Explosion-Proof Ball Valve with Fail-Safe Actuator — Spring Return, IP68, ATEX / IECEx / CSA, 50 to 260 NM

The Cematic explosion-proof fail-safe ball valve with actuator is the standard assembly for automated and safe fluid shut-off in industrial classified areas with the presence of combustible gases, vapors, or dusts. Its spring return actuator ensures that, in the event of a power supply loss, the valve moves to the predefined safe position.

It does not require a battery, capacitor, or auxiliary power source. The spring mechanism permanently stores mechanical energy, which means the fail-safe response is instantaneous and reliable at all times. It is certified under ATEX, IECEx, and CSA, as it complies with international standards for installation in zones 1, 2, 21, and 22.

Cematic delivers the valve + actuator assembly pre-assembled, calibrated, and tested, making it ready for installation.

Spring Return Mechanism — Why It's More Reliable Than Battery or Capacitor

The spring return actuator uses a rack-and-pinion mechanism to convert the energy stored in the spring into rotational valve movement. The reasons why this mechanism is the standard in functional safety are described below:

• No degradation over time: The spring stores mechanical energy permanently without losing capacity. Batteries and supercapacitors, however, degrade with charge cycles and temperature. Therefore, they require periodic replacement to ensure the safety function.
• Instantaneous response: When the power supply is cut, the spring acts immediately. Consequently, there is no activation time or prior charge verification. As a result, the closing time in an emergency is predictable and constant throughout the actuator's lifespan.
• Mechanical damper in On-Off version: The On-Off version includes a mechanical damper at the end of the spring's travel. This reduces water hammer in the piping caused by the rapid closing of the spring. Therefore, it reduces water hammer in the piping caused by the rapid closing of the spring, protecting downstream piping and equipment.
• Configurable fail direction: The return direction — close or open on power failure — is configured at the time of order based on the process's safe state. However, it is not modifiable after manufacturing, so it must be correctly specified when ordering.

Classified Zones Where This Assembly Is Required by Standard

International standards classify industrial environments according to the risk of explosive atmospheres. This assembly is certified for the following zones:

• Zone 1 and Zone 2 — gases and vapors (Groups IIA and IIB): Zones with occasional or unlikely presence of an explosive gas or vapor atmosphere. ATEX/IECEx certification covers gases in Groups IIA and IIB — including most industrial hydrocarbons — making it the standard assembly in refining and petrochemical processing. Therefore, it is the standard assembly in refining, gas plants, and petrochemical processes.
• Zone 21 and Zone 22 — combustible dusts: Zones with the presence of suspended combustible dusts. The Ex tb IIIC T130°C Db certification also covers dusts from Group IIIC. The Ex tb IIIC T130°C Db certification also covers dusts from Group IIIC — the most conductive and with the lowest ignition temperature. Therefore, it is the correct actuator in coal, flour, sugar plants, and other combustible dust applications.

Control Modes Available in Addition to the Standard Spring Return

The actuator is available in three control modes according to process requirements. In all cases, the spring return acts automatically upon a power supply cut:

• On-Off (standard): Two positions — open or closed — from an electrical signal. It is also the standard mode included in the assembly. The mechanical damper also reduces the impact of spring closure on the piping. Therefore, it is the most specified configuration in emergency shutdown and isolation systems in hazardous areas.
• Floating (option): Allows positioning the valve at any intermediate point using open, close, or stop signals. However, in the event of a power supply cut, the spring returns the valve to the predefined safe position. However, in the event of a power supply cut, the spring returns the valve to the predefined safe position. This is the correct option when intermediate positioning is required in addition to fail-safe closing.
• Modulating (option): Offers proportional control via a 4-20 mA signal for continuous flow regulation in PID loops. In the event of a power loss, the spring return also acts. In the event of a power loss, the spring return also acts. Therefore, it is the correct option in control loops for hazardous areas where fail-safe closing is a simultaneous safety requirement to proportional control.

Torque Selection: Models Available According to Valve Diameter

The actuator's torque must exceed the valve's operating torque at maximum working pressure. The available models in the series are described below:

• SE-500 — 50 NM: For small diameter ball and butterfly valves in classified areas. It is the most compact model in the series, as it has the lowest weight and dimensions.
• SE-1300 — 130 NM: For intermediate diameter valves or valves requiring higher torque due to elevated pressure. Likewise, it is the standard model for most 2" to 4" ball valves in classified areas. Likewise, it is the standard model for most 2" to 4" ball valves in classified industrial services.
• SE-2000 — 200 NM: For 4" to 8" butterfly valves or larger diameter ball valves. Therefore, it covers applications where the SE-1300 does not provide the required torque. Therefore, it covers larger diameter applications in industrial processes where the SE-1300's torque is insufficient.
• SE-2600 — 260 NM: The highest torque model in the series. Therefore, it is the option for large diameter valves or high differential pressure services. Therefore, it is the option for large diameter valves or high differential pressure services where previous models do not provide the required torque.

Materials and Technical Specifications Ensuring Performance in Hazardous Areas

The actuator cover is made of aluminum alloy with a dry powder coating, standard for explosion-proof actuators. The spring mechanism is rack-and-pinion, as it efficiently converts stored energy into 90° rotational motion. The motor also includes integrated thermal protection and Class F insulation. Finally, the ISO5211 mounting ensures compatibility with the valve without adapters.

Hazardous Area Certifications

Applications of the Explosion-Proof Fail-Safe Actuator Valve

Petrochemical and Refining Industry with Classified Areas

The explosion-proof fail-safe actuator valve is the standard component in hydrocarbon lines for refining and petrochemical processes. The spring return also ensures emergency shut-off without auxiliary power in the event of any power supply failure.

Therefore, it simultaneously meets the requirements of functional safety and hazardous area classification in a single unit.

Natural Gas and LPG Plants Where Fail-Safe Closing Is a Regulatory Requirement

In natural gas, LPG, and biogas installations, this assembly controls shut-off valves in zones 1 and 2 with Group IIB gases. Consequently, it is the preferred solution in gas distribution and storage stations. The ATEX/IECEx/CSA certifications also directly enable it for these zones without additional safety barriers in the control signal.

Consequently, it is the preferred solution in compression, distribution, and gas storage stations where automatic emergency shutdown is a regulatory requirement.

Chemical Industry with Flammable Fluids

In plants with toxic or flammable fluids, the combination of fail-safe closing and explosion-proof protection ensures safety in the event of any electrical failure. The stainless steel ball valve body also offers adequate chemical resistance for the most common fluids in chemical processes.

Therefore, it is the correct assembly when the process simultaneously demands corrosion resistance and an actuator certified for hazardous areas.

Mining and Processes with Combustible Dusts certified for Zone 21 and 22

The Ex tb IIIC T130°C Db certification enables this actuator for zones 21 and 22 with combustible dusts. Therefore, it is the suitable assembly in coal, flour, sugar, and metallic dust plants where dust protection is a regulatory requirement.

The automatic spring closure also acts without operator intervention even in widespread emergency situations.

Dosing and Emergency Shut-off Systems

In dosing systems for hazardous products in classified areas, this assembly ensures immediate shut-off in the event of any control system failure. The mechanical damper included in the On-Off version also protects the piping from water hammer caused by the rapid closing of the spring.

Consequently, it is the most complete solution for emergency shut-off systems in processes with hazardous fluids in classified atmospheres.

For the complete range of explosion-proof actuators, see Ex-Proof Actuators collection →