Electric valves in chemical plants may be exposed to flammable gases, combustible dust, rain, high humidity, and daily temperature changes at the same installation point. Under these conditions, actuator selection cannot be based on output torque alone. Engineers must also verify the explosion-protection marking, ingress-protection rating, ambient temperature range, control signal, and cable entry.
An IP68 explosion-proof electric actuator can provide a suitable foundation for valve automation in demanding chemical environments. However, suitability must always be confirmed against the hazardous-area classification and the certification scope of the selected model.
An IP68 rating describes the enclosure’s protection against dust and water ingress. It does not replace an explosion-proof certification. For chemical plant applications, engineers should separately determine whether:
- The ingress-protection rating matches the site’s dust, rain, and washdown exposure.
- The explosion-proof marking covers the applicable gas or dust group.
- The temperature class is suitable for the process and ambient conditions.
- The certification applies to the specific actuator model and installation area.
The DCL-Ex product literature specifies IP68 protection. Its listed markings include Ex db h IIC T4 Gb for gas atmospheres and Ex h tb IIIC T135°C Db for dust environments. For North American projects, the literature also identifies Class I, Division 1, Groups C and D, T5/T6 and a Class I, Zone 1 classification.
These ratings provide a basis for preliminary selection. Final approval should follow the project’s electrical code, area-classification documents, actuator nameplate, and applicable certificate.
The DCL-Ex explosion-proof electric actuator range provides standard output torque from 50 to 3,000 Nm. The series is intended for ball valves, butterfly valves, plug valves, and other rotary valves, with adjustable 0–90° travel on most models and 0–360° travel on selected configurations.
Nominal valve diameter alone is not sufficient for sizing. Required torque can change with:
- Process pressure and differential pressure.
- Fluid viscosity or suspended solids.
- Seat and sealing materials.
- Pipeline temperature.
- Breakaway torque after extended shutdown.
- Valve stem and mounting-interface dimensions.
The product literature recommends allowing approximately 1.1–1.3 times the valve’s tested torque when selecting an actuator. This factor should be applied together with torque data supplied by the valve manufacturer, rather than treated as a universal rule for every chemical process.
An IP68 enclosure helps limit external water and dust ingress, but temperature cycling can still create condensation inside an actuator. An optional dehumidifying heater should therefore be considered for outdoor chemical plants, high-humidity locations, and installations with large day-to-night temperature differences.
Optional over-torque protection can disconnect the actuator circuit when debris or valve jamming causes torque to reach a preset limit. This helps reduce the risk of damage to both the valve and actuator. An optional fail-safe system uses a supercapacitor or battery to move the valve to a preset fully open, fully closed, or retained position after an abnormal power loss.
An on-off explosion-proof actuator is suitable for isolation duties. Processes requiring continuous regulation of flow, pressure, temperature, or liquid level can use a modulating electric actuator with 4–20 mA, 1–5 V, or 2–10 V input.
DCL-Ex modulating models provide 4–20 mA position feedback. The literature specifies a basic error of no more than ±1%, with reciprocating and actuator repeat errors no greater than 1%.
For chemical plants combining moisture exposure with explosive gases, a practical selection sequence is to verify the hazardous-area classification first, confirm IP protection and ambient temperature next, and then match the actuator’s torque, control mode, power supply, and mounting interface to the valve.