fit ventilators or leave the extractor system switched on to cause the
air to circulate between the water and the top face of the sheet ;
* keep the water at a neutral pH. This should reduce the chemical
reactions between the water and the aluminium ;
* after the installation has been out of use for a time, vibrate the water
table before positioning the first sheet. This should allow the
accumulated hydrogen to release itself and dissipate before trapped by
the sheet
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