2. CONFINED SPACE
Confined space means a space that has
1. Limited openings for entry & exit
2. Unfavourable natural ventilation
3. Not designed for continuous worker occupancy
It includes, but is not limited to ,
Boilers , Pressure vessels, cargo tanks, compressor rooms, void spaces
Ballast tanks, pump rooms etc.
3. General Hazards
Working in confined space has a greater likelihood of causing
1. Serious risk of fire explosion
2. Loss of consciousness from asphyxiation arising from gas, fumes or
lack of oxygen
3. Asphyxiation or suffocation arising from free flowing solids
4. Drowning arising from increase water level
5. Loss of consciousness arising from an increase in body temperature
5. Competent Person
Means a person with sufficient theoretical knowledge & practical
experience to make an informal.
Assessment of the likelihood of a dangerous atmosphere being present or
subsequently arising in the space
Responsible Person
Means a person authorized to permit entry, to a confined space and having
sufficient knowledge of the procedure to be followed
6. Safe entry measures for confined space
A safety meeting should be held prior to the survey to discuss all aspects of
safety measures .
Entry permit should be obtained for the space to be entered.
Identify the hazards & assess the risks
In order to be able to identify the hazards in the space to be surveyed
assess the risks , following information should be available,
1. Latest content of the spaces
2. For gas carriers, a data sheet for the latest cargo should be presented
3. For chemical tankers, a data sheet for the three previous cargoes should be
presented.
Evaluate ventilation of the space.
Evaluate need for isolation of the space
7. Evaluate need for precaution against extreme climatic condition.
Evaluate the lighting arrangement.
Evaluate if special clothing or equipment required.
8. Physical & General hazards
Temperature extremes
Engulfment hazards
Noise
Slick /Wet surface
Falling objects.
9. HAZARDOUS ATMOSPHERE FROM THE
CONTAINMENT IN THE TANK
Inadequate oxygen atmosphere
Inert gas , N2 ( Nitrogen), & exhaust- Inert gas is a non reactive gas used
to prevent possible explosives atmosphere from different cargo
vapour’s.
Pure nitrogen is not poisonous itself , but it cause displacement of the
natural breathing environment.
Toxic atmosphere-toxic substances can come from
1. The product stored in the space
2. The work being performed in a confined space
3. Areas adjacent to the confined space
10. Flammable atmosphere
Two thing make an atmosphere flammable:
1. The oxygen in air
2. A flammable gas , vapour, chemical reaction or dust in a proper mixture.
Different gases have different flammable ranges if a source of ignition, eg:
a sparking or electrical tool, Static electricity, Sand blasting. Is introduced
into space containing a flammable atmosphere, an explosion will result.
An oxygen enriched atmosphere above 22% will cause flammable
materials , such as clothing & hair to burn violently when ignited.
11. Hydrogen sulphide
Is highly toxic & also flammable and is created by decay of organic matter
that is found .H2S is heavier than air has no colour but does have a strong
rotten egg odour . H2S contact can irritate the eyes . Long term exposure to
low levels can cause pain & redness of the eyes with blurred vision.
Breathing can irritate the nose , throat & irritate the lungs higher exposures
can cause a build up of fluid in the lungs( pulmonary odema), a medical
emergency with severe shortness of breath. Very high levels can cause
immediate death.
12. Methane
Methane is an odourless, colourless gas, or liquid under pressure.it is used
as a fuel & in the manufacture of organic chemicals , acetylene, hydrogen
cyanide & hydrogen
Methane is highly flammable gas and dangerous fire & explosion hazard. In
addition to being an explosion hazard very high levels of methane can cause
suffocation, skin contact with methane cause frostbite.
Benzene
Is highly flammable occurs naturally in crude oil. It evaporates easily and
most people can detect its distinctive smell. It can irritate eyes & skin with
drying & scaling of the skin. Exposure can irritate the nose and throat,
headache vomiting. Repeated exposure can cause damage to blood cells.
Convulsions , coma or sudden death from irregular hart beat, may follow
high exposure.
13. Low specific activity
Naturally occurring radioactive materials have been known to be present in
varying concentrations in hydrocarbon reservoirs in a number of areas of the
world. It recognized that these materials can give rise to radioactive scales,
which are usually referred to as low specific activity.
The scales tend to be barium sulphate & strontium sulphate, which
coprecipitate with naturally occurring radium leached out of the reservoir
rock.
