Protection structure (proof product description)
Explosion levels, safety explosion-proof technology Detail
2014-01-17 19:14:02

 

Detail Explosion safety technology

The concept of explosion :

Explosion is the material from one state, through physical or chemical change, suddenly turned into another state, and release huge amounts of energy. Dramatically speed the release of energy, will make the surrounding objects and suffered severe impact damage.

Explosion must have three conditions:

A ) Explosive substances: with oxygen (air) reacting substances, including gases, liquids and solids. (Gases: hydrogen, acetylene, methane, etc.; liquid: alcohol, gasoline; solid: dust, fiber dust.)

2 ) Oxygen: air.

3 ) ignition sources include: open flames, electrical sparks, mechanical sparks, static electricity sparks, heat, chemical reactions, energy and so on.

Why proof :

Explosive substances : many production sites will have some flammable substances. About two-thirds of the coal mine sites have an explosive substance; chemical industry, about 80 percent more than the presence of explosive material production workshop area.

Oxygen : oxygen in the air is everywhere.

Ignition source : the extensive use of electrical equipment in the production process, a variety of friction sparks , mechanical wear sparks, static electricity sparks, heat and other inevitable, especially when equipment, electrical malfunction.

Many industrial site to meet the objective conditions of the explosion. When mixed with oxygen concentration of explosive material is within the explosion limits, if there is an explosion source, will explode. So it is very necessary to take proof of

The basic principle of Explosion :

To prevent the explosion, is to avoid the explosion of three conditions exist. Since the oxygen (air) everywhere, difficult to control. Therefore, the control and detonate explosive gas source for the two most common proof principle. In the device , the device industry, there is another proof

Principle: control the explosive range. Explosion-proof equipment three common principles: control explosive gases control the explosive range, controlled detonation source

Control of explosive gases  :  

Artificially in dangerous places (we have three conditions required for an explosion scene, said the danger of industrial sites) to create a no explosive gas space in which the equipment is installed , a typical representative of the positive pressure-proof methodExp . Working principle is: in a sealed cabinets, filled with explosive gas-free clean gas or inert gas, and keep the inside air pressure slightly above atmospheric pressure outside the box, the device is installed in the box. Then line analytical instruments used in the explosion and the computer, PLC , operator station or other device placed in the field of pressure explosion-proof equipment cabinet.

Control the explosive range :

Artificially limit the explosion in a limited local area, so that continuous bonding within the range of explosion explode restaurants. Typical method for the explosion-proofExd . Working principle is: to design a device casing is strong enough, according to strict standards of design, manufacture and installation of all the interfaces, so that the explosion occurred in the outer shell casing dangerous gases (explosive gas) explosion triggered Buzhi Yu. Explosion-proof design and manufacturing specification method is extremely strict and installation, wiring and maintenance procedures are very strict. This method determines the flameproof electrical equipment, equipment is often very heavy, power outages and other operations are required, but in many cases the most effective way. 

Controlled detonation source :

Artificially eliminate detonation source, both to eliminate enough spark to detonate, and the elimination of the surface temperature enough to detonate, a typical representative of intrinsic safety explosion-proof method Exi . Working principle is: the use of barrier technology, will provide electrical power to field devices is limited neither produce enough spark to detonate, they can not produce enough to detonate within a safe range of the surface temperature of the device. Accordance with international standards and China's national standards, barrier safety zone when the connected equipment side of any failure (not exceeding 250V voltage), intrinsically safe explosion-proof method to ensure the safety hazards of the scene. Ex ia intrinsically safe equipment in the normal class work, the occurrence of a failure, would not cause the explosion of explosive gas mixtures of two faults occurring. Therefore, this method is the most secure and reliable method of proof.

 

 

 

 

 

 

 

 

 

 

Classified hazardous locations dangerous    

 

 

 

 

 

 

Explosive substances

Zone definition

China Standard

North American standard

Gas ( CLASS I )

Under normal conditions the explosive gas mixture present in place of continuous or prolonged

0 Area

Div.1

Under normal circumstances there may be an explosive gas mixture in place

An area

Under normal circumstances, an explosive gas mixture does not happen only in normal circumstances , place the occasional or short-term appear

2District

Div.2

Dust or fibers(CLASS Ⅱ / Ⅲ)

Under normal circumstances , the fibers may be explosive or combustible dust and air mixture in a continuous , long or short occurs frequently present in place

