Is "intrinsically safe" higher than "flameproof" explosion-proof grade?

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0 1
Is the protection level of the instrument higher than that of the flameproof instrument?


Intrinsically safe and flameproof are different types of explosion-proof types. Since the intrinsic safety type is divided into three protection levels: ia, ib and ic, and the corresponding EPL levels are different. For example, the protection level of intrinsically safe ic is lower than that of flameproof d, while the protection level of intrinsically safe ia is higher than that of flameproof d. (See the corresponding relationship between explosion-proof type and EPL in the table below for details.)


Correspondence between explosion-proof type and EPL

Therefore, the intrinsically safe and flameproof explosion-proof technologies have their own characteristics and advantages, and are suitable for different products and occasions.

0 2
Can the safety instrument replace the flameproof instrument?


Explosion-proof specific speaking there are many kinds of technology, for the instrument equipment, intrinsically safe explosion-proof technology and explosion-proof technology with its high safety, high operability is widely used.


Definition of Intrinsically Safe Type "I:


An explosion-proof type of electrical equipment that limits the energy of electrical sparks or thermal effects that may be generated inside the equipment and continuous wires exposed to an explosive atmosphere to a level that cannot produce ignition.



Intrinsically safe explosion-proof technology is a kind of "safety design" technology which suppresses the energy of ignition source as explosion-proof means.It is to fundamentally limit the energy of the ignition source, even if the specified failure will not detonate the explosive material in the explosive atmosphere. It is required that the electric spark and thermal effect that may be generated by the equipment under normal operation and fault state are respectively less than the minimum ignition energy and auto-ignition temperature of explosive hazardous gas. The intrinsically safe technology is a low power design technology. Therefore, it can have the advantages of simple structure, small size, light weight, maintenance and replacement under live conditions, high safety and reliability, and wide application range.



Flameproof type "d" definition:
An explosion-proof type of electrical equipment in which the enclosure can withstand an internal explosion of an explosive mixture entering the interior of the enclosure through any joint surface or structural gap of the enclosure without damage, and will not cause external ignition of an explosive gas atmosphere formed by one or more gases or vapors.


Explosion-proof and explosion-proof technology is mainly to isolate the ignition source and allow dangerous gas to enter the explosion-proof enclosure, which may cause explosion. The enclosure is required to be of sufficient strength, with each enclosure bonding surface having a sufficiently long engagement length and a sufficiently small clearance to ensure that an internal explosion does not pass through the flameproof interface and cause an external environmental explosion. Belongs to the gap explosion-proof technology, relying on the gap, meshing length to achieve cooling, flameout effect.
Generally, the principle of substitution is that high EPL grade can replace low EPL grade, or EPL is replaced at the same level, but when it is necessary to pay attention to substitution, it is still necessary to meet the requirements of different explosion-proof types.



Which is more common in chemical plants, the safety instrument and the flameproof instrument?



When dealing with instrument faults, it may be necessary to carry out live maintenance in the explosion-proof area (for maintenance, it is generally necessary to carry out live maintenance, and some faults cannot be judged if they are not charged). Intrinsically safe instruments can be opened and repaired with live electricity, even if the cable is short-circuited, it doesn't matter, while flameproof instruments are usually not allowed to be opened with live electricity.
From the price point of view, for the use of a larger number of small instruments, such as: temperature transmitter, pressure transmitter, valve positioner class flameproof instrument and the price of the safety meter,However, due to the need to add safety barriers to intrinsically safe instruments, the price of a safety barrier is about several hundred to one thousand yuan, and the overall price will be slightly higher than that of using flameproof instruments.
Considering the convenience of maintenance, safety, engineering consistency, price and other factors, intrinsically safe instruments (ia level) are generally preferred in the process unit area of chemical plants, while flameproof instruments are generally preferred in the public works unit area.
The intren-safety instrument is so complicated? Why not choose flameproof ones?


(1) Division of hazardous areas in explosive gas environment


Due to the different environment of the production site,According to the current GB 50058-2014, we divide the hazardous areas of explosive gas environment into: Zone 0, Zone 1 and Zone 2.
Zone 0: an environment where explosive gas mixtures exist continuously or for a long time;
Zone 1: An environment where explosive gas mixtures may occur under normal conditions;

Zone 2: An environment in which explosive gas mixtures are unlikely to occur under normal conditions, or where they are present only for a short period of time.



(2)Classification of explosive substances and corresponding classification of electrical equipment (only for gas)


(1) Class I: for coal mine gas environment.
(2) Class II: For other explosive gas environments except coal mine gas.
According to the maximum test safety gap MESG or minimum ignition current ratio MICR, it is subdivided into: IIA, IIB and IIC. IIA-The representative gas is propane. IIB-The representative gas is ethylene. IIC-The representative gas is hydrogen.
(3) Ignition temperature grouping of explosive gas mixtures




(4) Equipment protection level EPL


According to the classification of hazardous locations, the relationship between the explosion-proof area and the applicable equipment protection level EPL is as follows:


Ga grade:Equipment for explosive gas atmospheres, with a "very high" protection level, is not a source of ignition during normal operation, expected failure or rare failure.
Gb:Equipment for explosive gas atmospheres that has a "high" protection level and is not a source of ignition under normal operating or expected fault conditions.
Grade Gc:Equipment for explosive gas environments, with a "general" protection level, is not an ignition source in normal operation, and some additional protection measures can be taken to ensure that the ignition source is expected to occur frequently (such as lamp failure) will not form an effective ignition.
The current GB3836 series standards and GB50058 have introduced the concept of equipment protection level EPL(equipment protection level). EPL is based on the possibility of the equipment as an ignition source and the different characteristics of the explosive gas environment, explosive dust environment and coal mine methane explosive environment.
(5) Corresponding relationship between partial explosion-proof type and EPL


Refer to the above "corresponding relationship between explosion-proof type and EPL", the equipment can be applied to zone 0 environment when reaching Ga level. The "ia" type explosion-proof type is still an effective product for zone 0, but it is not the only one.
Ga level is applicable to zone 0, zone 1 and zone 2.
The Gb level is applicable to Zone 1 and Zone 2.
Grade Gc applies to Zone 2.


To sum up,Intrinsically safe type and flameproof type are different types of explosion-proof type, they have their own characteristics and advantages, suitable for different products and occasions, should be based on the product can be implemented, the use of the environment, economy, operation and maintenance and other comprehensive consideration.

Extended reading:Why explosion-proof?


According to statistics, there are about 2/3 of the places in the coal mine with explosive substances; in the chemical industry, there are about 80% of the production workshop area with explosive substances; about 60 ~ 80% of the oil production sites and refineries are explosive hazardous places.

An explosion is a material from one state, through physical or chemical changes, suddenly into another state, and release a huge amount of energy.
The three elements of a chemical explosion areExplosive substances, accelerants and ignition sources.


Combustion improtant: such as oxygen in the air.
Ignition source: electrical equipment used in large quantities in the production process, various frictional electric sparks, mechanical wear sparks, electrostatic sparks, high-temperature hot surfaces, etc.


Due to the production of explosive substances and combustion improver is usually difficult to avoid. Therefore, while controlling the abnormal leakage of explosive substances, it is usually the key direction of fire prevention and explosion prevention to eliminate or control the ignition source.
Therefore, it is very necessary to take appropriate explosion-proof measures for electric instruments.