Endress+Hauser Levelflex FMP51: Guided Wave Radar for Demanding Level and Interface Measurement

FMP51 is not a single fixed instrument. Probe design, length, process connection, wetted materials, housing, output, approvals and optional features are determined by the complete order code. A correct selection therefore begins with the process and vessel—not only the model name.

How the Levelflex FMP51 Works

Levelflex FMP51 uses guided wave radar, also called time-of-flight measurement. Radar pulses travel along a rod, rope or coaxial probe. When the pulses reach the product surface or an interface between two liquids, part of the signal is reflected to the transmitter. The measured travel time is converted into level.

Guiding the signal along a probe provides a defined measurement path. Endress+Hauser positions the FMP51 for reliable operation when the product surface is moving, foam is present or tank baffles complicate the vessel geometry. Changing media, temperature, gas blankets and vapor do not directly alter the radar travel-time principle.

FMP51 Key Specifications

Specifications depend on the selected product configuration and may be revised by the manufacturer. Always verify the complete order code and current technical documentation before purchase.

Where Is the FMP51 Commonly Used?

The Levelflex FMP51 is designed for demanding process-industry applications such as:

• Process and storage vessels with high temperature or pressure
• Liquids with moving surfaces, foam, vapor or gas blankets
• Tanks containing baffles, heating coils or other internal structures
• Continuous level measurement of liquids, pastes and slurries
• Interface measurement between two liquid phases
• Chemical, oil and gas, power, water and general process-industry duties

Actual suitability depends on chemical compatibility, probe construction, process limits, dielectric properties, approvals and installation conditions.

Rod, Rope or Coaxial Probe?

Rod probe

The rigid rod probe is suitable for measuring ranges up to 10 m. It can be a practical choice for smaller and medium-height vessels when sufficient installation clearance is available.

Rope probe

The rope probe extends the maximum published measuring range to 45 m, depending on dielectric constant. It is well suited to tall vessels, but the installation must account for probe movement, inlet flow, agitation and any anchoring requirement.

Coaxial probe

The coaxial design guides the signal inside an outer tube and supports measuring ranges up to 6 m. With a published minimum dielectric constant above 1.4, it can be useful for low-dielectric media and controlled measurement geometries. Process cleanliness, viscosity, coating and solids must still be considered.

FMP51 Level and Interface Measurement

For standard level measurement, the instrument evaluates the reflection from the upper product surface. In a suitable two-liquid application, the FMP51 can also determine the interface between an upper and lower liquid layer.

Interface measurement is application-dependent. The upper phase must allow sufficient signal transmission, and emulsion layers, dielectric contrast, coating and vessel conditions can influence performance. Provide both liquid properties, expected layer thicknesses and process conditions when requesting a configuration.

FMP50 vs FMP51: What Changes?

The comparison is a starting point only. Material compatibility, approvals and the complete product configuration remain essential.

Information Required for Correct FMP51 Selection

Before requesting a quotation, collect the following information:

1. Medium: product name, dielectric constant, density, conductivity and tendency to foam or build up.
2. Process conditions: normal and maximum temperature and pressure.
3. Vessel: total height, measuring range, nozzle dimensions and internal structures.
4. Probe: rod, rope or coaxial, required length and any anchoring requirement.
5. Measurement task: overall level, interface level or both.
6. Connection and materials: thread or flange and compatible wetted materials.
7. Electrical interface: required power supply, output and communication protocol.
8. Approvals: hazardous-area, overfill-prevention, SIL or project-specific certificates.
9. Existing unit: complete order code, serial number and nameplate photo for replacement projects.

Why the Complete FMP51 Order Code Matters

FMP51 identifies the product family, but it does not define the complete instrument. Probe type and length, process connection, wetted materials, housing, electrical output, display, approvals and additional options are encoded in the full model number.

For replacement projects, send the complete code exactly as shown on the nameplate—for example, a code beginning with FMP51-...—along with the serial number, probe length and photos of the process connection. This helps verify both technical compatibility and mechanical fit.

Technical and trademark notice: Technical data is based on current Endress+Hauser product information and is subject to configuration and revision. Confirm specifications, compatibility, approvals, availability and lead time with the quotation. Product imagery is representative. We are an independent supplier; trademarks belong to their respective owners. Official product reference: Endress+Hauser Levelflex FMP51.

Related Keywords: Endress+Hauser FMP51, Levelflex FMP51, FMP51 guided wave radar, interface level measurement, guided radar level transmitter, FMP51 supplier, rod probe, rope probe, coaxial probe, high-temperature level measurement