Hydrogen emission from anodes and /or accumulators:
Hydrogen gas is produced from an electrolytic reaction from zincous/carbon
& alkaline accumulators. A mix of hydogen gas & oxygen may form a
highly explosive mixture
14. Test for toxic atmosphere
GAS Limit 8 hour work shift
(PPM)
Limit 15 min working
(PPM)
BENZENE (C6H6) 1 5
HYDROGEN SULPHIDE 5 20
CARBON DIOXIDE 5 30
CARBON MONOXIDE 25 50
NITROGEN DIOXIDE 1 3
NITROGEN MONOXIDE 25 50
SULPHUR DIOXIDE 2 5
15. Test for Oxygen
Any atmosphere with less than 20.8%(+/- 0.2%) oxygen by volume should
not be entered.
Health effects from lack of Oxygen is shown below
O2 Level Effects
22% Oxygen enriched atmosphere
20.8% Normal level-Safe for entry
19.5% Oxygen deficient atmosphere
16% Impaired judgment & breathing
14% Rapid fatigue & faulty judgment
11% Difficult breathing & death in a few minutes
16. Test for flammable atmosphere
A space with an atmosphere with more than 1% of the Lower flammable
limit or Lower explosive limit, on a combustible gas inducator should not be
entered
The flammability indicator shows the percent within a safety range of 0-
10% of the lower explosive limit & ideally should read 0%.
Combustible gas detectors have normally two measuring ranges 0-100%
LEL & 0-10% LEL.
Testing Instruments: when dragger tube or equal is used for detecting toxic
gases the sampling gas should have sufficient time to pass through the
sampling hose. If manual hand rubber pump is used , approximately 4
squeezes are needed for each meter of the sampling hose. If battery driven
pumps are used approximately 10 seconds for each neter of sampling hose
should be sufficient
17. Preparation for Confined space entry procedures
Isolate the space
1. Close valves-double block & bleed flange.
2. Empty the space by depressurize, vent & drain.
3. Lockout/Tagout equipment: Electrical sources,
Rotating/Reciprocating parts, Hazardous material
4. Clean residue from the space
18. Ventilate the space
1. Use mechanical ventilation or as per the sources available.
2. Ventilate at the rate of at least 4 volumes per hour.
3. For larger space require more ventilation.
4. Make sure supply is not contaminated.
Conduct a tail board briefing.
1. Entire crew must attend.
2. Review hazards of entry & work.
3. Review PPE, Contacting rescue.
Complete permit
19. Stand by team/person
Person should be assigned to remain on the outside of the confined space
and be in constant contact ( visual or two way voice communication eg:
walkie-talkie)
Should not have any other duties than to serve as standby & know who
should be notified in case of emergency
Should never leave his post. Be able to communicate sufficiently in a
relevant common language
Test the atmosphere
20. Enter the space & proceed with the work
An attendant shall be posted near the entrance for the duration of work. He
shall be in constant communication with the entrants.
All entrants shall sign the sign in log when entering the space & sign out
while exiting
The attendant shall maintain the permit & sign in log for the duration of the
work
When the job is done , remove all personnel tools & debris from the space.
Close the space.
Close the permit
21. Rescue members/team
Rescuers must be trained in and follow established emergency
procedures and use appropriate equipment and techniques
Unplanned rescue, such as when someone instinctively rushes in to
help a downed co-worker, can easily result in a fatality.
22. Permit to work system
Based on the findings of the risk assessment, appropriate control measures
should be put into place to protect those who may be affected.
The permit should be relevant and as accurate as possible. The permit to
work system consists of an organizes and predefined safety procedure.
Permit to work system has a risk assessment of the proposed work or check
list
It should state the location & details of the work to be done .
Confined Space Entry Certificate is raised before the Permit is Issued. It
remains open for the period that the space is open and is considered safe to
enter or when the permit is closed after 12hrs
The Confined Space Entry Certificate will only be cancelled when the Area
Authority has been advised that the work being carried out is complete, and
there are no linked Permits applying to the same isolation. The confined
space is vacated and any further entry prevented.
23. Notes
Do not enter a space first or alone!
If in doubt-do not enter-no survey is worth risking life or health for.
Use of non explosive proof equipment like cameras, torches. Chipping
hammers, may be allowed provided that it is stated in the permit issued and
the space is safe for hot work or safe for workers and LELis measured
Never thrust ones own senses to determine if the air in a confined space is
safe!
When dragger tube or equal is used for detecting toxic gases the sampling
gas should have sufficient time to pass through the sampling hose
Follow permit to work system