The crux of the controversy: Can an explosion-proof certificate for pressure transmitters be applied universally?
Regarding explosion-proof compliance for pressure transmitters, the industry mainly has three opposing viewpoints, each corresponding to different safety risks and operational logics. After reading this, you'll understand the potential hidden dangers in your company:
1. The "Simple Approach": A certified enclosure is sufficient; modifications don't require further certification.
This is the most common misconception. Many procurement and maintenance personnel believe that the explosion-proof enclosure is the core issue. They think that as long as the enclosure passes explosion-proof certifications such as Ex d/IIC T4, installing internal instrument components and wiring automatically provides explosion-proof performance.
Their reasoning is simple: the enclosure is the "first line of defense" against explosions. As long as the enclosure is not damaged, even slight heating or leakage of internal components will not ignite flammable or explosive gases in the field. Some companies even replace the transmitter's internal chip and modify the wiring to save costs, believing that "as long as the enclosure isn't touched, it won't affect explosion-proof performance."
However, the truth is: this kind of operation is essentially illegal modification, essentially creating a hidden loophole in the "safety defense line."
2. The "Risk-Focused Approach" (Industry Mainstream): A certified enclosure ≠ overall compliance; modifications require recertification.
This view is mostly held by safety engineers, metrology calibration personnel, and industry experts. Their core demand is "compliance first, safety as a safety net."
They argue that explosion-proof certification applies to the "complete equipment," not just individual components. An explosion-proof certificate for the enclosure only proves that the enclosure itself meets explosion-proof standards, but the heating power of internal instrument components, wiring methods, installation clearances, and even a small opening can alter the overall explosion-proof performance of the equipment.
For example, a petrochemical company purchased a batch of pressure transmitters with Ex d enclosures. To facilitate debugging, maintenance personnel drilled holes in the enclosures and installed data cables without any explosion-proof treatment or recertification. Ultimately, during production, the internal components of the transmitter heated up, igniting leaked flammable gas through the opening, causing a small explosion that damaged equipment and resulted in minor injuries.
More importantly, according to GB/T 3836.1-2021, "Explosive Atmospheres Part 1: Equipment - General Requirements," if equipment modification affects its explosion-proof performance, it must be recertified; otherwise, it is considered unauthorized use.
3. The Middle Ground: Scenario-Based Approach, Avoiding Blind Modifications and Excessive Compliance
Some practitioners believe a "one-size-fits-all" approach is unnecessary. The decision should be based on the scenario and the extent of the modification: If it's simply replacing internal components of the same model and specification without altering the housing structure, adding openings, or changing wiring, recertification is unnecessary, but replacement records must be kept and regular explosion-proof testing conducted. If it involves component model changes, housing opening modifications, or wiring alterations, explosion-proof certification must be re-certified to ensure overall compliance with standards.
They also raised a more complex point of contention: Can gas explosion-proof (Ex d) and dust explosion-proof (Ex td) standards be used interchangeably? In the dual-hazardous areas of chemical plants (containing both flammable gases and flammable dust), how should pressure transmitters be selected to meet both explosion-proof requirements?
Industry Warning: These Explosion-Proof "Red Lines" Must Never Be Crossed
Based on the above controversies, we have compiled three core compliance recommendations for the explosion-proof use of pressure transmitters. These recommendations can be directly applied to procurement, operation and maintenance, and project acceptance to avoid safety risks:
1. Reject the "Enclosure First" Mindset: When purchasing, not only check the explosion-proof certificate of the enclosure, but also confirm the explosion-proof certification of the entire device (not just a single component certification). Avoid purchasing "assembled" explosion-proof transmitters (the enclosure is certified, but the internal components are not).
2. Modifications Must Be Certified, Alterations Must Be Tested: Any modifications involving the transmitter enclosure, internal components, or wiring methods must first assess the explosion-proof performance. If necessary, a new explosion-proof certification should be applied for. Unauthorized modifications and drilling are strictly prohibited.
3. Select for Dual Hazardous Areas: In scenarios with both flammable gases and flammable dust, prioritize pressure transmitters with "dual explosion-proof certification" (Ex d + Ex td). Avoid mixing different types of explosion-proof equipment to prevent explosion-proof blind spots.
