E+H Prosonic S FDU91F Hazardous Area Ultrasonic Level Sensor

Reliable Non-Contact Level Measurement in Hazardous Areas

Maintaining accurate continuous level monitoring in chemical processing plants, fuel storage terminals, and industrial explosive atmospheres requires specialized instrumentation designed for safety compliance and operational reliability. The Endress+Hauser Prosonic S FDU91F Ultrasonic Level Sensor provides a proven, non-contact measurement solution utilizing time-of-flight acoustic wave technology certified for hazardous classified locations. By emitting ultrasonic pulses toward the process media surface, the FDU91F measures fluid levels and bulk solids continuously without physical media contact, eliminating issues caused by corrosion, sticky buildup, or mechanical wear.

Explosion-Protected Design & Integrated Temperature Compensation

Outdoor chemical basins and fuel tank farms are frequently exposed to hazardous explosive gases, volatile vapors, and fluctuating ambient temperatures. The Prosonic S FDU91F addresses these demands by combining full international explosion-proof approvals (such as ATEX, IECEx, and FM/CSA Div 1) with an integrated temperature sensor directly inside the sensor head.

This sensor continuously monitors ambient air temperatures, allowing connected transmitters (such as the Prosonic S FMU90 or FMU95) to automatically compensate for changes in the speed of sound through air. Furthermore, an optional integrated sensor heater prevents frost, ice buildup, and condensation on the acoustic membrane, ensuring uninterrupted measurement accuracy during extreme weather cycles.

Submerged Protection & Self-Cleaning Acoustic Membrane

Engineered to withstand tough environmental conditions and accidental submersion in hazardous pits, the FDU91F sensor features a hermetically sealed, fully potted housing rated to IP68 (NEMA 6P). The acoustic sensor face utilizes a flexible, self-cleaning membrane made from PVDF or UP-sheet materials, which reduces dust and condensation accumulation in dirty industrial atmospheres.

The non-intrusive sensor probe connects via a shielded 2-wire coaxial cable up to 300 meters (1,000 feet) away from the control transmitter, isolating sensitive display and controller electronics in safe, easy-to-access control rooms.

Flexible Automation System Integration

When combined with the Endress+Hauser Prosonic S FMU90 Ex-certified transmitter, the FDU91F supports a broad range of open-channel flow measurement flumes and weirs. It offers sophisticated echo signal evaluation algorithms that suppress false fixed reflections caused by internal structural obstructions, agitator blades, or basin walls.

Output signal options provided through the paired transmitter include 4 to 20 mA HART, PROFIBUS DP, and Modbus RS485 for seamless integration into supervisory PLC, SCADA, or DCS architectures.

 Applications

• Chemical & Petrochemical Plants: Continuous level monitoring in hazardous chemical storage tanks, reactor feed basins, and neutralizer pits.

• Fuel & Oil Terminals: Level tracking in day tanks, fuel oil storage vessels, and oily water separators located in classified zones.

• Wastewater & Effluent Treatment: Continuous level monitoring in industrial intake screens, equalization basins, and sludge holding tanks in classified areas.

• Open Channel Flow Measurement: Volumetric flow calculation in chemical plant discharge flumes and industrial effluent channels.

• Bulk Solids Storage: Level tracking in short silos and powder hoppers within hazardous dust environments (Zone 21/22).

Technical Specifications

• Manufacturer / Brand: Endress+Hauser (E+H)

• Measurement Principle: Non-contact ultrasonic time-of-flight measurement.

• Operating Frequency: ~43 kHz.

• Max. Measuring Range: Liquids: Up to 20 meters (65 ft); Bulk Solids: Up to 10 meters (33 ft).

• Blocking Distance: 0.3 meters (1 ft).

• Process Temperature Range: -40 °C to +95 °C (-40 °F to +203 °F).

• Process Pressure Range: 0.7 to 4 bar abs (10 to 58 psi abs).

• Sensor Membrane Material: PVDF or UP-sheet (unsaturated polyester).

• Ingress Protection Class: IP68 / NEMA 6P (submersion proof).

• Temperature Compensation: Integrated internal temperature sensor; optional integrated heater.

• Cable Connection: Shielded coaxial cable (up to 300 m / 1,000 ft distance to transmitter).

• Compatible Transmitters: Prosonic S FMU90 (Ex-version), Prosonic S FMU95.

• Hazardous Area Approvals: ATEX II 2G Ex db [ia] IIC T6…T4 Gb, ATEX II 2D Ex tb [ia] IIIC Txx°Db, IECEx, FM / CSA Div 1.

FAQ

Q1: Is the Endress+Hauser Prosonic S FDU91F supplied as an authentic original unit? A: Yes. We supply 100% genuine, brand-new Endress+Hauser instruments complete with original factory serial numbers, calibration reports, and official documentation.

Q2: What is the main difference between the FDU91 and the FDU91F models? A: The FDU91F model is specifically engineered with rigorous explosion protection approvals (Ex-certified for Zone 1 / Division 1 hazardous areas), making it suitable for explosive chemical and fuel environments where standard sensors cannot be used.

Q3: Can the FDU91F sensor operate independently without a separate transmitter? A: No. The FDU91F is an ultrasonic sensor probe designed to operate in combination with an external Ex-certified transmitter controller, such as the Endress+Hauser Prosonic S FMU90.

Q4: How can I request distributor quotes and confirm delivery lead times? A: Simply submit your required E+H model ordering code, Ex-approval requirement, cable length, and measuring range through our inquiry form. Our sales team will provide a prompt, competitive quotation and export delivery timeline.

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