Choosing the right explosion-proof ultrasonic flow meter is not only about measurement accuracy but also about ensuring personnel and equipment safety in hazardous environments. This guide breaks down the essential concepts, certifications, and selection steps to help you make the best purchase decision.

What Does “Explosion-Proof” Mean?

Explosion protection ensures that a device will not ignite explosive gases or dust through sparks or high surface temperatures. In flow meters, this is critical for industries such as oil & gas, chemical, and mining where hazardous atmospheres are common.

Key Certifications to Check

Before purchasing, always verify if the flow meter has the correct explosion-proof certifications for your market:

  • China: Ex certification (e.g., Ex d IIC T6 Gb) issued by NEPSI.
  • Europe: ATEX certification.
  • International: IECEx certification.
  • North America: UL and cUL for Class I, Division 1/2 hazardous areas.

⚠️ If a flow meter lacks proper certification, it should never be used in hazardous zones.

Five-Step Selection Guide

1. Define Application and Fluid Properties

  • Medium type: Liquid, gas, or steam.
    • Clean liquids → Transit-time method.
    • Slurries or bubble-rich liquids → Doppler method.
  • Fluid properties: Temperature, pressure, viscosity, corrosion.
  • Flow range: Ensure meter range covers minimum, normal, and maximum flows.

👉 Learn more about ultrasonic flow meters

2. Confirm Explosion-Proof Level and Zone Classification

Work with safety engineers to identify the correct zone classification:

  • Zone 0: Continuous explosive atmosphere (intrinsically safe only).
  • Zone 1: Explosive atmosphere likely during normal operation.
  • Zone 2: Explosive atmosphere rare and short-lived.

Gas groups: IIC > IIB > IIA (higher class covers lower).
Temperature class: T1–T6 (T6 = ≤85°C, safest).

👉 Example: If your site uses hydrogen (IIC, Zone 1), your flow meter must be rated Ex d IIC T6 Gb or higher.

3. Select the Right Explosion-Proof Type

  • Flameproof / Explosion-proof enclosure (Ex d):
    • Sealed housing prevents external ignition.
    • Suitable for Zone 1, Zone 2.
  • Intrinsically Safe (Ex ia / Ex ib):
    • Limits circuit energy, safe for Zone 0.
    • Often used for sensors.
  • Pressurized enclosure (Ex p):
    • Maintains positive pressure with clean gas.
    • Less common for flow meters.

💡 Best practice: Use Ex d transmitter + Ex ia sensor for maximum safety.

4. Check Performance and Installation Details

  • Accuracy: ±1% or better (±0.5% for high-precision).
  • Installation types:
    • Clamp-on: Non-intrusive, easy install, lower accuracy.
    • Insertion: Higher accuracy, can be serviced under pressure.
    • Inline (spool-piece): Highest accuracy, requires pipeline cut.
  • Integration: Verify compatibility with power supply (AC/DC), signals (4-20mA, pulse), and communication protocols (HART, Modbus, PROFIBUS).

5. Evaluate Supplier and After-Sales Support

  • Technical expertise: Does the supplier provide engineering support?
  • Documentation: Ensure full certification, test reports, manuals.
  • Service: Availability of calibration, on-site support, and quick replacements.

Quick Checklist Before Purchase

✅ Explosion-proof certification (Ex/ATEX/IECEx/UL)
✅ Correct zone and gas/temperature group rating
✅ Suitable explosion-proof type (Ex d, Ex ia, Ex p)
✅ Fluid compatibility and measurement method
✅ Proper installation style (clamp-on, insertion, inline)
✅ Accuracy and flow range requirements
✅ Compatible outputs and communication
✅ Reliable supplier with after-sales service

Conclusion

An explosion-proof ultrasonic flow meter combines safety, accuracy, and reliability in hazardous environments. By following the five-step selection method—defining application, confirming safety level, choosing explosion-proof type, checking performance, and vetting suppliers—you can avoid costly mistakes and ensure safe, precise flow measurement.

When safety is critical, never compromise on certification or supplier quality. The right investment in explosion-proof technology guarantees both accurate process control and long-term operational safety.

Any questions? Consult us, and the Aister professional team will solve your problems.