A card-type temperature sensor is installed in the explosion-proof junction box; is a separate explosion-proof certification required?
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As the title says. Normally, we configure explosion-proof junction boxes according to the classification of explosion-proof zones. For example, if the junction box is located in Zone 2, an intrinsically safe cartridge-type temperature sensor needs to be installed inside it; in most cases, an enhanced safety type of junction box is sufficient to meet the requirements. But recently, I came into contact with a junction box manufacturer who stated that junction boxes are meant for holding wiring terminals and connections; they cannot be used to house electrical components such as temperature sensors. For junction boxes designed for enhanced safety, separate certification is required when incorporating such electrical components – in other words, the box with the temperature sensor installed must be submitted for certification, along with the specified model of the temperature sensor. I wonder if such a saying exists?
Yes, there is such a saying. If an explosion-proof junction box is to house non-conventional electrical components (such as temperature transmitters), it may indeed require additional explosion-proof certification. This is because the explosion-proof certification for an explosion-proof junction box usually applies only to the structure of the junction box itself and its explosion-proof classification, such as increased safety type. When other electrical components are installed inside the junction box, the explosion-proof properties of the entire system may be affected; therefore, it may be necessary to conduct new explosion-proof certification for the entire device to ensure safety and compliance. This approach helps ensure that the junction box and its internal components meet explosion-proof safety requirements in actual use. You can consult specific certification bodies further or review relevant explosion-proof standards to obtain more detailed information. .
But in actual construction projects, I’ve never heard of anyone having such a requirement; moreover, considering things like temperature changes, and the large number of manufacturers and models available, it’s not practical to obtain certification for each one separately. I also don’t know what the standard for this is – is it required in all explosion-proof areas, or only in certain areas?
I’ll take the lead on this; I hope everyone can offer some suggestions based on the actual situation on site
In actual engineering projects, the on-site operations are usually carried out in accordance with the specific requirements of the project as well as prevailing **or industry standards. The interpretation and implementation of standards may vary across different projects and regions. Some projects may require more stringent explosion-proof measures, including additional explosion-proof certification for the electrical components installed inside the junction box. Some projects may consider that, as long as the electrical components installed inside the junction box possess the appropriate explosion-proof certification and do not affect the overall explosion-proof performance of the junction box, no additional certification is required. To obtain more accurate advice, consider the following aspects: 1. Consult local safety regulatory authorities or certification bodies to understand the relevant regulations and standard requirements. 2. Draw on the practical experience of similar projects to understand industry best practices. 3. Check the specific project specifications or contract requirements to see if there are clear provisions. 4. Consult the manufacturers of explosion-proof equipment or professional explosion-proof engineers for expert advice. The final approach should be based on ensuring site safety and meeting regulatory requirements. If the project has explicit requirements for explosion-proof certification, or if there are uncertainties, it is recommended to follow stricter standards to ensure the safety of construction. .
I just checked it – 3836.15 states that enclosures with only an explosion-proof certificate for the Ex components cannot be used directly, whether they are of flameproof or increased safety type; certification can only be obtained after the entire assembly is completed. The internal components of the equipment cannot be changed without re-evaluation of the equipment. It is estimated that this manufacturer does not have certified explosion-proof temperature change chambers
Thank you for the answer. In fact, I have also been involved in the acceptance testing of many complete sets of equipment, such as turbines, pumps, and blowers. The common types of sensors used are those for measuring temperature changes and vibration displacement. I have never come across any requirement for obtaining separate certification for explosion-proof features; it is generally assumed that an explosion-proof enclosure is sufficient, or perhaps I simply haven’t paid much attention to this aspect.
A temperature transmitter also has five wires: three of them are connected to the PT100, with almost no current flowing through them, and there are two signal wires. In our case, they are connected to the DCS cabinet of Zhejiang University, at the analog input points; the maximum short-circuit current is 25 MA, which is very safe.
Is a separate explosion-proof certificate required for explosion-proof junction boxes? As special devices used in flammable and explosive environments, explosion-proof junction boxes must undergo strict testing and certification to ensure their safety performance. In China, explosion-proof electrical equipment must comply with standards such as GB3836.1-2021 \"Explosion-proof electrical equipment – Part 1: General requirements for equipment\" and GB3836.2-2021 \"Explosion-proof electrical equipment – Part 2: Explosion-proof type \"d\" equipment\", and it is necessary to obtain certification from an explosion-proof product certification body designated by the Certification and Accreditation Administration. If the explosion-proof junction box is equipped with electrical components such as card-type temperature sensors, and these components together with the junction box form a complete explosion-proof system, then this system usually needs to be certified for explosion protection as a whole. This means that the entire system (including the junction box and internal electrical components) must comply with relevant explosion-proof standards and obtain the corresponding explosion-proof certification. Can enhanced safety junction boxes be used directly to house electrical components? There are significant differences between enhanced safety junction boxes and explosion-proof junction boxes in terms of protection level, safety performance, and applicable environments. Enhanced safety junction boxes are generally suitable for locations with low temperatures and low humidity, while explosion-proof junction boxes are designed for harsh environments characterized by flammability, explosiveness, corrosivity, high temperatures, and high humidity. If an enhanced safety junction box is to be used to house electrical components, especially those that need to be used in flammable and explosive environments, special attention must be paid to whether its safety performance meets the required standards. In some cases, enhanced safety junction boxes may require additional safety assessments and modifications to ensure they meet the safety requirements of specific environments. Regarding the claim made by wiring box manufacturers that the discharge components of enhanced safety wiring boxes require separate certification, this is likely due to specific requirements in particular projects or environments. In some cases, to ensure the safety performance of the entire system, it is indeed necessary to obtain an overall explosion-proof certification for the junction box and its internal electrical components.
Generally, large manufacturers have the necessary certifications; it’s a good idea to consult two more manufacturers. Explosion-proof components need to be placed in the enhanced safety box; it doesn’t matter for the flameproof box, but care should be taken to ensure that the nameplate indicates it is a control box.