Why must explosion-proof solenoid valves be equipped with dedicated explosion-proof coils?
Publish Time: 2025-11-04
In petrochemical, natural gas transportation, coal mining, pharmaceutical workshops, and dusty industrial environments, flammable and explosive gases, vapors, or dust may be present in the air, either continuously or intermittently. In such hazardous locations, any tiny electrical spark, high-temperature surface, or even electrostatic discharge can become an ignition source, triggering a catastrophic explosion. As a key actuator in automated control systems, the solenoid valve's core—the electromagnetic coil—inevitably involves current changes, magnetic field establishment, and energy conversion during energization and de-energization.When a conventional solenoid coil is in operation, the internal coil windings are energized to generate a magnetic field, driving the valve core. However, at the moment of switching, especially when power is cut off, the inductive element generates an induced electromotive force, which may trigger an arc or spark. Simultaneously, the coil heats up during prolonged operation; if heat dissipation is poor or the load is abnormal, the surface temperature may rise to dangerous levels. In ordinary industrial environments, these phenomena are usually harmless; however, in explosive atmospheres, they are sufficient to act as a "trigger." Dedicated explosion-proof coils are designed to completely eliminate these risks.The core of an explosion-proof coil lies in "limiting energy release" and "isolating potential ignition sources." Its internal structure is specially optimized, using high-insulation-grade encapsulation materials to completely seal the windings, preventing internal arcs or sparks from leaking into the surrounding environment. Simultaneously, through precise electromagnetic design and thermal management, it ensures that under rated operating conditions and even certain overload conditions, the surface temperature of the coil casing remains below the minimum ignition temperature of flammable substances in the environment. This temperature rise control does not rely on external cooling but rather limits heat generation at the source and enhances the heat dissipation path, achieving intrinsic safety.Furthermore, explosion-proof coils typically integrate multiple protection mechanisms. For example, they use flame-retardant, high-temperature-resistant epoxy resin or polyurethane for integral potting, which not only improves mechanical strength and moisture resistance but also effectively suppresses internal partial discharge. Some designs also incorporate temperature-sensitive elements that automatically cut off power in case of abnormal temperature rise. The casing material is also rigorously selected, possessing impact resistance and corrosion resistance, and meets international explosion-proof standards through special structural designs (such as explosion-proof gaps or increased safety measures).More importantly, dedicated explosion-proof coils must be certified by authoritative bodies such as ATEX, IECEx, NEC, or the Chinese Explosion-Proof Certificate. These certifications not only verify safety in simulated hazardous environments in laboratories but also cover long-term operational stability, environmental adaptability, and failure mode analysis. This means that each explosion-proof coil undergoes systematic safety verification, rather than being a simple "enhanced" version of an ordinary coil.If an ordinary coil is used on an explosion-proof solenoid valve without authorization, even if the valve body itself has an explosion-proof structure, the explosion-proof integrity of the entire system will be compromised. This is because the coil, as the energy input, is a potential source of ignition risk. Safety regulations clearly require that all live parts of explosion-proof equipment must be certified as a whole; any uncertified replacement will lead to compliance failure and may result in legal liability in accident investigations.In conclusion, equipping explosion-proof solenoid valves with dedicated explosion-proof coils is a necessary requirement of industrial safety logic. It is not a functional addition but a risk closure loop; not an increase in cost but a manifestation of responsibility. In those dangerous spaces where flames are unseen yet ignite potential, a small explosion-proof coil, with its silent sealing and precise temperature control, builds an invisible yet crucial safety barrier. It protects not only the normal operation of equipment, but also the lives of countless workers and the stability of the entire production system.
