EIGA - 04-00 - E - Fire Hazards of Oxygen and Oxygen Enriched Atmospheres
EIGA - 04-00 - E - Fire Hazards of Oxygen and Oxygen Enriched Atmospheres
EIGA - 04-00 - E - Fire Hazards of Oxygen and Oxygen Enriched Atmospheres
OXYGEN ENRICHED
ATMOSPHERES
IGC Doc 04/00/E
FIRE HAZARDS OF
OXYGEN AND
OXYGEN ENRICHED ATMOSPHERES
Prepared by the Safety Advisory Group SAG 1993
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IGC
Doc 04/00/E
Table of Contents
Scope .............................................................................................................................................1
Purpose ..........................................................................................................................................1
Definitions .......................................................................................................................................1
Protection of personnel...................................................................................................................7
8.1
8.2
8.3
8.4
8.5
Measuring Instruments............................................................................................................6
Choice of the measuring method ............................................................................................6
Accuracy..................................................................................................................................6
Utilisation of measuring instruments .......................................................................................7
Clothes ....................................................................................................................................7
Analysis ...................................................................................................................................7
Fire fighting equipment............................................................................................................7
Smoking ..................................................................................................................................7
First Aid ...................................................................................................................................7
Appendix A - References
Appendix B - Summary for operators
Appendix C - Examples of oxygen enrichment accidents
IGC
1
Scope
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personnel to
enrichment.
the
presence
of
oxygen
Purpose
4.3
5.1
General Properties
4.2
n
itio
Ig n
Co
m
Ma busti
ter ble
ial
Oxygen
Oxygen
IGC
f)
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within the visible cloud associated with the
spill. Nevertheless, atmospheric checks
should be carried out to confirm this when
approaching the vicinity of the vapour
cloud.
g) Liquefaction of air.
When using cryogenic gases with boiling
points lower than oxygen, e.g. nitrogen,
hydrogen and helium, oxygen enrichment
can also occur.
Ambient air will condense on uninsulated
equipment where the temperature is lower
than the liquefaction temperature of air
(approx 193 C). This will also occur on
pipework lagged with an open cell insulant.
The liquid air so produced can contain up
to 50 % oxygen and, if this liquid drips off
and evaporates, the oxygen concentration
in the last remaining portion can be over 80
%. Consequently, special precautions shall
be taken with regard to the potential
oxygen enriched insulation and to the
vessel before starting repair work on any
equipment.
h) Oxygen vents.
Particularly hazardous are areas where
oxygen vents are located. A sudden
release of oxygen can occur without
warning. Note that the non-cryogenic
production of oxygen or nitrogen might
involve an occasional or continuous
venting of oxygen.
5.2.2 Improper use of oxygen
Many serious accidents have been caused by
the use of oxygen for applications for which it
was not intended.
Examples of improper use of oxygen are:
a)
b)
c)
d)
e)
IGC
5.2.3 Incorrect operation and maintenance
of oxygen equipment
Incorrect operation and maintenance of oxygen
equipment is one of the most frequent causes
of fires in oxygen systems.
Examples of Incorrect Operation
a) Failing to reset pressure regulators to the
closed position when the oxygen cylinder
valve has been closed. This results in
extremely high oxygen gas velocities when
pressurising the regulator next time it is
used.
b) Rapidly opening valves. This can lead to
ignitions caused by the heat generated by
high velocity gas or adiabatic compression.
Rapid opening of valves can result in
momentarily high oxygen velocities,
sufficient to project any debris being in the
system through the system at sonic
velocity causing frictional heat, sparks, etc.
When the system is dead ended as in
the case with a pressure regulator
connected to an oxygen cylinder high
heat
can
be
generated
through
compression of the oxygen. Both these
phenomena can cause a fire.
c) Opening a valve rapidly against a closed
valve downstream in a system this can
lead to a similar situation as described
above.
d) Start-up of an oxygen compressor
erroneously with oxygen. (This is incorrect
operation only in special cases see
references No. 7 and 8)
Examples of Incorrect maintenance
e) Working on pressurised systems.
f) Venting oxygen into confined spaces.
g) Allowing systems to become contaminated.
Contamination by particulate matter, dust,
sand, oils, greases or general atmospheric
debris creates a potential fire hazard as
highlighted above. Portable equipment is
particularly susceptible to contamination
and precautions shall be taken to prevent
ingress of dirt, oil, etc.
h) Failure to completely remove cleaning
solvents from components which are to be
used in oxygen service. The solvent
residues are not compatible with an oxygen
enriched atmosphere.
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5.2.4 Use of incorrect materials
Design of oxygen equipment is very complex
and the why and how is not always obvious. In
essence nearly all materials are combustible in
oxygen. Safe equipment for oxygen service is
achieved by careful selection of suitable
materials or combination of materials and their
use in a particular manner.
