Explosion protection rating of the instrument

You need to learn some knowledge about explosion prevention. The selection of the explosion-proof type first requires determining which zone the instrument is located in: Zone 0? Zone 1 or Zone 2? Now, to answer your question: 1. If it is Zone 0, only intrinsically safe Type IA instruments can be used; in Zones 1 and 2, both intrinsically safe and flameproof instruments are acceptable. Intrinsically safe and flameproof are two different types of explosion protection mechanisms. In simple terms, intrinsically safe design means that the instrument itself is inherently safe and does not generate any sparks that could cause ignition, while flameproof design involves an explosion-proof casing that prevents sparks or explosions inside from spreading outside and igniting the surrounding environment. 2. The explosion-proof rating of this locator you proposed is the highest level; it can definitely be used. 3. Intrinsically safe cables and ordinary control cables can be placed in the same conduit, but they need to be separated by a partition, which is in compliance with the standards.

Do ExdIICT3 explosion-proof instruments meet the explosion-proof requirements? ExdIICT3 explosion-proof instruments are designed in accordance with the standards set by the International Electrotechnical Commission (IEC) for use in environments where explosive gases are present. Among them, “Exd” indicates that the electrical equipment has explosion-proof properties; “II” means the equipment is suitable for use in explosive gas environments other than coal mines; “C” denotes that the equipment is suitable for use with gases such as hydrogen, acetylene, and ethylene; “T3” indicates that the maximum surface temperature of the equipment does not exceed 200°C. For flammable and explosive gases such as hydrogen and carbon monoxide used in a company’s new production lines, ExdIICT3 explosion-proof instruments are suitable, as they meet the explosion protection requirements for these gases. Selection of valve positioner: The Yaskawa AVP100-H type valve positioner mentioned has an explosion protection rating of E*a IIC T4 Ga. Among them, “E*a” indicates that the electrical equipment possesses intrinsically safe properties; “IIC” also means it is suitable for gases such as hydrogen, acetylene, and ethylene; “T4” signifies that the maximum surface temperature of the equipment does not exceed 135°C; “Ga” denotes the protection level of the equipment, making it suitable for explosive methane environments in coal mines. Considering the type of gas used in the new production line, the explosion protection rating E*a IIC T4 Ga of the AVP100-H valve positioner meets the requirements, as it is also suitable for flammable and explosive gases such as hydrogen. However, it should be noted that although its explosion-proof rating meets the requirements, it is still necessary to ensure that the valve positioner can satisfy the other technical requirements and operating conditions of the production line. Can intrinsically safe instruments and ordinary cables be wired in the same conduit? Intrinsically safe instruments are those that possess intrinsic safety features; the electrical sparks and heat generated by their circuits under normal operation or specified fault conditions cannot ignite the specified explosive gas mixtures. Ordinary cables, on the other hand, do not have such explosion-proof requirements. In accordance with explosion-proof safety principles, and to avoid potential safety hazards, it is generally not recommended to run intrinsically safe instruments and ordinary cables in the same conduit. This is because ordinary cables may interfere with the circuits of intrinsically safe instruments or affect their explosion-proof properties. Therefore, it is recommended to route the circuits of intrinsically safe instruments separately from ordinary cables to ensure isolation and safety between them. In summary, regarding the explosion protection requirements for the company’s new production line: ExdIICT3 explosion-proof instruments meet the requirements. The explosion protection rating of the Yamaku AVP100-H valve positioner, E*a IIC T4 Ga, also meets the requirements, but other technical specifications and operating conditions must also be taken into consideration. It is not recommended to run intrinsically safe instruments and ordinary cables in the same conduit to ensure safety and isolation.

It’s really comprehensive! Obviously a big shot. I have only one question: normally, if an explosion-proof area is classified as Zone 0, then simple flameproof instruments would not meet the explosion-proof requirements, right? Or is it that hydrogen and carbon monoxide, which are used as raw materials in production, are not classified as Zone 0?

Zone 0 can only use intrinsically safe instruments of type E*a; explosion-proof EX types are not acceptable. The classification of explosion hazard zones is based on the likelihood and randomness of leakage of the process media in those zones, rather than considering only the properties of the media.

That’s right; simple explosion protection is not sufficient to meet the requirements of Zone 0. Flammable and explosive gases such as hydrogen and carbon monoxide can create a Zone 0 under certain conditions: if explosive hazardous gases are present for ≥1000 hours per year, then it can be considered a Zone 0. If the raw materials for production are hydrogen and carbon monoxide, with 8,000 hours of production per year, it will definitely exceed the limit.

