Explosion Protection System

7/30/2019 Explosion Protection System

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EXPLOSION

An explosion is a rapid increase in volume and

release of energy in an extreme manner,

usually with the generation of high

temperatures and the release of gases.

The released energy is then dissipated by a

variety of mechanisms, including formation of

a pressure wave; projectiles, thermalradiation, and acoustic energy.


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CAUSES

Natural

Chemical

Electrical and magnetic

Mechanical and vapour

Nuclear


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CAUSES

Gases, vapours and mists escape during theproduction, processing, transportation and storage offlammable substances in the chemical andpetrochemical industries, in mining and in many other

sectors. During many processes, especially in food industries,

combustible dusts are also created.

These flammable gases, vapours, mists, and dusts forman explosive atmosphere with the oxygen in the air.

If this atmosphere is ignited, explosions take place,which can result in severe harm to human life andproperty.


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The Basic Physic Principles


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What is a HAZARDOUS

AREA?

A hazardous area is defined as an area inwhich an explosive atmosphere is present, ormay be expected to be present, in quantities

such as to require special precautions for theconstruction, installation, and use of potentialignition sources.

Examples:

Petrochemical, Chemical, SewerageTreatment, Grain Handling, Coal Mining


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Hazardous Area Classification

A Hazardous Area is classified according to the

following 3 criteria :-

The type of hazard - gas or dust.

Probability of explosive atmosphere occurring.

The nature of the hazard.


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TYPE OF HAZARD

CLASS I - Gas/vapour/mist. CLASS II - Dusts.


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PROBABILITY OF HAZARD OCCURRING


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NATURE OF HAZARD

Group I - Coal Mining (methane) Group II - Other Industries

Group IIA (e.g. propane, butane)

Group IIB (e.g. ethylene, butadiene) Group IIC (e.g. acetylene, hydrogen)


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Basic principles of explosion

protection

1

Preventing the formation of anexplosive atmosphere

2

Avoidance of the ignition of anexplosive atmosphere

3 Mitigation of the effects of an

explosion to an acceptable extent


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Preventing explosive atmospheres

(Primary Explosion Protection)

The term primary explosion protection refers to

all precautions, which prevent a hazardous

explosive atmosphere from being created. This

can be achieved by:> avoiding flammable substances (replacement

technologies)

> inerting (addition of nitrogen, carbon dioxide etc.)> limitation of the concentration by means of

natural or technical ventilation


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Avoiding ignition of explosive

atmospheres

If the danger of explosion cannot be

completely or only partly avoided by measures

of preventing the formation of an hazardous

explosive atmosphere, then measures must betaken that avoid the ignition of the explosive

atmosphere.


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Mitigation of the explosion effects

(Constructive Explosion Protection)

If hazardous explosive atmospheres cannot besafely avoided and their ignition cannot beexcluded, then measures must be taken which

limit the effect of explosions to a safe degree. e.g. by means of:

> explosion pressure resistant construction

> explosion relief devices> explosion suppression by means of

extinguishers


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Designing Facilities for Use of

Explosive Materials

Pressure rate-of-rise detectors can activate a device orsystem to extinguish a potential explosion before itreaches an explosive stage.

Controlling ventilation & humidity level above 25%

Fixed monitoring for mass and size fraction using light-scattering laser photometers providing real-timeaerosol mass readings.

Inerting purging supply of oxygen when flammableatmospheres are detected with care being taken forthose workers in the area

Min Ignition Energy, Temp.,Concentration.


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Design of Buildings

Relief of overpressure break away & blow outwalls and window openings to minimizedestructiveness (explosion release panel)

Shielding personnel and equipment deflectionof shock wave so as not to pass unobstructivedinto another work area.

Explosive proof wall or barrier

Burst vessel/container disk venting away totransmit pressure wave harmlessly to outsideatmosphere


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Protection Measures

The facility has an emergency action plan. Dust collectors are not located inside of buildings. (Some

exceptions)

Rooms, buildings, or other enclosures (dust collectors) have

explosion relief venting distributed over the exterior wall ofbuildings and enclosures.

Explosion venting is directed to a safe location away fromemployees.

The facility has isolation devices to prevent deflagration

propagation between pieces of equipment connected byductwork.

The dust collector systems have spark detection andexplosion/ deflagration suppression systems.

Emergency exit routes are maintained properly.


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Explosion Protection Techniques

Explosion Containment

Ex d - Flameproof enclosure

An enclosure for electrical equipment that willwithstand, without damage, an explosion of a

prescribed flammable mixture.

Applications

Switch gear, motors..

(all apparatus producing arcs)


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EnergyLimitation

Ex i - Intrinsically safe

- Limitation of electrical energy or thermaleffect under normal or abnormal conditions

that cause ignition of a potentially explosive

atmosphere


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Dilution

Ex v Ventilation

Avoidance of Ignition Source

Ex e - Increased safety

Ex n - Non-sparking (inherent)


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Documents

Explosion Protection System