Any modifications to a design must be properly
authorised to prevent incompatible materials
being used.
Substituting materials which look similar is
extremely dangerous and many accidents are
reported where the cause was incompatible
replacement parts. Examples of this practice
could be
a) Replacing o-rings and gaskets with similar
looking items. There are hundreds of
different types of elastomer and most are
not compatible with oxygen.
b) Replacing a metal alloy with a similar type
of alloy. The composition of particular
alloys has a significant effect on its
mechanical
properties
and
oxygen
compatibility. Bronze, which covers a
wide range of alloys, has several varieties
which are compatible with oxygen and
even more which are not; e.g. tin bronze is
used in liquid oxygen pumps while
aluminium
bronze
is
considered
hazardous.
c) Replacing PTFE tape with a similar white
tape. Not all white tape is PTFE and not all
brands of PTFE tape are safe for use in
oxygen.
d) Replacing parts/components with nonapproved equipment is not allowed. The
geometry of certain components is
sometimes
critical
and
approved
manufacturers parts shall always be used
when maintaining oxygen equipment.
e) Replacing or installation of combustible
material in filters e.g. plastics, paper,
adhesives. Filters in oxygen systems are
very sensitive to ignition due to presence of
particles and complicated flow conditions.
Therefore filters must be made of materials
which demand very high ignition energy
e.g. Monel.
f) Lubricants are generally not allowed in
oxygen service except for special
applications. Specialist expert advice shall
always be obtained before applying such
lubricants.
IGC
5.3
Combustible material
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such cases the molten or burned metal residue
is projected away from the equipment and may
be followed by an oxygen release. This in turn
can lead to fierce and rapidly spreading flames
in any adjacent combustible material external
to the equipment. Oil and grease shall never be
used to lubricate equipment that will be in
contact with oxygen.
5.4
Ignition sources
d)
e)
f)
g)
h)
i)
6.1
Information/training
IGC
b) Prevention of hose failures in high
pressure gas systems IGC Doc 42/89
c) Reciprocating compressors for oxygen
service. Code of practice IGC Doc. 10/81
d) Code of practice for the design and
operation of centrifugal liquid oxygen
pumps IGC Doc 11/82
e) Centrifugal compressors for oxygen
service Code of practice IGC Doc. 27/93
f) SAG Info 15/97: Safety principles of high
pressure oxygen systems.
g) Flammability and sensitivity of materials in
oxygen-enriched atmospheres American
Society for Testing & Materials (ASTM)
symposium series
h) Cleaning of equipment for oxygen service.
IGC Doc. 33/97
All maintenance and repair work shall be
performed by experienced and fully trained
personnel.
All persons who work in areas where oxygen
enrichment can occur shall be given adequate
instructions as to the risks involved. Special
attention shall be drawn to the insidious nature
of the risks due to the rapidity of their effects.
Practical training shall be given in the means
by which such risks can be minimised,
stressing the importance of identifying sources
of oxygen enrichment and their isolation.
6.2
Proper design
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6.3
IGC
need to be documented in the Hazardous
Work Permit. Reliance on the closure of valves
to prevent oxygen enrichment is not sufficient.
Permission to enter such a space subsequent
to completing the steps indicated above shall
be given only after the issue of an entry permit
certificate signed by a responsible person. An
analysis of the vessel atmosphere shall always
be requested as part of the work permit
requirements.
6.3.5 Isolation equipment
When an oxygen pipeline enters a building, an
isolation valve shall be provided outside the
building in an accessible position for operation.
This valve and location shall be clearly marked
and identified. The purpose is to be able to
operate the valve in a safe location in the event
of an oxygen release in the building.
Disused oxygen lines should be dismantled or
completely severed and blanked off from the
supply system.
6.4
Oxygen cleanliness
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isolation and purging procedures prior to entry
into the area, and periodically during the course
of the working to confirm that changes have
not occurred.
A possible method of oxygen detection could
be odorisation. The odorisation is occasionally
used in ship yards, because there is a certain
risk of oxygen enrichment while welding in
small ship rooms. (For details see Ref.2).
However, odorisation must only be viewed as a
possible supplement to effective risk analysis,
isolation, and atmospheric monitoring, and not
as an alternative to them.
7.1
Measuring Instruments
Accuracy
IGC
7.4
Protection of personnel
8.1
Clothes
Many
so-called
non-flammable
textile
materials will burn fiercely in oxygen enriched
air.
Some synthetic materials can be fire-resistant
to some extent, but can still melt and cause
serious burns due to the adhesion of molten
material to the skin. Synthetic materials are not
recommended.
