Introduction to Intrinsically Safe Mobile Phones
In on-site operations of the oil extraction, oil refining, petrochemical, and natural gas industries, intrinsically safe mobile phones must be used to ensure the safety of workers. These hazardous environments may have flammable and explosive gas leaks, and the use of ordinary mobile phones would pose potential safety risks. In contrast, explosion-proof mobile phones adopt special safe circuit designs to strictly control current levels, making them suitable for such environments.
What are the Explosion-Proof Safety Standards?
Intrinsically safe explosion-proof standards form a regulatory system that achieves explosion protection by limiting the electrical energy of equipment circuits. Explosion-proof areas are classified based on the frequency and duration of the presence of explosive substances. Together, they provide the basis for equipment selection and safe operation in hazardous environments, with detailed explanations below:
Intrinsically Safe Explosion-Proof Standards
Intrinsically safe phone (known as “i” protection) focuses on limiting parameters such as voltage, current, capacitance, and inductance of electrical equipment. This ensures that electric sparks and thermal effects generated by the equipment during normal operation or fault conditions cannot ignite the surrounding explosive mixtures.
Equipment Protection Levels
Intrinsically safe explosion-proof equipment is divided into three levels based on safety redundancy capabilities, suitable for different hazardous areas:
- Ex ia: Maintains safety even with two independent faults. Suitable for Zones 0-2 and Zones 20-22, with the highest safety level.
- Ex ib: Maintains safety with one fault. Suitable for Zones 1-2 and Zones 21-22.
- Ex ic: No fault redundancy required. Only suitable for Zone 2 and Zone 22, with a relatively lower safety level.
Definition of Explosion-Proof Areas
Explosion-proof areas are categorized into two types based on the physical state of explosive substances: explosive gas atmospheres and explosive dust atmospheres. The classification is determined by the frequency and duration of the presence of explosive substances, as detailed below:
Explosive Gas Atmospheres (in accordance with IEC 60079, GB 3836.1)
- Zone 0: Explosive gas mixtures are present continuously, for long periods, or frequently. This is the highest risk level. Typical scenarios include the upper space above the liquid surface inside oil tanks and specific locations where flammable gas leaks and accumulates for long periods.
- Zone 1: Explosive gas mixtures may occur during normal operation, with a typical presence time of 10-1000 hours per year. Typical scenarios include chemical plant pump rooms and enclosed, poorly ventilated areas in petrochemical facilities.
- Zone 2: Explosive gas mixtures are unlikely to occur during normal operation. If they do appear, it is only occasionally and for short durations, usually less than 10 hours per year. Typical scenarios include the outer perimeter of well-ventilated oil tank areas and open-air petrochemical sites.
Explosive Dust Atmospheres (in accordance with IEC 61241, GB 12476)
- Zone 20: Combustible dust is present continuously or frequently, sufficient to form dust mixtures or extremely thick dust layers, with a presence time of ≥1000 hours per year. Typical scenarios include the interior of flour mill grinders and the inside of dust storage tanks.
- Zone 21: Combustible dust mixtures of explosive concentration may be generated during normal operation, with a dust presence time of 10-1000 hours per year. Typical scenarios include powder conveyor belts and specific areas outside dust containers.
- Zone 22: Dust mixtures are not expected during normal operation. They only appear occasionally and for short durations under abnormal conditions such as equipment failures, with a dust presence time of ≤10 hours per year. Typical scenarios include the surrounding area of exhaust outlets when bag filters malfunction and dust accumulation areas on warehouse floors.
