hazards of petroleum

7/29/2019 Hazards of Petroleum

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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

hazards of petroleum

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