Level Measurement in High-Temperature Bulk Solids Silos: FMR57 Non-Contact Radar Solution for Processes up to 400°C

Industry Pain Point: The Challenge of Level Measurement under High-Temperature Conditions

In the cement, steel, power generation, and chemical industries, level measurement of high-temperature powdered or granular bulk solids has long been a technical challenge. When internal silo temperatures exceed 200°C—or reach as high as 400°C—traditional contact-type level sensors (such as plumb-bob, capacitive, or vibrating fork types) often suffer from probe burnout, mechanical jamming, or signal drift.

Root causes include:

• Elevated temperatures shorten electronic component lifespan and degrade measurement stability

• Heavy dust-laden environments attenuate radar signals, causing echo loss

• Loose product surfaces (particularly under pneumatic conveying) generate irregular reflections, interfering with true level identification

For process engineers and instrument specifiers, selecting a level transmitter that maintains long-term reliability under the dual constraints of high temperature and heavy dust is a frequent and mission-critical decision.

Solution Approach: Non-Contact Radar Based on Time-of-Flight Principle

The Micropilot FMR57 operates on the Time-of-Flight (ToF) measurement principle: radar pulses are emitted by the antenna, reflected off the product surface, and received back by the same system. The distance D to the product surface is proportional to the pulse flight time t (D = c·t/2), and the level L is calculated from the known empty distance E: L = E − D.

The key advantages of this non-contact approach:

• No moving parts eliminates high-temperature wear and mechanical failure

• Measurement is unaffected by media density, temperature layers, or gas-phase composition changes

• Suitable for a wide range of bulk solids—from powders to granules (dielectric constant εr > 1.6)

Parameterized Evidence: Why FMR57 Handles +400°C Duty

Four critical specifications collectively establish the reliability foundation for high-temperature applications:

Interference Rejection: The Engineering Value of Multi-Echo Tracking

In high-temperature powder silos, sources of interference echoes are complex: internal struts, weld seams, material build-up, and filling noise all generate false signals. FMR57 integrates Multi-Echo Tracking algorithms, built on over 30 years of time-of-flight experience, to ensure measurement reliability through the following mechanisms:

1. Short-term and long-term echo history comparison: validates the plausibility of every detected signal

2. Active interference echo suppression: users can activate electronic interference echo suppression, which, combined with the algorithm, excludes reflections from obstacles in level determination

3. Self-learning echo search: the device records a reference echo curve during commissioning and uses it as a baseline to identify anomalies during operation

For applications with heavy dust emissions or risk of antenna build-up, the FMR57 also features an integrated purge-air connection. Pulse or continuous purging keeps the antenna clean, preventing signal attenuation.

Selection Guidelines and Key Considerations

When specifying FMR57 for high-temperature powder silos, prioritize the following three aspects:

1. Seal Selection (Feature 090)

• Standard high-temperature duty (≤200°C): Viton GLT seal

• Extreme high-temperature duty (≤400°C): Graphite seal (mandatory)

2. Antenna Type and Installation Clearance

• Slim silos or small nozzle diameters: prioritize parabolic antenna (200 mm / 250 mm) with beam angles of only 3.5°–4°—highly focused energy and superior interference rejection

• Standard installation spaces: horn antenna (80 mm / 100 mm, beam angles 8°–10°) are adequate

3. Explosion Protection and Functional Safety

• FMR57 carries ATEX, IECEx, FM, CSA, NEPSI, and other international explosion protection certifications

• Single device meets SIL2 functional safety requirements; homogeneous redundancy can achieve SIL3

• For WHG (German Water Resources Act) compliance, the device holds the relevant approvals

Conclusion

Level measurement in high-temperature bulk solids silos does not have to mean frequent maintenance or unreliable data. With a 70 m range, –1 to 16 bar pressure rating, –40 to +400°C temperature capability, and ±3 mm accuracy—complemented by Multi-Echo Tracking interference rejection—the FMR57 delivers a parametrically verified radar measurement solution for high-temperature, high-dust duties. By focusing on three key configuration choices—seal material, antenna type, and functional safety level—engineers can achieve stable, continuous level monitoring across the majority of high silo, coal bunker, and stockpile applications.

This article is based on the Endress+Hauser Micropilot FMR57 Technical Information (TI01042FEN) and publicly available technical data from authorized distributors. Final selection should always reference the latest official specifications and be validated against actual process conditions.