Critical Technical Advantages
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Optimized for Pressurized Tanks: The FMD77 is ideal for vessels where the transmitter can be bolted directly to the lower flange. The capillary on the low-pressure side then compensates for the head pressure at the top of the tank, providing an accurate level reading without the need for complex impulse piping.
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TempC Membrane Technology: Like the FMD78, this device features the TempC Membrane. This advanced technology significantly reduces measurement errors caused by varying process temperatures or ambient weather conditions, ensuring a stable zero point and high precision even during rapid temperature changes.
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Extreme Temperature Range: The diaphragm seal system allows the FMD77 to operate in processes ranging from -70°C to +400°C. By isolating the sensor electronics from these extreme temperatures, the device maintains long-term reliability and accuracy.
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High Safety Standards (SIL3): Designed for high-integrity safety loops, the FMD77 is suitable for SIL2 applications and SIL3 in redundant setups. The gas-tight feedthrough provides an essential barrier between the process and the electronics, protecting the plant and personnel.
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HistoROM Data Management: All device and process parameters are stored in the HistoROM data module. This makes “plug-and-play” maintenance possible, as settings can be automatically transferred to a replacement electronics module, drastically reducing downtime.
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Modular Serviceability: The sensor, electronics, and display are separate modules. If one component fails, it can be replaced individually without needing to buy a completely new instrument, lowering the total cost of ownership.
Technical Performance Matrix
| Feature | Details |
| Measuring Principle | Differential Pressure (Metal sensor with Diaphragm Seals) |
| System Accuracy | ±0.075% |
| Process Temperature | -70 to +400°C (-94 to +752°F) |
| Measuring Range | 100 mbar to 16 bar (1.5 to 240 psi) |
| Safety Rating | SIL2/3 (IEC 61508) / WHG Overfill Prevention |
| Communication | HART, PROFIBUS PA, FOUNDATION Fieldbus |
Primary Applications
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Pressurized Liquid Level: Measuring the level, volume, or mass of liquids in closed tanks where the transmitter is flange-mounted at the bottom.
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Distillation Columns: Reliable level monitoring in refinery or chemical columns where the process medium is at high temperatures.
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Corrosive Media: Using specialized membrane materials like Tantalum or Hastelloy to measure aggressive chemicals that would destroy standard stainless steel sensors.
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Vacuum Applications: The FMD77 is designed to handle measurements in vessels under vacuum, where traditional impulse lines would struggle with gas bubbles or fluid vaporization.
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Hygienic Level Measurement: Monitoring levels in food and pharmaceutical tanks using flush-mounted diaphragm seals that meet EHEDG or 3-A standards.
