Summary

Gammapilot FTG20 - Radiometric Measuring Technology

Application

• Non-invasive point level measurement for liquids, solids, suspensions, and sludges.
• Suitable for extreme measuring conditions: high pressure, high temperature, corrosiveness, toxicity, and abrasion.
• Used in various process vessels such as reactors, autoclaves, separators, acid tanks, mixers, cyclones, and cupola furnaces.

Benefits

• Integrated sensor and transmitter design.
• High availability, reliability, and safety in extreme process and ambient conditions.
• Adjustable sensitivity versions for optimal application matching.
• Output options: Relay, 8/16 mA (passive), or 4 to 20 mA for system integration.
• Housing options: Aluminum or stainless steel for heavy-duty applications.
• Easy commissioning and on-site operation.
• Universal use due to numerous certificates and approvals.
• Short response time.
• No recalibration required after electronics replacement.
• Self-monitoring electronics.

Technical Information

Measuring Principle

Radiometric point level detection utilizes the attenuation of gamma radiation through a material. The attenuation is governed by density, thickness, and the material's linear attenuation coefficient. A gamma radiation source and the Gammapilot FTG20 are mounted opposite each other on the vessel. The count rate at the FTG20 is maximum when the radiation path is clear and minimum when attenuated by the medium. Minimum and maximum count rates (Nmin, Nmax) are calibrated during commissioning, with switching points automatically defined.

Measuring System Components

• Gamma radiation source: Typically 137Cs or 60Co. Activity is chosen based on application requirements using the "Applicator" tool.
• Radiation source container: Directs radiation in one direction and shields other directions. Various sizes and radiation exit angles are available.
• Gammapilot FTG20: Consists of a transmitter housing and a sensor containing Geiger-Müller counters.

Geiger-Müller Counter

The sensor uses Geiger-Müller counters, which detect gamma radiation by ionizing noble gas within a cylindrical tube. Ionization creates pulses proportional to the local dose rate. These pulses are processed by the transmitter electronics to switch the output. The FTG20 can be equipped with one, two, or three Geiger-Müller counters for varying sensitivity.

Decay Compensation

A decay compensation function is available for 137Cs or 60Co sources. The device tracks runtime since calibration and warns if radioactive decay impacts switching behavior. Calibration parameters are stored on a memory module, retaining usability even if the electronics fail.

Input

Input Signal

The measured variable is the local dose rate at the Geiger-Müller counter(s). Sensitivity and maximum dose rate depend on the number of counters. All details are based on 137Cs; using 60Co results in approximately 20% higher sensitivity.

An alarm is triggered if the local dose rate is too high or too low. The required local dose rate depends on the number of counters, half-value layers (HVL), and selected switching time (0.4 s, 1.5 s, 5 s, 10 s).

• 3 HVL: 87.5% pulse rate change (e.g., ~350 mm water for 137Cs)
• 5 HVL: 97% pulse rate change (e.g., ~600 mm water for 137Cs)

Output

Output Signal

• Relay Output (FEG24): Universal current connection with relay output (DPDT). Supports voltage ranges of 19 to 253 VAC or 19 to 55 VDC. Suitable for overvoltage category II. Spark suppression is recommended for high-inductive loads.

  • Connectable Power:
    • AC: Max. 4 A, Max. 253 V, Max. 1000 VA (cos φ = 1), Max. 750 VA (cos φ = 0.7)
    • DC: Max. 4 A to 30 V, Max. 0.2 A to 125 V
  • Switching Delay: 0.4 s, 1.5 s, 5 s, 10 s
  • Signal on Alarm (Power Failure / Device Failure): Relay de-energized.

• Current Output (FEG25): Two-wire DC connection (11 to 36 VDC, 11 to 30 VDC for Ex ia). Suitable for PLCs and AI modules.

  • Switching Mode (8/16 mA): An output jump from 8 mA to 16 mA indicates a point level is reached.
    • Switching Delay: 0.4 s, 1.5 s, 5 s, 10 s
    • Error Current: ≥ 21 mA
  • Analog Mode (4 to 20 mA): Output current continuously varies from 4 mA (covered) to 20 mA (free). Conversion to a switch signal is external.
    • Integration Time: 0.4 s, 1.5 s, 5 s, 10 s
    • Error Current: ≥ 21 mA
  • Signal on Alarm (Power Failure / Device Failure): < 3.6 mA.

Sensor Failure

Failure rate data for various failure modes (Safe Detected, Safe Undetected, Dangerous Detected, Dangerous Undetected, etc.) is provided for both current and relay outputs. MTBF values are also listed.

Power Supply

• Supply Voltage:
  • FEG25 (Current Output): 11 to 36 VDC (11 to 30 VDC for Ex ia). Overvoltage category I. Reverse polarity protection: yes.
  • FEG24 (Relay Output): 19 to 55 VDC or 19 to 253 VAC (50 to 60 Hz). Overvoltage category II. Reverse polarity protection: yes.
• Power Consumption:
  • FEG25: Max. 900 mW
  • FEG24: DC max. 1.4 W; AC max. 23 VA

Installation

Mounting Location

The measuring system is mounted externally to the container. The detector (Gammapilot FTG20 sensor) is mounted precisely opposite the radiation source container.

