Post on 14-Apr-2018
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OxygenFuel
Ignition Source
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FLAMMABILITY
Evaporation Liquid turns to vapour Flammable vapours
Petroleum gives off flammable vapours (hydrocarbon gas)
Flammable mixtures
Flammable gas mixed with oxygen Temperature
The rate of evaporation is related to temperature
Flashpoint
The lowest temperature at which enough flammablevapours form to create a flammable mixture with air
Volatile petroleum Petroleum with a FLASHPOINT < 600c
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FLAMMABILITY
Lower Flammable (Explosive) Limit below this limit there is insufficient hydrocarbon gas inthe mixture to support and propagate combustion
the mixture is said to be too lean.
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FLAMMABILITY
Upper Flammable (Explosive) Limit the limit above which there is insufficient oxygen in themixture to support and propagate combustion
the mixture is said to be too rich.
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FLAMMABILITY
Flammable Range The relatively narrow range of mixtures between theupper & lower limits
WILLSUPPORT & PROPOGATE COMBUSTION
UFL
LFL
FLAMMABLE RANGE
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Flammable Range Diagram
LFL1
10
5 10 15 20
FlammableRange
Oxygen - % by Volume
Hydrocarbons% by Volume
UFLApprox11.4% O2
5
Insufficient O2 to
support combustion
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IGNITION SOURCES
Direct Heat Smoking Welding Burning
Mechanical sparks Chipping Dropped tools
Collision
Electrical energy Electrical sparks Electrical arcing Lightening
Static discharge
Chemical energy Spontaneous combustion
Metallic smears Auto-ignition Pyrophoric Iron Sulphide
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Electrostatic Hazards
3 stages of static electricity charge separation
charge accumulation
electrostatic discharge
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Charge Separation
2 dissimilar materials come together
+ve
-ve
Charges separate Materials become positively ornegatively charged
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Charge Separation
The flow of oil through the pipeline system
Static Accumulator Oils Oils which insufficient conductivity to dissipate a charge
Less that 50 picoSiemens/metre
The settling of sediment or water droplets through oil
Oil splashing into an empty tank
Water droplets or particles ejected from a nozzle
during tank washing Synthetic ropes rubbing on PVC gloves
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Charge Accumulation
Charges attempt to recombine Charge Relaxation
Poor conductors accumulatea charge
CHARGED LIQUID
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Objects which might be electrically
insulated in hazardous situations Ship/shore hose couplings and flanges if morethan one length of non-conducting hose or pipe isused in a string.
Portable tank cleaning machines. Manual ullaging and sampling equipment. The float of a permanently fitted ullage device if
it lacks an earthing path through the metal tape. A metal object such as a can floating in a static
accumulating liquid A loose metal object while it is falling in a tank
during washing operations
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Electrostatic Discharge
Electrical breakdown between 2 points Generally occur at protrusions
CHARGED LIQUID
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Electrostatic Discharge
Between sampling equipment and thesurface of a charged liquid
Between an unearthed object on thesurface of a liquid and the tank structure
Between unearthed equipment and the tankstructure
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Precautions
Earthing the electrical connection of equipment to
the main body of the earth to ensurethat it is at earth potential.
On board ship this is achieved byconnection to the main structure of theship.
Bonding the connecting together of metal partsto ensure electrical continuity.
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Precautions
Limit initial loading rate Prevent excess water reaching tanks Anti-static Additive from shipper
Raises conductivity to 100pS/m Ensure electrical continuity of hoses Only introduce earthed & bonded
equipment into cargo tanks Ullaging & Sampling precautions
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TOXICITY
The ability of a substance to cause damage to
lining tissue & impair the nervous system
Caused by petroleum liquid or vapour
4 avenues of exposure: -
Inhalation
Absorption
Ingestion
Injection
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INHALATION
Hydrocarbon gas produces narcosisLow
concentrations
High
concentrations
Eye irritation
Headache
Diminished responsibilities
Drowsiness
Insensibility
Paralysis
Death
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ABSORPTION
Skin & eye irritation Removal of essential oils
Dermatitis
Serious skin disorders with prolonged &
repeated contact
Carcinogenic
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INGESTION
Low risk of ingestion in operational practice Low oral toxicity
Acute discomfort & nausea if swallowed
Possible serious consequences if oil enters
lungs during vomiting
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THRESHOLD LIMIT VALUE
(TLV) The maximum concentration of cargo
vapours in air to which personnel may be
exposed without adverse effect The toxicity of a substance is measured in
parts per million (ppm) of volume of gas in
air The exposure timeis also a factor
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TLV-TWA
Time Weighted Average The maximum concentration of vapour in
air to which personnel may be exposed for
a normal 8 hour working day or 40 hour
working weekwithout adverse effect
A reference to TLVmay be taken to mean
TLV-TWA
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TLV-STEL
Short Term Exposure Limit The maximum concentration of vapour in
air to which personnel can be exposed for a
per iod of 15 minutes without adverse effect
Maximum 4 such periods per day
Minimum 1 hour between each period
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TLV-C
Ceiling The concentration of vapour in air that must
not be exceeded
Applied to fast acting substance
Ammonia
Chlorine
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AROMATIC
HYDROCARBONS Benzene
Toluene
Xylene The presence of these substances greatly
increases TOXICITY
TLV of Benzene 5 ppm Effects may include blood & bone marrow
disorders
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HYDROGEN SULPHIDE
(H2S) Present in unstabilised crude
Also in some products
Naphtha
Gas oil
Rotten egg smell
TLV - 10 ppm
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HYDROGEN SULPHIDE
(H2S) Detectable by smell only in
concentrations < 1ppm
First effect is loss of sense
of smell
Eff t f HEffects of H S t t ti b TLVS at concentrations abo e TLV
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Effects of HEffects of H22S at concentrations above TLVS at concentrations above TLV
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Effects of H2S at concentrations
above TLV 50-100 ppm
Eye & respiratory tract irritation after 1 hour
200 - 300 ppm
As above but more severe after 1 hour
500 - 700 ppm
Dizziness, headache and nausea after 15 minutes
Loss of consciousness and possible death after 30 - 60 minutes
700 - 900 ppm Rapid unconsciousness, death within a few minutes
1,000 - 2,000 ppm
Instantaneous collapse and cessation of breathing
Death
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INERT GAS
Main hazard is low O2 content
Gas freeing operations sufficient to dilute
toxic constituents to below TLVs
Toxic constituents of IG
Nitric oxide
Nitrogen dioxide
Sulphur dioxide
Carbon monoxide
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O2 DEFICIENCY
Causes of low O2 levels in enclosed spaces
Presence of inert gas
RustingHardening of coatings & paint
Normal O2 content 21% by volume
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EFFECTS OF O2 DEFICIENCY 21% - 16%
Breathing becomes deeper & faster
16% - 10%
Impairment to breathing very apparent
Unconsciousness in most individuals
10% - 5%
Unconsciousness inevitable, perhaps rapid
Death will follow if victim not removed
< 5% Immediate unconsciousness Irreversible brain damage within minutes
Death
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EFFECTS OF O2 DEFICIENCY
Symptoms indicating that an atmosphere isdeficient in oxygen may give inadequatenotice of danger
Most persons would fail to recognise thedanger until they were too weak to be ableto escape without help
This is especially so when escape involvesthe exertion of climbing