|
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 |
Ⅰ |
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 |
|||||||||