In hazardous areas such as petroleum, chemical, natural gas, and pharmaceuticals where flammable and explosive gases or dust exist, explosion-proof pressure transmitters are not only key process measuring instruments, but also important defense lines to ensure safe production. The long-term reliability of its operation largely depends on the design and material selection of the sealing structure. Once the seal fails, it not only leads to inaccurate measurements, but also may cause medium leakage, resulting in safety accidents.
1、 Multiple sealing design is the foundation of safety
Explosion proof pressure transmitters typically adopt a "triple sealing" strategy:
1. Process interface sealing: Metal gaskets (such as 316 stainless steel wrapped gaskets) or fluororubber O-rings are used to ensure high pressure resistance and corrosion resistance at the connection with the pipeline;
2. Electronic cavity sealing: A high elasticity fluorosilicone sealing ring is used between the housing and the cover plate, and is uniformly tightened with bolts to achieve IP66/IP67 or even IP68 protection levels;
3. Electrical lead sealing: The cable entrance is equipped with an explosion-proof gland (Ex d certified), which is internally sealed with epoxy resin or silicone to block flammable gases from entering the cavity along the cable.
2、 Material compatibility determines lifespan
The transmitter diaphragm and seal must be highly compatible with the measured medium. For example, in oil and gas environments containing hydrogen sulfide (H ₂ S), the diaphragm is often made of Hastelloy C-276 or tantalum material; The sealing ring is preferably made of perfluoroether rubber (FFKM), which can withstand temperatures up to 300 ℃ and has excellent resistance to strong acids and solvents, significantly extending its service life.
3、 Welding and potting processes enhance reliability
Explosion proof transmitters commonly use laser welding instead of traditional threaded connections to eliminate potential leakage points. At the same time, the circuit board is treated with three anti paints (moisture-proof, anti mold, anti salt spray) and then fully sealed to effectively isolate moisture and corrosive gases from entering, avoiding performance drift caused by condensation or electrochemical corrosion.
4、 Long term stability verification mechanism
Manufacturers typically verify product stability through accelerated aging tests (such as high-temperature and high humidity cycling, pressure shock testing) and long-term drift tests (such as 1000 hours of full-scale operation). Users should also regularly perform zero point calibration and sealing checks during use, especially under frequent start stop or severe temperature fluctuations.
In summary, the sealing structure of explosion-proof pressure transmitters is not only a physical barrier, but also a core component of functional safety. Only through scientific material selection, precision manufacturing, and standardized maintenance can we truly achieve the industrial goal of "accurate measurement, long-lasting use, and safety".