Explosion Proof Solenoid Valve — NC, SS304, Viton, Ex mb II T4 Gb Certified

Cematic's explosion-proof solenoid valve is a fluid control component certified for installation in areas with potentially explosive atmospheres — classified as Zone 1 and Zone 2 according to IEC 60079 / NOM-022. Its Ex mb II T4 Gb / Ex mbD 21 IP65 T130 °C certification ensures that the solenoid coil is encapsulated in such a way that no internal electrical arc can ignite an external explosive atmosphere, complying with electrical safety requirements in hazardous areas of the chemical, petrochemical, gas, and mining industries.

Unlike standard solenoids with conventional IP65 protection, this solenoid valve is specifically designed and certified for environments where the presence of flammable gases, vapors, or combustible dusts makes any electrical ignition source an explosion risk. Therefore, its selection is not a specification preference — it is a safety and regulatory requirement in the industries where it applies.

Ex Certification — what it means and why it matters

The designation Ex mb II T4 Gb precisely describes the safe operating conditions of this solenoid valve:

• Ex: Equipment certified for use in explosive atmospheres according to IEC/ATEX regulations.
• mb: Protection method by encapsulation — the coil and electrical components are embedded in high-resistance epoxy resin that prevents contact between live electrical parts and the explosive atmosphere, even in the event of an internal failure.
• II: Equipment group for surface industries (general industry, excluding gassy mines).
• T4: Temperature class — the maximum surface temperature of the equipment does not exceed 135 °C, making it safe in gas atmospheres with an ignition temperature above 135 °C (most common industrial gases).
• Gb: Equipment Protection Level (EPL) for Zone 1 — high protection level, suitable for atmospheres where the presence of gas is likely under normal operating conditions.
• Ex mbD 21 IP65 T130 °C: Additional certification for combustible dust atmospheres (Zone 21), with a maximum surface temperature of 130 °C and IP65 protection against dust and water.

Operating principle — Normally Closed (NC)

In the de-energized state: the valve remains closed — the spring keeps the plunger on the seat, blocking fluid flow. When the coil is energized, the electromagnetic field lifts the plunger, opening the flow. When de-energized, the spring automatically returns the plunger to the closed position.

The NC configuration is standard in ATEX zones for a fundamental safety reason: in the event of any electrical failure in the control system — including those caused by an explosion event — the valve automatically closes, cutting off the flow of hazardous fluid. Consequently, NC closure is the intrinsic safety state of the process in most applications with flammable or toxic fluids.

Construction materials

• Body: Stainless steel 304 (SS304) — corrosion resistance for industrial, chemical, and aggressive process fluids. Compatible with most fluids present in ATEX zones in the chemical and petrochemical industry.
• Plunger: Stainless steel — resistant to corrosion by process fluid.
• Seat Seal: Viton (FKM) — compatible with industrial gases, hydrocarbon vapors, solvents, and aggressive chemical fluids present in classified zones. Significantly superior chemical resistance to NBR for typical ATEX zone fluids.
• Coil: Encapsulated in high-resistance epoxy resin — "mb" protection method that prevents any external electrical arc. IP65 protection against dust and water.
• Connection: Female NPT thread — industrial standard in Mexico and America, compatible with stainless steel and carbon steel piping.

Technical specifications

Installation zones — when is an Ex solenoid required?

The zone classification according to IEC 60079-10 / NOM-022-STPS defines which electrical equipment can be installed in each area. Therefore, it is the starting point for correctly selecting this valve:

• Zone 0: Explosive atmosphere present continuously. Conventional solenoids do not apply — requires equipment with intrinsic protection "ia".
• Zone 1 (this product applies ✅): Explosive atmosphere likely under normal operating conditions. This Ex mb II T4 Gb solenoid is certified for Zone 1.
• Zone 2 (this product applies ✅): Explosive atmosphere unlikely under normal conditions but possible under abnormal conditions. This solenoid is also suitable for Zone 2.
• Zone 21 (this product applies ✅): Combustible dust likely present under normal conditions. Ex mbD 21 IP65 T130 °C certification.

Fluid compatibility in classified zones

• ✅ Natural gas and LPG — flow control in gas lines in classified zones
• ✅ Hydrocarbon vapors — benzene, toluene, hexane and derivatives in refining and petrochemicals
• ✅ Industrial solvents — alcohols, ketones, esters compatible with Viton and SS304
• ✅ Process water and aqueous solutions — in classified zones due to the presence of flammable vapors
• ✅ Compressed air up to 1.0 MPa — instrumentation and pneumatic control in ATEX zones
• ✅ Hydraulic oils and fuels — compatible with Viton seal
• ⚠️ Gases with ignition temperature below 135 °C: verify temperature class T4 vs. the specific process gas before installation
• ❌ Concentrated acids and halogenated solvents: verify chemical compatibility of SS304 and Viton with Cematic technical team

Main industrial applications

Petrochemical and refining industry
In refineries and petrochemical plants, controlling flammable fluids — crude oil, naphtha, LPG, natural gas — in Zone 1 and Zone 2 requires Ex-certified electrical equipment. This explosion-proof solenoid valve controls the flow of these fluids with automatic shutdown in case of electrical failure (NC), ensuring that no failure in the control system generates an ignition source in the classified zone. Therefore, it is the standard component in automatic process control systems in ATEX areas of refineries.

Chemical industry — control of flammable solvents and reagents
In chemical production plants where organic solvents, alcohols, ketones, and other flammable liquids are handled, the installation of standard solenoids in classified zones is prohibited by regulation. Consequently, this Ex solenoid valve allows automation of dosing and cut-off control of flammable reagents, complying with the safety requirements of NOM-022-STPS and applicable IEC/ATEX standards.

Storage and distribution of natural gas and LPG
In natural gas and LPG storage, loading, and distribution facilities, the areas around valves, flanges, and process equipment are classified as Zone 1 or Zone 2. Additionally, this Ex solenoid controls gas flow with automatic safety shutdown, being compatible with the Safety Instrumented Systems required in these facilities.

Mining and handling of combustible dusts
In facilities where combustible dusts — coal, aluminum, flour, sugar — are handled, classified as Zone 21, the Ex mbD 21 IP65 T130 °C certification of this solenoid valve enables its direct installation in risk areas, without the need for purge boxes or additional protective equipment.

Industrial water and wastewater treatment with classified zones
In industrial wastewater treatment plants where biogas (methane) and other flammable gases are generated, the areas around digesters and lagoons are classified as hazardous areas. Likewise, this Ex solenoid controls the flow of water and process gases, complying with the electrical safety requirements of the classified zones of the facility.

For the complete range of industrial solenoid valves, see solenoid valves collection →

Technical Data Sheet