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permissible only if the oxygen concentration is
equal to that of normal air. All other
concentrations, that is 23 % or more, are
potentially dangerous. However, as a warning
against local or temporary variation in
concentration, it is recommended that anyone
entering such a space should be issued with a
personal
continuous
automatic
oxygen
analyser which sounds an audible alarm when
the oxygen concentration in the atmosphere
varies above 22.5% or below 19.5%.
8.3
The only effective way of dealing with oxygenfeed fires is to isolate the supply of oxygen.
Under oxygen rich conditions, fire fighting
media could be water, dry chemical (powder)
or carbon dioxide. The choice between these
media needs to take into account the nature of
the fire, e. g. electrical, etc. Burning clothing for
example shall be extinguished by water as
covering in a fire blanket will still allow oxygen
enriched clothing to burn.
Fire fighting equipment should be properly
maintained and operating personnel should
know where it is located, how to operate it, and
which equipment to use for which type of fire.
8.4
Analysis
Smoking
First Aid
Summary of recommendations
IGC
b)
c)
d)
e)
f)
g)
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h) Smoking shall be strictly forbidden where
there is any possible risk of oxygen
enrichment.
i) People catching fire in enriched oxygen
atmospheres cannot be rescued by a
person entering the area to pull them out,
as the rescuer will almost certainly also
catch fire.
j) People who have been exposed to oxygen
enriched atmospheres shall not be allowed
to approach open flames, burning
cigarettes, etc., until after adequate
ventilation of their clothing.
k) Make sure that all oxygen apparatus and
equipment is properly identified.
Escape routes must be kept clear at all times.
APPENDIX A
References
[1].
[2].
Odorisation of oxygen
IGC TN 28/80
[3].
[4].
[5].
The probability of fatality in oxygen enriched atmospheres due to spillage of liquid oxygen
BCGA Doc TR2, 1999
[6].
[7].
[8].
A method for estimating the offsite risks from bulk storage of liquefied oxygen
BCGA Report R 1, 1984
EIGA
Properties of oxygen
Oxygen supports combustion
APPENDIX B
colourless, odourless
and tasteless, oxygen
enrichment cannot be
detected by the
normal human
senses.
Because oxygen is
EIGA
Properties of oxygen
Oxygen gives no warning
APPENDIX B
EIGA
Properties of oxygen
Oxygen is heavier than air
APPENDIX B
Oxygen
EIGA
Co
m
Ma bust
t
e
ria ible
l
n
itio
n
Ig
APPENDIX B
EIGA
oxygen systems
Use of materials incompatible with oxygen
service
APPENDIX B
EIGA
Compatibility of materials
APPENDIX B
EIGA
APPENDIX B
EIGA
APPENDIX B
EIGA
APPENDIX B
EIGA
APPENDIX B
EIGA
APPENDIX B
EIGA
APPENDIX B
APPENDIX C
8. A contractor employee had to grind away a piece of railing on a platform at the air separation
column.
A Work Permit had been issued and a pre-job discussion had been held. The ambient
temperatures were low and while waiting for a colleague he leaned over and partially sat down on
an oxygen vent warming himself on the escaping relatively warm oxygen leaking through the
valve.
The moment he started grinding, a spark set his oxygen saturated clothing alight, causing burns
nd
rd
on his total body of 2 and 3 degree resulting in months of hospital treatment.
9. When using an oxygen lance in a steel foundry, an operator realised that the coupling between
hose and lance was leaking, but did not mind because it provided some cooling on his stomach. A
spark of hot metal was projected towards the operator and ignited the oxygen saturated clothing
at his stomach, resulting in serious burns.
10. An air powered rotary drill was connected by means of an adapter to an oxygen line. After several
hours, the air in the working compartment had become so enriched with oxygen that when one
of the workers lit a cigarette it flared up, ignited clothing, resulting in four fatalities and five other
men being injured
11. A welder was working in a tank car. After a while, he interrupted his work in order to renew the air
in the tank by introducing oxygen. When he resumed his welding a spark ignited his clothing.
The worker succumbed to fatal burns.
APPENDIX C
12. A steelworker attempted to repair his car which had a blockage in the fuel line. He used oxygen
to clear the blockage and the fuel tank exploded killing one person.
13. There are several reports of men being set on fire due to walking into the gas cloud from an
oxygen spillage while smoking.
14. A person who was wearing proper clothing was working in an oxygen enriched atmosphere. He
went to a smoking area and immediately lit a cigarette, whereupon his clothing ignited.
15. Several incidents are reported of hospital patients who had their clothing and bedding set on fire
due to smoking or sparks while receiving oxygen treatment.
16. Several instances have been reported of deaths in hyperbaric chambers due to smoking or
electrostatic sparking under enriched oxygen conditions. In one case 10 people were killed
when a fire broke out caused by a portable hand warmer being used.