This post was last edited by ycz_305 on 2024-6-6 at 10:36. Thank you for your patient explanations; I have a few more questions: 1. For new projects that haven’t been designed by an architectural firm, how is it determined whether that area belongs to Zone 0, Zone 1, or Zone 2? 2. For the new project mentioned above, if explosion-proof instruments of type ExdIICT3 are used for instruments such as those for measuring temperature, pressure, and flow rate, cannot the valve positioner be an AVP100-H model? (I have quite high confidence in Yamaki’s positioners.) If it is chosen, does it require a separate safety barrier, intrinsically safe cables, and cable trays? 3. For the new projects mentioned above, if electromagnetic flowmeters are to be used, for example, the explosion-proof ratings of Shanghai Guanghua electromagnetic flowmeters are only EXdmiaⅡBT4 and EXdeⅡBT4 – does this mean that these flowmeters do not meet the explosion-proof requirement for the aforementioned new projects? How to choose a flow meter at this time? 4. In a production process, there are motors and instruments. The instrument design institute has chosen intrinsically safe instruments for design, while explosion-proof motors have been selected for the motors – is there any contradiction in this? 5. What other technical requirements and working conditions need to be considered when selecting a locator? What are those aspects? Does the hero take apprentices? Elder Sun, put away your supernatural powers! :lol

A lot of information is actually available online; for things I don’t understand, I first look up relevant materials before responding – it’s also a process of learning for me. By discussing these topics, we can all learn from each other. 1. The classification of explosion-proof areas must be based on specific process conditions, the production environment, and the properties of the hazardous substances. The following is the judgment criterion for Zone 0: Areas where hazardous substances are present for an extended period or continuously. Zone 1: Areas where hazardous substances may be present. Zone 2: Hazardous substances are generally not present; they only appear occasionally for short periods in abnormal circumstances. 2. Regarding instrument selection and the use of the AVP100-H valve positioner: If instruments for measuring temperature, pressure, flow rate, etc., are all explosion-proof models of type ExdIICT3, then for the selection of the valve positioner, the AVP100-H is an intrinsically safe instrument (E*a IIC T4 Ga) that can be used in Zones 0, 1, and 2. If the AVP100-H valve positioner is selected, and Zone 0 is indeed present in the project, then it is necessary to use safety barriers, intrinsically safe cables, and cable trays to ensure the intrinsical safety of the entire system. 3. Explosion-proof rating and selection of electromagnetic flowmeters: If the explosion-proof ratings available for Shanghai Guanghua electromagnetic flowmeters are only EXdmiaⅡBT4 and EXdeⅡBT4, the choice must be made based on the explosion-proof requirements of the new project. If the project requires a higher explosion protection rating (such as ExdIICT3), an electromagnetic flowmeter that meets this requirement must be selected. When making a choice, in addition to the explosion protection rating, other factors such as the flow meter’s performance, accuracy, and stability also need to be considered. 4. Are the explosion-proof requirements for motors and instruments contradictory? Motors with explosion-proof designs are used to prevent explosions that occur inside them from spreading outside, while intrinsically safe instruments are chosen to ensure that they do not generate sparks or energy that could ignite explosive mixtures. These two approaches are not contradictory; rather, they represent explosion-proof measures tailored to the different requirements of various devices and environments. 5. Other technical requirements and operating environment for selector choice Besides the explosion-proof rating, other technical requirements and the operating environment must also be taken into account when selecting a locator: 1. Accuracy and resolution: To ensure they meet the process requirements. 2. Response time: Fast response to satisfy process control needs. 3. Operating temperature and pressure range: To ensure the locator can function properly in the actual operating environment. 4. Corrosion resistance: For corrosive media, a locator with corrosion resistance is required. 5. Ease of installation and maintenance: To facilitate on-site installation and subsequent maintenance

Hello, Engineer Fu! I still would like to discuss with you the knowledge related to explosion protection: 1. The criteria for determining explosion-proof zones seem rather vague; in the absence of design by a professional design firm, what basis do instrument technicians use to determine whether flammable gases are present in a particular area on a permanent basis? How many hours per year are gaseous substances present? Which district should it belong to? 2. If a workshop is classified as Zone 1 and the temperature and pressure instruments are selected with an explosion protection rating of ExdIICT3, then without any partitions in the cable trays, nor the use of safety barriers or intrinsically safe cables, cannot other instruments such as valve positioners use intrinsically safe versions? Can only choose instruments from other brands that have an explosion-proof rating? If intrinsically safe instruments are also used for instruments such as those for temperature and pressure, but only flameproof flowmeters are available, can they be used? 3. If a workshop is classified as Zone 0 and the production material is hydrogen, can explosion-proof flexible hoses be used? (Explosion-proof flexible hoses are suitable for Zones 1 and 2, as well as for explosive gas environments of Classes IIA and IIB.) If they cannot be used, what should be chosen instead? 4. Is the cost of intrinsically safe instruments combined with intrinsically safe cables and safety barriers significantly different from the cost of flameproof instruments combined with ordinary cables?