• Maximum Point Level Detection (e.g., overfill protection): Detector and source mounted at the upper level limit.
• Minimum Point Level Detection (e.g., dry running protection): Detector and source mounted at the lower level limit.

Environment

Ambient Temperature Range

• Transmitter Housing: –40 to +70 °C (–40 to +158 °F) for both Aluminum and 316L versions.
• Sensor Housing:
  • Without water cooling: –40 to +70 °C (–40 to +158 °F) (lower limit for permanently installed cable).
  • With water cooling: 0 to +120 °C (32 to +248 °F).
  • Minimum temperature during installation: -20 °C (-4 °F).

Storage Temperature

–40 to +70 °C (–40 to +158 °F)

Climate Class

IEC EN 60068-2-38 (Test Z/AD)

Installation Height

As per IEC 61010-1 Ed.3: 2000 m (6600 ft)

Degree of Protection

• Transmitter Housing: IP66/IP67 (Aluminum F13), IP66/IP68 (316L F27) - TYPE 4/6 or TYPE 4X/6P Enclosure
• Sensor Housing: IP66/IP67 (Aluminum), IP66/IP68 (316L) - TYPE 4/6 or TYPE 4X/6P Enclosure

Shock Resistance

IEC EN 60068-2-27 (test Ea; 30 g acceleration, 18 ms, 3 shocks/direction/axis)

Vibration Resistance

IEC EN 60068-2-64 (test Fh; 10 to 2000 Hz, 1(m/s²)²/Hz)

Electromagnetic Compatibility

• Interference emission: EN 61326, Class B
• Interference immunity: EN 61326, Appendix A (industrial sector)
• NAMUR Recommendation: NE 21

Process

The measurement is non-contact. Process pressure may influence radiation source activity calculation. No other process limitations apply, and applications in the food industry are possible without additional requirements.

Process Pressure Range

The process pressure can influence the required source activity and is considered during configuration.

Process Temperature Range

Does not affect source activity. For high process temperatures, insulation or a water cooling jacket may be required.

• Mounting the Cooling Jacket:
  • Ambient Temperature (Ta): ≤ 120 °C (248 °F)
  • Maximum Pressure: 4 bar (58 psi)
  • Flow Temperature / Required Flow:
    • Max. 40 °C (104 °F) / 0.2 l/min
    • Max. 50 °C (122 °F) / 0.5 l/min

Mechanical Construction

Design, Dimensions

Dimensions are provided for Aluminum and Stainless Steel housings.

Weight

Weights for various component parts (sensors, transmitters, cables, etc.) are listed in kg and lbs.

Materials

Detailed material specifications are provided for transmitter and sensor housings, covers, seals, connectors, and other components, including material grades and standards (e.g., AlSi10Mg, 316L, EPDM, PTFE, NBR, FKM).

Operability

Display and Operating Elements

Electronic inserts (FEG24 and FEG25) are operated using a function switch and "+" / "-" keys. LEDs indicate operating status, switching position, and faults.

Operating Concept

• Manual Commissioning: Requires manual "free" and "covered" calibration. Settings for analog mode, switching delay, decay compensation, and parameter backup/restore are available.
• Commissioning Without Calibration: Automatic mode requires specific boundary conditions to be met during operation:
  • Pulse rate > 30 cps when "uncovered."
  • Pulse rate < 10 cps when "covered."
  • ≥ 5 half-value layers between "covered" and "uncovered" states.
  • Status change faster than 10 s.

Requirements for Measuring Point Configuration

Based on sensor version and radiation source (137Cs or 60Co), specific local dose rates are required for "free" and "covered" status to ensure reliable automatic operation. If these conditions are not met, manual calibration is necessary.

Certificates and Approvals

• CE Mark: Confirms conformity with applicable EC Directives.
• C-Tick Symbol: Complies with EMC requirements of the Australian Communications and Media Authority (ACMA).
• Ex Approval: Refer to safety instructions (XA) for specific details based on approval codes (e.g., ATEX, CSA/US, IECEx).
• Inspection Certificates: Available on request.
• Other Standards and Guidelines: IEC/EN 60529 (IP code), IEC/EN 61010-1, IEC/EN 61326 (EMC), NE 21 (EMC), NE 43 (Signal Level).

Ordering Information

Detailed ordering information is available via the Endress+Hauser Product Configurator on their website or through their Sales Centers.

Scope of Delivery

Includes device components (sensor, transmitter, cable), optional accessories, approval documentation (if not in Operating Instructions), and Operating Instructions.

Accessories

• Mounting Set: For wall and pipe mounting of the transmitter housing.
• Mounting Bracket: For sensor housing and cooling jacket.
• Impact Protection Tube: For conduiting between transmitter and sensor.
• Overvoltage Protection: HAW56x series for signal lines, available for control cabinet or M20x1.5 housing installation, suitable for hazardous and non-hazardous areas.

Documentation

• Standard Documentation: Operating Instructions (BA01035F/00/EN).
• Supplementary Device-Dependent Documentation: Safety Instructions (XA) are supplied based on the device's approval.

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Disclaimer: Extraction may miss figures, footnotes, or revisions; contractual data must match the OEM PDF revision used on the project.

Official datasheet (PDF)

Lenntech datasheet mirror