“Comparison of explosion protection ratings: “Intrinsic safety” and “explosion isolation”

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We often talk about whether the instruments used in a particular application are intrinsically safe or flameproof, but the following provides a brief explanation of how intrinsically safe and flameproof types are distinguished from one another. Differences in design concepts: 1. Definition of explosion-proof type: (1) An electrical equipment enclosure that can withstand the explosive pressure of internal explosive gas mixtures and prevent the spread of an internal explosion to the explosive mixtures surrounding the enclosure (Zone 1 explosion-proof technology). 　　(2) It allows hazardous gases to enter the flameproof enclosure, where an explosion may occur; however, the enclosure must have sufficient strength ； Furthermore, the joint surfaces of each enclosure must have a sufficient length of engagement and a sufficiently small gap to ensure that an internal explosion does not pass through the flameproof joint surface and cause an explosion in the external environment. 　　(3) Gap explosion-proof technology, which relies on gaps and engagement length to achieve cooling and flame extinction. Definition of intrinsically safe: (1) Under the conditions specified in the standards (including normal operation and specified fault conditions), any electrical spark or heat effect generated shall not be able to ignite the specified explosive gas environment (explosion protection technology for Zone 0/I). (2) It is a “safe” technology that uses the suppression of ignition source energy as a means of explosion prevention. The equipment is required to have electrical sparks or thermal effects that may occur under normal operation or in the event of a failure, each of which must be below the minimum ignition energy and auto-ignition temperature of the explosive hazardous gases. 　　(3) Intrinsic safety technology is actually a low-power design technique. Therefore, it is well suited for industrial automation instruments. 2. Intrinsic safety type and flameproof type are different types of explosion protection methods. Since the intrinsic safety type is divided into three protection levels: ia, ib, and ic, the corresponding EPL levels vary. For example, the protection level of intrinsically safe ICs is lower than that of flameproof type D, while the protection level of intrinsically safe type IA is higher than that of flameproof type D. Therefore, intrinsically safe and flameproof explosion protection technologies each have their own characteristics and advantages, and are suitable for different products and applications. 3. Characteristics of intrinsically safe and flameproof instruments: Intrinsically safe and flameproof technology is a \"safety design\" technique that uses the suppression of the energy of ignition sources as a means to prevent explosions. Fundamentally limit the energy of the ignition source, so that even in the event of a specified fault, explosive materials in an explosive environment will not be detonated. The equipment is required to have electrical sparks and thermal effects generated under normal operation and in fault conditions that are each lower than the minimum ignition energy and auto-ignition temperature of the explosive hazardous gases. Intrinsic safety technology is a low-power design technique. Therefore, it boasts advantages such as a simple structure, small size, light weight, the ability to be maintained and replaced while still charged, high safety and reliability, and a wide range of applications. Flameproof and explosion-proof technologies mainly involve isolating ignition sources, allowing hazardous gases to enter the flameproof enclosure where an explosion may occur. The enclosure is required to have sufficient strength, and the joints between the various enclosures must have a long enough engagement length and a small enough gap to ensure that an internal explosion does not penetrate the flameproof joints and cause an explosion in the external environment. It belongs to the gap explosion-proof technology, relying on gaps and meshing length to achieve cooling and flame extinction effects. Generally, the substitution principle states that an EPL of a higher grade can replace one of a lower grade, or substitutions can be made between EPLs of the same grade; however, it should be noted that when substituting, the requirements of different explosion-proof types must still be met. 4. Differences in application areas: The explosion-proof type is suitable for installation only in hazardous areas classified as Zone 1 or Zone 2. Intrinsic safety application areas: (1) E*a: Devices that can maintain their explosion-proof properties even in the presence of failures in two components or of other types of faults. Intrinsic safety devices can be installed in Zone 0, Zone 1, and Zone 2 hazardous areas. The E*a intrinsic safety equipment is the only explosion-proof electrical equipment that can be installed in Zone 0. (2) E*b: Equipment that maintains its explosion-proof properties even in the event of a failure in a component or of another type of fault. Intrinsic safety equipment can be installed in Zone 1 and Zone 2 hazardous areas. When dealing with instrument failures in chemical enterprises, live maintenance must be performed in explosion-proof areas. Intrinsic safety instruments can be opened for maintenance while still under power; it doesn’t matter if the cables are short-circuited. In contrast, flameproof instruments generally cannot be opened while under power, and additional safety measures are required when performing maintenance on them while they are powered on. In terms of price, for small instruments with high usage levels, such as temperature transmitters, pressure transmitters, and explosion-proof or intrinsically safe valve positioners, their prices are similar. However, since intrinsically safe instruments require the use of safety barriers, and the cost of each such barrier is around a few hundred to a thousand yuan, the overall cost of intrinsically safe instruments is slightly higher than that of explosion-proof instruments. Considering factors such as maintenance convenience, safety, engineering consistency, and cost, intrinsically safe instruments (IA category) are generally given priority in the process unit areas of chemical plants, while flameproof instruments are typically preferred uniformly in the utility unit areas. In summary, intrinsically safe and flameproof types are different categories of explosion-proof designs, each with its own characteristics and advantages, suitable for different products and applications. The choice should be made by taking into account factors such as the feasibility of implementation, the operating environment, cost, and operation and maintenance requirements.