oil & gas storage - module - 2

8/4/2019 Oil & Gas Storage - Module - 2

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Oil & Gas Storage


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The occurrence and extent of

flammable atmosphere

Hazardous area

Non-hazardous area


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Hazardous area

An area in which explosive gas mixture

(flammable) are or may be expected to be

present in the quantities such as to require

special precautions for construction and use ofelectrical apparatus.


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Non- Hazardous area

Area in which explosive gas air mixture are

not expected to be present in quantities such

as to require special precautions for

construction and use of electrical apparatus.


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Different Zones

Zone-0

flammable atmosphere is

continuously present

Zone- I Flammable atmosphere is likely to

occur under normal conditions

Zone-II flammable atmosphere is likely to

occur under abnormal conditions and if it

does, will only exist for a short time.


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Factors which influence the extent of

vapor drift

Quantity of vapor released in unit time.

Velocity of vapor discharge

vapor density

Gasoline 3-4 times of air

Butane 2

Propane 1.5

Wind velocity and direction

Surrounding atmosphere.


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Petroleum Escaping as Liquid

Drip leakage of petroleum liquid

Small spillages of petroleum liquid

Major escape of petroleum liquid


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Detection of Flammable atmosphere

Detect leaks of flammable vapours at unattended or

infrequently attended pump-houses and compressors

Give warning at locations where industrial type

electrical equipment has been installed, eitherbecause intrinsically safe or flame proof equipment

is not procurable.

Give warning at locations where smoking is

permitted in selected isolated places, or where the

applications of heat, as by welding, may give off

vapor in flammable concentration.


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Fixed System

The atmosphere at each location is monitored on afixed cycle which may be 3 or 4 or 5 min intervals.

Gives continuous record of the vapourconcentration, or to report, by visual or audiblewarning signal, small leaks of flammable vaporcorresponding to 15 to 60 % lower explosive limit.

Give danger signal when the sample vapour isabove 25% of LEL.


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Portable system

For continuous monitoring

Gives audible alarm as soon as the vapour

concentration in the area exceeds 20 % of LEL

The instrument is supplied with 2 m hose to facilitatesmapling from enclosed tanks and service ducts

Hand-operated aspirator is available for spot

sampling

Particularly useful in searching for small leaks.


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Sources of Ignition

Electrical apparatus

Stray electric currents

Static electricity

Lightening

Non-electrical sources of ignition


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Electrical apparatus

Source of ignition

Hot-filament of electric lamp

Heating effect of an electric current may be such

as to raise the surface temperature of the apparatusabove the spontaneous ignition temperature of

flammable atmosphere in the vicinity of the

apparatus.

Mechanical breakdown of the electrical insulation

of apparatus may cause danger through

overheating, arcing, or sparking.


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Safety precautions

The use of equipment specifically designed for use

in hazardous area.

Attention to design layout in such a way thatprobability of hazardous atmosphere and an

electrical ignition occurring simultaneously as

remote as possible.

Complete suppression or avoidance of the

hazardous atmosphere so as to render unnecessary

any special electrical precautions.


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Intrinsically safe apparatus

Apparatus so constructed that when installed and

operated under conditions specified by certifying

authority, any electrical sparking that may occur innormal working, either in the apparatus or in the

circuit associated therewith, is incapable of causing

an ignition of prescribed gas or vapor.


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Stray Currents

Stray currents are those which are unintentionally

present and may result from leakage

oil & gas storage - module - 2

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