10District

Div.1

Under normal circumstances , explosive or flammable fibrous dust and air mixture can not occur , not only under normal conditions ,occasional or short spaces appeared

11District

Div.2

 

 

 

 

 

 

 

 

 

 

 Explosion-proof method applicability of dangerous places

 

Ex Type

Code

National Standards

Explosion-proof measures

Applicable area

 

Flameproof

D

GB3836.2

Isolated ignition source exists

Zone1, Zone2

 

Increased safety

E

GB3836.3

Try to prevent ignition sources

Zone1, Zone2

 

Intrinsically Safe

IA

GB3836.4

Limiting energy ignition source

Zone0-2

 

Intrinsically Safe

IB

GB3836.4

Limiting energy ignition source

Zone1, Zone2

 

Pressurized

P

GB3836.5

Separated from hazardous substances and ignition sources

Zone1, Zone2

 

Oil-filled

O

GB3836.6

Separated from hazardous substances and ignition sources

Zone1, Zone2

 

Sand filled

Q

GB3836.7

Separated from hazardous substances and ignition sources

Zone1, Zone2

 

Non-sparking

N

GB3836.8

Try to prevent ignition sources

Zone2

 

Encapsulation

M

GB3836.9

Try to prevent ignition sources

Zone1, Zone2

 

Airtight

H

GB3836.10

Try to prevent ignition sources

Zone1, Zone2

 

Explosion levels of classification standards :

 

Explosion on the applicability of dangerous places:

 

Explosive gases Category :

 

 According to the smallest spark of energy could be detonated, the country and Europe and most countries and regions of the world will explode  dangerous gases into four grades , the following table :

Condition Category

Gas Category

Representative gas

The minimum spark energy detonated

 

 

Mine under

Methane

0.280mJ

 

 

Mine outside plant

Ⅱ A

Propane

0.180mJ

 

 

Ⅱ B

Ethylene

0.060mJ

 

 

Ⅱ C

Hydrogen

0.019mJ

 

 

 

 

 

 

 

 

 

 

 

 

First, the United States and Canada, the spread in the air explosive substances into three CLASS ( Type ): CLASS I gases and vapors   CLASS Ⅱ   dust   CLASS Ⅲ fibers . then separated into gas and dust Group ( Group )

 

 

 

Group Name

Representative of gas or dust

 

 

 

 

 

A

Acetylene

 

 

 

 

 

B

Hydrogen

 

 

 

 

 

C

Ethylene

 

 

 

 

 

D

Propane

 

 

 

 

 

E

Metal dust

 

 

 

 

 

F

Coal dust

 

 

 

 

 

G

Grain dust

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Gas temperature group division :

 

Temperature groups

Safe surface temperature

Common explosive gas

 

T1

≤ 450 ℃

Hydrogen, acrylonitrile 46species

 

T2

≤ 300 ℃

Acetylene, ethylene and other 47kinds of

 

T3

≤ 200 ℃

Gasoline, crotonaldehyde and other 36 kinds of

 

T4

≤ 135 ℃

Acetaldehyde, ethylene tetrafluoroethylene 6 species

 

T5

≤ 100 ℃

Carbon disulfide

 

T6

≤ 85 ℃

Ethyl nitrate and nitrite, ethyl

 

 

 

 

 

 

 

 

 

 

 

 EX (ia) Ⅱ C T6 meanings :

 

 

 

Flag Content

Symbol

Meaning

 

 

 

Explosion Statement

Ex

Meet certain standards for explosion proof, such as China's national standards

 

 

 

Explosion-proof way

ia

Using ia intrinsically safe level methods, can be installed in 0 zone

 

 

 

Gas Category

Ⅱ c

Be allowed to involve Ⅱ Cexplosive gas

 

 

 

Temperature groups

T6

Product surface temperature does not exceed 85 ℃

 

 

 

EX (ia) Ⅱ C meaning:

 

 

 

Flag Content

Symbol

Meaning

 

 

 

Explosion Statement

Ex

Explosion in line with European standards

 

 

 

Explosion-proof way

ia

Using ia intrinsically safe level methods, can be installed in 0 zone

 

 

 

Gas Category

Ⅱ c

Be allowed to involve Ⅱ Cexplosive gas

 

 

 

 

 

 

 

 

 

 

 

 

 

Note : This flag is no temperature group entry , indicating that the device is not in direct contact with the explosive gas